Both the thickness and absorption coefficient of the epidermis influence the light transmission through skin. Different skin phototypes were modeled and show a more than 50% reduction in fluence rate for the darker skin phototypes at a depth of 200 μm into the skin.
Light based treatments offer major benefits to patients. Many of the light based treatments or diagnostic
techniques need to penetrate the skin to reach the site of interest. Human skin is a highly scattering medium
and the melanin in the epidermal layer of the skin is a major absorber of light in the visible and near infrared
wavelength bands. The effect of increasing absorption in the epidermis is tested on skin simulating phantoms
as well as on a computer model. Changing the absorption coefficient between 0.1 mm<sup>-1</sup> and 1.0 mm<sup>-1</sup> resulted
in a decrease of light reaching 1 mm into the sample. Transmission through a 1 mm thick sample decreased
from 48% to 13% and from 31% to 2% for the different scattering coefficients.
The accuracy of the calibration model for the single and double integrating sphere systems are compared for a white light
system. A calibration model is created from a matrix of samples with known absorption and reduced scattering
coefficients. In this instance the samples are made using different concentrations of intralipid and black ink. The total and
diffuse transmittance and reflectance is measured on both setups and the accuracy of each model compared by evaluating
the prediction errors of the calibration model for the different systems. Current results indicate that the single integrating
sphere setup is more accurate than the double system method. This is based on the low prediction errors of the model for
the single sphere system for a He-Ne laser as well as a white light source. The model still needs to be refined for more
absorption factors. Tests on the prediction accuracies were then determined by extracting the optical properties of solid
resin based phantoms for each system. When these properties of the phantoms were used as input to the modeling
software excellent agreement between measured and simulated data was found for the single sphere systems.
Photodynamic therapy (PDT) represents a novel treatment that uses a photosensitizer (PS), light source (laser) of an
appropriate wavelength and oxygen to induce cell death in cancer cells. The aim of this study was to investigate the
photodynamic effects of aluminum tetrasulfophthalocyanines (AlTSPc) and zinc (ZnTSPc) tetrasulfophthalocyanines
activated with a 672nm wavelength laser on melanoma cancer, dermal fibroblast and epidermal keratinocyte cells. Each
cell line was photosensitized with either AlTSPc or ZnTSPc for 2 h before using a diode laser with a wavelength of
672nm to deliver a light dose of 4.5 J/cm<sup>2</sup> to the cells. The cell viability of melanoma cells were decreased to
approximately 50% with concentrations of 40 μg/ml for AlTSPc and 50 μg/ml for ZnTSPc. These PS concentrations
caused a slight decrease in the cell viability of fibroblast and keratinocyte cells. Both photosensitizers in the presence of
high concentrations (60 μg/ml-100 μg/ml) showed cytotoxicity effects on melanoma cells in its inactive state. This was
not observed in fibroblast and keratinocyte cells. Cell death in PDT treated melanoma cells was induced by apoptosis.
Therefore, AlTSPc and ZnTSPc exhibit the potential to be used as a PS in PDT for the treatment of melanoma cancer.
Poly(N-isopropylacrylamide) i.e. PNIPAAm is a temperature sensitive smart material which displays a lower critical solution temperature (LCST) at 33-35°C. At the lower critical solution temperature, the gel changes from hydrophilic to hydrophobic which has significant consequences in cell culturing. The first known measurements of the optical properties i.e. absorption
(μ<sub>a</sub>) and reduced scattering (μ'<sub>s</sub>) coefficients, as a function of temperature, of a series of crosslinked PNIPAAm gels, using an Integrating Sphere setup, is presented at a wavelength of 632.8 nm. These properties showed a direct correlation between the scattering coefficient and the crosslinker density for the gels. The absorption properties correlated well with the known absorption characteristics of these gels.
Computer modeling can be a valuable tool to determine the absorption of laser light in different skin layers. For this
study, the optical properties of three different skin tumors were used in the model to evaluate the effect on penetration
depth into the skin. Comparison between the healthy dermis and the skin tumors indicated that up to 28 % more laser
light is absorbed in the healthy dermis than in the tumor tissue. This has implications on the laser dose applied to the skin
A variety of strategies have been utilised for prevention and treatment of chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores<sup>1</sup>. Low Level Laser Therapy (LLLT) has been reported to be an invaluable tool in the enhancement of wound healing through stimulating cell proliferation, accelerating collagen synthesis and increasing ATP synthesis in mitochondria to name but a few<sup>2</sup>. This study focused on an in-vitro analysis of the cellular responses induced by treatment with three different laser beam profiles namely, the Gaussian (G), Super Gaussian (SG) and
Truncated Gaussian (TG), on normal wounded irradiated (WI) and wounded non-irradiated (WNI) human skin fibroblast cells (WS1), to test their influence in wound healing at 632.8 nm using a helium neon (HeNe) laser. For each beam profile, measurements were made using average energy densities over the sample ranging from 0.2 to 1 J, with
single exposures on normal wounded cells. The cells were subjected to different post irradiation incubation periods, ranging from 0 to 24 hours to evaluate the duration (time) dependent effects resulting from laser irradiation. The promoted cellular alterations were measured by increase in cell viability, cell proliferation and cytotoxicity. The results obtained showed that treatment with the G compared to the SG and TG beams resulted in a marked increase in cell
viability and proliferation. The data also showed that when cells undergo laser irradiation some cellular processes are driven by the peak energy density rather than the energy of the laser beam. We show that there exist threshold values for damage, and suggest optimal operating regimes for laser based wound healing.