Backscattering light detection of nucleic acids with tetraphenylporphyrin–Al(III)–nucleic acids at liquid/liquid interface

A backscattering light (BSL) detection assembly is constructed and applied to the determination of nucleic acids with high sensitivity and selectivity based on the measurements of BSL signals at water/tetrachloromethane (H2O/CCl4) interface. In aqueous medium of pH 3, the binary complex of of Al(III)–DNAs could be formed by the interaction of Al(III) with the phosphate group of DNAs, which then could interact with tetraphenylporphyrin (TPP) in tetrachloromethane through liquid/liquid interaction, forming a ternary complex of TPP–Al(III)–DNAs at the interface. It was observed that greatly enhanced BSL signals occurred with maximum peak at 469 nm when the ternary complex of TPP–Al(III)–DNAs were absorbed to the liquid/liquid interface. The enhanced backscattering light intensity (IBSL) is in proportion to the concentration of calf thymus DNA (ctDNA) and fish sperm DNA (fsDNA) in the range of 0.6–1200 ng ml^-1 and 1.1–1200 ng ml^-1, respectively. The limits of determination (3(sigma)) are 60 pg ml^-1 and 110 pg ml^-1, correspondingly. Artificial samples with highly interference backgrounds were determined with the recovery ranging from 94.5 to 106.7%, and relative standard deviation (R.S.D.) less than 2.40%.