Gene gun assisted micro-particle delivery system is an excellent method for the delivery of DNA into target tissue so as to carry out gene transfection in the target cells. The gene gun is primarily a particle accelerator which accelerates DNA-coated micro-particles to sufficient velocities to breach the target layer enabling the micro-particles to penetrate to a desired depth and target the cells of interest to achieve gene transfer. However, an inevitable problem in this process is the tissue/cell damage due to the impaction of the pressurized gas and micro-particles on the target. The purpose of this research is developing a new conceptual system which improves the penetration depth of micro-particles at less imposed pressure and particle injection velocity. This is achieved by applying a microneedle array and ground slide in the gene gun system, thus a study involving microneedle assisted micro-particle delivery is conducted in this work. Microneedle array is used to create holes in the target which allows a number of micro-particles to penetrate through the skin which enhances the penetration depth inside target. The ground slide is used to load a pellet of the micro-particles and prevent the pressurized gas to avoid the impaction on the target. The operation principle is that the pellet is attached to ground slide which is accelerated to a sufficient velocity by the pressurized gas. The pellet is released from the ground slide which separates into individual micro-particles by a mesh and penetrates to a desired depth inside the target. An experimental rig to study various aspects of microneedle assisted micro-particle delivery is designed in this PhD research. The passage percentage of the micro-particles and size of the separated micro-particles are analysed in relation to the operating pressure, mesh pore size and Polyvinylpyrrolidone (PVP) concentration to verify the applicability of this system for the micro-particle delivery. The results have shown that the passage percentage increases from an increase in the mesh pore size and operating pressure and a decrease in PVP concentration. A mesh pore size of 178 μm and pellet PVP concentration of 40 mg/ml were used for the bulk of the experiments in this study as these seem to provide higher passage percentage and the narrow size distribution of the separated micro-particles. In addition, the velocity of the ground slide is detected by the photoelectric sensor and shown that it increases from an increase in operating pressure and reaches 148 m/s at 6 bar pressure, A further analysis in the penetration depths of the micro-particles to determine whether they achieve enhanced penetration depths inside the target after using microneedles is carried out. A skin mimicked agarose gel is obtained from comparing the viscoelastic properties of various concentration of agarose gel in comparison with the porcine skin, which is assumed to mimic the human skin. These experiments are used to relate the micro-particle penetration depth with the operating pressure, microneedle length and particle size. In addition, a theoretical model is developed based on the experimental data to simulate the microneedle assisted micro-particle delivery which provide further understanding of the microneedle assisted micro-particle delivery. The developed model was used to analyse the penetration depth of micro-particles in relation to the operation pressure, target properties, microneedle length and particle size and density. The modelling results were compared with the experimental results to verify the feasibility of the microneedle assisted micro-particle delivery for micro-particles delivery. As expected, both experimental and theoretical results show that the micro-particles achieve an enhanced penetration depth inside target. The maximum penetration depth of micro-particles is increased from an increase in operating pressure, microneedle length, particle size and density.

The project introduces an application using computer vision for Hand gesture recognition. A camera records a live video stream, from which a snapshot is taken with the help of interface. The system is trained for each type of count hand gestures (one, two, three, four, and five) at least once. After that a test gesture is given to it and the system tries to recognize it.A research was carried out on a number of algorithms that could best differentiate a hand gesture. It was found that the diagonal sum algorithm gave the highest accuracy rate. In the preprocessing phase, a self-developed algorithm removes the background of each training gesture. After that the image is converted into a binary image and the sums of all diagonal elements of the picture are taken. This sum helps us in differentiating and classifying different hand gestures.Previous systems have used data gloves or markers for input in the system. I have no such constraints for using the system. The user can give hand gestures in view of the camera naturally. A completely robust hand gesture recognition system is still under heavy research and development; the implemented system serves as an extendible foundation for future work.

The use of lasers for diagnosis and treatment in medical and cosmetic applications is increasing worldwide. Not all of these modalities are superficial and many require laser light to penetrate some distance into the tissue or skin to reach the treatment site. Human skin is highly scattering for light in the visible and near infrared wavelength regions, with a consequent reduction of the fluence rate. Melanin, which occurs in the epidermis of the skin, acts as an absorber in these wavelength regions and further reduces the fluence rate of light that penetrates through the epidermis to a treatment site. In vivo fluence rate measurements are not viable, but validated and calibrated computer models may play a role in predicting the fluence rate reaching the treatment site. A layered planar computer model to predict laser fluence rate at some depth into skin was developed in a commercial raytracing environment (ASAP). The model describes the properties of various skin layers and accounts for both the absorption and scattering taking place in the skin. The model was validated with optical measurements on skin-simulating phantoms in both reflectance and transmission configurations. It was shown that a planar epidermal/dermal interface is adequate for simulation purposes. In the near infrared wavelength region (676 nm), melanin (consisting of eumelanin and pheomelanin) is the major absorber of light in the epidermis. The epidermal absorption coefficient is one of the required input parameters for the computer model. The range of absorption coefficients expected for typical South African skin phototypes (ranging from photo-sensitive light skin, phototype I on the Fitzpatrick scale, to the photo-insensitive darker skin phototype V) was not available. Non-invasive diffuse reflectance spectroscopy measurements were done on 30 volunteers to establish the expected range of absorption coefficients. In the analysis it became apparent that the contributions of the eumelanin and pheomelanin must be accounted for separately, specifically for the Asian volunteers. This is a new concept that was introduced in the diffuse reflectance probe analysis. These absorption coefficient measurements were the first to be done on the expected range of skin phototypes for the South African population. Other authors dealing with diffuse reflectance probe analysis only account for the dominant eumelanin. Both the epidermal absorption coefficient and thickness are important in the prediction of the fluence rate loss. The computer model was used to evaluate the effect of the epidermal absorption coefficient (a parameter dictated by an individual’s skin phototype) and the epidermal thickness on the fluence rate loss through the skin. The epidermal absorption is strongly wavelength dependent with the higher absorption at the shorter wavelengths. In the computer model a longer wavelength of 676 nm (typical for a photodynamic treatment (PDT) of cancer) was used. For the darker skin phototypes (V) only about 30% of the initial laser fluence rate reached a depth of 200 ìm into the skin (just into the dermis). For the PDT application, results from the computer model indicated that treatment times need to be increased by as much as 50% for very dark skin phototypes when compared to that of very light phototypes. / Thesis (PhD)--University of Pretoria, 2012. / Physics / unrestricted