Polyglycerol for Half-Life Extension of Proteins-Alternative to PEGylation?

Enhancing colloidal stability of nanodiamond via surface modification with dendritic molecules for optical sensing in physiological environments

Pre-treatment of diamond surface in low-temperature plasma for oxygenation and in acids for carboxylation was hypothesized to promote the branching density of the hyperbranched glycidol polymer. This was expected to increase the homogeneity of the branching level and suppress interactions with proteins. As a result, composite nanodiamonds with reduced hydrodynamic diameters that are maintained in physiological environments were anticipated. Surfaces of 140-nm-sized nanodiamonds were functionalized with oxygen and carboxyl groups for grafting of hyperbranched dendritic polyglycerol via anionic ring-opening polymerization of glycidol. The modification was verified with Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Dynamic light scattering investigated colloidal stability in pH-diverse (2-12) solutions, concentrated phosphate-buffered saline, and cell culture media. Thermogravimetric analysis of nanodiamonds-protein incubations examined non-specific binding. Fluorescence emission was tested across pH conditions. Molecular dynamics simulations modeled interparticle interactions in ionic solutions. The hyperbranched polyglycerol grafting increased colloidal stability of nanodiamonds across diverse pH, high ionic media like 10 × concentrated phosphate-buffered saline, and physiological media like serum and cell culture medium. The hyperbranched polyglycerol suppressed non-specific protein adsorption while maintaining intensive fluorescence of nanodiamonds regardless of pH. Molecular modelling indicated reduced interparticle interactions in ionic solutions correlating with the improved colloidal stability.

IL-1ra loaded chondroitin sulfate-functionalized microspheres for minimally invasive treatment of intervertebral disc degeneration

Presently, the clinical treatment of intervertebral disc degeneration (IVDD) remains challenging, but the strategy of simultaneously overcoming the overactive inflammation and restoring the anabolic/catabolic balance of the extracellular matrix (ECM) in the nucleus pulposus (NP) has become an effective way to alleviate IVDD. IL-1ra, a natural antagonist against IL-1β, can mitigate inflammation and promote regeneration in IVDD. Chondroitin sulfate (CS), an important component of the NP, can promote ECM synthesis and delay IVDD. Thus, these were chosen and integrated into functionalized microspheres to achieve their synergistic effects. First, CS-functionalized microspheres (GelMA-CS) with porous microstructure, good monodispersion, and about 200 µm diameter were efficiently and productively fabricated using microfluidic technology. After lyophilization, the microspheres with good local injection and tissue retention served as the loading platform for IL-1ra and achieved sustained release. In in vitro experiments, the IL-1ra-loaded microspheres exhibited good cytocompatibility and efficacy in inhibiting the inflammatory response of NP cells induced by lipopolysaccharide (LPS) and promoting the secretion of ECM. In in vivo experiments, the microspheres showed good histocompatibility, and local, minimally invasive injection of the IL-1ra-loaded microspheres could reduce inflammation, maintain the height of the intervertebral disc (IVD) and the water content of NP close to about 70 % in the sham group, and retain the integrated IVD structure. In summary, the GelMA-CS microspheres served as an effective loading platform for IL-1ra, eliminated inflammation through the controlled release of IL-1ra, and promoted ECM synthesis via CS to delay IVDD, thereby providing a promising intervention strategy for IVDD. STATEMENT OF SIGNIFICANCE: The strategy of simultaneously overcoming the overactive inflammation and restoring the anabolic/catabolic balance of the extracellular matrix (ECM) in nucleus pulposus (NP) has shown great potential prospects for alleviating intervertebral disc degeneration (IVDD). From the perspective of clinical translation, this study developed chondroitin sulfate functionalized microspheres to act as the effective delivery platform of IL-1ra, a natural antagonist of interleukin-1β. The IL-1ra loading microspheres (GelMA-CS-IL-1ra) showed good biocompatibility, good injection with tissue retention, and synergistic effects of inhibiting the inflammatory response induced by lipopolysaccharide and promoting the secretion of ECM in NPCs. In vivo, they also showed the beneficial effect of reducing the inflammatory response, maintaining the height of the intervertebral disc and the water content of the NP, and preserving the integrity of the intervertebral disc structure after only one injection. All demonstrated that the GelMA-CS-IL-1ra microspheres would have great promise for the minimally invasive treatment of IVDD.

