Stanford Advisors

All Publications

  • Biomimetic Non-ergodic Aging by Dynamic-to-covalent Transitions in Physical Hydrogels. ACS applied materials & interfaces Sen, S., Dong, C., D'Aquino, A. I., Yu, A. C., Appel, E. A. 2024


    Hydrogels are soft materials engineered to suit a multitude of applications that exploit their tunable mechanochemical properties. Dynamic hydrogels employing noncovalent, physically cross-linked networks dominated by either enthalpic or entropic interactions enable unique rheological and stimuli-responsive characteristics. In contrast to enthalpy-driven interactions that soften with increasing temperature, entropic interactions result in largely temperature-independent mechanical properties. By engineering interfacial polymer-particle interactions, we can induce a dynamic-to-covalent transition in entropic hydrogels that leads to biomimetic non-ergodic aging in the microstructure without altering the network mesh size. This transition is tuned by varying temperature and formulation conditions such as pH, which allows for multivalent tunability in properties. These hydrogels can thus be designed to exhibit either temperature-independent metastable dynamic cross-linking or time-dependent stiffening based on formulation and storage conditions, all while maintaining structural features critical for controlling mass transport, akin to many biological tissues. Such robust materials with versatile and adaptable properties can be utilized in applications such as wildfire suppression, surgical adhesives, and depot-forming injectable drug delivery systems.

    View details for DOI 10.1021/acsami.4c03303

    View details for PubMedID 38862125

  • Use of a biomimetic hydrogel depot technology for sustained delivery of GLP-1 receptor agonists reduces burden of diabetes management. Cell reports. Medicine d'Aquino, A. I., Maikawa, C. L., Nguyen, L. T., Lu, K., Hall, I. A., Jons, C. K., Kasse, C. M., Yan, J., Prossnitz, A. N., Chang, E., Baker, S. W., Hovgaard, L., Steensgaard, D. B., Andersen, H. B., Simonsen, L., Appel, E. A. 2023; 4 (11): 101292


    Glucagon-like peptide-1 (GLP-1) is an incretin hormone and neurotransmitter secreted from intestinal L cells in response to nutrients to stimulate insulin and block glucagon secretion in a glucose-dependent manner. Long-acting GLP-1 receptor agonists (GLP-1 RAs) have become central to treating type 2 diabetes (T2D); however, these therapies are burdensome, as they must be taken daily or weekly. Technological innovations that enable less frequent administrations would reduce patient burden and increase patient compliance. Herein, we leverage an injectable hydrogel depot technology to develop a GLP-1 RA drug product capable of months-long GLP-1 RA delivery. Using a rat model of T2D, we confirm that one injection of hydrogel-based therapy sustains exposure of GLP-1 RA over 42 days, corresponding to a once-every-4-months therapy in humans. Hydrogel therapy maintains management of blood glucose and weight comparable to daily injections of a leading GLP-1 RA drug. This long-acting GLP-1 RA treatment is a promising therapy for more effective T2D management.

    View details for DOI 10.1016/j.xcrm.2023.101292

    View details for PubMedID 37992687

  • Polyacrylamide-based hydrogel coatings improve biocompatibility of implanted pump devices. Journal of biomedical materials research. Part A Chan, D., Maikawa, C. L., d'Aquino, A. I., Raghavan, S. S., Troxell, M. L., Appel, E. A. 2023


    The introduction of transcutaneous and subcutaneous implants and devices into the human body instigates fouling and foreign body responses (FBRs) that limit their functional lifetimes. Polymer coatings are a promising solution to improve the biocompatibility of such implants, with potential to enhance in vivo device performance and prolong device lifetime. Here we sought to develop novel materials for use as coatings on subcutaneously implanted devices to reduce the FBR and local tissue inflammation in comparison to gold standard materials such as poly(ethylene glycol) and polyzwitterions. We prepared a library of polyacrylamide-based copolymer hydrogels, which were selected from materials previously shown to exhibit remarkable antifouling properties with blood and plasma, and implanted them into the subcutaneous space of mice to evaluate their biocompatibility over the course of 1month. The top performing polyacrylamide-based copolymer hydrogel material, comprising a 50:50 mixture of N-(2-hydroxyethyl)acrylamide (HEAm) and N-(3-methoxypropyl)acrylamide (MPAm), exhibited significantly better biocompatibility and lower tissue inflammation than gold standard materials. Moreover, when applied to polydimethylsiloxane disks or silicon catheters as a thin coating (45±1mum), this leading copolymer hydrogel coating significantly improved implant biocompatibility. Using a rat model of insulin-deficient diabetes, we showed that insulin pumps fitted with HEAm-co-MPAm hydrogel-coated insulin infusion catheters exhibited improved biocompatibility and extended functional lifetime over pumps fitted with industry standard catheters. These polyacrylamide-based copolymer hydrogel coatings have the potential to improve device function and lifetime, thereby reducing the burden of disease management for people regularly using implanted devices.

