Ultrasensitive Diamond Microelectrode Application in the Detection of Ca2+ Transport by AnnexinA5-Containing Nanostructured Liposomes

Author(s)

Pasquarelli, Alberto ; Silva Andrilli, Luiz Henrique ; Bolean, Mayte ; Ferreira, Claudio Reis ; Eufrasio Cruz, Marcos Antonio ; de Oliveira, Flavia Amadeu ; Ramos, Ana Paula ; Millan, Jose Luis ; Bottini, Massimo ; Ciancaglini, Pietro

• Document type: Journal article
• Source: BIOSENSORS-BASEL; v. 12, n. 7, p. 15-pg., 2022-07-01.

Abstract

This report describes the innovative application of high sensitivity Boron-doped nanocrystalline diamond microelectrodes for tracking small changes in Ca2+ concentration due to binding to Annexin-A5 inserted into the lipid bilayer of liposomes (proteoliposomes), which could not be assessed using common Ca2+ selective electrodes. Dispensing proteoliposomes to an electrolyte containing 1 mM Ca2+ resulted in a potential jump that decreased with time, reaching the baseline level after similar to 300 s, suggesting that Ca2+ ions were incorporated into the vesicle compartment and were no longer detected by the microelectrode. This behavior was not observed when liposomes (vesicles without AnxA5) were dispensed in the presence of Ca2+. The ion transport appears Ca2+-selective, since dispensing proteoliposomes in the presence of Mg2+ did not result in potential drop. The experimental conditions were adjusted to ensure an excess of Ca2+, thus confirming that the potential reduction was not only due to the binding of Ca2+ to AnxA5 but to the transfer of ions to the lumen of the proteoliposomes. Ca2+ uptake stopped immediately after the addition of EDTA. Therefore, our data provide evidence of selective Ca2+ transport into the proteoliposomes and support the possible function of AnxA5 as a hydrophilic pore once incorporated into lipid membrane, mediating the mineralization initiation process occurring in matrix vesicles. (AU)

• FAPESP's process: 21/13140-1 - Study of PHOSPHO1 and nSMase2 interaction with model membranes: a possible correlation in matrix vesicle secretion
• Grantee: Luiz Henrique da Silva Andrilli
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/08568-2 - Investigation of the extracellular vesicles (VEs) role in the initiation, propagation, regeneration, and modeling of biological mineralization
• Grantee: Pietro Ciancaglini
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/25475-2 - Effect of pH and calcium ions on the optimization of the incorporation of annexin A5 into liposomes
• Grantee: Luiz Henrique da Silva Andrilli
• Support Opportunities: Scholarships in Brazil - Scientific Initiation