Biology subjects

Appel, E. A.

Publications and source records attributed to Appel, E. A..

18 recordsLinked to original sources

bioRxiv2026

Structure-Property-Performance Engineering of Hydrogel Depots for Long-Acting Peptide Delivery

Controlled release systems for subcutaneous peptide delivery often exhibit a pronounced initial burst release followed by inadequate maintenance of therapeutic exposure, limiting depot lifetime and increasing pharmacokinetic variability. Here, we engineer a dynamic, injectable hydrogel depot technology for months-long delivery of lipidated peptides. Using semaglutide as a model, we establish a modular formulation framework integrating: (i) formulation-driven tuning of depot mechanics to control release kinetics, (ii) cargo complexation strategies leveraging hydrophobic and multivalent ion-mediated interactions, and (iii) oxidative stabilization through sacrificial antioxidant excipients. We evaluated depot performance by rheology, in vitro cargo release, and in vivo pharmacokinetic and pharmacodynamic studies in rodents. Optimized formulations sustained semaglutide exposure for over six weeks from a single administration with two-fold reduction in peak-to-trough exposure and comparable total bioavailability relative to daily dosing, resulting in improved glucose control, weight regulation, and preservation of pancreatic islet content. These results suggest potential for quarterly dosing in humans. Together, this work establishes integrated and generalizable structure-property-performance relationships that account for cargo-matrix and cargo-excipient interactions across burst, diffusion, and erosion regimes to inform a practical formulation framework for engineering long-acting depots for sustained peptide delivery.

bioengineering↗

bioRxiv2025

Long-acting hydrogel-based depot formulations of tirzepatide and semaglutide for the management of type 2 diabetes and weight

Several incretin hormone therapies have been clinically approved and have revolutionized the treatment of diabetes and obesity. Promising therapeutics include semaglutide (Ozempic(R) and Wegovy(R)), an agonist for glucagon-like peptide-1 (GLP-1) receptor, and tirzepatide (Mounjaro(R)), a dual agonist for GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptors. These molecules help to regulate blood glucose levels, enhance insulin secretion and sensitivity, and reduce appetite. Currently, these treatments require weekly injections, which can be challenging for patients to adhere to. We recently reported the development of an injectable hydrogel depot technology enabling months-long release of semaglutide (Sema). Here, we further develop this technology for improved prolonged release of both Sema and tirzepatide (TZP). In a rat model of diabetes, we show a single administration of hydrogel-based formulations of either Sema or TZP maintained relevant drug levels for over 6 weeks. In these studies, single administrations of long-acting hydrogel-based therapies of Sema or TZP were similarly effective at regulating blood glucose and weight compared to daily injections of either Sema or TZP in standard aqueous vehicles. This hydrogel depot technology is easy to manufacture, injectable, and exhibits excellent biocompatibility, enabling months-long-acting treatments with the potential to improve management of diabetes and weight.

bioengineering↗

bioRxiv2025

Engineering Sustained-Release Broadly Neutralizing Antibody Formulations

Sustained serum levels of broadly neutralizing antibodies (bnAbs) are crucial for effective passive immunization against infectious diseases as protection persists only while these bnAbs remain at adequate concentrations within the body. Current obstacles, such as poor pharmacokinetics (PK) and burdensome administration, must be overcome to make bnAbs a viable option for pre- and post-exposure prophylaxis. In this work, we explore how a polymer-nanoparticle (PNP) hydrogel depot technology can be engineered to prolong protein delivery. In-vivo studies in mice and rats demonstrate prolonged protein release, and modeling efforts predict the impact of both the elimination half-life of the active pharmaceutical ingredient and hydrogel depot volume on overall pharmacokinetics. Moreover, flow cytometry characterization reveals that immune cell infiltration into the hydrogel depot can result in faster-than-expected release of antibody cargo on account of active transport via cellular uptake. We then demonstrate that co-formulation of antibodies with an anti-inflammatory agent reduces cellular infiltration and resulting active transport, further extending delivery and pharmacokinetics. Finally, multicompartmental modeling predicts the human PK profiles of clinically relevant HIV bnAbs delivered via subcutaneous hydrogel injection. These findings aid in the development of next generation hydrogel materials that stabilize and slowly release bnAbs for long-term pre-exposure immunoprophylaxis.

