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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.
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