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

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.

Bioconjugation of a Fibroblast Activation Protein Targeted Interleukin-4

Interleukin-4 (IL-4) is an immune-modulating therapeutic with growing potential for the treatment of inflammatory diseases. Current challenges of IL-4 therapy include a low serum half-life and pleiotropic activity, suggesting effective targeting of IL-4. To develop an interleukin-4 bioconjugate with rapid targeting to inflammatory disease sites, we report the chemical synthesis, bioconjugation, and in vitro characterization of a murine interleukin-4 (mIL-4) conjugate decorated with a fibroblast activation protein inhibitor (FAPI). The FAPI targeting moiety features 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) to allow future biodistribution and imaging studies of the FAPI-mIL-4 bioconjugate. We demonstrated site-specific coupling of mIL-4 and FAPI-DOTA deploying chemo-enzyme and enzyme chemistries with a high purity exceeding 95%. The FAPI-DOTA modified mIL-4 was bioactive with polarization of murine macrophages into the M2 state while maintaining specific binding to FAP on fibroblast cells. Together, these results point to future in vivo use of the FAPI-mIL-4 bioconjugate to assess biodistribution and biological effects in animal models of inflammatory joint disease.

PEG-Lipids: Quantitative Study of Unimers and Aggregates Thereof by the Methods of Molecular Hydrodynamics

Understanding the polymorphism of lipids in solution is the key to the development of intracellular delivery systems. Here, we study the dynamics of poly(ethylene glycol)-lipid (PEG-Lipid) conjugates aiming at a better understanding of their molecular properties and aggregation behavior in solution. Those PEG-Lipids are used as components of lipid nanoparticles (LNPs). LNPs are gaining increased popularity, e.g., by their utilization in modern vaccination strategies against SARS-CoV-2. Characterization of the systems is conducted by the classical methods of hydrodynamics in different solvents, such as ethanol and water, which are also commonly used for LNP formulation. We were able to elucidate the structurally associated hydrodynamic properties of isolated PEG-Lipids in ethanol, revealing the typically expected values of the hydrodynamic invariant for random coil polymers. By virtue of the same experimental setting, the PEG-Lipids' behavior in water was as well studied, which is a less good solvent than ethanol for the PEG-Lipids. Our experiments demonstrate that PEG-Lipids dissolved in water form well-defined micelles that can quantitatively be characterized in terms of their degree of aggregation of PEG-Lipid polymer unimers, their hydrodynamic size, and solvation, i.e., the quantitative determination of water contained or associated to the identified micelles. Quantitative results obtained from classical hydrodynamic analyses are fully supported by studies with standard dynamic light scattering (DLS). The obtained diffusion coefficients and hydrodynamic sizes are in excellent agreement with numerical results derived from analytical ultracentrifugation (AUC) data. Cryo-transmission electron microscopy (cryo-TEM) supports the structural insight from hydrodynamic studies, particularly, in terms of the observed spherical structure of the formed micelles. We demonstrate experimentally that the micelle systems can be considered as solvent-permeable, hydrated spheres.

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.

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.