    View details for DOI 10.1002/jbm.a.37521

    View details for PubMedID 36861657

  • Stable High-Concentration Monoclonal Antibody Formulations Enabled by an Amphiphilic Copolymer Excipient. Advanced therapeutics Klich, J. H., Kasse, C. M., Mann, J. L., Huang, Y., d'Aquino, A. I., Grosskopf, A. K., Baillet, J., Fuller, G. G., Appel, E. A. 2023; 6 (1)


    Monoclonal antibodies are a staple in modern pharmacotherapy. Unfortunately, these biopharmaceuticals are limited by their tendency to aggregate in formulation, resulting in poor stability and often requiring low concentration drug formulations. Moreover, existing excipients designed to stabilize these formulations are often limited by their toxicity and tendency to form particles such as micelles. Here, we demonstrate the ability of a simple "drop-in", amphiphilic copolymer excipient to enhance the stability of high concentration formulations of clinically-relevant monoclonal antibodies without altering their pharmacokinetics or injectability. Through interfacial rheology and surface tension measurements, we demonstrate that the copolymer excipient competitively adsorbs to formulation interfaces. Further, through determination of monomeric composition and retained bioactivity through stressed aging, we show that this excipient confers a significant stability benefit to high concentration antibody formulations. Finally, we demonstrate that the excipient behaves as an inactive ingredient, having no significant impact on the pharmacokinetic profile of a clinically relevant antibody in mice. This amphiphilic copolymer excipient demonstrates promise as a simple formulation additive to create stable, high concentration antibody formulations, thereby enabling improved treatment options such as a route-of-administration switch from low concentration intravenous (IV) to high concentration subcutaneous (SC) delivery while reducing dependence on the cold chain.

    View details for DOI 10.1002/adtp.202200102

    View details for PubMedID 36684707

    View details for PubMedCentralID PMC9854243

  • Injectable Polymer-Nanoparticle Hydrogel for the Sustained Intravitreal Delivery of Bimatoprost ADVANCED THERAPEUTICS Meany, E. L., Andaya, R., Tang, S., Kasse, C. M., Fuji, R. N., Grosskopf, A. K., D'Aquino, A. L., Bartoe, J. T., Ybarra, R., Shelton, A., Pederson, Z., Hu, C., Leung, D., Nagapudi, K., Ubhayakar, S., Wright, M., Yen, C., Appel, E. A. 2022
  • Stable High-Concentration Monoclonal Antibody Formulations Enabled by an Amphiphilic Copolymer Excipient ADVANCED THERAPEUTICS Klich, J. H., Kasse, C. M., Mann, J. L., Huang, Y., D'Aquino, A., Grosskopf, A. K., Baillet, J., Fuller, G. G., Appel, E. A. 2022
  • Delivery of CAR-T cells in a transient injectable stimulatory hydrogel niche improves treatment of solid tumors. Science advances Grosskopf, A. K., Labanieh, L., Klysz, D. D., Roth, G. A., Xu, P., Adebowale, O., Gale, E. C., Jons, C. K., Klich, J. H., Yan, J., Maikawa, C. L., Correa, S., Ou, B. S., d'Aquino, A. I., Cochran, J. R., Chaudhuri, O., Mackall, C. L., Appel, E. A. 2022; 8 (14): eabn8264


