Santiago (Santi) is interested in the intersection of materials science and immunotherapy, and is working to develop injectable hydrogels to stimulate the immune system to recognize and eliminate cancer. Santi is especially interested in leveraging the unique drug delivery capabilities provided by such materials systems in order to explore combination immunotherapy and the role of release kinetics on therapeutic efficacy and safety.
Honors & Awards
Siebel Scholar, Siebel Foundation (2018)
Sloan UCEM Fellow, Alfred P. Sloan Foundation (2016)
Lemelson Engineering Presidential Fellowship, MIT (2012)
National Science Foundation (NSF) Graduate Research Fellowship, National Science Foundation (2012)
Science, Technology, and Research Scholars Fellowship, Yale (2010)
Doctor of Philosophy, Massachusetts Institute of Technology (2018)
BS, Yale University, Biomedical Engineering (2012)
An ultrafast insulin formulation enabled by high-throughput screening of engineered polymeric excipients.
Science translational medicine
2020; 12 (550)
Insulin has been used to treat diabetes for almost 100 years; yet, current rapid-acting insulin formulations do not have sufficiently fast pharmacokinetics to maintain tight glycemic control at mealtimes. Dissociation of the insulin hexamer, the primary association state of insulin in rapid-acting formulations, is the rate-limiting step that leads to delayed onset and extended duration of action. A formulation of insulin monomers would more closely mimic endogenous postprandial insulin secretion, but monomeric insulin is unstable in solution using present formulation strategies and rapidly aggregates into amyloid fibrils. Here, we implement high-throughput-controlled radical polymerization techniques to generate a large library of acrylamide carrier/dopant copolymer (AC/DC) excipients designed to reduce insulin aggregation. Our top-performing AC/DC excipient candidate enabled the development of an ultrafast-absorbing insulin lispro (UFAL) formulation, which remains stable under stressed aging conditions for 25 ± 1 hours compared to 5 ± 2 hours for commercial fast-acting insulin lispro formulations (Humalog). In a porcine model of insulin-deficient diabetes, UFAL exhibited peak action at 9 ± 4 min, whereas commercial Humalog exhibited peak action at 25 ± 10 min. These ultrafast kinetics make UFAL a promising candidate for improving glucose control and reducing burden for patients with diabetes.
View details for DOI 10.1126/scitranslmed.aba6676
View details for PubMedID 32611683
A co-formulation of supramolecularly stabilized insulin and pramlintide enhances mealtime glucagon suppression in diabetic pigs.
Nature biomedical engineering
Treatment of patients with diabetes with insulin and pramlintide (an amylin analogue) is more effective than treatment with insulin only. However, because mixtures of insulin and pramlintide are unstable and have to be injected separately, amylin analogues are only used by 1.5% of people with diabetes needing rapid-acting insulin. Here, we show that the supramolecular modification of insulin and pramlintide with cucurbituril-conjugated polyethylene glycol improves the pharmacokinetics of the dual-hormone therapy and enhances postprandial glucagon suppression in diabetic pigs. The co-formulation is stable for over 100 h at 37 °C under continuous agitation, whereas commercial formulations of insulin analogues aggregate after 10 h under similar conditions. In diabetic rats, the administration of the stabilized co-formulation increased the area-of-overlap ratio of the pharmacokinetic curves of pramlintide and insulin from 0.4 ± 0.2 to 0.7 ± 0.1 (mean ± s.d.) for the separate administration of the hormones. The co-administration of supramolecularly stabilized insulin and pramlintide better mimics the endogenous kinetics of co-secreted insulin and amylin, and holds promise as a dual-hormone replacement therapy.
