Trehalose Glycopolymer Enhances Both Solution Stability and Pharmacokinetics of a Therapeutic Protein

Di-PEGylated insulin: A long-acting insulin conjugate with superior safety in reducing hypoglycemic events

Although the discovery of insulin 100 years ago revolutionized the treatment of diabetes, its therapeutic potential is compromised by its short half-life and narrow therapeutic index. Current long-acting insulin analogs, such as insulin-polymer conjugates, are mainly used to improve pharmacokinetics by reducing renal clearance. However, these conjugates are synthesized without sacrificing the bioactivity of insulin, thus retaining the narrow therapeutic index of native insulin, and exceeding the efficacious dose still leads to hypoglycemia. Here, we report a kind of di-PEGylated insulin that can simultaneously reduce renal clearance and receptor-mediated clearance. By impairing the binding affinity to the receptor and the activation of the receptor, di-PEGylated insulin not only further prolongs the half-life of insulin compared to classical mono-PEGylated insulin but most importantly, increases its maximum tolerated dose 10-fold. The target of long-term glycemic management in vivo has been achieved through improved pharmacokinetics and a high dose. This work represents an essential step towards long-acting insulin medication with superior safety in reducing hypoglycemic events.

Uniform trehalose nanogels for glucagon stabilization

Glucagon is a peptide hormone that acts via receptor-mediated signaling predominantly in the liver to raise glucose levels by hepatic glycogen breakdown or conversion of noncarbohydrate, 3 carbon precursors to glucose by gluconeogenesis. Glucagon is administered to reverse severe hypoglycemia, a clinical complication associated with type 1 diabetes. However, due to low stability and solubility at neutral pH, there are limitations in the current formulations of glucagon. Trehalose methacrylate-based nanoparticles were utilized as the stabilizing and solubilizing moiety in the system reported herein. Glucagon was site-selectively modified to contain a cysteine at amino acid number 24 to covalently attach to the methacrylate-based polymer containing pyridyl disulfide side chains. PEG2000 dithiol was employed as the crosslinker to form uniform nanoparticles. Glucagon nanogels were monitored in Dulbecco's phosphate-buffered saline (DPBS) pH 7.4 at various temperatures to determine its long-term stability in solution. Glucagon nanogels were stable up to at least 5 months by size uniformity when stored at -20 °C and 4 °C, up to 5 days at 25 °C, and less than 12 hours at 37 °C. When glucagon stability was studied by either HPLC or thioflavin T assays, the glucagon was intact for at least 5 months at -20 °C and 4 °C within the nanoparticles at -20 °C and 4 °C and up to 2 days at 25 °C. Additionally, the glucagon nanogels were studied for toxicity and efficacy using various assays in vitro. The findings indicate that the nanogels were nontoxic to fibroblast cells and nonhemolytic to red blood cells. The glucagon in the nanogels was as active as glucagon alone. These results demonstrate the utility of trehalose nanogels towards a glucagon formulation with improved stability and solubility in aqueous solutions, particularly useful for storage at cold temperatures.

Mass spectrometry of polymers: A tutorial review

Ever since the inception of synthetic polymeric materials in the late 19th century, the number of studies on polymers as well as the complexity of their structures have only increased. The development and commercialization of new polymers with properties fine-tuned for specific technological, environmental, consumer, or biomedical applications requires powerful analytical techniques that permit the in-depth characterization of these materials. One such method with the ability to provide chemical composition and structure information with high sensitivity, selectivity, specificity, and speed is mass spectrometry (MS). This tutorial review presents and exemplifies the various MS techniques available for the elucidation of specific structural features in a synthetic polymer, including compositional complexity, primary structure, architecture, topology, and surface properties. Key to every MS analysis is sample conversion to gas-phase ions. This review describes the fundamentals of the most suitable ionization methods for synthetic materials and provides relevant sample preparation protocols. Most importantly, structural characterizations via one-step as well as hyphenated or multidimensional approaches are introduced and demonstrated with specific applications, including surface sensitive and imaging techniques. The aim of this tutorial review is to illustrate the capabilities of MS for the characterization of large, complex polymers and emphasize its potential as a powerful compositional and structural elucidation tool in polymer chemistry.

Elucidating the Role of Optical Activity of Polymers in Protein-Polymer Interactions

Proteins are biomolecules with potential applications in agriculture, food sciences, pharmaceutics, biotechnology, and drug delivery. Interactions of hydrophilic and biocompatible polymers with proteins may impart proteolytic stability, improving the therapeutic effects of biomolecules and also acting as excipients for the prolonged storage of proteins under harsh conditions. The interactions of hydrophilic and stealth polymers such as poly(ethylene glycol), poly(trehalose), and zwitterionic polymers with various proteins are well studied. This study evaluates the molecular interactions of hydrophilic and optically active poly(vitamin B5 analogous methacrylamide) (poly(B5AMA)) with model proteins by fluorescence spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and circular dichroism (CD) spectroscopy analysis. The optically active hydrophilic polymers prepared using chiral monomers of R-(+)- and S-(-)-B5AMA by the photo-iniferter reversible addition fragmentation chain transfer (RAFT) polymerization showed concentration-dependent weak interactions of the polymers with bovine serum albumin and lysozyme proteins. Poly(B5AMA) also exhibited a concentration-dependent protein stabilizing effect at elevated temperatures, and no effect of the stereoisomers of polymers on protein thermal stability was observed. NMR analysis, however, showed poly(B5AMA) stereoisomer-dependent changes in the secondary structure of proteins.

