Conference Publications

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Browsing Conference Publications by Author "Abrahamse, H"

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    Design and fabrication of a micro fluidic circuit for the separation of micron sized particles
    (South African Institute of Physics (SAIP), 2009-07) Khumalo, F; Jordaan, J; Abrahamse, H; Land, K; Potgieter, S; Sparrow, R
    The development of a micro fluidic circuit for the separation of micro particles is being investigated. There are a wide range of available separation techniques such as acoustic, laminar flow, split flow, optical trapping and centrifugal forces. The physical phenomena occurring at the micron level influences the design of the circuit as well as the behaviour of the particles within the circuit. Research is being directed towards the use of physical forces such as laminar flow and away from using external forces to drive flow and perform separation, this simplifies the circuit design. These phenomena can be manipulated in circuit design to suit specific applications. The present study focuses on the design considerations for circuits used in separation applications and the manufacturing of suitable standard particles, using dendrisphere technology. The particles used in this study are polyethyleneimine crosslinked with glutaraldehyde using an emulsion based technique. The versatility of these particles includes the ability to customise and functionalise them to suit a specific study. The modification of the technique for generating a variety of particle sizes is being investigated. The particles are stained to improve visualisation and assess qualitative discrimination of the different sized particles. The optical signature of the particles can be used advantageously in quantifying separation rather then particle counting. The particles will be used as standards to precisely evaluate the sorting ability of the micro fluidic circuits. This will give quantitative results of the circuit performance as well as establish the limitations of the system.
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    Influence of beam shape on in-vitro cellular transformations in human skin fibroblasts
    (The International Society for Optical Engineering, 2005) Mthunzi-Kufa, Patience; Forbes, A; Hawkins, D; Abrahamse, H; Karsten, AE
    A variety of strategies have been utilised for prevention and treatment of chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores1. 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 few2. 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. The authors show that there exist threshold values for damage, and suggest optimal operating regimes for laser based wound healing.
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    Influence of laser beam shape on in-vitro cellular and molecular transformations in human skin fibroblasts
    (2006-07) Mthunzi-Kufa, Patience; Forbes, A; Hawkins, D; Abrahamse, H; Karsten, AE
    A variety of strategies have been utilised for prevention and treatment of chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores. 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. This study focused on an in-vitro analysis of the cellular responses induced by treatment with three different laser beam profiles. The promoted cellular alterations were measured by increase in cell viability, cell proliferation and cytotoxicity. The results obtained 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