View details for DOI 10.1038/s41551-020-0555-4
View details for PubMedID 32393892
Layer-by-layer nanoparticles for the non-toxic delivery of interleukin-12 to orthotopic ovarian cancer
View details for Web of Science ID 000496473200123
- Binary Targeting of siRNA to Hematologic Cancer Cells In Vivo Using Layer-by-Layer Nanoparticles ADVANCED FUNCTIONAL MATERIALS 2019; 29 (20)
Solution Conditions Tune and Optimize Loading of Therapeutic Polyelectrolytes into Layer-by-Layer Functionalized Liposomes
2019; 13 (5): 5623–34
Layer-by-layer (LbL) nanoparticles offer great potential to the field of drug delivery, where these nanocomposites have been studied for their ability to deliver chemotherapeutic agents, small molecule inhibitors, and nucleic acids. Most exciting is their ability to encapsulate multiple functional elements, which allow nanocarriers to deliver complex combination therapies with staged release. However, relative to planar LbL constructs, colloidal LbL systems have not undergone extensive systematic studies that outline critical synthetic solution conditions needed for robust and efficient assembly. The multistaged process of adsorbing a series of materials onto a nanoscopic template is inherently complex, and facilitating the self-assembly of these materials depends on identifying proper solution conditions for each synthetic step and adsorbed material. Here, we focus on addressing some of the fundamental questions that must be answered in order to obtain a reliable and robust synthesis of nucleic acid-containing LbL liposomes. This includes a study of solution conditions, such as pH, ionic strength, salt composition, and valency, and their impact on the preparation of LbL nanoparticles. Our results provide insight into the selection of solution conditions to control the degree of ionization and the electrostatic screening length to suit the adsorption of nucleic acids and synthetic polypeptides. The optimization of these parameters led to a roughly 8-fold improvement in nucleic acid loading in LbL liposomes, indicating the importance of optimizing solution conditions in the preparation of therapeutic LbL nanoparticles. These results highlight the benefits of defining principles for constructing highly effective nanoparticle systems.
View details for DOI 10.1021/acsnano.9b00792
View details for Web of Science ID 000469886300069
View details for PubMedID 30986034
Binary Targeting of siRNA to Hematologic Cancer Cells In Vivo using Layer-by-Layer Nanoparticles.
Advanced functional materials
2019; 29 (20)
Using siRNA therapeutics to treat hematologic malignancies has been unsuccessful because blood cancer cells exhibit remarkable resistance to standard transfection methods. Herein we report the successful delivery of siRNA therapeutics with a dual-targeted, layer-by-layer nanoparticle (LbL-NP). The LbL-NP protects siRNA from nucleases in the bloodstream by embedding it within polyelectrolyte layers that coat a polymeric core. The outermost layer consists of hyaluronic acid (a CD44-ligand) covalently conjugated to CD20 antibodies. The CD20/CD44 dual-targeting outer layer provides precise binding to blood cancer cells, followed by receptor-mediated endocytosis of the LbL-NP. We use this siRNA delivery platform to silence B-cell lymphoma 2 (BCL-2), a pro-survival protein, in vitro and in vivo. The dual-targeting approach significantly enhanced internalization of BCL-2 siRNA in lymphoma and leukemia cells, which led to significant downregulation of BCL-2 expression. Systemic administration of the dual-targeted, siRNA-loaded nanoparticle induced apoptosis and hampered proliferation of blood cancer cells both in cell culture and in orthotopic non-Hodgkin's lymphoma animal models. These results provide the basis for approaches to targeting blood-borne cancers and other diseases, and suggest that LbL nanoassemblies are a promising approach for delivering therapeutic siRNA to hematopoetic cell types that are known to evade transfection by other means.
View details for DOI 10.1002/adfm.201900018
View details for PubMedID 31839764
View details for PubMedCentralID PMC6910249
Theranostic Layer-by-Layer Nanoparticles for Simultaneous Tumor Detection and Gene Silencing.
Angewandte Chemie (International ed. in English)
Layer-by-layer nanoparticles (NPs) are modular drug delivery vehicles that incorporate multiple functional materials through sequential deposition of polyelectrolytes onto charged nanoparticle cores. Herein, we combined the multicomponent features and tumor targeting capabilities of layer-by-layer assembly with functional biosensing peptides to create a new class of nanotheranostics. These NPs encapsulate a high weight percentage of siRNA while also carrying a synthetic biosensing peptide on the surface that is cleaved into a urinary reporter upon exposure to specific proteases overexpressed in the tumor microenvironment. Importantly, this biosensor reports back on a molecular signature characteristic to metastatic tumors and associated with poor prognosis, MMP9 protease overexpression. This nanotheranostic mediates noninvasive urinary-based diagnostics in mouse models of three different cancers with simultaneous gene silencing in flank and metastatic mouse models of ovarian cancer.
