| Chitosan(CS),an abundant natural amino polysaccharide,is attractive due to its a variety of biological activities such as antimicrobial activity,biocompatibility,atoxicity and biodegradability.Amphiphilic CS derivatives and their self-assembled nanomicelles have unique core-shell structure,and their hydrophobic core can act as containers for insoluble molecules such as drugs,active ingredients and fluorescent probes,while the hydrophilic shell has excellent water dispersibility.The amphiphilic chitosan-based amphiphilic self-assembly micelles demonstrated excellent safety,biocompatibility and stability.Therefore,chitosan-based amphiphilic self-assembly micelles have great potential in extending applications in food,pharmaceutical and other fields.In this thesis,a series of amphiphilic chitosan derivatives were constructed by chemical modification of macromolecule chitosan with biobased hydrophobic molecules.Their self-assembly behaviors and their applications in food safety detection and nutrientdelivery with natural active component were studied.Specifically,the thesis includes the following parts:1.A "turn-on" fluorescent sensing system based on CPs/ chitosan-graft-oleic acid(CS-graft-OA)micelles was developed for fast and visiable detection of aliphatic amines.The active materials in this system are fluorescent carboxylated polyfluorenes encapsulated in the self-assembled amphiphilic CS-graft-OA nanomicelles,which tend to identify amines through electrostatic interactions.It was interesting to find that a partial FRET fluorescence of the carboxylated polyfluorenes was observed when they were encapsulated in the micelles,and the FRET was significantly enhanced with the presence of trace amines,giving a visible "turn-on" fluorescence response.The CPs containing more carboxyl groups showed a higher sensitivity.We investigated the FRET ratio in respond to the increasing concentration of different aliphatic amines.A linear relationship was obtained with all of the aliphatic amines samples in the concentration range of 0–50 μM,showing this sensing system can also be used for quantitative detect trace aliphatic amines.This is very meaningful for fast food safety detection,because the time-consuming extraction and separtion steps can be saved.2.Novel amphiphilic chitosan grafted alpha lipoic acid(CS-graft-ALA)was successfully synthesized by graft copolymerization of CS and ALA,and its structure was confirmed with FT-IR and ~1H-NMR.This CS-graft-ALA copolymers were able to form self-assembled spherical nanomicelles in aqueous solution,with the particle size and CMC values determined be 116.0 nm and 0.0076 mg/m L,respectively.:Quercetin(Qu)was easily encapsulated into the core of CS-graft-ALA micelles.The self-assembly and drug loading properties of the micelles were strongly dependent on the polymer architecture and the drug feeding ratio.In the antioxidant study by DPPH method and FRAP method,the antioxidant activity of Qu was effectively enhanced when it was entrapped within CS-graft-ALA nanomicelles.Moreover,CS-graft-ALA nanomicelles can effectively improve the photo-stability and temperature-stability of Qu.The employment of CS-graft-ALA nanomicelles encapsulation provides more potential for improving and extending the actual applications of Qu.3.Amphiphilic chitosan grafted salicylic acid(CS-graft-SA)was synthesised by grafting copolymerization of salicylic acid and chitosan.This CS-graft-SA copolymers were able to form self-assembled spherical nanomicelles in aqueous solution,with the particle size and CMC values determined be 126.0 nm and 0.0145 mg/mL,respectively.Tea tree essential oil(TTO)was easily encapsulated into the core of s CS-graft-SA micelles.The self-assembly and drug loading properties of the micelles were studied and found strongly dependent on the polymer structure and the drug feeding ratio.The antioxidant abilities of TTO/ CS-graft-SA micelles were studied by DPPH method and FRAP method,showing that the antioxidant activity of TTO was effectively enhanced when it was entrapped within CS-graft-SA nanomicelles.Moreover,CS-graft-SA nanomicelles can effectively improve the salt stability and thermal stability of TTO.The employment of CS-graft-SA nanomicelles encapsulation provides more potential for developing effective and feasible antioxidants from natural products. |
