RESUMO
Nanoscale sensing elements offer promise for single-molecule analyte detection in physically or biologically constrained environments. Single-walled carbon nanotubes have several advantages when used as optical sensors, such as photostable near-infrared emission for prolonged detection through biological media and single-molecule sensitivity. Molecular adsorption can be transduced into an optical signal by perturbing the electronic structure of the nanotubes. Here, we show that a pair of single-walled nanotubes provides at least four modes that can be modulated to uniquely fingerprint agents by the degree to which they alter either the emission band intensity or wavelength. We validate this identification method in vitro by demonstrating the detection of six genotoxic analytes, including chemotherapeutic drugs and reactive oxygen species, which are spectroscopically differentiated into four distinct classes, and also demonstrate single-molecule sensitivity in detecting hydrogen peroxide. Finally, we detect and identify these analytes in real time within live 3T3 cells, demonstrating multiplexed optical detection from a nanoscale biosensor and the first label-free tool to optically discriminate between genotoxins.
Assuntos
Técnicas Biossensoriais/métodos , Células/efeitos dos fármacos , Medições Luminescentes/métodos , Nanotubos de Carbono/química , Células 3T3 , Alquilantes/farmacologia , Animais , Técnicas Biossensoriais/instrumentação , Citotoxinas/farmacologia , Dano ao DNA/efeitos dos fármacos , DNA de Cadeia Simples/efeitos dos fármacos , Raios Infravermelhos , Luminescência , Substâncias Luminescentes/análise , Substâncias Luminescentes/efeitos da radiação , Medições Luminescentes/instrumentação , Camundongos , Nanotecnologia/métodos , Espécies Reativas de Oxigênio/farmacologia , Sensibilidade e Especificidade , Espectrofotometria Infravermelho/instrumentação , Espectrofotometria Infravermelho/métodos , Eletricidade EstáticaRESUMO
The transition of DNA secondary structure from an analogous B to Z conformation modulates the dielectric environment of the single-walled carbon nanotube (SWNT) around which it is adsorbed. The SWNT band-gap fluorescence undergoes a red shift when an encapsulating 30-nucleotide oligomer is exposed to counter ions that screen the charged backbone. The transition is thermodynamically identical for DNA on and off the nanotube, except that the propagation length of the former is shorter by five-sixths. The magnitude of the energy shift is described by using an effective medium model and the DNA geometry on the nanotube sidewall. We demonstrate the detection of the B-Z change in whole blood, tissue, and from within living mammalian cells.