View details for DOI 10.1002/anie.201911762
View details for PubMedID 31747099
RNA-Peptide nanoplexes drug DNA damage pathways in high-grade serous ovarian tumors.
Bioengineering & translational medicine
2018; 3 (1): 26–36
DNA damaging chemotherapy is a cornerstone of current front-line treatments for advanced ovarian cancer (OC). Despite the fact that a majority of these patients initially respond to therapy, most will relapse with chemo-resistant disease; therefore, adjuvant treatments that synergize with DNA-damaging chemotherapy could improve treatment outcomes and survival in patients with this deadly disease. Here, we report the development of a nanoscale peptide-nucleic acid complex that facilitates tumor-specific RNA interference therapy to chemosensitize advanced ovarian tumors to frontline platinum/taxane therapy. We found that the nanoplex-mediated silencing of the protein kinase, MK2, profoundly sensitized mouse models of high-grade serous OC to cytotoxic chemotherapy by blocking p38/MK2-dependent cell cycle checkpoint maintenance. Combined RNAi therapy improved overall survival by 37% compared with platinum/taxane chemotherapy alone and decreased metastatic spread to the lungs without observable toxic side effects. These findings suggest (a) that peptide nanoplexes can serve as safe and effective delivery vectors for siRNA and (b) that combined inhibition of MK2 could improve treatment outcomes in patients currently receiving frontline chemotherapy for advanced OC.
View details for DOI 10.1002/btm2.10086
View details for PubMedID 29376131
View details for PubMedCentralID PMC5773954
Engineering nanolayered particles for modular drug delivery.
Journal of controlled release : official journal of the Controlled Release Society
2016; 240: 364–86
Layer-by-layer (LbL) based self-assembly of nanoparticles is an emerging and powerful method to develop multifunctional and tissue responsive nanomedicines for a broad range of diseases. This unique assembly technique is able to confer a high degree of modularity, versatility, and compositional heterogeneity to nanoparticles via the sequential deposition of alternately charged polyelectrolytes onto a colloidal template. LbL assembly can provide added functionality by directly incorporating a range of functional materials within the multilayers including nucleic acids, synthetic polymers, polypeptides, polysaccharides, and functional proteins. These materials can be used to generate hierarchically complex, heterogeneous thin films on an extensive range of both traditional and novel nanoscale colloidal templates, providing the opportunity to engineer highly precise systems capable of performing the numerous tasks required for systemic drug delivery. In this review, we will discuss the recent advancements towards the development of LbL nanoparticles for drug delivery and diagnostic applications, with a special emphasis on the incorporation of biostability, active targeting, desirable drug release kinetics, and combination therapies into LbL nanomaterials. In addition to these topics, we will touch upon the next steps for the translation of these systems towards the clinic.
View details for DOI 10.1016/j.jconrel.2016.01.040
View details for PubMedID 26809005
View details for PubMedCentralID PMC6450096
Layer-by-layer assembled fluorescent probes in the second near-infrared window for systemic delivery and detection of ovarian cancer.
Proceedings of the National Academy of Sciences of the United States of America
2016; 113 (19): 5179–84
Fluorescence imaging in the second near-infrared window (NIR-II, 1,000-1,700 nm) features deep tissue penetration, reduced tissue scattering, and diminishing tissue autofluorescence. Here, NIR-II fluorescent probes, including down-conversion nanoparticles, quantum dots, single-walled carbon nanotubes, and organic dyes, are constructed into biocompatible nanoparticles using the layer-by-layer (LbL) platform due to its modular and versatile nature. The LbL platform has previously been demonstrated to enable incorporation of diagnostic agents, drugs, and nucleic acids such as siRNA while providing enhanced blood plasma half-life and tumor targeting. This work carries out head-to-head comparisons of currently available NIR-II probes with identical LbL coatings with regard to their biodistribution, pharmacokinetics, and toxicities. Overall, rare-earth-based down-conversion nanoparticles demonstrate optimal biological and optical performance and are evaluated as a diagnostic probe for high-grade serous ovarian cancer, typically diagnosed at late stage. Successful detection of orthotopic ovarian tumors is achieved by in vivo NIR-II imaging and confirmed by ex vivo microscopic imaging. Collectively, these results indicate that LbL-based NIR-II probes can serve as a promising theranostic platform to effectively and noninvasively monitor the progression and treatment of serous ovarian cancer.
