A series of pH-responsive random copolymers comprised of 2-hydroxyethyl methacrylate (HEMA) and tertbutyl carbamate (Boc)-protected phenylalanine methacryloyloxyethyl ester (Boc-Phe-EMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in N,N'-dimethylformamide (DMF) at 70°C. The synthesized copolymers were comprehensively characterized using a combination of techniques, including 1 H NMR, FT-IR spectroscopy and size exclusion chromatography (SEC). Reactivity of each monomers towards controlled radical polymerization was evaluated by determining the reactivity ratios by virtue of extended Kelen-Tüdös method at high conversions revealed the higher reactivity of non-modified HEMA (r HEMA = 1.03) in contrast to Boc-Phe-EMA (r Boc-Phe-EMA = 0.48). Furthermore, the expulsion of the Boc-groups resulted copolymers with ionizable pendant primary ammonium and hydroxyl groups. To understand the glass transition behaviours of homo-and co-polymers, differential scanning calorimetric (DSC) measurements were carried out. The effect of HEMA content on the pH-sensitivity of the copolymers in aqueous medium was investigated through turbidity measurements. Finally, the counteranion exchange from trifluoroacetate to chloride provided copolymers with enhanced water solubility and unaltered phase transition pH.

Due to health and environmental hazards, there is an increased desire to rely on sustainable resources that are biocompatible, biodegradable, and safe for human administration. Herein, the present study explores bioconjugate efficacy as a potential anti-stain and green antibacterial additive in toothpaste formulation using GRAS (generally regarded as safe) and Food and Drug Administration (FDA)-approved ingredients. In this study, a series of conjugated polymers were synthesized using sodium alginate and alendronic acid and are labeled as SA-ALN amide and SA-ALN ester. Spectroscopic techniques thoroughly characterized the synthesized conjugated polymers. These synthesized polymers were adsorbed onto hydroxyapatite (HAP, a tooth model) to evaluate its practical application as anti-stain and reduce bacterial attachment. The adsorption of the conjugate polymers on the HAP surface was confirmed by Raman spectra and Fourier transform infrared spectroscopy (FTIR). The anti-stain test revealed significant whitening benefits for coated hydroxyapatite (HAP) tiles over uncoated tiles. The antibacterial activity of conjugated polymers toward E. coli (Gram-negative) and S. mutans (Gram-positive, bacteria responsible for tooth decay) strain showed 2.5 log reduction and 1.5 log reduction, respectively. Among the conjugated polymers, the SA-ALN-ester showed slightly higher antibacterial activity against E. coli as well as S. mutans strain relative to the SA-ALN amide product due to the presence of a free amine group in the former. Further, we carried out the in vitro cytotoxicity test of the conjugated polymers using gingival fibroblasts and pre-osteoblasts and the study demonstrated that the synthesized conjugates are cytocompatible in nature. Thus, this study revealed that the proposed work might provide insights into sustainable oral hygiene.