Monodisperse engineered PEGs for bio-related applications

Synthesis of Antifouling Poly(ethylene glycol) Brushes via "Grafting to" Approach for Improved Biodistribution

Polyethylene glycol (PEG) modification of materials has been identified to mitigate the challenge of biofouling. However, the practical application of PEGylation has been hampered by a low PEGylation density on the material surface. Therefore, developing efficient strategies to promote the PEGylation density is crucial. In this study, PEG brushes (PBs) with various structures were synthesized and their physicochemical properties and biomedical applications were investigated. Compared to benzaldehyde (BA), o-phthalaldehyde (OPA) exhibited higher reactivity with amine groups, resulting in increased grafting density (as high as 96.3%) and improved antifouling properties of PEG brushes. Bottlebrushes fabricated by PEG-OPA and polylysine demonstrated a prolonged circulation time in blood and enhanced potential for magnetic resonance imaging of tumors. Furthermore, the rigidity of the backbone was found to be crucial for the antifouling properties of PEG brushes both in vitro and in vivo. These findings are significant and provide valuable insights into designing biomaterials with superior antifouling performance.

Inhibitors of amyloid fibril formation

Many diseases are caused by misfolded and denatured proteins, leading to neurodegenerative diseases. In recent decades researchers have developed a variety of compounds, including polymeric inhibitors and natural compounds, antibodies, and chaperones, to inhibit protein aggregation, decrease the toxic effects of amyloid fibrils, and facilitate refolding proteins. The causes and mechanisms of amyloid formation are still unclear, and there are no effective treatments for Amyloid diseases. This section describes research and achievements in the field of inhibiting amyloid accumulation and also discusses the importance of various strategies in facilitating the removal of aggregates species (refolding) in the treatment of neurological diseases such as chemical methods like as, small molecules, metal chelators, polymeric inhibitors, and nanomaterials, as well as the use of biomolecules (peptide and, protein, nucleic acid, and saccharide) as amyloid inhibitors, are also highlighted.

Striving for Uniformity: A Review on Advances and Challenges To Achieve Uniform Polyethylene Glycol

Poly(ethylene glycol) (PEG) is the polymer of choice in drug delivery systems due to its biocompatibility and hydrophilicity. For over 20 years, this polymer has been widely used in the drug delivery of small drugs, proteins, oligonucleotides, and liposomes, improving the stability and pharmacokinetics of many drugs. However, despite the extensive clinical experience with PEG, concerns have emerged related to its use. These include hypersensitivity, purity, and nonbiodegradability. Moreover, conventional PEG is a mixture of polymers that can complicate drug synthesis and purification leading to unwanted immunogenic reactions. Studies have shown that uniform PEGylated drugs may be more effective than conventional PEGylated drugs as they can overcome issues related to molecular heterogeneity and immunogenicity. This has led to significant research efforts to develop synthetic procedures to produce uniform PEGs (monodisperse PEGs). As a result, iterative step-by-step controlled synthesis methods have been created over time and have shown promising results. Nonetheless, these procedures have presented numerous challenges due to their iterative nature and the requirement for multiple purification steps, resulting in increased costs and time consumption. Despite these challenges, the synthetic procedures went through several improvements. This review summarizes and discusses recent advances in the synthesis of uniform PEGs and its derivatives with a focus on overall yields, scalability, and purity of the polymers. Additionally, the available characterization methods for assessing polymer monodispersity are discussed as well as uniform PEG applications, side effects, and possible alternative polymers that can overcome the drawbacks.

