Biophotonics '09: Lecture by Prof. Kishan Dholakia

Optical micromanipulation for biophotonics

Professor Kishan Dholakia

School of Physics and Astronomy
University of St Andrews
North Haugh
Fife, Scotland
KY16 9SS

Tel: +44 1334 463184
Fax: +44 1334 463104
E-mail: kd1@st-andrews.ac.uk

Web: http://www.st-andrews.ac.uk/~atomtrap/
Web: http://www.st-andrews.ac.uk/~biophot/

Abstract

Key words: optical trapping, two photon excitation, biophotonics, single molecule studies, optical sorting, fractionation, Bessel, Laguerre-Gaussian, cell transfection

Optical tweezers is a powerful non-contact technique [1] where micrometre sized particles can be grabbed, moved and generally manipulated solely with light. Optical tweezers have forged an important bridge between physics, chemistry and biology. In recent years there has been a proliferation of activity in this area, fuelled, in part, by the recognition that we need to advance the “optical toolkit”. This essentially means creating and optical landscape and enhancing our ability to move and sort particles [2] and importantly, create 2D and 3D arrays of particles.

Using novel light sources we can perform new bioscience: femtosecond optical traps that may be used for cell detection and simultaneous trapping and two-photon excitation. Laser sources may be incorporated into optical tweezers systems for GFP fluorescence detection in cells and photoporating cells and DNA transfection. Optical traps may act as incredibly accurate force transducers that will permit accurate measurements of the motion of DNA and other biopolymers. Optical arrays in 2D and 3D may be used to separate particles in microfluidic flows by exploiting the varying affinity of particles to lattice sites in this landscape. Particles may be sorted by size, shape and refractive index. Applications exist for sorting cells and chromosomes. Additionally we may transport (guide) microscopic particles over extended distances or redistribute them between corralled regions for sorting and analysis of sub-cellular biological material using "non-diffracting" light fields [4]. Such light fields find broader interest in microscopy and targeted drug delivery to cells. Finally there is the intriguing question of ”optically bound matter”:
light scattering and refracting from objects actually holding particles together and how this might work in the biological arena.

References

[1] A. Ashkin, J.-M. Dziedzic, J. E. Bjorkholm, and S. Chu, "Observation of a single-beam gradient force optical trap for dielectric particles," Opt. Lett. 11, 288-290 (1986).

[2] M MacDonald, G. Spalding and K. Dholakia, “Microfluidic sorting in an optical lattice”, Nature 426, 421-424 (2003).

[3] K. Dholakia, P Reece, and M Gu, "Optical Micromanipulation," Chem. Soc. Rev 37, 42-55 (2008), DOI: 10.1039/b512471a.

[4] J Baumgartl et al., "Optically mediated particle clearing using Airy wavepackets" Nature Photonics 2, 675-678 (2008)

Link to program

• Session 6

Link to lectures at Biophotonics '07

• Optical Trapping and its role in biophotonics: Light takes hold
  (PDF 10.9 Mb))

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