Elemental Mass Spectrometry and Fluorescence Dual-Mode Strategy for Ultrasensitive Label-Free Detection of HBV DNA.

This work reported a simple and ultrasensitive label-free method for the detection of hepatitis B virus (HBV) DNA by combining hyperbranched rolling circle amplification (HRCA) with dual-mode detection by inductively coupled plasma mass spectrometry (ICP-MS) and fluorescence using ruthenium complex [Ru(bpy)2dppz]2+ (bpy = 2,2'-bipyridine, dppz = dipyrido [3,2-a:2',3'-c] phenazine) as a dual functional probe. An HBV DNA-initiated HRCA system was designed to realize the highly efficient amplification of HBV DNA with the generation of a mass of dsDNA. Also, the [Ru(bpy)2dppz]2+ probe was then added to intercalate into the dsDNA products, resulting in strong fluorescence recovery of the probe for fluorescence detection. Meanwhile, using a biotin-modified primer in HRCA, the dsDNA-[Ru(bpy)2dppz]2+ complexes could be captured by the avidin-coated 96-well plates, and the captured [Ru(bpy)2dppz]2+ probe was later desorbed by acid for ICP-MS detection. The linear range of the proposed method was 3.5-200 amol L-1 and the limit of detection (LOD) was 1 amol L-1 for ICP-MS detection, while the linear range was 20-500 amol L-1 and the LOD was 9.6 amol L-1 for fluorescence detection. The developed method was applied to human serum sample analysis, and the analytical results coincided very well with those obtained by the real-time polymerase chain reaction (PCR) method. The developed dual-mode label-free detection method was ultrasensitive, simple, and accurate, showing great potential for therapeutic monitoring of HBV infection.