Turn on-off fluorescent sensor for protamine and heparin based on label-free silicon quantum dots coupled with gold nanoparticles

An ultrasensitive turn on-off fluorescent sensor was presented for determination of protamine and heparin based on the high quenching ability of gold nanoparticles (AuNPs) to the fluorescence of silicon quantum dots (SiQDs) as well as high binding affinity of protamine with heparin. The fluorescence of SiQDs was quenched significantly by adding AuNPs into SiQDs solution. Upon addition of protamine, the AuNPs aggregated and the fluorescence of SiQDs was recovered due to the competitive adsorption of protamine and SiQDs on AuNPs. Addition of heparin disturbed the interaction between protamine and AuNPs due to its strong affinity to protamine, resulting in an adsorption of SiQDs on the surface of AuNPs. Thus the fluorescence of SiQDs was quenched. The strategy was simply achieved by measuring the changes in the fluorescence of SiQDs. The research results suggested that the developed method has several advantages such as label-free, high sensitivity, low cost, ease of operation. The linear response range was obtained over the range 0-1.2 mu g/mL and 0.002-1.4 mu g/mL with the low detection limit of 6.7 ng/mL and 0.67 ng/mL for protamine and heparin, respectively. The sensing platform was successfully applied to determination of heparin and protamine in serum samples. (C) 2015 Elsevier B.V. All rights reserved.