National Institute Of Materials Physics - Romania

A hybrid hydroxyapatite/chitosan/microcrystalline-cellulose (CaHAp-CS-MCC) biocomposite was synthesized via a co-precipitation-lyophilization route and comprehensively characterized for potential biomedical applications. X-ray diffraction confirmed the formation of a single-phase hexagonal hydroxyapatite (P-63/m, JCPDS 09-0432) with an average crystallite size of similar to 15 nm and slight lattice contraction induced by polymer incorporation. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy evidenced strong interfacial bonding between hydroxyapatite phosphate groups and the amino and hydroxyl functionalities of chitosan and cellulose. Microscopic analyses (SEM, AFM) revealed a denser, rougher surface with root-meansquare roughness rising from 9 to 36 nm, accompanied by modified particle distribution. Nitrogen adsorption-desorption (BET) analysis indicated a decrease of specific surface area (139 -> 12 m(2) g(- 1)) and an increase of pore diameter (7.4 -> 13.3 nm), confirming partial pore filling by the organic matrix. Hemolysis indices below 2 % and >90 % HeLa-cell viability after 72 h indicated excellent hemocompatibility and cytocompatibility. The synergistic integration of crystalline hydroxyapatite with flexible, bioactive polymers yields a stable and biocompatible composite suitable for bone regeneration, implant coatings, and other advanced biomedical applications.

Monitoring superoxide anion in chronic wounds is critical for understanding oxidative stress and guiding personalized treatment. We present a novel electrochemical biosensor enabling real-time superoxide detection in cell culture, integrating enzymatic selectivity with a biocompatible electrospun membrane for direct tissue contact. The biosensor employs screen-printed electrodes (SPE) modified with electropolymerized poly(3,4ethylenedioxythiophene) (PEDOT), which enhances enzyme immobilization and signal transduction, with superoxide dismutase (SOD) for enhanced selectivity. The analytical performance of SPE/PEDOT/SOD biosensor was evaluated by fixed potential amperometry at +0.3 V with a sensitivity of 130.3 +/- 5.6 mu A cm- 2 & sdot;mM- 1, and a 1.5 mu M detection limit. A cell-based wound model was developed to simulate chronic wound conditions, using an adhesive membrane modified with electrospun Nylon fibers that provided a biocompatible surface for cell adhesion and proliferation. Cells cultured on the membrane were irradiated with UV light to induce superoxide generation, mimicking oxidative stress in chronic wounds. Although the membrane introduced a diffusion barrier that reduced sensitivity by 40 %, it ensured close contact between cells and the electrode surface, enabling accurate in situ quantification of superoxide. Chronoamperometric detection at +0.3 V revealed sharp photocurrent peaks followed by decay, consistent with ROS generation and enzymatic clearance. The PEDOT matrix exhibited a photo-amplifying effect, nearly tripling the sensitivity under UV irradiation. The developed device is suitable for real-time oxidative stress profiling in wound models with potential for ex vivo and in vivo applications.

Boron-doped silicon detectors used in high radiation environments like the future HL-LHC show a degradation in device performance due to the radiation induced deactivation of the active boron dopant. This effect, known as the so-called Acceptor Removal Effect (ARE), depends on particle type, particle energy and radiation dose and is usually explained by the formation of boron-interstitial-oxygen-interstitial (BiOi) defects that induce a donor-type defect level in the upper part of the Si band gap. Here we present defect characterization studies using Thermally Stimulated Current technique (TSC) and Deep Level Transient Spectroscopy (DLTS) on a set of epitaxially grown p-type silicon diodes of different resistivity, irradiated with 60Co gamma-rays. We used the defect parameters (activation energy, charge carrier capture cross sections and defect concentration) obtained from DLTS experiments for modeling the corresponding TSC spectra, and subsequently compared those with the experimental TSC results. This approach shows that the di-vacancy which is well characterized by DLTS correlates with the so-far unspecified charge emission signal of the X-defect that partially overlaps with the BiOi peak in TSC spectra. Additionally, in order to evaluate the impact of BiOi defect formation on the macroscopic properties of the device, we compared the BiOi defect concentration with the change in the effective carrier concentration Neff obtained from C-V measurements. It shows that the variations in Neff are about twice the changes in the BiOi concentration, which corroborate the assumption of boron deactivation by the formation of the BiOi donor in irradiated p-type Si.

