Abstract
A novel versatile biocompatible hydrogel of whey protein isolate (WPI) and two types of tannic acid (TAs) was prepared by crosslinking of WPI with TAs in a one-step method at high temperature for 30 min. WPI is one common protein-based preparation which is used for hydrogel formation. The obtained WPI-TA hydrogels were in disc form and retained their integrity after sterilization by autoclaving. Two TA preparations of differing molecular weight and chemical structure were compared, namely a polygalloyl glucose-rich extract-ALSOK 02-and a polygalloyl quinic acid-rich extract-ALSOK 04. Hydrogel formation was observed for WPI solutions containing both preparations. The swelling characteristics of hydrogels were investigated at room temperature at different pH values, namely 5, 7, and 9. The swelling ability of hydrogels was independent of the chemical structure of the added TAs. A trend of decrease of mass increase (MI) in hydrogels was observed with an increase in the TA/WPI ratio compared to the control WPI hydrogel without TA. This dependence (a MI decrease-TA/WPI ratio) was observed for hydrogels with different types of TA both in neutral and acidic conditions (pH 5.7). Under alkaline conditions (pH 9), negative values of swelling were observed for all hydrogels with a high content of TAs and were accompanied by a significant release of TAs from the hydrogel network. Our studies have shown that the release of TA from hydrogels containing ALSOK04 is higher than from hydrogels containing ALSOK 02. Moreover, the addition of TAs, which display a strong anti-cancer effect, increases the cytotoxicity of WPI-TAs hydrogels against the Hep-2 human laryngeal squamous carcinoma (Hep-2 cells) cell line. Thus, WPI-TA hydrogels with prolonged drug release properties and cytotoxicity effect can be used as anti-cancer scaffolds.
Highlights
Much attention has been paid to hydrogels in drug delivery
Which corresponds to the tannic acids (TAs)/whey protein isolate (WPI) ratios were 0.0375/0.075/0.15/0.30 in the hydrogels; a control sample without the TA addition was prepared
Concentrations in WPI hydrogels were selected and hydrogels with differing TAs contents were synthesized 1.5; 3.0; 6.0 and 12.0 mg per mL, which corresponds to the TA/WPI ratios were 0.0375/0.075/0.15/0.30 in the hydrogels. [27,28]
Summary
Much attention has been paid to hydrogels in drug delivery. In this regard, hydrogels must comply with principles such as biocompatibility, biodegradation, and non-toxicity. One common protein-based preparation used for hydrogel formation in the food industry is whey protein isolate (WPI), which we have recently begun to investigate as a hydrogel biomaterial for biomedical applications [1,2,3,4]. The process of whey protein aggregation consists of three stages, including conformational changes of the native protein structure, chemical reactions typically through disulfide bridges between intraand interchain bonds and physical interactions like hydrophobic interactions, which leads to aggregation clustering and the formation of a spatial gel network [8]. The increased comparison of ß-lactoglobulin allows to fabricate more elastic WPI hydrogels with far superior mechanical properties compered to hydrogels based on whey protein concentrate
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