Protein–Polymer Delivery: Chemistry from the Cold Chain to the Clinic

Protein-polymer bioconjugation, immobilization, and encapsulation: a comparative review towards applicability, functionality, activity, and stability

Polymer-based biomaterials have received a lot of attention due to their biomedical, agricultural, and industrial potential. Soluble protein-polymer bioconjugates, immobilized proteins, and encapsulated proteins have been shown to tune enzymatic activity, improved pharmacokinetic ability, increased chemical and thermal stability, stimuli responsiveness, and introduced protein recovery. Controlled polymerization techniques, increased protein-polymer attachment techniques, improved polymer surface grafting techniques, controlled polymersome self-assembly, and sophisticated characterization methods have been utilized for the development of well-defined polymer-based biomaterials. In this review we aim to provide a brief account of the field, compare these methods for engineering biomaterials, provide future directions for the field, and highlight impacts of these forms of bioconjugation.

Microneedle-Mediated Delivery of Immunomodulators Restores Immune Privilege in Hair Follicles and Reverses Immune-Mediated Alopecia

Disorders in the regulatory arm of the adaptive immune system result in autoimmune-mediated diseases. While systemic immunosuppression is the prevailing approach to manage them, it fails to achieve long-lasting remission due to concomitant suppression of the regulatory arm and carries the risk of heightened susceptibility to infections and malignancies. Alopecia areata is a condition characterized by localized hair loss due to autoimmunity. The accessibility of the skin allows local rather than systemic intervention to avoid broad immunosuppression. It is hypothesized that the expansion of endogenous regulatory T cells (Tregs) at the site of antigen encounter can restore the immune balance and generate a long-lasting tolerogenic response. A hydrogel microneedle (MN) patch is therefore utilized for delivery of CCL22, a Treg-chemoattractant, and IL-2, a Treg survival factor to amplify them. In an immune-mediated murine model of alopecia, local bolstering of Treg numbers is shown, leading to sustained hair regrowth and attenuation of inflammatory pathways. In a humanized skin transplant mouse model, expansion of Tregs within human skin is confirmed without engendering peripheral immunosuppression. The patch offers high-loading capacity and shelf-life stability for prospective clinical translation. By harmonizing immune responses locally, the aim is to reshape the landscape of autoimmune skin disease management.

Metal-Drug Coordination Nanoparticles and Hydrogels for Enhanced Delivery

Drug delivery is a key component of nanomedicine, and conventional delivery relies on the adsorption or encapsulation of drug molecules to a nanomaterial. Many delivery vehicles contain metal ions, such as metal-organic frameworks, metal oxides, transition metal dichalcogenides, MXene, and noble metal nanoparticles. These materials have a high metal content and pose potential long-term toxicity concerns leading to difficulties for clinical approval. In this review, recent developments are summarized in the use of drug molecules as ligands for metal coordination forming various nanomaterials and soft materials. In these cases, the drug-to-metal ratio is much higher than conventional adsorption-based strategies. The drug molecules are divided into small-molecule drugs, nucleic acids, and proteins. The formed hybrid materials mainly include nanoparticles and hydrogels, upon which targeting ligands can be grafted to improve efficacy and further decrease toxicity. The application of these materials for addressing cancer, viral infection, bacterial infection inflammatory bowel disease, and bone diseases is reviewed. In the end, some future directions are discussed from fundamental research, materials science, and medicine.

The Promise and Potential of Metal-Organic Frameworks and Covalent Organic Frameworks in Vaccine Nanotechnology

The immune system's complexity and ongoing evolutionary struggle against deleterious pathogens underscore the value of vaccination technologies, which have been bolstering human immunity for over two centuries. Despite noteworthy advancements over these 200 years, three areas remain recalcitrant to improvement owing to the environmental instability of the biomolecules used in vaccines─the challenges of formulating them into controlled release systems, their need for constant refrigeration to avoid loss of efficacy, and the requirement that they be delivered via needle owing to gastrointestinal incompatibility. Nanotechnology, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), has emerged as a promising avenue for confronting these challenges, presenting a new frontier in vaccine development. Although these materials have been widely explored in the context of drug delivery, imaging, and cancer immunotherapy, their role in immunology and vaccine-related applications is a recent yet rapidly developing field. This review seeks to elucidate the prospective use of MOFs and COFs for biomaterial stabilization, eliminating the necessity for cold chains, enhancing antigen potency as adjuvants, and potentializing needle-free delivery of vaccines. It provides an expansive and critical viewpoint on this rapidly evolving field of research and emphasizes the vital contribution of chemists in driving further advancements.

