PEGylation of Human Vascular Endothelial Growth Factor

Positional isoform analysis of PEGylated biotherapeutic protein using a novel peptide-based reversed-phase liquid chromatography with UV detection

PEGylation, the covalent attachment of poly(ethylene glycol) (PEG) to biomolecules, is a well-established molecular modification strategy that enhances the pharmacological properties of conjugated proteins by improving stability, reducing immunogenicity, extending half-life, and increasing solubility. Despite its benefits, PEGylated proteins are often heterogeneous mixtures containing positional isoforms that are challenging to eliminate and can significantly impact the biological activity of drugs. This study developed a reversed-phase ultra-performance liquid chromatography (RP-UPLC) method for the separation and quantification of positional isoforms in commercial PEGylated recombinant human growth hormone (PEG-rhGH) at the peptide level. In this strategy, PEG-rhGH was digested into peptides via trypsin treatment and then separated and quantified using RP-UPLC. Under the chromatography condition optimized from Quality by Design (QbD) principles, this method can effectively distinguish the PEGylated peptides in five isomers. MALDI-TOF MS, SDS-PAGE and Edman degradation indicated that each of these five isomers was conjugated with one 40 kDa branched PEG at a specific lysine residue and the N-terminal. Through the concentration correction of PEGylated peptides varying in sequence lengths, the proportion of five modified sites can be quantified. The comparative assay showed that this strategy effectively addresses the limitations of the commonly used IEC method, especially under challenging conditions like post-translational modifications (e.g., oxidation, deamidation, and cyclization) and conformational changes. As a result, it offers improved robustness and accuracy. Furthermore, the proposed RP-UPLC method exhibited outstanding repeatability across various storage conditions, making it a reliable tool for quality control and product release in the biopharmaceutical industry.

Advances in Designer Materials for Chronic Wound Healing

Significance: Nonhealing or chronic wounds represent a significant and growing global health concern, imposing substantial burdens on individuals, health care systems, and economies worldwide. Although the standard-of-care treatment involves the application of wound dressings, most dressing materials are not specifically designed to address the pathological processes underlying chronic wounds. This review highlights recent advances in biomaterial design tailored to chronic wound healing. Recent Advances: Chronic wounds are characterized by persistent inflammation, impaired granulation tissue formation, and delayed re-epithelialization. Newly developed designer materials aim to manage reactive oxygen species and extracellular matrix degradation to suppress inflammation while promoting vascularization, cell proliferation, and epithelial migration to accelerate tissue repair. Critical Issues: Designing optimal materials for chronic wounds remains challenging due to the diverse etiology and a multitude of pathological mechanisms underlying chronic wound healing. While designer materials can target specific aberrations, designing a materials approach that restores all aberrant wound-healing processes remains the Holy Grail. Addressing these issues requires a deep understanding of how cells interact with the materials and the complex etiology of chronic wounds. Future Directions: New material approaches that target wound mechanics and senescence to improve chronic wound closure are under development. Layered materials combining the best properties of the approaches discussed in this review will pave the way for designer materials optimized for chronic wound healing.

The Art of PEGylation: From Simple Polymer to Sophisticated Drug Delivery System

The development of effective drug delivery systems (DDSs) is important for cancer and infectious disease treatment to overcome low bioavailability, rapid clearance and the toxicity of the therapeutic towards non-targeted healthy tissues. This review discusses how PEGylation, the attachment of poly(ethylene glycol) (PEG) molecules to nanoparticles (NPs), enhances drug pharmacokinetics by creating a "stealth effect". We provide the synthesis methods for several PEG derivatives, their conjugation with NPs, proteins and characterization using modern analytical tools. This paper focuses particularly on covalent conjugation and self-assembly strategies for successful PEGylation and discusses the influence of PEG chain length, density and conformation on drug delivery efficiency. Despite the PEGylation benefits, there are several challenges associated with it, including immunogenicity and reduced therapeutic efficacy due to accelerated blood clearance. Therefore, the balance between PEGylation benefits and its immunogenic risks remains a critical area of investigation.

