Colorimetric detection of DNA hybridization based on a dual platform of gold nanoparticles and graphene oxide

•Development of a basic colorimetric system utilizing oligonucleotide conjugated gold nanoparticles and graphene oxide through DNA hybridization.•Formation of nanoparticle composite between gold nanoparticles and graphene oxide sheets through DNA hybridization.•Detection of DNA hybridization through colour change of the biosensor system from pinkish red to purplish solution and wavelength shift through spectrophotometer analysis.•Highly specific biosensor system to targeted DNA sequence with non-specific sequence not inducing any colour change or wavelength shift.•Biosensor system exhibited lowest sensitivity of detection at 8 nM of target DNA sequence.

The unique property of gold nanoparticles (Au NP) to induce colour change and the versatility of graphene oxides (GO) in surface modification makes them ideal in the application of colorimetric biosensor. Thus we developed a label free optical method to detect DNA hybridization through a visually observed colour change. The Au NP is conjugated to a DNA probe and is allowed to hybridize with the DNA target to the GO thus causing a change in colour from pinkish-red to purplish blue. Spectrophometry analysis gave a wavelength shift of 22 nm with 1 µM of DNA target. Sensitivity testing using serially diluted DNA conjugated GO showed that the optimum detection was at 63 nM of DNA target with the limit at 8 nM. This proves the possibility for the detection of DNA hybridization through the use of dual nanoparticle system by visual observation.