View details for DOI 10.1073/pnas.1521175113
View details for PubMedID 27114520
View details for PubMedCentralID PMC4868435
Highly scalable, closed-loop synthesis of drug-loaded, layer-by-layer nanoparticles.
Advanced functional materials
2016; 26 (7): 991–1003
Layer-by-layer (LbL) self-assembly is a versatile technique from which multicomponent and stimuli-responsive nanoscale drug carriers can be constructed. Despite the benefits of LbL assembly, the conventional synthetic approach for fabricating LbL nanoparticles requires numerous purification steps that limit scale, yield, efficiency, and potential for clinical translation. In this report, we describe a generalizable method for increasing throughput with LbL assembly by using highly scalable, closed-loop diafiltration to manage intermediate purification steps. This method facilitates highly controlled fabrication of diverse nanoscale LbL formulations smaller than 150 nm composed from solid-polymer, mesoporous silica, and liposomal vesicles. The technique allows for the deposition of a broad range of polyelectrolytes that included native polysaccharides, linear polypeptides, and synthetic polymers. We also explore the cytotoxicity, shelf life and long-term storage of LbL nanoparticles produced using this approach. We find that LbL coated systems can be reliably and rapidly produced: specifically, LbL-modified liposomes could be lyophilized, stored at room temperature, and reconstituted without compromising drug encapsulation or particle stability, thereby facilitating large scale applications. Overall, this report describes an accessible approach that significantly improves the throughput of nanoscale LbL drug-carriers that show low toxicity and are amenable to clinically relevant storage conditions.
View details for DOI 10.1002/adfm.201504385
View details for PubMedID 27134622
View details for PubMedCentralID PMC4847955
Tumor-Targeted Synergistic Blockade of MAPK and PI3K from a Layer-by-Layer Nanoparticle.
Clinical cancer research : an official journal of the American Association for Cancer Research
2015; 21 (19): 4410–19
Cross-talk and feedback between the RAS/RAF/MEK/ERK and PI3K/AKT/mTOR cell signaling pathways is critical for tumor initiation, maintenance, and adaptive resistance to targeted therapy in a variety of solid tumors. Combined blockade of these pathways-horizontal blockade-is a promising therapeutic strategy; however, compounded dose-limiting toxicity of free small molecule inhibitor combinations is a significant barrier to its clinical application.AZD6244 (selumetinib), an allosteric inhibitor of Mek1/2, and PX-866, a covalent inhibitor of PI3K, were co-encapsulated in a tumor-targeting nanoscale drug formulation-layer-by-layer (LbL) nanoparticles. Structure, size, and surface charge of the nanoscale formulations were characterized, in addition to in vitro cell entry, synergistic cell killing, and combined signal blockade. In vivo tumor targeting and therapy was investigated in breast tumor xenograft-bearing NCR nude mice by live animal fluorescence/bioluminescence imaging, Western blotting, serum cytokine analysis, and immunohistochemistry.Combined MAPK and PI3K axis blockade from the nanoscale formulations (160 ± 20 nm, -40 ± 1 mV) was synergistically toxic toward triple-negative breast (MDA-MB-231) and RAS-mutant lung tumor cells (KP7B) in vitro, effects that were further enhanced upon encapsulation. In vivo, systemically administered LbL nanoparticles preferentially targeted subcutaneous MDA-MB-231 tumor xenografts, simultaneously blocked tumor-specific phosphorylation of the terminal kinases Erk and Akt, and elicited significant disease stabilization in the absence of dose-limiting hepatotoxic effects observed from the free drug combination. Mice receiving untargeted, but dual drug-loaded nanoparticles exhibited progressive disease.Tumor-targeting nanoscale drug formulations could provide a more safe and effective means to synergistically block MAPK and PI3K in the clinic.
View details for DOI 10.1158/1078-0432.CCR-15-0013
View details for PubMedID 26034127
View details for PubMedCentralID PMC4624301