Johny Neamtu
University of Medicine and Pharmacy of Craiova
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Featured researches published by Johny Neamtu.
Journal of Biomedical Materials Research Part A | 2010
Livia E. Sima; George E. Stan; Constantin O. Morosanu; Alina Melinescu; Adelina Ianculescu; Razvan Melinte; Johny Neamtu; Stefana M. Petrescu
In this work, an improved version of the radio frequency magnetron sputtering (RF-MS) technique was used to prepare highly adherent B-type carbonated hydroxylapatite (B-CHA) thin films. Fourier transform infrared spectroscopy (FTIR) and grazing incidence X-ray diffraction studies proved that the coatings maintained the composition and revealed the polycrystalline structure of HA. Scanning electron microscopy analysis showed that the CHA films are rough and exhibit a homogeneous microstructure. Energy-dispersive X-ray spectroscopy (EDX) mapping demonstrated a uniform distribution of the Ca and P cations while a Ca/P ratio of 1.8 was found. In addition, the FTIR experiments showed a remarkable reproducibility of the nanostructures. Human mesenchymal stem cells (hMSCs), in vitro differentiated osteoblasts, and explanted bone cells were grown over the surface of CHA coatings for periods between a few hours and 21 days. Osteoprogenitor cells maintained viability and characteristic morphology after adhesion on CHA coatings. Ki67-positive osteoblasts were the evidence of cell proliferation events. Cells showed positive staining for markers of osteoblast phenotype such as collagen type I, bone sialoprotein and osteonectin. Our data showed the formation of mineralized foci by differentiation of hMSCs to human primary osteoblasts after cultivation in osteogenic media on RF-sputtered films. The results demonstrate the capacity of B-type CHA coating to support MSCs adhesion and osteogenic differentiation ability.
Journal of Applied Physics | 1999
Johny Neamtu; I.N. Mihailescu; C. Ristoscu; J. Hermann
We present an analysis describing the phenomena that are involved in the interaction process between high intensity UV laser radiation and a solid target in a low-pressure gas environment. The laser action upon the solid surface is described by solving the one-dimensional (1D) heat-conduction equation. The 1D hydrodynamic model is further applied to describe the interaction between laser radiation and the plasma expanding in front of the target. The laser radiation absorption in the vapor plasma is considered using a multicomponent fluid model. The transit of ablated material from target to collector is treated by a Monte Carlo method. The time and space distributions of the main plasma parameters (e.g., atom density and plasma electron temperature and density) are calculated. Finally, the thickness profile of a film deposited on a collector parallel to the target is predicted. For comparison with available experimental data, the calculations were carried out for the case of a Ti target submitted to a mul...
Journal of Materials Science: Materials in Medicine | 2009
Livia E. Sima; A. Filimon; R. M. Piticescu; Gabrielle Charlotte Chitanu; D. M. Suflet; Marimona Miroiu; G. Socol; I.N. Mihailescu; Johny Neamtu; Gabriela Negroiu
The nanohybrid structures consisting of hydroxyapatite (HA) and sodium maleate-vinyl acetate copolymer (MP) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique on Ti surfaces were investigated for specific biological qualities required in bone implantology. The data from in vitro studies demonstrated that human primary osteoblasts (OBs) firmly adhered to Ti coated with HA–MP as indicated by cytoskeleton and vinculin dynamics. OBs spread onto biomaterial surface and formed groups of cells which during their biosynthetic activity expressed OB phenotype specific markers (collagen and non-collagenous proteins) and underwent controlled proliferation.
Journal of Thermal Analysis and Calorimetry | 2017
Johny Neamtu; Maria Viorica Bubulica; Andrei Rotaru; Catalin Ducu; Oana Elena Balosache; Valentin Costel Manda; Adina Turcu-Stiolica; Claudiu Nicolicescu; Razvan Melinte; Mariana Popescu; Octavian Croitoru
In this study, hydroxyapatite–alendronate composites were synthesized from calcium nitrate, diammonium hydrogen phosphate and alendronate by chemical precipitation method. The obtained materials were analysed by physical–chemical methods, while the compositional and structural characteristics of hydroxyapatite–alendronate phases were determined by a combination of crystallographic, spectroscopic and thermal analysis investigations; moreover, the alendronate content, its maximal incorporation efficiency to hydroxyapatite and stability were determined. A two-level full factorial design was chosen to determine the optimum set of process parameters (synthesis temperature, reactant addition rate and ripening time) and their effects on various hydroxyapatite–alendronate characteristics: alendronate incorporation efficiency, hydroxyapatite crystallite size (XRD), hydroxyapatite particle size distribution (DLS). These effects were quantified using design of experiments. The in vitro release profile of alendronate from hydroxyapatite–alendronate tablets was assessed.
