Diagnostic Arrays

A variety of polymer films that have distinctly different electrical resistance responses to various vapors can be prepared to obtain diagnostic array signal patterns in response to a series of odorants. However, their use in RAC is very limited. 

Obviously, by means of sensor arrays several components can be determined simultaneously. This way of doing analytical chemistry is useful if the analytical probe is small, but on the other hand only a few components have to be studied in a restricted concentration range. In medical diagnostics, arrays of potentiometric sensors have been around for a long time. Such arrays, which have not been really subject to miniaturization, are used to determine the medically important ions Ca, K" ", Na" " and Mg " " simultaneously with low time demand. The quick availability of results is important particularly during an operation if physiologic speciflcations are kept constant within a certain range. 

The attachment of proteins onto solid surfaces in a highly organized manner is critical to the development of efficient and operationally flexible sensor and diagnostic arrays and... 

The development of DNA sensors and high-density DNA arrays has been prompted by the tremendous demands for innovative analytical tools capable of delivering the genetic information in a faster, simpler, and cheaper manner at the sample source, compared to traditional nucleic acid assays. Nanoparticle-biopolymer conjugates offer great potential for DNA diagnostics and can have a profound impact upon bioanalytical chemistry. Nanoparticle/polynucleotide assemblies for advanced electrical detection of DNA sequences have been reviewed by Wang [145]. 

The development of protein chip assays to determine protein function using purified components is a rapidly advancing area. Automated systems for the assay of protein function on chips in parallel for thousands of proteins simultaneously will likely be available in the next few years. These miniaturized arrays will be useful for basic research as well as for diagnostics and drug development. For instance, the combination of protein chips with combinatorial chemistry will allow the simultaneous screening of vast collections of small molecules against vast collections of potential target proteins. 

Antibodies have been used extensively as diagnostic tools in many different formats, especially for measurement of protein and cytokine abundances. Applications of antigen arrays can be found in reverse immunoassays for detection of allergens and autoimmune antibodies. 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

K.J. Albert, C.L. Schauer, and D.R. Walt, Optical sensor arrays for medical diagnostics, in Biomedical Diagnostic Science and Technology (W. Law, N. Akmal, and A Usmani, eds), pp. 121-138. Marcel Dekker, NY (2002). 

Since rolling circle amplification takes place at a constant temperature, there is no need for the target amplification process to take place in a thermal cycler, which is required to regulate the temperature for different parts of the reaction. The type of DNA polymerase to be used in RCA is not limited to thermostable enzymes, like the PCR-based diagnostics. On the other hand, the RCA method requires the environment to be free of contaminations as the RCA arrays are highly sensitive. Wiltshire [22]... 

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