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  • Preformulated, Shelf-Stable, Dendritic Cell-Targeting Nanogel mRNA Vaccine Delivery Platform. Bioconjugate chemistry Laturski, A. E., Durán, V., Schaar, B. T., Dulay, M. T., Einav, S., DeSimone, J. M. 2026

    Abstract

    Current mRNA-based vaccine platforms are limited by complex fabrication, stringent cold-chain dependence, and off-target in vivo delivery, restricting their global accessibility and targeting precision. Here we show a modular mRNA delivery platform; our approach integrates inverse microemulsion-derived polymeric nanogels with adsorption-based mRNA loading and the capability for ligand-directed targeting to develop targeted reductively cleavable acrylate-based inverse microemulsion nanogels (TRAINs). By decoupling nanoparticle fabrication from mRNA loading, preformed TRAINs can be stockpiled and later combined with newly designed mRNA, enabling a plug-and-play strategy for rapid adaptation to emerging pathogens, which is particularly advantageous for pandemic preparedness. This architecture supports efficient mRNA association and robust cellular uptake and translation in HEK293T cells. TRAIN also enables postsynthetic surface functionalization; as a proof of concept, CD206-targeted TRAINs promoted selective delivery to antigen-presenting cells (APCs), producing sustained and localized protein expression in BALB/c mice and preferential mRNA delivery to myeloid APCs in heterogeneous human peripheral blood mononuclear cells. Together, these results demonstrate TRAINs as a surface-customizable, adsorption-based mRNA delivery platform with potential for APC-targeted vaccination and rapid, adaptable vaccine deployment.

    View details for DOI 10.1021/acs.bioconjchem.6c00069

    View details for PubMedID 42225260

  • A 3D-Printed Scaffolded Hydrogel Microneedle Array Biosensor for Real-Time, Continuous Monitoring. Advanced materials (Deerfield Beach, Fla.) Kwak, J. W., Trinh, T., White, A. D., Chen, Y., Eckman, N., Jain, I., Xu, Y., Nguyen, N., Gopalan, D., Kim, Y. E., Unni Kamat, N., Tumbleston, J. R., Park, C. H., Yoshikawa, A., Ji, J., Dulay, M. T., Eisenstein, M., Appel, E. A., Kim, J., DeSimone, J. M., Soh, H. T. 2026: e73325

    Abstract

    Hydrogel-based biosensors offer a promising platform for designing microneedles capable of continuously tracking biomarkers in real time. However, such biosensors have been limited by the mechanical properties of hydrated hydrogels, which are generally ineffective at penetrating the skin to access interstitial fluid (ISF). As a solution, we have developed a microneedle-array biosensor (MAB) patch that enables continuous, reversible sensing by coupling fluorescent deoxyribonucleic acid (DNA) aptamer switches to a hydrated hydrogel mesh within a 3D-printed scaffold. This scaffold provides essential mechanical support for skin insertion while preserving the apatmer-hydrogel's sensing functionality in the ISF. We demonstrate this design by tuning both aptamer switch design and hydrogel mesh size to detect exogenous levels of stress hormone cortisol and the metabolite adenosine triphosphate. We subsequently incorporated our cortisol-sensing hydrogel into the MAB scaffold and coupled this system to a custom-designed portable optical detector. Following in vitro validation, we demonstrated the biocompatibility and in vivo utility of our system by conducting continuous, real-time measurements of exogenous cortisol in the ISF of live rats. These results demonstrate, for the first time, submicromolar detection using a sensor-embedded hydrogel microneedle system, highlighting the MAB platform as a versatile solution for real-time, continuous in vivo biosensing.

    View details for DOI 10.1002/adma.73325

    View details for PubMedID 42163595

  • Tunable Applicator for Microneedle-Based Medical Devices ADVANCED MATERIALS TECHNOLOGIES Ilyn, D., Hwang, J., Coates, I. A., Dobson, J., Hung, A. H., Kamat, N. U., Tumbleston, J. R., Dulay, M. T., Jacobson, G. B., DeSimone, J. M. 2026

    View details for DOI 10.1002/admt.202502525

    View details for Web of Science ID 001687405100001

  • Engineering Ultra-Soft Porous Hydrogel Scaffolds via High-Resolution 3D Printing to Enhance Cell-Based Therapy for Glioblastoma ADVANCED MATERIALS TECHNOLOGIES Garcia-Avila, J., Zhang, Y., Carlberg, L. E., Stockwell, C., Hwang, J., Dulay, M. T., Hingtgen, S. D., Perry, J. L., DeSimone, J. M. 2026

    View details for DOI 10.1002/admt.202501673

    View details for Web of Science ID 001682172400001

  • Free-Form Microfluidic Microneedle Array Patches ADVANCED FUNCTIONAL MATERIALS Coates, I. A., Driskill, M. M., Rajesh, N. U., Lipkowitz, G., Ilyn, D., Xu, Y., Dulay, M. T., Jacobson, G. B., Tumbleston, J. R., Perry, J. L., Tian, S., DeSimone, J. M. 2025

    View details for DOI 10.1002/adfm.202514879

    View details for Web of Science ID 001565190500001

  • Lyophilized SARS-CoV-2 self-amplifying RNA vaccines for microneedle Array patch delivery. Journal of controlled release : official journal of the Controlled Release Society Driskill, M. M., Coates, I. A., Hurst, P. J., Rajesh, N. U., Dulay, M. T., Waymouth, R. M., Akahata, W., Matsuda, K., Smith, J. F., Jacobson, G. B., Perry, J. L., Tian, S., DeSimone, J. M. 2025: 113944

    Abstract

    mRNA vaccines have emerged as a pivotal tool to respond to global pandemics like SARS-CoV-2. However, RNA vaccines face challenges with limited duration of immunogenicity and reliance on a special cold-chain for long term storage. Self-amplifying (saRNA) vaccines have shown sustained antigen expression and durable immune responses. Herein we developed lyophilization formulations for a SARS-CoV-2 saRNA ionizable lipid nanoparticle (LNP) to help reduce dependence on the cold chain. Our results show the induction of robust immune responses in mice by saRNA-LNPs when delivered either intramuscularly or intradermally following lyophilization and storage for up to 15 weeks at above freezing temperatures. Additionally, lyophilized saRNA-LNPs were efficiently delivered into the skin via microfluidic microarray patches (M-MAPs), inducing strong humoral and cellular immunity. M-MAPs offer a painless, self-administered alternative to traditional injections for transdermal drug delivery. Our work highlights the potential for a thermostable, self-administered RNA-LNP vaccine to improve vaccine coverage.