A scalable synthesis of adjuvanting antigen depots based on metal-organic frameworks

Vaccines have saved countless lives by preventing and even irradicating infectious diseases. Commonly used subunit vaccines comprising one or multiple recombinant proteins isolated from a pathogen demonstrate a better safety profile than live or attenuated vaccines. However, the immunogenicity of these vaccines is weak, and therefore, subunit vaccines require a series of doses to achieve sufficient immunity against the pathogen. Here, we show that the biomimetic mineralization of the inert model antigen, ovalbumin (OVA), in zeolitic imidazolate framework-8 (ZIF-8) significantly improves the humoral immune response over three bolus doses of OVA (OVA 3×). Encapsulation of OVA in ZIF-8 (OVA@ZIF) demonstrated higher serum antibody titers against OVA than OVA 3×. OVA@ZIF vaccinated mice displayed higher populations of germinal center (GC) B cells and IgG1+ GC B cells as opposed to OVA 3×, indicative of class-switching recombination. We show that the mechanism of this phenomenon is at least partly owed to the metalloimmunological effects of the zinc metal as well as the sustained release of OVA from the ZIF-8 composite. The system acts as an antigen reservoir for antigen-presenting cells to traffic into the draining lymph node, enhancing the humoral response. Lastly, our model system OVA@ZIF is produced quickly at the gram scale in a laboratory setting, sufficient for up to 20 000 vaccine doses.

Investigating BioCaRGOS, a Sol-Gel Matrix for the Stability of Heme Proteins under Enzymatic Degradation and Low pH

There have been significant advances in the development of vaccines for the prevention of various infectious diseases in the last few decades. These vaccines are mainly composed of proteins and nucleic acids. Poor handling and storage, exposure to high temperatures that lead to enzymatic degradation, pH variation, and various other stresses can denature the proteins or nucleic acids present in any vaccine formulation. Therefore, it is necessary to maintain a proper environment to preserve the integrity of biospecimens. To overcome these challenges, we report a practical and user-friendly approach for sol-gels called "BioCaRGOS" that can stabilize heme proteins not only in the presence of degrading enzymes and acidic pH but simultaneously maintain stability at room temperature. Heme proteins, such as myoglobin and cytochrome c, have been used for this study.

In vivo biocompatibility of ZIF-8 for slow release via intranasal administration

Zeolitic imidazolate framework-8 (ZIF-8) is becoming popular in research for its potential in antigen protection and for providing a thermally stable, slow-release platform. While papers applying this material for immunological applications are aplenty in the literature, studies that explore the biosafety of ZIF-8 in mammals-especially when administered intranasally-are not well represented. We checked the body clearance of uncoated and ZIF-8-coated liposomes and observed that the release slowed as ZIF-8 is easily degraded by mucosal fluid in the nasal cavity. We delivered varying doses of ZIF-8, checked its short- and long-term effects on diagnostic proteins found in blood serum, and found no noticeable differences from the saline control group. We also studied their lung diffusing capacity and tissue morphology; neither showed significant changes in morphology or function.

Self-assembly of a fluorescent virus-like particle for imaging in tissues with high autofluorescence

Virus-like particles (VLPs) are engineered nanoparticles that mimic the properties of viruses-like high tolerance to heat and proteases-but lack a viral genome, making them non-infectious. They are easily modified chemically and genetically, making them useful in drug delivery, enhancing vaccine efficacy, gene delivery, and cancer immunotherapy. One such VLP is Qβ, which has an affinity towards an RNA hairpin structure found in its viral RNA that drives the self-assembly of the capsid. It is possible to usurp the native way infectious Qβ self-assembles to encapsidate its RNA to place enzymes inside the VLP's lumen as a protease-resistant cage. Further, using RNA templates that mimic the natural self-assembly of the native capsid, fluorescent proteins (FPs) have been placed inside VLPs in a "one pot" expression system. Autofluorescence in tissues can lead to misinterpretation of results and unreliable science, so we created a single-pot expression system that uses the fluorescent protein smURFP, which avoids autofluorescence and has spectral properties compatible with standard commercial filter sets on confocal microscopes. In this work, we were able to simplify the existing "one-pot" expression system while creating high-yielding fluorescent VLP nanoparticles that could easily be imaged inside lung epithelial tissue.

