National Institute Of Materials Physics - Romania

Novel biocompatible composite hydrogels with good elastic and antimicrobial properties have been fabricated by e-beam cross-linking using chitosan and water-soluble polymers mixed with commercial silver nanoparticles (AgNP). Hydrogels having different formulations were characterized by rheological, swelling, FTIR, SEM, and biodegradation measurements. The network structure, biocompatibility, and antimicrobial properties were evaluated as well. The composite hydrogels showed higher stability and absorb large amounts of fluids specific to an infected wound without losing structural integrity. The rheological, SEM, and network structure results demonstrate that at above 0.1 mg/mL AgNP, hydrogels with high cross-linking density are obtained. The in vitro response of fibroblasts proved the high biocompatibility of the hydrogel's composites. The antimicrobial activity is directly influenced by the amount of AgNP and cross-linking degree of the hydrogel. Significant antimicrobial activity was recorded against Gram-negative bacteria, while for the Gram-positive ones, the growth inhibition seems to require a decrease of the cross-linking degree.

Selective growth of 2D MoS2 layers on patterned substrates is highly desired for easy fabrication of devices. Selectively grown 2D MoS2 on Mo patterned substrates for the formation of intimate metallic contact was obtained by a Mo-CVD method in which MoO2 from an oxidized Mo pattern and S powder are the growth precursors. Mo films were deposited by magnetron sputtering on SiO2(300 nm)/c-Si substrates and patterned by photolithography techniques for obtaining Mo strips and finger contact structures, with the gap between the strips and finger varied from 5 to 20 mu m. The filling of the gap by selectively grown atomically thin MoS2 plates of 1-2 monolayers (MLs) was demonstrated by scanning electron microscopy and atomic force microscopy imaging. Field effect devices for the characterization of the photosensitivity of selectively grown MoS2 have been fabricated from finger contact structures. The dark current is drastically reduced from 10(-9) to 10(-13)-10(-14) A by varying the gate voltage from +7 to -7 V, showing the n-type semiconductor behavior of the selectively grown 2D MoS2. High photosensitivity of 10(5) (%) was obtained for 4.5 x 10(-4) mW/cm(2) at 650 nm wavelength illumination. The spectral responsivity reaches values of 15-25 A/W at 600 nm wavelength and shows an energy onset of 1.72-1.77 eV corresponding to about 2 ML MoS2. The carrier-trapping effect responsible for the slow part of the device response can be caused by structural defects and also by adsorbed molecules like in gas sensors.

This work describes the development of a flexible uric acid (UA) biosensor based on palladium-coated submicrometer electrospun poly(methylmethacrylate) (PMMA) fibers metalized with gold and attached to polyethylene terephthalate substrate (Pd/Au/PMMA/PET). The morphological characterization conducted by scanning electron microscopy revealed nanoscale Pd dendritic structures. Electrochemical investigations in the absence and in the presence of redox probes demonstrated that these Pd nanostructures are responsible for a six-fold increase in the electroactive area and enhanced electron transfer kinetics when compared to the gold-coated electrospun fibers. The UA biosensor obtained by immobilizing the uricase enzyme (UrOx) onto the Pd/Au/PMMA/PET electrode surface, allowed UA detection with a sensitivity of 431 mu A cm(-2) mM(-1) and a limit of detection of 12 mu M. Investigation of the redox reactions of hydrogen peroxide (a product of the enzymatic oxidation of UA by UrOx) at the Pd/Au/PMMA/PET electrode demonstrated that the working principle of the biosensor is based on the reduction of PdO produced at the electrode surface during the spontaneous reduction of hydrogen peroxide on Pd. This allows a biosensor operating potential of -0.05 V (vs Ag/AgCl) with high selectivity. The UrOx/Pd/Au/PMMA/PET biosensor was applied for UA detection in body fluids (sweat, urine, and blood serum) with recovery values between 98 and 105%, which were validated by high-performance liquid chromatography analysis. The stability of the device was evaluated over a period of 3 months, retaining 78% of the initial sensitivity, and reproducibility with RSD = 4.9% was achieved. The analytical performance of the biosensor under harsh mechanical deformations and at physiological temperatures demonstrated the potential applications of the device to wearable sensing platforms.

