Stefan Ioan Voicu

Recent advances in cellulose and chitosan based membranes for water purification: A concise review

Recently membrane technology has emerged as a new promising and pervasive technology due to its innate advantages over traditional technologies such as adsorption, distillation and extraction. In this article, some of the recent advances in developing polymeric composite membrane materials for water purification from natural polysaccharide based polymers namely cellulose derivatives and chitosan are concisely reviewed. The impact of human social, demographic and industrial evolution along with expansion through environment has significantly affected the quality of water by pollution with large quantities of pesticides, minerals, drugs or other residues. At the forefront of decontamination and purification techniques, we found the membrane materials from polymers as a potential alternative. In an attempt to reduce the number of technical polymers widely used in the preparation of membranes, many researchers have reported new solutions for desalination or retention of organic yeasts, based on bio renewable polymers like cellulose derivatives and chitosan. These realizations are presented and discussed in terms of the most important parameters of membrane separation especially water flux and retention in this article.

Characterization and In Vitro and In Vivo Assessment of a Novel Cellulose Acetate-Coated Mg-Based Alloy for Orthopedic Applications

Despite their good biocompatibility and adequate mechanical behavior, the main limitation of Mg alloys might be their high degradation rates in a physiological environment. In this study, a novel Mg-based alloy exhibiting an elastic modulus E = 42 GPa, Mg-1Ca-0.2Mn-0.6Zr, was synthesized and thermo-mechanically processed. In order to improve its performance as a temporary bone implant, a coating based on cellulose acetate (CA) was realized by using the dipping method. The formation of the polymer coating was demonstrated by FT-IR, XPS, SEM and corrosion behavior comparative analyses of both uncoated and CA-coated alloys. The potentiodynamic polarization test revealed that the CA coating significantly improved the corrosion resistance of the Mg alloy. Using a series of in vitro and in vivo experiments, the biocompatibility of both groups of biomaterials was assessed. In vitro experiments demonstrated that the media containing their extracts showed good cytocompatibility on MC3T3-E1 pre-osteoblasts in terms of cell adhesion and spreading, viability, proliferation and osteogenic differentiation. In vivo studies conducted in rats revealed that the intramedullary coated implant for fixation of femur fracture was more efficient in inducing bone regeneration than the uncoated one. In this manner, the present study suggests that the CA-coated Mg-based alloy holds promise for orthopedic aplications.

Effect of micron sized silver particles concentration on the adhesion induced by sintering and antibacterial properties of hydroxyapatite microcomposites

Abstract In this paper, silver microparticles were proposed as an additive (wetting agent) in the sintering of bovine bone-derived hydroxyapatite, and their well-known antibacterial properties were evaluated for the newly-developed materials. Hydroxyapatite was prepared by thermal processing of bovine bones, followed by milling and sorting. After silver addition, the samples were tested as precursors, green compacts and adhered particles-sintered compacts, using complementary morphological, compositional and structural evaluation techniques (scanning electron microscopy coupled with energy dispersive spectrometry, Fourier infrared spectroscopy, X-ray diffraction). The antibacterial effect was assessed on bacterial strains popular for their association with post-implantation infections. The study was designed to evaluate the precursors, investigate the surface, morphology and/or structure changes during forming and adhesion by sintering, and explore the relationship between the silver concentration and the antibacterial effect of the material. The results confirmed the benefits of adding silver as a wetting agent in sintering bovine bone-derived hydroxyapatite as well as its antibacterial effect (with best results at 2 wt%Ag). In spite of the great potential as a wetting agent and antibacterial factor in hydroxyapatite, the proper evaluation of these results requires extensive testing for elevating the control level in designing the material properties, and for establishing optimal concentrations of silver in order to achieve proper antibacterial and biocompatible behaviours.

Modification of titanium surface with collagen and doxycycline as a new approach in dental implants

In this work, we investigate for the first time several issues involved in bio-adhesion process for a new type of chemically modified titanium surfaces (in their initial form and after collagen deposition), in order to assess their potential in dental implant surface modification. For this purpose, we studied the following: collagen adhesion, cytotoxicity, osteoblast cytomorphology, cell adhesion and proliferation, doxycycline embedding and modifications in the collagen film deposed on the metal surfaces, drug release from the collagen films. The improvement of adhesion between collagen film and titanium substrate, when hydroxyl and amino functional groups are assisting the surfaces was presented, all materials showing no cytotoxic effects as revealed by lactate dehydrogenase-based assay. The drug release from titanium–coll–doxy systems offers a dual mechanism of the delivery profile (burst release followed by moderate discharge of the antibiotic), with perspectives in soft tissue recovery postoperative stage.

Polysulfone- doped polyaniline composite membranes. synthesis and electrochemical characteristics

In order to combine the advantages of polysulfone (PSf) as a membrane material to that of polyaniline as a conductive polymer, one has attempted to obtain novel polysulfone-polyaniline composite membranes by a newly improved technique comparing to the existing ones. The strong point of this technique consists in a phase inversion by immersion precipitation accompanying by chemical reaction followed by the activation of polyaniline with sulfonated beta-cyclodextrine. The above synthesized membranes were structurally characterized using Scanning Electron Microscopy, FT-IR spectroscopy, thermal analysis. The ionic conductivity and electrochemical characteristics were also determined by Electrochemical Impedance Spectroscopy.

