Study On The Preparation Of Chitosan Derivatives And Their Applications In Drug Delivery

Chitosan，the second abundant polysaccharide existing in nature, is a derivative from chitin.Chitosan has many distinctive properties such as biocompatibility, biodegradability,antimicrobial activity, nontoxicity and remarkable affinity to proteins. However, owing to itsinsoluble either in water or in organic solvents except aqueous acids, application of chitosan islimited. To overcome this drawback, chitosan was converted to water-or organicsolvents-soluble derivatives using chemical modification for further applications.1. Folate polyethylene glycol conjugated carboxymethyl chitosan for tumor targeteddelivery of5fluorouracilIn this study, folate acid (FA) was conjugated to carboxymethyl chitosan (CMCS) through apolyethylene glycol (PEG) spacer to form CMCS-PEG-FA. The resulting conjugates wereconfirmed by1H nuclear magnetic resonance(1H NMR) and infrared spectroscopy (FT-IR)detection. The cytotoxic effects of CMCS-PEG-FA and CMCS-PEG-FA-5-fluorouracil (5-FU)were determined by crystal violet stain assay. Hela cell line, which has high surface folatereceptors, and A549cell line, which contains low amount of surface folate receptor, were used todetect the5-FU delivery ability by CMCS-PEG-FA with the use of3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylterazoliu bromide analysis (MTT). The MTT resultsrevealed that the cytotoxicity of (CMCS-5-FU)-PEG-FA on Hella cells was greater thanCMCS-5-FU, suggesting that folate receptor-mediated endocytosis might improve the cellularuptake efficiency of5-FU-loaded CMCS-PEG-FA.2. Preparation and characterization of N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride（HTACC）/multi-walled carbon nanotubes(MWCNTs) compositematerialIn this study, self-assembly between water-soluble GTMAC-grafted chitosan derivatives(HTACC) and multiwalled carbon nanotubes(MWCNTs) has been successfully developed andthe resultant products possessed excellent dispersity. HTACC was characterized by FT-IR,1H-NMR, X-ray diffraction(XRD) and DSC. Spontaneous self-assembly complex of HTACCand MWCNTs was confirmed by FT-IR, thermogravimetric analysis(TGA), zeta potential, andtransmission electron microscopy(TEM) studies. TEM analysis revealed that the diameter ofpristine MWCNTs was9.5nm whereas the diameter of HTACC coated MWCNTs was14.7nm. The measured zeta potential of HTACC coated MWCNTs was+7.37mv. TGA resultdemonstrated that the MWNT/HTACC consisted of about20wt%HTACC. As a novelderivative of the MWNTs, this HTACC coated MWCNTs showed a remarkable stabilitywithout any observable aggregation after centrifugation at12,000rpm for20minutes.3. Preparation and characterization of magnetic targeted chitosan derivatives drug carrierIn situ preparation of magnetic chitosan derivatives/Fe3O4composite nanoparticles wasemployed, resulting a uniform single-crystal and well-dispersible product. The resultantmagnetic Fe3O4nanoparticles were characterized with FT-IR, X-RD, TEM, zeta-potentialmeasurement and vibrating sample magnetometry (VSM). The synthetic protocol described inthis paper yielded materials, composed magnetite cores with the mean crystallite size among10nm and12nm. The mean hydrodynamic diameters of these particles varied from68nm to162nm, and the zeta potentials of the materials varied from highly positive+40.3mV to negative–56.3mV, depending on the coating material used. The magnetic nanoparticle concentration interms of iron content varied from4.56mg/L to5.09mg/L and the magnetic nanoparticleconcentration in terms of dry weight was6.28mg/mL～9.07mg/mL. The hysteresis loops ofFe3O4, carboxymethyl chitosan magnetic nanoparticles(Fe3O4/CMCS) and2-hydroxypropyltrimethyl ammonium chloride chitosan magnetic nanoparticles (Fe3O4/QCTS)nanoparticles showed a ferromagnetic behavior with saturation magnetization of59.1,66.2and55.8emu/g, respectively. TEM results demonstrated a spherical or ellipsoidal morphologywith an average diameter of10-12nm. The adsorbed layer of QCTS and CMCS on themagnetite surface was confirmed by FT-IR. TGA results indicated that the Fe3O4/QCTSconsisted of about16wt%QCTS and the CMCS content was about6%in Fe3O4/CMCS. XRDillustrated that the resultant magnetic nanoparticles had a spinel structure and lastly VSM resultsshowed the modified magnetic Fe3O4nanoparticles were superparamagnetic. The adsorptionmechanism of QCTS and CMCS onto the surface of Fe3O4nanoparticles was believed to be theelectrostatic and coordination interactions, respectively. The mechanisms of both QCTS andCMCS stabilizing the suspension of Fe3O4nanoparticles were supposed to be electrostaticrepulsion.4. The preparation and characterization of chitosan-grafted-β-cyclodextrinThe conjugates of β-cyclodextrin with chitosan were obtained by the reaction ofβ-cyclodextrin with p-nitrobenzenesulfonyl chloride, following by grafting to chitosan. Thepurified conjugate was characterized with FT-IR,1H NMR, XRD and nitrogen analysis. In theinfrared spectra of chitosan-β-cyclodextrin, the peak at1020cm-1was ascribed to-pyanyl vibration of β-cyclodextrin and the peak at1050cm-1was due to β-pyanyl vibration of chitosan.Protons of both chitosan and cyclodextrins appeared in1H NMR of chitosan-β-cyclodextrinconjugate, indicating β-cyclodextrins was grafted to chitosan successfully. The XRD resultindicated that the peak at2θ=10°disappeared and the peak at2θ=20°decreased greatly,suggesting that β-cyclodextrin was grafted to2-position amino-group in the unit of chitosan.Nitrogen analysis demonstrated that the substitution of β-cyclodextrin was13%.