Detection of Interleukin 6 in a Sprague Dawley Rat’s Blood Plasma Using a Fiber Optic Biosensor with Long-Period Grating ^†

Abstract

The severity of various diseases is related to the concentration of interleukin 6 (IL-6), a proinflammatory cytokine crucial for the proliferation and differentiation of immunocompetent and hematopoietic cells. In ischemic cerebrovascular disease, it is known that, after traumatic injury, increased plasma levels of IL-6 are associated with neuronal inflammation and brain death. Research has shown that elevated plasma IL-6 levels within the first 12 h after an ischemic vascular event are strong predictors of early mortality. Therefore, developing a device that can detect the presence of IL-6 in a murine model of induced ischemic disease could be beneficial for monitoring the disease and selecting the appropriate treatment in the future. This study aimed to detect IL-6 using biosensors developed within optical fibers; the biosensors were assembled using a self-assembled monolayer technique. Subsequently, detection was carried out using samples from rats (Sprague Dawley strain) with an induced ischemic disease. Samples were left to interact with the sample for 2 h to characterize the changes in the sensor’s transmission response. Both the response of the biosensor to IL-6 and the self-assembly steps were characterized by transmission spectroscopy at wavelengths of 1250–1450 nm and micro-MIR spectroscopy. Spectral changes were observed at different stages of the assembly and detection processes. By performing a PCA on the experimental data, it was possible to observe the clustering of the different assembly stages and the final detection. This allowed for discrimination not only at the stage of the biosensor’s construction but also in its detection of IL-6.