    View details for DOI 10.1016/j.jconrel.2025.113944

    View details for PubMedID 40499765

  • Transfection via RNA-Based Nanoparticles: Comparing Encapsulation vs Adsorption Approaches of RNA Incorporation. Bioconjugate chemistry Laturski, A. E., Dulay, M. T., Perry, J. L., DeSimone, J. M. 2025

    Abstract

    Historically, RNA delivery via nanoparticles has primarily relied on encapsulation, as demonstrated by lipid nanoparticles in SARS-CoV-2 vaccines. Concerns about RNA degradation on nanoparticle surfaces initially limited the exploration of adsorption-based approaches. However, recent advancements have renewed interest in adsorption as a viable alternative. This Viewpoint explores the approaches of RNA incorporation in nanoparticles, comparing encapsulation, adsorption, and the combination of encapsulation and adsorption, and presents a framework to guide the selection of the most suitable strategy based on general characteristics.

    View details for DOI 10.1021/acs.bioconjchem.5c00028

    View details for PubMedID 39999074

  • High-resolution stereolithography: Negative spaces enabled by control of fluid mechanics. Proceedings of the National Academy of Sciences of the United States of America Coates, I. A., Pan, W., Saccone, M. A., Lipkowitz, G., Ilyin, D., Driskill, M. M., Dulay, M. T., Frank, C. W., Shaqfeh, E. S., DeSimone, J. M. 2024; 121 (37): e2405382121

    Abstract

    Stereolithography enables the fabrication of three-dimensional (3D) freeform structures via light-induced polymerization. However, the accumulation of ultraviolet dose within resin trapped in negative spaces, such as microfluidic channels or voids, can result in the unintended closing, referred to as overcuring, of these negative spaces. We report the use of injection continuous liquid interface production to continuously displace resin at risk of overcuring in negative spaces created in previous layers with fresh resin to mitigate the loss of Z-axis resolution. We demonstrate the ability to resolve 50-μm microchannels, breaking the historical relationship between resin properties and negative space resolution. With this approach, we fabricated proof-of-concept 3D free-form microfluidic devices with improved design freedom over device material selection and resulting properties.

    View details for DOI 10.1073/pnas.2405382121

    View details for PubMedID 39231205

  • 3D-Printed Latticed Microneedle Array Patches for Tunable and Versatile Intradermal Delivery. Advanced materials (Deerfield Beach, Fla.) Rajesh, N. U., Luna Hwang, J., Xu, Y., Saccone, M. A., Hung, A. H., Hernandez, R. A., Coates, I. A., Driskill, M. M., Dulay, M. T., Jacobson, G. B., Tian, S., Perry, J. L., DeSimone, J. M. 2024: e2404606

    Abstract

    Using high-resolution 3D printing, a novel class of microneedle array patches (MAPs) is introduced, called latticed MAPs (L-MAPs). Unlike most MAPs which are composed of either solid structures or hollow needles, L-MAPs incorporate tapered struts that form hollow cells capable of trapping liquid droplets. The lattice structures can also be coated with traditional viscous coating formulations, enabling both liquid- and solid-state cargo delivery, on a single patch. Here, a library of 43 L-MAP designs is generated and in-silico modeling is used to down-select optimal geometries for further characterization. Compared to traditionally molded and solid-coated MAPs, L-MAPs can load more cargo with fewer needles per patch, enhancing cargo loading and drug delivery capabilities. Further, L-MAP cargo release kinetics into the skin can be tuned based on formulation and needle geometry. In this work, the utility of L-MAPs as a platform is demonstrated for the delivery of small molecules, mRNA lipid nanoparticles, and solid-state ovalbumin protein. In addition, the production of programmable L-MAPs is demonstrated with tunable cargo release profiles, enabled by combining needle geometries on a single patch.

    View details for DOI 10.1002/adma.202404606

    View details for PubMedID 39221508

  • Roll-to-roll, high-resolution 3D printing of shape-specific particles. Nature Kronenfeld, J. M., Rother, L., Saccone, M. A., Dulay, M. T., DeSimone, J. M. 2024; 627 (8003): 306-312

    Abstract

    Particle fabrication has attracted recent attention owing to its diverse applications in bioengineering1,2, drug and vaccine delivery3-5, microfluidics6,7, granular systems8,9, self-assembly5,10,11, microelectronics12,13 and abrasives14. Herein we introduce a scalable, high-resolution, 3D printing technique for the fabrication of shape-specific particles based on roll-to-roll continuous liquid interface production (r2rCLIP). We demonstrate r2rCLIP using single-digit, micron-resolution optics in combination with a continuous roll of film (in lieu of a static platform), enabling the rapidly permutable fabrication and harvesting of shape-specific particles from a variety of materials and withcomplex geometries, including geometries not possible to achieve with advanced mould-based techniques. We demonstrate r2rCLIP production of mouldable and non-mouldable shapes with voxel sizes as small as 2.0*2.0m2 in the print plane and 1.1±0.3m unsupported thickness, at speeds of up to 1,000,000particles per day. Such microscopic particles with permutable, intricate designs enable direct integration within biomedical, analytical and advanced materials applications.

    View details for DOI 10.1038/s41586-024-07061-4

    View details for PubMedID 38480965

  • 3D-Printed Microarray Patches for Transdermal Applications. JACS Au Rajesh, N. U., Coates, I., Driskill, M. M., Dulay, M. T., Hsiao, K., Ilyin, D., Jacobson, G. B., Kwak, J. W., Lawrence, M., Perry, J., Shea, C. O., Tian, S., DeSimone, J. M. 2022; 2 (11): 2426-2445

    Abstract

    The intradermal (ID) space has been actively explored as a means for drug delivery and diagnostics that is minimally invasive. Microneedles or microneedle patches or microarray patches (MAPs) are comprised of a series of micrometer-sized projections that can painlessly puncture the skin and access the epidermal/dermal layer. MAPs have failed to reach their full potential because many of these platforms rely on dated lithographic manufacturing processes or molding processes that are not easily scalable and hinder innovative designs of MAP geometries that can be achieved. The DeSimone Laboratory has recently developed a high-resolution continuous liquid interface production (CLIP) 3D printing technology. This 3D printer uses light and oxygen to enable a continuous, noncontact polymerization dead zone at the build surface, allowing for rapid production of MAPs with precise and tunable geometries. Using this tool, we are now able to produce new classes of lattice MAPs (L-MAPs) and dynamic MAPs (D-MAPs) that can deliver both solid state and liquid cargos and are also capable of sampling interstitial fluid. Herein, we will explore how additive manufacturing can revolutionize MAP development and open new doors for minimally invasive drug delivery and diagnostic platforms.

