A novel ex-vivo model for fluorescence guided surgery: Simulating glioma conditions

Reliable in vitro models are used for optoelectronic device development, such as fluorescence detection devices for fluorescence-guided surgery of gliomas. A common approach involves inducing gliomas in animal models, followed by a dosage of 5-ALA which metabolises to Protoporphyrin IX (PpIX) in the glioma, resulting in fluorescence. Although these approaches excel in capturing key biomolecular and physiological features of the tumour, they are inherently indeterministic. This limits the scope of their use for preclinical device development, where consistent and controllable tumour reproduction across multiple animals, over time, is needed. Alternative approaches using fluorescence markers in gelatine provide a simple replication but may fail to capture the complexities of in vivo models. In this study, we introduce an exogenous brain tumour model for assessing PpIX fluorescence detection. The model was developed by injecting a PpIX solution into the cortical region of a resected adult rat brain, where the injection site simulated a tumoral region with elevated PpIX concentration. The created tumoral region had a gradient of concentrations, with a peak at the centre and a decrease towards the tumour margins, akin to glioma in in vivo conditions. The fluorescence profile was compared to in vivo conditions using 5-ALA and correlated well with other reported works, achieving a correlation of R 2 > 0.93. The model’s validity was tested by examining the effect of the solvent, Dimethyl Sulfoxide, on the Autofluorescence (AF) of the brain sample. Additionally, the short-term effect of storage (over 20 h) on AF was analysed. Examinations confirmed that the solvent did not alter AF. The brain sample should be stored in Hank’s Balanced Salt Solution (or an equivalent) and refrigerated to maintain moisture and preserve AF. The model accurately replicated surgical fluorescence conditions and offers a suitable alternative to glioma induction, benefiting the development of fluorescence detection devices across design iterations.