Layers of HfO2 and (Hf,Zr)O2 crystalline nano-particles are synthesized via direct liquid injection atomic layer deposition, and a comprehensive set of structural, chemical, and electrical characterizations is employed to elucidate their phase composition and functional behavior. X-ray photoelectron spectroscopy revealed a compositional contrast between the films: (Hf,Zr)O2 layers contained up to 45% stoichiometric oxide, while pure HfO2 films are dominated by sub-oxides, especially under strongly reducing conditions, in which exclusively sub-oxide phases and p-type semiconducting behavior is revealed. Electrical measurements indicated room-temperature stabilization of polar phases and tetragonal-to-orthorhombic phase transition with a Curie temperature near 200 K. FTIR spectroscopy confirmed the presence of tetragonal and orthorhombic HfO2 phases, providing insight into minor features observed approximate to 30 degrees (2 theta) in X-ray diffraction patterns. Notably, devices incorporating an AlN interlayer demonstrated a significant enhancement in pyroelectric performance, suggesting this strategy to advance the pyroelectric performance of HfO2-based materials, supporting their development for lead-free sensor technologies.

In this work, we investigate the electrical properties of a ternary biocomposite material based on a vinyl resin (VR) matrix filled with two types of fillers, namely green microcrystalline cellulose (MCC) and carbon nanotubes (CNT), over a frequency range of 10-1 to 107 Hz and a temperature range from 10 to 130 degrees C. Thermal analyses were carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), which revealed significant changes in the glass transition and degradation temperatures of the biocomposite, respectively. The electrical measurements were analyzed using two formalisms: (i) Electrical conductivity, which showed the presence of two distinct low-frequency behaviors associated with quasi-dc conductivity below the glass transition temperature and dc conductivity above it, along with high-frequency dispersion, which allows determining the ac conductivity mechanisms using Jonscher's power law, and (ii) Electric modulus, which revealed a low-temperature relaxation originating from water dipole polarization and two high-temperature dielectric relaxation processes. The first high-temperature relaxation, observed at low frequencies, was attributed to the Maxwell-Wagner-Sillars (MWS) effect, while the second, appearing at high frequencies, was associated with the alpha-relaxation. These relaxations were modeled using Bergman's equation. Furthermore, the temperature dependence of the relaxation time and dc conductivity were analysed using an Arrhenius representation.

Zinc oxide (ZnO) semiconducting nanoparticles were added to a nematic liquid crystal (NLC) mixture E7, and the influence of these particles on the spectroscopic and dielectric properties of the E7 mixture was studied. ZnO nanoparticles were obtained using a recently developed green method involving clove extract. The proportion of ZnO:LC in the mixture was varied between 1:99 and 95:5% to ensure accessibility of the particle surface for interactions with LC. These natural compounds not only facilitate the formation of stable nanostructures, but also promote surface functionalization, influencing the resulting morphology, crystallinity, and dispersion behavior of the nanoparticles in the host media. Because the classical fitting models were inadequate in our systems with multiple overlapping relaxation and conduction processes, derivative-based numerical methods were employed. Such approaches enabled the resolution of up to three distinct dielectric relaxation processes and allowed the extraction of characteristic frequencies and activation energies, and insight into the underlying interfacial phenomena between the ZnO nanoparticles and LC molecules was obtained. We assumed that the interaction between the two components of the composites (NLC and ZnO) was weak, which contributes to a deeper understanding of the interplay between biofunctionalized nanostructures and anisotropic soft matter environments.

Background: Hepatocellular carcinoma is associated with high mortality and increasing incidence. Sorafenib, a cornerstone of therapy for advanced hepatocellular carcinoma, presents certain disadvantages, including low bioavailability and poor water solubility. This work describes a new strategy for sorafenib-targeted delivery aimed at improving treatment efficiency and reducing side effects. Methods: Magnetic nanoparticles coated with azelaic acid were modified with aptamer molecules that specifically recognize human liver cancer cell line HepG2, ensuring specificity for the tumor tissue. The nanoparticles were further loaded with sorafenib. The obtained drug delivery system was extensively characterized using UV-Vis spectrophotometry, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. Results: The drug delivery system demonstrated a higher release of sorafenib at acidic pH compared to pH 7.4. The cell internalization of the bare and aptamer-modified magnetic nanoparticles was assessed in HepG2 and human normal foreskin fibroblasts BJ cell lines, demonstrating that the aptamer significantly enhances internalization in tumor cells, while having no impact on healthy cells. Conclusions: The sorafenib-modified nanoparticles exhibited excellent cytocompatibility with BJ cells across all tested concentrations, while showing cytotoxicity towards HepG2 cells at higher concentrations, confirming the selectivity of the system.

