Objective: To prepare conjugates of quantum dots and Staphylococcal protein A (SPA) and figure out the optimal conditions. Methods: The “classical injection method” was used to prepare cadmium telluride quantum dots, while 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) were applied as coupling agents for coupling quantum dots with SPA. A single factor inspection method was adopted to explore the effects of the different amount of EDC, NHS, SPA and the reaction time on the coupling efficiency. Results: A series of conjugates were prepared with different ratios of quantum dots, EDC, NHS, SPA and reaction time. Among them, the fluorescence intensity of the conjugate is the strongest while the ratio of quantum dots to EDC is 1 ∶1 500, the ratio of EDC to NHS is 1 ∶2, and the reaction time is 2 h. Conclusion: When the ratio of cadmium telluride quantum dots to EDC and NHS is 1 ∶1 500 ∶3 000, and the reaction time is 2 h, the cadmium telluride quantum dot-SPA conjugate with better fluorescence intensity could be prepared.

［Key words］quantum dots; Staphylococcal protein A; coupling