Investigation On The Optical Fiber Biosensor For The Detection Of Cardiac Troponin I

Cardiac troponin I（cTnI）,a regulatory protein unique to heart muscle,is released to thebloodstream after myocardial necrosis, which is one of the most specific and sensitivemarkers of acute myocardial infarction （AMI）. Along with the rise of nanometer materialsscience, nano-scale metal particles show potential applications in many fields because oftheir unique optical and electrical properties, which attract the interest of scientists greatly.And then, the applications of the localized surface plasmon resonance（LSPR）effect onnoble metal nanoparticles have been a research hot-spot during recent years.In this paper, the localized surface plasmon resonance effect is investigated, and a newbiosensor to measure cTnI and monitor the real time biomolecular interaction dynamicallyis designed based on the properties of optical fiber sensing technology and the LSPR effectof silver nanoparticles.Silver nanoparticles are prepared by microwave synthesizing method and absorbed on theoptical fiber by chemical self-assembly technology. Thus, the localized surface plasmonresonant（LSPR）sensor is developed, which is proved by extinction spectra and the SEMimage．The sensing sensitivity reaches178±8nm/RIU by measuring the response ofrefractive index on environment dielectric. The experimental result indicates that thesensitivity of this sensor is influenced by nanoparticles aggregation. After fractional silvernanoparticles clumping together, half band width of spectra become wider; the newcharacteristic peaksappear; and the shift in the peak extinction wavelength of the LSPRband as a function of the refractive index of the solution reduced to120.210nm/RIU.The goat anti-rabbit IgG modified optical fiber LSPR sensor is employed to detect therabbit IgG. The entire dynamics process of nonspecific adsorption and rabbit IgG specificimmune adsorption are collected, which shows good local refractive index sensingproperties of the sensor.The novel optical fiber LSPR biosensor coated with a layer membrane of staphylococcalprotein A （SPA） is modified by mouse anti-hcTnI monoclonal antibodywhich can be usedto monitor the real time biomolecular affinity interaction ofmonoclonal antibody and cTnI.The experimental result indicates: human cardiac troponin I is determined in theconcentration range of20¹20ng/ml;the sensor has no response to the interferedproteins;the affinity constant of mouse anti-hcTnI monoclonal antibody is1.713× 10^-M^-1; the lowest detection concentration of cTnI is supposed to be20ng/ml which canbe improved to be10ng/ml by the sandwich immunoassay method.