Light can be used to manipulate of microscopic biological particles such as cells or DNA. Optical trapping (also known as optical tweezing) is the use of laser beams to trap and move tiny particles. Lasers can also be used as scissors to punch a hole in a cell membrane, allowing drugs or foreign genetic material to enter. This is known as photoporation.
Optical trapping
Optical trapping involves the confinement of a small particle, such as a cell, to the spot of a focused laser beam. The particle can be 'picked up' and moved around by moving the focal spot of the laser beam, which explains why the laser beams are also known as optical tweezers. The wavelength of the light is chosen so that light is not absorbed by the particle, preventing damage. Typically, infrared light is used.
Click on the links below to find out more
How optical trapping works
Microgolf and other fun videos!
Optical Trapping group at University of St Andrews
Photoporation
Lasers can be used as optical scisssors to punch tiny holes in single cells, allowing drugs for foreign DNA to enter. When lasers are used to cut biological material, the laser wavelength is chosen so that light will be absorbed by the sample. Typically, ultraviolet light is used. The laser light is actually delivered in short pulses (typically nanoseconds, or even femtoseconds in duration) and can be used to cut a micron sized hole in a cell. This hole rapidly re-seals, avoiding permanent damage to the cell membrane.
A technique being used for photoporation is through the use of a Bessel beam - read on to find out more!
Further information about photoporation
Optically-guided neuron growth
Focused laser beams have been shown to influence the growth of developing neuronal (brain-like) cells. A developing neuron produces a structure called an axon which grows out of the cell like an extending cable and eventually finds a target and forms a connection (e.g. connecting your toes to your spinal cord). Ordinarily these axons are guided to their targets by chemical signals present in the organism. However a focused laser has been demonstrated to also guide these structures as they grow. This represents a possibility for a high degree of manipulation in creating artificial neuronal structures or repairing damaged ones.
Further information about optically-guided neuron growth
Raman spectroscopy
Raman spectroscopy is a spectroscopic technique used that relies on analysis of light that is scattered by a sample, with the energy of the light being shifted to a higher or lower energy than that of the incident light. The energy shift results from a change in vibrational, rotational or electronic energy of a molecule.
How Raman spectroscopy works
Raman spectroscopy can be used to study biological systems. Research in this field at the University of St Andrews is focussed on the field of cancer diagnostics. cancer research particularly the early diagnosis of neoplasia.
Further information about Raman spectroscopy