N, N-Dimethyl-4-Aminopyridine- and Aluminum Isopropoxide-Catalysed Ring-Opening Polymerizations of β-Butyrolactone for the Antimicrobial Oligohydroxybutyrate

Infectious pathogens pose serious threats to public health, necessitating the development of more antimicrobials. In this study, oligohydroxybutyrates were obtained through the catalyzed polymerization of <i>β</i>-butyrolactone using <i>N</i>, <i>N</i>-dimethyl-4-aminopyridine (DMAP) and aluminum isopropoxide [Al(O<i>i</i>Pr)₃] and applied as sustainable antimicrobial agents. The poly3-hydroxybutyrate (PHB) oligomers exhibited broad-spectrum antibacterial activities against both Gram-negative (<i>E</i>. <i>coli</i>) and Gram-positive (<i>S</i>. <i>aureus</i>) model bacteria. Additionally, PHB oligomers displayed robust (inhibiting rate: >95%) and rapid (action time: <20 min) antiviral activity against three notorious single-stranded RNA viruses, that is, influenza A virus (H1N1 and H3N2) and coronavirus (SARS-CoV-2). In particular, a comprehensive set of advanced experimental characterizations, including FT-IR, ¹H- and ¹³C-NMR, and H-ESI-MS/MS, was applied to analyze their chemical structures. The results confirmed the loss of terminal hydroxyl groups in the PHB intermediate and end products associated with theoretical calculations. These findings will also help provide deep insight into the major chain growth mechanism during the synthesis of PHB. The structural variations, which were treated as unwanted side reactions, were identified as a pivotal factor by deactivating the terminal hydroxy during chain growth. Their effective sterilization properties and degradability endowed the as-prepared PHB oligomers with a promising biomedical potential, including for use as disinfectants, sanitizers, and antiseptics.