Sensitivity biochemically based sensors

Green, W. Scheuer, J. DeRose, G. Yariv, A., Ultra sensitive biochemical sensor based on circular bragg micro cavities, CLEO/QELS 2005, Baltimore, Maryland, paper CPDA7... 

Aslan K, Holley P, Geddes CD (2006) Microwave-accelerated metal-enhanced fluorescence (MAMEF) with silver colloids in 96-well plates Application to ultra fast and sensitive immunoassays, high throughput screening and dmg discovery. J Immunol Methods 312 137-147 Matveeva E, Gryczynski Z, Malicka J et al (2004) Metal-enhanced fluorescence immunoassays using total internal reflection and silver-coated surfaces. Anal Biochem 334 303-311 Blue R, Kent N, Polerecky L (2005) Platform for enhanced detection efficiency in luminescent-based sensors. Electron Lett 41 682-684... 

There are several techniques suitable for the cantilever response read-out as the optical beam deflection, piezoresistivity, piezoelectricity, interferometry and capacitance, among the most important. However, the majority of the biochemical applications carried out with the cantilever-based sensor are based in the optical beam deflection method, because of its high sensitivity and its simplicity. 

High importance must also be placed on validation of biosensors and immunosensors from the transducer type point of view. Because the biochemical reaction is very sensitive, only the sensors based on an ampero-metric, fluorescent, or chemiluminescent transducer may be validated. 

The type of enzyme sensor described above is highly selective and can be sensitive in operation. There are obvious applications for the determination of small amounts of oxidizable organic compounds. However, it is perhaps too early to give a realistic assessment of the overall importance of enzyme sensors to analytical chemistry. This is especially so because of parallel developments in other biochemical sensors which may be based upon a quite different physical principle. 

Fluorescence and chemiluminescence sensors are considered the most sensitive in the class of optical sensors. They have a higher selectivity because the chemiluminescent and fluorescent reactions take place in certain medium conditions, and only a limited group of ions and molecules can be involved. When the selectivity of this type of sensor is not sufficient, the quality of analysis can be improved by using a biochemical reaction such as an enzymatic reaction (chemiluminescence- or fluorescence-based biosensors) or an immunoreaction (chemiluminescence- or fluorescence-based immunosensors). By using these types of optical sensors the chemical analysis becomes most sensitive and selective.265... 

In a sensor experiment (e.g., in a typical biochemical experiment) the sensor has been functionalized with a sensitive film, which is in contact with an analyte containing buffer solution. The new resonance frequencies / can be calculated when replacing Ls and Rs by =Ls + Lc + Liiq and R = Rs + Knq, respectively (neglecting Qiq and Guq). Usually frequency shifts are determined and of interest only. Some example data are added to Table 2. Series and parallel resonance frequency shifts vary by a few percent. All the parallel resonance frequencies are very much affected by external capacitance (values in brackets). The same holds for all frequency shifts in a Hquid except /s. Oscillators based on parallel resonance should not be used because stray capacitance is hardly to avoid and hardly to keep constant in an experimental setup. Deviations of/r and/m from s are also ampHfied by external capacitance. 

---