Abstract

We have investigated the effect of application of gold nanoparticles with a diameter of 50 nm and nanoshells with a 150 nm silica core size and 25 nm thick gold shell on optical properties of skin. We have analyzed the possibility of using these particles as a contrasting agent for optical coherence tomography (OCT). As the first step in the study, effects of gold nanoparticles after one application to skin were studied using OCT. Then we evaluated the effects of multiple applications of 50 nm gold nanoparticles to skin in 30-minute intervals. Biopsy of relevant skin areas was performed under local anaesthesia and samples for light and electron microscopy were prepared. Identification of skin layers on OCT images was made by comparing with histology. Application of gold-silica nanoshells caused increase in intensity of useful signal, brightness of the superficial part of the dermis and contrast between the superficial and deep parts of the dermis 30 minutes after application on skin. After 24 hours the changes in OCT images became more pronounced as the brightness of the superficial part of the dermis and the contrast between the superficial and deep parts of the dermis further increased. In addition, the border between the superficial and deep parts of the dermis became more distinct, continuous and well discernible, permitting to accurately differentiate these layers. Besides that, the application of nanoshells caused contrasting of hair follicles and glands. In order to give interpretation to the obtained experimental OCT-images of skin and understand the mechanisms of contrasting a set of Monte Carlo calculations was performed in order to simulate the images of skin before and after application of the nanoparticles for skin model close to that in the experiment. The results of the simulation exhibit good qualitative agreement with the experimental images and prove that the contrasting originates from the nanoparticles added while contrasting of hair bulb originates from the absence of nanoparticles in it with their presence in surrounding area.

© 2007 SPIE