Silver nanodendrites as substrate for a selective non-enzymatic insulin sensor using surface-enhanced Raman spectroscopy

Abstract

A sensitive and selective detection method of insulin has been developed by using silver nanodendrites (AgNDs) as a substrate in Surface-Enhanced Raman Spectroscopy (SERS) measurements. The AgNDs were electrochemically synthesized in the citric acid solution on the surface of screen-printed carbon electrode (SPCE). SEM images show the growth of dendrites morphology of the silver particles on the surface of SPCE, which increase the surface area of SPCE from 0.88 to 2.88 cm2. The use of the synthesized materials as a substrate for the detection of insulin with an excitation laser of 785 nm at 400 mW observes the highest peak intensity for insulin phenylalanine peaks at the wavenumber around 1003 cm-1. The intensity of this peak linearly increases with insulin concentrations with a sensitivity of 48.736 a.u./IU and a limit of detection of 0.018 IU or equivalent to 0.108 mu M, indicating that the detection of insulin at extremely low concentrations could be performed. Furthermore, this peak shows less interference by glucose, cholesterol, and NaCl at low concentrations, with recovery rates exceeding 95 %. The demonstrated analysis of a commercial insulin sample shows recovery rates close to 100 %, validating the method's effectiveness for practical applications. Reproducibility and repeatability assessments show excellent stability, with relative standard deviations (RSD) of 0.65 % and 1.85 %, respectively, over the successive measurements. These findings highlight the significant potential of AgNDs to be used as a substrate for SERS as a powerful and reliable tool for insulin detection, supporting its applications in advanced biomedical diagnostics.