  This work reports on the production of Ag nanoparticles (AgNPs) in water
solution based upon two-phase pulsed laser procedure for ophthalmological
therapeutic approaches. In this case, the AgNPs should be less then 10 nm and
have a narrow size distribution. Nanoparticles of this sized-scale are capable
to penetrate the complex ocular barriers, ensuring effective non-invasive drug
delivery to retina. In the first phase, AgNPs larger than 20 nm were fabricated
via laser ablation of a Ag target under water by irradiation with a fundamental
wavelength of 1064 nm generated by a Nd:YAG laser. During the second phase, to
reduce the mean size of the as-obtained nanoparticles and properly adjust the
size distribution, the water colloids were additionally irradiated by
ultraviolet harmonics (355 nm and 266 nm) from the same laser source. The
effect of the key laser parameters - wavelength, fluence and laser exposure
time - upon the nanoparticles morphology was studied. The most suitable
post-ablation treatment of initial colloids was obtained by consecutive
irradiation with the third (355 nm) and the fourth (266 nm) harmonics of the
fundamental laser wavelength. By using this approach synergistic effect between
two mechanisms of light absorption by AgNPs was induced. As a result
contaminant-free colloids of AgNPs with a size inferior to 10 nm and a quite
narrow size distribution with a standard deviation of 1.6 nm were fabricated.
The toxic effect of the as-produced AgNPs on Gram-positive and Gram-negative
bacteria and Candida albicans was explored. The most efficient action was
reached against Pseudomonas aeruginosa and Escherichia coli. Potential
application of the synthesized AgNPs colloidal aqueous solutions with
antimicrobial action as a non-invasive method for ocular infections prevention
and treatment was proposed.
