OPTIMISATION OF COLOURIMETRIC APTASENSOR FOR DETERMINATION OF METHYLPHOSPHONIC ACID USING RESPONSE SURFACE METHODOLOGY

Abstract

Methylphosphonic acid (MPA) is a chemical marker of organophosphorus chemical warfare agents (CWAs) and thus, the detection of MPA is important to examine the exposure of CWAs to humans and the environment. In this study, citrate capped gold nanoparticles (cit-AuNPs) and DNA aptamer were used to detect MPA based on colourimetry. In addition, image processing was utilised to convert colour images of the mixture into red, green and blue (RGB) values in order to improve the accuracy
of detection. The independent variables (concentration of cit-AuNPs, concentration of DNA aptamer and incubation period) influencing the detection were optimised using faced-centred central composite design (FCCD) with the response surface methodology (RSM). Analysis of variance (ANOVA) showed that the concentration of cit-AuNPs and incubation period significantly affected the detection. From the analysis, a good correlation between the experimental and predicted responses
was found as indicted by high R2 value (95.48%). The optimum conditions of the detection were suggested as the following conditions: concentration of cit-AuNPs of 155 nM, concentration of DNA aptamer of 1 μM and incubation period of 24.85 min.
Keywords: Aptamer; colourimetry; image processing; methylphosphonic acid; response surface , methodology (RSM).

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