    View details for DOI 10.1021/jacsau.2c00432

    View details for PubMedID 36465529

    View details for PubMedCentralID PMC9709783

  • Single-digit-micrometer-resolution continuous liquid interface production. Science advances Hsiao, K., Lee, B. J., Samuelsen, T., Lipkowitz, G., Kronenfeld, J. M., Ilyn, D., Shih, A., Dulay, M. T., Tate, L., Shaqfeh, E. S., DeSimone, J. M. 2022; 8 (46): eabq2846

    Abstract

    To date, a compromise between resolution and print speed has rendered most high-resolution additive manufacturing technologies unscalable with limited applications. By combining a reduction lens optics system for single-digit-micrometer resolution, an in-line camera system for contrast-based sharpness optimization, and continuous liquid interface production (CLIP) technology for high scalability, we introduce a single-digit-micrometer-resolution CLIP-based 3D printer that can create millimeter-scale 3D prints with single-digit-micrometer-resolution features in just a few minutes. A simulation model is developed in parallel to probe the fundamental governing principles in optics, chemical kinetics, and mass transport in the 3D printing process. A print strategy with tunable parameters informed by the simulation model is adopted to achieve both the optimal resolution and the maximum print speed. Together, the high-resolution 3D CLIP printer has opened the door to various applications including, but not limited to, biomedical, MEMS, and microelectronics.

    View details for DOI 10.1126/sciadv.abq2846

    View details for PubMedID 36383664

  • 3D-Printed Microarray Patches for Transdermal Applications JACS AU Rajesh, N. U., Coates, I., Driskill, M. M., Dulay, M. T., Hsiao, K., Ilyin, D., Jacobson, G. B., Kwak, J., Lawrence, M., Perry, J., Shea, C. O., Tian, S., DeSimone, J. M. 2022

    View details for DOI 10.1021/jacsau.2c00432

    View details for Web of Science ID 000874579200001

  • Injection continuous liquid interface production of 3D objects. Science advances Lipkowitz, G., Samuelsen, T., Hsiao, K., Lee, B., Dulay, M. T., Coates, I., Lin, H., Pan, W., Toth, G., Tate, L., Shaqfeh, E. S., DeSimone, J. M. 2022; 8 (39): eabq3917

    Abstract

    In additive manufacturing, it is imperative to increase print speeds, use higher-viscosity resins, and print with multiple different resins simultaneously. To this end, we introduce a previously unexplored ultraviolet-based photopolymerization three-dimensional printing process. The method exploits a continuous liquid interface-the dead zone-mechanically fed with resin at elevated pressures through microfluidic channels dynamically created and integral to the growing part. Through this mass transport control, injection continuous liquid interface production, or iCLIP, can accelerate printing speeds to 5- to 10-fold over current methods such as CLIP, can use resins an order of magnitude more viscous than CLIP, and can readily pattern a single heterogeneous object with different resins in all Cartesian coordinates. We characterize the process parameters governing iCLIP and demonstrate use cases for rapidly printing carbon nanotube-filled composites, multimaterial features with length scales spanning several orders of magnitude, and lattices with tunable moduli and energy absorption.

    View details for DOI 10.1126/sciadv.abq3917

    View details for PubMedID 36170357

  • An Outreach/Learning Activity for STEAM Education via the Design and 3D Printing of an Accessible Periodic Table JOURNAL OF CHEMICAL EDUCATION Zhang, T., Cummings, M., Dulay, M. T. 2022

    View details for DOI 10.1021/acs.jchemed.2c00186

    View details for Web of Science ID 000855190900001

  • Optimizing Coaxial Sonic Spray Geometry for Generating Water Microdroplets. Analytical chemistry Dulay, M. T., Chamberlayne, C. F., Zare, R. N. 2022

    Abstract

    Sonic spray creates a stream of neutral and charged microdroplets without application of voltage, heating, laser irradiation, or corona discharge. The solvent of interest flows through an inner capillary (usually constructed of fused silica) that is surrounded by an outer stainless-steel tube through which a nebulizing gas flows under pressure. This technique has been widely used as the interface in mass spectrometric studies for chemical analysis and for understanding microdroplet chemistry. We have used light scattering to characterize the size distribution and density for water microdroplets as a function of several parameters, such as water quality, water flow rate, nebulizing gas pressure, and sonic sprayer geometry. We find that the size distribution of the microdroplets, which is critical to many applications, depends most sensitively on the distance between the inner and outer capillary outlets and the gas flow pressure. The best performance as measured by the smallness of the microdroplet diameters is obtained when the gas flow pressure is the highest and there is no separation distance, d, between the two capillary outlets. In addition, at d = 0 mm, the microdroplet diameter distribution is nearly independent of the water flow rate, indicating that studies under these conditions can be scaled up.

    View details for DOI 10.1021/acs.analchem.1c05337

    View details for PubMedID 35191692

  • Effect of relative humidity on hydrogen peroxide production in water droplets. QRB discovery Dulay, M. T., Huerta-Aguilar, C. A., Chamberlayne, C. F., Zare, R. N., Davidse, A., Vukovic, S. 2021; 2: e8

    Abstract

    Mist is generated by ultrasonic cavitation of water (Fisher Biograde, pH 5.5-6.5) at room temperature (20-25 °C) in open air with nearly constant temperature (22-25 °C) but varying relative humidity (RH; 24-52%) over the course of many months. Water droplets in the mist are initially about 7 μm in diameter at about 50% RH. They are collected, and the concentration of hydrogen peroxide (H2O2) is measured using commercial peroxide test strips and by bromothymol blue oxidation. The quantification method is based on the Fenton chemistry of dye degradation to determine the oxidation capacity of water samples that have been treated by ultrasonication. It is found that the hydrogen peroxide concentration varies nearly linearly with RH over the range studied, reaching a low of 2 parts per million (ppm) at 24% RH and a high of 6 ppm at 52% RH. Some possible public health implications concerning the transmission of respiratory viral infections are suggested for this threefold change in H2O2 concentration with RH.

    View details for DOI 10.1017/qrd.2021.6

    View details for PubMedID 37529674

    View details for PubMedCentralID PMC10392617

  • Spraying Small Water Droplets Acts as a Bacteriocide. QRB discovery Dulay, M. T., Lee, J. K., Mody, A. C., Narasimhan, R., Monack, D. M., Zare, R. N. 2020; 1: e3

    Abstract

    Disinfectants are important for arresting the spread of pathogens in the environment. Frequently used disinfectants are often incompatible with certain surfaces, expensive and can produce hazardous by-products. We report that micron-sized water droplets can act as an effective disinfectant, which were formed by spraying pure bulk water with coaxial nebulizing airflow. Spraying for 20 min onto Escherichia coli and Salmonella typhimurium on stainless-steel discs caused inactivation of over 98% of the bacteria. Control experiments resulted in less than 10% inactivation (water stream only and gas only) and 55% inactivation with 3% hydrogen peroxide. Experiments have shown that cell death results from cell wall destruction. We suggest that the combined action of reactive oxygen species present in water droplets (but not in bulk water) along with the droplet surface charge is responsible for the observed bactericidal activity.