Alkyl Substituent in Heterocyclic Substrate, Carbon Skeleton Length of O-Nucleophilic Agent and Conditions Influence the Product Composition from Competitive Reactions of SNipso Substitution by Aliphatic Oligoethers

Using 1H NMR spectroscopy, we studied the relative mobility of the NO2 group in 1-alkyl-5-nitro-1,2,4-triazoles in the reaction of nucleophilic heterocyclic substitution by aliphatic oligoethers. The main pathways of the SNipso substitution process and the composition of resultant products from competitive reactions were examined, and the key factors influencing the relative mobility of the nitro group, such as the nitrotriazole substrate constitution, the carbon skeleton length of the O-nucleophilic agent and the process conditions, were discussed. Several independent competitive reactions directed towards the substitution of the nitro group at position C(5) in the alkyltriazole substrate by different types of nucleophiles such as alkoxide-, hydroxide- and triazolonate anions were observed to take place under conditions used. The major reaction yielded oligoethers containing terminal alkyltriazole heterocycles. Secondary reactions occurred to form the corresponding triazolone and N-C triazolyl triazolone structures in the reaction system. Additionally, in excess of the alkaline agent, alkaline hydrolysis was observed to proceed at the final stages of the process involving the O-nucleophile having a longer oligoether backbone in the series studied, leading to the formation of new O-nucleophilic sites. The obtained findings can provide a foundation for devising a method for the modification of a wide range of commercially available aliphatic oligo- or polyethers to prepare functional macromolecules whose terminals carry bioactive 1,2,4-triazole heterocycles located at a desired distance from each other.

Carboxyl PEGylation of magnetic nanoparticles as antithrombotic and thrombolytic agents by calcium binding

Known to be biocompatible and hemocompatible, polyethylene glycol (PEG) has been widely used as anti-fouling coating of biomaterials. Nanoparticles coated with functionalized PEG were also investigated for their nano-cell interactions, but seldomly on the coagulation system, especially with platelets. Both experiments and molecular dynamic simulations indicate that terminal carboxylation of PEG promotes its binding with calcium, especially in the ionized form, which makes it potential anticoagulants. Further, the carboxyl PEGylated magnetic nanoparticle (HOOC-PEG₂₀₀₀-MNP) exhibits significantly increased anticoagulant and antiplatelet properties, by entering the open canalicular system (OCS) of human platelets and binding with the cytoplasmic calcium ions. HOOC-PEG₂₀₀₀-MNP also acts as effective thrombolytic agents in dissolving mature blood clots under oscillating magnetic field both in vitro and in vivo. Therefore, the carboxyl PEGylated magnetic nanoparticles are prototype agents for antithrombotic and thrombolytic therapies and provide a versatile platform for targeted and effective treatments of acute cardiovascular diseases.

Discrete Libraries of Amphiphilic Poly(ethylene glycol) Graft Copolymers: Synthesis, Assembly, and Bioactivity

Poly(ethylene glycol) (PEG) is an important and widely used polymer in biological and pharmaceutical applications for minimizing nonspecific binding while improving blood circulation for therapeutic/imaging agents. However, commercial PEG samples are polydisperse, which hampers detailed studies on chain length-dependent properties and potentially increases antibody responses in pharmaceutical applications. Here, we report a practical and scalable method to prepare libraries of discrete PEG analogues with a branched, nonlinear structure. These lipid-PEG derivatives have a monodisperse backbone with side chains containing a discrete number of ethylene glycol units (3 or 4) and unique functionalizable chain ends. Significantly, the branched, nonlinear structure is shown to allow for efficient nanoparticle assembly while reducing anti-PEG antibody recognition when compared to commercial polydisperse linear systems, such as DMG-PEG2000. By enabling the scalable synthesis of a broad library of graft copolymers, fundamental self-assembly properties can be understood and shown to directly correlate with the total number of PEG units, nature of the chain ends, and overall backbone length. These results illustrate the advantages of discrete macromolecules when compared to traditional disperse materials.

Synthesis of symmetrical secondary oligoethylene glycolated amines from diethanolamine

Monodisperse oligoethylene glycols (M-OEGs)-containing symmetrical secondary amines are highly valuable synthetic intermediates in drug development and materials sciences. Scalable three-step synthesis of M-OEGs secondary amines with flexible M-OEGs and/or alkyl chains is described herein. Through reduction amination of diethanolamine, Williamson ether synthesis, and subsequent deprotection, a series of M-OEGs secondary amines with diverse and fine-tunable chemical structures were conveniently prepared. The presented strategy is attractive with readily available starting materials, simple catalytic systems, scalable synthesis, and avoids the use of explosive sodium azide.

