March 6, 2002 – Munich, Germany – Infineon Technologies has released information on its development of what it claims to be the world’s first molecular test biochip with integrated evaluation electronics. The device potentially simplifies test procedures and offers efficiency and cost advantages in testing of nucleic acids and proteins in areas such as clinical diagnosis and individual patient medication.
Infineon says it has demonstrated that it can combine electronic circuitry for test analyses with biochemical test “wells” on a single silicon chip structure. This breakthrough achievement is a significant step in research to accelerate and optimize molecular-level analysis. Infineon expects that the laboratory tests of the electronic biochips will commence in approximately one year.
128 test tubes on a chip
The test biochips fabricated by Infineon measure approximately one quarter of a square centimeter. Each biochip contains 128 homogeneous “wells” that are 100 microns in diameter. Biological mini-probes can be linked to these wells, effectively allowing 128 miniaturized different tests on a chip. The electronic circuits fabricated on the same chip are used to replace optical analysis of samples with measurements of electric currents depending on the test samples’ properties. The result is a test apparatus that is smaller and less complex than optical systems.
The biochip has the potential to make medical diagnosis in hospitals and in medical practices less costly, faster, and more efficient. In the long-term, biochips open up new applications, such as determining whether or not a patient has adverse reactions to a medication.
On-chip analysis and evaluation
The Infineon biochip is fabricated on a standard Complementary Metal Oxide Semiconductor (CMOS) technology extended with additional process steps to form sensor electrodes made of gold. Silicon as basis material allows the integration of electronic circuitry for signal amplification and evaluation within the chip. Infineon’s success in integrating the gold electrodes on chip, without affecting the CMOS structures, is a process technology breakthrough. For the first time, standard CMOS production methods can be used to produce biochips with “built-in” analysis capability.
Testing and evaluation methods of biochips
With on-chip electronic analysis testing method, specific enzymes are added to the probes to be tested. These enzymes are able to split another substance, which has been added in a separate step, into electronically active components. This chemical procedure creates an electrical current of 1 pA to 100 nA at the sensor gold electrodes, which is measured with highly sensitive circuits. The timeline and intensity of the electrical current identifies the composition and concentration of the tested substance.
In today’s optical techniques, unknown gene sequences are loaded onto a biochip after first having been tagged with a fluorescent dye emitting light of a particular wavelength when irradiated. During the tests, a specific charge-coupled-camera (CCD) reads the light patterns emitted. These light patterns explain the composition of the substances tested.