Surface modification of ZnSe/ZnS Quantum dots with biocompatible polymer for biological applications

Abstract

In this work, ZnSe/ZnS quantum dot nanoparticles (ZnSe/ZnS QDs) were synthesized and modified in order to apply in bio-application. ZnSe/ZnS QDs were synthesized using zinc stearate as zinc precursor and 1-octadecene as solvent by a hot-injection method in one-pot. The ZnSe/ZnS QDs were characterized using UV-visible spectroscopy, fluorescence spectroscopy and TEM. The photoluminescence of ZnSe/ZnS QDs was blue with the emission wavelength of about 400-450 nm and narrow full width at half maximum (FWHM) of about 20-30 nm. For TEM images, the results showed size and structure of ZnSe/ZnS QD nanoparticles. The average diameter of ZnSe/ZnS QDs particles was 3.8±0.4 nm. The size of ZnSe core QDs was increased upon coating with ZnS shell. In order to improve dispersibility in aqueous phase and reduce toxicity, ZnSe/ZnS QDs were modified with thiol-conjugated polyamidoamine (PAMAM) polymer by ligand exchange method. The results showed that ZnSe/ZnS QDs 4-(3,5-bis(mercaptomethyl)phenoxy)butanoic acid poly(amidoamine) (ZnSe/ZnS QDs-BMPBA-PAMAM) were obtained with higher efficiency than ZnSe/ZnS quantum dots dihydrolipoic acid poly(amidoamine) (ZnSe/ZnS QDs-DHLA-PAMAM). For cytotoxicity studied by methylthiazolyldiphenyltetrazolium bromide (MTT) assay, ZnSe/ZnS QDs were studied in comparison with the conventional CdSe/ZnS core-shell QDs. The Zn-based QDs exhibited lower toxicity than the Cd-based QDs, and the QDs that have been modified with thiol-conjugated PAMAM polymer showed higher biocompatibility than the ones without PAMAM and be more suitable for applying in biological applications.