Molecular Insights into the Improved Bioactivity of Interferon Conjugates Attached to a Helical Polyglutamate

Attaching polymers, especially polyethylene glycol (PEG), to protein drugs has emerged as a successful strategy to prolong circulation time in the bloodstream. The hypothesis is that the flexible chain wobbles on the protein's surface, thus resisting potential nonspecific adsorption. Such a theoretical framework may be challenged when a helical polyglutamate is used to conjugate with target proteins. In this study, we investigated the structure-activity relationships of polyglutamate-interferon conjugates P(EG₃Glu)-IFN using molecular simulations. Our results show that the local crowding effect induced by oligoethylene glycols (i.e., EG₃) is the primary driving force for helix formation in P(EG₃Glu), and its helicity can be effectively increased by reducing the free volume of the two termini. Furthermore, it was found that the steric hindrance induced by IFN is not conductive to the helicity of P(EG₃Glu) but contributes to its dominant orientation relative to interferon. The orientation of IFN relative to the helical P(EG₃Glu) can help to protect the protein drug from neutralizing antibodies while maintaining its bioactivity. These findings suggest that the helical structure and its orientation are critical factors to consider when updating the theoretical framework for protein-polymer conjugates.

Active-targeting long-acting protein-glycopolymer conjugates for selective cancer therapy

Non-fouling polymers are effective in improving the pharmacokinetics of therapeutic proteins, but short of biological functions for tumor targeting. In contrast, glycopolymers are biologically active, but usually have poor pharmacokinetics. To address this dilemma, herein we report in situ growth of glucose- and oligo(ethylene glycol)-containing copolymers at the C-terminal site of interferon alpha, an antitumor and antivirus biological drug, to generate C-terminal interferon alpha-glycopolymer conjugates with tunable glucose contents. The in vitro activity and in vivo circulatory half-life of these conjugates were found to decrease with the increase of glucose content, which can be ascribed to complement activation by the glycopolymers. Additionally, the cancer cell endocytosis of the conjugates was observed to maximize at a critical glucose content due to the tradeoff between complement activation and glucose transporter recognition by the glycopolymers. As a result, in mice bearing ovarian cancers with overexpressed glucose transporter 1, the conjugates with optimized glucose contents were identified to possess improved cancer-targeting ability, enhanced anticancer immunity and efficacy, and increased animal survival rate. These findings provided a promising strategy for screening protein-glycopolymer conjugates with optimized glucose contents for selective cancer therapy.

Deep Eutectic Solvents for Subcutaneous Delivery of Protein Therapeutics

Proteins are among the most common therapeutics for the treatment of diabetes, autoimmune diseases, cancer, and metabolic diseases, among others. Despite their common use, current protein therapies, most of which are injectables, have several limitations. Large proteins such as monoclonal antibodies (mAbs) suffer from poor absorption after subcutaneous injections, thus forcing their administration by intravenous injections. Even small proteins such as insulin suffer from slow pharmacokinetics which poses limitations in effective management of diabetes. Here, a deep eutectic-based delivery strategy is used to offer a generalized approach for improving protein absorption after subcutaneous injections. The lead formulation enhances absorption of mAbs after subcutaneous injections by ≈200%. The same composition also improves systemic absorption of subcutaneously injected insulin faster than Humalog, the current gold-standard of rapid acting insulin. Mechanistic studies reveal that the beneficial effect of deep eutectics on subcutaneous absorption is mediated by their ability to reduce the interactions of proteins with the subcutaneous matrix, especially collagen. Studies also confirm that these deep eutectics are safe for subcutaneous injections. Deep eutectic-based formulations described here open new possibilities for subcutaneous injections of therapeutic proteins.

Long-Acting Insulin-Zwitterionic Polymer Conjugate Mitigates Hypoglycemia

Insulin, a main medication to control glycemia of type 1 and advanced type 2 diabetes, faces problems of a short half-life and poor stability during its clinical use. Zwitterionic polymer shows unique properties of antifouling and low immunogenicity. Here, we have synthesized a new insulin-zwitterionic polymer conjugate (INS-PMPC) through grafting-from strategy by controlled radical polymerization. Apart from showing excellent stability upon mechanical agitation, the resulting INS-PMPC conjugate provided over 20 h of glycemic control due to improved pharmacokinetics in diabetic mice with one single subcutaneous injection. Most importantly, this insulin-zwitterionic polymer conjugate significantly decreases the incidence of hypoglycemia.

