RGB colorimetric method based detection of oxytocin in food samples using cysteamine functionalized gold nanoparticles

In the present investigation, a colorimetric method has been demonstrated for detection of oxytocin using Cysteamine functionalized gold nanoparticles (Cys-AuNP). The analyte oxytocin which finds its use in medical field is purposefully injected in fruits and vegetables for their faster growth. Also, it is used in the milk letdown in cattles. The complexity of segregating oxytocin induced fruit and vegetables from naturally grown ones led to development of the method. The choice of spherical gold nanoparticles for development of sensor was influenced from its unique optical properties. Moreover, functionalization with cysteamine increased its sensitivity towards oxytocin detection. The method was coupled with RGB colorimetric technique which exhibited excellent linear correlation between Oxytocin concentration and RGB color values (R2 = 0.96). The RGB method used measured the intensity of color and a relation was established between measured RGB values and concentration of analyte (Oxytocin) present in the sample. This formed the basis for generation of simple colorimetric card that can be used to relate the color with amount present in the sample. More significantly, the Cys-AuNP shows excellent selectivity towards other coexisting substances present in the sample. This method with good precision (RSD>15%) offers suitability for onsite application without need for complex instrumentation.