National Institute Of Materials Physics - Romania

The present study aims to develop and investigate the biological response of a bone substitute based on electrospun polyvinylidene fluoride (PVDF) fibres, which are either embedded or coated with a silicate bioglass belonging to SiO2-P2O5-CaO-Na2O oxide system. This bioglass is substituted with antibacterial agents, silver (Ag) and cerium (Ce), while deposition methods utilized include pulsed laser deposition (PLD) and matrixassisted pulsed laser evaporation (MAPLE). The results showed the inhomogeneous distribution of the glassy particulate phase in the polymer fibres when using electrospinning as single processing technique. In contrast, the materials achieved by combining the electrospinning with laser ablation displayed a continuous coating of glass at the polymer fibres surface. The thickness and roughness of this layer can be easily tuned as a function of deposition conditions, as it was demonstrated when changing the dispersion medium or working pressure. Good results were obtained for all coated PVDF fibres, but especially in the case of PLD processing with a thicker layer of silicate glass, the imaging evaluation suggested a superior beneficial impact on cellular metabolism. Such scaffolds, with controlled porosity, engineered surface and potential piezoelectric properties represent important candidates for the field of personalized bone substitutes.

Capitalizing on invasive plant species and stopping their aggressive spread might be achieved by using them as a renewable source of useful products such as cellulose. The study aimed to develop new cellulose-based food packaging materials with antioxidant and antimicrobial activity. The cellulose was extracted from the invasive plant species Robinia pseudoacacia pods, crosslinked with citric acid, used as reinforcement for polyvinyl alcohol (PVA) and functionalized with ferulic acid (FA). The obtained materials were characterized by XRD, ATR-FTIR, contact angle and SEM. The materials exhibited low solubility in water and the swelling degree was proportional to the FA content. The FA release from the matrix was assessed by HPLC and the antioxidant profile by CUPRAC, FRAP, and TEAC methods. The obtained materials inhibited the growth of bacteria, yeasts and molds, being especially active on Gram-positive bacteria and yeasts. Overall, the most promising formulation for further developing new packaging materials for products with water activity less than 0.95 was the one with the highest FA content.

Kynurenic acid (KA) is an active metabolite of tryptophan with notable biological effects, such as antioxidant, neuroprotective, and anti-inflammatory properties. It often undergoes changes of the concentration in biological fluids in chronic diseases. Thus, detecting KA is of great importance for diagnosing inflammatory and neurodegenerative conditions, monitoring disease progression, and assessing responses to pharmacological treatment. This study aimed to design a tailored, flexible platform for sensitive and direct electrochemical detection of KA in biological fluids. Carbon-based electrodes were custom-printed in the lab using specialized inks and flexible substrates. The working electrodes were further functionalized with graphene oxide and subsequently electrochemically reduced to increase the sensitivity toward the analyte. An optimized differential pulse voltammetry protocol was developed for KA detection. The elaborated platform was firstly characterized and then evaluated regarding the analytical performances. It showed a good limit of detection (3 nM and demonstrated the capability to detect KA across a broad concentration range (0.01-500 mu M). Finally, the elaborated flexible platform, was succesfully applied for KA determination in serum and saliva samples, in comparison with an optimized HPLC-UV method. The developed platform is the first example of in-lab printed flexible platform reported in literature so far for KA detection. It is also the first study reported in the literature of detection of KA in raw saliva collected from 10 subjects. The sensitivity towards the target analyte, coupled with the adaptability and portability, showcases the potential of this platform for thus illustrating great potential for further development of wearable sensors and biomedical applications.

Cu-doped hydroxyapatite (CuHAp) thin films were obtained using spin coating method. To make these thin films, CuHAp suspensions obtained by sol-gel method were used. The coatings obtained were thermally treated at 500 degrees C. After the thermal treatment, the thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Moreover, the stability of the suspensions before being used to obtain the thin films was certified by dynamic light scattering (DLS), zeta potential methods and ultrasound measurements. In the XRD patterns, the peaks associated with hexagonal hydroxyapatite were identified in accordance with JCPDS no. 09-0432. EDS and XPS results confirmed the presence of Cu ions in the samples. Data about the morphological features and chemical composition of CuHAp thin films were obtained by performing scanning electron microscopy (SEM) measurements. Our results suggest that the CuHAp thin films surface is continuous and homogenous. The presence of the functional groups in the CuHAp thin films was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy studies. Information about the surface topography of the CuHAp thin films has been obtained using atomic force microscopy (AFM). The AFM images determined that the surface topography of the CuHAp thin layer is homogenous and continuous without presenting any unevenness or fissures. The cytotoxicity of CuHAp thin films was assessed using human gingival fibroblasts (HGF-1) cells. The results of the cell viability assays demonstrated that the thin films presented good biocompatible properties towards the HGF-1 cells. Additionally, the adherence and development of HGF-1 cells on the surface of CuHAp thin films were determined using AFM. The AFM surface topographies highlighted that the CuHAp thin film's surface favored the attachment and proliferation of HGF-1 cells on their surface.