    View details for DOI 10.1017/qrd.2020.2

    View details for PubMedID 37528962

    View details for PubMedCentralID PMC10392691

  • Detecting bacteria using an artificial antibody Dulay, M., Mody, A., Zare, R., Da-Silva-Granja, C. AMER CHEMICAL SOC. 2019

    View details for Web of Science ID 000525055501173

  • Selective and sensitive detection of pathogens with pathogen-imprinted polymers Dulay, M. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000435537700459

  • Taking back my power: My story of sexual harassment Dulay, M. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000435539907688

  • Polymer-spray mass spectrometry for rapid analysis of drugs in biofluids Dulay, M. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000435537700460

  • Pathogen-Imprinted Organosiloxane Polymers as Selective Biosensors for the Detection of Targeted E. coli. C Dulay, M. T., Zaman, N. n., Jaramillo, D. n., Mody, A. C., Zare, R. N. 2018; 4 (2): 29

    Abstract

    Early detection of pathogens requires methods that are fast, selective, sensitive and affordable. We report the development of a biosensor with high sensitivity and selectivity based on the low-cost preparation of organosiloxane (OSX) polymers imprinted with E. coli-GFP (green fluorescent protein). OSX polymers with high optical transparency, no cracking, and no shrinkage were prepared by varying several parameters of the sol-gel reaction. The unique shape and chemical fingerprint of the targeted inactivated E. coli-GFP were imprinted into bulk polymers by replication imprinting where the polymer solution was dropcast onto a bacteria template that produced a replica of the bacterial shape and chemistry on the polymer surface upon removal of the template. Capture performances were studied under non-laminar flow conditions with samples containing inactivated E. coli-GFP and compared to inactivated S. typhimurium-GFP. Capture selectivity ratios are dependent on the type of alkoxysilanes used, the H2O:silane molar ratio, and the polymerization temperature. The bacteria concentration in suspension ranged from ~6 × 105 to 1.6 × 109 cells/mL. E. coli-imprinted OSX polymers with polyethylene glycol (PEG) differentiated between the targeted bacterium E. coli, and non-targeted bacteria S. typhimurium and native E. coli-GFP, achieving selectivity ratios up to 4.5 times higher than polydimethylsiloxane (PDMS) and OSX polymers without PEG.

    View details for DOI 10.3390/c4020029

    View details for PubMedID 33381537

    View details for PubMedCentralID PMC7743956

  • Polymer-spray mass spectrometric detection and quantitation of hydrophilic compounds and some narcotics. Rapid communications in mass spectrometry : RCM Dulay, M. T., Zare, R. N. 2017; 31 (19): 1651–58

    Abstract

    High-throughput screening of biofluids is essential in monitoring concentration of a variety of drugs to determine their efficacy and toxicity. Organosiloxane polymers prepared by sol-gel chemistry as sample supports, and electrospray ionization emitters in a single material and as an alternative to paper substrates, is described in this study.Hydrophobic drugs and hydrophilic streptomycin were analyzed by polymer-spray mass spectrometry with an LTQ-Orbitrap mass spectrometer. Drug samples in urine (1-2 μL) were deposited on an OSX polymer, allowed to dry, then electrosprayed from the polymer tip into the mass spectrometer without sample pretreatment. The OSX polymers, whose polarity and porosity can be controlled, were prepared by sol-gel chemistry where methyl-substituted alkoxysilanes were hydrolyzed in the presence of a pore template and an acid catalyst.Five nanograms each of seven narcotic drugs were detected in <1 min (relative standard deviation (RSD) of response <1% for each drug). Calibration curves of cocaine and streptomycin in urine were used to establish the performance of the polymer. For sample 1 (n = 2), the mean recovery for cocaine was 81% with paper and 90% with polymer. Streptomycin is detected with polymer, not with paper; for samples 1 and 2 (n = 3), mean recovery was 97% and 95%, respectively.Organosiloxane polymers achieve more sensitive analysis than paper, allowing for more accurate quantitation of both hydrophobic and hydrophilic drug compounds. The ability to tailor the polymer polarity and porosity allows for the synthesis of a wide range of polymers, and thus opens many possibilities for further development and applications.

    View details for PubMedID 28792093

  • Monitoring Enzymatic Reactions in Real Time Using Venturi Easy Ambient Sonic-Spray Ionization Mass Spectrometry ANALYTICAL CHEMISTRY Jansson, E. T., Dulay, M. T., Zare, R. N. 2016; 88 (12): 6195-6198

    Abstract

    We developed a technique to monitor spatially confined surface reactions with mass spectrometry under ambient conditions, without the need for voltage or organic solvents. Fused-silica capillaries immersed in an aqueous solution, positioned in close proximity to each other and the functionalized surface, created a laminar flow junction with a resulting reaction volume of ∼5 pL. The setup was operated with a syringe pump, delivering reagents to the surface through a fused-silica capillary. The other fused-silica capillary was connected to a Venturi easy ambient sonic-spray ionization source, sampling the resulting analytes at a slightly higher flow rate compared to the feeding capillary. The combined effects of the inflow and outflow maintains a chemical microenvironment, where the rate of advective transport overcomes diffusion. We show proof-of-concept where acetylcholinesterase was immobilized on an organosiloxane polymer through electrostatic interactions. The hydrolysis of acetylcholine by acetylcholinesterase into choline was monitored in real-time for a range of acetylcholine concentrations, fused-silica capillary geometries, and operating flow rates. Higher reaction rates and conversion yields were observed with increasing acetylcholine concentrations, as would be expected.

    View details for DOI 10.1021/acs.analchem.6b01246

    View details for Web of Science ID 000378470200019

    View details for PubMedID 27249533

    View details for PubMedCentralID PMC4917919

  • Protein Analysis by Ambient Ionization Mass Spectrometry Using Trypsin-Immobilized Organosiloxane Polymer Surfaces ANALYTICAL CHEMISTRY Dulay, M. T., Eberlin, L. S., Zare, R. N. 2015; 87 (24): 12324-12330

    Abstract

    In the growing field of proteomic research, rapid and simple protein analysis is a crucial component of protein identification. We report the use of immobilized trypsin on hybrid organic-inorganic organosiloxane (T-OSX) polymers for the on-surface, in situ digestion of four model proteins: melittin, cytochrome c, myoglobin, and bovine serum albumin. Tryptic digestion products were sampled, detected, and identified using desorption electrospray ionization mass spectrometry (DESI-MS) and nanoDESI-MS. These novel, reusable T-OSX arrays on glass slides allow for protein digestion in methanol:water solvents (1:1, v/v) and analysis directly from the same polymer surface without the need for sample preparation, high temperature, and pH conditions typically required for in-solution trypsin digestions. Digestion reactions were conducted with 2 μL protein sample droplets (0.35 mM) at incubation temperatures of 4, 25, 37, and 65 °C and digestion reaction times between 2 and 24 h. Sequence coverages were dependent on the hydrophobicity of the OSX polymer support and varied by temperature and digestion time. Under the best conditions, the sequence coverages, determined by DESI-MS, were 100% for melittin, 100% for cytochrome c, 90% for myoglobin, and 65% for bovine serum albumin.

