Electrochemical measurements with multielectrode array systems to determine the release of serotonin by exocytosis in human platelets.

Introduction.

Serotonin is a neurotransmitter that participates in the homeostasis of many physiological functions in humans. The study and understanding of its cellular biology are of special relevance in advancing knowledge of the different actions and biosignal processes of this biological amine. It accumulates in intracellular vesicles and is released by exocytosis. Over 90% of blood serotonin is accumulated in platelets, where the highest content is stored in the so-called delta granules.

We are carrying out a quantitative study of the release, by exocytosis, of serotonin in platelets using amperometry with multi-electrode array (MEA) systems. Each exocytotic event is recorded as an amperometric deflection called a “spike”.

Methods.

We fabricate and optimize novel boron-doped nanocrystalline diamond 16-microelectrode array devices (16-BBD-MEA): opaque devices on silicon substrates (BDD-on-silicon MEA)¹ and transparent devices on quartz substrates (BDD-on-quartz MEA)².

With these 16-BBD-MEA systems, we record the amperometric spikes. The measurements are carried out under two different conditions: basal (without the modification of isolated platelets) and after loading the platelets with10 µM serotonin for 2 h.^1,2

Results.

MEA systems are a solid tool for studying exocytosis in human platelets. This is important as platelets are one of few easily accessible human cells. From each spike, we calculate four kinetic parameters: Imax (maximum oxidation current, in pA), t_1/2 (spike width at half maximum, in ms), Q (spike net charge, in pQ) and the ascending slope of the spike (in pA/ms). These parameters permit us to characterize and classify the secretory spikes.^1,2

Conclusions.

It is possible to quantitatively determine the release of serotonin by exocytosis from human platelets using BDD-MEA devices.

References.

¹ González Brito, R; Montenegro, P; Méndez, A; Carabelli, V; Tomagra, G; Shabgahi, R.E.; Pasquarelli, A.; Borges, R. Biosensors2023, 13, 86.

² González Brito, R; Montenegro, P; Méndez, A; Shabgahi, R.E.; Pasquarelli, A.; Borges, R. Biosensors2024, 14, 75.