The development of a multimodal imaging agent for the management of diabetes mellitus type 2

Diabetes Mellitus is a metabolic disorder with multiple aetiologies with an estimated 422 million people with the condition, which is characterised by the chronic presence of hyperglycaemia and dysfunction in carbohydrate, protein, and fat metabolism. Diabetes Mellitus is separated into two main types; Diabetes Mellitus Type 1 and Diabetes Mellitus Type 2. In Diabetes Mellitus Type 2, individuals often exhibit insulin resistance with the exact pathophysiology being unknown. However, what is known is that the β-cells (the insulin-producing cells of the pancreas) can change in mass and different observations have been reported as to how this affects the progression of the disease. Since there are several different observations, there is a need to produce an imaging agent which can help give visual evidence as to the changes in the β-cell mass within the pancreas. The aim of this project was to develop an multimodal imaging probe that could be used to image the β-cell mass and it’s changes in the pancreas through MRI imaging and fluorescence microscopy.A multimodal imaging probe was developed which has been synthesised by functionalising fluorescent quantum dots with Exendin-4 (for specific binding to GLP1-R) and Gd-DOTA-TA (for MRI imaging). The spectra of the probe showed an excitation wavelength of 400nm and an emission wavelength of 607nm. With the probe being determined to be 533.6nm in size and with a charge of -20.1mV, there was evidence of good conversion from the TGA ligands to the Exendin-4 and Gd-DOTA-TA. Despite this, the relaxivity of the QD-Exendin-Gd-DOTA-TA conjugate could not be determined due to the low concentration obtained. The confocal studies show that the imaging agent was internalised into the cell, with some indication of specific binding to the GLP1-R on the MIN6 cells. However, cell viability studies show error between readings, so it is unclear of the actual effects of the agent on the cell.To conclude, the result of this study demonstrated the successful synthesis and functionalisation of the multimodal imaging probe with some future studies needed to optimise the functionalisation process. Furthermore, it was demonstrated that this probe can successfully enter MIN6 cells within 1 hour, and indicates specific binding to GLP1-R. This shows initial potential that this probe can specifically bind to cells expressing GLP1-R and can be used to visualise the mass present in the pancreas.With this, in future studies, confocal studies can be conducted to focus on alternative cell lines that express this receptor, and the localisation of the probe within the cell. The synthesis of the imaging probe can be repeated and optimised to prevent aggregation. If this is done, a more accurate idea of the cytotoxicity can be done. This information can further indicate the probes potential in visualising the β-cell mass overtime to investigate it’s changes