Abstract
Network formation of poly(γ-glutamic acid) (γPGA) having catechol structure at room temperature in aqueous media was examined, and its application to biocompatible adhesives was investigated. Carboxyl groups of γPGA was partially transformed to an activated succinmide ester form, SI-γPGA, by treatment with hydroxysuccinimide and watersoluble carbodiimide. Addition of 3-hydroxytyramine (DOPA) hydrochloride in γPGA in NaHCO3 solution gave DOPAmodified γPGA. On the other hand, immediate gelation was observed by addition of 4,7,10-trioxa-1,13-tridecanediamine (TODA) in a polymer aqueous NaHCO3 solution, which indicated formation of networked polymer by diamine crosslinking. Simultaneous addition of DOPA hydrochloride and TODA to the SI-γPGA solution caused rapid gelation of the polymer solution, which indicated the formation of networked γPGA partially modified with DOPA. Solutions of SI-γPGA/TODA/DOPA mixture and SI-γPGA/TODA mixture were put on the surface of a pig skin and covered with another pig skin and pressed for 24 h, respectively. The adhesion property was evaluated by mechanical tensile measurements. As a result, detaching force of SI-γPGA/TODA/DOPA sample was more than three times higher than that of SI-γPGA/TODA, indicating the high adhesion property of DOPA-modified γPGA.
