Layer-by-layer assembled film of TiO2/poly(l-lysine)/graphene quantum dots for simultaneous electrochemical determination of guanine and adenine

[Display omitted] •A sensitive electrochemical sensor for guanine and adenine is designed with TiO2/poly(l-lysine)/GQDs film.•This sensor can simultaneously respond guanine and adenine down to 0.4 and 0.17 µM, respectively.•This sensor shows good stability, reproducibility, and anti-interference ability.•This sensor has successfully been used to detect guanine and adenine in calf thymus DNA, milk, and urine samples. This work proposed an electrochemical biosensing method for simultaneous detection of guanine and adenine. This electrochemical biosensor was constructed by layer-by-layer assembling TiO2 nanoparticles, poly(l-lysine) and graphene quantum dots (GQDs) on a glassy carbon electrode. The assembled film of TiO2/poly(l-lysine)/GQDs showed better conductivity and significantly increased effective surface area for the electrochemical oxidation of guanine and adenine along with a quasi-reversible electrode process. Under optimal preparation and square wave voltammetric detection conditions, the proposed electrochemical methods could simultaneously detect guanine and adenine ranging from 1.0 to 35.0 µM with detection limits of 0.56 µM for GA and 0.81 µM for AD. The limits of quantification for sample analysis were 1.90 and 2.70 µM, respectively. The developed electrochemical biosensor exhibited good reproducibility, anti-interfering properties, and stability, and could be practically applied in the simultaneous determination of guanine and adenine in calf thymus DNA, cow milk, and urine samples with acceptable precision.