Cell viability after exposure to optical tweezers using high power red laser diodes or near infrared lasers

Ln comparison with optical tweezers using near infrared lasers, red emitting high power laser diodes (lambda = 670-680 nm) may offer several advantages, such as easier adjustment, smaller beam diameter in the focal plane and low absorption of optical radiation. One-photon absorption by water or two-photon absorption by various cellular components may induce cell killing by heat or by photochemical reactions. To test cell viability, cultivated CHO cells were exposed to various light doses of this wavelength as well as to a moderate light dose of a conventional Nd:YAG laser. Loss of clonogenicity of about 50 % as well as a reduction of cell growth were measured at 680 nm when using a maximum light dose of 2.4 GJ/cm(2). In contrast, no cell damage was found at 670 nm as well as at 1064 nm when using a light dose of 340 MJ/cm(2), which revealed to be sufficient for several applications.