bioengineering↗

bioRxiv2024

Sustained exposure to multivalent antigen-decorated nanoparticles generates broad anti-coronavirus responses

The threat of future coronavirus pandemics requires developing cost-effective vaccine technologies that provide broad and long-lasting protection against diverse circulating and emerging strains. Here we report a multivalent liposomal hydrogel depot vaccine technology comprising the receptor binding domain (RBD) of up to four relevant SARS and MERS coronavirus strains non-covalently displayed on the surface of the liposomes within the hydrogel structure. The multivalent presentation and sustained exposure of RBD antigens improved the potency, neutralizing activity, durability, and consistency of antibody responses across homologous and heterologous coronavirus strains in a naive murine model. When administrated in animals previously exposed to the wild-type SARS-CoV-2 antigens, liposomal hydrogels elicited durable antibody responses against the homologous SARS and MERS strains for over 6 months and elicited neutralizing activity against the immune-evasive SARS-CoV-2 variant Omicron BA.4/BA.5. Overall, the tunable antigen-decorated liposomal hydrogel platform we report here generates robust and durable humoral responses across diverse coronaviruses, supporting global efforts to effectively respond to future viral outbreaks. Progress and PotentialRapidly mutating infectious diseases such as influenza, HIV, and COVID-19 pose serious threats to human health. Yet, most vaccines still do not mount durable protection against mutagenic viruses and fail to induce broad responses to protect against emergent strains. Materials approaches to vaccine design, such as employing sustained delivery approaches or decorating nanoparticle constructs with multiple antigens, have shown promise in improving the breadth and potency of vaccines. Yet, these approaches typically require cumbersome chemistries and have not been explored in pre-exposed populations over clinically relevant time scales. Here, we report the development of an injectable liposomal hydrogel depot technology capable of prolonged presentation of multiple coronavirus antigens non-covalently coordinated on the surface of the liposomes forming the hydrogel structure. These hydrogels improve the potency, durability and breadth of vaccine response and are easy to fabricate, enabling the rapid design of next generation vaccines that confer protection against rapidly evolving pandemics.

bioengineering↗

bioRxiv2024

A thiol--ene click-based strategy to customize injectable polymer--nanoparticle hydrogel properties for therapeutic delivery

Polymer-nanoparticle (PNP) hydrogels are a promising injectable biomaterial platform that has been used for a wide range of biomedical applications including adhesion prevention, adoptive cell delivery, and controlled drug release. By tuning the chemical, mechanical, and erosion properties of injected hydrogel depots, additional control over cell compatibility and pharmaceutical release kinetics may be realized. Here, we employ thiol-ene click chemistry to prepare a library of modified hydroxypropylmethylcellulose (HPMC) derivatives for subsequent use in PNP hydrogel applications. When combined with poly(ethylene glycol)-b-poly(lactic acid) nanoparticles, we demonstrate that systematically altering the hydrophobic, steric, or pi stacking character of HPMC modifications can readily tailor the mechanical properties of PNP hydrogels. Additionally, we highlight the compatibility of the synthetic platform for the incorporation of cysteine-bearing peptides to access PNP hydrogels with improved bioactivity. Finally, through leveraging the tunable physical properties afforded by this method, we show hydrogel retention time in vivo can be dramatically altered without sacrificing mesh size or cargo diffusion rates. This work offers a route to optimize PNP hydrogels for a variety of translational applications and holds promise in the highly tunable delivery of pharmaceuticals and adoptive cells.

bioengineering↗

bioRxiv2023

Label-Free Composition Analysis of Supramolecular Polymer - Nanoparticle Hydrogels by Reversed-Phase Liquid Chromatography Coupled with a Charged Aerosol Detector

