Bovine serum albumin-capped CdS quantum dots as an inner-filter effect sensor for rapid detection and quantification of protamine and heparin

In this work, we developed a novel and sensitive sensor for the detection of heparin and protamine based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and bovine serum albumin-capped CdS quantum dots (QDs). The methodology enabled the use of a simple synthesis procedure for CdS QDs via a fast route using bovine serum albumin as a capping agent. The fluorescence of the QDs could be quenched by AuNPs based on the IFE. Protamine could effectively turn on the fluorescence due to the electrostatic attraction between protamine and the AuNPs. On the addition of both heparin and protamine, the IFE system was formed owing to the stronger interaction between heparin and protamine than that with the AuNPs, leading to a marked fluorescence quenching of the QDs. By measuring the fluorescence of the QDs, the concentration of protamine and heparin was evaluated. Under the optimized conditions, the proposed nanosensor could be used for protamine detection in the concentration range of 10-350 ng mL(-1) with a detection limit of 2.4 ng mL(-1). The linear range for heparin anions was 10-300 ng mL(-1) with a detection limit of 2.2 ng mL(-1). Furthermore, a simple and convenient method had been used for protamine and heparin detection in serum samples with satisfactory results.