Polyglycerol-Shelled Reduction-Sensitive Polymersome for DM1 Delivery to HER-2-Positive Breast Cancer

Supramolecular delivery systems with the prolonged circulation, the potential for diverse functionalization, and few toxin-related limitations have been extensively studied. For the present study, we constructed a linear polyglycerol-shelled polymersome attached with the anti-HER-2-antibody trastuzumab. We then covalently loaded the anticancer drug DM1 in the polymersome via dynamic disulfide bonding. The resulted trastuzumab-polymersome-DM1 (Tra-PS-DM1) exhibits a mean size of 95.3 nm and remarkable drug loading efficiency % of 99.3%. In addition to its superior stability, we observed the rapid release of DM1 in a controlled manner under reductive conditions. Compared to the native polymersomes, Tra-PS-DM1 has shown greatly improved cellular uptake and significantly reduced IC50 up to 17-fold among HER-2-positive cancer cells. Moreover, Tra-PS-DM1 demonstrated superb growth inhibition of HER-2-positive tumoroids; specifically, BT474 tumoroids shrunk up to 62% after 12 h treatment. With exceptional stability and targetability, the PG-shelled Tra-PS-DM1 appears as an attractive approach for HER-2-positive tumor treatment.

Hyaluronic acid-poly(glyceryl)10-stearate nanoemulsion for co-delivery of fish oil and resveratrol: Enhancing bioaccessibility and antioxidant potency

Hyaluronic acid (HA), an endogenous polysaccharide comprising alternating D-glucuronic acid and N-acetylglucosamine units, is renowned for its high hydrophilicity, biocompatibility, and biodegradability. These attributes have rendered HA invaluable across medical and drug delivery fields. HA can be altered through physical, chemical, or enzymatic methods to improve the properties of the modified substances. In this work, we synthesized a derivative via the esterification of HA with poly(glyceryl)10-stearate (PG10-C18), designated as HA-PG10-C18. This novel derivative was employed to fabricate a nano co-delivery system (HA-PG10-C18@Res-NE) for fish oil and resveratrol (Res), aiming to enhance their stability and bioaccessibility. An exhaustive investigation of HA-PG10-C18@Res-NE revealed that the HA-modified system displayed superior physicochemical stability, notably in withstanding oxidation and neutralizing free radicals. Moreover, in vitro simulated digestion underscored the system's enhanced bioaccessibility of Res and more efficient release of free fatty acids. These outcomes underscore the strategic advantage of HA in modifying PG10-C18 for nanoemulsion formulation. Consequently, HA-PG10-C18 stands as a promising emulsifier for encapsulating lipophilic bioactives in functional foods, nutraceuticals, and pharmaceuticals.

Improved physicochemical stability of fish oil nanoemulsion via a dense interfacial layer formed by hyaluronic acid-poly(glyceryl)10-stearate

This study aimed to synthesize a novel emulsifier, hyaluronic acid-poly(glyceryl)10-stearate (HA-PG10-C18), and employ it for the fabrication of nanoemulsions incorporating deep-sea fish oil to improve their apparent solubility and physicochemical stability. 1H NMR and FT-IR analyses indicated successful synthesis of HA-PG10-C18. Nanoemulsions of deep-sea fish oil loaded with HA-PG10-C18 (HA-PG10-C18@NE) were successfully fabricated by ultrasonic emulsification. The fixed aqueous layer thickness (FALT) of PG10-C18@NE and HA-PG10-C18@NE was determined and the FALT of both nanoemulsions was similar, while the surface density of HA-PG10-C18@NE (4.92 × 10-12 ng/nm2) is 60 % higher than that of PG10-C18@NE (3.07 × 10-12 ng/nm2). Notably, HA-PG10-C18@NE demonstrated an exceptional physicochemical stability when exposed to various stressed environmental conditions, especially its freeze-thaw stability. Moreover, after simulated in vitro digestion, the HA-PG10-C18@NE exhibited a comparatively greater liberation of free fatty acids (94.0 ± 1.7 %) when compared to the release observed in PG10-C18@NE (85.5 ± 2.2 %).