Thermal stability of exenatide encapsulated in stratified dissolving microneedles during storage

As low-temperature storage and transportation of peptides require high costs, improving the dosage form of peptides can reduce costs. We developed a thermostable and fast-releasing stratified dissolving microneedle (SDMN) system for delivering exenatide (EXT) to patients with type 2 diabetes. Among the tested polymers, dextran and polyvinyl alcohol (PVA) were the best at stabilizing EXT under high-temperature storage for 9 weeks. The two polymers possess a relatively high glass transition temperature (T_g) and weak hydrogen bonding between PVA and EXT. Additionally, zinc sulfate (ZnSO₄) had a stabilizing effect on EXT among the selected stabilizers, suggesting that EXT formed a dimer after coordination with zinc ions (Zn²⁺). In addition, the denaturation temperature (T_m) of EXT was increased by adding ZnSO₄, thus stabilizing EXT. Accordingly, SDMNs consisting of a tip layer (dextran encapsulating the Zn²⁺-EXT complex) and a base layer (PVA) were fabricated. Within 2 min of implantation, the EXT loaded on the patch was quickly released into the skin. Transdermal pharmacokinetics studies showed that manufactured SDMNs generated comparable efficacy to subcutaneous injection. Significantly, the remaining EXT amount was not significantly different under storage at 40 °C and -20 °C for 3 months, supporting that the SDMN system had excellent delivery efficiency and stability, thus reducing the dependence on the cold chain.

Stable High-Concentration Monoclonal Antibody Formulations Enabled by an Amphiphilic Copolymer Excipient

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.

Rip it, stitch it, click it: A Chemist's guide to VLP manipulation

Viruses are some of nature's most ubiquitous self-assembled molecular containers. Evolutionary pressures have created some incredibly robust, thermally, and enzymatically resistant carriers to transport delicate genetic information safely. Virus-like particles (VLPs) are human-engineered non-infectious systems that inherit the parent virus' ability to self-assemble under controlled conditions while being non-infectious. VLPs and plant-based viral nanoparticles are becoming increasingly popular in medicine as their self-assembly properties are exploitable for applications ranging from diagnostic tools to targeted drug delivery. Understanding the basic structure and principles underlying the assembly of higher-order structures has allowed researchers to disassemble (rip it), reassemble (stitch it), and functionalize (click it) these systems on demand. This review focuses on the current toolbox of strategies developed to manipulate these systems by ripping, stitching, and clicking to create new technologies in the biomedical space.

Carrier gas triggered controlled biolistic delivery of DNA and protein therapeutics from metal-organic frameworks

The efficacy and specificity of protein, DNA, and RNA-based drugs make them popular in the clinic; however, these drugs are often delivered via injection, requiring skilled medical personnel, and producing biohazardous waste. Here, we report an approach that allows for their controlled delivery, affording either a burst or slow release without altering the formulation. We show that when encapsulated within zeolitic-imidazolate framework eight (ZIF-8), the biomolecules are stable in powder formulations and can be inoculated with a low-cost, gas-powered "MOF-Jet" into living animal and plant tissues. Additionally, their release profiles can be modulated through judicious selection of the carrier gas used in the MOF-Jet. Our in vitro and in vivo studies reveal that when CO₂ is used, it creates a transient and weakly acidic local environment that causes a near-instantaneous release of the biomolecules through an immediate dissolution of ZIF-8. Conversely, when air is used, ZIF-8 biodegrades slowly, releasing the biomolecules over a week. This is the first example of controlled-biolistic delivery of biomolecules using ZIF-8, which provides a powerful tool for fundamental and applied science research.

Long-Term Vaccine Delivery and Immunological Responses Using Biodegradable Polymer-Based Carriers

Biodegradable polymers are largely employed in the biomedical field, ranging from tissue regeneration to drug/vaccine delivery. The biodegradable polymers are highly biocompatible and possess negligible toxicity. In addition, biomaterial-based vaccines possess adjuvant properties, thereby enhancing immune responses. This Review introduces the use of different biodegradable polymers and their degradation mechanism. Different kinds of vaccines, as well as the interaction between the carriers with the immune system, then are highlighted. Natural and synthetic biodegradable micro-/nanoplatforms, hydrogels, and scaffolds for local or targeted and controlled vaccine release are subsequently discussed.

