The Synthesis Of Amphiphilic Chitosan Derivatives And Their Application On Encapsulation Of Nanopatricles

The nanotechnology has resulted in active developments of a new emergingresearch area, which offers exciting opportunities for discovering new materials,processes, and phenomena. Semiconductor quantum dots (QDs) are emerging as anew class of fluorescent labels for molecular, cellular, and in-vivo imagingapplications, due to their narrow and size-tunable emission spectra, broad absorptionprofiles, and superior photostability. Nanoscale magnetic materials have their ownadvantages that provide many exciting opportunities in biomedical applications. First,they deliver controllable sizes ranging from a few up to tens of nanometers. Second,the nanoparticles can be manipulated by an external magnetic force. Third, magneticnanoparticles play an important role as MRI contrast enhancement agents. Recently,the active explorations of the applications of nanoparticles have advancedconsiderably, including biomedicine.In this paper, alkyl-chitosan derivatives（Octyl chitosan, Decyl chitosan）weresuccessfully synthesized via Schiff base reduction reaction of chitosan and n-octanalor n-Decanal, with chitosan acting as the backbone of the grafted copolymers. It wasconfirmed by characterization employing Fourier transform sample infraredspectroscopy (FT-IR) and1HNMR characterization. The size and distribution of thepolymeric micelle was determined by dynamic light scattering (DLS), as well theeffect of the amount of alkyl chains on the size of the hollow polymeric micelles. Theresult showed that with grafting level increasing, the size of those nanoparticlesdiminished accordingly.In the subsequent procedure, the N-octyl-N-mPEG-chitosan (OPEGC) wassythisised by the introduction of mPEG aldehyde to the Octyl chitosan. TheN-decyl-O,N-carboxymethyl chitosan was synthesised by the carboxy methylation ofDecyl chitosan. Moreover, critical micelle concentration (CMC) was determinedbased on I3/I1derived from emission spectrum afforded by fluorescence spectroscopy with pyrene as fluorescent probe. The CMC of OPEGC=2.032×10-2mg/mL; TheCMC of CMDCTS=4.90×10-3mg/mL.In the third chapter, water-soluble quantum dots (QDs), widely used asnanoprobe for medical application, were achieved by incorporation of QDs inside thepolymeric micelle core through the hydrophobic interaction between the alkyl chainligand capped on the QDs and the hydrophobic inner core of the polymeric micelles.The optical properties of OPEGC@QDs and CMDCTS@QDs were characterized byUV-Vis spectroscopy, fluorescence spectroscopy and the morphology of theirassembly formed in water were observed by AFM and TEM. The results indicatedthat the OPEGC@QDs and CMDCTS@QDs nanoparticles with narrow sizedistribution were prepared here, which represented good water solubility and highquantum yield.In the fourth chapter, the OPEGC@IO and CMDCTS@IO were obtained by thesimilar way of preparing chitosan@QDs. It was confirmed by characterizationemploying Fourier transform sample infrared spectroscopy (FT-IR). What’s morethe magnetic properties of chitosan@IO were characterized by vibrating samplemagnetometry (VSM), which shown that they were good superparamagnetic. TheDLS, AFM and TEM results indicated that the OPEGC@IO and CMDCTS@IOnanoparticles with narrow size distribution were prepared here, which representedgood water solubility.In the end of the work, MTT assay was performed to evaluate the cytotoxicity ofOPEGC, CMDCTS, OPEGC@QDs, CMDCTS@QDs, OPEGC@IO andCMDCTS@IO micelles against HepG2cells. The results show that the OPEGC orCMDCTS composite nanoparticles were low cytotoxicity and may be widely used inbiomedical in the future.