In Vitro Biocompatibility and Endothelial Permeability of Branched Polyglycidols Generated by Ring-Opening Polymerization of Glycidol with B(C6F5)3 under Dry and Wet Conditions

Polyglycidol or polyglycerol (PG), a polyether widely used in biomedical applications, has not been extensively studied in its branched cyclic form (bcPG), despite extensive research on hyperbranched PG (HPG). This study explores the biomedical promise of bcPG, particularly its ability to cross the blood-brain barrier (BBB). We evaluate in vitro biocompatibility, endothelial permeability, and formation of branched linear PG (blPG) as topological impurities in the presence of water. Small angle X-ray scattering in solution revealed a fractal dimension of approximately two for bcPG and the mixture bc+blPG, suggesting random branching. Comparisons of cytotoxicity and endothelial permeability between bcPG, bc+blPG, and HPG in a BBB model using hCMEC/D3 cells showed different biocompatibility profiles and higher endothelial permeability for HPG. bcPG showed a tendency to accumulate around cell nuclei, in contrast to the behavior of HPG. This study contributes to the understanding of the influence of polymer topology on biological behavior.

Molecular Dynamics Simulations for Rationalizing Polymer Bioconjugation Strategies: Challenges, Recent Developments, and Future Opportunities

The covalent modification of proteins with polymers is a well-established method for improving the pharmacokinetic properties of therapeutically valuable biologics. The conjugated polymer chains of the resulting hybrid represent highly flexible macromolecular structures. As the dynamics of such systems remain rather elusive for established experimental techniques from the field of protein structure elucidation, molecular dynamics simulations have proven as a valuable tool for studying such conjugates at an atomistic level, thereby complementing experimental studies. With a focus on new developments, this review aims to provide researchers from the polymer bioconjugation field with a concise and up to date overview of such approaches. After introducing basic principles of molecular dynamics simulations, as well as methods for and potential pitfalls in modeling bioconjugates, the review illustrates how these computational techniques have contributed to the understanding of bioconjugates and bioconjugation strategies in the recent past and how they may lead to a more rational design of novel bioconjugates in the future.

Zwitterionic Polymer: A New Paradigm for Protein Conjugation beyond PEG

To render protein drugs more suitable for clinical treatment, PEGylation has been widely used to ameliorate their inherent deficiencies, such as poor stability, rapid elimination in the bloodstream, and high immunogenicity. While increasingly PEGylated protein drugs have been approved by the FDA, the non-degradability of PEG and the emergence of anti-PEG antibodies after injection raise concerns about their cumulative chronic toxicity and long-term therapeutic efficacy. Zwitterionic polymer, with a unique structure containing equal amounts of positively charged and negatively charged groups, shows a different hydration behavior to PEG, which may be a superior PEG alternative for protein conjugation. In this concept review, a series of features beyond that of PEGylated protein exhibited by protein-zwitterionic polymer conjugate are discussed and some suggestions are presented for their future direction.

Antifouling polymers for nanomedicine and surfaces: recent advances

Antifouling polymers are materials that can resist nonspecific interactions with cells, proteins, and other biomolecules. Typically, they are hydrophilic polymers with polar or charged moieties that are capable of strong nonbonding interactions with water molecules. This propensity to bind water generates a surface hydration layer that reduces nonspecific interactions with other molecules and is paramount to the antifouling behavior. This property is especially useful for nanoscale applications such as nanomedicine and surface modifications at the molecular level. In nanomedicine, antifouling polymers such as poly(ethylene glycol) and its alternatives play a key role in shielding drug molecules and therapeutic proteins/genes from the immune system within nanoassemblies, thereby enabling effective delivery to target tissues. For coatings, antifouling polymers help to prevent adhesion of cells and molecules to surfaces and are thus valued in marine and biomedical device applications. In this Review, we survey recent advances in antifouling polymers in the context of nanomedicine and coatings, while shining the spotlight on the major polymer classes such as PEG, polyzwitterions, poly(oxazoline)s, and other nonionic hydrophilic polymers.

Empowering Cancer Therapy: Comparing PEGylated and Non-PEGylated Niosomes Loaded with Curcumin and Doxorubicin on MCF-7 Cell Line