Method for Screening Sodium Cyanoborohydride for Free Cyanide Content and Its Impact on Bioconjugation Chemistry

Sodium cyanoborohydride (CBH) is commonly used as a mild reducing agent in the reductive amination of aldehydes and free amines. Within the pharmaceutical industry, this reaction is employed in the bioconjugation of proteins and peptides. Free cyanide species such as HCN and NaCN are known residual impurities in CBH that can contribute to the formation of undesired side products including cyanoamines and cyanohydrins. In commercial processes, the potential for bound cyanated species requires an analytical control strategy to monitor and mitigate any risk to human health. Given these concerns, minimization of cyanated side products is of utmost priority and can be achieved through a robust control strategy of quantitative screening of starting materials for free cyanide. Alternative risk mitigation strategies such as purification of bound cyanide containing species to pure species are less effective due to minor chemical differences between the expected product and bound cyanide species. Herein, we present a simple chromatographic assay for the quantitation of free cyanide in the raw material sodium cyanoborohydride. Method development, robustness evaluation, and scientific soundness assessment are reported with excellent linearity, accuracy, precision, and specificity. Additionally, this method was applied for the evaluation of raw material supplied from 10 commercial sources, none of which report a specification for free cyanide within their certificate of analysis. The measured free cyanide from these vendors ranged from 8 to 80 mM concentration, thereby confirming the value of screening these raw materials. Finally, we demonstrate the impact of free cyanide on a model bioconjugation reaction between ornithine and glyceraldehyde.

Polyethylene glycol and immunology: aspects of allergic reactions and their mechanisms, as well as ways to prevent them in clinical practice

In modern medical practice, where polyethylene glycol is widely used as a component of various drugs, such as vaccines, chemotherapy drugs, and antibiotics, including vaccines, the issue of allergic reactions to this substance is becoming increasingly important. The purpose of this study is to review and systematise data on various aspects of allergic reactions to polyethylene glycol with the aim of better understanding their pathogenesis, clinical manifestations, diagnostic methods, and possible treatment approaches. The study analysed literature data in modern databases, such as MEDLINE, PubMed, and Scopus, on allergic reactions to polyethylene glycol, using the keywords: "PEG", "polyethylene glycol", "allergy", "side effect". The main aspects of allergy to this substance were highlighted, including mechanisms of development, diagnostic methods, and possible treatment strategies. The analysis found that allergic reactions to polyethylene glycol can manifest in a variety of ways, including anaphylaxis and systemic reactions. A possible role for the immune response has been identified, including the production of IgE and IgM antibodies, complement activation, and accelerated clearance in response to polyethylene glycol, in blood plasma. Data are also provided on how to diagnose an increased risk of an allergic reaction in patients who have previously received drugs with this type of drug transporter and in patients receiving high molecular weight types of polyethylene glycol. The results of this review contribute to a better understanding of allergic reactions to polyethylene glycol and provide information for the development of more effective diagnostic and treatment methods.

Site-specific PEGylation of recombinant tissue-type plasminogen activator

Tissue-type plasminogen activator (tPA) is the gold standard for emergency treatment of ischemic stroke, which is the third leading cause of death worldwide. Major challenges of tPA therapy are its rapid elimination by plasminogen activator inhibitor-1 (PAI-1) and hepatic clearance, leading to the use of high doses and consequent serious side effects, including internal bleeding, swelling and low blood pressure. In this regard, we developed three polyethylene glycol (PEG)ylated tPA bioconjugates based on the recombinant human tPA drug Alteplase using site-specific conjugation strategies. The first bioconjugate with PEGylation at the N-terminus of tPA performed by reductive alkylation showed a reduced proteolytic activity of 68 % compared to wild type tPA. PEGylation at the single-free cysteine of tPA with linear and branched PEG revealed similar proteolytic activities as the wild-type protein. Moreover, both bioconjugates with PEG-cysteine-modification showed 2-fold slower inhibition kinetics by PAI-1. All bioconjugates increased in hydrodynamic size as a critical requirement for half-life extension.