Optimization and Development of Albumin–Biopolymer Bioconjugates with Solubility-Improving Properties

Abstract

Bioconjugation is an emerging field in the food and pharmaceutical industry. Due to its biocompatibility and high ligand binding capacity, albumin is widely used in modern drug delivery systems. However, the protein is sensitive to environmental stresses; albumin conjugates, on the other hand, have improved functional properties. Biopolymers are gaining interest due to their biodegradability and safety, compared to synthetic polymers. In this study, albumin–biopolymer bioconjugates were prepared by nonenzymatic Maillard reaction at 60 °C and 80% relative humidity. This nonenzymatic conjugation takes place between reducing sugars and available amino groups of a protein in certain conditions. The optimal molar ratio and time for the conjugation were studied by several investigation methods, including circular dichroism and fluorescence spectroscopy, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and determination of available amino groups with ortho-phthaldialdehyde (OPA) assay. All of the measurements provided evidence for the covalent bonding of albumin and biopolymers, resulting in bioconjugates. Based on the results, a higher molar ratio and longer time are necessary to complete the reaction with the available amino groups. However, the optimal parameters are specific to each given biopolymer. The rheological behavior of the conjugates is characteristic of the initial biopolymer, which can be useful in drug development. Moreover, both the physical characteristics of albumin and the solubility-improving capacity were enhanced. Therefore, the potential use of albumin–biopolymer bioconjugates in the pharmaceutical industry could be considered.

Reproducible and controlled peptide functionalization of polymeric nanoparticles

“…When considering the OPA assay, the reagent reacts with the primary amines present on the peptide to produce a fluorometric byproduct (KangLee and Drescher, 1978;Frank et al, 1985). When the peptide sequence includes multiple primary amines, the unconjugated primary amines are used to quantify the number of peptides on the polymer chains or bioconjugates (Mu et al, 2010;Wu et al, 2012;Li et al, 2014;Ding et al, 2017;Hou et al, 2019;Papay et al, 2021;Wu et al, 2021;Liu et al, 2022). As crosslinking converts these remaining primary amines to secondary amines, the assay produces a falsenegative result even though the peptide is chemically conjugated to the polymer backbone.…”