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 (I_BSL) 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 (3σ) 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%.