Biomolecules detection

Biomolecules-functionalized CNTs can result in characteristic electric conductivity changes of CNTs (Hou et al., 2003), which may be developed into specific biosensor for ultrasensitive detection of biomolecules such as DNA molecules, bacteria and vims, etc. We also observed that oligo DNA-filled SWCNTs appeared as characteristic Electric Resistance peaks as shown in Fig. 9.22, which also may be used as biosensor to detect biomolecules or sequence DNA sequences. 

OFDs can be divided into two subclasses (1) optical fiber chemical detectors (OFCD) which detect the presence of chemical species in samples, and (2) optical fiber biomolecular detectors (OFBD) which detect biomolecules in samples. Each subclass can be divided further into probes and sensors, and bioprobes and biosensors, respectively. As a result of the rapid expansion of optical research, these terms have not been clearly defined and to date, the terms probe and sensof have been used synonymously in the literature. As the number of publications increases, the terminology should be clarified. Although both probes and sensors serve to detect chemicals in samples, they are not identical. The same situation exists with bioprobes and biosensors. Simply, probes and bioprobes are irreversible to the analyte s presence, whereas sensors and biosensors monitor compounds reversibly and continuously. 

In a very general sense, Stephenson has defined the term bioprobes as. functional molecules or devices that provide information about biological systems. The high kinetic and thermodynamic stability of many organo-metallic complexes, in addition to their electronic and spectroscopic properties, have spurred their use in numerous sensor applications. Among those are sensors which involve biomolecules, or which detect biomolecules. In this chapter, only a few selected examples are presented as an introduction to the field. Organometallic biosensors are comprehensively summarized in four chapters in a recent book on bioorganometallic chemistry. A more... 

Another application involves capillary electrophoresis (CE) used to separate ionic species based on their size-to-charge ratio in microchannels filled with electrolytes. Various dyes have been used such as Rhodamine B, Cy3, and Topro-5 to detect biomolecules and DNA. LODs of 100-200 nM have been reported (Table 1, 5th, 8th and 13th rows) [6, 9, 13]. 

The transducers producing electrical equivalents of the changes in passive components are suitable for miniaturized systems, which translate the changes in chemical and biological analytes into resistive, piezoelectric, capacitive, or inductive variations. Such methods are suitable for detecting biomolecules without biochemical reactions... 

The resistive-type sensors measure strain-related mechanical properties such as strain, force, acceleration, and pressure-utilizing piezoresistive properties of sensitive film resistors [2,14,38,39]. These sensors are also incorporated as biosensors for detecting biomolecules. The electrode configuration is the same as in electrochemical transducers, but it measures the change of resistance when biomolecules interact with the biologically sensitive elements [2]. The piezoresistive microcantilever sensors are also extensively studied for biosensing. The piezoresistive sensors. 

The unique photonic and condnctive properties of some nanoparticles can be employed to detect biological recognitions on a surface. With dimensions similar to those of biomolecnles, nanoparlicles are a natural choice for detecting biomolecules, which can be nsed in both electrochemically and optically based biosensors. Upon the assembly of nanoparticles on a solid surface, the biomolecules adsorbed on the surfaces of nanoparlicles can be detected by means of surface plasmon resonance (SPR), surface enhanced Raman spectroscopy (SERS), and surface-enhanced fluorescence spectroscopic techniques. Furthermore, the unique size-controlled optical properties of semiconductor nanoparticles imply that the organization of combinatorial hbraries of biomolecule-semiconductor nanoparticle hybrid systems or the assembly of these hybrids in array configurations may lead to the high-throughput parallel analysis of numerous analytes [53]. 

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