| To develop novel environmental stimuli-responsive smart materials and app-ly to drug delivery systems have become research frontier and hotspot.Further-more,the development of supramolecular hydrogels with pH-and thermal-sens itive properties is especially favored by the researchers.In this paper,throughthe chemical modification of chitosan(CS)by ?-CD and guest with nitrogen or aromatic structural unit,the pH-and thermal-sensitive supramolecular hydro-gels based on CB[7] and ?-CD host competitive interaction towards guest has been developed and are expected as novel intelligent materials applied to slow/controlled release.The main work is as follows:1.?-CD-CS(1?2?3)were synthesized by three different methods and studied by IR,UV-vis and 1H NMR spectroscopy,which showed that the largest apparent amount of grafting of ?-CD is 62.53?mol/g.Fc-Q-CS was prepared by Schiff base reaction between Quaternized Chitosan(Q-CS)and Fc-CHO and studied by IR,UV-vis and 1H NMR spectroscopy.Solubility experiment results indicated that Fc-Q-CS had good solubility.2.The Fc-Q-CS/?-CD-CS/CB[7] gel based on CB[7] and ?-CD host competitive interaction towards ferrocene guest has been constructed.The MBCS/?-CD-CS/CB[7]gel based on CB[7] and ?-CD host competitive interaction towards aromatic amine guest has been constructed,too.The host-guest interaction inclusion complexe between ?-CD of ?-CD-CS and guest with nitrogen or aromatic structural unit on the chain of chitosan was the driving force for the formation of Fc-Q-CS/?-CD-CS/CB[7and MBCS/?-CD-CS/CB[7] gels under acidic conditions.However,The nitrogen of guest on the chain was charged and the guest was encapsulated by CB[7] throughion–dipole interactions instead of ?-CD under alkaline conditions,at the last,the gels were destroyed.The main driving forces for gel-sol transitions were attributed to competitive host interaction between CB[7] and ?-CD towards guest,which was investigated by UV-Vis,IR and 1H NMR.Thermal stability of gels was analyzed by thermogravimetric method(TG)and differential scanning calorimetry method(DSC).The environmental scanning electron microscope(SEM)image of the gels displayed that gels formed a cross-linked network structure.Furthermore,in this work,we discovered that gels mentioned above had an interesting reversible pH-and thermo-sensitivity.3.Lincomycin was taken as the model drug and the vitro release studies o-f Fc-Q-CS/?-CD-CS/CB[7] supramolecular gel entrapped with Lincomycin were studied at various kinds of pH conditions(pH=1.2,4.0,6.8).The results reve-aled that raw drug of Lincomycin release fast under three different pH values and pH values couldn't influence the release behavior of Lincomycin.Within180 minutes,the cumulative release rate of Lincomycin was 96.18%(pH=1.2),95.01%(pH=4.0),90.24%(pH=6.8),respectively.While,the cumulative release ra te of Fc-Q-CS/?-CD-CS/CB[7] drug-loaded Fc-Q-CS/?-CD-CS/CB[7] supramolec-ular gel were 77.75%(pH=1.2)?67.42%(pH=4.0)?59.13%(pH=6.8)at 180 minu-tes respectively,and were 93.50%(pH=1.2)?77.02%(pH=4.0)?65.14%(pH=6.8)at 400 minutes respectively.The results showed that the Fc-Q-CS/?-CD-CS/CB[7]supramolecular gel system had obviously sustained-release for Lincomycin in vitro when pH was 6.8,and showed pH-responsive drug release characteristic.4.5-Fu was taken as the model drug and the vitro release studies of MBC-S/?-CD-CS/CB[7] supramolecular gel entrapped with 5-Fu were studied at vari-ous kinds of pH conditions(pH=1.2,4.0,6.8).The results revealed that raw d-rug of 5-Fu released fast under three different pH values and pH values could n't influence the release behavior of 5-Fu.Within 180 minutes,the cumulative dissolution rate of 5-Fu was 96.08%(pH=1.2),96.83%(pH=4.0),95.17%(pH=6.8),respectively.While,the cumulative release rate of MBCS/?-CD-CS/CB[7] drug-loaded supramolecular gel were 77.49%(pH=1.2)?73.78%(pH=4.0)?61.89%(pH=6.8)at 180 minutes respectively,and were 90.18%(pH=1.2)?87.60%(pH=4.0)?76.51%(pH=6.8)at 400 minutes respectively.The results showed that the MBCS/?-CD-CS/CB[7] supramolecular gel system had obviously sustained-release for5-Fu in vitro when pH was 6.8,and showed pH-responsive drug release charac-teristic. |
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