Research into the interaction between biological tissue and laser light is advancing thanks to the Council for Scientific and Industrial Research (CSIR) Biophotonics Group (BG).
The BG, which is part of the CSIR National Laser Centre, has established a biological laboratory for manufacturing tissue models based on human cell samples adjacent to an optical laboratory where laser treatments and analysis, such as determining the optical properties of the samples, can be performed.
"I do not know of other research groups which have combined facilities to study lasers and laser interaction with tissue. Other biochemistry groups are using lasers as a medium to study tissue cells, however, they do not have the facilities for the optical analysis," says BG group leader Aletta Karsten.
The BGs strength lies in the fact that it is a multidisciplinary research group, says Karsten.
Members of the group include physicists, biologists, biochemists and engineers all working together to provide the physics, biology and engineering expertise behind the study of photons and how the light particles interact with tissue.
Using computer models, the group can determine how photons are scattered, absorbed and transmitted through a layer of tissue of variable thickness.
The path of individual photons is modelled as the photons travel through the tissue and the model produces the results in a cross section of the tissue, showing the pattern according to which the overall light has been scattered and absorbed and to what depth in the skin tissue the light has penetrated.
The model consists of different layers, which represent, in the case of skin tissue, the stratum corneum, epidermis, dermis and hypodermis layers.
Multidimensional tissue models can be used to analyse the effectiveness of photodymanic therapy (PDT) on different skin types.
PDT is a possible cancer treatment modality where a photosensitiser, which accumulates mostly in cancerous tissue, is administered to a cancer patient. After a period of time the tumour is irradiated by a laser or other light source, the wavelength of which has been carefully selected to coincide with one of the light absorption peaks of the photosensitiser.
The energy of the photons is absorbed by the photosensitiser, which causes a fatal oxygen reaction within the cancerous cells.
Unlike chemotherapy, the killing of cells is achieved by the combination of the laser and drug, with possibly fewer side effects than traditional chemotherapy.
The BG is working with Rhodes University's department of science and technology and national research foundation Professor of medicinal chemistry and nanotechnology, Tebello Nyokong, to further her research into PDT drugs.
To achieve the desired effect, it is important to supply enough laser light to kill the tumour cells. For embedded tumours, this becomes more difficult owing to the absorption of light in the first layers of the skin before the tumour. The absorption of light is highly dependent on skin tone, says Karsten.
The laser settings appropriate for a fair skinned person may cause severe burns on a dark skinned person, says Karsten.
The BGs research, therefore, aims to perfect the laser procedures involved in PDT as much as possible before going to clinical trials. The three-dimensional skin models used in the BGs studies are close to actual tissue and, therefore, the interpretation of the model's interaction with lasers is close to that of real tissue.
Less Invasive Diagnostic Procedures
The BG is also studying how lasers can be introduced into medical diagnostic procedures and treatments, hoping to influence contemporary medical practices.
The BG researcher in this field, Ann Singh, says that lasers offer medical diagnostic procedures that are less invasive than current diagnostic procedures.
"People may be reluctant to undergo biopsies and endoscopic procedures because such procedures can be uncomfortable and painful. Lasers offer a method of diagnosis that is less painful and not as invasive, which is an improvement in the quality of life for a prospective patient," says Singh.
One of the tools currently available within the BG is an optical coherence tomography (OCT) system, which is a laser imaging technology that can image different structures within tissue.
OCT, coupled with other imaging techniques, has the potential to offer noninvasive biopsies and is a method of monitoring processes like wound healing over a period of time. It can also be used in tumour detection and the evaluation of a treatment.
The technology offers similar result to histology in medicine, without the need to remove tissue as in the case of a biopsy or sacrificing the subject under investigation.