Development of novel light sources to enable non-invasive imaging of cells in 3D tissue constructs and grafts.

We have developed methods for growing a patient's own skin cells in the laboratory to produce sheets of skin that can be used for skin grafting on patients with extensive burns, and for repairing chronic wounds in diabetic and elderly patients. Although the methods are successful, and are being used clinically, we have no reliable technique for assessing how well the living cells are developing into properly structured skin - all the reliable methods involve killing the cells. Optical coherence tomography (OCT) is a relatively new method of producing cross-sectional images of living tissue that are comparable to the sections of dead tissue that the histologist examines. The amount of detail that can be seen on the optical coherence tomography images is controlled by the light source. Expensive and complex lasers are needed to produce finely detailed images. We have a great deal of experience in designing and manufacturing very high performance solid state light sources. In this project, we will design and make novel light sources, build them into our existing optical coherence tomography equipment, and test them by comparing OCT images with conventional histological images of dead tissue. The end result will be an optical imaging system that can be used to follow the growth of the live cells in the laboratory, and also to check the behaviour of the cells when the graft has been applied to the patient.

The key objective of the proposed multidisciplinary project is to develop compact and cost-effective nanostructured photonic device technology to produce ultra-broadband emission in the 900-1300 nm wavelength region to enable a quantum leap in the visualization performance of OCT systems. This advance will provide an unprecedented non-invasive optical sectioning tool to visualize microscopic morphometric features at subcellular level resolution in tissue to replace conventional bright-field and confocal microscopy imaging of biopsy sections in the lab, whilst the technique may be easily adapted to provide compact and easy to use scanning systems for clinical studies. Broadband multilayered QD laser diode structures will specifically be developed for emission across the wavelength range from 900 to 1300nm. These wavelengths are compatible with those achievable using InGaAs QD technology and the program will exploit recent advances in QD lasers for telecommunications applications, which have shown that ultra low threshold, high power and relative temperature independence can be obtained to cover these wavelengths. To develop a reliable OCT approach for non-invasive monitoring of cells within 3D scaffolds we propose to use well established tissue engineered models of skin based on natural human dermis as the in vitro test-bed model for the development and validation of non-invasive methodologies for testing cell penetration into 3D scaffolds - here information on the rough population density of cells within scaffolds at different depths would be sufficient; and the nature of the cells present in the scaffold.