This work describes the development of a flexible uric acid (UA) biosensor based on palladium-coated submicrometer electrospun poly(methylmethacrylate) (PMMA) fibers metalized with gold and attached to polyethylene terephthalate substrate (Pd/Au/PMMA/PET). The morphological characterization conducted by scanning electron microscopy revealed nanoscale Pd dendritic structures. Electrochemical investigations in the absence and in the presence of redox probes demonstrated that these Pd nanostructures are responsible for a six-fold increase in the electroactive area and enhanced electron transfer kinetics when compared to the gold-coated electrospun fibers. The UA biosensor obtained by immobilizing the uricase enzyme (UrOx) onto the Pd/Au/PMMA/PET electrode surface, allowed UA detection with a sensitivity of 431 mu A cm(-2) mM(-1) and a limit of detection of 12 mu M. Investigation of the redox reactions of hydrogen peroxide (a product of the enzymatic oxidation of UA by UrOx) at the Pd/Au/PMMA/PET electrode demonstrated that the working principle of the biosensor is based on the reduction of PdO produced at the electrode surface during the spontaneous reduction of hydrogen peroxide on Pd. This allows a biosensor operating potential of -0.05 V (vs Ag/AgCl) with high selectivity. The UrOx/Pd/Au/PMMA/PET biosensor was applied for UA detection in body fluids (sweat, urine, and blood serum) with recovery values between 98 and 105%, which were validated by high-performance liquid chromatography analysis. The stability of the device was evaluated over a period of 3 months, retaining 78% of the initial sensitivity, and reproducibility with RSD = 4.9% was achieved. The analytical performance of the biosensor under harsh mechanical deformations and at physiological temperatures demonstrated the potential applications of the device to wearable sensing platforms.

The bioavailability of the administered drugs that reach the systemic circulation is the first point in resolving the pathology of patients. Albumin-based nanoparticles represent an increasingly used strategy to deliver cancer drugs into cells that otherwise cannot overcome biological barriers. In this work, rutin (Ru), a flavonoid with anticancer and antioxidant potential, was incorporated into bovine serum albumin nanoparticles (BSA-Ru NPs), developed using the desolvation method, and the entire system was characterized and evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis absorption spectroscopy. The results showed that BSA and BSA-Ru NPs are uniformly distributed, have relatively large sizes, and have a time stability of more than 60%. Furthermore, the effect of these nanohybrids on the thermal stability of liposomal membranes was evaluated by surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The viability evaluation was assessed by the tetrazolium salt (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) protocol in the fibroblast L929 line and a high level of biocompatibility, confirmed by SEM results, was found.

This study reports the development of a novel biocomposite for potential applications in the environmental remediation. The hydroxyapatite/sodium bicarbonate (HAp-SB) biocomposite obtained by a cheap method could offer promising characteristics to be used in environmental applications. The obtaining of HAp-SB ceramic composites was studied with the aim of increasing the adsorption efficiency of lead ions from contaminated waters. A composite material (HAp-SB) with good crystallinity that preserves the hexagonal structure of pure hydroxyapatite was obtained. For the powder recovered after decontamination of the lead solution (PbHAp-SB), the XRD model highlighted additional maxima belonging to Ca10(PO4)5(OH)2, Ca0.805Pb4.195(PO4)(OH) and PbH2P2O7. The FTIR spectra of PbHAp-SB are similar to those of HAp-SB composites showing a broadening of the vibration peaks and a slight shift. The XPS and EDS studies illustrated the purity of the HAp-SB sample. Moreover, the presence of lead in the powder recovered after decontamination was also highlighted by XPS and EDS studies. The efficiency of HAp-SB in the adsorption of Pb2+ ions from the contaminated solution was also highlighted by ultrasound studies using double-distilled water as the reference liquid. The adsorption kinetics were investigated with the aid of Langmuir and Freundlich theoretical models. The results demonstrated that the HAp-SB ceramic composite has a strong affinity for the adsorption of Pb2+ ions from contaminated solutions. The removal efficiency of Pb2+ ions was about 92% for the initial Pb2+ concentration above 50 mg/L. The results of the cell viability and cytotoxicity studies demonstrated that HAp-SB nanoparticles did not influence negatively the HeLa cell's viability and did not induce any significant changes of the morphological features of HeLa cells after 24 h of incubation. The batch adsorption results as well as the cytotoxicity assay results suggested that the HAp-SB powder could be successfully used for the removal of Pb2+ from contaminated water.

