A membrane-based electrochemical nanobiosensor sensitive toward whole viral particles is fabricated by forming a submicrometer thick nanoporous alumina membrane over a platinum disk electrode. Antibody probe molecules are physically adsorbed onto the walls of the membrane nanochannels. The sensing signal is based on the monitoring of the electrode's Faradaic current response toward ferrocenemethanol, which is extremely sensitive to the formation of immunocomplex within the nanoporous membrane. This nanobiosensor is demonstrated for the sensing of West Nile virus protein domain III (WNV-DIII) and the inactivated West Nile viral particle, using anti-WNV-DIII immunoglobulin M (IgM) as the biorecognition probe. The detection of the viral protein and the particle are logarithmically linear up to 53 pg mL(-1) (R(2) = 0.99) and 50 viral particles per 100 mL (R(2) = 0.93) in pH 7, with extremely low detection limits of 4 pg mL(-1) and ca. 2 viral particles per 100 mL, comparable to sensitivities of polymerase chain reaction techniques. The relative standard deviation (RSD) of whole viral particle detection in whole blood serum is 6.9%. In addition, the simple nanobiosensor construction procedure, minimal sample preparation, and short detection time of 30 min are highly attractive properties and demonstrate that the detection of a wide range of proteins and viruses can be achieved.
Dalgliesh, Toh & Work (1952) have shown that two substances are responsible for the 'enteramine activity' produced on the rat's atropinized colon by acetone extracts of gastro-intestinal mucosa. The substance responsible for the main part of activity was identified as 5-hydroxytryptamine; the other principle has not been isolated but appeared to be another related indole derivative. This identification of 5-hydroxytryptamine in gastro-intestinal mucosal extracts confirms a suggestion made by Erspamer that the enteramine activity of such extracts and of those of the posterior salivary glands of octopus and of skin of amphibia are due to the same active principle. This was isolated from the latter sources and identified as 5-hydroxytryptamine (Erspamer & Asero, 1951, 1952. 5-Hydroxytryptamine has also been isolated from ox serum under the name of serotonin (Rapport, 1949).The present paper deals with the assay of extracts containing 5-hydroxytryptamine and substance P and the distribution of 5-hydroxytryptamine in the gastro-intestinal wall.The atropinized rat's colon provided a sensitive preparation for assaying tissue extracts for 5-hydroxytryptamine in the presence of acetylcholine, histamine and substance P. The guinea-pig's ileum under atropine and mepyramine contracted to 5-hydroxytryptamine and substance P, but could be rendered insensitive to 5-hydroxytryptamine by tryptamine (Gaddum, 1952); it could then be used for the assay of substance P in the presence of 5-hydroxytryptamine. * Singapore, Colonial Development and Welfare Scholar.
DISTRIBUTION OF 5-HYDROXYTRYPTAMINE
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METHODSThe rat's colon and the guinea-pig's ileum were suspended in 18 ml. baths. In order to reduce spontaneous activity of the rat's colon, the Ca++ content of the bath fluid was reduced and its temperature kept at 22-24°C. The method has been described by Dalgliesh et al. (1952). The guinea-pig's ileum was suspended in 18 ml. Tyrode solution at 340 C and, to render the preparation insensitive to acetylcholine and histamine, 04 Fg atropine sulphate and 1 i&g mepyramine maleate were added to the bath fluid each time it was renewed. To render the preparation insensitive to 5-hydroxytryptamine, 200jug tryptamine hydrochloride were added to the bath and kept in it until the tryptamine contraction had passed off. Sometimes another 200eug were added after 2-3 min, to see if the preparation had become insensitive to the stimulating action of tryptamine itself or of 5-hydroxytryptamine. When this condition was attained, 200,ug tryptamine were added to the bath fluid each time it was renewed.A standard powder of substance P was prepared according to the method described by Euler (1942) with slight modification introduced by Dalgliesh et al. Substance P activity is expressed in mg of this standard preparation. The 5-hydroxytryptamine activity was assayed against a preparation of serotonin creatinine sulphate which was kindly supplied to us by Dr R. K. Richards of Abbott Laboratories. Only about 50% of the serotonin complex consists of the base...
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