Colourimetric-based method for the diagnosis of spinal muscular atrophy using gold nanoprobes

Although numerous molecular methods for spinal muscular atrophy (SMA) detection have been exploited, most of them are laborious, time consuming and costly. Recently, gold nanoparticles (AuNPs) have attracted attention in the field of colourimetric bioanalysis, because AuNP aggregation can be tracked with the naked eye as well as ultraviolet-visible (UV-vis) peak analysis. Here, based on a non-cross linking platform, a colourimetric-based method was used to evaluate the capability of thiolated oligo-AuNPs (Au nanoprobes) to distinguish between normal individuals, carriers and those with SMA. In this platform, removal of the repulsive force of the Au nanoprobes using high salt concentration solutions forced them to aggregate. Amplified DNA products from 20 blood samples were hybridised with the Au nanoprobes. UV-vis spectra and peak analysis ratios of SMA-positive samples revealed that, following salt addition, the unhybridised Au nanoprobes progressively aggregated and their absorption peak shifted to longer wavelengths (P<0.05), observed as a colour change from red to violet-purple. In contrast, colourimetric discrimination between normal and carrier samples following salt addition was not possible because of the small differences in their spectra and aggregation indices. Using this method, patients can be screened in <30 min.