Ultrasensitive direct detection of dsDNA using a glassy carbon electrode modified with thionin-functionalized multiple graphene aerogel and gold nanostars

The paper reports on the synthesis of a composite consisting of thionin-functionalized multiple graphene aerogel and gold nanostars (termed TF-MGA/GNSs). The composite displays an enhanced electrochemical performance compared to the classical graphene aerogel. The performance can be further improved by increasing number of the graphene oxide gelation cycles. The composite was deposited on a glassy carbon electrode to obtain a biosensor for the direct detection of dsDNA. The interaction of thionin with dsDNA causes a specific electrochemical response, best at a working voltage of -228 mV (vs. Ag/AgCl). The enhanced electrocatalytic activity of the composite strongly improves sensitivity. The differential pulse voltammetric signal linearly decreases with increasing dsDNA concentration in the range from 100 fg center dot mL(-1) to 10 ng center dot mL(-1), and the detection limit is 39 fg center dot mL(-1) (at an S/N ratio of 3). The method is sensitive, selective and rapid. It was successfully applied to the detection of circulating free DNA in human serum. The study also provides an attractive approach towards graphene aerogel-based materials to meet the needs of nanoelectronics for molecule diagnosis, bioanalysis and catalysis.