Development of DNA electrochemical biosensor based on covalent immobilization of probe DNA by direct coupling of sol–gel and self-assembly technologies

A new procedure for fabricating deoxyribonucleic acid (DNA) electrochemical biosensor was developed based on covalent immobilization of target single-stranded DNA (ssDNA) on Au electrode that had been functionalized by direct coupling of sol–gel and self-assembled technologies. Two siloxanes, 3-mercaptopropyltrimethoxysiloxane (MPTMS) and 3-glycidoxypropyltrimethoxysiloxane (GPTMS) were used as precursors to prepare functionally self-assembly sol–gel film on Au electrode. The thiol group of MPTMS allowed assembly of MPTMS sol–gel on gold electrode surface. Through co-condensation between silanols, GPTMS sol–gel with epoxide groups interconnected into MPTMS sol–gel and enabled covalent immobilization of target NH2–ssDNA through epoxide/amine coupling reaction. The concentration of MPTMS and GPTMS influenced the performance of the resulting biosensor due to competitive sol–gel process. The linear range of the developed biosensor for determination of complementary ssDNA was from 2.51 × 10−9 to 5.02 × 10−7 M with a detection limit of 8.57 × 10−10 M. The fabricated biosensor possessed good selectivity and could be regenerated. The covalent immobilization of target ssDNA on self-assembled sol–gel matrix could serve as a versatile platform for DNA immobilization and fabrication of biosensors.