Analytical Sciences | 2017
Andrei Bita; George Dan Mogoşanu; Ludovic Everard Bejenaru; Carmen Nicoleta Oancea; Cornelia Bejenaru; Octavian Croitoru; Gabriela Rau; Johny Neamtu; Iulia Daria Scorei; Ion Romulus Scorei; John M. Hunter; Brad Evers; Boris Nemzer; Florin Anghelina; Otilia-Constantina Rogoveanu
The paper describes a new, simple, selective and precise high-performance thin-layer chromatographic (HPTLC) method for the simultaneous identification and quantitative determination of boric acid (BA) and calcium fructoborate (CFB) in bulk and tablet/capsule dosage forms of dietary supplements. HPTLC silica gel G 60 F254 precoated glass plates were used as the stationary phase. The mobile phase consisted of 2-propanol-water 8:2 (v/v). The two boron-based compounds were adequately separated with the Rf values of 0.83 ± 0.01 (BA) and 0.59 ± 0.01 (CFB).
Acta Pharmaceutica | 2018
Maria-Viorica Ciocilteu; Andreea Gabriela Mocanu; Adriana Mocanu; Catalin Ducu; Oana Elena Nicolaescu; Valentin Costel Manda; Adina Turcu-Stiolica; Claudiu Nicolicescu; Razvan Melinte; Maria Balasoiu; Octavian Croitoru; Johny Neamtu
Abstract The main objective of this study was to synthesize hydroxyapatite-ciprofloxacin composites using a chemical precipitation method and to evaluate the properties and in vitro release profile of the drug from the hydroxyapatite-ciprofloxacin composites. Composite characterization was achieved by FT-IR, XRD and DLS. Ciprofloxacin determination was accomplished by HPLC, resulting in good incorporation efficiency of the drug (18.13 %). The in vitro release study (Higuchi model C = K t1/2 and Ritger-Peppas model, C = K t0.6) showed a diffusion-controlled mechanism. The antibacterial activity showed that the bacterial growth inhibition zones were approximately equal for the synthesis composites and for the mechanical mixture on the Staphylococcus aureus germ. The use of hydroxyapatite, which is a biocompatible, bioactive and osteoconductive material, with ciprofloxacin, which has good antibacterial activity in this composite, makes it suitable for the development of bone grafts. Furthermore, the synthesis process allows a slow local release of the drug.
ALT'02 International Conference on Advanced Laser Technologies | 2003
Rodica Cristescu; G. Socol; I.N. Mihailescu; I. Morjan; Iulia Soare; Mihai Popescu; F. Sava; I. Stamatin; A. Andrei; Johny Neamtu
We report the obtaining of thin organic films based on poly(methyl methacrylate) polymer by Pulsed Laser Deposition on silicon substrates and quartz slides. The films were characterized by complementary techniques: x-ray Diffraction, x-ray Photoelectron Spectroscopy, Atomic Force Microscopy, Optical Microscopy, Raman Spectroscopy and Fourier Transform Infrared Spectroscopy. The obtained structures are amorphous. The film composition and structure depend on both the laser fluence as well as on the temperature of the substrate during deposition. We put in evidence in freshly deposited films the presence of diamond-like carbon while its amount strongly increases by annealing at ~400°C in Argon atmosphere.
ROMOPTO 2000: Sixth Conference on Optics | 2001
Johny Neamtu; I.N. Mihailescu
We report a theoretical study of the integration between UV laser pulse and the plasma expanding in front of the target. For description of the laser-plasma interaction process we used the gasdynamic approach. The plasma is assumed to be an electrically neutral gas, which contains neutral atoms, ions, and electrons in Local Thermodynamic Equilibrium (LTE). For study this interaction we used an Coupled Euler Lagrange numerical code. In addition it was possible to investigate the mechanism of plasma absorptivity and also calculating the laser energy which is effectively transmitted to the target.
ROMOPTO 2000: Sixth Conference on Optics | 2001
Johny Neamtu; I.N. Mihailescu; C. Ristoscu
We made a Monte Carlo simulation of the elastic interaction of ablated atoms with ambient gas molecules. Varying the initial energy of ablated atoms, the simulations were performed for different values of the ambient gas pressure in the range of 0.1-100 Pa and/or for values of target collector distance between 3-7 cm. The results concern the Ti ablated atoms transit in methane. Calculating the energy of the atoms when they reach the collector we determine the condition for plume splitting occurrence.
11th International School on Quantum Electronics: Laser Physics and Applications | 2001
Johny Neamtu; C. Ristoscu; I.N. Mihailescu
We report a theoretical and experimental comprehensive study of the synthesis of TiN by RPLD from Ti targets in (0.2 - 50) Pa nitrogen. We used an UV XeCl* excimer laser source ((lambda) equals 308 nm, (tau) FWHM<EQ 30 ns). The deposited structures were characterized by electron microscopy, XPS and RBS. We observed a tight interval of the ambient gas pressure of (0.7 - 7) Pa within we deposited stoichiometric, polycrystalline TiN films. The theoretical analysis was performed with a numerical multifluid code using the 1D heat- conduction equation. The transit of the ablated material from target to collector was treated by a Monte-Carlo method. Finally, the thickness profile of the deposited films was predicted. The obtained results are in good accordance with experimental measurements.