Development of fluorescent particles for bio-related application

Abstract

Part 1 Water-soluble and biocompatible quantum dots (QDs) were prepared by grafting folic acid-functionalized poly(methacrylic acid)-ran-(2-methacryloyloxyethyl phosphorylcholine) on QDs via ligand exchange method by using ethanolamine as a novel phase transfer agent to obtain QDs-PMAMPC-FA. The success of FA immobilization and the presence of PMAMPC-FA around the QDs were confirmed by FTIR. As revealed by transmission electron microscopy, the QDs-PMAMPC-FA were highly stable, spherical and had monodispersed size of 5.2±0.8 nm, slightly larger than the as-synthesized QDs (3.8±0.6 nm). This result was consistent with a small red-shift of fluorescence emission from 597 nm (as-sythesized QDs) to 606 nm (QDs- PMAMPC-FA). The core-shell structure of QDs-PMAMPC-FA was also observed from AFM analysis. Moreover, quantum yields of QDs stabilized by PMAMPC and PMAMPC-FA were higher than QDs stabilized by mercaptopropanoic acid (QDs-MPA), as water-soluble model QDs, demonstrating the improvement of photoluminescence of QDs by polymer modification. It is anticipated that these modified QDs can be developed for cellular imaging with specific targeted epidermoid cervical carcinoma (CaSki) cell having overexpressed folate receptor. Part 2 This research focused in synthesis of amphiphilic chitosan particle that can be detected with fluorescent microscope. The particles were to be used as carrier of drug or bioactive compounds. Two types of amphiphilic chitosan particle were prepared. The first type (Pyr-CSHTAP) had pyrene as hydrophobic entity and N-[(2-hydroxyl-3-trimethyl ammonium)]propyl (HTAP) from reaction with glycidyltrimethylammonium chloride (GTMAC) as hydrophilic entity. The second type (Pyr-CS-mPEG) had pyrene as hydrophobic entity and mPEG from reaction with mPEG-COOH as hydrophilic entity. Both types of particle were characterized by NMR and FT-IR and their morphology were observed with TEM and SEM. It was found that Pyr-CS-HTAP formed round particles with size of 0.77± 0.186 nm through aggregation of smaller particles. Pyr-CS-HTAP particle was then used to encapsulate curcumin, which could act as fluorescent dye. Investigation through CLSM showed that curcumin was successfully encapsulated via hydrophobic interaction and π-π interaction between aromatic rings of pyrene and curcumin.