Thermal stabilization of diverse biologics using reversible hydrogels

Improving the thermal stability of biologics, including vaccines, is critical to reduce the economic costs and health risks associated with the cold chain. Here, we designed a versatile, safe, and easy-to-use reversible PEG-based hydrogel platform formed via dynamic covalent boronic ester cross-linking for the encapsulation, stabilization, and on-demand release of biologics. Using these reversible hydrogels, we thermally stabilized a wide range of biologics up to 65°C, including model enzymes, heat-sensitive clinical diagnostic enzymes (DNA gyrase and topoisomerase I), protein-based vaccines (H5N1 hemagglutinin), and whole viruses (adenovirus type 5). Our data support a generalized protection mechanism for the thermal stabilization of diverse biologics using direct encapsulation in reversible hydrogels. Furthermore, preliminary toxicology data suggest that the components of our hydrogel are safe for in vivo use. Our reversible hydrogel platform offers a simple material solution to mitigate the costs and risks associated with reliance on a continuous cold chain for biologic transport and storage.

Metal-Organic Framework Encapsulated Whole-Cell Vaccines Enhance Humoral Immunity against Bacterial Infection

The increasing rate of resistance of bacterial infection against antibiotics requires next generation approaches to fight potential pandemic spread. The development of vaccines against pathogenic bacteria has been difficult owing, in part, to the genetic diversity of bacteria. Hence, there are many potential target antigens and little a priori knowledge of which antigen/s will elicit protective immunity. The painstaking process of selecting appropriate antigens could be avoided with whole-cell bacteria; however, whole-cell formulations typically fail to produce long-term and durable immune responses. These complications are one reason why no vaccine against any type of pathogenic E. coli has been successfully clinically translated. As a proof of principle, we demonstrate a method to enhance the immunogenicity of a model pathogenic E. coli strain by forming a slow releasing depot. The E. coli strain CFT073 was biomimetically mineralized within a metal-organic framework (MOF). This process encapsulates the bacteria within 30 min in water and at ambient temperatures. Vaccination with this formulation substantially enhances antibody production and results in significantly enhanced survival in a mouse model of bacteremia compared to standard inactivated formulations.

PEGylated Nanoscale Metal-Organic Frameworks for Targeted Cancer Imaging and Drug Delivery

Nanoscale metal-organic frameworks (nMOFs) are a unique type of hybrid materials, which are broadly applicable as cargo delivery systems. However, the relatively low material stability and insufficient cancer cell interacting capacity have limited nMOFs' applications in cancer theranostics. Herein, a zirconium-based nMOF UiO-66-N₃ was synthesized, and its surface was covalently functionalized with alkyne-containing polyethylene glycol (PEG) via the azide-alkyne click chemistry. After that, F3 peptide was attached for targeting of cancer cells (the material was denoted as UiO-66-PEG-F3). Doxorubicin (DOX) served as a therapeutic drug and a fluorescent label in this study, and it was transported into UiO-66-PEG conjugates with sufficient drug loading efficiency. pH-responsive release of DOX from UiO-66 conjugates was witnessed. The structural integrity of UiO-66-N₃ was maintained post the surface modification process. Flow cytometry and confocal fluorescence microscopy revealed that DOX/UiO-66-PEG-F3 had stronger accumulation in MDA-MB-231 cells (nucleolin⁺) compared with DOX/UiO-66-PEG. In order to track the pharmacokinetic behavior (organ distribution profile) in vivo, the positron-emitting zirconium-89 (⁸⁹Zr) was incorporated into UiO-66-N₃. Similar PEGylation and F3 peptide conjugation resulted in the formation of ⁸⁹Zr-UiO-66-PEG-F3. Serial positron emission tomography (PET) imaging demonstrated that the preferential accumulation of ⁸⁹Zr-UiO-66-PEG-F3 in MDA-MB-231 tumors, and their liver clearance was faster than PEGylated UiO-66 using noncovalent methods. Thus, the PEGylated nMOFs using covalent strategies may find broad application in future cancer theranostics.

