Visual detection of Pb2+ using strip biosensor based on PS2M aptamer and sensitivity enhancement probe
PS2M aptamer was selected as sensing element to construct Pb 2+ strip biosensor, and for the first time, AuNP-DNA polymer was used as sensitivity enhancement probe (SEP) to improve sensitivity. Pb 2+ separated the double-strand formed by PS2M and its complementary sequence at Anti-PS2M and induced PS2M to form G-quadruplex structure, then single-strand Anti-PS2M was released. When migrated along the strip, sequence at one end of Anti-PS2M hybridized with AuNP-DNA probe G immobilized on conjugate pad, when the composite migrated to test zone (TZ), other end of Anti-PS2M hybridized with biotin-DNA probe T on TZ to form sandwich structure. Subsequent SEP hybridized with the remaining oligonucleotides of AuNP-DNA probe G on TZ thus enhanced the signal. After optimization, the false positive result could be eliminated and the best signal value could be obtained. The results showed that the limit of detection of Pb 2+ strip biosensor was 2.5 nM by adding the sensitivity enhancement probe, which was 40 times better than that strip without enhancement. The test strip showed good results in the direct detection of soil and lake samples, presenting good practical value. In addition, the cost of this strip biosensor was low, with good market prospect.
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