    View details for DOI 10.1021/acs.analchem.5b03669

    View details for PubMedID 26567450

  • Droplet Spray Ionization from a Glass Microscope Slide: Real-Time Monitoring of Ethylene Polymerization ANALYTICAL CHEMISTRY Jiang, J., Zhang, H., Li, M., Dulay, M. T., Ingram, A. J., Li, N., You, H., Zare, R. N. 2015; 87 (16): 8057-8062

    Abstract

    Ambient ionization mass spectrometry is achieved in a simple manner by loading a sample solution onto a corner of a microscope cover glass positioned in front of the inlet to a mass spectrometer and applying a high voltage to the sample. The resulting stream of charged droplets is stable, has no contamination from the substrate platform, and can be used repeatedly. The utility of droplet spray for in situ analysis and real-time monitoring of chemical reactions was demonstrated by the bis(cyclopentadienyl)zirconium dichloride (zirconocene dichloride)/methylaluminoxane, Cp2ZrCl2/MAO, homogeneously catalyzed polymerization of ethylene in various solutions. Reaction times ranged from seconds to minutes, and catalytically active species and polymeric products of ethylene were acquired and identified by tandem mass spectrometry.

    View details for DOI 10.1021/acs.analchem.5b02390

    View details for Web of Science ID 000359892100005

  • Droplet spray ionization from a glass microscope slide: real-time monitoring of ethylene polymerization. Analytical chemistry Jiang, J., Zhang, H., Li, M., Dulay, M. T., Ingram, A. J., Li, N., You, H., Zare, R. N. 2015; 87 (16): 8057-62

    Abstract

    Ambient ionization mass spectrometry is achieved in a simple manner by loading a sample solution onto a corner of a microscope cover glass positioned in front of the inlet to a mass spectrometer and applying a high voltage to the sample. The resulting stream of charged droplets is stable, has no contamination from the substrate platform, and can be used repeatedly. The utility of droplet spray for in situ analysis and real-time monitoring of chemical reactions was demonstrated by the bis(cyclopentadienyl)zirconium dichloride (zirconocene dichloride)/methylaluminoxane, Cp2ZrCl2/MAO, homogeneously catalyzed polymerization of ethylene in various solutions. Reaction times ranged from seconds to minutes, and catalytically active species and polymeric products of ethylene were acquired and identified by tandem mass spectrometry.

    View details for DOI 10.1021/acs.analchem.5b02390

    View details for PubMedID 26204485

  • Visible light-induced photopolymerization of an in situ macroporous sol-gel monolith JOURNAL OF SEPARATION SCIENCE Dulay, M. T., Choi, H. N., Zare, R. N. 2007; 30 (17): 2979-2985

    Abstract

    A one-step, in situ, photopolymerization of a mixture of methacryloxypropyltrimethoxysilane in the presence of an acid catalyst, water, and toluene is accomplished in a 75 microm id polyimide-coated capillary using visible light (460 nm) for a 15 min irradiation time. The mixture is a two-component photosystem comprising Irgacure 784 photosensitizer and diphenyliodonium chloride photoinitiator. The visible photopolymerized sol-gel (vis-PSG) column shows RP chromatographic behavior. The analytical potential of these columns is demonstrated with the isocratic separation of small, neutral alkyl phenyl ketones. Operational parameters, such as mobile phase composition, field strength, and column temperature were varied to assess how they affect the separation performance of the monolith.

    View details for DOI 10.1002/jssc.200700328

    View details for Web of Science ID 000251461500024

    View details for PubMedID 17960846

  • On-line biological sample cleanup for electrospray mass spectrometry using sol-gel columns JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES Johannesson, N., Pearce, E., Dulay, M., Zare, R. N., Bergquist, J., Markides, K. E. 2006; 842 (1): 70-74

    Abstract

    Using a slight overpressure, a urine sample is loaded onto a monolithic photopolymerized sol-gel column that has been derivatized with hydrophobic carbon chains and then the complex urine matrix is washed with aqueous solution. A buffer containing organic solvent is used to elute the adsorbed peptides by an applied voltage and the sample is then introduced into a mass spectrometer by sheath flow electrospray. The importance of desalting this type of sample is demonstrated by an experiment that shows that the signal intensity of a test solution with neurotensin, sprayed directly into the mass spectrometer, decreased from 4.5x10(4) cps to no detectible signal when just 10% urine is added to the sample solution. We suggest that this procedure may find general application for desalting biological samples prior to mass spectrometric analysis.

    View details for DOI 10.1016/j.jchromb.2006.05.012

    View details for Web of Science ID 000240712700011

    View details for PubMedID 16814621

  • Enhanced proteolytic activity of covalently bound enzymes in photopolymerized sol gel. Analytical chemistry Dulay, M. T., Baca, Q. J., Zare, R. N. 2005; 77 (14): 4604-4610

    Abstract

    Trypsin is covalently linked to a photopolymerized sol-gel monolith modified by incorporating poly(ethylene glycol) (PSG-PEG) for on-column digestion of N(alpha)-benzoyl-l-arginine ethyl ester (BAEE) and two peptides, neurotensin and insulin chain B. The coupling of the enzyme to the monolith is via room-temperature Schiff chemistry in which an alkoxysilane reagent (linker) with an aldehyde functional group links to an inactive amine on trypsin to form an imine bond. The proteolytic activity of the immobilized trypsin was measured by monitoring the formation of N alpha-benzoyl-L-arginine (BA), the digestion product of BAEE. The BA is separated from BAEE by capillary electrophoresis and detected downstream (18.5 cm from the microreactor) by absorption (254 nm). Using the Bradford assay, we determined that 97 ng of trypsin is bound to the 1-cm microreactor located at the entrance of capillary column. The bioactivity of the trypsin-PSG-PEG microreactor at 20 degrees C for the digestion of BAEE was found to be 2270 units/mg of immobilized trypsin. The bioactivity of trypsin bound to the capillary wall in the open segment upstream from the monolith was 332 units/mg of immobilized trypsin under the same conditions. In contrast, the activity of free trypsin could not be observed for the digestion of BAEE at 20 degrees C after 16 h of incubation time.

    View details for PubMedID 16013879

  • Enhanced proteolytic activity enzymes in photopolymerized of covalently bound sol gel ANALYTICAL CHEMISTRY Dulay, M. T., Baca, Q. J., Zare, R. N. 2005; 77 (14): 4604-4610

    Abstract

    Trypsin is covalently linked to a photopolymerized sol-gel monolith modified by incorporating poly(ethylene glycol) (PSG-PEG) for on-column digestion of N(alpha)-benzoyl-l-arginine ethyl ester (BAEE) and two peptides, neurotensin and insulin chain B. The coupling of the enzyme to the monolith is via room-temperature Schiff chemistry in which an alkoxysilane reagent (linker) with an aldehyde functional group links to an inactive amine on trypsin to form an imine bond. The proteolytic activity of the immobilized trypsin was measured by monitoring the formation of N alpha-benzoyl-L-arginine (BA), the digestion product of BAEE. The BA is separated from BAEE by capillary electrophoresis and detected downstream (18.5 cm from the microreactor) by absorption (254 nm). Using the Bradford assay, we determined that 97 ng of trypsin is bound to the 1-cm microreactor located at the entrance of capillary column. The bioactivity of the trypsin-PSG-PEG microreactor at 20 degrees C for the digestion of BAEE was found to be 2270 units/mg of immobilized trypsin. The bioactivity of trypsin bound to the capillary wall in the open segment upstream from the monolith was 332 units/mg of immobilized trypsin under the same conditions. In contrast, the activity of free trypsin could not be observed for the digestion of BAEE at 20 degrees C after 16 h of incubation time.

