Comparative bactericidal activities of lasers operating at seven different wavelengths

Watson, I. A. , Ward, G. D., Wang, R. K., Sharp, J. H. , Budgett, D. M., Stewart-Tull, D. E., Wardlaw, A. and Chatwin, C. R. (1996) Comparative bactericidal activities of lasers operating at seven different wavelengths. Journal of Biomedical Optics, 1(4), pp. 466-472. (doi: 10.1117/12.250684)

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Seven laser instruments, delivering radiation at a selection of wavelengths in the range of 0.355 to 118 μm, were investigated for their ability to kill <i>Escherichia coli</i> as a lawn of the bacteria on nutrient agar culture plates. Easily the most effective was a 600-W CO<sub>2</sub> laser operating at 10.6 μm, which produced 1.2- cm<sup>2</sup> circular zones of sterilization at energy densities of around 8 J cm<sup>-2</sup> in a 30-msec exposure. Circular zones with an area of 0.7 cm<sup>2</sup> were achieved with 200 W from a Nd:YAG laser delivering 8-ms, 10-J pulses of 1.06 μm radiation at 20 Hz. The exposure time, however, was 16 s and the energy density (1940 J cm<sup>-2</sup>) was more than 240 times higher than with the CO<sub>2</sub> laser. This difference is believed to be partly due to the much higher absorption of radiation at 10.6 μm than at 1.06 μm, by water in the bacterial cells and the surrounding medium (nutrient agar). Sterilization was observed after exposure to frequency-tripled Nd:YAG laser radiation at 355 nm (3.5 J cm<sup>-2</sup>). Lasers that were totally ineffective in killing Escherichia coli (with their wavelength and maximum energy densities tested) were the far infrared laser (118 μm; 7.96 J cm<sup>-2</sup>), the laser diode array (0.81 μm; 13,750 J cm<sup>-2</sup>), and the argon ion laser (0.488 μm; 2210 J cm<sup>-2</sup>). The speed at which laser sterilization can be achieved is particularly attractive to the medical and food industries. Glenn D. Ward,‡ Ruikang K. Wang,† James H. Sharp,† David M. Budgett,† Duncan E. Stewart-Tull,‡ Alastair C. Wardlaw,‡ and Chris R. Chatwin

Item Type:Articles
Glasgow Author(s) Enlighten ID:Watson, Dr Ian and Chatwin, Prof Christopher and Wardlaw, Prof Alastair and Stewart-Tull, Prof Duncan and Sharp, Dr James
Authors: Watson, I. A., Ward, G. D., Wang, R. K., Sharp, J. H., Budgett, D. M., Stewart-Tull, D. E., Wardlaw, A., and Chatwin, C. R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Journal of Biomedical Optics
Publisher:Society of Photo-optical Instrumentation Engineers
ISSN (Online):1560-2281

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