Biomedical subjects
Publications and source records attributed to J N Roe.
This article reviews the recent biosensor developments for medical applications, focusing on the various biological recognition elements used in biosensors and the systems transduction mechanisms. Available instruments utilizing biosensor technology are also examined from a commercial perspective.
A fluorescence fibre optic sensor has been developed for measurement of the potassium concentration in aqueous solution based on the change in optical absorbance of the hydrophobic indicator 7-decyl-2-methyl-4-(3',5'-dichlorophen-4'-one)indonaphth-1-o l (MEDPIN). The sensor was constructed by dipping the distal end of a single optical fibre in a poly(vinyl chloride) (PVC) coating solution containing MEDPIN, a plasticiser, the ionophore valinomycin and the fluorescent dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine perchlorate [DilC18(5)]. The change in the absorbance of MEDPIN induced by potassium was detected from the quenching of the fluorescence of DilC18(5) due to energy transfer. Glass slides dipped in the PVC coating solution were used to establish the optical properties of the sensor. The potassium concentration was detected by the absorbance of MEDPIN at 650 nm and by the quenching of the DilC18(5) fluorescence by MEDPIN. The fluorescence intensity and lifetime of DilC18(5) decreased by ca. 40% with the addition of 33 mM KCl, indicating a resonance energy transfer mechanism. Experiments with the fibre optic sensor showed a decrease in the fluorescence of 57% with increasing potassium concentration (0-5 mM) at pH 7.45. The potassium concentration giving a 50% decrease in the fluorescence (Kd) for the most sensitive probe was 0.05 mM KCl. The value of Kd was increased to 1.3 mM when the plasticiser was changed from 2-nitrophenyl octyl ether to tris(2-ethylhexyl)phosphate; however, the 90% response time increased from 10 s to 4.2 min.(ABSTRACT TRUNCATED AT 250 WORDS)
An assay was developed for K+ in aqueous solution at neutral pH. The method was based on the change in optical absorbance of the hydrophobic indicator 7-(n-decyl)-2-methyl-4-(3',5'-dichlorophen-4'-one)indonaphthl++ +-1-ol (MEDPIN) in phospholipid vesicles. Formation of a ternary complex between a valinomycin-K+ pair and the anionic form of MEDPIN in the bilayer resulted in an absorption band at 584 nm. K+ concentration was determined by monitoring the MEDPIN absorbance at 584 nm and MEDPIN quenching of lissamine rhodamine B sulfonylphosphatidylethanolamine (L-RhB-PE) fluorescence by an energy-transfer mechanism. Both the fluorescence intensity and lifetime of L-RhB-PE decreased by more than 25% upon addition of 50 mM K+. Kinetic studies using stopped-flow photometry showed a single-exponential reaction of MEDPIN and valinomycin in vesicles with aqueous K+ (maximum rate 1.7 s-1) that was dependent upon [valinomycin] and [K+]. The lipid surface charge was shown to influence the ratio of anionic to neutral MEDPIN at constant pH, and to alter the sensitivity of MEDPIN absorbance to aqueous [K+]. A 1:20 neutral/negative lipid mole ratio was optimal for K+ detection at pH 7.4. Spectroscopic and kinetic data suggest that the optical response of MEDPIN to K+ involves the formation of a ternary complex between K+, valinomycin and MEDPIN.