A Review of Protein- and Peptide-Based Chemical Conjugates: Past, Present, and Future

Over the past few decades, the complexity of molecular entities being advanced for therapeutic purposes has continued to evolve. A main propellent fueling innovation is the perpetual mandate within the pharmaceutical industry to meet the needs of novel disease areas and/or delivery challenges. As new mechanisms of action are uncovered, and as our understanding of existing mechanisms grows, the properties that are required and/or leveraged to enable therapeutic development continue to expand. One rapidly evolving area of interest is that of chemically enhanced peptide and protein therapeutics. While a variety of conjugate molecules such as antibody-drug conjugates, peptide/protein-PEG conjugates, and protein conjugate vaccines are already well established, others, such as antibody-oligonucleotide conjugates and peptide/protein conjugates using non-PEG polymers, are newer to clinical development. This review will evaluate the current development landscape of protein-based chemical conjugates with special attention to considerations such as modulation of pharmacokinetics, safety/tolerability, and entry into difficult to access targets, as well as bioavailability. Furthermore, for the purpose of this review, the types of molecules discussed are divided into two categories: (1) therapeutics that are enhanced by protein or peptide bioconjugation, and (2) protein and peptide therapeutics that require chemical modifications. Overall, the breadth of novel peptide- or protein-based therapeutics moving through the pipeline each year supports a path forward for the pursuit of even more complex therapeutic strategies.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Alternative Excipients for Protein Stabilization in Protein Therapeutics: Overcoming the Limitations of Polysorbates

Given their safety and efficiency in protecting protein integrity, polysorbates (PSs) have been the most widely used excipients for the stabilization of protein therapeutics for years. In recent decades, however, there have been numerous reports about visible or sub-visible particles in PS-containing biotherapeutic products, which is a major quality concern for parenteral drugs. Alternative excipients that are safe for parenteral administration, efficient in protecting different protein drugs against various stress conditions, effective in protein stabilization in high-concentrated liquid formulations, stable under the storage conditions for the duration of the product's shelf-life, and compatible with other formulation components and the primary packaging are highly sought after. The aim of this paper is to review potential alternative excipients from different families, including surfactants, carbohydrate- and amino acid-based excipients, synthetic amphiphilic polymers, and ionic liquids that enable protein stabilization. For each category, important characteristics such as the ability to stabilize proteins against thermal and mechanical stresses, current knowledge related to the safety profile for parenteral administration, potential interactions with other formulation components, and primary packaging are debated. Based on the provided information and the detailed discussion thereof, this paper may pave the way for the identification or development of efficient excipients for biotherapeutic protein stabilization.

Trehalose and its applications in the food industry

Trehalose is a nonreducing disaccharide composed of two glucose molecules linked by α, α-1,1-glycosidic bond. It is present in a wide variety of organisms, including bacteria, fungi, insects, plants, and invertebrate animals. Trehalose has distinct physical and chemical properties that have been investigated for their biological importance in a range of prokaryotic and eukaryotic species. Emerging research on trehalose has identified untapped opportunities for its application in the food, medical, pharmaceutical, and cosmetics industries. This review summarizes the chemical and biological properties of trehalose, its occurrence and metabolism in living organisms, its protective role in molecule stabilization, and natural and commercial production methods. Utilization of trehalose in the food industry, in particular how it stabilizes protein, fat, carbohydrate, and volatile compounds, is also discussed in depth. Challenges and opportunities of its application in specific applications (e.g., diagnostics, bioprocessing, ingredient technology) are described. We conclude with a discussion on the potential of leveraging the unique molecular properties of trehalose in molecular stabilization for improving the safety, quality, and sustainability of our food systems.

Formulation, Characterisation and Evaluation of the Antihypertensive Peptides, Isoleucine-Proline-Proline and Leucine-Lysine-Proline in Chitosan Nanoparticles Coated with Zein for Oral Drug Delivery

Isoleucine-Proline-Proline (IPP) and Leucine-Lysine-Proline (LKP) are food-derived tripeptides whose antihypertensive functions have been demonstrated in hypertensive rat models. However, peptides display low oral bioavailability due to poor intestinal epithelial permeability and instability. IPP and LKP were formulated into nanoparticles (NP) using chitosan (CL113) via ionotropic gelation and then coated with zein. Following addition of zein, a high encapsulation efficiency (EE) (>80%) was obtained for the NP. In simulated gastric fluid (SGF), 20% cumulative release of the peptides was achieved after 2 h, whereas in simulated intestinal fluid (SIF), ~90% cumulative release was observed after 6 h. Higher colloidal stability (39−41 mV) was observed for the coated NP compared to uncoated ones (30−35 mV). In vitro cytotoxicity studies showed no reduction in cellular viability of human intestinal epithelial Caco-2 and HepG2 liver cells upon exposure to NP and NP components. Administration of NP encapsulating IPP and LKP by oral gavage to spontaneously hypertensive rats (SHR) attenuated systolic blood pressure (SBP) for 8 h. This suggests that the NP provide appropriate release to achieve prolonged hypotensive effects in vivo. In conclusion, chitosan-zein nanoparticles (CZ NP) have potential as oral delivery system for the encapsulation of IPP and LKP.

