Polyvinylamine-g-galactose is a route to bioactivated silica surfaces

Enrichment of sialic acid-containing casein glycomacropeptide in protein hydrolysates using phenylboronic acid-functionalized mesoporous silica nanoparticles

Glycomacropeptide (GMP) is a bioactive peptide of high value, rich in glycosylation sites and with physiological and dietary therapeutic value. The enrichment and detection of GMP facilitates the accurate quantification and the identification of adulteration of GMP in food products. In GMP, sialic acid is an abundant glycosyl group and is mainly located at the end of the sugar chain. Here, we propose a novel GMP enrichment strategy based on the affinity of sialic acid for phenylboronic acid groups that shift with environmental pH. As an enrichment material, mesoporous silica nanoparticles were progressively modified with aminopropyl and phenylboronic acid groups. The developed material showed excellent selectivity for sialic acid in the presence of galactose and fucose as interferents. The adsorption behavior of sialic acid-containing GMP fits the Langmuir adsorption model, offering a recovery of 71.72% (in terms of sialic acid content) and a GMP relative purity of 0.957. Results from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography confirm that the enriched GMP contains almost no other unexpected proteins and peptides, indicating that the developed strategy holds promise for purifying GMP in various dairy systems.

Phenylboronic Acid-polymers for Biomedical Applications

Background:

Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area.

Methods:

We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications.

Results:

We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning.

Conclusion:

The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Phenylboronic Acid-Functionalized Layer-by-Layer Assemblies for Biomedical Applications

Recent progress in the development of phenylboronic acid (PBA)-functionalized layer-by-layer (LbL) assemblies and their biomedical applications was reviewed. Stimuli-sensitive LbL films and microcapsules that exhibit permeability changes or decompose in response to sugars and hydrogen peroxide (H₂O₂) have been developed using PBA-bearing polymers. The responses of PBA-modified LbL assemblies arise from the competitive binding of sugars to PBA in the films or oxidative decomposition of PBA by H₂O₂. Electrochemical glucose sensors have been fabricated by coating the surfaces of electrodes by PBA-modified LbL films, while colorimetric and fluorescence sensors can be prepared by modifying LbL films with boronic acid-modified dyes. In addition, PBA-modified LbL films and microcapsules have successfully been used in the construction of drug delivery systems (DDS). Among them, much effort has been devoted to the glucose-triggered insulin delivery systems, which are constructed by encapsulating insulin in PBA-modified LbL films and microcapsules. Insulin is released from the PBA-modified LbL assemblies upon the addition of glucose resulting from changes in the permeability of the films or decomposition of the film entity. Research into insulin DDS is currently focused on the development of high-performance devices that release insulin in response to diabetic levels of glucose (>10 mM) but remain stable at normal levels (~5 mM) under physiological conditions.

Far beyond primary poly(vinylamine)s through free radical copolymerization and amide hydrolysis

Copolymers bearing various amino groups of predictable compositions are made available through radical copolymerization followed by optimized amide hydrolysis.

Polyvinylamine: a tool for engineering interfaces

With the highest content of primary amine functional groups of any polymer, polyvinylamine (PVAm) is a potent tool for the modification of macroscopic and nanoparticle surfaces. Based on the free radical polymerization and subsequent hydrolysis of N-vinylformamide, PVAm is prepared as linear polymers (0.8 kDa to >1 MDa), microgels, macrogels, and copolymers. The amine groups serve as reaction sites for grafting PVAm to surfaces and for the preparation of derivatives. Coupling low-molecular-weight molecules and oligomers gives PVAm-X, where X includes hydrophobes, carbohydrate oligomers, proteins, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), phenylboronic acids, and fluorocarbons. This contribution highlights the use of PVAm and PVAm-X to modify solid surface properties. Where possible, the PVAm properties and applications as an interfacial agent are compared to those of linear polyethylenimine, polyallylamine, and chitosan.