Stimulatory effects of zinc oxide nanoparticles on visual sensitivity and electroretinography b-waves in the bullfrog eye.

During the last decade, a large number of studies have focused on the development of nanomaterials for medical applications. Therefore, the present study was designed to evaluate the stimulatory effects of zinc oxide nanoparticles in the vertebrate visual system. Zinc oxide nanoparticles were synthesized and characterized through photoluminescence, ultraviolet (UV)-visible spectroscopy, field emission scanning electron microscopy and X-ray diffraction measurements. Furthermore, various electrophysiological recordings were obtained from the bullfrog eyecup preparations under various treatment conditions. Photoluminescence data showed a central peak at 386 nm while the UV-visible spectrum showed a sharp absorption band centered around 367 nm. Field emission scanning electron microscopy and X-ray diffraction measurements showed that synthesized zinc oxide nanoparticles have a polycrystalline wurtzite structure, with a round to oval shape and an average particle size of > 40 nm. Electroretinography (ERG) demonstrated that zinc oxide nanoparticles significantly increased the ERG b-wave amplitude in dark-adapted bullfrog eyecups and in the presence of background illumination. Zinc oxide nanoparticles also improved the visual sensitivity by 0.7 log unit of light intensity and shortened the duration of rhodopsin regeneration. Based on the results obtained, it was concluded that zinc oxide nanoparticles may be used to improve visual functions. The present study may add new dimensions to the biomedical applications of nanomaterials in eye research.