Supramolecular hydrogels formed through polymer-nanoparticle interactions are promising biocompatible materials for translational medicines. This class of hydrogels exhibits shear-thinning behavior and rapid recovery of mechanical properties following applied stresses, providing desirable attributes for formulating sprayable and injectable therapeutics. Characterization of hydrogel composition and loading of encapsulated drugs is critical to achieving desired rheological behavior as well as tunable in vitro and in vivo payload release kinetics. However, quantitation of hydrogel compositions is challenging due to material complexity, heterogeneity, high molecular weight, and the lack of chromophores. Here, we present a label-free approach to simultaneously determine hydrogel polymeric components and encapsulated payloads by coupling a reversed phase liquid chromatographic method with a charged aerosol detector (RPLC-CAD). The hydrogel studied consists of modified hydroxypropylmethylcellulose, self-assembled PEG-b-PLA nanoparticles, and a therapeutic compound, Bimatoprost. The three components were resolved and quantitated using the RPLC-CAD method with a C4 stationary phase. The method demonstrated robust performance, applicability to alternative cargos (i.e. proteins), and was suitable for composition analysis as well as for evaluating in vitro release of cargos from the hydrogel. Moreover, this method can be used to monitor polymer degradation and material stability, which can be further elucidated by coupling the RPLC method with high resolution mass spectrometry and a Fourier-transform based deconvolution algorithm. To our knowledge, this is the first RPLC-CAD method for characterizing the critical quality attributes of supramolecular hydrogels. We envision this analytical strategy could be generalized to characterize other classes of supramolecular hydrogels, establish structure-property relationships, and provide rational design guidance in hydrogel drug product development.

biochemistry↗

bioRxiv2023

Sustained Delivery of GLP-1 Receptor Agonists from Injectable Biomimetic Hydrogels Improves Treatment of Diabetes

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. GLP-1 in itself is rapidly degraded, but long-acting GLP-1 receptor agonists (GLP-1 RAs) have become central in the treatment of T2D because of the beneficial effects extending also beyond glucose control. Currently, these therapeutics must be injected either daily or weekly or taken daily orally, leaving room for technological innovations that enable less frequent administrations, which will reduce patient burden and increase patient compliance. An ideal GLP-1 RA drug product would provide continuous therapy for upwards of four months from a single administration to match the cadence with which T2D patients typically visit their physician. In this work, we leveraged an injectable hydrogel depot technology to develop a long-acting GLP-1 RA drug product. By modulating the hydrogel properties to tune GLP-1 RA retention within the hydrogel depot, we engineered formulations capable of months-long GLP-1 RA delivery. Using a rat model of T2D, we confirmed that a single injection of hydrogel-based therapies exhibits sustained exposure of GLP-1 RA over 42 days, corresponding to a once-every four month therapy in humans. Moreover, these hydrogel therapies maintained optimal management of blood glucose and weight comparable to daily injections of a leading GLP-1 RA drug molecule. The pharmacokinetics and pharmacodynamics of these hydrogel-based long-acting GLP-1 RA treatments are promising for development of novel therapies reducing treatment burden for more effective management of T2D. Progress and PotentialWhile insufficient access to quality healthcare is problematic for consistent management of Type II diabetes (T2D), poor adherence to burdensome treatment regimens is one of the greatest challenges for disease management. Glucagon-like peptide 1 (GLP1) drugs have become central to the treatment of T2D due to their many beneficial effects beyond improving glucose control. Unfortunately, while optimization of GLP1 drugs has reduced treatment frequency from daily to weekly, significant patient burden still leads to poor patience compliance. In this work we developed an injectable hydrogel technology to enable GLP1 drugs only requiring administration once every four months. We showed in a rat model of T2D that one injection of a hydrogel-based therapy improves management of blood glucose and weight when compared with daily injections of the leading drug used clinically. These hydrogel-based GLP1 treatments are promising for reducing treatment burden and more effectively managing T2D. Future ImpactA GLP-1-based drug product providing four months of continuous therapy per administration could be transformational for the management of Type II diabetes (T2D). One of the most challenging aspects of diabetes management with GLP-1 mimics is maintenance of consistent levels of the drugs in the body, which is complicated by poor patient compliance on account of the high frequency of dosing required for current treatments. By leveraging a unique sustained release hydrogel depot technology we develop a months-long GLP-1 drug product candidate that has the potential to reduce patient burden and improving diabetes management. Overall, the hydrogel technology we describe here can dramatically reduce the frequency of therapeutic interventions, significantly increasing patient quality of life and reducing complications of diabetes management. Our next steps will focus on optimization of the drug formulations in a swine model of T2D, which is the most advanced and translationally-relevant animal model for these types of therapeutics. The long-term vision for this work is to translate lead candidate drug products towards clinical evaluation, which will also require comprehensive safety evaluation in multiple species and manufacturing our these materials according to Good Manufacturing Practices. The months-long-acting GLP-1 drug product that will come from this work has the potential to afford thus far unrealized therapeutic impact for the hundreds of millions of people with diabetes worldwide.

