title: Wide dynamic range sensing with single quantum dot biosensors.
abstract: Single-particle analysis of biosensors that use charge transfer as the means for analyte-dependent signaling with semiconductor nanoparticles, or quantum dots, was examined. Single-particle analysis of biosensors that use energy transfer show analyte-dependent switching of nanoparticle emission from off to on. The charge-transfer-based biosensors reported here show constant emission, where the analyte (maltose) increases the emission intensity. By monitoring the same nanoparticles under various conditions, a single charge-transfer-based biosensor construct (one maltose binding protein, one protein attachment position for the reductant, one type of nanoparticle) showed a dynamic range for analyte (maltose) detection spanning from 100 pM to 10 μM while the emission intensities increase from 25 to 175% at the single-particle level. Since these biosensors were immobilized, the correlation between the detected maltose concentration and the maltose-dependent emission intensity increase could be examined. Minimal correlation between maltose detection limits and emission increases was observed, suggesting a variety of reductant-nanoparticle surface interactions that control maltose-dependent emission intensity responses. Despite the heterogeneous responses, monitoring biosensor emission intensity over 5 min provided a quantifiable method to monitor maltose concentration. Immobilizing and tracking these biosensors with heterogeneous responses, however, expanded the analyte-dependent emission intensity and the analyte dynamic range obtained from a single construct. Given the wide dynamic range and constant emission of charge-transfer-based biosensors, applying these single molecule techniques could provide ultrasensitive, real-time detection of small molecules in living cells.
authors.affiliation: Department of Chemistry & Biochemisty, Calvin College, 1726 Knollcrest Circle SE, Grand Rapids, Michigan 49546, United States.
authors.forename: Stacey R
authors.initials: SR
authors.lastname: Opperwall
authors.forename: Anand
authors.initials: A
authors.lastname: Divakaran
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Porter
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Christians
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Denhartigh
authors.forename: David E
authors.initials: DE
authors.lastname: Benson
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008163:Luminescent Measurements / Q000295:instrumentation*; D008320:Maltose / Q000032:analysis*; D036103:Nanotechnology / Q000295:instrumentation*; D045663:Quantum Dots
chemical_list: D008320:Maltose