A quantum dot-based optical immunosensor for human serum albumin detection

► Used QD to enhance the detection signals of biosensing. ► Used APTES to enhance the biological activity between glass and protein. ► Demonstrated successful HSA detection with a detection limit of 3.2×10−5mg/ml. ► Designed a small optical biosensor for integrating to microfluidic for future application. In this study, a CdSe/ZnS quantum dot (QD)-based immunosensor using a simple optical system for human serum albumin (HSA) detection is developed. Monoclonal anti-HSA (AHSA) immobilized on 3-aminopropyltriethoxysilane (APTES)-modified glass was used to capture HSA specifically. Bovine serum albumin (BSA) was used to block non-specific sites. The solution, containing AHSA–QD complex prepared by mixing biotinylated polyclonal anti-HSA and streptavidin coated QD, was used to conjugate with the HSA molecules captured on AHSA/BSA/APTES-modified glass for the modification of HSA with QD. A simple optical system, comprising a diode laser (405nm), an optical lens, a 515-nm-long pass filter, and an Si-photodiode, was used to detect fluorescence and convert it to photocurrent. The current intensity was determined by the amount of QD specifically conjugated with HSA, and was therefore HSA-concentration-dependent and could be used to quantify HSA concentration. The detection limit of the pure QD solution was ∼3.5×10−12M, and the detection limit for the CdSe/ZnS QD-based immunosensor developed in this study was approximately 3.2×10−5mg/ml. This small optical biosensing system shows considerable potential for future applications of on-chip liver-function detection.