In the current study, a porous composite material, hydroxyapatite/chitosan/microcrystalline-cellulose (CaHAp-CS-MCC), was successfully prepared and used for the adsorption of Eriochrome Black T (EBT) from water. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), specific surface area (SSA), and atomic force microscope (AFM) were used to evaluate the physicochemical properties of the prepared adsorbents. CaHAp-CS-MCC exhibited a decrease in crystallinity and reduction in crystallite size. CaHAp-CS-MCC surface exhibited cracks and pores. AFM displayed changes in surface micro-texture of CaHAp, formation of new surface structures, and variations in particle size and distribution. Upon grafting CaHAp with CS and MCC, its specific surface area decreased from 139.224 to 11.775 m2/g. BET suggested that filling CaHAp pores by CS and MCC contributed to the reduction in surface area. The pore volume values decreased from 2.56 x 10-1 (CaHAp) to 3.91 x 10-2 cm3/g (CaHAp-CS-MCC). Adsorption equilibrium was reached at about 40 min. The adsorption capacities values of CaHAp-CS-MCC and CaHAp were equal to 248 mg/g and 92 mg/g, respectively. The pseudo-second order and the Langmuir equations fitted well the adsorption phenomenon. The calculated thermodynamic parameters showed an exothermic and non-spontaneous system.

In the present work, we report the synthesis and investigations of La0.9K0.1MnO3 and La0.8K0.1Pb0.1MnO3 bulk samples which could be potential magnetocaloric materials for magnetic refrigeration close to room temperature. A flash combustion reaction and sintering at 1200 degrees C for 10 h are used to prepare the bulk materials. Both compounds crystallized into a rhombohedral structure with R3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{3 }$$\end{document}c space group confirmed by X-ray powder diffraction results. Scanning electron microscopy analysis, combined with XRD peak profiles is performed to estimate the particle/crystallite size of the samples. Moreover, the Curie temperature, TC, is found to be higher in lead-rich sample due to the enhancement of the grain size and the Mn3+-O-Mn4+ double exchange (DE) interaction. Therefore, the bulk sample La0.8K0.1Pb0.1MnO3 shows a room temperature phase transition of 289 K as well as a higher saturation magnetization. The La0.8K0.1Pb0.1MnO3 bulk compound exhibits a high and sharp peak in magnetic entropy change up to 5.5 Jkg-1 K-1 under 5 T at the magnetic transition temperature TC. To compare the magnetocaloric performances of the studied compounds, relative cooling power (RCP) was employed. The obtained experimental results revealed that the increase in particle size influences severely the magnetocaloric properties.

This research targets the need for eco-friendly strategies in the synthesis of bioactive materials, addressing the importance of valorization of vegetal waste. This study focuses on developing biohybrids containing biomimetic lipid vesicles and phytosynthesized gold-silver chloride nanoparticles (AuAgCl NPs) derived from Achillea millefolium L. extract. By leveraging the natural antioxidant and antimicrobial properties of the plant, the research proposes a sustainable approach to creating materials with potential biomedical applications. The biomimetic membranes were loaded with chlorophyll a, a natural spectral marker. Three types of bioactive materials (biohybrids) were developed by varying the lipid vesicle/AuAgCl NP ratio. Optical (UV-Vis, fluorescence emission, FTIR), structural (XRD), elemental (EDX, XPS), and morphological (TEM) studies were performed to characterize the bio-developed materials. The hydrophobic/hydrophilic characteristics of the samples were investigated by measuring the water contact angle, and their size was estimated by DLS and TEM. Zeta potential measurements were used to evaluate the physical stability of phyto-developed particles. Antioxidant properties of phyto-particles were investigated through the chemiluminescence technique. The obtained biomaterials exhibited high antioxidant activity and antiproliferative activity against HT-29 and B-16 cancer cells. Therapeutic index values were calculated for each biohybrid. Additionally, the bio-prepared hybrids revealed biocidal action against Staphylococcus aureus and Enterococcus faecalis. The phyto-developed biomaterials are promising in biomedical applications, particularly as adjuvants in cancer therapy.

Nowadays, the development of devices based on organic materials is an interesting research challenge. The performance of such devices is strongly influenced by material selection, material properties, design, and the manufacturing process. Usually, buckminsterfullerene (C60) is employed as electron transport material in organic photovoltaic (OPV) devices due to its high mobility. However, considering its low solubility, there have been many attempts to replace it with more soluble non-fullerene compounds. In this study, bulk heterojunction thin films with various compositions of zinc phthalocyanine (ZnPc), a perylene diimide derivative, or C60 were prepared by matrix-assisted pulsed laser evaporation (MAPLE) technique to assess the influence of C60 replacement on fabricated heterostructure properties. The investigations revealed that the optical features and the electrical parameters of the organic heterostructures based on this perylene diimide derivative used as an organic acceptor were improved. An increase in the JSC value (4.3 x 10-4 A/cm2) was obtained for the structures where the perylene diimide derivative acceptor entirely replaced C60 compared to the JSC value (7.5 x 10-8 A/cm2) for the heterostructure fabricated only with fullerene. These results are encouraging, demonstrating the potential of non-fullerene compounds as electron transport material in OPV devices.

Among many iron-based superconductors, isovalently substituted BaFe2(As1-xPx)2 displays, for x approximate to 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes-field cooling, zero-field cooling, and field cooling with measurements during warming up-we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP.