Novel antigen responsive hydrogels were prepared by using polymerizable antibody Fab′ fragment from monoclonal anti-fluorescein BDC1 antibody (IgG2a). To form Fab′ containing hydrogels, the polymerizable Fab′ fragment was copolymerized with N-isopropylacrylamide (NIPAAm) and N,N′-methylenebis(acrylamide) (MBAAm; crosslinker) using redox initiators. The thermosensitivity of the hydrogels decreased with increasing Fab′ fragment content. The antigen responsiveness of the hydrogels depended on the Fab′ content, pH, and temperature. When the hydrogels were alternately exposed to antigens fluorescein (FL) and polyamidoamine dendrimer (PAMAM)-fluorescein (FD), significant reversible volume changes were observed for the hydrogel containing 50% (w/w) Fab′ fragment at 33.7 and 36.8 °C in acetate buffer (10 mM, pH 5.0), respectively, but not at 27.7 °C or in PBS buffer (10 mM, pH 7.4). No noticeable reversible volume changes were observed with pure PNIPAAm hydrogel and the gel containing 10% (w/w) Fab′ fragment.
Structure of Fab′ containing hydrogels.