Study On The Hydrogels Of Fmoc-dipeptides

9-Fluorenylmethoxycarbonyl(Fmoc)protected dipeptides are ones of common intermediates in the synthesis of peptides.It was found that 9-Fluorenylmethoxy carbonyl(Fmoc)protected dipeptides have some advantages such as biocompatibility, biodegradability and drug effects,so the hydrogels formed by these dipeptides can be used in drug delivery,drug release,tissue engineering,chemical sensor and so on.In this paper,we chose N-hydroxysuccinimide as activator of carboxyl group and DCC as condensing agent,the N-hydroxysuccinimide ester of Fmoc-D-Alanine was synthesized in anhydrous dimethoxyethane solvent,then the ester was used as one of reactant provided carboxyl to react with another amino acids in ethanol and acetone mixture(V₁:V₂=4:1),at last,five Fmoc-D-Alanyl-dipeptides were synthesized. The structures of Fmoc-D-Alanyl-dipeptides are established by experimental technique UV,1H-NMR and FTIR,and the reaction mechanism was speculated according to the properties of the reactants and products.The character in gelled solvent of the above resulted Fmoc-D-Alanyl-dipeptides was studied,and the properties of the five Fmoc-D-Alanyl-dipeptides in rheology, morphology and microscopic arrangement was tested by the experimental technique Rheometer,TEM,SEM and CD.In addition,the effects of pH,the acid radical ion and the temperature to the hydrogels was studied.It was found that although the five Fmoc-D-Alanyl-dipeptides have the similar structure,the five gels formed by them are different in the mechanical property and morphology.Along with the size of side group increasing,the morphology of the gels changed from nanofiber to nanotube.According to the information from the above test,we speculated the mechanism of the hydrogels formation,.In addition,it was also found that the above four compounds can form hydrogels adjusted by different acids on the condition of pH＜5,the results of TEM show that the morphologies of hydrogels acidized by hydrochloride,nitric acid and sulfuric acid are not different.The result suggests that we can acidized the Fmoc-D-Alanyl-dipeptides solution by hydrochloride in the study of preparation hydrogel used in drug delivery,drug release and tissue engineering.The temperature of surroundings made great effect to the hydrogels,when the temperature arrived the T_g,the hydrogels can change into solution,but cooled to the room temperature,the hydrogels formed again. The results show that the hydrogels are thermosensitive reversible hydrogels.The research significance in this paper consists in synthesis of five Fmoc-D-Alanyl-dipeptides, prepared four Fmoc-D-Alanyl-dipeptides thermosensitive reversible hydrogels,finding the phenomenon of the side groups effects to the whole molecule.The results of our research provide some reference for drug delivery and enriched the database of drug delivery to a certain extent.