PhotothermalPhage: A Virus-Based Photothermal Therapeutic Agent

Virus-like particles (VLPs) are multifunctional nanocarriers that mimic the architecture of viruses. They can serve as a safe platform for specific functionalization and immunization, which provides benefits in a wide range of biomedical applications. In this work, a new generation immunophotothermal agent is developed that adjuvants photothermal ablation using a chemically modified VLP called bacteriophage Qβ. The design is based on the conjugation of near-infrared absorbing croconium dyes to lysine residues located on the surface of Qβ, which turns it to a powerful NIR-absorber called PhotothermalPhage. This system can generate more heat upon 808 nm NIR laser radiation than free dye and possesses a photothermal efficiency comparable to gold nanostructures, yet it is biodegradable and acts as an immunoadjuvant combined with the heat it produces. The synergistic combination of thermal ablation with the mild immunogenicity of the VLP leads to effective suppression of primary tumors, reduced lung metastasis, and increased survival time.

Translational Applications of Hydrogels

Advances in hydrogel technology have unlocked unique and valuable capabilities that are being applied to a diverse set of translational applications. Hydrogels perform functions relevant to a range of biomedical purposes-they can deliver drugs or cells, regenerate hard and soft tissues, adhere to wet tissues, prevent bleeding, provide contrast during imaging, protect tissues or organs during radiotherapy, and improve the biocompatibility of medical implants. These capabilities make hydrogels useful for many distinct and pressing diseases and medical conditions and even for less conventional areas such as environmental engineering. In this review, we cover the major capabilities of hydrogels, with a focus on the novel benefits of injectable hydrogels, and how they relate to translational applications in medicine and the environment. We pay close attention to how the development of contemporary hydrogels requires extensive interdisciplinary collaboration to accomplish highly specific and complex biological tasks that range from cancer immunotherapy to tissue engineering to vaccination. We complement our discussion of preclinical and clinical development of hydrogels with mechanical design considerations needed for scaling injectable hydrogel technologies for clinical application. We anticipate that readers will gain a more complete picture of the expansive possibilities for hydrogels to make practical and impactful differences across numerous fields and biomedical applications.

A Novel Approach against Salmonella: A Review of Polymeric Nanoparticle Vaccines for Broilers and Layers

This work discusses the present-day limitations of current commercial Salmonella vaccines for broilers and layers and explores a novel approach towards poultry vaccination using biodegradable nanoparticle vaccines against Salmonella. With the increasing global population and poultry production and consumption, Salmonella is a potential health risk for humans. The oral administration of killed or inactivated vaccines would provide a better alternative to the currently commercially available Salmonella vaccines for poultry. However, there are currently no commercial oral killed-vaccines against Salmonella for use in broilers or layers. There is a need for novel and effective interventions in the poultry industry. Polymeric nanoparticles could give way to an effective mass-administered mucosal vaccination method for Salmonella. The scope of this work is limited to polymeric nanoparticles against Salmonella for use in broilers and layers. This review is based on the information available at the time of the investigation.

Charged Poly(N-isopropylacrylamide) Nanogels for the Stabilization of High Isoelectric Point Proteins

Storage and transportation of protein therapeutics using refrigeration is a costly process; a reliable electrical supply is vital, expensive equipment is needed, and unique transportation is required. Reducing the reliance on the cold chain would enable low-cost transportation and storage of biologics, ultimately improving accessibility of this class of therapeutics to patients in remote locations. Herein, we report on the synthesis of charged poly(N-isopropylacrylamide) nanogels that efficiently adsorb a range of different proteins of varying isoelectric points and molecular weights (e.g., adsorption capacity (Q) = 4.7 ± 0.2 mg/mg at 6 mg/mL initial IgG concentration), provide protection from external environmental factors (i.e., temperature), and subsequently release the proteins in an efficient manner (e.g., 100 ± 1% at 2 mg/mL initial IgG concentration). Both cationic and anionic nanogels were synthesized and selectively chosen based on the ability to form electrostatic interactions with adsorbed proteins (e.g., cationic nanogels adsorb low isoelectric point proteins whereas anionic nanogels adsorb high isoelectric point proteins). The nanogel-protein complex formed upon adsorption increases the stabilization of the protein's tertiary structure, providing protection against denaturation at elevated temperatures (e.g., 84 ± 4% of the protected IgG was stabilized when exposed to 65 °C). The addition of a high molar salt solution (e.g., 40 mM CaCl₂ solution) to protein-laden nanogels disrupts the electrostatic interactions and collapses the nanogel, ultimately releasing the protein. The versatile materials utilized, in addition to the protein loading and release mechanisms described, provide a simple and efficient strategy to protect fragile biologics for their transport to remote areas without necessitating costly storage equipment.

