Surface plasmons resonance transduction

Electronic and optical transduction of the formation of antigen-antibod/ affinity compleK-es on transducers (A) Amperometric transduction at an electrode (R /R is a redox label in the riec-trolyte solution). (B) Tnuisduction by faradic impedance >ectro cc. (C) hterogravimetric tpiartz crystal microbabnce (QCM) transduction in the presence of a piezoelectric quartz crystal. (D) Surface plasmon resonance transduction. 

Other teehniques used for studying molecular interactions between polymers and mueus inelude ultracentrifugation, surface plasmon resonance, and electromagnetic transduction [4,34]. Ilium and co-workers [35] investigated the interaction of chitosan microspheres using turbidimetric measurements and adsorption studies of mucin to the mierospheres. 

The detection and quantification of the presence of biomolecules at the surface is based on specific interactions taking place in the evanescent field, generated by the total internal reflectance or by the surface plasmon resonance. The latter is the key transduction principle in the optical bioanalysis and biosensing area (Narayanaswamy and Wolfbeis, 2004). Launched in the early 1980s in Sweden,... 

Fiber-optic biosensors are analytical devices in which a fiber optic device serves as a transduction element. The usual aim of fiber-optic biosensors is to produce a signal proportional to the concentration of target analyte to which the biological element reacts. Fiber-optic biosensors are based on the transmission of light along silica glass fiber, or POF to the site of analysis. They can be used in combination with different types of spectroscopic technique, e.g. absorption, fluorescence, phosphorescence, or surface plasmon resonance (SPR) (14). 

An optical transduction method that is often used with ultrathin hlms, such as LB hlms, is that of surface plasmon resonance [30, 31]. Surface plasma waves are collective oscillations of the free electrons at the boundary of a metal and a dielectric. These can be excited by means of evanescent electromagnetic waves. This excitation is associated with a minimum in the intensity of the radiation reflected from the thin him system, called surface plasmon resonance (SPR). The sensitivity of SPR is noteworthy, and changes in refractive index of 10 may be monitored thus the technique compares favorably with ellipsometry. The method has been used with LB hlms to provide both gas detectors [29] and sensors for metal ions in solution [32]. 

Different transduction methodologies are employed for the VOCs detection, such as electrical conductivity [9], piezoelectric quartz crystal microbalance (QCM) [10-14], surface acoustic wave [15,16], field-effect transistor (FET) [17], surface plasmon resonance (SPR) [18,19], Kelvin probe [20], color variation [8,21,22], and UV-vis absorption [3,23,24], in the physical properties of the sensing elements. 

Schuster, S.C., Swanson, R.V., Alex, L.A., Bourret, R.B. and Simon, M.I. (1993). Assembly and function of a quaternary signal transduction complex monitored by surface plasmon resonance. Nature 365, 343-347,... 

Apart from the classification based on sensing mechanisms, biosensors are classified into three categories considering the transduction mechanism used. They are optical, electrochenfical, or electrical. The optical transduction mechanism includes fluorescence, chemilununescence, interferometry, and surface plasmon resonance. These techniques involve either the production of light from chemical reactions or the change in refractive index at the interface of biosensing materials. 

Biomolecule detectors incorporate a biorecognition device capable of selectively recognizing the analyte of interest in connection with a signal transducer and a suitable output device. Transduction methods include a variety of optical (surface plasmon resonance [SPR], fluorescence), electrochemical (voltammetry, impedance, field effect), mechanical (cantilever, surface probe microscopy), and mass-based systems (quartz crystal microgravimetry [QCM], mass spectrometry). Selection of the appropriate transduction system is partially determined by the nature of information sought (quantitative or qualitative), the analyte (concentration, molecular weight), the sample size, and assay timeline. 

NCs could be employed for in vivo applications. The UV-Vis absorption of the Cu2-xSe NCs showed a broad absorption peak at 970 mn which was attributed to the surface plasmon resonance. When these NCs were irradiated with a 800 nm laser for 5 min, they exhibited a photothermal transduction efficiency of 22% which is equivalent to Au nanorods (21%) and relatively higher than Au nanoshells (13%). Cu2.xSe NCs were effective in the destruction of cancer cells, and hence are promising candidate for photo-thermal applications. 

Raitman OA, Katz E, Willner I, Chegel VI, Popova GV. Photonic transduction of athree-state electronic memory and of electrochemical sensing of NADH using surface plasmon resonance spectroscopy. Angew Chem Int Ed 2001 40 3649-3652. 

Chegel V, Raitman O, Katz E, Gabai R, Willner I. Photonic transduction of electro-chemically-triggered redox-functions of polyaniline films using surface plasmon resonance spectroscopy. Chem Commun 2001 883-884. 

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