Cancer remains an enduring challenge in modern society, prompting relentless pursuits to confront its complexities. However, resistance often emerges against conventional treatments, driven by their inherent limitations such as adverse effects and limited solubility. Herein, we spotlight a remarkable solution; a niosomal platform engineered to tandemly ferry two potent agents, doxorubicin (DOX) and curcumin (CUR). Notably, we delve into the pivotal role of PEGylation, unraveling its impact on therapeutic efficacy. These niosomes consist of Span 60, Tween 60, and cholesterol with a molar ratio of 5:2:3, which were prepared via a thin film hydration method. The physicochemical characterization of particles was performed using DLS, zeta potential measurement, SEM, and FTIR analysis. In addition, their encapsulation efficiency and release profile were determined using the HPLC method. Finally, their cytotoxicity and biocompatibility effects were checked by performing an MTT assay test on the MCF7 and L929 cell lines. The obtained results confirmed the successful fabrication of co-loaded niosomal structures with and without PEG coating. The fabricated nanoparticles had sizes in the range of 100 to 200 nm with a surface charge of about -18 mV for particles without PEG coating and -40 mV for coated particles. Notably, DOX encapsulation efficiency leaps from 20% to 62% in the transition from uncoated to coated, while CUR exhibits an impressive surge from 80% to 95%. The drug release was more controlled and slower in the coated sample. Finally, the MTT results confirmed the biocompatibility and synergistic effect of the simultaneous use of two drugs on cancer cells in the PEGylated niosomal particle. Based on the results, PEGylated niosomal particles can be considered adept vehicles for the simultaneous delivery of different chemotherapy cargoes with synergic interaction to overcome cancer.

Genetically encoded discovery of perfluoroaryl macrocycles that bind to albumin and exhibit extended circulation in vivo

Peptide-based therapeutics have gained attention as promising therapeutic modalities, however, their prevalent drawback is poor circulation half-life in vivo. In this paper, we report the selection of albumin-binding macrocyclic peptides from genetically encoded libraries of peptides modified by perfluoroaryl-cysteine SNAr chemistry, with decafluoro-diphenylsulfone (DFS). Testing of the binding of the selected peptides to albumin identified SICRFFC as the lead sequence. We replaced DFS with isosteric pentafluorophenyl sulfide (PFS) and the PFS-SICRFFCGG exhibited KD = 4-6 µM towards human serum albumin. When injected in mice, the concentration of the PFS-SICRFFCGG in plasma was indistinguishable from the reference peptide, SA-21. More importantly, a conjugate of PFS-SICRFFCGG and peptide apelin-17 analogue (N3-PEG6-NMe17A2) showed retention in circulation similar to SA-21; in contrast, apelin-17 analogue was cleared from the circulation after 2 min. The PFS-SICRFFC is the smallest known peptide macrocycle with a significant affinity for human albumin and substantial in vivo circulation half-life. It is a productive starting point for future development of compact macrocycles with extended half-life in vivo.

Cinnamyl-Modified Polyglycidol/Poly(ε-Caprolactone) Block Copolymer Nanocarriers for Enhanced Encapsulation and Prolonged Release of Cannabidiol

The present study describes the development of novel block copolymer nanocarriers of the phytocannabinoid cannabidiol (CBD), designed to enhance the solubility of the drug in water while achieving high encapsulation efficiency and prolonged drug release. Firstly, a well-defined amphiphilic block copolymer consisting of two outer hydrophilic polyglycidol (PG) blocks and a middle hydrophobic block of poly(ε-caprolactone) bearing pendant cinnamyl moieties (P(CyCL-co-CL)) were synthesized by the click coupling reaction of PG-monoalkyne and P(CyCL-co-CL)-diazide functional macroreagents. A non-modified polyglycidol/poly(ε-caprolactone) amphiphilic block copolymer was obtained as a referent system. Micellar carriers based on the two block copolymers were formed via the solvent evaporation method and loaded with CBD following two different protocols-loading during micelle formation and loading into preformed micelles. The key parameters/characteristics of blank and CBD-loaded micelles such as size, size distribution, zeta potential, molar mass, critical micelle concentration, morphology, and encapsulation efficiency were determined by using dynamic and static multiangle and electrophoretic light scattering, transmission electron microscopy, and atomic force microscopy. Embedding CBD into the micellar carriers affected their hydrodynamic radii to some extent, while the spherical morphology of particles was not changed. The nanoformulation based on the copolymer bearing cinnamyl moieties possessed significantly higher encapsulation efficiency and a slower rate of drug release than the non-modified copolymer. The comparative assessment of the antiproliferative effect of micellar CBD vs. the free drug against the acute myeloid leukemia-derived HL-60 cell line and Sezary Syndrome HUT-78 demonstrated that the newly developed systems have pronounced antitumor activity.

