Completed notes of the course

Pagina 1

BIOCHIP Lunedì 22 febbraio 2021 http://politecnicomilano.webex.com/politecnicomilano/ldr.php?RCID=81a6bf48848d4ef1a0e921f07c1c3 b08 BIOSENSORS  Measures the status of a biological system  a SENSOR based on a biological entity (cell or a part of a cell) and we put it into an artificial system  we can use macromolecules e.g. a bird uses as a gas sensor for miners The presence of a molecule in a fluid is a marker for some diseases. We want to identify molecule x. The idea is to take a macromolecule complementary to the molecule we are looking for. One molecule is the key, the other is the lock. The bonding of the target molecule to the receptor  we want to convert this event into an electrical signal. We don’t have the sensitivity to detect a single molecule, for instance due to the noise. The bonding is not static and this sets a detection threshold. We have a substrate and a linking layer which we want to attach the receptor on. The linking helps to attach the receptor. Ionic solution. In a dry environment the sensor will not work. AFFINITY: matching between the receptor and the target:  ANTIBODY-antigen (immunosensors)  ENZYME-substrate (enzymatic sensor): substrate is a molecule that binds the enz yme and profits the catalitical activity of the enzyme  ssDNA and nucleic acids (genosensors): we use the complementary sequence of the target we want to identify. DNA can be of natural origin or synthetic. SIZE SCALING and COMPATIBLITY Human cells (10-100um), bacteria (2um), virus (100nm), proteins (10nm), molecules (1nm). Microfabrication (microelectronics): we have the technological capability to fabricate something that matches the dimensions capability of the biological systems. For an object with a non -defined shape , we have the CONTOUR LENGTH and the RADIUS…