Synergistic effect of carbon nanotubes and graphene for high performance cellulose acetate membranes in biomedical applications

Comparative evaluation of innovative combinations of three types of carbon nanomaterial (CNM) highlighted membranes with important potential for biomedical applications. Non-solvent induced phase separation coupled with ultrasound technique was used to generate membranes comprised of (i) cellulose acetate/ammonia functionalized carbon nanotubes (CA/CNT), (ii) cellulose acetate/ammonia functionalized graphene oxide (CA/GO), and (iii) cellulose acetate/CNT-GO. Structural, topographical and thermal features as well as water and ethanol permeation, bovine serum albumin (BSA) and haemoglobin (Hb) rejection were evaluated. Biocompatibility in terms of cytotoxicity, cell proliferation and adhesion were explored using a 3T3E1 cell line. The formation of amorphous structures, within which the CNMs were well dispersed, facilitated the development of smoother topographies. Addition of CNMs generated morphological changes influencing a decrease in water and ethanol fluxes. Furthermore, CNMs concentrated within the membrane skin layer exhibited repellent effects against BSA and Hb molecules and excellent cytocompatibility.

Cellulose Derivatives Based Membranes for Biomedical Applications

This paper presents a comparative study of cellulose acetate membranes, respectively nitrocellulose membranes, synthesized under the same conditions for the retention of proteins from aqueous solutions. It has also been studied the hydrodynamic behavior of the membranes, measuring water, respectively ethanol flow rates, and the retention of proteins. The membranes have been characterized by scanning electron microscopy in order to study the morphological differences.

Production and characterization of cellulose acetate – titanium dioxide nanotubes membrane fraxiparinized through polydopamine for clinical applications

The present paper introduces a study on the preparation and characterization of cellulose acetate - TiO2 nanotubes membrane. In order to be used as a hemodialysis membrane, fraxiparinized nanotubes have been incorporated into the cellulose matrix. Fraxiparine embedding was performed via strong binding ability of dopamine. Composite membrane was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. Electrochemical impedance spectroscopy was used to correlate the morphology of composite membrane with its electrochemical properties. Mott-Schottky test proved titanium dioxide semiconductor incorporation in composite membrane. Permeation test was made to determine pure water flux. The obtained results showed that addition of nanotubes had a positive impact on membrane permeation compared with a control polymeric membrane.

The Influence of Filler in Composite Cellulose Acetate Membranes for Proteins Recovery

The present work study the influence of filler in proteins recovery using cellulose acetate membranes. There were studied carbon nanotubes and graphene oxide as synthetic fillers and bone powder and inulin as natural fillers. The used proteins for work were Bovine Serum Albumin and hemoglobin. The best retention results were shown by the composite membranes with carbon nanowalls, fact that can be explained by the chemical interactions between carbon nanotubes surface and proteins molecules. Synthesized membranes were characterized by Scanning Electron Microscopy and Fourrier Transformed infrared Spectroscopy and the proteins retention was determined by UV-Vis Spectroscopy.

Collagen-Niflumic Acid Spongious Matrices for Bone Repairing

Collagen is one of the most used biomaterials for bone defects repair, proving good results in tissue reconstruction research, and also its features recommend it as a very attractive drug delivery scaffold for local treatment of the affected osseous tissue. The inflammatory response is a common reaction that occurs in bone disease, the topical administration of anti-inflammatory drugs (NSAIDs) representing a reliable strategy to overcome this issue. The purpose of this paper was the physical-chemical and biopharmaceutical evaluation of some spongious matrices consisting of collagen as release support and niflumic acid as drug NSAID model, usable in bone tissue regeneration. Type I fibrillar collagen gel (2.4% w/w, 3.5 pH) was extracted from calf hide by the technology currently used in Collagen Department of Division Leather and Footwear Research Institute. The collagen sponges were obtained by freeze-drying of gels adjusted at 1% and 7.3 pH, with different dextran (0; 10 and 20%) and MgO (0; 30 and 60%) concentrations (reported to dry collagen), with 0.5% and without niflumic acid (NA) (reported to gel) and the same amount of glutaraldehyde (0.5% reported to collagen dry substance). The sponges were evaluated through water absorption, FT-IR spectroscopy and optical microscopy. In vitro NA release from the designed sponges was carried out using a sandwich device adapted to a dissolution equipment. Power law kinetic model was applied to explain drug release from the tested formulations. The NA release from collagen sponges showed a non-Fickian transport mechanism. The addition in different concentrations of dextran and MgO leads to more compact structures and improves stability of collagenic matrices. Our results showed that the designed support could be adequate for treating the inflammation associated with a bone defect in orthopedic surgery.