Rapid Oxygen-Tolerant Synthesis of Protein-Polymer Bioconjugates via Aqueous Copper-Mediated Polymerization

The synthesis of protein-polymer conjugates usually requires extensive and costly deoxygenation procedures, thus limiting their availability and potential applications. In this work, we report the ultrafast synthesis of polymer-protein bioconjugates in the absence of any external deoxygenation via an aqueous copper-mediated methodology. Within 10 min and in the absence of any external stimulus such as light (which may limit the monomer scope and/or disrupt the secondary structure of the protein), a range of hydrophobic and hydrophilic monomers could be successfully grafted from a BSA macroinitiator, yielding well-defined polymer-protein bioconjugates at quantitative yields. Our approach is compatible with a wide range of monomer classes such as (meth) acrylates, styrene, and acrylamides as well as multiple macroinitiators including BSA, BSA nanoparticles, and beta-galactosidase from Aspergillus oryzae. Notably, the synthesis of challenging protein-polymer-polymer triblock copolymers was also demonstrated, thus significantly expanding the scope of our strategy. Importantly, both lower and higher scale polymerizations (from 0.2 to 35 mL) were possible without compromising the overall efficiency and the final yields. This simple methodology paves the way for a plethora of applications in aqueous solutions without the need of external stimuli or tedious deoxygenation.

Poly(trehalose methacrylate) as an Excipient for Insulin Stabilization: Mechanism and Safety

Insulin, the oldest U.S. Food and Drug Administration (FDA)-approved recombinant protein and a World Health Organization (WHO) essential medicine for treating diabetes globally, faces challenges due to its storage instability. One approach to stabilize insulin is the addition of poly(trehalose methacrylate) (pTrMA) as an excipient. The polymer increases the stability of the peptide to heat and mechanical agitation and has a low viscosity suitable for injection and pumps. However, the safety and stabilizing mechanism of pTrMA is not yet known and is required to understand the potential suitability of pTrMA as an insulin excipient. Herein is reported the immune response, biodistribution, and insulin plasma lifetime in mice, as well as investigation into insulin stabilization. pTrMA alone or formulated with ovalbumin did not elicit an antibody response over 3 weeks in mice, and there was no observable cytokine production in response to pTrMA. Micropositron emission tomography/microcomputer tomography of ⁶⁴Cu-labeled pTrMA showed excretion of 78-79% ID/cc within 24 h and minimal liver accumulation at 6-8% ID/cc when studied out to 120 h. Further, the plasma lifetime of insulin in mice was not altered by added pTrMA. Formulating insulin with 2 mol equiv of pTrMA improved the stability of insulin to standard storage conditions: 46 weeks at 4 °C yielded 87.0% intact insulin with pTrMA present as compared to 7.8% intact insulin without the polymer. The mechanism by which pTrMA-stabilized insulin was revealed to be a combination of inhibiting deamidation of amino acid residues and preventing fibrillation, followed by aggregation of inactive and immunogenic amyloids all without complexing insulin into its hexameric state, which could delay the onset of insulin activity. Based on the data reported here, we suggest that pTrMA stabilizes insulin as an excipient without adverse effects in vivo and is promising to investigate further for the safe formulation of insulin.

Sulfoxide-Containing Polyacrylamides Prepared by PICAR ATRP for Biohybrid Materials

Water-soluble and biocompatible polymers are of interest in biomedicine as the search for alternatives to PEG-based materials becomes more important. In this work, the synthesis of a new sulfoxide-containing monomer, 2-(methylsulfinyl)ethyl acrylamide (MSEAM), is reported. Well-defined polymers were prepared by photoinduced initiators for continuous activator regeneration atom transfer radical polymerization (PICAR ATRP). The polymerizations were performed in water under biologically relevant conditions in a small volume without degassing the reaction mixture. DNA-PMSEAM and protein-PMSEAM hybrids were also synthesized. The lower critical solution temperature (LCST) of PMSEAM was estimated to be approximately 170 °C by extrapolating the LCST for a series of copolymers with variable content of N-isopropylacrylamide. The cytotoxicity studies showed excellent biocompatibility of PMSEAM, even at concentrations up to 2.5 mg/mL. Furthermore, the MSEAM monomer exhibited relatively lower toxicity than similar (meth)acrylate-based monomers at comparable concentrations.

Safety and Biodistribution Profile of Poly(styrenyl acetal trehalose) and Its Granulocyte Colony Stimulating Factor Conjugate

Poly(styrenyl acetal trehalose) (pSAT), composed of trehalose side chains linked to a polystyrene backbone via acetals, stabilizes a variety of proteins and enzymes against fluctuations in temperature. A promising application of pSAT is conjugation of the polymer to therapeutic proteins to reduce renal clearance. To explore this possibility, the safety of the polymer was first studied. Investigation of acute toxicity of pSAT in mice showed that there were no adverse effects of the polymer at a high (10 mg/kg) concentration. The immune response (antipolymer antibody and cytokine production) in mice was also studied. No significant antipolymer IgG was detected for pSAT, and only a transient and low level of IgM was elicited. pSAT was also safe in terms of cytokine response. The polymer was then conjugated to a granulocyte colony stimulating factor (GCSF), a therapeutic protein that is approved by the Federal Drug Administration, in order to study the biodistribution of a pSAT conjugate. A site-selective, two-step synthesis approach was developed for efficient conjugate preparation for the biodistribution study resulting in 90% conjugation efficiency. The organ distribution of GCSF-pSAT was measured by positron emission tomography and compared to controls GCSF and GCSF-poly(ethylene glycol), which confirmed that the trehalose polymer conjugate improved the in vivo half-life of the protein by reducing renal clearance. These findings suggest that trehalose styrenyl polymers are promising for use in therapeutic protein-polymer conjugates for reduced renal clearance of the biomolecule.

