Integration of poly(ethylene glycol) in N-fluorenylmethoxycarbonyl-l-tryptophan hydrogel influencing mechanical, thixotropic, and release properties.

Polyethylene glycol (PEG) is incorporated to improve the mechanical properties of N-fluorenylmethoxycarbonyl-l-tryptophan (FT) hydrogel producing the hybrid (FTP) gels designated as FTP1, FTP2.5, etc. having PEG concentrations of 0.05 and 0.125% (w/v), respectively. Both the FT and FTP1 gels exhibit fibrillar network morphology; the fibers of the FTP1 gel are thinner than those of the FT gel. FTP gels exhibit a magnificent improvement in mechanical properties, and the storage and complex moduli increase with a maximum of ∼2800% for the FTP2.5 gel. Creep recovery experiment exhibits a maximum strain recovery of 90% for the FTP1 gel. The thixotropic property is observed for both FT and FTP gels and the rate of recovery increases with increase of PEG concentration; the latter acts as a molecular adhesive to the gel fibers bringing back the network structure easily. Gelation of FT causes a 5-fold increase of fluorescence intensity due to molecular aggregation, and with increase of FT concentration the ratio of fluorescence intensities at 470 and 395 nm increases. Exploiting the thixotropic property of FT and FTP hybrid gels, doxorubicin (DOX) is successfully encapsulated, and tunable release of DOX using appropriate amount of PEG in the gel matrix under physiological conditions is observed.