title: Hybrids of a genetically engineered antibody and a carbon nanotube transistor for detection of prostate cancer biomarkers.
abstract: We developed a novel detection method for osteopontin (OPN), a new biomarker for prostate cancer, by attaching a genetically engineered single-chain variable fragment (scFv) protein with high binding affinity for OPN to a carbon nanotube field-effect transistor (NT-FET). Chemical functionalization using diazonium salts is used to covalently attach scFv to NT-FETs, as confirmed by atomic force microscopy, while preserving the activity of the biological binding site for OPN. Electron transport measurements indicate that functionalized NT-FET may be used to detect the binding of OPN to the complementary scFv protein. A concentration-dependent increase in the source-drain current is observed in the regime of clinical significance, with a detection limit of approximately 30 fM. The scFv-NT hybrid devices exhibit selectivity for OPN over other control proteins. These devices respond to the presence of OPN in a background of concentrated bovine serum albumin, without loss of signal. On the basis of these observations, the detection mechanism is attributed to changes in scattering at scFv protein-occupied defect sites on the carbon nanotube sidewall. The functionalization procedure described here is expected to be generalizable to any antibody containing an accessible amine group and to result in biosensors appropriate for detection of corresponding complementary proteins at fM concentrations.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Mitchell B
authors.initials: MB
authors.lastname: Lerner
authors.forename: Jimson
authors.initials: J
authors.lastname: D'Souza
authors.forename: Tatiana
authors.initials: T
authors.lastname: Pazina
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dailey
authors.forename: Brett R
authors.initials: BR
authors.lastname: Goldsmith
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Robinson
authors.forename: A T Charlie
authors.initials: AT
authors.lastname: Johnson
mesh_terms: D000818:Animals; D000906:Antibodies / Q000235:genetics; D014408:Biomarkers, Tumor / Q000097:blood*; D002417:Cattle; D003217:Conductometry / Q000295:instrumentation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation*; D008297:Male; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D053495:Osteopontin / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis*; D015202:Protein Engineering / Q000379:methods; D014173:Transistors, Electronic
chemical_list: D000906:Antibodies; D014408:Biomarkers, Tumor; D037742:Nanotubes, Carbon; D053495:Osteopontin