Preparation of a portable calorimetry kit and one-step spectrophotometric nanomolar level detection of l-Histidine in serum and urine samples using sebacic acid capped silver nanoparticles

This work describes the synthesis of sebacic acid capped silver nanoparticles (SA-AgNPs) by the wet chemical method for the detection of l-Histidine in blood serum and urine samples. The synthesized SA-AgNPs were characterized by several techniques. The obtained particles were spherical in shape and the average diameter was calculated by HR-TEM images to be 11 nm. Moreover, the synthesized SA-AgNPs were stable for more than 3 months in solution. The synthesized SA-AgNPs showed the surface plasmon resonance (SPR) band at 420 nm. Interestingly, after the addition of 18.1 μM of l-Histidine into the SA-AgNPs solution, the SPR band absorbance decreased and the colour of the solution changed from brown to colourless. Based on the changes in the SPR band, we calculated the lowest detection limit to be 122 nM. The observed colour shift and spectral changes were due to the aggregation of SA-AgNPs induced by l-Histidine via hydrogen bonding interaction. Additionally, a possible mechanism is discussed. Furthermore, a 268-fold excess of common interferences did not interfere with the detection of 18.1 μM of l-Histidine. We successfully applied the SA-AgNPs probe for the detection of l-Histidine in blood serum and urine samples. Further, we validated our system with the HPLC technique. Importantly, we prepared a portable smartphone aided paper-based kit for on-site monitoring of l-Histidine. We strongly hope that this facile synthesis of SA-AgNPs and the portable paper-based kit will represent a step forward in the field of biosensing and materials science.