Low doses of zeolitic imidazolate framework-8 nanoparticles alter the actin organization and contractility of vascular smooth muscle cells

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles have emerged as a promising platform for drug delivery and controlled release. Considering most ZIF-8 nanoparticle drug carriers are designed to be administered intravenously, and thus would directly contact vascular smooth muscle cells (VSMCs) in many circumstances, the potential interactions of ZIF-8 nanoparticles with VSMCs require investigation. Here, the effects of low doses of ZIF-8 nanoparticles on VSMC morphology, actin organization, and contractility are investigated. Two nanoscale imaging tools, atomic force microscopy, and direct stochastic optical reconstruction microscopy, show that even at the concentrations (12.5 and 25 µg/ml) that were deemed "safe" by conventional biochemical cell assays (MTT and LDH assays), ZIF-8 nanoparticles can still cause changes in cell morphology and actin cytoskeleton organization at the cell apical and basal surfaces. These cytoskeletal structural changes impair the contractility function of VSMCs in response to Angiotensin II, a classic vasoconstrictor. Based on intracellular zinc and actin polymerization assays, we conclude that the increased intracellular Zn²⁺ concentration due to the uptake and dissociation of ZIF-8 nanoparticles could cause the actin cytoskeleton dis-organization, as the elevated Zn²⁺ directly disrupts the actin assembly process, leading to altered actin organization such as branches and networks. Since the VSMC phenotype change and loss of contractility are fundamental to the development of atherosclerosis and related cardiovascular diseases, it is worth noting that these low doses of ZIF-8 nanoparticles administered intravenously could still be a safety concern in terms of cardiovascular risks. Moving forward, it is imperative to re-consider the "safe" nanoparticle dosages determined by biochemical cell assays alone, and take into account the impact of these nanoparticles on the biophysical characteristics of VSMCs, including changes in the actin cytoskeleton and cell morphology.

Biomaterials and nanomaterials for sustained release vaccine delivery

Vaccines are considered one of the most significant medical advancements in human history, as they have prevented hundreds of millions of deaths since their discovery; however, modern travel permits disease spread at unprecedented rates, and vaccine shortcomings like thermal sensitivity and required booster shots have been made evident by the COVID-19 pandemic. Approaches to overcoming these issues appear promising via the integration of vaccine technology with biomaterials, which offer sustained-release properties and preserve proteins, prevent conformational changes, and enable storage at room temperature. Sustained release and thermal stabilization of therapeutic biomacromolecules is an emerging area that integrates material science, chemistry, immunology, nanotechnology, and pathology to investigate different biocompatible materials. Biomaterials, including natural sugar polymers, synthetic polyesters produced from biologically derived monomers, hydrogel blends, protein-polymer blends, and metal-organic frameworks, have emerged as early players in the field. This overview will focus on significant advances of sustained release biomaterial in the context of vaccines against infectious disease and the progress made towards thermally stable "single-shot" formulations. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Stabilization of surface-bound antibodies for ELISA based on a reversable zeolitic imidazolate framework-8 coating

Immunoassays typically must be stored under refrigerated conditions because antibodies, after being immobilized to solid surfaces, tend to lose their recognition capabilities to target antigens under non-refrigerated conditions. This requirement hinders application of immunoassays in resource-limited settings including rural clinics in tropical regions, disaster struck areas, and low-income countries, where refrigeration may not be feasible. In this work, a facile approach based on a reversable zeolitic imidazolate framework-8 (ZIF-8) coating is introduced to stabilize surface-bound antibodies on enzyme-linked immunosorbent assay (ELISA) plates under non-refrigerated conditions. Using a sandwich ELISA for the detection of neutrophil gelatinase-associated lipocalin (NGAL), a urine biomarker for acute kidney injury, as a model system, ZIF-8 is demonstrated to be able to uniformly coat the surface-bound anti-NGAL IgG, and stabilize the dynamic range and detection sensitivity of the assay after storage at an elevated temperature (50 °C) for at least 4 weeks. The stabilization efficacy of the ZIF-8 coating is comparable to the current "gold standard" refrigeration approach, and superior to the commonly used sucrose coating method. This approach will greatly improve the shelf-life and stability of antibody-coated ELISAs and other types of assays which utilize surface-bound antibodies, thus extending biomedical research and medical diagnostics to resource-limited settings.

