Label-free electrical detection of pyrophosphate generated from DNA polymerase reactions on field-effect devices.

We introduce a label-free approach for sensing polymerase reactions on deoxyribonucleic acid (DNA) using a chelator-modified silicon-on-insulator field-effect transistor (SOI-FET) that exhibits selective and reversible electrical response to pyrophosphate anions. The chemical modification of the sensor surface was designed to include rolling-circle amplification (RCA) DNA colonies for locally enhanced pyrophosphate (PPi) signal generation and sensors with immobilized chelators for capture and surface-sensitive detection of diffusible reaction by-products. While detecting arrays of enzymatic base incorporation reactions is typically accomplished using optical fluorescence or chemiluminescence techniques, our results suggest that it is possible to develop scalable and portable PPi-specific sensors and platforms for broad biomedical applications such as DNA sequencing and microbe detection using surface-sensitive electrical readout techniques.

Non-covalent attachment of proteins to single-walled carbon nanotubes.

A method for the non-covalent attachment of proteins to single-walled carbon nanotubes (SWNTs) is described. In this method, the protein is adsorbed to SWNTs that are suspended using sodium cholate, a surfactant and bile salt. The sodium cholate is then removed by dialysis with retention of the protein on the SWNTs.

Adsorption of glucose oxidase onto single-walled carbon nanotubes and its application in layer-by-layer biosensors.

In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the redox enzyme glucose oxidase (GOX) onto single-walled carbon nanotubes (SWNT). By this method, solutions of dispersed and debundled SWNTs were prepared that remained stable for 30 days and which retained 75% of the native enzymatic activity. We also demonstrate that GOX-SWNT conjugates can be assembled into amperometric biosensors with a poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)] redox polymer (PVP-Os) through a layer-by-layer (LBL) self-assembly process.