Laroussi has been conducting research on the biomedical applications of cold atmospheric plasma since 1994. His early experiments were mostly on the inactivation of bacteria for decontamination, disinfection, and wound healing applications. These early seminal experiments are recognized today as the initial groundbreaking work that led to the establishment of modern plasma medicine.
Three main research themes have been pursued at Laroussi’s lab: 1. Development of low temperature plasma sources; 2. Diagnostics and characterization of plasma; and 3. the biomedical applications of cold plasmas. Each general theme is comprised of several research topics. The following is a detailed list of these research topics:
- Generation of large volume atmospheric pressure cold plasmas
- Generation of cold plasma jets and microjets (and assemblies of these)
- Electrical and optical diagnostics of plasmas
- Effects of cold plasmas on prokaryotic cells (bacteria)
- Effects of cold plasmas on healthy Eukaryotic cells (mammalian cells)
- Effects of cold plasmas on cancer cells
- Selectivity studies
- Plasma-liquid/biological fluid interactions
Low temperature plasma sources for biology and medicine
Preliminary research is showing promising possibilities to use low temperature plasmas in medical applications such as wound healing, killing of cancer cells, tissue engineering, and the sterilization of reusable heat-sensitive medical instruments. These fascinating developments are posing many technological challenges and are bringing to the forefront fundamental questions regarding the mechanisms of interaction between living organisms and plasma. At the same time, as low temperature non-equilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed and characterized. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, etc. These sources are today used in various biomedical investigations including in dental applications, wound healing and cancer treatment. Two main devices have been used: The Dielectric Barrier Discharge and Plasma Jets. Our plasma jet, the “plasma pencil” was the first low temperature jet developed specifically for biomedical applications.
Inactivation of bacteria by low temperature plasma
Many medical tools and instruments are made of heat sensitive materials rendering them unsuitable to be sterilized by heat based methods such as autoclaves. Cold plasma is an ideal medium to use to decontaminate/sterilize contaminated surfaces of instruments used in the medical or dental theaters. In addition, to date, bacteria showed no acquired resistance to plasma treatment. This makes plasma a potential technology to use to fight bacteria that acquire resistance to antibiotics such as MRSA.
Effects of low temperature plasma on healthy cells
Low temperature plasmas produce chemical species including reactive oxygen species (ROS) and reactive nitrogen species (RNS) which exhibit strong oxidative properties and/or trigger signaling pathways in biological cells. For example oxidation of the lipids and proteins that constitute the membrane of biological cells leads to the loss of their functions. In such environment bacterial cells were found to die in minutes or even seconds, depending on the strain. However, under some conditions, low temperature plasmas appear to cause little damage to living animal and plant tissues. Having different structures and morphologies, bacterial and mammalian cells exhibit different responses to physical and chemical stresses. For example, epithelial cells are found to remain viable under plasma conditions that can be lethal to bacterial cells. In addition, low doses of cold plasma can stimulate the proliferation of healthy cells, such as fibroblasts, which is beneficial in wound healing applications.
Effects of low temperature plasma on cancer cells
Under some conditions, low temperature plasmas can induce apoptosis/ programmed cell death. The induction of apoptosis opened the possibility to use plasma technology to kill cancerous cells. Promising results have so far been achieved in vitro and in vivo which show that plasma can effectively kill prostate cancer cells, leukemia cells, squamous cells carcinoma, and others.