Abstract
To detect DNA concentration, a novel fiber optic biosensor based on fluorescence quenching was designed and constructed by using lock-in amplifier for signal measurement. The sensor head was fixed on a sensing membrane prepared by the mixture of ethyl silicate, formamide, HCl and fluorescence indicator [Ru(phen)3]2+. The optimal film-forming conditions were that the contents of [Ru(phen)3]Cl2, HCl and formamide were 2.1 mg/ml, 12 % and 16 % respectively, the aging temperature and time of sol-gel solution were 4 oC and 5 d, and the film-forming temperature and time were 4 oC and 48 h, respectively. A linear relationship between the relative phase delay Δφ of sensing membrane and ctDNA concentration was observed in range from 2.0×10-9 to 4.0×10-7 M in Tris buffer, and the detection limit is 8.0×10-10 M. The biosensor had a response time of 65 s and showed good stability and repeatability.
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