Understanding the Role and Impact of Poly (Ethylene Glycol) (PEG) on Nanoparticle Formulation: Implications for COVID-19 Vaccines

Poly (ethylene glycol) (PEG) is a widely used polymer in a variety of consumer products and in medicine. PEGylation refers to the conjugation of PEG to drugs or nanoparticles to increase circulation time and reduce unwanted host responses. PEG is viewed as being well-tolerated, but previous studies have identified anti-PEG antibodies and so-called pseudoallergic reactions in certain individuals. The increased use of nanoparticles as contrast agents or in drug delivery, along with the introduction of mRNA vaccines encapsulated in PEGylated lipid nanoparticles has brought this issue to the fore. Thus, while these vaccines have proven to be remarkably effective, rare cases of anaphylaxis have been reported, and this has been tentatively ascribed to the PEGylated carriers, which may trigger complement activation in susceptible individuals. Here, we provide a general overview of the use of PEGylated nanoparticles for pharmaceutical applications, and we discuss the activation of the complement cascade that might be caused by PEGylated nanomedicines for a better understanding of these immunological adverse reactions.

Effects of polyethylene glycol on the surface of nanoparticles for targeted drug delivery

The rapid development of drug nanocarriers has benefited from the surface hydrophilic polymers of particles, which has improved the pharmacokinetics of the drugs. Polyethylene glycol (PEG) is a kind of polymeric material with unique hydrophilicity and electrical neutrality. PEG coating is a crucial factor to improve the biophysical and chemical properties of nanoparticles and is widely studied. Protein adherence and macrophage removal are effectively relieved due to the existence of PEG on the particles. This review discusses the PEGylation methods of nanoparticles and related techniques that have been used to detect the PEG coverage density and thickness on the surface of the nanoparticles in recent years. The molecular weight (MW) and coverage density of the PEG coating on the surface of nanoparticles are then described to explain the effects on the biophysical and chemical properties of nanoparticles.

Optimization of PEGylated KL4 Peptide for siRNA Delivery with Improved Pulmonary Tolerance

Pulmonary delivery of small interfering RNA (siRNA) is a promising therapeutic strategy for treating various respiratory diseases but an effective carrier for the delivery of siRNA into the cells of the lungs and a robust gene-silencing effect is still lacking. Previously, we reported that the KL4 peptide, a synthetic cationic peptide with a repeating KLLLL sequence, can mediate effective siRNA transfection in lung epithelial cells but its high hydrophobic leucine content, and hence poor water solubility, limits its application as a delivery vector. Here, we show that the covalent attachment of monodisperse poly(ethylene glycol) (PEG) improves the solubility of KL4 and the uptake of its complex with siRNA into lung epithelial cells, such that very robust silencing is produced. All PEGylated KL4 peptides, with PEG length varying between 6 and 24 monomers, could bind and form nanosized complexes with siRNA, but the interaction between siRNA and peptides became weaker as the PEG chain length increased. All PEGylated KL4 peptides exhibited satisfactory siRNA transfection efficiency on three human lung epithelial cell lines, including A549 cells, Calu-3 cells, and BEAS-2B cells. The PEG₁₂KL4 peptide, which contains 12 monomers of PEG, was optimal for siRNA delivery and also demonstrated a low risk of inflammatory response and toxicity in vivo following pulmonary administration.