bioengineering↗

bioRxiv2022

Polyacrylamide-based Hydrogel Coatings Improve Biocompatibility of Implanted Pump Devices

The introduction of transcutaneous and subcutaneous implants and devices into the human body instigates fouling and foreign body responses 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. In this work we sought to develop novel materials that can be used as coatings on devices. We first synthesized a library of polyacrylamide-based copolymer hydrogels and implanted them into the subcutaneous space of mice to evaluate their biocompatibility. We sought to discover copolymer hydrogel formulations eliciting less fibrous capsule formation and lower overall inflammation than gold standard materials such as PEG and polyzwitterions. The top performing copolymer hydrogel materials were then shown to improve the biocompatibility of a commonly used medical material, PDMS. Lastly, we applied the leading hydrogel coating to the catheter tips of insulin pumps. In a rat model of insulin deficient diabetes, the functional lifetime of hydrogel-coated devices was extended over uncoated pumps. 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, such as those with diabetes.

bioengineering↗

bioRxiv2022

Formulation excipients and their role in insulin stability and association state in formulation

While excipients are often overlooked as the "inactive" ingredients in pharmaceutical formulations, they often play a critical role in protein stability and absorption kinetics. Recent work has identified an ultrafast absorbing insulin formulation that is the result of excipient modifications. Specifically, the insulin monomer can be isolated by replacing zinc and the phenolic preservative metacresol with phenoxyethanol as an antimicrobial agent and an amphiphilic acrylamide copolymer excipient for stability. A greater understanding is needed of the interplay between excipients, insulin association state, and stability in order to optimize this formulation. Here, we formulated insulin with different preservatives and stabilizing excipient concentrations using both insulin lispro and regular human insulin and assessed the insulin association states using analytical ultracentrifugation as well as formulation stability. We determined that phenoxyethanol is required to eliminate hexamers and promote a high monomer content even in a zinc-free lispro formulation. There is also a concentration dependent relationship between the concentration of polyacrylamide-based copolymer excipient and insulin stability, where a concentration greater than 0.1 g/mL copolymer is required for a mostly monomeric zinc-free lispro formulation to achieve stability exceeding that of Humalog in a stressed aging assay. Further, we determined that under the formulation conditions tested zinc-free regular human insulin remains primarily hexameric and is not at this time a promising candidate for rapid-acting formulations.

bioengineering↗

bioRxiv2022

Subcutaneous delivery of an antibody against SARS-CoV-2 from a supramolecular hydrogel depot

Prolonged maintenance of therapeutically-relevant levels of broadly neutralizing antibodies (bnAbs) is necessary to enable passive immunization against infectious disease. Unfortunately, protection only lasts for as long as these bnAbs remain present at a sufficiently high concentration in the body. Poor pharmacokinetics and burdensome administration are two challenges that need to be addressed in order to make pre- and post-exposure prophylaxis with bnAbs feasible and effective. In this work, we develop a supramolecular hydrogel as an injectable, subcutaneous depot to encapsulate and deliver antibody drug cargo. This polymer-nanoparticle (PNP) hydrogel exhibits shear-thinning and self-healing properties that are required for an injectable drug delivery vehicle. In vitro drug release assays and diffusion measurements indicate that the PNP hydrogels prevent burst release and slow the release of encapsulated antibodies. Delivery of bnAbs against SARS-CoV-2 from PNP hydrogels is compared to standard routes of administration in a preclinical mouse model. We develop a multi-compartment model to understand the ability of these subcutaneous depot materials to modulate the pharmacokinetics of released antibodies; the model is extrapolated to explore the requirements needed for novel materials to successfully deliver relevant antibody therapeutics with different pharmacokinetic characteristics.