    Adoptive cell therapy (ACT) has proven to be highly effective in treating blood cancers, but traditional approaches to ACT are poorly effective in treating solid tumors observed clinically. Novel delivery methods for therapeutic cells have shown promise for treatment of solid tumors when compared with standard intravenous administration methods, but the few reported approaches leverage biomaterials that are complex to manufacture and have primarily demonstrated applicability following tumor resection or in immune-privileged tissues. Here, we engineer simple-to-implement injectable hydrogels for the controlled co-delivery of CAR-T cells and stimulatory cytokines that improve treatment of solid tumors. The unique architecture of this material simultaneously inhibits passive diffusion of entrapped cytokines and permits active motility of entrapped cells to enable long-term retention, viability, and activation of CAR-T cells. The generation of a transient inflammatory niche following administration affords sustained exposure of CAR-T cells, induces a tumor-reactive CAR-T phenotype, and improves efficacy of treatment.

    View details for DOI 10.1126/sciadv.abn8264

    View details for PubMedID 35394838

  • Hydrogel-Based Slow Release of a Receptor-Binding Domain Subunit Vaccine Elicits Neutralizing Antibody Responses Against SARS-CoV-2. Advanced materials (Deerfield Beach, Fla.) Gale, E. C., Powell, A. E., Roth, G. A., Meany, E. L., Yan, J., Ou, B. S., Grosskopf, A. K., Adamska, J., Picece, V. C., d'Aquino, A. I., Pulendran, B., Kim, P. S., Appel, E. A. 2021: e2104362


    The development of effective vaccines that can be rapidly manufactured and distributed worldwide is necessary to mitigate the devastating health and economic impacts of pandemics like COVID-19. The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, which mediates host cell entry of the virus, is an appealing antigen for subunit vaccines because it is efficient to manufacture, highly stable, and a target for neutralizing antibodies. Unfortunately, RBD is poorly immunogenic. While most subunit vaccines are commonly formulated with adjuvants to enhance their immunogenicity, clinically-relevant adjuvants Alum, AddaVax, and CpG/Alum are found unable to elicit neutralizing responses following a prime-boost immunization. Here, it has been shown that sustained delivery of an RBD subunit vaccine comprisingCpG/Alumadjuvant in an injectable polymer-nanoparticle (PNP) hydrogelelicited potentanti-RBD andanti-spikeantibody titers, providing broader protection against SARS-CoV-2 variants of concern compared to bolus administration of the same vaccine and vaccines comprising other clinically-relevant adjuvant systems. Notably, a SARS-CoV-2 spike-pseudotyped lentivirus neutralization assay revealed that hydrogel-based vaccines elicited potent neutralizing responses when bolus vaccines didnot. Together, these results suggest that slow delivery of RBD subunit vaccines with PNP hydrogels can significantly enhance the immunogenicity of RBD and induce neutralizing humoral immunity.

    View details for DOI 10.1002/adma.202104362

    View details for PubMedID 34651342

  • Ultra-Fast Insulin-Pramlintide Co-Formulation for Improved Glucose Management in Diabetic Rats. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Maikawa, C. L., Chen, P. C., Vuong, E. T., Nguyen, L. T., Mann, J. L., d'Aquino, A. I., Lal, R. A., Maahs, D. M., Buckingham, B. A., Appel, E. A. 2021: e2101575


    Dual-hormone replacement therapy with insulin and amylin in patients with type 1 diabetes has the potential to improve glucose management. Unfortunately, currently available formulations require burdensome separate injections at mealtimes and have disparate pharmacokinetics that do not mimic endogenous co-secretion. Here, amphiphilic acrylamide copolymers are used to create a stable co-formulation of monomeric insulin and amylin analogues (lispro and pramlintide) with synchronous pharmacokinetics and ultra-rapid action. The co-formulation is stable for over 16 h under stressed aging conditions, whereas commercial insulin lispro (Humalog) aggregates in 8 h. The faster pharmacokinetics of monomeric insulin in this co-formulation result in increased insulin-pramlintide overlap of 75 ± 6% compared to only 47 ± 7% for separate injections. The co-formulation results in similar delay in gastric emptying compared to pramlintide delivered separately. In a glucose challenge, in rats, the co-formulation reduces deviation from baseline glucose compared to insulin only, or separate insulin and pramlintide administrations. Further, comparison of interspecies pharmacokinetics of monomeric pramlintide suggests that pharmacokinetics observed for the co-formulation will be well preserved in future translation to humans. Together these results suggest that the co-formulation has the potential to improve mealtime glucose management and reduce patient burden in the treatment of diabetes.

