Label-free, direct DNA detection by means of a standard CMOS electronic chip

An integrated chip for DNA hybridization detection was realized in a standard CMOS process: it hosts 80 biosensors subdivided in 2 channels, as well as D/A and A/D converters for electrical stimulation and readout. A microfluidic system, bonded on the surface of the chip, provides access to the sensing areas for test solutions and reagents. A simple, low-cost technique for the realization of a biocompatible interface on the aluminum sensing area was developed; it allows the immobilization of single-stranded DNA oligonucleotides on the sensing electrodes. The electrical response of the realized chip to the functionalization and hybridization processes was verified. A direct extrapolation of the density of the immobilized oligonucleotides was possible and this demonstrated the compatibility of the results with electrochemical data available in literature. Experimental results show sensitivity to target concentration down to 100 pM. Selectivity was tested by verifying that no response is generated by oligonucleotides either completely non-complementary or with 5 and 3 modifications.