bioengineering↗

bioRxiv2022

Yield Stress and Creep Control Depot Formation and Persistence of Injectable Hydrogels Following Subcutaneous Administration

Hydrogels that can be injected into the body using standard needles or catheters enable a minimally invasive strategy to prolong local delivery of therapeutic drug and cellular cargo. In particular, physically crosslinked hydrogels exhibit shear-thinning and self-healing behaviors enabling facile injectability and depot formation upon administration. While prior efforts to characterize these systems have focused on injectability and cargo release behaviors, prediction of cargo release in the body often assumes the materials form a depot rather than spreading out upon administration. Here, we evaluate how hydrogel rheology correlates with depot formation and persistence following subcutaneous administration in mice with two physicochemically-distinct, physically crosslinked hydrogel systems. We evaluate calcium-alginate and polymer-nanoparticle hydrogel systems exhibiting variable mechanical behaviors across several rheological properties (stiffness, viscoelasticity, yield stress, and creep). By relating measured rheological properties to depot formation and persistence time following subcutaneous administration, we identify that yield stress is predictive of initial depot formation while creep is predictive of depot persistence. Indeed, only materials with yield stresses greater than 25 Pa form robust depots and reduced creep correlates with longer depot persistence. These findings provide predictive insights into design considerations for hydrogel technologies capable of extended controlled release of therapeutic cargo.

bioengineering↗

bioRxiv2021

Real-time monitoring of drug pharmacokinetics within tumor tissue in live animals

The efficacy and safety of a chemotherapy regimen fundamentally depends on its pharmacokinetics. This is currently measured based on blood samples, but the abnormal vasculature and physiological heterogeneity of the tumor microenvironment can produce radically different drug pharmacokinetics relative to the systemic circulation. We have developed an implantable microelectrode array sensor that can collect such tissue-based pharmacokinetic data by simultaneously measuring intratumoral pharmacokinetics from multiple sites. We employ gold nanoporous microelectrodes that maintain robust sensor performance even after repeated tissue implantation and extended exposure to the tumor microenvironment. We demonstrate continuous in vivo monitoring of concentrations of the chemotherapy drug doxorubicin at multiple tumor sites in a rodent model, and demonstrate clear differences in pharmacokinetics relative to the circulation that could meaningfully affect drug efficacy and safety. This platform could prove valuable for preclinical in vivo characterization of cancer therapeutics, and may offer a foundation for future clinical applications.

bioengineering↗

bioRxiv2021

Engineering Insulin Cold Chain Resilience to Improve Global Access

There are 150 million people with diabetes worldwide who require insulin replacement therapy and the prevalence of diabetes is rising fastest in middle and low-income countries. Current formulations require costly refrigerated transport and storage to prevent loss of insulin integrity. This study shows the development of simple "drop-in" amphiphilic copolymer excipients to maintain formulation integrity, bioactivity, pharmacokinetics and pharmacodynamics for over 6 months when subjected to severe stressed aging conditions that cause current commercial formulation to fail in under 2 weeks. Further, when these copolymers are added to Humulin R (Eli Lilly) in original commercial packaging they prevent insulin aggregation for up to 4 days at 50 {degrees}C compared to less than 1 day for Humulin R alone. These copolymers demonstrate promise as simple formulation additives to increase the cold chain resilience of commercial insulin formulations, thereby expanding global access to these critical drugs for treatment of diabetes.

bioengineering↗

bioRxiv2021

Consistent Tumorigenesis with Self-Assembled Hydrogels Enables High-powered Murine Cancer Studies

Preclinical cancer research is heavily dependent on allograft and xenograft models, but current approaches to tumor inoculation yield inconsistent tumor formation and growth, ultimately wasting valuable resources (e.g., animals, time, and money) and limiting experimental progress. Here we demonstrate a method for tumor inoculation using self-assembled hydrogels to reliably generate tumors with low variance in growth. The observed reduction in model variance enables smaller animal cohorts, improved effect observation and higher powered studies.

