Studies Of Colorimetric Biosensors Based On Liposomes' Controlled-released System

Owning to its advantage of controlled-released,easy to modification,and preparation,liposomes have attracted a lot of attention in targeted therapy,fine chemical,analysis testing fields.In this study,horseradish peroxidase(HRP)-encapsulated liposomes have been prepared and used to develop sensitive,selective biosensors based on its controlled-released system.The main research work was as follows:1.Preparation of the biotin-tagged HRP-encapsulated liposomes by the enthanol injection method.The results showed that the liposomes have some advantages,such as easy to preparation,easy to modification,and biocompatibility.2.A colorimetric immunosensor for virus influenza H5N1 been developed which based on enzyme-encapsulated liposomes and immunoassay.In the presence of the target,the target was captured by capture antibody and then recognized by biotinylated detection antibody to form a sandwich immunocomplex.And then the biotinylated detection antibody is able to combine with biotin-tagged liposome through biotin-avidin-biotin linkage.The addition of the substrate(mixture of 3,3',5,5'-tetramethylbenzidine(TMB)and H2O2)resulted in the color change of the system from colorless to blue.Because HRP released from liposomes could catalyze H2O2 to generate · OH,and · OH could oxidize TMB to generate TMB+.As a consequence,the concentration of H5N1 can be observed by naked eyes easily or detected by UV-vis spectra.The results showed that the biosensor has the advantages of high selectivity,sensitivity,and practicability.3.A colorimetric aptasensor for ochratoxin A(OTA)based on enzyme-encapsulated liposomes has been developed.Magnetic beads and liposomes were covalently attached through the double strands which formed by hybridization of OTA aptamer and its complementary strands.In the present of OTA,OTA can competitively bind with aptamer due to their high affinity,leading the release of complementary strands and HRP-encapsulated liposomes.The addition of the substrate(mixture of TMB and H2O2)resulted in the color change of the system from colorless to blue.As a consequence,the concentration of OTA can be observed by naked eyes easily or detected by UV-vis spectra.4.Liposomes have ability to develop different kinds of colorimetric biosensor,and it is expected to play an important role in clinical medicine and food safety analysis.