| Techniques to fabricate heterogeneous nanoarrays of biomolecules or biomolecule coated nanoparticles have been developed. Nanoarrays of distinct DNA and protein biomolecules were fabricated by electrochemically controlling their assembly/release from Au nanoelectrodes on a chip. The surface density, ratio, and activity of the biomolecules assembled on each nanoelectrode in the array can be configured quantitatively and temporally by adjusting the electrochemical potential applied on the nanoelectrode. Nanoarrays of biomolecule coated nanoparticles were fabricated by applying electric field on nanoelectrodes to attract charged nanoparticles and immobilize them on the nanoelectrodes. If magnetic nanoparticles were used, the nanoparticles can be concentrated by magnetic field to reach a high density assembly. The assembled nanoparticles can be transferred to a biocompatible polymer.;Based on the biomolecular nanopatterning, we developed a "lock-in" fluorescence biosensing method that can detect the modulated fluorescence signal from a single molecule manipulated by an alternating electrical field. The modulated specific fluorescence signal can be efficiently extracted from background noise, and unambiguously distinguished from nonspecific fluorescence. This simple method can significantly improve the detection sensitivity and specificity down to the single molecule level, as demonstrated through a thrombin assay. |
