Dopamine-ModifiedAlginate Beads Reinforced by Cross-Linkingvia Titanium Coordination or Self-Polymerization and Its Applicationin Enzyme Immobilization.

Twonovel kinds of dopamine-modified alginate beads were developedby using titanium(IV) coordination or self-polymerization, besidesthe conventional Ca2+ion cross-linking. Alginate was modifiedwith dopamine (AlgDA) via EDC/NHS chemistry. Fourier transforminfrared spectroscopy (FTIR) and circular dichroism (CD) characterizationconfirmed that dopamine was covalently attached preferentially tothe mannuronic acid residues of alginate; thus, gel-forming abilityof the as-prepared AlgDAwas well retained. The titanium(IV)coordination-reinforced alginate beads [Ca–Ti(AlgDA)] were prepared by cross-linking with Ti4+and Ca2+. Covalently cross-linking-reinforced alginate beads (Ca–AlgPDA) were also prepared by self-polymerization of dopamineand cross-linking with Ca2+. The swelling of Ca–AlgPDAand Ca–Ti(AlgDA) were both obviouslyinhibited, and the mechanical properties were enhanced by 3 timescompared to those of Ca–Alg beads. The as-prepared beads wereutilized for immobilization of alcohol dehydrogenase (YADH). The immobilizationefficiency of Ca–Ti(AlgDA) and Ca–AlgPDAreached up to 100% and 89%, respectively, both notablyhigher than that of Ca–Alg (67.4%). Stabilities of the immobilizedYADH in Ca–AlgPDAand Ca–Ti(AlgDA) toward pH, storage, and recycling were all improved compared withthose immobilized in Ca–Alg. [ABSTRACT FROM AUTHOR]