Influence of pH on aptamer-based gold nanoparticles colorimetric sensors

In recent years, aptamer-based gold nanoparticles (AuNPs) colorimetric sensors have received extensive attention, especially in discovery of disease markers and food safety. However, the detection sensitivity is not high enough and the detection results are prone to false positives. Therefore, it is urgently to improve the performance of sensors, ranging from the optimization of sensor detection conditions and establishment of new sensing methods. pH is an important parameter in the solution. In this article, pH was employed to adjust the aptamer charge to increase the sensitivity of lysozyme detection, and the detection limit can be approached as low as 0.05 nM. pH was also used to adjust the target charge to improve the performance of sensors. Chloramphenicol (CAP) and precursors of chloramphenicol (CAP-base) were used as targets to verify the charge effect introduced by pH adjustment. The experiment found that the neutral or electronegativity target would weaken the response of the sensor. To achieve the detection of CAP (electron neutral), a competitive colorimetric sensor had been successfully established to detect CAP. The Derjaguin–Landau–Verwey–Overbeck (DLVO) theory was used to explain the effect of pH on sensor performance. Therefore, by adjusting pH, the detection sensitivity can be improved significantly and a new sensing method can be established, which provide a broad application prospects for chemical, environmental and biological sensing.