The conjugation of antibody to semiconductor quantum dots plays a very important role in many applications such as bioimaging, biomarking, and biosensing. In this research, we present some results of highly luminescent core/shell structure CdSe/ZnS on which theE. coliantibody was conjugated. The CdSe core was synthesized successfully with chemical “green” method. For biological applications, the capping surfactant, trioctylphosphine oxide, was substituted by a new one, mercaptopropionic acid (MPA), before the antibody attachment step. Finally, theE. coliantibody was attached to quantum dots CdSe/ZnS. Morphology, structure, and optical properties were investigated with PL, UV-Vis, TEM, and XRD methods. The successful ligand substitution and antibody attachment were confirmed by zeta potential measurement, FTIR spectroscopy, and TEM. The results showed quantum dots size of 2.3 nm, uniform distribution, and high luminescence. CdSe/ZnS core/shell structure had better stability and enhanced the luminescence efficiency up to threefold compared with the core CdSe. MPA ligand shifted the initial hydrophobic quantum dots to hydrophilic ones, which helped to dissolve them in organic solvents and attach the antibody.
Quantum dots have been considered to be promising candidates for bioapplications because of their high sensitivity, rapid response, and reliability. The synthesis of high-quality quantum dots that can be dissolved in water and other biological media is a crucial step toward their further application in biology. Starting with a one-pot reaction and the successive ionic layer adsorption and reaction (SILAR) method, we produced the CdSe/ZnS core/shell structure. Through a ligand-exchange mechanism, we coated the asmade CdSe/ZnS structure with 3-mercaptopropionic acid (MPA) or mercaptosuccinic acid (MSA). Various techniques, including photoluminescence (PL), ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, were utilized to characterize the ligand-coated CdSe/ZnS structure. The results show enhanced luminescence intensity, CdSe surface passivation by ZnS, and successful coating with MPA and MSA. The stability of quantum dots in solutions with different pH values was investigated by performing zeta potential measurements. The results revealed that the quantum dots shifted from displaying hydrophobic to hydrophilic behavior and could be connected with bioagents.
Early and highly accurate detection of diverse diseases is in urgent demand than ever, especially for cancers and infectious ones. Among possibilities, biosensing by utilizing conjugated nanoparticles is still a method of choice. However, the toxicity of quantum dots remains a big matter of concern in those biooriented applications. In this study, mercaptosuccinic acid-coated cadmium selenide quantum dots of approximately 2.3 nm were synthesized with a simple green method at low temperature and cost-saving chemicals. The influence of synthesis factors was investigated with different spectroscopic methods. The toxicity issue was evaluated on the NIH-3T3 cell line (ATCC® CRL-1658™) and an MTT assay, revealing a secure threshold of 20 μg/ml. Consequently, successful conjugation to the CD3 antibody including an A/G protein bridge was implemented and verified with fluorescent methods. Finally, Jurkat T cell detectability of conjugated CdSe was successfully validated with fluorescent microscopy. The CdSe-based products are accessible for future biosensing applications.
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