    View details for DOI 10.1021/ac0504767

    View details for Web of Science ID 000230530300042

  • Capillary electrophoretic and micellar electrokinetic separations of asymmetric dimethyl-L-arginine and structurally related amino acids: Quantitation in human plasma JOURNAL OF SEPARATION SCIENCE Trapp, G., Sydow, K., Dulay, M. T., Chou, T., Cooke, J. P., Zare, R. N. 2004; 27 (17-18): 1483-1490

    Abstract

    We report the development of efficient electrophoretic methods for the separation and quantification of L-arginine and six naturally occurring derivatives that are structurally and functionally related. Capillary electrophoresis (CE) employing a concentrated borate buffer at pH 9.4 achieves the separation of mixtures containing dimethyl-L-arginine, NG-monomethyl-L-arginine, L-arginine, L-homoarginine, L-ornithine, and L-citrulline as 4-fluoro-7-nitrobenzofurazan derivatives. In addition, the separation of the isomeric dimethyl-L-arginine derivatives (symmetric and asymmetric) is attained with baseline resolution by micellar electrokinetic chromatography (MEKC) when a high concentration of deoxycholic acid is added as a surfactant to the same running buffer. The influence of buffer type, concentration, and pH on the separation was studied to optimize separation conditions. The limit of quantitation (LOQ) for asymmetric dimethyl-L-arginine in aqueous solution was determined to be 20 microM using UV absorption in a CE separation and 0.1 microM using laser induced fluorescence (LIF) detection in an MEKC separation. This newly developed method was successfully applied for the quantitation of asymmetric dimethyl-L-arginine and L-arginine in human plasma samples at levels that might be used as a clinical diagnostic for cardiovascular disease (0.125 microM LOQ).

    View details for DOI 10.1002/jssc.200401918

    View details for Web of Science ID 000225938100011

    View details for PubMedID 15638156

  • Integration of on-line protein digestion, peptide separation, and protein identification using pepsin-coated photopolymerized sol-gel columns and capillary electrophoresis/mass spectrometry ANALYTICAL CHEMISTRY Kato, M., Sakai-Kato, K., Jin, H. M., Kubota, K., Miyano, H., Toyo'oka, T., Dulay, M. T., Zare, R. N. 2004; 76 (7): 1896-1902

    Abstract

    A miniaturized pepsin reactor was prepared inside a fused-silica capillary (i.d. 75 microm) by coating a pepsin-containing gel on a photopolymerized porous silica monolith. The pepsin-encapsulated film was prepared by a sol-gel method. The sol-gel reaction was optimized so that the sol solution containing pepsin forms a thin film on the photopolymerized sol-gel (PSG) monolith that was initially fabricated at the inlet of the capillary. Pepsin was encapsulated into the gel matrix without losing its activity. The large surface area of the PSG monolith enabled the immobilized pepsin to achieve a high catalytic turnover rate, and the porous nature of the PSG promotes penetration of large molecular proteins into the column. The immobilized pepsin-digested peptides and proteins, and the resulting mixture of peptide fragments, could be directly separated in the portion of the capillary where no PSG monolith exists. The durability and repeatability of the fabricated pepsin-coated column was tested and found to be satisfactory. An acidic solution consisting of 0.5 M formic acid was used as the running buffer, because it suppresses the adsorption of proteins or peptides on the inner surface of the capillary as well as enables direct connection of the output of the capillary electrophoresis column to a mass spectrometer. The on-line digestion of insulin chain beta and lysozyme provides identification of the proteolytic peptides. Recovery was achieved for 100% of the insulin chain beta amino acid sequence and 73% of the lysozyme amino acid sequence.

    View details for DOI 10.1021/ac035107u

    View details for Web of Science ID 000220618400022

    View details for PubMedID 15053649

  • Determination of glutamine and serine in rat cerebrospinal fluid using capillary electrochromatography with a modified photopolymerized sol-gel monolithic column JOURNAL OF CHROMATOGRAPHY A Kato, M., Jin, H. M., Sakai-Kato, K., Toyo'oka, T., Dulay, M. T., Zare, R. N. 2003; 1004 (1-2): 209-215

    Abstract

    Capillary electrochromatographic separations of amino acid mixtures were studied using two modified porous photopolymerized sol-gel monolithic columns. One was modified with dimethyloctadecylchlorosilane (DMOS), and the other was modified with DMOS, followed by chlorotrimethylsilane to end-cap residual silanol groups. Prior to separation, amino acids were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole using as a mobile phase 50 mM phosphate (pH 2.5), water, and acetonitrile in the ratio of 1:1:8. Five derivatized amino acids (Asn, Phe, Ala, Ile, and Leu) were separated within 7 min. Theoretical plate numbers varied between 58700 and 105000/m. This separation method with the end-capped monolithic column was applied to rat cerebrospinal fluid. The dominant amino acid found was Gln at a concentration of 420 microM along with small quantities of Ser (54 microM).

    View details for DOI 10.1016/S0021-9673(03)00451-5

    View details for Web of Science ID 000184296600023

    View details for PubMedID 12929975

  • Toward sol-gel electrochromatographic separations on a chip JOURNAL OF SEPARATION SCIENCE Morishima, K., Bennett, B. D., Dulay, M. T., Quirino, J. P., Zare, R. N. 2002; 25 (15-17): 1226-1230

    View details for Web of Science ID 000179959200035

  • Capillary electrophoresis separation and native laser-induced fluorescence detection of metallotexaphrins JOURNAL OF SEPARATION SCIENCE Quirino, J. P., Dulay, M. T., Fu, L., Mody, T. D., Zare, R. N. 2002; 25 (13): 819-824

    View details for Web of Science ID 000178547800004

  • Effect of preparatory conditions on the performance of photopolymerized sol-gel monoliths for capillary electrochromatography International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC Kyoto) Kato, M., Sakai-Kato, K., Toyo'oka, T., Dulay, M. T., Quirino, J. P., Bennett, B. D., Zare, R. N. ELSEVIER SCIENCE BV. 2002: 45–51

    Abstract

    We prepared different photopolymerized sol-gel (PSG) columns by varying the amount of monomer (methacryloxypropyltrimethoxysilane), porogen (toluene) and catalyst (hydrochloric acid) in the reaction solution containing a photoinitiator (Irgacure 1800). The effects of these variations on the chromatographic behavior of the PSG columns were studied. All of the columns studied exhibited reversed-phase character. The concentration of hydrochloric acid was important for the rigidity of the columns, although it did not affect the separation property. The ratio of monomer solution to porogen was a critical factor in controlling the through-pore size and the surface area of PSG, which were found to significantly affect the separation properties, such as permeability, theoretical plate number, retention time, and separation efficiency, of a mixture of test analytes-thiourea, benzene, and naphthalene. There was no change in the retention order for the test analytes. Short separation times were achieved on PSG columns made from a 10% monomer stock solution and 90% porogen with 1 M hydrochloric acid. Mixtures of polycyclic aromatic hydrocarbons and alkylbenzenes were separated with theoretical plate numbers greater than 100 000 plates/m.

