Applicability of Birth-Death Markov Modeling for Single-Molecule Counting Using Single-Walled Carbon Nanotube Fluorescent Sensor Arrays

In recent work, the authors have shown that d(AT)15 DNA-wrapped single-walled carbon nanotubes (SWNTs) are able to detect the adsorption and desorption of single mols. of nitric oxide (NO) from the surface by quenching of the near-IR fluorescence. A central question is how to est. the local concn. from stochastic dynamics for these types of sensors. Herein, the authors employ an exact soln. to the birth-death Markov model to est. the local analyte concn. from the stochastic dynamics. Conditions are derived for the intrinsic variance displayed by identical sensor elements, and the homogeneity of the environment is assessed by comparing exptl. sensor-to-sensor variance with this limit. The authors find that d(AT)15 DNA-wrapped SWNTs demonstrate variances that are close to the idealized limit at relatively high NO concns. (19.4 μM). At 780 nM, the sensor-to-sensor variance is approx. double the idealized value, indicating marginal variation in the SWNT array. An NO adsorption coeff. of 2.6 × 10-4 [μM-1] is identified, and the authors outline how to predict the local analyte concn. from the sensor dynamics. [on SciFinder(R)]