Photothermal biosensor for HPV16 based on strand-displacement amplification and gold nanoparticles using a thermometer as readout.

Gold nanoparticles (AuNPs) in aggregated state have a strong near infrared region (NIR) absorption and the causes a much stronger photothermal effect than that of the dispersed AuNPs. Strand-displacement amplification (SDA) can produce large amount of single-stranded DNA (ssDNA), which in turn effectively prevent AuNPs from aggregation. In this study, these characteristics had been applied to design a photothermal biosensor for human papilloma virus (HPV and HPV16 were chosen as model target) detection. In the absence of HPV16, AuNPs was in the aggregated state and large temperature rise can be detected after the irradiation by 808 nm laser. The presence of HPV16 triggers the SDA reaction with the help of Bst DNA polymerase and Nt.BstNBI nicking endonuclease resulting in the production of large amounts of ssDNA; this protects unmodified AuNPs from salt-induced aggregation. Therefore, AuNPs was in a dispersed state and the temperature change was not significant after the irradiation of 808 nm laser. The difference of the temperature changing can be applied for the quantitative detection of HPV16 using a thermometer as readout. The linear response range is 1.0 fM ~ 50 pM with a detection limit of 0.3 fM. The proposed method has been applied to detect HPV16 in clinical cervical sample and is competent for clinical analysis.