Research
Tunable Quantum Dot Bioconjugates for Targeting and Imaging of Cells
Photoluminescent semiconductor quantum dots (QDs) are of significant interest for bioimaging and fluorescence labeling. Currently, the best available QDs for bioimaging are based on CdSe. However, there are issues concerning inorganic passivation and application to a broad range of pH and cytotoxicity. Although, the potential cytotoxicity of heavy metals, Cd and Se, is being explored by employing different protections such as ZnS and polymers, the leakage of Cd-ions through the outer shell induced by photolysis and oxidation, and the enrichment of these ions in the physiological system in the long term is a serious concern. Furthermore, identifying an effective cap from the viewpoint of ligand-exchange efficiency remains a scientific challenge. These concerns have been addressed by successfully developing highly sensitive, biocompatible, and non-toxic nanoprobes for cellular imaging. The innovative structural design of QDs involves immobilization of multiple manganese-doped zinc oxide QDs (~2-4 nm) on hydrophilic silica nanosphere (~100 nm). This approach eliminates drawbacks of CdSe-based QDs, and provides significant benefits of ultrasensitivity, high brightness, reliable and reproducible imaging of biomolecules. Lastly, these QDs have long term stability of up to 12 months with "size and dopant compositional tunable fluorescence emission" from visible to near-infrared biological window (~650-770 nm).
The adsorption of proteins from blood plasma to the biomaterial surface is a dynamic process during which proteins bind to the surface and rearrange. Adsorbed proteins act as pilots for cell adhesion, if they have the correct geometry to mediate cell attachment. Moreover, the structure and constitution of adsorbed plasma proteins on the surface governs events that follow adsorption, including cell attachment, proliferation, and tissue formation. Thus, the adsorption and self-assembly (microstructure) of proteins at biointerfaces, metallic or nonmetallic, which govern biological response is important.