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.

Synthesis and Application of Trehalose Materials

Trehalose is a naturally occurring, nonreducing disaccharide that is widely used in the biopharmaceutical, food, and cosmetic industries due to its stabilizing and cryoprotective properties. Over the years, scientists have developed methodologies to synthesize linear polymers with trehalose units either in the polymer backbone or as pendant groups. These macromolecules provide unique properties and characteristics, which often outperform trehalose itself. Additionally, numerous reports have focused on the synthesis and formulation of materials based on trehalose, such as nanoparticles, hydrogels, and thermoset networks. Among many applications, these polymers and materials have been used as protein stabilizers, as gene delivery systems, and to prevent amyloid aggregate formation. In this Perspective, recent developments in the synthesis and application of trehalose-based linear polymers, hydrogels, and nanomaterials are discussed, with a focus on utilization in the biomedical field.

Trehalose-releasing nanogels: A step toward a trehalose delivery vehicle for autophagy stimulation

Trehalose has been widely studied as a treatment for a variety of human disorders due to its ability to stimulate autophagy. Trehalose, however, is poorly adsorbed and is hydrolyzed in the intestinal mucosa, and oral delivery requires relatively high doses to induce autophagy. The parenteral injection of trehalose-releasing nanogels proposed in this study offers an alternative mode of delivery. This study aimed to develop stable colloidal dispersions of trehalose-rich nanogels that could sustainably release trehalose under physiologically relevant conditions. The nanogel design was based on the covalent incorporation of 6-O-acryloyl-trehalose within a polymer network. A series of nine trehalose-rich nanogels with highly conjugated trehalose (up to 59 % w/w) were synthesized and shown to sustainably release trehalose at a rate that is not dose dependent. The nanogels were optimized to keep colloidal stability in serum-enriched cell culture media. The stable nanogels were not cytotoxic to primary HUVECs. Two selected nanogels with opposite surface charges were subjected to extended in vitro characterization that included a cellular uptake study and a hemocompatibility assay. Both nanogels were efficiently taken up by HUVECs during a short incubation. They also proved not to be hemolytic to human RBCs in concentrations up to 2.0 mg/mL. Finally, an in vivo autophagy stimulation study employing transgenic zebrafish and Drosophila larvae demonstrated that prolonged exposure to a cationic trehalose-releasing nanogel can induce autophagic activity in in vivo systems without any detectable toxicity.

Self-Immolative Hydroxybenzylamine Linkers for Traceless Protein Modification

Traceless self-immolative linkers are widely used for the reversible modification of proteins and peptides. This article describes a new class of traceless linkers based on ortho- or para-hydroxybenzylamines. The introduction of electron-donating substituents on the aromatic core stabilizes the quinone methide intermediate, thus providing a platform for payload release that can be modulated. To determine the extent to which the electronics affect the rate of release, we prepared a small library of hydroxybenzylamine linkers with varied electronics in the aromatic core, resulting in half-lives ranging from 20 to 144 h. Optimization of the linker design was carried out with mechanistic insights from density functional theory (DFT) and the in silico design of an intramolecular trapping agent through the use of DFT and intramolecular distortion energy calculations. This resulted in the development of a faster self-immolative linker with a half-life of 4.6 h. To demonstrate their effectiveness as traceless linkers for bioconjugation, reversible protein-polyethylene glycol conjugates with a model protein lysozyme were prepared, which had reduced protein activity but recovered ≥94% activity upon traceless release of the polymer. This new class of linkers with tunable release rates expands the traceless linkers toolbox for a variety of bioconjugation applications.

Effect of Poly(trehalose methacrylate) Molecular Weight and Concentration on the Stability and Viscosity of Insulin

Instability to storage and shipping conditions and injection administration remain major challenges in treating chronic conditions with biopharmaceuticals. Herein, formulations of poly(trehalose methacrylate) (pTrMA) were successfully optimized to stabilize insulin without appreciably increasing viscosity. Polymers were synthesized (2,400 - 29,200 Da), and added to insulin at different concentrations. pTrMA maintained >95% intact insulin against 250 rpm at 37 °C for 3 hours with at least 10 mol. eq. of 5.0 kDa, 7.5 mol. eq. of 9.4 kDa, 5 mol. eq. of 12.8 kDa, 1 mol. eq. of 19.8 kDa, and 0.5 mol. eq. of 29.2 kDa polymers, compared to 13.1% of insulin alone. The lowest pTrMA concentration formulations were more viscous than insulin alone, but the highest viscosity, U-600 with 10 mol. eq. of 5 kDa pTrMA, was only 1.43 cP at 25 °C. This data demonstrates that pTrMA is a promising low viscosity additive to stabilize the diabetes therapeutic insulin.