    View details for DOI 10.1002/advs.202101575

    View details for PubMedID 34499434

  • Affinity-Directed Dynamics of Host-Guest Motifs for Pharmacokinetic Modulation via Supramolecular PEGylation. Biomacromolecules Maikawa, C. L., d'Aquino, A. I., Vuong, E. T., Su, B., Zou, L., Chen, P. C., Nguyen, L. T., Autzen, A. A., Mann, J. L., Webber, M. J., Appel, E. A. 2021


    Proteins are an impactful class of therapeutics but can exhibit suboptimal therapeutic performance, arising from poor control over the timescale of clearance. Covalent PEGylation is one established strategy to extend circulation time but often at the cost of reduced activity and increased immunogenicity. Supramolecular PEGylation may afford similar benefits without necessitating that the protein be permanently modified with a polymer. Here, we show that insulin pharmacokinetics can be modulated by tuning the affinity-directed dynamics of a host-guest motif used to non-covalently endow insulin with a poly(ethylene glycol) (PEG) chain. When administered subcutaneously, supramolecular PEGylation with higher binding affinities extends the time of total insulin exposure systemically. Pharmacokinetic modeling reveals that the extension in the duration of exposure arises specifically from decreased absorption from the subcutaneous depot governed directly by the affinity and dynamics of host-guest exchange. The lifetime of the supramolecular interaction thus dictates the rate of absorption, with negligible impact attributed to association of the PEG upon rapid dilution of the supramolecular complex in circulation. This modular approach to supramolecular PEGylation offers a powerful tool to tune protein pharmacokinetics in response to the needs of different disease applications.

    View details for DOI 10.1021/acs.biomac.1c00648

    View details for PubMedID 34314146

  • Multi-State Dynamic Coordination Complexes Interconverted through Counterion-Controlled Phase Transfer INORGANIC CHEMISTRY Cheng, H., Paul, M. K., D'Aquino, A., Stern, C. L., Mirkin, C. A. 2021; 60 (7): 4755-4763


    We studied a series of dynamic weak-link approach (WLA) complexes that can be shuttled between two immiscible solvents and switched between two structural states via ion exchange. Here, we established that hydrophobic anions transfer cationic, amphiphilic complexes from the aqueous phase to the organic phase, while a chloride source reverses the process. As a result of the dynamic metal coordination properties of WLA complexes, the denticity of these complexes (mono- to bi-) can be modulated as they partition into different phases. In addition, we discovered that heteroligated complexes bearing ligands of different donor strengths preferentially rearrange into two homoligated complexes that are phase-partitioned to maximize the number of stronger coordination bonds. This behavior is not observed in systems with one solvent, highlighting the dynamic and stimuli-responsive nature of hemilabile ligands in a multiphasic solvent environment. Taken together, this work shows that the highly reconfigurable WLA modality can enable the design of biphasic reaction networks or chemical separations driven by straightforward salt metathesis reactions.

    View details for DOI 10.1021/acs.inorgchem.0c03708

    View details for Web of Science ID 000637850300061

    View details for PubMedID 33719417

  • Engineering biopharmaceutical formulations to improve diabetes management. Science translational medicine Maikawa, C. L., d'Aquino, A. I., Lal, R. A., Buckingham, B. A., Appel, E. A. 2021; 13 (578)


    Insulin was first isolated almost a century ago, yet commercial formulations of insulin and its analogs for hormone replacement therapy still fall short of appropriately mimicking endogenous glycemic control. Moreover, the controlled delivery of complementary hormones (such as amylin or glucagon) is complicated by instability of the pharmacologic agents and complexity of maintaining multiple infusions. In this review, we highlight the advantages and limitations of recent advances in drug formulation that improve protein stability and pharmacokinetics, prolong drug delivery, or enable alternative dosage forms for the management of diabetes. With controlled delivery, these formulations could improve closed-loop glycemic control.

    View details for DOI 10.1126/scitranslmed.abd6726

    View details for PubMedID 33504649