Dual role of polyglycerol vitamin E succinate in emulsions: An efficient antioxidant emulsifier

α-Tocopherol, as an oil-soluble vitamin with strong antioxidant activity. It is the most naturally abundant and biologically active form of vitamin E in humans. In this study, a novel emulsifier (PG20-VES) was synthesized by attaching hydrophilic twenty-polyglycerol (PG20) to hydrophobic vitamin E succinate (VES). This emulsifier was shown to have a relatively low critical micelle concentration (CMC = 3.2 μg/mL). The antioxidant activities and emulsification properties of PG20-VES were compared with those of a widely used commercial emulsifier: D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS). PG20-VES exhibited a lower interfacial tension, stronger emulsifying capacity and similar antioxidant property to TPGS. An in vitro digestion study showed that lipid droplets coated by PG20-VES were digested under simulated small intestine conditions. This study showed that PG20-VES is an efficient antioxidant emulsifier, which may have applications in the formulation of bioactive delivery systems in the food, supplement, and pharmaceutical industries.

One to one comparison of cell-free synthesized erythropoietin conjugates modified with linear polyglycerol and polyethylene glycol

With more than 20 Food and Drug Administration (FDA)-approved poly (ethylene glycol) (PEG) modified drugs on the market, PEG is the gold standard polymer in bioconjugation. The coupling improves stability, efficiency and can prolong blood circulation time of therapeutic proteins. Even though PEGylation is described as non-toxic and non-immunogenic, reports accumulate with data showing allergic reactions to PEG. Since PEG is not only applied in therapeutics, but can also be found in foods and cosmetics, anti-PEG-antibodies can occur even without a medical treatment. Hypersensitivity to PEG thereby can lead to a reduced drug efficiency, fast blood clearance and in rare cases anaphylactic reactions. Therefore, finding alternatives for PEG is crucial. In this study, we present linear polyglycerol (LPG) for bioconjugation as an alternative polymer to PEG. We report the conjugation of LPG and PEG by click-chemistry to the glycoprotein erythropoietin (EPO), synthesized in a eukaryotic cell-free protein synthesis system. Furthermore, the influence of the polymers on EPOs stability and activity on a growth hormone dependent cell-line was evaluated. The similar characteristics of both bioconjugates show that LPGylation can be a promising alternative to PEGylation.

Effect of the crosslinking agent on the biorepulsive and mechanical properties of polyglycerol membranes

Polyglycerol (PG) based surfaces materials and surfaces are well-established bio-compatible materials. Crosslinking of the dendrimeric molecules via their OH groups improves their mechanical stability up to the point that free-standing materials can be attained. Here, we investigate the effect of different crosslinkers on PG films regarding their biorepulsivity and mechanical properties. For this purpose, PG films with different thicknesses (15, 50 and 100 nm) were prepared by polymerizing glycidol in a ring-opening polymerization onto hydroxyl-terminated Si substrates. These films were then crosslinked using ethylene glycol diglycidyl ether (EGDGE), divinyl sulfone (DVS), glutaraldehyde (GA), 1,11-di(mesyloxy)-3,6,9-trioxaundecane (TEG-Ms₂) or 1,11-dibromo-3,6,9-trioxaundecane (TEG-Br₂), respectively. While DVS, TEG-Ms₂, and TEG-Br₂ resulted in slightly thinned films, presumably due to loss of unbound material, increase of film thickness was observed with GA and, in particular, EDGDE, what can be explained by the different crosslinking mechanisms. The biorepulsive properties of the crosslinked PG films were characterized by water contact angle (WCA) goniometry and various adsorption assays involving proteins (serum albumine, fibrinogen, γ-globulin) and bacteria (E. coli), showing that some crosslinkers (EGDGE, DVS) improved the biorepulsive properties, while others deteriorated them (TEG-Ms₂, TEG-Br₂, GA). As the crosslinking stabilized the films, it was possible to use a lift-off procedure to obtain free-standing membranes if the thickness of the films was 50 nm or larger. Their mechanical properties were examined with a bulge test showing high elasticities, with the Young's moduli increasing in the order GA ≈ EDGDE < TEG-Br₂ ≈ TEG-Ms₂ < DVS.

