Scientists have begun integrating electronics into biology, but don't bolt your doors in fear of cyborgs and hybrid human-robots yet! Researchers from the Instituto de Microelectrónica de Barcelona IMB-CNM (CSIC), have found a way to implant minute silicon chips into living cells and use them as intracellular sensors. This bio-nanotechnological advancement could tell us a lot about how our cells are working at a nano level, and have widespread implications for early detection of diseases, and new cellular repair mechanisms.

CMOS or Complementary Metal–Oxide–Semiconductor is a technology for constructing integrated circuits, also known as IC, microcircuit, microchip, silicon chip, or chips. These are miniaturized electronic circuits that have been manufactured in the surface of a thin substrate of semiconductor material, and are used in almost all electronic equipment today. A typical human cell is the size of about 10 square micrometers and with transistors the size of nanometers, hundreds of today's smallest transistors could fit inside a single cell. It was therefore only a matter of time before scientists began interfacing nanoelectronic components with living cells.

The team in the Micro and Nanosystems Department at IMB-CNM (CSIC) began by fabricating different batches of polysilicon chips, a typical semiconductor material, and choosing the most suitable types with lateral dimensions of 1.5–3µm and with a thickness of 0.5 µm before implanting them inside living cells taken from Dictyostelium discoideum and human HeLa cells. Preliminary experiments incubating the HeLa cells with polysilicon chips gave low yields of internalized intracellular chips (ICC) so they used lipofection (encapsulation of materials in a lipid vesicle called a liposome) to obtain higher rates of ICC-containing cells. After insertion, the researchers then monitored the cells to make sure they remained alive and healthy. They found that over 90% of the HeLa cell population remained viable seven days after lipofection.

Having demonstrated that silicon chips smaller than cells could be produced, collected, and internalized inside living cells by different techniques (lipofection, phagocytosis or microinjection), they went on to further demonstrate the versatility of the technique by studying the integration of different materials in a single chip and their 3D nanostructuring capability and using other common microelectronics techniques such as FIB milling.

Most significantly however, they wanted to prove that the silicon chips could be used as intracellular sensors. "Today's micro- and nanoelectronic processes already would allow us to produce complex 3-dimensional microscale structures as sensors and actuators," said Plaza. "Complex structures, smaller than cells, can be mass produced with nanometer precision in shape and dimensions and at low cost already. Furthermore, many different materials (semiconductors, metals, and insulators) could be patterned on the silicon chip with accurate dimensions and geometries."

The main applications of future intracellular chips will be the study of individual cells. The technology could significantly aid early detection of diseases and new cellular repair mechanisms.

The team published its findings "Intracellular Silicon Chips in Living Cells" in a recent issue of Small.