bioengineering↗

bioRxiv2021

Ultra-fast insulin-pramlintide co-formulation for improved glucose management in diabetic rats

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, we use amphiphilic acrylamide copolymers 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 hours under stressed aging conditions, whereas commercial insulin lispro (Humalog) aggregates in 8 hours. The faster pharmacokinetics of monomeric insulin in this co-formulation resulted in increased insulin-pramlintide overlap of 75 {+/-} 6% compared to only 47 {+/-} 7% for separate injections. The co-formulation resulted in similar delay in gastric emptying compared to pramlintide delivered separately. In a glucose challenge, in rats the co-formulation reduced 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.

bioengineering↗

bioRxiv2020

Injectable hydrogels for sustained co-delivery of subunit vaccines enhance humoral immunity

Vaccines aim to elicit a robust, yet targeted, immune response. Failure of a vaccine to elicit such a response arises in part from inappropriate temporal control over antigen and adjuvant presentation to the immune system. In this work, we sought to exploit the immune systems natural response to extended pathogen exposure during infection by designing an easily administered slow-delivery vaccine platform. We utilized an injectable and self-healing polymer-nanoparticle (PNP) hydrogel platform to prolong the co-delivery of vaccine components to the immune system. We demonstrated that these hydrogels exhibit unique delivery characteristics whereby physicochemically distinct compounds (such as antigen and adjuvant) could be co-delivered over the course of weeks. When administered in mice, hydrogel-based sustained vaccine exposure enhanced the magnitude, duration, and quality of the humoral immune response compared to standard PBS bolus administration of the same model vaccine. We report that the creation of a local inflammatory niche within the hydrogel, coupled with sustained release of vaccine cargo, enhanced the magnitude and duration of germinal center responses in the lymph nodes. This strengthened germinal center response promoted greater antibody affinity maturation, resulting in a more than 1000-fold increase in antigen-specific antibody affinity in comparison to bolus immunization. In summary, this work introduces a simple and effective vaccine delivery platform that increases the potency and durability of subunit vaccines.

bioengineering↗

bioRxiv2020

Combinatorial Polyacrylamide Hydrogels for Preventing Biofouling on Implantable Biosensors

Biofouling on the surface of implanted medical devices severely hinders device functionality and drastically shortens device lifetime. Poly(ethylene glycol) and zwitterionic polymers are currently considered "gold standard" device coatings to reduce biofouling. To discover novel anti-biofouling materials, we created a combinatorial library of polyacrylamide-based copolymer hydrogels and screened their ability to prevent fouling from serum and platelet-rich plasma in a high-throughput parallel assay. We found certain non-intuitive copolymer compositions exhibit superior antibiofouling properties over current gold standard materials, and employed machine learning to identify key molecular features underpinning their performance. For validation, we coated the surfaces of electrochemical biosensors with our hydrogels and evaluated their anti-biofouling performance in vitro and in vivo in rodent models. Our copolymer hydrogels preserved device function and enabled continuous measurements of a small-molecule drug in vivo better than gold standard coatings. The novel methodology we describe enables the discovery of anti-biofouling materials that can extend the lifetime of real-time in vivo sensing devices.

bioengineering↗

bioRxiv2020

Continuous detection of glucose and insulin in live animals

Real-time biosensors that can continuously measure circulating biomolecules in vivo would provide valuable insights into a patients health status and their response to therapeutics even when there is considerable variability in pharmacokinetics and pharmacodynamics across patient populations. Unfortunately, current real-time biosensors are limited to a handful of analytes (e.g. glucose and blood oxygen) and are limited in sensitivity (high nanomolar). In this work, we describe a general approach for continuously and simultaneously measuring multiple analytes with picomolar sensitivity and sub-second temporal resolution. As exemplars, we report the simultaneous detection of glucose and insulin at picomolar concentrations in live diabetic rats. Using our system, we demonstrate the capacity to resolve inter-individual differences in the pharmacokinetic responses to insulin and discriminate profiles from different insulin formulations at a high temporal resolution. Critically, our approach is general and could be readily modified to continuously and simultaneously measure other circulating analytes in vivo by swapping the affinity reagents, thus making it a versatile tool for biomedical research.

bioengineering↗