Editing Biosensor (section)

===Cells===
Cells are often used in bioreceptors because they are sensitive to surrounding environment and they can respond to all kinds of stimulants. Cells tend to attach to the surface so they can be easily immobilized. Compared to organelles they remain active for longer period and the reproducibility makes them reusable. They are commonly used to detect global parameter like stress condition, toxicity and organic derivatives. They can also be used to monitor the treatment effect of drugs. One application is to use cells to determine herbicides which are main aquatic contaminant.<ref>{{cite journal | last1 = Védrine | first1 = C. | last2 = Leclerc | first2 = J.-C. | last3 = Durrieu | first3 = C. | last4 = Tran-Minh | first4 = C. | year = 2003 | title = Optical whole-cell biosensor using Chlorella vulgaris designed for monitoring herbicides | journal = Biosensors & Bioelectronics | volume = 18 | issue = 4| pages = 457–63 | doi=10.1016/s0956-5663(02)00157-4| pmid = 12604263 | citeseerx = 10.1.1.1031.5904 }}</ref> Microalgae are entrapped on a quartz [[microfiber]] and the chlorophyll fluorescence modified by herbicides is collected at the tip of an optical fiber bundle and transmitted to a fluorimeter. The algae are continuously cultured to get optimized measurement. Results show that detection limit of certain herbicide can reach sub-ppb concentration level. Some cells can also be used to monitor the microbial corrosion.<ref>{{cite journal | last1 = Dubey | first1 = R. S. | last2 = Upadhyay | first2 = S. N. | year = 2001 | title = Microbial corrosion monitoring by an amperometric microbial biosensor developed using whole cell of Pseudomonas sp. | journal = Biosensors & Bioelectronics | volume = 16 | issue = 9–12| pages = 995–1000 | doi=10.1016/s0956-5663(01)00203-2| pmid = 11679280 }}</ref> Pseudomonas sp. is isolated from corroded material surface and immobilized on acetylcellulose membrane. The respiration activity is determined by measuring oxygen consumption. There is linear relationship between the current generated and the concentration of [[sulfuric acid]]. The response time is related to the loading of cells and surrounding environments and can be controlled to no more than 5min.