Utilization of thermal imaging for monitoring in vitro processes

Thermography use has been increased dramatically with the commercial, industrial and medicine applications over the past fifty years. As completely non-invasive technique it has been useful tool in the medical research as sensitive diagnostic method for a multitude of clinical and experimental situations. Based on thermal imaging of a human skin, it is possible to monitor nervous system, metabolic or vascular disorders, breast cancer, arthritis, pain syndromes, soft tissue injuries and virus infections among others. Infection and inflammation can emerge in the any part of the human body. The five main symptoms of acute inflammation are redness (rubor), swelling (turgor), heat (calor), pain (dolor) and loss of function (functio laesa). Increase in the body temperature during inflammation may happen locally as well as systemically (fever). Monocytes and macrophages are cells central to inflammation, as they produce many components which participate in the immune defence mechanisms and cause temperature rise in vivo. Analysis of these processes can be done with isolated primary cells or with model cell lines in vitro. The aim of this study was to explore whether it is possible to monitor inflammatory process under in vitro conditions by thermography imaging. Cell cultures were stimulated in 48 wells polystyrene microtiter plate with two different stimulants that induce metabolic processes similar to those during inflammation in vivo: a) phorbol 12-myristate 13-acetate (PMA, a polyfunctional diterpene phorbol ester used as unspecific activator of protein kinase C), b) bacterial lipopolysaccharide (LPS, the major structural component of the outer wall of Gram-negative bacteria used as specific potent stimulator of an inflammatory process via TLR4 pathway). Cells were incubated in media only or media containing stimulants for various period of time (24h, 1h, 15min) before onset of imaging. Imaging was provided in real time inside the CO 2 incubator by infrared camera Thermo Tracer TH7102WL. This camera system contains an uncooled focal plane array detector with geometric resolution of 76,800 pixels per picture. Spectral range is from 8 μm to 14 μm with the temperature range-40°C to 120°C. The minimum detectable temperature resolution (difference) is 0.07°C at 30°C (Normal mode) and spatial resolution is 0.48 mm at measuring distance of 30 cm (IFOV1.58mrad). We conclude that thermography has potential for monitoring in vitro processes in cell culture system but main obstacles from our experience should be discussed.