Amperometric Detection of Ultrasound-Induced Secretory Events in Potential Treatment of Type 2 Diabetes

OBJECTIVE:The objective of this study was to explore a potential new treatment method that utilizes a non-invasive application of ultrasound energy to induce exocytosis of insulin from pancreatic beta cells. Our amperometric measurements can not only provide confirmation of secretion, but also data that could lead to optimization in controlling the release via ultrasound application. METHODS: Our experiments focused on detecting exocytotic secretions from pancreatic beta cells in response to ultrasound stimulation using carbon fiber amperometry. Exocytosis of insulin is measured via amperometric readings of the oxidation of dopamine. Dopamine that is loaded into cells is released via vesicles along with insulin. Results were obtained with commercially available electrodes as well as electrodes fabricated in-house. A sham group was included in which cells were loaded with dopamine but not stimulated for secretion. RESULTS: To confirm the functionality of the in-house made electrodes, a triangular waveform was run through the electrode, and using an oscilloscope, the original signal was compared to the one from the electrode. Consequently, the amperometry experiments were run with both the in-house made electrodes and commercial electrodes. Similar results were obtained. Secretory amperometric readings were recorded after application of ultrasound at 800kHz and 1MHz with an intensity of 1W/ cm2. The ultrasound pulse was applied for 5s, 10s and 15s at various time intervals. There is an immediate response of secretion after application of the 800kHz pulse for 5s at three intervals (t=180s, 360s and 540s). Similar results were obtained at 1KHz. With application of consequent 5s, 10s and 15s ultrasound pulses, a prolonged response was recorded for a prolonged stimulation. These results confirm that ultrasound stimulation induces secretory events in beta cells. Ongoing experiments focus on exploring the impact of varying parameters such as ultrasound intensity and pulse length on exocytotic events. CONCLUSIONS: Our proposed technology would directly target beta cell dysfunction, one of the underlying causes of insulin deficiency in Type 2 Diabetes, and could result in the development of a new therapeutic approach for the treatment of Type 2 Diabetes