Influence of experimental conditions on the adsorption of disease biomarker proteins to InP/ZnS quantum dots.

The spontaneous formation of quantum dot (QD)-protein assemblies in the physiological environment exhibits challenges or benefits for nanomedicine applications. In this study, we investigated the QD-protein assemblies spontaneously formed with the greener water soluble InP/ZnS-COOH QDs and isolated disease biomarker proteins under various environmental conditions, including QDs size, solution pH, incubation time, ionic strength, different salts, as well as the lowest concentrations of the proteins that started the formation of detectable assemblies. It was shown that higher ionic strength or valence charge disrupted the assembly's formation. The basic pH 8.5 facilitated the formation to a greater extent than the pH 7.4 did. The heat shock protein 90-alpha (HSP90α) adsorbed on QDs surface more readily than cytochrome C (CytoC) and lysozyme (Lyz) in the basic environment. Among the three-sized QDs compared, the medium-sized QDs were the most effective in promoting the assemblies' formation. The detectable assemblies started at as low as 0.4 ng/mL of CytoC, 1.0 ng/mL of HSP90α, or 1.8 ng/mL of Lyz, respectively. The findings add insights into how the biomarker proteins interacted with the QDs under different environmental conditions, which promotes the understanding of QD-protein assemblies' collaborative behaviors when they facilitate bioimaging and biomedicine applications.