The main goal of NAQUANTA is the development of a bio-analytical device for quantification and detection of nucleic acids (NAs). The device consists of two elements: i) an electrochemical sensing system able to quantify and determine the NAs concentration; and, ii) a temperature control system or microheater essential for enzymatic reactions during NAs amplification processes. These two components will be equipped with metal-coated electrospun polymeric fibers electrodes attached on the microfluidics support for sample transport. A hydrogel will act as solid-state electrolyte necessary for NAs detection and amplification and, at the same time as a physical barrier for the components of the detection system. In order to achieve the main goal of the project the following objectives are envisaged:

O1. fabrication of electrodes through attachment of metal-coated electrospun polymeric fibers on solid support with imprinted microchannels. This step is essential for the fabrication of both components of the device;

O2. fabrication of the sensing element. Finding the best electrodes’ architecture, combinations and/or modification, the solid-state electrolyte, and testing its capacity for detection and quantification of NAs.

O3. fabrication of the microheater. Finding the best electrode’s architecture, investigating the spatial distribution of power dissipation and consequently their heating capacity.

The project is carried out by the group of Lab. 10. Functional Nanostructures of the National Institute of Materials Physics

The results were disseminated through presentations at meetings and conferences:

1. V.C. Diculescu, New Electrode Architectures Based on Electrospun Polymeric Fibers For (Bio)Sensing Applications, at the 18th International Conference on Electroanalysis - ESEAC 2022, 5 - 9 Iunie 2022, Vilnius, Lituania. Invited talk.

2. D. Botta, Electrochemical Devices with Metallized Electrospun Fiber Meshes Electrodes, at the Biosystems in Toxicology and Pharmacology – Current challenges, online, 8-9 September 2022, Leiria, Portugal. Oral Presentation.

3. V.C. Diculescu, Electrospining for electrochemical applications, at the Biosystems in Toxicology and Pharmacology – Current challenges, online, 8-9 September 2022, Leiria, Portugal. Keynote lecture.

Phase 1. The electrodes and the micro-fluidic system (2022)
Three activities were carried out during the Phase 1 of NAQUANTA implementation.
Activity 1.1.Electrospun polymeric fibers
was dedicated to electrospinning of polymeric solutions such as poly(methyl methacrylate) and nylon. The process parameters were investigated and optimized in order to achieve robust polymeric fiber meshes. The obtained fiber meshes were then subjected to coating with thin layers of Au, Ag, Pt or AgCl by magnetron sputtering deposition, which allowed the fabrication of electrodes.
Activity 1.2. Attachment of the metallized polymeric fibers on solid support
The metallized electrospun polymer fiber meshes were transferred by thermal treatment on four different substrates: polyethylene terephthalate, dimethyl polysiloxane, filter or chromatography paper. The morphologies of the assemblies formed by the metallized polymer fibers and these substrates were investigated by scanning electron microscopy, while the chemical and structural composition was analyzed by X-ray photoelectron spectroscopy and X-ray diffraction analysis.
Activity 1.3. Microfluidic system
The investigations performed within this activity were dedicated to the microfluidic system which was obtained on chromatographic paper by 3D printing with wax filaments and polymeric materials with wax-like properties. Printing and diffusion tests were carried out in order to achieve an ideal hydrophobic barrier that allows confining the fluids in a determined area/volume, restricting at the same time their diffusion throughout the entire paper pad.

The attachment of the metallized polymeric fibers on the two sides of the microfluidic system, allowed the development of an electrochemical sensor/cell on chromatographic paper, Figure 1. The electrochemical response was investigated in two- and three-electrode architectures. The functionality of the sensors was investigated electrochemically under different conditions of pH, composition of the supporting electrolyte, but also in the absence and presence of different redox samples. Electrochemical analysis was performed by cyclic voltammetry and electrochemical impedance spectroscopy.

Figure 1. Photographs of the 3D printed microfluidic systems on chromatographic paper with three Au/PMMA electrodes in different configurations.

The project involve training of three PhD students and two Post-doc Researchers in biosensing technologies and engineering.

1. R. J. B. Leote, M. Beregoi, I. Enculescu, V.C. Diculescu, Metallized electrospun polymeric fibers for electrochemical sensors and actuators, Current Opinion in Electrochemistry, 2022, 34:101024. IF 7.664; AIS 1.411; Q1 (in Electrochemistry and in Chemistry, Physical)
2. R.J.B. Leote, C.G. Sanz, V.C. Diculescu, Electrochemical characterization of shikonin and in-situ evaluation of interaction with DNA, Journal of Electroanalytical Chemistry, 2022, 921: 116663. IF 4.598; AIS 0.568; Q1 (in Chemistry, Analytical)
3. M.C. Bunea , V.C. Diculescu, M. Enculescu, D. Oprea, T.A. Enache, Influence of the Photodegradation of Azathioprine on DNA and Cells, International Journal of Molecular Sciences, 2022, 23:14438. IF 6.208; AIS 1.064; Q1 (in Biochemistry & Molecular Biology)