A Dual-Channel Sensor Array: Ultraviolet Absorption and Surface Potential Measurements for Discrimination of Amino Acids Based on Gold Nanorods

Abstract

We report a dual-channel array based on gold nanorods (GNRs) to catalyze the reaction of methyl orange (MO) and sodium borohydride (NaBH4) for recognition of multiple amino acids. The sensor array consists of two channels: ultraviolet absorption and surface potential measurements. When amino acids with negative charges exist, positively charged GNRs and negatively charged amino acids attract each other, triggering the catalytic reduction ability of the GNRs to weaken and resulting in a decrease in the amount of reduction products of MO. Therefore, compared with the solution without target amino acids with negative charges, the absorbance of the solution at 460 nm decreases and zeta potential of the solution increases. However, in the presence of positively charged amino acids, the result is opposite to that of negatively charged amino acids mentioned above. Due to different amino acids with different charges, their existence leads to specific array’s response patterns, i.e., ultraviolet absorption and surface potentials, which are distinguished by linear discriminant analysis. The sensor array successfully distinguished five amino acids (glutamic acid (Glu), lysine (Lys), aspartic acid (Asp), arginine (Arg), and histidine (His)) at the 100 nM level in complex media, showing great potential in the field of clinical diagnosis, biomedical research, and so on.