title: Subfemtomole detection of small molecules with microsphere sensors.
abstract: We investigated the feasibility of using a silica microsphere sensor for detection of small molecules. Using the silica molecules (60 Da) at the sphere's surface as a model system, we measured the spectral shifts in the whispering-gallery modes (WGMs) when the sphere size was decreased by a hydrofluoric acid (HF) solution. The results demonstrate that our sensor is capable of detecting a 4 pm (or 0.01 layer of silica) decrease in sphere radius, corresponding to a change of 0.4 fmol silica molecule. These results suggest that small molecules can be detected in trace quantities at the surface of an optical microsphere sensor.
authors.affiliation: Department of Biological Engineering, University of Missouri-Columbia, Missouri 65211, USA.
authors.forename: Ian M
authors.initials: IM
authors.lastname: White
authors.forename: Niranjan M
authors.initials: NM
authors.lastname: Hanumegowda
authors.forename: Xudong
authors.initials: X
authors.lastname: Fan
mesh_terms: D000465:Algorithms; D001704:Biopolymers / Q000032:analysis*; D015374:Biosensing Techniques / Q000379:methods*; D005240:Feasibility Studies; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008832:Microchemistry / Q000379:methods*; D008863:Microspheres; D015336:Molecular Probe Techniques; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D010316:Particle Size; D012031:Refractometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001704:Biopolymers