Label-Free Fluorescent Determination of Simian Virus 40 Using Triplex DNA and G-Quadruplex/N-Methyl Mesoporphyrin IX

Simian virus 40 (SV40) causes multiple diseases due to its low immunogenicity and strong infectivity. Here, the development of a label-free fluorescent sensor designed to detect double-stranded DNA (dsDNA) via a functionalized molecular beacon (MB) produced using triplex DNA and guanine (G)-quadruplexes is described. A SV40-specific dsDNA sequence was used as the target dsDNA (T-dsDNA). The MB was designed to comprise a G-quadruplex sequence, a complementary homopyrimidine sequence for T-dsDNA, and a partially complementary sequence for G-quadruplex sequence. Addition of T-dsDNA forces the MB to unfold, forming triplex DNA, and releasing the G-quadruplex sequence that binds to N-methyl mesoporphyrin IX (NMM), producing a signal. The G-quadruplex/NMM complex augments the signal at 610 nm and allows qualitative SV40 detection. Under optimal conditions, this strategy demonstrates a low limit of detection (0.4 nM). Compared to traditional biosensors, this sensor is enzyme-free, rapid, selective, sensitive, and was used to determine T-dsDNA in serum, suggesting that this strategy has applications in clinical analysis and for other viruses.