    View details for Web of Science ID 000177061200006

    View details for PubMedID 12186390

  • Genetic screening using the colour change of a PNA-DNA hybrid-binding cyanine dye NUCLEIC ACIDS RESEARCH Wilhelmsson, L. M., Norden, B., Mukherjee, K., Dulay, M. T., Zare, R. N. 2002; 30 (2)

    Abstract

    As the relationship between human genes and various malfunctions and diseases becomes revealed at an ever-increasing pace, the need arises for the development of rapid genetic screening methods for diagnostic purposes. Genetic diseases show great diversity. Some are caused by a few characteristic localised mutations, while others arise from a large number of variations. Hence, it is unlikely that a single, general diagnostic method that applies to all cases will ever exist. Instead, a combination of methods is frequently applied. Here we propose the use of a dramatic colour change that a cyanine dye, 3,3'-diethylthiadicarbocyanine, displays upon binding to DNA-PNA duplexes. This method could become an inexpensive, fast and simple genetic screening test by visual inspection, with no need for complicated equipment. Our results demonstrate that this diagnostic method may be sufficiently sensitive to discriminate between even a fully complementary and a single mutation DNA sequence.

    View details for Web of Science ID 000173551200027

    View details for PubMedID 11788729

    View details for PubMedCentralID PMC99842

  • Bonded-phase photopolymerized sol-gel monoliths for reversed phase capillary electrochromatography JOURNAL OF SEPARATION SCIENCE Dulay, M. T., Quirino, J. P., Bennett, B. D., Zare, R. N. 2002; 25 (1-2): 3-9

    View details for Web of Science ID 000173610600002

  • Strategy for on-line preconcentration in chromatographic separations ANALYTICAL CHEMISTRY Quirino, J. P., Dulay, M. T., Bennett, B. D., Zare, R. N. 2001; 73 (22): 5539-5543

    Abstract

    In chromatographic separations, the heights of peaks are proportional to the concentrations of sample components present in an injected mixture. In general, an increase in the peak height cannot be achieved by simply increasing the injection time or the sample plug length. An exception occurs if some form of on-line preconcentration is possible. We present a new strategy for achieving on-line preconcentration by the use of a porous chromatographic material that acts as a solid-phase extractor as well as a stationary-phase separator. We are able to realize significant on-line preconcentration using capillary columns filled with a photopolymerized sol-gel (PSG). More than 2-cm plugs of sample solution can be loaded into the capillary and concentrated using a running buffer that is the same as the injection buffer (to avoid solvent gradient effects). As a demonstration, mixtures of three different polycyclic aromatic hydrocarbons, eight different alkyl phenyl ketones, and five different peptides in solutions of aqueous acetonitrile have been injected onto the PSG column and separated by capillary electrochromatography. The preconcentration is marked in terms of peak heights, with up to 100-fold increase for the PAH mixture, 30-fold for the alkyl phenyl ketone mixture, and 20-fold for the peptide mixture. Preconcentration takes place because of the high mass-transfer rates possible in the highly porous structure, and the extent of preconcentration follows the retention factor k for a given analyte.

    View details for DOI 10.1021/ac015522r

    View details for Web of Science ID 000172209400027

    View details for PubMedID 11816585

  • On-line preconcentration in capillary electrochromatography using a porous monolith together with solvent gradient and sample stacking ANALYTICAL CHEMISTRY Quirino, J. P., Dulay, M. T., Zare, R. N. 2001; 73 (22): 5557-5563

    Abstract

    Preconcentration effects of solvent gradient and sample stacking are investigated on a photopolymerized sol-gel (PSG) in capillary electrochromatography. The porous PSG monolith has a high mass-transfer rate. This characteristic promotes preconcentration of dilute samples. Plugs of samples more than 2 cm in length prepared in the separation solution (nongradient condition) are injected onto the PSG column. The extent of preconcentration is quite significant, showing up to a 100-fold increase in peak heights of the separated analytes. Even larger preconcentrations are achieved under gradient conditions by dissolving the sample in a matrix with a higher concentration of noneluting solvent (water). For eight alkyl phenyl ketones and four polycyclic aromatic hydrocarbons that serve as neutral test analytes, improvements in peak heights obtained under gradient conditions can be more than a 1000-fold. Indeed, injection of a 91.2-cm plug, which is more than 3 times the total length of the capillary, was possible with only a minor loss in resolution. Five peptides serve as charged test analytes. Nongradient conditions in which the sample is hydrodynamically injected onto the PSG column show sizable preconcentration because of sample stacking. The use of a solvent gradient with the same ionic strength, however, does not appear to have practical value because of destacking caused by the changing organic composition that affects the conductivity. As an alternative preconcentration method, we demonstrate that electric field-enhanced sample injection on the PSG yielded up to a 1000-fold improvement in detection sensitivity for the test peptides.

    View details for Web of Science ID 000172209400030

    View details for PubMedID 11816588

  • Photopolymerized sol-gel monoliths for capillary electrochromatography ANALYTICAL CHEMISTRY Dulay, M. T., Quirino, J. P., Bennett, B. D., Kato, M., Zare, R. N. 2001; 73 (16): 3921-3926

    Abstract

    A solution of methacryloxypropyltrimethoxysilane in the presence of an acid catalyst, water, toluene, and a photoinitiator was irradiated at 365 nm for 5 min in a 75-microm i.d. capillary to prepare a porous monolithic sol-gel column by a one-step, in situ, process. The photopolymerized sol-gel (PSG) column shows reversed-phase behavior. Using this column, a variety of low-molecular-weight neutral compounds, including polycyclic aromatic hydrocarbons, alkyl benzenes, alkyl phenyl ketones, and steroids are separated from mixtures. Various different operational parameters, such as buffer composition, field strength, and column temperature, were varied to assess their influence on column performance. Use of PSG as a stationary phase for a pressure-driven separation is also demonstrated.