Inhibition of S. aureus-Infection of HUVECs by Trehalose and Glucose-functionalized Gold Nanoparticles

Microbial adhesion to host cells represents the initial step in the infection process. Several methods have been explored to inhibit microbial adhesion including the use of glycopolymers based on mannose, galactose, sialic acid and glucose. These sugar receptors are however abundant in the body and they are not unique to bacteria. Trehalose in contrast is a unique disaccharide that is wildly expressed by microbes. This carbohydrate has not yet been explored as an anti-adhesive. Herein, gold nanoparticles (AuNPs) coated with trehalose-based polymers were prepared and compared to glucose-functionalized AuNPs and examined for their ability to prevent binding to endothelial cells. Acting as anti-adhesive, trehalose-functionalized nanoparticles decreased the binding of S. aureus to HUVEC cells, while outperforming the control nanoparticles. Microscopy revealed that trehalose coated nanoparticle bound strongly to S. aureus compared to the controls. In conclusion, nanoparticles based on trehalose could be a non-toxic alternative to inhibit S. aureus infection.

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 the fastest in middle- and low-income countries. The 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 °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.

An ultrafast insulin formulation enabled by high-throughput screening of engineered polymeric excipients

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.

Conformational stability as a quality attribute for the cell therapy raw material human serum albumin

Although human serum albumin (HSA) has been used for many decades, there is still a lack of suitable quality control (QC) attributes. Its current use as a raw material in gene-, cell- and tissue-therapies requires more appropriate functionally-relevant quality attributes and methods. This study investigated the conformational stability of serum albumin using circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) for evaluating the thermal sensitivity, and quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) for assessing the adsorption behavior. Different serum albumin samples were used, encompassing plasma-derived HSA (pHSA), recombinant octanoate-stabilized HSA (rHSA) and bovine serum albumin (BSA). The melting temperature (T _m) as well as the onset temperature (T _onset) were obtained from the derivative curves of the temperature gradient CD data at 222 nm. The results from DLS, as well as from real-time QCM-D and LSPR silica-adsorption kinetic profiles confirmed the relatively higher conformational stability of the octanoate (fatty acid) containing rHSA, while the additional negative charge resulted in a lower amount adsorbed to the silica surface compared to the non-stabilized HSA and BSA. Adsorption studies further revealed that BSA has a lower conformational stability and undergoes more extensive adsorption-induced spreading compared to the non-stabilized HSA. Collectively, the temperature-based (CD and DLS) as well as adsorption-based biosensor (QCM-D and LSPR) approaches gave congruent and discriminatory information about the conformational stability of different serum albumins, indicating that these techniques provide information on valuable QC attributes.

Synthesis of Disulfide-Bridging Trehalose Polymers for Antibody and Fab Conjugation Using a Bis-Sulfone ATRP Initiator

Antibodies and antigen binding fragments (FABs) are widely used as therapeutics and conjugated polymers can enhance the properties of these important biomolecules. However, limitations to the selectivity and stability of current conjugation methodologies can inhibit the exploration of new antibody-polymer conjugates. Herein, we describe a new strategy for the synthesis of these conjugates that forms a stable thioether bond and can be directly incorporated into an atom transfer radical polymerization (ATRP) initiator. Specifically, a bis-sulfone alkyl bromide initiator was synthesized and utilized in the activators generated by electron transfer (AGET) ATRP of ethylene glycol methacrylate and trehalose methacrylate to form the respective polymers. The trehalose polymer was then irreversibly inserted into the disulfide bonds of Herceptin and Herceptin FAB after mild reduction to form the conjugates with quantitative conversions as verified by Western Blot and mass spectrometry after cleavage of the polymer. The binding of the Herceptin and Herceptin Fab conjugates to the receptor was investigated by indirect ELISA (enzyme-linked immunosorbent assay) and the EC50's were 0.90 and 2.74 nM, respectively, compared to Herceptin (0.26 nM) and the Fab (0.56 nM). The conjugates were subjected to heating studies at a constant 75 °C, the temperature determined in a heat ramp to be the threshold of stability for the antibody and FAB; the trehalose polymer was found to considerably increase the thermal stability of both Herceptin and Herceptin Fab. This work provides a new way to prepare polymer-antibody/Fab conjugates utilizing bis-sulfone end groups installed by atom transfer radical polymerization of the functionalized initiators and a way to stabilize these important molecules by conjugation to trehalose polymers.

One-Step Protein-Polymer Conjugates from Boronic-Acid-Functionalized Polymers

Polymer-protein conjugates are hybrid materials with interesting and useful properties. Methods to prepare diverse diblock materials of this sort often struggle to deal with the complexity and size of reagents, and so polymer-protein conjugation represents a stringent testing ground for nontraditional bioconjugation methods, such as metal-catalyzed arylation. This work demonstrates a simple Ni²⁺-promoted arylation of cysteine residues with end-functionalized polymer-boronic acid reagents, and explores some molecular and physical properties possible in these hybrid structures.

Proteins Conjugated with Sulfoxide-Containing Polymers Show Reduced Macrophage Cellular Uptake and Improved Pharmacokinetics

The conjugation of hydrophilic polymers to proteins is an effective approach to prolonging their circulation time in the bloodstream and, hence, improving their delivery to the target region of interest. In this work, we report the synthesis of protein-polymer conjugates using a highly water-soluble sulfoxide-containing polymer, poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA), through a combination of "grafting-to" and "grafting-from" methods. Oligomeric MSEA was synthesized by conventional reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently conjugated to lysozyme to produce a macromolecular chain transfer agent. This was followed by a visible light-mediated chain extension polymerization of MSEA to obtain a lysozyme-PMSEA conjugate (Lyz-PMSEA). It was found that the Lyz-PMSEA conjugate exhibited much reduced macrophage cellular uptake compared with unmodified and PEGylated lysozyme. Moreover, the Lyz-PMSEA conjugate was able to circulate longer in the bloodstream, demonstrating significantly improved pharmacokinetics demanded for pharmaceutical applications.

