| Chitosan and Poly D,L-lactide-co-glycolide(PLGA)-based nano-materials have been successfully developed as drug delivery systems due to sustained drug-release property. PLGA-based nanoparticulate formulations, designed to bead ministered orally, topically, subcutaneously, or transmucosally have the advantage of supplying a continuous amount of drug over a long period of time. However, the non-specific interaction with cells and proteins and lack of suitable function groups for efficient covalent conjugation obstructed its application. Physical and chemical modification of PLGA nanoparticles were studied for practical requirements. Chitosan, as a natural biodegradable copolymer of N-acetyl glucosamine and D-glucosamine, has been widely used in pharmaceutical and drug delivery systems for its favorable biological properties, such as biodegradability, biocompatibility, low toxicity, hemostatic, bacteriostatic, fungistatic, anticancerogen, and anticholesteremic properties. Modification of reactive groups (-NH2) in chitosan molecule such as carboxymethylation and quaternary ammonium salt modification could improve its water solubility and biocampatibility.PLGA nanoparticles were surface modified with chitosan by adsorption or covalent binding, both of which involved emulsification solvent evaporation and showed a unitary structure. The surface-modified structure of CHS-PLGA nanoparticles limited its applications in drug encapsulation and delivery. In order to improve the preparation and properties of CHS-PLGA nanoparticles, novel self-assembeled CHS-PLGA nanoparticles were prepared and studied.In the present study, surfaced modified Chitosan-PLGA nanoparticles (C-NPs) and self-assembled chitosan-PLGA nanoparticles (G-NPs) were prepared. The naked PLGA NPs were served as control. Three kinds of differently structured nanoparticles were prepared and characterized by the laser light scattering technique, transmission electron microscopy (TEM), FT-IR spectroscopy and elemental analysis. Successful conjugation of chitosan to the PLGA particles was confirmed by FT-IR spectroscopy and elemental analysis. These nanoparticles all showed regularly spherical shape with mean diameters as191.3±3.6nm,211.9±13.2nm and187.5±17.6nm for PLGA NPs, C-NPs and G-NPs, respectively. Their zeta potentials were-22.4±1.31mV,-8.7±0.45mV,-3.1±0.12mV, respectively.The hydrolytic erosion of PLGA, C-NPs and G-NPs and its influence on the release of DOX from those differently structured nanoparticles under acidic (pH3.8) and physiological (pH7.4) conditions were investigated. The process of hydrolytic erosion of the nanoparticles with time was evaluated by ultra high-pressure liquid chromatographic (UHPLC) analysis. Both C-NPs (15.3%PLGA remained after two weeks, pH7.4) and G-NPs (3.7%PLGA remained after two weeks, pH7.4) had higher hydrolysis rate than PLGA NPs (18.4%PLGA remained after6weeks, pH7.4), with G-NPs showing the highest rate in hydrolysis due to the incorporation of chitosan and its self-assembled structure. Self-assembling properties and controllable biodegradability of G-NPs indicated that it could be a promising drug delivery carrier for tumor drug delivery.Doxorubicin (DOX) was efficiently loaded into the nanoparticles and showed sustained release in PBS at different pH. PLGA NPs had higher drug-loading content (DL%) and encapsulation efficiency (EE%) for its hydrophobic property and unmodified structure. At pH7.4, the burst release of PLGA particles at12h was57.28%, while it was43.44%and40.47%for C-NPs and G-NPs, respectively. The cumulative release rate of DOX from PLGA NPs, C-NPs and G-NPs after72h was60.03%,56.56%and62.85%, respectively. Presence of chitosan in the C-NPs reduced the burst release of the drug and accelerated the erosion rate of nanoparticles. Of the three kinds of nanoparticles, G-NPs had the fastest erosion rate in PBS for its homogenous structure, which lead to the highest the cumulative release rate of DOX. And the nanoparticles showed increased erosion rate and cumulative drug release at lower pH. The release profile of DOX from nanoparticles was closely related to nanoparticle erosion except for the initial burst release.Furthermore, the biocompatibility of NPs was also investigated. Three kinds of nanoparticles showed low hemolysis rate and BSA adsorption rate. MTT assay showed that they were nontoxic and biocompatible to MCF-7cells.The in vitro cellular uptake and growth inhibition of C-NPs and G-NPs were studied. Both the fluorescence microscopy and quantitative determination showed that C-NPs and G-NPs can be effectively endocytosed by MCF-7cells, while no significant difference in uptake efficiency of two nanoparticles. The quantitative determination of cell growth inhibition showed that the drug-loaded C-NPs and G-NPs in low concentrations1-4μg/ml, had higher cell growth inhibition rate than free doxorubicin and drug-loaded PLGA nanoparticles carrier. The drug-loaded nanoparticles of growth inhibition for MCF-7cells were time and concentration dependent. The in vitro experimental results demonstrated that G-NPs were favorable for tumor cell phagocytosis and drug control release.Based on the above considerations, G-NPs have good biocompatibility and sustained drug release property, and drug-loaded nanoparticles show better inhibition to cancer cells than DOX in vitro, which revealed the promising potential as carriers for antitumor agents. |
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