Raluca Petronela Dumitriu

Hybrid Nanostructures Containing Sulfadiazine Modified Chitosan as Antimicrobial Drug Carriers

Chitosan (CH) nanofibrous structures containing sulfadiazine (SDZ) or sulfadiazine modified chitosan (SCH) in the form of functional nanoparticles attached to nanofibers (hybrid nanostructures) were obtained by mono-axial and coaxial electrospinning. The mono-axial design consisted of a SDZ/CH mixture solution fed through a single nozzle while the coaxial design consisted of SCH and CH solutions separately supplied to the inner and outer nozzle (or in reverse order). The CH ability to form nanofibers assured the formation of a nanofiber mesh, while SDZ and SCH, both in form of suspensions in the electrospun solution, assured the formation of active nanoparticles which remained attached to the CH nanofiber mesh after the electrospinning process. The obtained nanostructures were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SDZ release profiles and kinetics were analyzed. The SDZ or SCH nanoparticles loosely attached at the surface of the nanofibers, provide a burst release in the first 20 min, which is important to stop the possible initial infection in a wound, while the SDZ and SCH from the nanoparticles which are better confined (or even encapsulated) into the CH nanofibers would be slowly released with the erosion/disruption of the CH nanofiber mesh.

Polyurethane-extracellular matrix/silver bionanocomposites for urinary catheters

Polyurethane–extracellular matrix membranes with bionanocomposites or coatings containing a small amount of biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, and silver were obtained by solvent casting or electrospinning/electrospraying of the polyurethane–extracellular matrix–Ag formulations onto pure polyurethane membrane in order to achieve improved antibacterial biomaterials for urinary catheters. Using Fourier transform infrared spectroscopy, the interaction of the incorporated silver nanoparticles with polyurethane–extracellular matrix was found, while X-ray photoelectron spectroscopy and X-ray diffraction analyses ws used to determine the presence of metallic Ag for polyurethane membrane and Ag only in oxidized state for polyurethane–extracellular matrix membranes due to the stabilizing effect of polymeric components. The in vitro antimicrobial tests against Escherichia coli, Salmonella typhymurium, and Listeria monocytogenes were used for the evaluation of the antimicrobial efficiency.

Kinetics of Swelling and Drug Release from PNIPAAm/Alginate Stimuli Responsive Hydrogels

Stimuli responsive hydrogels are very attractive for applications in sustained and/or targeted drug delivery systems. As the release of drugs is related to the swelling behavior of hydrogels, the swelling kinetic studies become of great importance to appreciate the release kinetics from hydrogel matrices. Hydrogels with high performance properties have been prepared from N-isopropylacryl amide (NIPAAm) and sodium alginate, crosslinked with N,N`-methylene-bis-(acrylamide) (MBAAm). This study is focused on the investigation of swelling and drug release kinetics, coupled by morphological studies. The kinetic parameters of the swelling at different temperatures for hydrogels samples have been evaluated and confirmed their temperature-responsive behavior. The swelling rate constant (ksw) decreases of with increasing temperature and slight increases with the alginate content in the samples. The drug release kinetic study from the prepared hydrogel matrices was performed in twice-distilled water and ethanol for bioactive agents as vanillin and ketoprofen, respectively. An increase of alginate content results in a slower rate and smaller percentage of vanillin and ketoprofen released. It has been established that the ketoprofen occurs according with case II of transport and vanillin release behavior occurs by an anomalous transport mechanism. The values of the release rate constant (kr) decreased by increasing swelling degree in case of 75/25 NIPAAm/alginate hydrogels and decreased also by increasing content of alginate in hydrogels with various compositions. Morphological studies performed by environmental scanning electron microscopy (ESEM) evidenced a relaxed network at high relative humidity, which explain both swelling and release profiles.

Sulfadiazine—Chitosan Conjugates and Their Polyelectrolyte Complexes with Hyaluronate Destined to the Management of Burn Wounds

In the present study polyelectrolyte complexes (PECs) based on new sulfadiazine-chitosan conjugates with sodium hyaluronate have been developed with potential use in treatment of burn wounds. The PECs were chemically characterized using Fourier Transform—Infrared Spectroscopy, Scanning Electon Microscopy and Near Infrared Chemical Imaging Technique. The swelling behavior and in vitro sulfadiazine release were also investigated. The antimicrobial activity was evaluated towards three bacterial strains: Escherichia coli, Listeria monocytogenes and Salmonella thyphymurium. The developed PECs demonstrated their antimicrobial efficiency against tested bacterial strains, the PECs containing sulfadiazine-modified chitosan being more active than PECs containing unmodified chitosan.

Biocompatible and Biodegradable Chitosan / Clay Nanocomposites as New Carriers for Theophylline Controlled Release

Aims: Carrier polymeric materials based on chitosan and chitosan / montmorillonite crosslinked with glutaraldehyde were prepared and studied for their biocompatibility, nontoxicity, and biod egradability aiming their application in drug delivery. Study Design: Polymeric materials based on chitosan and chitosan/ montmorillonite crosslinked with glutaraldehyde were prepared as new carriers for theophylline release. Methodology: The matrices of c hitosan / glutaraldehyde and chitosan / montmorillonite / Original Research Article

Evaluation of the Rosemary Extract Effect on the Properties of Polylactic Acid-Based Materials

New multifunctional materials containing additives derived from natural resources as powdered rosemary ethanolic extract were obtained by melt mixing and processed in good conditions without degradation and loss of additives. Incorporation of powdered rosemary ethanolic extract (R) into poly(lactic acid) (PLA) improved elongation at break, rheological properties, antibacterial and antioxidant activities, in addition to the biocompatibility. The good accordance between results of the chemiluminescence method and radical scavenging activity determination by chemical method evidenced the increased thermoxidative stability of the PLA biocomposites with respect to neat PLA, with R acting as an antioxidant. PLA/R biocomposites also showed low permeability to gases and migration rates of the bioactive compounds and could be considered as high-performance materials for food packaging. In vitro biocompatibility based on the determination of surface properties demonstrated a good hydrophilicity, better spreading and division of fibroblasts, and increased platelet cohesion. The implantation of PLA/R pellets, was proven to possess a good in vivo biocompatibility, and resulted in similar changes in blood parameters and biochemical responses with the control group, suggesting that these PLA-based materials demonstrate very desirable properties as potential biomaterials, useful in human medicine for tissue engineering, wound management, orthopedic devices, scaffolds, drug delivery systems, etc. Therefore, PLA/R-based materials show promising properties for applications both in food packaging and as bioactive biomaterials.

Stimuli Responsive Matrices for Medical Applications

Different types of stimuli responsive polymers that respond with a property change to a variation in the environmental conditions are an attractive class of materials for advanced applications in biomedical or pharmaceutical fields. Three types of responsive biocompatible and biodegradable polymer matrices are presented as potential biomaterials for medical application as carriers for various drugs and tissue engineering substitutes. Hybrid hydrogels based on collagen/ N-isopropyl acrylamide containing montmorillonite nanoparticles are promising materials for tissue engineering and also as carriers for norfloxacin, a chemotherapeutic antibacterial agent. Semi-interpenetrated hydrogels based either on substituted anhydride modified collagen and 2-hydroxyethyl methacrylate or on alginate and poly (N-isopropylacrylamide) were tested as matrices for the controlled delivery of bisoprolol fumarate, an antihypertensive drug and respectively of ketoprofen, a non-steroidal anti-inflammatory drug.