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Biomolecule-Responsive Behavior of Smart Gels Having Biomoleclar Complexes as Reversible Cross-Links

Takashi Miyata, Kaori Okawa, Noriko Asami, and Tadashi Uragami. Faculty of Engineering, Kansai University, Suita, Osaka 564-8680, Japan

Stimuli-responsive gels that exhibit volume changes in response to environmental changes such as pH and temperature have many future opportunities as suitable biomaterials for designing smart systems in biomedical fields. We have prepared a variety of biomolecule-responsive gels that undergo volume changes in response to a specific biomolecule. This paper describes biomolecule-responsive behavior of biomolecule-cross-linked gels that were prepared using biomolecular complexes such as antigen-antibody complexes and DNA duplexes. The bioconjugated gels having antigen-antibody complexes as cross-linking points were prepared by copolymerization of acrylamide (AAm), N, N'-methylenebisacrylamide (MBAA) and antigen-antibody complexes having polymerizable groups. The antigen-antibody gels swelled immediately in the presence of a target antigen, but shrank gradually in its absence. The swelling ratio of the antigen-antibody gels was strongly dependent upon the antigen concentration. The antigen-responsive swelling of the antigen-antibody gels was due to a decrease in their cross-linking density by the dissociation of the antigen-antibody complexes. Furthermore, the bioconjutaged gels having DNA duplexes as cross-linking points were prepared by copolymerization of AAm, MBAA and DNA duplexes having polymerizable groups. The swelling ratio of the DNA-cross-linked gels increased immediately in a buffer solution containing a target DNA. The sequence of DNA in a buffer solution influenced swelling behavior of the DNA-cross-linked gels. Their DNA-responsive behavior can be explained by the dissociation of the DNA duplexes in the gels in the presence of target DNA. Such biomolecule-responsive gels have many potential applications as smart biomaterials for constructing drug delivery systems and sensor systems.