Preparation Of Soluble Carbon Nanotubes Modified Hydrogel Drug Carrier

Since their discovery in 1991,Carbon nanotubos(CNTs)have become the research focus in chemistry,physics,material science and biomedicine.CNTs have a lot of potential applications in the future Hi-Tech field due to their special mechanical,electronic,chemical properties and unique one-dimensional tube structures.However,CNTs are chemical inertia and cannot dissolve in general organic solvents, which hind their researches and applications.Moreover,it has been reported that CNTs' toxicity could be reduced by improving their solubility.Here biomacromolecule chitosan was used to modify carbon nanotubes to improve their solubilities.CS-CNT/CS semi-IPN hydrogels were prepared and their structure and properties were studied.The main contents of this study are shown as follows:(1)CNT-CS was prepared by two steps through first oxidation of multiple-walled carbon nanotubes using 70%HNO₃ and then amidation of the oxidized products under microwave irradiation.The two processes could be completed in one hour.Purification of products was achieved by twice adjusting of pH value of the solution and centrifugation in succession,pure chitosan-grafted multiple-walled carbon nanotubes were obtained as final products.(2)The chemical structure of chitosan-grafted multiple-walled carbon nanotubes was characterized by IR and UV spectroscopy.Their morphology was characterized by transmission electron microscopy (TEM),and the content of CS was analyzed by TGA.Results show that -COOH,C=O groups were successfully generated.Chitosan has been covalently grafted to the MWCNTs through the amide-acyl bonding.(3)A series of CS-CNT/CS semi-IPN hydrogels were prepared by a pre-freezing and freeze-drying technique sequentially using glutaraldehyde as a crosslinker.The mechanical properties of all hydrogels were tested.Equilibrium water retention and equilibrium swelling ratio of hydrogels was studied in the buffer solutions with different pH values.Contrast with the normal CS hydrogel,the mechanical strength of these semi-IPN hydrogels was remarkably improved,while the pH sensitivities were well preserved.(4)The swelling and deswelling kinetics of CS-CNT/CS semi-IPN hydrogels were studied.When CNT-CS composites were added into CS hydrogels,the swelling property and deswelling property of CS-CNT/CS semi-IPN hydrogels can be preserved well.Meanwhile,it showed excellent pH sensitivity as the the normal CS hydrogel.Deswelling ratios were lower in strong acid and strong alkaline buffer solutions than in neuter buffer solutions.The effect of the amount of CNT-CS on the pH sensitivity was not remarkable.Under acid conditions,the kinetic exponent of hydrogel approximate to 1 and the swelling mechanism isⅡstyle.The other kinetic exponent is between 1 and 0.5 and the transport mechanism belongs to non-fickian.(5)Comparing to normal hydrogels,CS-CNT/CS semi-IPN hydrogels containe 10%CS-CNT composites(C10)and can be used as drug delivery system for model drugs-PZFX.It was found that the loading ratio of hydrogels is huge.Drug releasing ability of hydrogels CO is beginning with a burst,while hydrogels C10 release drugs slowly.It is proved that hydrogels C10 could prolong drug releasing time up to one week.