KEYWORDS: Zinc oxide, Quantum dots, Near infrared, Nanoparticles, Nanoprobes, Luminescence, Inflammation, In vitro testing, Bacteria, In vivo imaging, Transmission electron microscopy, Absorbance
Early diagnosis and effective treatment of bacterial infection has become increasingly important. Herein, we developed a fluorescent nano-probe MPA@ZnO-PEP by conjugating SiO2-stabilized ZnO quantum dot (ZnO@SiO2) with bacteria-targeting peptide PEP, which was encapsulated with MPA, a near infrared (NIR) dye. The nanoprobe MPA@ZnO-PEP showed excellent fluorescence property and could specifically distinguish bacterial infection from sterile inflammation both in vitro and in vivo. The favorable biocompatability of MPA@ZnO-PEP was verified by MTT assay. This probe was further modified with antibiotic methicillin to form the theranostic nanoparticle MPA/Met@ZnO-PEP with amplified antibacterial activity. These results promised the great potential of MPA@ZnO-PEP for efficient non-invasive early diagnosis of bacterial infections and effective bacterial-targeting therapy.
Exploiting the bright and colorful photophysical properties of semiconductor quantum dots (QDs) is an onward trend in biotechnology and QDs have been widely used as fluorescent probes in cell-targeted imaging. However, nonspecific binding to cellular membranes has been a major challenge. In this study, high quality cadmium telluride (CdTe) quantum dots with different particle sizes were prepared via hydrothermal method. The surface of the QDs was modified with the chemically reduced bovine serum albumin (BSA) for effective reduction of nonspecific binding in cell targeting. Here,the as–prepared QDs exhibits tunable photoluminescence (PL) emission between 525nm and 620 nm.BSA-coated QDs which also provide reaction sites for conjugation of targeting ligands is mainly achieved by multiple mercapto groups in BSA macromolecules as multidentate ligands and partially by ligand exchange interaction between BSA and QDs. The BSA-coated QDs, with an overwhelming majority of hydrodynamic diameter size of 15nm ,are found to exhibit strong fluorescent intensities. The cellular uptake and localization of QDs was studied using laser confocal scanning microscopy. The results indicated that the nonspecific cellular binding is effectively reduced by BSA-coated QDs, compared with the N-acetyl-L-cysteine (NAC) -coated CdTe QDs.
Quantum dots (QDs) is a promising candidate for biomedical imaging. However, the bio-toxicity of traditional quantum dots obstructed their further application seriously. In this work, a simple solution growth method was utilized to synthesize ZnO QDs. However, their self-assemble feature makes them unstable in aqueous solution. Furthermore, (3-Aminopropyl) triethoxysilane was selected as a capping agent to stabilize ZnO QDs and then ZnO@SiO2 nanoparticles were obtained. They dispersed excellently in water and exhibited favorable fluorescence properties owing to the protection of silane. The biocompatability of ZnO@SiO2 nanoparticles was verified by MTT assy. The cell affinity studies demonstrated that ZnO@SiO2 nanoparticles could be uptaken by cells efficiently. Therefore, the as-prepared ZnO@SiO2 nanoparticles is a promising candidate for applications in cell imaging.
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