Release and Detection of microRNA by Combining Magnetic Hyperthermia and Electrochemistry Modules on a Microfluidic Chip.

The heating of a biologic solution is a crucial part in an amplification process such as the catalytic detection of a biological target. However, in many situations, heating must be limited in microfluidic devices, as high temperatures can cause the denaturation of the chip components. Local heating through magnetic hyperthermia on magnetic nano-objects has opened the doors to numerous improvements, such as for oncology where a reduced heating allows the synergy of chemotherapy and thermotherapy. Here we report on the design and implementation of a lab on chip without global heating of samples. It takes advantage of the extreme efficiency of DNA-modified superparamagnetic core–shell nanoparticles to capture complementary sequences (microRNA-target), uses magnetic hyperthermia to locally release these targets, and detects them through electrochemical techniques using ultra-sensitive channel DNA-modified ultramicroelectrodes. The combination of magnetic hyperthermia and microfluidics coupled with on-chip electrochemistry opens the way to a drastic reduction in the time devoted to the steps of extraction, amplification and nucleic acids detection. The originality comes from the design and microfabrication of the microfluidic chip suitable to its insertion in the millimetric gap of toric inductance with a ferrite core.