Application of field-modulated birefringence and light scattering to biosensing

Louis H. Strong; Daniel B. Hall; Clark M. Edson; Hiep-hoa Nguyen; Michael A. Whitt; Gyula Varadi

doi:10.1117/12.875342

8 February 2011 Application of field-modulated birefringence and light scattering to biosensing

Louis H. Strong, Daniel B. Hall, Clark M. Edson, Hiep-hoa Nguyen, Michael A. Whitt, Gyula Varadi

Proceedings Volume 7888, Frontiers in Biological Detection: From Nanosensors to Systems III; 78880P (2011) https://doi.org/10.1117/12.875342
Event: SPIE BiOS, 2011, San Francisco, California, United States

Abstract

Superparamagnetic nanoparticles (NPs) coated with surface ligands are shown to be an effective means to impart magnetic field modulation to optical signals from targeted receptor complexes. The modulated signals they produce can be used for a number of important high throughput applications in bio-sensing including: detecting (weaponized) viruses, screening recombinant libraries of proteins, identifying pathogenic conversions of microbes, and monitoring gene amplification. We compare the results of two dynamic methods of measuring target binding to NPs: birefringence and field modulated light scattering (FMLS). These measurements reflect complementary manifestations of NP alignment (orientation) and de-alignment (relaxation) dynamics. Birefringence originates from the specific crystalline properties of a small subset of paramagnetic NPs (for example, maghemite) when oriented in a magnetic field. Upon quenching the field, it decays at a rate exhibiting the Debye-Stokes-Einstein rotational relaxation constant of target-NP complexes. Birefringence relaxation reflects the particle dynamics of the mixed suspension of NPs, with signal components weighted in proportion to the free and complexed NP size distributions. FMLS relaxation signals, on the other hand, originate predominately from the inherent optical anisotropy of the target complexes, show little contribution from non-complexed NPs when the targets are more optically anisotropic than the NPs, and provide a more direct and accurate method for determining target receptor concentrations. Several illustrations of the broad range of applications possible using these dynamic measurements and the kind of information to be derived from each detection modality will be discussed.

Citation Download Citation

Louis H. Strong, Daniel B. Hall, Clark M. Edson, Hiep-hoa Nguyen, Michael A. Whitt, and Gyula Varadi "Application of field-modulated birefringence and light scattering to biosensing", Proc. SPIE 7888, Frontiers in Biological Detection: From Nanosensors to Systems III, 78880P (8 February 2011); https://doi.org/10.1117/12.875342

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