Whispering-gallery-mode-based biosensing using quantum dot-embedded microspheres

Highly sensitive, miniature biosensors are desired for the development of new techniques for biological and environmental analyte sensing. One potential approach uses the detection of optical resonances, known as Whispering Gallery Modes (WGMs), from quantum dot embedded polystyrene microspheres. These modes arise from the total internal reflection of the quantum dot emission light within the high index polystyrene microsphere, to produce narrow spectral peaks, which are sensitive to refractive changes in the immediate vicinity of the microsphere surface. The high refractometric sensitivity of the WGMs in these microspheres offers potential for remote detection of molecules adsorbed onto or bound to the microsphere surface without the need for direct coupling of the light via an optical fiber. The sensitivity of these modes has been shown to exceed the theoretical sensitivity of a homogeneous microsphere, using a Mie theory model. This enhancement is believed to be due to the embedded layer of quantum dots at the surface of the microspheres. A model was developed to demonstrate that the embedded QDs could be modeled as a high index outer layer to explain the observed WGM spectra and explore the sensitivity of the modes. In this work, we extend this idea to multiple layers to model the effects of protein adsorption or binding to the surface. The theoretical results are shown to provide a close fit to our previous experimental results.

[1]  S. Arnold,et al.  Shift of whispering-gallery modes in microspheres by protein adsorption. , 2003, Optics letters.

[2]  Alexandre François,et al.  Whispering gallery mode biosensor operated in the stimulated emission regime , 2009 .

[3]  Xudong Fan,et al.  Subfemtomole detection of small molecules with microsphere sensors. , 2005, Optics letters.

[4]  S. Arnold,et al.  Whispering-gallery-mode biosensing: label-free detection down to single molecules , 2008, Nature Methods.

[5]  Stephen Arnold,et al.  Whispering-gallery modes in a microsphere coated with a high-refractive index layer: polarization-dependent sensitivity enhancement of the resonance-shift sensor and TE-TM resonance matching , 2007 .

[6]  Michael Himmelhaus,et al.  Whispering gallery mode biosensors in the low-Q limit , 2008 .

[7]  H. Beier,et al.  Whispering Gallery Mode Biosensors Consisting of Quantum Dot-Embedded Microspheres , 2009, Annals of Biomedical Engineering.

[8]  B. R. Johnson,et al.  Theory of morphology-dependent resonances : shape resonances and width formulas , 1993 .

[9]  Zhanfeng Cui,et al.  Effect of pH on the Adsorption of Bovine Serum Albumin at the Silica/Water Interface Studied by Neutron Reflection , 1999 .

[10]  Xiaogang Peng,et al.  Formation of high-quality CdTe, CdSe, and CdS nanocrystals using CdO as precursor. , 2001, Journal of the American Chemical Society.

[11]  Hongying Zhu,et al.  Aptamer Based Microsphere Biosensor for Thrombin Detection , 2006, Sensors (Basel, Switzerland).

[12]  Frank Vollmer,et al.  Perturbation approach to resonance shift of whispering gallery modes in a dielectric microsphere as a probe of a surrounding medium , 2003 .

[13]  Hope T. Beier,et al.  Modeling whispering gallery modes in quantum dot embedded polystyrene microspheres , 2010 .

[14]  Robert E. Benner,et al.  Morphology-Dependent Resonances , 1988 .

[15]  Dieter Braun,et al.  Protein detection by optical shift of a resonant microcavity , 2002 .

[16]  Lord Rayleigh,et al.  CXII. The problem of the whispering gallery , 1910 .

[17]  S. Nie,et al.  Quantum dot bioconjugates for ultrasensitive nonisotopic detection. , 1998, Science.

[18]  Marcus J. Swann,et al.  Real time, high resolution studies of protein adsorption and structure at the solid liquid interface using dual polarization interferometry , 2004 .

[19]  Stephen Arnold,et al.  Enhancing the sensitivity of a whispering-gallery mode microsphere sensor by a high-refractive-index surface layer , 2006 .

[20]  Ian M. White,et al.  Refractometric sensors based on microsphere resonators , 2005 .

[21]  Paul Mulvaney,et al.  Detection of unlabeled oligonucleotide targets using whispering gallery modes in single, fluorescent microspheres. , 2007, Small.

[22]  A. R. Jones.  Optical Effects Associated with Small Particles , 1989 .

[23]  Shuming Nie,et al.  Quantum dot-encoded mesoporous beads with high brightness and uniformity: rapid readout using flow cytometry. , 2004, Analytical chemistry.

[24]  Shuo Pang,et al.  Quantum dot-embedded microspheres for remote refractive index sensing. , 2008, Applied physics letters.