Lab-on-a-chip Platform Based on Graphene Field-effect Transistors for DNA Sensing

Lab-on-a-chip systems for the detection of complex diseases are growing in importance, normally requiring the detection of multiple targets in an autonomous and portable fashion. Taking advantage of graphene low-dimensionality, high carrier mobility and chemical stability, we developed a monoplex assay based on DNA label-free sensors. The graphene genosensors are based on an electrolyte-gated field-effect transistor (FET) array, with a receded, integrated gate architecture. The 22 graphene channels of the devices in the array are functionalized with a linker for single stranded DNA immobilization, which acts as the capture probe. The 30 nucleotides-long immobilized DNA sequences are designed for specificity towards the DNA target. Electrical lines and contacts are passivated leaving exposed to the biomolecule-containing solutions only the graphene channel active area of the devices.

Fully complementary target DNA is detected in a linear range between 1 aM and 100 fM, with SNP sensitivity down to 10 aM. The FET genosensor array is designed for multiplex configuration, and portability. Therefore, it is fabricated on a single chip and integrated in a lab-on-chip platform containing a microcontroller, a 16 bit DAC for gate voltage application (0-3.3 V), a 8 bit digital potentiometer and a resistance-controlled current source (1-100 µA) for sensor bias, a 16 bit ADC for sensor readout, and several 12×8 CMOS matrices connecting instrumentation lines to sensor lines, thus providing simultaneous transistor readout capability. Additionally, a flow cell of 4.3 mL sample volume was built to allow for sequential injection of multiple testing samples in an automated way. Overall, the detection system comprises a syringe pump, a multiposition valve and the lab-on-a-chip platform for portable detection.

The results of this work pave the way for a wide range of applications, including personalized medicine, early diagnosis of cancer and infectious diseases, like malaria and others, as a point-of-care tool.