Synthesis of Zwitterionic and Trehalose Polymers with Variable Degradation Rates and Stabilization of Insulin

Polymers that stabilize biomolecules are important as excipients in protein formulation. Herein, we describe a class of degradable polymers that have tunable degradation rates depending on the polymer backbone and can stabilize proteins to aggregation. Specifically, zwitterion- and trehalose-substituted polycaprolactone, polyvalerolactone, polycarbonate, and polylactide were prepared and characterized with regards to their hydrolytic degradation and ability to stabilize insulin to mechanical agitation during heat. Ring-opening polymerization (ROP) of allyl-substituted monomers was performed by using organocatalysis, resulting in well-defined alkene-substituted polymers with good control over molecular weight and dispersity. The polymers were then modified by using photocatalyzed thiol-ene reactions to install protein-stabilizing carboxybetaine and trehalose side chains. The resulting polymers were water-soluble and exhibited a wide range of half-lives, from 12 h to more than 3 months. The polymers maintained the ability to stabilize the therapeutic protein insulin from activity loss due to aggregation, demonstrating their potential as degradable excipients for protein formulation.

Nanosized Delivery Systems for Therapeutic Proteins: Clinically Validated Technologies and Advanced Development Strategies

The impact of protein therapeutics in healthcare is steadily increasing, due to advancements in the field of biotechnology and a deeper understanding of several pathologies. However, their safety and efficacy are often limited by instability, short half-life and immunogenicity. Nanodelivery systems are currently being investigated for overcoming these limitations and include covalent attachment of biocompatible polymers (PEG and other synthetic or naturally derived macromolecules) as well as protein nanoencapsulation in colloidal systems (liposomes and other lipid or polymeric nanocarriers). Such strategies have the potential to develop next-generation protein therapeutics. Herein, we review recent research progresses on these nanodelivery approaches, as well as future directions and challenges.

Trends in Therapeutic Conjugates: Bench to Clinic

In recent years, therapeutic conjugates have attracted considerable attention as a new class of drug due to their unique pharmacological properties, especially from the pharmaceutical community. Their molecular structure tunability, improved targeting specificity, and therapeutic efficacy have been demonstrated in a wide range of research and clinical applications. In this topical review, we summarize selected recent advances in bioconjugation strategies for the development of therapeutic conjugates, their emerging application in clinical settings, as well as perspectives on the direction of future research.

Functional zwitterionic biomaterials for administration of insulin

This review summarizes the structures and biomedical applications of zwitterionic biomaterials in the administration of insulin.

Parallel evolution of polymer chemistry and immunology: Integrating mechanistic biology with materials design

To develop new therapeutics involves the interaction of multiple disciplines to yield safe, functional devices and formulations. Regardless of drug function and potency, administration with controlled timing, dosing, and targeting is required to properly treat or regulate health and disease. Delivery approaches can be optimized through advances in materials science, clinical testing, and basic biology and immunology. Presently, laboratories focused on developing these technologies are composed of, or collaborate with, chemists, biologists, materials scientists, engineers, and physicians to understand the way our body interacts with drug delivery devices, and how to synthesize new, rationally designed materials to improve targeted and controlled drug delivery. In this review, we discuss both device-based and micro/nanoparticle-based materials in the clinic, our biologic understanding of how our immune system interacts with these materials, how this diverse set of immune cells has become a target and variable in drug delivery design, and new directions in polymer chemistry to address these interactions and further our advances in medical therapeutics.

More than a Confinement: “Soft” and “Hard” Enzyme Entrapment Modulates Biological Catalyst Function

Catalysis makes chemical and biochemical reactions kinetically accessible. From a technological point of view, organic, inorganic, and biochemical catalysis is relevant for several applications, from industrial synthesis to biomedical, material, and food sciences. A heterogeneous catalyst, i.e., a catalyst confined in a different phase with respect to the reagents’ phase, requires either its physical confinement in an immobilization matrix or its physical adsorption on a surface. In this review, we will focus on the immobilization of biological catalysts, i.e., enzymes, by comparing hard and soft immobilization matrices and their effect on the modulation of the catalysts’ function. Indeed, unlike smaller molecules, the catalytic activity of protein catalysts depends on their structure, conformation, local environment, and dynamics, properties that can be strongly affected by the immobilization matrices, which, therefore, not only provide physical confinement, but also modulate catalysis.