    View details for DOI 10.1006/ac0100749

    View details for Web of Science ID 000170482800019

    View details for PubMedID 11534717

  • Photopolymerized sol-gel frits for packed columns in capillary electrochromatography 14th International Symposium on Microscale Separations and Analysis Kato, M., Dulay, M. T., Bennett, B. D., Quirino, J. P., Zare, R. N. ELSEVIER SCIENCE BV. 2001: 187–95

    Abstract

    Porous sol-gel frits are fabricated in a capillary column by filling it with a solution of 3-(trimethoxysilyl)propyl methacrylate, hydrochloric acid, water, toluene (porogen), and a photoinitiator (Irgacure 1800) and exposing it to UV light at 365 nm for 5 min. The separation column (30 cm x 75 microm I.D.) contains between the inlet and outlet frits a 15-cm packed segment filled with 5-microm silica particles modified with the chiral compound (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine. A detection window (1 mm long) is placed immediately after the outlet frit. To demonstrate the performance of this chiral separation column, mixtures of 16 different amino acids (three of which are not naturally occurring) derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole were separated by capillary chromatography. The enantiomeric separation of the column results in a resolution ranging from 1.21 to 8.29, and a plate height ranging from 8.7 to 39 microm.

    View details for Web of Science ID 000170359200018

    View details for PubMedID 11521865

  • Enantiomeric separation of amino acids and nonprotein amino acids using a particle-loaded monolithic column ELECTROPHORESIS Kato, M., Dulay, M. T., Bennett, B., Chen, J. R., Zare, R. N. 2000; 21 (15): 3145-3151

    Abstract

    A solution is prepared of 5 microm silica particles modified with (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine (particle 1) or (S)-N-3,5-dinitrophenylaminocarbonyl-valine (particle 2) suspended in liquid tetraethylorthosilicate, ethanol, and aqueous hydrochloric acid. This solution is injected under pressure into a 30 cm long, 75 microm inner diameter capillary column and heated for 1 h at 120 degrees C after which the modified particles are embedded in a monolithic column of sol gel. The packed column measures approximately 15 cm from the inlet to the window used to view the laser-induced fluorescence. Thirteen different amino acids and three nonprotein amino acids are derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) before injection onto the column for capillary electrochromatographic separation. The enantiomeric separation of the monolithic column packed with particle 1 results in a resolution ranging from 1.14 to 4.45, whereas that packed with particle 2 results in a resolution ranging from 0.79 to 1.17. On the basis of resolution and amount of chiral packing material the enantiomeric separation obtained by capillary electrochromatography is judged to be superior to that obtained previously with high performance liquid chromatography (HPLC).

    View details for Web of Science ID 000089318300012

    View details for PubMedID 11001212

  • Softening of fused-silica capillaries during particle packing ELECTROPHORESIS Chen, J. R., Dulay, M. T., Zare, R. N. 2000; 21 (7): 1430-1431

    Abstract

    When a semipreparative capillary electrochromatography (CEC) capillary is packed with silica particles and exposed to solvent, its mechanical strength is markedly reduced. In our studies, a fused-silica capillary (internal diameter > 200 microm and wall thickness < 150 microm) was packed under pressure (approximately 200 psi) with spherical silica particles (1.5-5 microm) suspended in water or various common organic solvents. After one hour of exposure, the capillary can be readily deformed, and it keeps its deformed shape upon release of the force causing deformation. It is suggested that capillary softening is promoted through the propagation of internal microcracks that have been caused by action of the particles during packing in the presence of solvent. Application of a protective coating to the inside of the capillary is found to reduce or eliminate capillary softening.

    View details for Web of Science ID 000087022300025

    View details for PubMedID 10826691

  • Macroporous photopolymer frits for capillary electrochromatography ANALYTICAL CHEMISTRY Chen, J. R., Dulay, M. T., Zare, R. N., Svec, F., Peters, E. 2000; 72 (6): 1224-1227

    View details for Web of Science ID 000085975200018

  • Preparation and characterization of monolithic porous capillary columns loaded with chromatographic particles ANALYTICAL CHEMISTRY Dulay, M. T., Kulkarni, R. P., Zare, R. N. 1998; 70 (23): 5103-5107

    Abstract

    Using sol-gel technology, a porous glass matrix (xerogel) is formed in a capillary column and acts as a support for a stationary phase of chromatographic particles used in capillary electrochromatography. Preparation of the sol-gel matrix and immobilization of the octadecylsilica (ODS) stationary phase occur in a single step. The presence of the particles in the column greatly reduces matrix cracking caused by internal pressure differentials within the pores of the sol-gel matrix. Good electroosmotic flow is achieved in part because of the inherent negative charge of both the particles and the sol-gel matrix. The performance of these sol-gel/ODS capillary columns was evaluated with a mixture of aromatic and nonaromatic organic compounds. Efficiencies of up to 80 000 plates/m were observed in columns with immobilized 3-μm ODS particles. The efficiency and resolution are enhanced when 3-μm ODS particles are used in place of the 5-μm particles.

    View details for Web of Science ID 000077278700046

    View details for PubMedID 21644688

  • Evidence for the extraterrestrial origin of polycyclic aromatic hydrocarbons in the Martian meteorite ALH84001 General Discussion on Chemistry and Physics of Molecules and Grains in Space Clemett, S. J., Dulay, M. T., Gillette, J. S., Chillier, X. D., Mahajan, T. B., Zare, R. N. ROYAL SOC CHEMISTRY. 1998: 417–436

    Abstract

    Possible sources of terrestrial contamination are considered for the observation of polycyclic aromatic hydrocarbons (PAHs) in the Martian meteorite ALH84001. Contamination is concluded to be negligible.

    View details for Web of Science ID 000076353800024

    View details for PubMedID 9809015

  • The template synthesis and X-ray characterization of pyrrole-derived hexadentate uranyl(VI) Schiff-base macrocyclic complexes INORGANICA CHIMICA ACTA Sessler, J. L., Mody, T. D., Dulay, M. T., ESPINOZA, R., Lynch, V. 1996; 246 (1-2): 23-30

    View details for Web of Science ID A1996UT89800004

  • Automated capillary electrochromatography: Reliability and reproducibility studies JOURNAL OF CHROMATOGRAPHY A Dulay, M. T., Yan, C., Rakestraw, D. J., Zare, R. N. 1996; 725 (2): 361-366

    Abstract

    The routine application of capillary electrochromatography (CEC) is demonstrated by incorporating 75 microns I.D. capillaries packed with 3 microns octadecylsilica (ODS) particles into a commercial CZE instrument. A mixture of several neutral compounds is separated into its components with an average efficiency up to 181 000 plates/m in less than 8 min. Hundreds of consecutive runs are performed over a period of weeks from which it is concluded that the reproducibility of the capacity factors is better than 2% and that CEC separations can be achieved in a reliable and routine manner.

    View details for Web of Science ID A1996UB61000015

    View details for PubMedID 8900577

https://orcid.org/0000-0002-4678-3480