Stacking of nanorings to generate nanotubes for acceleration of protein refolding

Self-assembly and photoisomerization of azobenzene-based amphiphilic molecules produced nanorings with an inner diameter of 25 nm and lengths of <40 nm. The nanorings, which consisted of a single bilayer membrane of the amphiphiles, retained their morphology in the presence of a stacking inhibitor; whereas in the absence of the inhibitor, the nanorings stacked into short nanotubes (<500 nm). When subjected to mild heat treatment, these nanotubes joined end-to-end to form nanotubes with lengths of several tens of micrometers. The nanorings and the short and long nanotubes were able to encapsulate proteins and thereby suppress aggregation induced by thermal denaturation. In addition, the nanotubes accelerated refolding of denatured proteins by encapsulating them and then releasing them into the bulk solution; refolding occurred simultaneously with release. In contrast, the nanorings did not accelerate protein refolding. Refolding efficiency increased with increasing nanotube length, indicating that the re-aggregation of the proteins was strictly inhibited by lowering the concentration of the proteins in the bulk solution as the result of the slow release from the longer nanotubes. The migration of the proteins through the long, narrow nanochannels during the release process will also contribute to refolding.

Basic Amino Acid Conjugates of 1,2-Diselenan-4-amine with Protein Disulfide Isomerase-like Functions as a Manipulator of Protein Quality Control

Protein disulfide isomerase (PDI) can assist immature proteins to correctly fold by controlling cysteinyl disulfide (SS)-relating reactions (i. e., SS-formation, SS-cleavage, and SS-isomerization). PDI controls protein quality by suppressing protein aggregation, as well as functions as an oxidative folding catalyst. Following the amino acid sequence of the active center in PDI, basic amino acid conjugates of 1,2-diselenan-4-amine (1), which show oxidoreductase- and isomerase-like activities for SS-relating reactions, were designed as a novel PDI model compound. By conjugating the amino acids, the diselenide reduction potential of compound 1 was significantly increased, causing improvement of the catalytic activities for all SS-relating reactions. Furthermore, these compounds, especially histidine-conjugated one, remarkably suppressed protein aggregation even at low concertation (0.3 mM∼). Thus, it was demonstrated that the conjugation of basic amino acids into 1 simultaneously achieves the enhancement of the redox reactivity and the capability to suppress protein aggregation.

Effective mRNA pulmonary delivery by dry powder formulation of PEGylated synthetic KL4 peptide

Pulmonary delivery of messenger RNA (mRNA) has considerable potential as therapy or vaccine for a range of lung diseases. Inhaled dry powder formulation of mRNA is particularly attractive as it has superior stability and dry powder inhaler is relatively easy to use. A safe and effective mRNA delivery vector as well as a suitable particle engineering method are required to produce a dry powder formulation that is respirable and mediates robust transfection in the lung. Here, we introduce a novel RNA delivery vector, PEG₁₂KL4, in which the synthetic cationic KL4 peptide is attached to a monodisperse linear PEG of 12-mers. The PEG₁₂KL4 formed nano-sized complexes with mRNA at 10:1 ratio (w/w) and mediated effective transfection on human lung epithelial cells. PEG₁₂KL4/mRNA complexes were successfully formulated into dry powder by spray drying (SD) and spray freeze drying (SFD) techniques. Both SD and SFD powder exhibited satisfactory aerosol properties for inhalation. More importantly, the biological activity of the PEG₁₂KL4 /mRNA complexes were successfully preserved after drying. Using luciferase mRNA, the intratracheal administration of the liquid or powder aerosol of PEG₁₂KL4 /mRNA complexes at a dose of 5μg mRNA resulted in luciferase expression in the deep lung region of mice 24h post-transfection. The transfection efficiency was superior to naked mRNA or lipoplexes (Lipofectamine 2000), in which luciferase expression was weaker and restricted to the tracheal region only. There was no sign of inflammatory response or toxicity of the PEG₁₂KL4 /mRNA complexes after single intratracheal administration. Overall, PEG₁₂KL4 is an excellent mRNA transfection agent for pulmonary delivery. This is also the first study that successfully demonstrates the preparation of inhalable dry powder mRNA formulations with in vivo transfection efficiency, showing the great promise of PEG₁₂KL4 peptide as a mRNA delivery vector candidate for clinical applications.