Thermal sensitivity as a quality control attribute for biotherapeutics: The L-asparaginase case

Thermal sensitivity, as a practical measure of thermostability, is an interesting quality attribute that can be used in the quality control (QC) release of biopharmaceuticals. This article investigates circular dichroism (CD) spectroscopy and nano-differential scanning fluorimetry (nano-DSF) to evaluate the thermal stability of E.coli L-asparaginase (L-ASNase) for QC purposes. In CD, molar ellipticity as a function of temperature (from 20 to 80°C) was measured at 222 nm. Different L-ASNase samples dissolved in different diluents were investigated by determining the melting temperature (T_m ) from the first derivative curve as well as the slope of the fitted sigmoidal function of the temperature gradient CD data. The obtained T_m values could be correlated with the L-ASNase sample origin as well as with the pH of the diluent. The T_m values obtained from the CD data were moreover consistent with the T_m values determined by nano-DSF, confirming their reliability. Next to the T_m value, also the slope of the fitted sigmoidal CD-function was able to differentiate different L-ASNase samples, including unstressed from stressed protein. By using both the T_m and the curve slope, the thermal stability of L-ASNase was investigated, demonstrating and recommending the use of this heat-stress characteristic as a QC quality attribute of proteins, which can be applied to detect substandard and falsified proteins.

Stimuli-Responsive Drug Release from Smart Polymers

Over the past 10 years, stimuli-responsive polymeric biomaterials have emerged as effective systems for the delivery of therapeutics. Persistent with ongoing efforts to minimize adverse effects, stimuli-responsive biomaterials are designed to release in response to either chemical, physical, or biological triggers. The stimuli-responsiveness of smart biomaterials may improve spatiotemporal specificity of release. The material design may be used to tailor smart polymers to release a drug when particular stimuli are present. Smart biomaterials may use internal or external stimuli as triggering mechanisms. Internal stimuli-responsive smart biomaterials include those that respond to specific enzymes or changes in microenvironment pH; external stimuli can consist of electromagnetic, light, or acoustic energy; with some smart biomaterials responding to multiple stimuli. This review looks at current and evolving stimuli-responsive polymeric biomaterials in their proposed applications.

Stabilization of enzyme-immobilized hydrogels for extended hypoxic cell culture

In this work, glucose oxidase (GOx)-immobilized hydrogels are developed and optimized as an easy and convenient means for creating solution hypoxia in a regular incubator. Specifically, acrylated GOx co-polymerizes with poly(ethylene glycol) diacrylate (PEGDA) to form PEGDA-GOx hydrogels. Results show that freeze-drying and reaction by-products, hydrogen peroxide, negatively affect oxygen-consuming activity of network-immobilized GOx. However, the negative effects of freeze-drying can be mitigated by addition of trehalose/raffinose in the hydrogel precursor solution, whereas the inhibition of GOx caused by hydrogen peroxide can be prevented via addition of glutathione (GSH) in the buffer/media. The ability to preserve enzyme activity following freeze-drying and during long-term incubation permits facile application of this material to induce long-term solution/media hypoxia in cell culture plasticware placed in a regular CO₂ incubator.

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.

Engineering Strategies for Oral Therapeutic Enzymes to Enhance Their Stability and Activity

Oral application of therapeutic enzymes is a promising and non-invasive administration that improves patient compliance. However, the gastrointestinal tract poses several challenges to the oral delivery of proteins, including harsh pH conditions and digestive proteases. A promising way to stabilise enzymes during their gastrointestinal route is by modification with polymers that can provide both steric shielding and selective interaction in different digestive compartments. We give an overview of modification technologies for oral enzymes ranging from functionalisation of native proteins, to site-specific mutation and protein-polymer engineering. We specifically focus on enzymes that are active directly in the gastrointestinal lumen and not systemically absorbed. In addition, we discuss examples of microparticle and nanoparticle encapsulated enzymes for improved oral delivery. The modification of orally administered enzymes offers a broad chemical variability and may be a promising tool for enhancing their gastrointestinal stability.

Determination of Optimum Excipients for Platanus orientalis Pollen Extract by Accelerating Chemical Stability Test and Their Synergistic Effect

BACKGROUND

The quality of extracts used in the skin prick test directly influences the interpretation of the test. Accordingly, the outcomes and effectiveness of immunotherapy for the management of IgE-mediated allergies depend on the quality of the extracts used. Excipients, which are pharmacologically inert ingredients, are intentionally added to the active ingredients. The aim of this study was to address optimum excipients for stability Platanus (P.) orientalis extract.

METHODS

In this study the excipients examined were l-lysine (20 mM), l-cysteine (20 mM), albumin (0.5%), sorbitol (2%), sucrose (750 mM), trehalose (20 mM), D-mannitol (2% w/v), urea (100 mM) and Tween-20 (0.1%). Their effects on P. orientalis extract stability were analyzed using an inhibition enzyme linked immune assay at 37 °C.

RESULTS

A mixture of lysine (20 mM), trehalose (20 mM), and D-mannitol (2% w/v) conferred the greatest stability on the P. orientalis extract.

CONCLUSION

The P. orientalis extract stability was increased by a mixture of lysine (20 mM), trehalose (20 mM), and D-mannitol.

A guide to maximizing the therapeutic potential of protein-polymer conjugates by rational design

Proteins are an important class of therapeutics that have advantages including high target specificity, but challenges to their use include rapid clearance and low physical stability. Conjugation of synthetic polymers is an effective approach to address the drawbacks and enhance other properties such as solubility. In this review, we present various considerations in synthesizing protein-polymer conjugates for therapeutic applications with a focus on the choice of polymer, protein, and conjugation method, as well as characterization and evaluation of the resulting conjugate in order to maximize the therapeutic potential of the protein drug.