Chemical Approaches to Synthetic Drug Delivery Systems for Systemic Applications

Poor water solubility and low bioavailability of active pharmaceutical ingredients (APIs) are major causes of friction in the pharmaceutical industry and represent a formidable hurdle for pharmaceutical drug development. Drug delivery remains the major challenge for the application of new small-molecule drugs as well as biopharmaceuticals. The three challenges for synthetic delivery systems are: (i) controlling drug distribution and clearance in the blood; (ii) solubilizing poorly water-soluble agents, and (iii) selectively targeting specific tissues. Although several polymer-based systems have addressed the first two demands and have been translated into clinical practice, no targeted synthetic drug delivery system has reached the market. This Review is designed to provide a background on the challenges and requirements for the design and translation of new polymer-based delivery systems. This report will focus on chemical approaches to drug delivery for systemic applications.

Polyglycerol fatty acid esters as alternatives to PEGylated lipids for liposome coating

Background: Polyglycerol (PG) is a type of biocompatible hydrophilic polyether polyol, and it is considered as a potential alternative to polyethylene glycol (PEG) in modifying nanomedicines. Materials & methods: Polyglycerol fatty acid esters (PGFEs) were modified onto liposomes and their serum stability, pharmacokinetics, in vivo distribution and the capacity to induce anti-PEG IgM were compared with PEGylated liposomes (PEG-Lips). Results: Polyglycerol 10-monostearate (PG-10-MS) displayed considerable serum stability and compatibility with mice red blood cells, and it significantly prolonged the blood circulation of liposomes in the pharmacokinetics study compared with the unmodified liposomes, with a similar biodistribution pattern to that of the PEG-Lips. Moreover, PGFE-modified liposomes were less likely to induce the production of anti-PEG IgM. Conclusion: PGFEs could be considered as good candidates to replace PEG lipids for the preparation of liposomes.

PEtOxylated Interferon-α2a Bioconjugates Addressing H1N1 Influenza A Virus Infection

Influenza A viruses (IAV), including the pandemic 2009 (pdm09) H1N1 or avian influenza H5N1 virus, may advance into more pathogenic, potentially antiviral drug-resistant strains (including loss of susceptibility against oseltamivir). Such IAV strains fuel the risk of future global outbreaks, to which this study responds by re-engineering Interferon-α2a (IFN-α2a) bioconjugates into influenza therapeutics. Type-I interferons such as IFN-α2a play an essential role in influenza infection and may prevent serious disease courses. We site-specifically conjugated a genetically engineered IFN-α2a mutant to poly(2-ethyl-2-oxazoline)s (PEtOx) of different molecular weights by strain-promoted azide-alkyne cyclo-addition. The promising pharmacokinetic profile of the 25 kDa PEtOx bioconjugate in mice echoed an efficacy in IAV-infected ferrets. One intraperitoneal administration of this bioconjugate, but not the marketed IFN-α2a bioconjugate, changed the disease course similar to oseltamivir, given orally twice every study day. PEtOxylated IFN-α2a bioconjugates may expand our therapeutic arsenal against future influenza pandemics, particularly in light of rising first-line antiviral drug resistance to IAV.

Polyglycerols as Multi-Functional Platforms: Synthesis and Biomedical Applications

The remarkable and unique characteristics of polyglycerols (PG) have made them an attractive candidate for many applications in the biomedical and pharmaceutical fields. The presence of multiple hydroxy groups on the flexible polyether backbone not only enables the further modification of the PG structure but also makes the polymer highly water-soluble and results in excellent biocompatibility. In this review, the polymerization routes leading to PG with different architectures are discussed. Moreover, we discuss the role of these polymers in different biomedical applications such as drug delivery systems, protein conjugation, and surface modification.

Polymer selection impacts the pharmaceutical profile of site-specifically conjugated Interferon-α2a

Conjugation of poly(ethylene glycol) (PEG) to biologics is a successful strategy to favorably impact the pharmacokinetics and efficacy of the resulting bioconjugate. We compare bioconjugates synthesized by strain-promoted azide-alkyne cycloaddition (SPAAC) using PEG and linear polyglycerol (LPG) of about 20 kDa or 40 kDa, respectively, with an azido functionalized human Interferon-α2a (IFN-α2a) mutant. Site-specific PEGylation and LPGylation resulted in IFN-α2a bioconjugates with improved in vitro potency compared to commercial Pegasys. LPGylated bioconjugates had faster disposition kinetics despite comparable hydrodynamic radii to their PEGylated analogues. Overall exposure of the PEGylated IFN-α2a with a 40 kDa polymer exceeded Pegasys, which, in return, was similar to the 40 kDa LPGylated conjugates. The study points to an expanded polymer design space through which the selected polymer class may result in a different distribution of the studied bioconjugates.

