title: Label-free and non-contact optical biosensing of glucose with quantum dots.
abstract: We present a label-free, optical sensor for biomedical applications based on changes in the visible photoluminescence (PL) of quantum dots in a thin polymer film. Using glucose as the target molecule, the screening of UV excitation due to pre-absorption by the product of an enzymatic assay leads to quenching of the PL of quantum dots (QDs) in a non-contact scheme. The irradiance changes in QD PL indicate quantitatively the level of glucose present. The non-contact nature of the assay prevents surface degradation of the QDs, which yields an efficient, waste-free, cost-effective, portable, and sustainable biosensor with attractive market features. The limit of detection of the demonstrated biosensor is ~3.5 µm, which is competitive with existing contact-based bioassays. In addition, the biosensor operates over the entire clinically relevant range of glucose concentrations of biological fluids including urine and whole blood. The comparable results achieved across a range of cost-affordable detectors, including a spectrophotometer, portable spectrometer, and iPhone camera, suggest that label-free and visible quantification of glucose with QD films can be applied to low-cost, point-of-care biomedical sensing as well as scientific applications in the laboratory for characterizing glucose or other analytes.
authors.affiliation: E.L. Ginzton Laboratory and Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Saara A
authors.initials: SA
authors.lastname: Khan
authors.affiliation: E.L. Ginzton Laboratory and Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Gennifer T
authors.initials: GT
authors.lastname: Smith
authors.affiliation: E.L. Ginzton Laboratory and Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA; Advanced Center for Laser Science and Spectroscopy, Department of Physics, Hampton University, Hampton, VA 23668, USA.
authors.forename: Felix
authors.initials: F
authors.lastname: Seo
authors.affiliation: E.L. Ginzton Laboratory and Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Audrey K
authors.initials: AK
authors.lastname: Ellerbee
mesh_terms: D015374:Biosensing Techniques / Q000191:economics / Q000295:instrumentation*; D001786:Blood Glucose / Q000032:analysis*; D040421:Cell Phone; D004867:Equipment Design; D005947:Glucose / Q000032:analysis*; D006029:Glycosuria / Q000652:urine*; D006801:Humans; D057230:Limit of Detection; D008163:Luminescent Measurements / Q000191:economics / Q000295:instrumentation*; D045663:Quantum Dots / Q000737:chemistry*; D014867:Water / Q000032:analysis
chemical_list: D001786:Blood Glucose; D014867:Water; D005947:Glucose
keywords: Biosensor; Glucose; Hexokinase–glucose 6-phosphate dehydrogenase; Optical transduction; Quantum dot