Boronic acids as efficient cross linkers for PVA: synthesis and application of tunable hollow microspheres in biocatalysis

Herein is reported an innovative and reproducible systemic approach for the fabrication of customized 3D hollow microspheres of polyvinyl alcohol (PVA) based on the use of aromatic boronic acids (ABAs) as crosslinkers. A dedicated experimental set-up was developed to enable microsphere formulation. Most of the boronic acids tested were able to produce hollow microspheres. Depending on the ABA used and the production conditions, hollow PVA/ABA microspheres with different morphologies, mass transfer characteristics and unprecedented thermal (up to 121 °C) stability were obtained. The crosslinking temperature proved to be an operational parameter to control membrane thickness. The hollow microspheres were evaluated in biocatalysis, with naringin hydrolysis as model system, using encapsulated naringinase. The results highlighted a naringinase high operational stability, namely in PVA microspheres crosslinked with 1,4-phenylenediboronic acid and with phenylboronic acid, with no evident loss of activity throughout seven consecutive runs, theoretically resulting in an infinite half-life.