Heavy metals: lead, chromium, zinc, mercury, cadmium and copper. Conventional analytical techniques for heavy metals are precise but suffer from various disadvantages such as high costs, need for trained personnel and need to be performed in laboratory. For these reasons, biosensors are being developed and used for monitoring heavy metal concentration in environmental samples. Also, their biological basis makes them ideal for toxicological measurements of heavy metals, while conventional techniques can only measure their concentration. Enzymatic methods are commonly used for metal ion detection. Inhibition of the activity of an enzyme (alkaline phosphatase, glucose oxidase) reveals the presence of heavy metals. Bacterial biosensors have been developed for the analysis of heavy metals in environmental samples. Bacterial strains resistant to these ions can be engineered with gene encoding bioluminescent proteins and in this case production of light reveals the presence of a heavy metal ion in the sample.

Biochemical Oxygen Demand (BOD): BOD is a parameter widely used to indicate the amount of biodegradable organic matter in water. Its determination is time consuming and consequently not suitable for online process monitoring. Fast determination of BOD could be achieved with biosensors based methods. Most BOD biosensors rely on the measurement of the bacterial respiration rate in close proximity to a transducer, commonly of Clark Type. BOD Biosensors are the most common commercial biosensors for environmental monitoring. The first commercial BOD sensor was produced by the Japanese company Nisshin Electric in the far 1983. Number of other commercial BOD Biosensors based on microbial cells are being marketed by Autoteam GmbH, Medingen GmbH and Dr.Lange GmbH in Germany, Kelma in Belgium, BioScience Inc and US Filter in USA.

Nitrogen compounds: Nitrites are widely used for food preservation and for fertilization of soils. Continuous consumption can cause serious implications on human health. Increasing levels of nitrates found in groundwater and surface water are of concern because they can harm the aquatic environment. Many examples exists of biosensors based on amperometric or conductimetric transducers coupled with enzymes (cytochrome C nitrite reductase and other electrochemical mediators)

PolyChloroBiphenyls (PCBs): PCBs are toxic organic compounds that are ubiquitous environmental pollutants. Level of PCB depends on the matrix where it originated. Currently food is assumed to be the major source of the PCB exposure. Several hundreds of PCB configurations (planar, mono-ortho planar, non-coplanar) persist worldwide in the environment and food chain. Conventional techniques used for the analysis of PCBs are generally based on gas chromatography coupled with mass spectrometry (GC-MS). Alternative techniques based, for example, on immunoassays (ELISA), are inexpensive and rapid screening tools for sample monitoring in laboratory and in field analysis. They are simple, sensitive, reliable and relatively selective for PCB testing, too. Another interesting approach is the use of immunosensor technology.

Phenolic compounds: Considerable number of organic pollutants has phenolic structures. Phenolics are common compounds in the industrial effluents coming from the activities related to production of plastics, dyes, drugs, polymers, pesticides, detergents etc.. Several substituted phenols, such as chloro- and nitro- phenols are highly toxic to humans and aquatic organisms. They are defined as hazardous pollutants in EC and USA EPA. They usually interact with DNA leading to the damage to human health but these interactions can be used in electrochemical DNA biosensors generating a response signal thus providing an effective approach for rapid screening of these pollutants. Enzymes commonly used in the manufacture of biosensors for phenolic compounds are: laccase, tyrosinase, peroxidases

Endocrine disruptors and hormones are chemicals that interfere with endocrine system of animal and human body. They are systematically discharged in the environment during the last years and have been related to the decrease of human sperm numbers and increased incidence of testicular, breast and thyroid cancers. Endocrine disruptors follow several mechanisms as well as a) Inhibition of enzymes related to hormone synthesis, b) alteration of free concentration of hormones by interaction with plasmatic globulins, c) alteration in expression of hormone metabolism enzymes, d) interactions with hormone receptors acting as agonist or antagonists, e) alteration of signal transduction resulting from hormone action. Although very low concentrations (ng/l range) of hormones such as estradiol, estrone and ethynil estradiol have been found in water, they may have, even at these low concentrations, endocrine disrupting activity in aquatic end terrestrial organisms. Immunoassays and Immunosensors are the most commons systems developed for these pollutants.

Organophosphorous and carbamic compounds: They are a class of chemicals that are widely used as insecticides in modern agriculture for controlling a wide variety of insect pests, weeds and disease-transmitting vectors. They are the most abundant pollutants in the world and are present in water, atmosphere, soil, plants and food. Enzymatic biosensors based on the inhibition of a selected enzyme activity (acetyl cholinesterase, alkaline phosphatase) are the most extensively used biosensors for the screening of these compounds.

Herbicides: For the detection of herbicides such as the phenylureas and triazines, amperometric and optical biosensors have been designed with membrane receptors of thylakoid and chloroplasts, photosystems and reaction centers or complete cells such as unicellular alga.

Particulate Matter (PM): Numerous studies have demonstrated that elevated concentrations of suspended atmospheric PM are associated with adverse health effects. Ultra-fine and nano-particulate materials resulting from mixtures of coal and non-coal fuels combustion release components to the air with toxic potential. In order to minimize the adverse public health effects of atmospheric PM, there is a need for a greater understanding of the toxic mechanisms and the components that are responsible for the toxic effects. Bioassay techniques can be used to screen and investigate the aspects of oxidative stress, respiration inhibition and metal deficiency.

Disclaimer: These pages solely reflect my own personal opinion and may in no case be taken as an official statement from CNR