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Modelling of Refractive Index Changes Due to Molecular Interactions

Varma, Manoj (2016) Modelling of Refractive Index Changes Due to Molecular Interactions. In: Conference on Biophysics, Biology, and Biophotonics - The Crossroads, FEB 13-14, 2016, San Francisco, CA.

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Official URL: http://dx.doi.org/10.1117/12.2211662


There are a large number of sensing techniques which use optical changes to monitor interactions between molecules. In the absence of fluorophores or other labels, the basic signal transduction mechanism relies on refractive index changes arising from the interactions of the molecules involved. A quantitative model incorporating molecular transport, reaction kinetics and optical mixing is presented which reveals important insights concerning the optimal detection of molecular interactions optically. Although conceptually simple, a comprehensive model such as this has not been reported anywhere. Specifically, we investigate the pros and cons of detecting molecular interactions in free solution relative to detecting molecular interactions on surfaces using surface bound receptor molecules such as antibodies. The model reveals that the refractive index change produced in surface based sensors is 2-3 orders of magnitude higher than that from interactions in free solution. On the other hand, the model also reveals that it is indeed possible to distinguish specific molecular interactions from non-specific ones based on free-solution bulk refractometry without any washing step necessary in surface based sensors. However, the refractive index change for free solution interactions predicted by the model is smaller than 10(-7) RIU, even for large proteins such as IgG in sufficiently high concentrations. This value is smaller than the typical 10(-6) RIU detection limit of most state of the art optical sensing techniques therefore requiring techniques with substantially higher index sensitivity such as Back Scattering Interferometry.

Item Type: Conference Proceedings
Series.: Proceedings of SPIE
Additional Information: Copy right for this article belongs to theSPIE-INT SOC OPTICAL ENGINEERING, 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA
Keywords: Optical biosensors; refractive index resolution; bulk fluid sensing
Department/Centre: Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited: 19 Aug 2016 09:20
Last Modified: 19 Aug 2016 09:20
URI: http://eprints.iisc.ac.in/id/eprint/54283

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