Confinements of Thermoresponsive Dendronized Polymers to Proteins

Crowding environment created by host polymers plays crucial roles in manipulating interactions with proteins and modulating their bioactivity. Here, we report our investigation on interactions between polymers and proteins in...

Reincarnation of the Analytical Ultracentrifuge: Emerging Opportunities for Nanomedicine

The analytical ultracentrifuge (AUC) and the modern field of analytical ultracentrifugation found its inception approximately a century ago. We highlight the scope of its major experimental opportunities as a transport-based method, contemporary and up-and-coming investigation potential for polymers, polymer-drug conjugates, polymer assemblies, as well as medical nanoparticles. Special focus lies on molar mass estimates of unimeric polymeric species, self-assemblies in solution, and (co)localization of multicomponent systems in solution alongside the material-biofluid interactions. We close with present challenges and incentives for future research.

Assembling BH3-mimic peptide into a nanocluster to target intracellular Bcl2 towards the apoptosis induction of cancer cell

Bcl-2, an anti-apoptotic protein, is always overexpressed in tumor cells to suppress the pro-apoptotic function of Bax, thereby prolonging the life of the tumor. However, BH3 proteins could directly activate Bax via antagonizing Bcl-2 to induce apoptosis in response to the stimulation. Thus, mimicking BH3 proteins with a peptide is a potential strategy for anti-cancer therapy. Unfortunately, clinical translation of BH3-mimic peptide is hindered by its inefficacious cellular internalization and proteolysis resistance. Herein, we translated a BH3-mimic peptide into a peptide-auric spheroidal nanocluster (BH3-AuNp), in which polymeric BH3-Auric precursors [Au¹⁺-S-BH3]_narein situself-assembled on the surface of gold nanoparticles by a one-pot synthesis. Expectedly, this strategy could improve the anti-proteolytic ability and cytomembrane penetrability of the BH3 peptide. As a result, BH3-AuNp successfully induced the apoptosis of two cancer cell lines by an order of magnitude compared to BH3. This therapeutic and feasible peptide nano-engineering strategy will help peptides overcome the pharmaceutical obstacles, awaken its biological functions, and possibly revive the research about peptide-derived nanomedicine.

Molecular Insights into Site-Specific Interferon-α2a Bioconjugates Originated from PEG, LPG, and PEtOx

Conjugation of biologics with polymers modulates their pharmacokinetics, with polyethylene glycol (PEG) as the gold standard. We compared alternative polymers and two types of cyclooctyne linkers (BCN/DBCO) for bioconjugation of interferon-α2a (IFN-α2a) using 10 kDa polymers including linear mPEG, poly(2-ethyl-2-oxazoline) (PEtOx), and linear polyglycerol (LPG). IFN-α2a was azide functionalized via amber codon expansion and bioorthogonally conjugated to all cyclooctyne linked polymers. Polymer conjugation did not impact IFN-α2a's secondary structure and only marginally reduced IFN-α2a's bioactivity. In comparison to PEtOx, the LPG polymer attached via the less rigid cyclooctyne linker BCN was found to stabilize IFN-α2a against thermal stress. These findings were further detailed by molecular modeling studies which showed a modulation of protein flexibility upon PEtOx conjugation and a reduced amount of protein native contacts as compared to PEG and LPG originated bioconjugates. Polymer interactions with IFN-α2a were further assessed via a limited proteolysis (LIP) assay, which resulted in comparable proteolytic cleavage patterns suggesting weak interactions with the protein's surface. In conclusion, both PEtOx and LPG bioconjugates resulted in a similar biological outcome and may become promising PEG alternatives for bioconjugation.

Linear Polyglycerol for N-terminal-selective Modification of Interleukin-4

Polymer conjugation to biologics is of key interest to the pharmaceutical industry for the development of potent and long acting biotherapeutics, with poly(ethylene glycol) (PEG) being the gold standard. Within the last years, unwanted PEG-related side effects (immunological reactions, antibody formation) arose, therefore creating several attempts to establish alternative polymers with similar potential to PEG. In this article, we synthesized N-terminal bioconjugates of the potential therapeutic human interleukin-4 (hIL-4 WT) with linear polyglycerol (LPG) of 10 and 40 kDa and compared it with its PEG analogs of same nominal weights. Polyglycerol is a highly hydrophilic polymer with good biocompatibility and therefore represents an alternative polymer to PEG. Both polymer types resulted in similar conjugation yields, comparable hydrodynamic sizes and an unaltered secondary structure of the protein after modification. LPG- and PEG-bioconjugates remained stable in human plasma, whereas binding to human serum albumin (HSA) decreased after polymer modification. Furthermore, only minor differences in bioactivity were observed between LPG- and PEG-bioconjugates of same nominal weights. The presented findings are promising for future pharmacokinetic evaluation of hIL-4-polymer bioconjugates.