Self-Assembled, Dilution-Responsive Hydrogels for Enhanced Thermal Stability of Insulin Biopharmaceuticals

Biotherapeutics currently dominate the landscape of new drugs because of their exceptional potency and selectivity. Yet, the intricate molecular structures that give rise to these beneficial qualities also render them unstable in formulation. Hydrogels have shown potential as stabilizing excipients for biotherapeutic drugs, providing protection against harsh thermal conditions experienced during distribution and storage. In this work, we report the utilization of a cellulose-based supramolecular hydrogel formed from polymer–nanoparticle (PNP) interactions to encapsulate and stabilize insulin, an important biotherapeutic used widely to treat diabetes. Encapsulation of insulin in these hydrogels prevents insulin aggregation and maintains insulin bioactivity through stressed aging conditions of elevated temperature and continuous agitation for over 28 days. Further, insulin can be easily recovered by dilution of these hydrogels for administration at the point of care. This supramolecular hydrogel system shows promise as a stabilizing excipient to reduce the cold chain dependence of insulin and other biotherapeutics.

Current Status of Alginate in Drug Delivery

Alginate is one of the natural polymers that are often used in drug- and protein-delivery systems. The use of alginate can provide several advantages including ease of preparation, biocompatibility, biodegradability, and nontoxicity. It can be applied to various routes of drug administration including targeted or localized drug-delivery systems. The development of alginates as a selected polymer in various delivery systems can be adjusted depending on the challenges that must be overcome by drug or proteins or the system itself. The increased effectiveness and safety of sodium alginate in the drug- or protein-delivery system are evidenced by changing the physicochemical characteristics of the drug or proteins. In this review, various routes of alginate-based drug or protein delivery, the effectivity of alginate in the stem cells, and cell encapsulation have been discussed. The recent advances in the in vivo alginate-based drug-delivery systems as well as their toxicities have also been reviewed.

Site-Specific, Stoichiometric-Controlled, PEGylated Conjugates of Fibroblast Growth Factor 2 (FGF2) with Hydrophilic Auristatin Y for Highly Selective Killing of Cancer Cells Overproducing Fibroblast Growth Factor Receptor 1 (FGFR1)

In spite of significant progress in the field of targeted anticancer therapy, the FDA has approved only five ADC-based drugs. Hence the search for new targeted anticancer agents is an unfulfilled necessity. Here, we present novel types of protein–drug conjugates (PDCs) that exhibit superior anticancer activities. Instead of a monoclonal antibody, we used fibroblast growth factor 2 (FGF2) as a targeting molecule. FGF2 is a natural ligand of fibroblast growth factor receptor 1 (FGFR1), a transmembrane receptor overproduced in various types of cancers. We synthesized site-specific and stoichiometric-controlled conjugates of FGF2 with a highly potent, hydrophilic derivative of auristatin called auristatin Y. To increase the hydrophilicity and hydrodynamic radius of conjugates, we employed PEG4 and PEG27 molecules as a spacer between the targeting molecule and the cytotoxic payload. All conjugates were selective to FGFR1-positive cell lines, effectively internalized via the FGFR1-dependent pathway, and exhibited a highly cytotoxic effect only on FGFR1-positive cancer cell lines.

Supramolecular Encapsulation of Small-Ultrared Fluorescent Proteins in Virus-Like Nanoparticles for Noninvasive In Vivo Imaging Agents

Icosahedral virus-like particles (VLPs) derived from bacteriophages Qβ and PP7 encapsulating small-ultrared fluorescent protein (smURFP) were produced using a versatile supramolecular capsid disassemble-reassemble approach. The generated fluorescent VLPs display identical structural properties to their nonfluorescent analogs. Encapsulated smURFP shows indistinguishable photochemical properties to its unencapsulated counterpart, exhibits outstanding stability toward pH, and produces bright in vitro images following phagocytosis by macrophages. In vivo imaging allows the biodistribution to be imaged at different time points. Ex vivo imaging of intravenously administered encapsulated smURFP reveals a localization in the liver and kidneys after 2 h blood circulation and substantial elimination after 16 h of imaging, highlighting the potential application of these constructs as noninvasive in vivo imaging agents.

