pH-sensitive gallol-rich chitosan hydrogel beads for on-off controlled drug delivery.

Malignant tumors have emerged as a serious health issue, and the interest in developing pH-sensitive polymers for site-specific drug delivery has increased. The physical and/or chemical properties of pH-sensitive polymers depend on the pH, and thus, drugs can be released by cleaving dynamic covalent and/or noncovalent bonds. In this study, gallic acid (GA) was conjugated to chitosan (CS) to prepare self-crosslinked hydrogel beads containing Schiff base (imine bond) crosslinks. The CS-GA hydrogel beads were formed by the dropwise addition of the CS-GA conjugate solution into a Tris-HCl buffer solution (TBS, pH 8.5). The pH-sensitivity of pristine CS was significantly enhanced following the introduction of GA moiety, and as a result, the CS-GA hydrogel beads swelled more than approximately 5000 % at pH 4.0, indicating an excellent swelling/deswelling ability of the beads at different pH (pH 4.0 and 8.5). The reversible breakage/recovery of the imine crosslinks in the CS-GA hydrogel beads was confirmed through X-ray photoelectron spectroscopic and rheological studies. Finally, Rhodamine B was loaded onto the hydrogel beads as a model drug to investigate the pH-sensitive drug release behavior. At pH 4, the drug was released up to approximately 83 % within 12 h. The findings indicate that the CS-GA hydrogel beads have great potential as a drug delivery system that is sensitive to acidic tumor sites in the body.

Ecofriendly poly(3-hydroxybutyrate-co-4-hydroxybutyrate) microbeads for sanitary products.

In the past, plastic microbeads (MBs) were added to personal healthcare products to improve the cleaning and exfoliating effects, but these have been withdrawn owing to their non-degradable nature and contribution to the pollution of marine environment, especially that caused by the adsorption of persistent organic pollutants (POPs) on MBs. Therefore, natural biodegradable alternatives are being developed, but these often do not exhibit sufficient performance to replace non-degradable MBs. In this study, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB-4HB), a biodegradable aliphatic polyester, was used to prepare MBs via melt-electrospraying. We carried out the rheological characterization of P3HB-4HB with respect to melting temperature, and the melt-electrospray process was optimized to prepare MBs having sizes similar to those of commercially available MBs. Furthermore, the adsorption properties of the P3HB-4HB MBs for POPs were investigated. Unlike commercial MBs, the P3HB-4HB MBs adsorbed significantly fewer contaminants owing to their smooth and regular surfaces. Finally, a cleansing product containing P3HB-4HB MBs was prepared to evaluate their cleaning ability, and we found that the MB-based product could remove dirt and contaminants that were not easily removed by water alone. Thus, the biodegradable P3HB-4HB MBs have great potential for use as sustainable additives for cosmetic products for skin exfoliation.