Acetal-Based Functional Epoxide Monomers: Polymerizations and Applications

Protecting group chemistry is essential for various organic transformation and polymerization processes. In particular, conventional anionic ring-opening polymerization (AROP) often requires proper protecting group chemistry because it is typically incompatible with most functional groups due to the highly basic and nucleophilic conditions. In this context, many functional epoxide monomers with proper protecting groups are developed, including the acetal group as a representative example. Since the early introduction of ethoxyethyl glycidyl ether, there is significant development of acetal-based monomers in the polyethers. These monomers are now utilized not only as protecting groups for hydroxyl groups under AROP conditions but also as pH-responsive moieties for biomedical applications, further expanding their utility in the use of functionalized polyethers. Recent progress in this field is outlined from their synthesis, polymerization, and biomedical applications.

Effect of Branching Degree of Dendritic Polyglycerols on Plasma Protein Adsorption: Relationship between Hydration States and Surface Morphology

This study focuses on dendritic glycerols and investigates the construction of biocompatible surfaces by understanding how differences in the branching of these molecules change the interactions with the biological components. The two molecules, polyglycerol dendrimer (PGD), which has a completely branched structure, and hyperbranched polyglycerol (HPG), which has an incompletely branched structure, are compared and the differences in branching are evaluated. It is shown that PGD has a little bit more intermediate water than HPG, which reflects the differences in the branching. The effect of surface state on the adsorption of the plasma proteins, human serum albumin (HSA), fibrinogen (Fib), and fibronectin (FN), is discussed by modifying a glass surface using these molecules with different hydration states. The adsorption of HSA decreases to several percent for HPG and 10% for PGD compared to unmodified substrate. Although the adsorption of Fib decreases to 5% for HPG, an increase to 150% is observed for PGD. Since this specific Fib adsorption observed only onto PGD is suppressed in the cases of a mixed solution of HSA and Fib or sequentially using HSA solution and then Fib solution, it is thought that the Vroman effect is suppressed on the PGD-modified surface. Furthermore, when AFM measurements are performed in PBS to understand the surface roughness, PGD is found to be more highly non-uniform. Because of this, the nanometer scale roughness that is significantly observed only on the PGD-modified surface is thought to have an effect on the characteristic adsorption properties of Fib. Thus, although both PGD and HPG with different branching have intermediate water, the proportion differs between PGD and HPG. Therefore, it is found that differences occur in the plasma protein adsorption mechanisms depending on the coordinates and density of hydroxyl groups within the molecules.

Prolonged activity of exenatide: Detailed comparison of Site-specific linear polyglycerol- and poly(ethylene glycol)-conjugates

Exenatide is a small therapeutic peptide being currently used in clinic for the treatment of diabetes mellitus type II, however, displaying a short blood circulation time which makes two daily injections necessary. Covalent polymer modification of a protein is a well-known approach to overcome this limitation, resulting in steric shielding, an increased size and therefore a longer circulation half-life. In this study, we employed site-selective C-terminal polymer ligation of exenatide via copper-catalyzed azide-alkyne-cycloaddition (CuAAC) to yield 1:1-conjugates of either poly(ethylene glycol) (PEG) or linear polyglycerol (LPG) of different molecular weights. Our goal was to compare the impact of the two polymers on size, structure and activity of exenatide on the in vitro and in vivo level. Both polymers did not alter the secondary structure of exenatide and expectedly increased its hydrodynamic size, where the LPG-versions of exenatide showed slightly smaller values than their PEG-analogs of same molecular weight. Upon conjugation, GLP-1 receptor activation was diminished, however, still enabled maximum receptor response at slightly higher concentrations. Exenatide modified with a 40 kDa LPG (Ex-40-LPG) showed significant reduction of the blood glucose level in diabetic mice for up to 72 h, which was comparable to its PEG-analog, but 9-fold longer than native exenatide (8 h).