Electrospun nanofibres based on poly(styrene sulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) were fabricated using a straightforward procedure which combines electrospinning, sputtering deposition and electrochemical synthesis. In general, electrospun fibre meshes based on conducting polymers are prepared by mixing the conducting polymer with a carrier polymer or chemically coverage of the fibres. In contrast, freestanding nylon 6/6 nanofibre webs were prepared through electrospinning and were coated by sputtering with gold in order to make them conductive. Further, a PEDOT:PSS layer was electrochemically deposited onto the metalized nanofibre meshes and the synthesis parameters were chosen in such a way to preserve the high active area of the fibres. The prepared material was morphologically characterized and the formation of PEDOT:PSS was also demonstrated. The PEDOT:PSS coated nanofibres revealed remarkable electrical properties (sheet resistance of about 3.5 Omega cm(-2)), similar to those of metalized nanofibres (sheet resistance around 3 Omega cm2). The in vitro studies using L929 fibroblast mouse cells showed that the bioactive material has no cytotoxic effect and allows proliferation. Moreover, after 72 h of incubation, the fibroblasts shrunk their nuclei and spread suggesting that a differentiation in myofibroblast occurs without application of any kind of external stimuli. These results will be helpful for developing efficient materials for wound healing applications that work without energy consumption.

Undoped and Sm3+doped 45P2O5-45Na2O-2Al2O3-8BaO glasses were synthesized by the melt-quenching technique. The glass structure and luminescence properties were investigated by using Raman spectroscopy, scanning electron microscopy (SEM), spectroscopic ellipsometry, Judd-Ofelt theory and photoluminescence. Electron microscopy showed the homogeneity of samples. Raman spectroscopy revealed that the overall struc-ture of the glass was unaffected by the doping of Sm3+ and ellipsometry was used to measure the optical constants. Judd-Ofelt (JO) analysis was performed on the absorption bands of Sm3+ (4f5) and the three phenomenological parameters (omega 2, omega 4, and omega 6) were computed and then used to determine radiative properties such as the radiative transition probability (Ar), the fluorescent branching ratio (beta r), the stimulated emission cross-section (sigma e) and the radiative lifetime (tau rad). Photoluminescence (PL) spectrum showed the typical four transitions of Sm3+ at wavelengths of 564, 600, 645 and 703 nm corresponding to 4G5/2 -> 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The spectroscopic quality factors omega 4/omega 6, the predicted lifetime (tau rad) calculated using the JO method and the experimentally lifetime (tau exp) for the 4G5/2level were calculated and discussed. The glass color purity is as high as 98%, which makes it a potential candidate for laser emission.

In the present study, we report the development and characterization of composite layers (by spin coating) based on magnesium-doped hydroxyapatite in a chitosan matrix, containing human osteosarcoma MG63 cells anchored. Studies regarding the biocompatibility of the composite layers were performed with the aid of a MTT (3-4,5-Dimethylthiazol 2,5-diphenyltetrazolium bromide) assay. The data determined that the composite layers did not inhibit the growth and adhesion of MG63 cells to their surfaces exhibiting good biocompatibility properties. Furthermore, the attachment and development of MG63 cells on the surface of MgHApCh composite layers were investigated using atomic force microscopy (AFM). AFM topographical maps emphasized that the HApCh and 8MgHApCh composite layers surface promoted the attachment and proliferation of MG63 cells on their surface. Meanwhile, in the case of 30MgHApCh layers incubated for 48 h, a slight modification of the morphological features of the MG63 cells. In addition, the effects of the composite layers against Candida albicans ATCC 10231 were also evaluated. The data results from the in vitro antifungal assay depicted that the composite layers successfully inhibited the growth of the fungal cells onto their surface. Morphological and fractal analyses unveil cancer cell surfaces on Mg-containing composite layers with intricate 3D patterns, driven by highfrequency components. Their remarkable complexity and roughness arises from a strong multifractal nature, supporting more effective vertical growth compared to Si and HApCh surfaces. The cell viability reduced of uncoated Si surface is highlighted by its less intense 3D pattern growth. Our results show that the uncoated Si surface promotes lower viability of MG63 cancer cells, with less rough and complex 3D spatial patterns.