Superoxide plays a significant role in maintaining physiological states of living systems, with major roles in eradicating invading microorganisms and in cell signaling. It is regulated intricately by the enzyme superoxide dismutase (SOD), and when not properly regulated it can lead to cascade biological pathways with severe and irreversible damage to biofilms, tissue, and organs, being linked with many neurodegenerative diseases, atherosclerotic and cardiovascular diseases. Therefore, superoxide anion (O center dot-2 ) detection has a tremendous potential in clinical diagnostics to assess oxidative stress in living cells. This comprehensive review aims to explore, discuss, and analyze recent trends in the electrochemical detection of O center dot-2 in living systems, focusing not only on the recognition mechanism for in vitro assays (living cell cultures/tissues) but also on the importance of the electrode design and operational parameters for in vivo measurements (implantable sensors). By analyzing current in vitro/in vivo electrochemical strategies we gather information that is helpful to overcome existing limitations in the dynamic monitoring of O center dot-2 , and further improve electrochemical strategies that can be adopted and applied to prevent its negative effect, with an insight into the pathophysiology of neurodegenerative disorders and even cellular malignancies that derive from its accumulation in living systems.

Chromium-doped hydroxyapatite (7CrHAp) and chromium-doped hydroxyapatite in chitosan matrix (7CrHAp-CH) coatings were synthesized in order to address the need for biomaterials with improved physico-chemical and biological properties for biomedical applications. Both chromium-doped hydroxyapatite (7CrHAp) and chromium-doped hydroxyapatite in chitosan matrix (7CrHAp-CH) coatings could represent promising materials for biomedical applications due to their superior properties. This study aims to evaluate the physico-chemical and in vitro biological properties of 7CrHAp and 7CrHAp-CH coatings to determine the impact of chitosan incorporation on the physico-chemical and biological features. The results reported in this study indicate that addition of chitosan improves surface uniformity and biological properties, highlighting their potential for uses in biomedical applications. In this study, coatings of chromium-doped hydroxyapatite (7CrHAp, with xCr = 0.07) and its composite variant embedded in a chitosan matrix (7CrHAp-CH) were systematically analyzed using a suite of characterization techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and metallographic microscopy (MM). The results of the XRD analysis revealed that the average crystal size was 19.63 nm for 7CrHAp and 16.29 nm for 7CrHAp-CH, indicating a decrease in crystallite size upon CH incorporation. The films were synthesized via the dip coating method using stable suspensions, whose stability was assessed through ultrasonic measurements (double-distilled water serving as the reference medium). The values obtained for the stability parameter were 2.5910-6 s-1 for 7CrHAp, 8.6410-7 s-1 for 7CrHAp-CH, and 3.1410-7 s-1 for chitosan (CH). These data underline that all samples are stable: CH is extremely stable, followed by 7CrHAp-CH (very stable) and 7CrHAp (stable). The in vitro biocompatibility of the 7CrHAp and 7CrHAp-CH coatings was evaluated with the aid of the MG63 cell line. The cytotoxic potential of these coatings towards MG63 cells was quantified using the MTT assay after 24 and 48 h of incubation. Our results highlight that both 7CrHAp and 7CrHAp-CH coatings exhibit high biocompatibility with MG63 cells, maintaining cell viability above 90% at both incubation times, thus supporting osteoblast-like cell proliferation. Furthermore, the antimicrobial efficacy of both 7CrHAp and 7CrHAp-CH samples was evaluated in vitro against the Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa) reference strain. The in vitro antibacterial activity of the 7CrHAp and 7CrHAp-CH coatings was further evaluated against Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa), Escherichia coli ATCC 25922 (E. coli) and Staphylococcus aureus ATCC 25923 (S. aureus) reference strains. In addition, atomic force microscopy (AFM) analysis was also used to investigate the ability of P. aeruginosa, E. coli and S. aureus cells to adhere and to develop colonies on the surfaces of the 7CrHAp and 7CrHAp-CH coatings. The results from the biological assays indicate that both coatings exhibit promising antibacterial properties, highlighting their potential for being used in biomedical applications, particularly in the development of novel antimicrobial devices.

The rapid growth of the global population has increased the need for efficient fabrication methods and materials to purify polluted water. In this study, we report the fabrication and characterization of reusable and efficient three-dimensional (3D) polydimethylsiloxane (PDMS) sponge composites designed for water treatment applications. By varying the ratios (10/90, 30/70, and 50/50) of large and small sacrificial templates' particles used in the fabrication method, we tailored the sponge's morphology and the interconnected pores' distribution. To achieve an enhanced photocatalytic activity, we incorporated titanium dioxide (TiO2) at different concentrations (1 % TiO2, 5 % TiO2, and 10 % TiO2 w/w) into the PDMS matrix. Scanning electron microscopy (SEM) was used to evaluate the structure of both 3D PDMS and TiO2@PDMS sponges, while energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) confirmed the successful incorporation of TiO2 into the sponge framework. The photocatalytic performance of the 3D TiO2@PDMS composites was assessed by monitoring the degradation of Rhodamine B (RhB) under solar light irradiation, and the results were compared to those obtained using reference (TiO2-free) sponges under identical conditions. Very low Ti leaching effect have been evidenced by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The reusability of the sponges was demonstrated through complete bleaching of the 554 nm RhB absorption band after four consecutive degradation cycles.