The main goal of this project is the development of ionphore-embedded membranes with application in bio-analytical devices for electrochemical detection of biomarker electrolytes in sweat but also in other biological media such as serum or cellular cultures.
The focus is the detection of sodium, potassium and chloride ions. In order to achieve this goal, the following objectives are envisaged:
O1: Membrane synthesis and ionophores incorporation.  Bilipidic membranes, hydrogels and liposomes will be synthesized and the incorporation of ionophores investigated.
O2: Immobilization of the ionophore embedded membrane at the electrode surface.  Interaction of the membrane with solid surface may lead to conformational/structural modifications and finding the optimal condition is relevant for achieving the best sensitivity and the lowest detection limit. The sensor performance will be investigated in artificial sweat but also on a biological model designed to detect short and transient responses to the sensor.

Director Proiect: Dr. Anca Aldea (U-1800-055N-8239)
https://www.brainmap.ro/anca-aldea

Mentor Proiect: Prof. Ileana Cornelia Farcasanu (U-1700-033C-8247)
https://www.brainmap.ro/ileana-cornelia-farcasanu

In the second stage of Project PD67 the main objective was to test the devices obtained for the detection and quantification of sodium, potassium and chlorine ions, as well as to determine the characteristics of the sensors. During this phase, the activities of obtaining electrodes from polycaprolactone electrospun polymer fibers and silicon/silicon dioxide waffers metallized with gold, the synthesis of membranes, the incorporation of the ionophore into the synthesized membranes, the immobilization of the membranes with the ionophore incorporated on the surface of the electrodes, continued.
Briefly, polycaprolactone electrospun polymeric fibers were obtained which were coated with a gold layer and electrodes obtained on silicon/silicon dioxide wafers metallized with an intermediate layer of titanium and gold. 3 types of membranes were synthesized: lipid membrane, hydrogel and liposomes. Ionophore incorporation was performed both before and after membrane synthesis. In order to characterize the surfaces obtained, they were analyzed electrochemically (cyclic voltammetry), morphologically (scanning electron microscopy) and structurally (infrared spectroscopy). Sensors obtained by immobilizing membranes with incorporated ionophore on surface were tested for the detection and quantification of sodium, potassium and chlorine ions. Biocompatibility tests were also carried out by using them as a substrate for the proliferation of cell cultures.
As a result of these activities, a 100% fulfillment of objective 1 (O1: Synthesis of the membrane and incorporation of ionophores) and 75% of objective 2 (O2: Immobilization of the membrane with ionophore embedded on the electrode surface) was achieved. Bilipid membranes, hydrogels and liposomes were synthesized and the ionophore incorporation method was optimized, gold surfaces modified with different membranes and ionophores were obtained and characterized, the membrane immobilization method on the electrode surface was optimized and the sensors were tested in order to establish their response to specific  ions of the incorporated ionophores.

Based on the studies, tests and characterizations performed, the project goal of building a sensor based on an ionophore incorporated into a membrane for the detection of ions in fluids was achieved.

It was demonstrated that both planar substrates (SiO2/Si) and flexible substrates such as polymer fibers obtained from polycaprolactone can be used as substrates, although the detection limits were lower for planar substrates, the difference was not so significant, the values ​​being of the same order of magnitude.

The optimal membrane for the construction of this sensor proved to be the membrane obtained from the immobilization of liposomes on the electrode surface. This was obtained starting from the lipid precursors 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-oleoyl-2-stearoyl-sn-glycero-3-phosphocholine (OSPC). The optimal ratio for the incorporation of ionophores between the two lipids was 1:1 and also, the acquisition of lipids dissolved in chloroform (not powder), led to a better efficiency of the synthesis but also to vesicle solutions whose polydispersity index was low, obtaining liposome vesicles with incorporated ionophore with diameters ranging predominantly between 100 and 200 nm.

The most efficient ionophores of those tested for the detection of sodium, potassium and chlorine ions proved to be sodium ionophore X, potassium ionophore I and chlorine ionophore II.

Through cytotoxicity (MTS) and biocompatibility (fluorescence) studies, it was demonstrated that the developed sensor allows the seeding and proliferation of cells on the surfaces modified with membranes with incorporated ionophore. For the use of these sensors in vivo, additional tests will be necessary before their use in direct contact with the skin.

12th APMAS 2022 International Advances in Applied Physics & Materials Science Congress & Exhibition, Mugla, Turcia, 2022 (Stage:1)

74th Annual Meeting of the International Society of Electrochemistry, Lyon, Franta, 2023 (Stage:2)

13th APMAS 2022 International Advances in Applied Physics & Materials Science Congress & Exhibition, Mugla, Turcia, 2023 (Stage:2)

A/00737/25.11.2024 - “Dispozitive electrochimice pe bază de ionofori și lipozomi pentru detecția ionilor de sodiu, potasiu și clor” 

Anca Aldea, Victor C. Diculescu

Anca ALDEA (DIBLĂ)

National Institute of Materials Physics

Laboratory of Multifunctional Materials and Structures

405A Atomistilor Street

077125, Magurele, Romania

E-mail: anca.aldea@infim.ro

Mobile: +40735157040