Fluorescent recognition of deoxyribonucleic acids by a quantum dot/meso-tetrakis(N-methylpyridinium-4-yl)porphyrin complex based on a photo induced electron-transfer mechanism

We have developed a new fluorescent probe of thioglycolic acid (TGA)-capped CdTe quantum dots (QDs) complexed with a model drug, meso -tetrakis( N -methylpyridinium-4-yl)porphyrin (TMPyP) for detecting deoxyribonucleic acids (DNAs). This probe operates with an “Off–On” mode: TMPyP quenches the photoluminescence (PL) of QDs via a photo induced electron-transfer (PIET) process; the presence of DNA can break the QD/TMPyP complexation, interrupting the PIET process, and switch on the PL of QDs. Sensitive detection of DNA with the detection limit of 0.16   nM and a linear detection range of 0.25–6.0   nM are achieved. Importantly, this probe can be used to distinguish the binding modes of DNA–TMPyP interactions, exhibiting the DNA sequence-dependent PL recovery behaviors. The obtained binding constant for poly(dA)·poly(dT) is ∼3.30   ×   10 7   L   mol −1 , which is approximately one order of magnitude larger than those for native DNAs and poly(dG)·poly(dC). Furthermore, the thymine bases preferential of the TMPyP–DNA interaction is proved by this probe.