Label-free immunosensor for morphine based on the electrochemiluminescence of luminol on indium–tin oxide coated glass functionalized with gold nanoparticles

Abstract

We report here the development of an immunosensor for morphine based on electrochemiluminescence using luminol as the probe. Gold nanoparticles were attached to the surface of indium–tin oxide coated glass via hydrolyzed 3-amino-propyltrimethoxysilane. This coating acted as a matrix to directly immobilize an antibody to morphine as the sensing host via adsorption. The electrochemiluminescence intensity of luminol on this sensor decreased with the concentration of morphine after immuno-incubation. There was a linear relationship with the logarithm of the morphine concentration in the range 2–200 ng mL⁻¹ and a detection limit of 0.82 ng mL⁻¹ (S/N = 3). The sensor was used to determine the concentration of morphine in spiked urine samples with a satisfactory recovery. This label-free sensor has the potential to be developed as a disposable, portable and mass-produced device as a result of its simplicity of preparation and utilization.