Using FRET to measure the time it takes for a cell to destroy a virus

The emergence of viral nanotechnology over the preceding two decades has created a number of intellectually captivating possible translational applications; however, the in vitro fate of the viral nanoparticles in cells remains an open question. Herein, we investigate the stability and lifetime of virus-like particle (VLP) Qβ-a representative and popular VLP for several applications-following cellular uptake. By exploiting the available functional handles on the viral surface, we have orthogonally installed the known FRET pair, FITC and Rhodamine B, to gain insight of the particle's behavior in vitro. Based on these data, we believe VLPs undergo aggregation in addition to the anticipated proteolysis within a few hours of cellular uptake.

Protein-polymer bioconjugates via a versatile oxygen tolerant photoinduced controlled radical polymerization approach

The immense application potential of amphiphilic protein-polymer conjugates remains largely unexplored, as established "grafting from" synthetic protocols involve time-consuming, harsh and disruptive deoxygenation methods, while "grafting to" approaches result in low yields. Here we report an oxygen tolerant, photoinduced CRP approach which readily affords quantitative yields of protein-polymer conjugates within 2 h, avoiding damage to the secondary structure of the protein and providing easily accessible means to produce biomacromolecular assemblies. Importantly, our methodology is compatible with multiple proteins (e.g. BSA, HSA, GOx, beta-galactosidase) and monomer classes including acrylates, methacrylates, styrenics and acrylamides. The polymerizations are conveniently conducted in plastic syringes and in the absence of any additives or external deoxygenation procedures using low-organic content media and ppm levels of copper. The robustness of the protocol is further exemplified by its implementation under UV, blue light or even sunlight irradiation as well as in buffer, nanopure, tap or even sea water.

ZIF-8 Degrades in Cell Media, Serum, and Some-But Not All-Common Laboratory Buffers

The emergence of drug delivery using water stable metal-organic frameworks has elicited a lot of interest in their biocompatibility. However, few studies have been conducted on their stability in common buffers, cell media, and blood proteins. For these studies, single crystal ZIF-8 approximately 1 um in diameter were synthesized, incubated with common laboratory buffers, cell media, and serum, and then characterized by PXRD, IR, DLS, and SEM. Time-resolved SEM and PXRD demonstrate that buffers containing phosphate and bicarbonate alter the appearance and composition of ZIF-8; however, cargo inside the ZIF-8 does not appear to leak out, in most of these buffers, even when the ZIF-8 itself is displaced by phosphates. On the other hand, blood proteins in serum dissolve ZIF-8, causing trapped biomolecules to escape. The study presented here suggests that ZIF-8 can undergo dramatic surface chemistry changes that may affect the interpretation of cellular uptake and cargo release data. On the other hand, it provides a rational explanation as to how ZIF-8 neatly dissolves in vivo.

Enhanced Stability and Controlled Delivery of MOF-Encapsulated Vaccines and Their Immunogenic Response In Vivo

Vaccines have an innate tendency to lose their structural conformation upon environmental and chemical stressors. A loss in conformation reduces the therapeutic ability to prevent the spread of a pathogen. Herein, we report an in-depth study of zeolitic imidazolate framework-8 and its ability to provide protection for a model viral vector against denaturing conditions. The immunoassay and spectroscopy analysis together demonstrate enhanced thermal and chemical stability to the conformational structure of the encapsulated viral nanoparticle. The long-term biological activity of this virus-ZIF composite was investigated in animal models to further elucidate the integrity of the encapsulated virus, the biosafety, and immunogenicity of the overall composite. Additionally, histological analysis found no observable tissue damage in the skin or vital organs in mice, following multiple subcutaneous administrations. This study shows that ZIF-based protein composites are strong candidates for improved preservation of proteinaceous drugs, are biocompatible, and are capable of controlling the release and adsorption of drugs in vivo.