A Simple and Efficient Method for Synthesis of Carboxymethylated Polyethyleneglycol

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.

Oscillating Magnetic Field Regulates Cell Adherence and Endothelialization Based on Magnetic Nanoparticle-Modified Bacterial Cellulose

Despite the widely explored biomaterial scaffolds in vascular tissue engineering applications lately, no ideal platform has been provided for small diameter synthetic vascular grafts mainly due to the thrombosis issue. Endothelium is the only known completely non-thrombogenic material; so, functional endothelialization onto vascular biomaterials is critical in maintaining the patency of vascular networks. Bacterial cellulose (BC) is a natural biomaterial with superior biocompatibility and appropriate hydrophilicity as potential vascular grafts. In previous studies, surface modification of active peptides such as Arg-Gly-Asp (RGD) sequences onto biomaterials has been proven to achieve accelerated and selective endothelial cell (EC) adhesion. In our study, we demonstrated a new strategy to remotely regulate the adhesion of endothelial cells based on an oscillating magnetic field and achieve successful endothelialization on the modified BC membranes. In details, we synthesized bacterial cellulose (BC), magnetic BC (MBC), and RGD peptide-grafted magnetic BC (RMBC), modified with the HOOC-PEG-COOH-coated iron oxide nanoparticles (PEG-IONs). The endothelial cells were cultured on the three materials under different frequencies of an oscillating magnetic field, including "stationary" (0 Hz), "slow" (0.1 Hz), and "fast" (2 Hz) groups. Compared to BC and MBC membranes, the cells on RMBC membranes generally show better adhesion and proliferation. Meanwhile, the "slow" frequency of a magnetic field promotes this phenomenon on RMBC and achieves endothelialization after culture for 4 days, whereas "fast" inhibits the cellular attachment. Overall, we demonstrate a non-invasive and convenient method to regulate the endothelialization process, with promising applications in vascular tissue engineering.

Synthesis and facile end-group quantification of functionalized PEG azides

Azido-functionalized poly(ethylene glycol) (PEG) derivatives are finding ever-increasing applications in the areas of conjugation chemistry and targeted drug delivery by their judicious incorporation into nanoparticle-forming polymeric systems. Quantification of azide incorporation into such PEG polymers is essential to their effective use. 1H Nuclear Magnetic Resonance (NMR) analysis offers the simplest approach; however, the relevant adjacent azide-bearing methylene protons are often obscured by the PEG manifold signals. This study describes the synthesis of 1,2,3-triazole adducts from their corresponding PEG azides via a convenient, mild click reaction, which facilitates straightforward NMR-based quantitative end-group analysis.This method was found to be compatible with many examples of bifunctional azido PEGs with molecular weights ranging from 2 to 18 kDa bearing a variety of functional groups. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2888-2895.

Coating of carboxymethyl dextran on liposomal curcumin to improve the anticancer activity

Coating of carboxymethyl dextran (CMD) on the liposome for improved anticancer activity by enhancing the cellular uptake.

Preparative purification of polyethylene glycol derivatives with polystyrene-divinylbenzene beads as chromatographic packing

A clear and powerful chromatographic approach to purify polyethylene glycol derivatives at a preparative scale was reported, which was based on the polystyrene-divinylbenzene beads with ethanol/water as eluants. The validity of this method was verified with the reaction mixture of mPEG-Glu and mPEG propionaldehyde diethylacetal (ALD-PEG) as the model. The target products were one-step achieved with the purity of >99% on the polymer resins column at gram scale. The method developed was free from such disadvantages as utility of toxic solvent and narrow application scope, which was combined with conventional approaches. The method developed provided an appealing and attractive alternative methods for purification of PEG derivatives at a preparative scale.

Investigation on PEGylation strategy of recombinant human interleukin-1 receptor antagonist

Although PEGylation is a potential approach to prolong the half-lives and reduce the dosing frequency of therapeutic proteins, conjugation behaviors of polymer have pivotal effects on the remaining bioactivities of the derivatives. In this study, the PEGylation strategy of recombinant human interleukin-1 receptor antagonist was investigated. The random conjugation of polyethylene glycol to amino groups on the protein resulted in a severe loss of activity and only retained 9.8% of the activity. In contrast, the PEGylation at the thiol groups had moderate effects on the bioactivity of protein and 40% of activity was conserved. The results suggested that the thiol-target PEGylation was more beneficial for IL-1ra.