Preparations And Applications Of Self-Assembled Nanoparticles Based On Hydrophobically Modified Carboxymethyl Chitosan

Carboxymethyl chitosan (CMCS) was modified by coupling with linoleic acid (LA) or folate (FA) through the 1- ethyl- 3- (3- dimethylaminopropyyl)- carbodiimide- mediated reaction. The results of NMR confirm the successful modification.The hydrogel nanoparticles of LA modified CMCS (LCC) and FA modified CMCS (FCC) can be prepared after the sonication. The critical aggregation concentration (CAC) of the self-aggregate of hydrophobically modified chitosan was determined by measuring the fluorescence intensity of the pyrene as a fluorescent probe. The CAC values were in the range of 0.061 to 0.081 mg/ml. The average particle size and size distribution were determined by quasielastic laser light scattering with a mean. The average sizes of FCC and LCC were 267nm and 412nm. AFM and transmission electron microscopy (TEM) image of the nanoparticles showed that the well-formed nanoparticles with structural integrity formed after the sonication of FCC and LCC molecules.Bromelain can be loaded onto nanoparticles of LCC. Factors affecting the activity of the immobilized enzyme, including temperature, storage etc., were investigated in this study. The results showed that the stabilities of bromelain for heat and storage were improved after immobilization on nanoparticles. The Michaelis constant (Km) of the immobilized enzyme, was smaller than that of free enzyme which indicated that the immobilization could promote the stability of the enzyme and strengthen the affinity of the enzyme for the substrate.As drug delivery system, loading capacity (LC), loading efficiency (LE) and the in vitro release profiles of FCC or LCC was investigated by DOX as a model drug. Self-aggregated nanoparticles exhibited an increased EE and LE, decreased sustained release with an increasing ratio of the hydrophobic LA to hydrophilic CMCS. When the initially added amount of DOX versus the constant amount of FCC polymer (1 mg) was increased, the LC in the nanoparticles was gradually increased. However, the LE decreased from 91.78±0.39 to 72.04±0.13%. And we found that the greater was the amount of DOX added the slower was sustained release.The antitumor activity of the DOX-loaded FCC nanoparticles, DOX-loaded LCC nanoparticles and free DOX against the Hela cells was evaluated using MTT method at various DOX concentrations for various incubation times. The free nanoparticles show almost no effects on the cytotoxicity of cells. DOX-loaded FCC nanoparticles showed a comparable inhibition of the growth of cells to that of free DOX. However, the DOX-loaded nanoparticles exhibit significantly less inhibitory activity than DOX-loaded FCC nanoparticles or free DOX.