Preparation And Application Of Fluorescein-Labeled Starch-Based Nanospheres

Starch is a natural polymer material which has a very good biocompatibility and biodegradable, adequate source and low prices. The nanospheres preparated from starch can make the drugs through the epithelial tissue smoothly, promote the penetration and absorption of drugs, extend the circulation time of drugs in the body, reduce the adverse effects of drugs and improve the drug utilization effectively. This paper aims to use cheap starch as raw material, not only prepared starch nanospheres using precipitation method which is simple and environmental friendly, and prepared a novel biodegradable fluorescent nanospheres through bonding fluorescein isothiocyanate (FITC) chemically in the starch chain which given starch nanospheres fluorescence properties.Fluorescein-labeled starch ester was obtained by replaced the hydroxyl groups of starch by acetic anhydride and FITC using organic synthesis methods, which given starch ester fluorescence properties. The structure of fluorescent starch ester was determined by 1H NMR; the degree of substitution of acetic anhydride of 2.14 was calculated by 1H NMR method, and the degree of substitution of FITC was 0.2% calculated by the fluorescence standard curve of FITC; the fluorescent particles showed spherical, the particle size range of these nanospheres is from 100nm to 700nm, and the average particle size distribution is 0.01; the influence of different FITC substitution, different initial concentration of fluorescent starch ester and different proportion of water and organic phases on particle size and size distribution were examined systematically; the maximum fluorescence emission peak of fluorescence nanospheres in fluorescence emission spectra was at 516nm, which indicated that incorporation of the indicator dyes in starch matrix has no major effect on the fluorescence properties of the fluorophores; the fluorescence properties of fluorescent nanospheres was same as FITC, the fluorescence intensity increases with increasing pH of the solution, the fluorescence intensity increases 11-fold when increases the pH from 5.7 to 8.0; the fluorescence quenching of fluorescent nanospheres by fluorescence quencher KI can be represented as the Stern-Volmer plot, the quenching constant of fluorescence nanospheres is much less than free FITC; the fluorescent nanospheres can be degradation in pH 7.4 phosphate buffer solution, and the fluorescence intensity increased with the degradation of the nanospheres.The ibuprofen-loaded starch-based fluorescent nanospheres were preperated by nanoprecipitation procedure; the nanospheres present a regular shape and uniform size. The ibuprofen-loaded starch-based fluorescent nanospheres have a higher drug encapsulation efficiency and drug loading, the highest drug encapsulation efficiency was 69.5% and the highest drug loading was 20.86%. The amount of fluorescein-labeled starch ester, the addition of ibuprofen and the volume ratio of acetone and water influence the drug encapsulation efficiency, drug loading and drug release rate of the fluorescent nanospheres. The released process in vitro of the drug-loaded nanospheres was characterized by scanning electron microscope and confocal laser scanning microscope.The starch-based fluorescent nanospheres were successfully prepared can transform the starch from waste to treasure, enhanced the value of starch effectively.