Polyethylene materials with multifunctional surface properties by electrospraying chitosan/vitamin E formulation destined to biomedical and food packaging applications

A dual-bioactive layer based on antimicrobial chitosan and antioxidant vitamin E was immobilized onto PE surface using electrospraying as coating technique. Covalent bonding of the antibacterial/antioxidant layer was achieved through amide bonds or carbamate linkage using both 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysuccinimide or carbonyldiimidazole coupling agents, respectively. The chitosan/vitamin E formulation was characterized by rheological measurements. The vitamin E addition in chitosan matrix leads to changes in chitosan rheological properties, such as viscosity decrease with increasing vitamin E content, change of the gel-like behavior to a fluid-like behavior, which further influences the electrospraying process and deposited coating morphology. The new stratified hybrid materials with improved properties have been characterized by different techniques as attenuated total reflectance-Fourier transform IR spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), polyelectrolyte and potentiometric titration, contact angle titration, scanning electron microscopy (SEM) and antibacterial and antioxidative tests. The electrosprayed bioactive coatings exhibit antibacterial, antioxidant and pH responsive activity. The pH responsiveness was evidenced by switching from hydrophilic to hydrophobic surface at pH ≈ 6. The chitosan/vitamin E modified PE substrate inhibited the growth for three different bacterial strains (Gram-negative and Gram-positive) and presented good antioxidative properties, acting as DPPH radical scavenging surfaces. Moreover, the new obtained materials present good stability and maintain their antioxidative capacity even after subjecting to desorption in harsh medium because of relative strong electrostatic and hydrogen bonds interactions between components of the formulation. The obtained materials can find application in food packaging or in medical field where synergistic action of these bioactive compounds is required.     

Investigation of Poly(vinyl alcohol)/Pluronic F127 Physical Gels

The application of Pluronic F127 as injectable gel-forming solution is limited by poor mechanical properties. The purpose of this study was to develop low viscosity formulations at ambient temperature that undergo a transition to gel under physiological conditions. Mixtures of Pluronic F127 and poly(vinyl alcohol) with different compositions were prepared in aqueous solutions and their in-situ gelation was investigated by dynamic light scattering and rheology. The results obtained for different formulations showed synergistic effects of polymer mixtures in aqueous media and their properties can be tuned by varying polymer concentration, system composition or changing temperature.     

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.     

In Vitro and Ectopic In Vivo Studies toward the Utilization of Rapidly Isolated Human Nasal Chondrocytes for Single-Stage Arthroscopic Cartilage Regeneration Therapy

Nasal chondrocytes (NCs) have a higher and more reproducible chondrogenic capacity than articular chondrocytes, and the engineered cartilage tissue they generate in vitro has been demonstrated to be safe in clinical applications. Here, we aimed at determining the feasibility for a single-stage application of NCs for cartilage regeneration under minimally invasive settings. In particular, we assessed whether NCs isolated using a short collagenase digestion protocol retain their potential to proliferate and chondro-differentiate within an injectable, swiftly cross-linked and matrix-metalloproteinase (MMP)-degradable polyethylene glycol (PEG) gel enriched with human platelet lysate (hPL). NC-hPL-PEG gels were additionally tested for their capacity to generate cartilage tissue in vivo and to integrate into cartilage/bone compartments of human osteochondral plugs upon ectopic subcutaneous implantation into nude mice. NCs isolated with a rapid protocol and embedded in PEG gels with hPL at low cell density were capable of efficiently proliferating and of generating tissue rich in glycosaminoglycans and collagen II. NC-hPL-PEG gels developed into hyaline-like cartilage tissues upon ectopic in vivo implantation and integrated with surrounding native cartilage and bone tissues. The delivery of NCs in PEG gels containing hPL is a feasible strategy for cartilage repair and now requires further validation in orthotopic in vivo models.     

Effect of storage conditions on lipid components and color of Mugil cephalus processed roes

The salted and semidried mullet (Mugil cephalus) ovary product (bottarga) is proposed as an important source of the long-chain n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid, and docosahexaenoic acid. In this work, we investigated the extent of lipid oxidation and browning of grated bottarga samples during 7 mo of storage at -20 °C, 2 to 3 °C in the absence of light, and at room temperature in the presence or absence of light. Modifications of the levels of total choline (as index of phospholipid breakdown), total sugars, and free amino acids such as lysine, methionine, and tryptophan (involved in nonenzymatic browning) were also studied at different storage conditions. Storage of bottarga did not significantly affect the n-3 PUFA and cholesterol levels with respect to the control; nevertheless, a significant hydroperoxide increase was observed during 7 mo in bottarga samples at all the storage conditions, while low malondialdeyde levels were measured. Samples placed at room temperature in the absence and in the presence of light showed over time a marked browning process, lipid breakdown, a sensible decrease in the levels of total sugars, tryptophan, and methionine with respect to control and samples stored at -20 °C and 2 to 3 °C. The resistance against the oxidation of the isolated bottarga lipids was also assessed in dry state at several temperatures (37, 75, and 140 °C). PRACTICAL APPLICATION: We evaluated the change in lipid compounds and color of dried and salted mullet roes under different storage conditions. The obtained results suggest the importance of the low temperatures to preserve the nutritional properties of this fish product during long storage.     

Hydrogen gas sensing properties of microwave-assisted 2D Hybrid Pd/rGO: Effect of temperature,humidity and UV illumination

A novel microwave assisted two-dimensional (2D) hybrid material based on nanostructured reduced graphene oxide (rGO) doped with Pd nanoparticles (Pd/rGO) has been synthesised to investigate its hydrogen sensing performance at different operational conditions. The sensing performance has been evaluated at various operating temperatures (room temperature up to 120 °C), hydrogen concentrations (up to 1%), and relative humidity (up to ~44%). The material characterization of the hybrid Pd/rGO analysed by different techniques which confirms homogeneous distribution of Pd NPs (<35 nm) on the multi-layered porous structure of the rGO nanosheets (NSs) and forming the hybrid Pd/rGO NSs. Moreover, the fundamental hydrogen sensing mechanism as well as recovery enhancement by ultraviolet (UV) light are investigated. This work offers an environmentally friendly and energy-saving synthesis approach for hydrogen sensing with excellent control over experimental parameters which can lead to fabrication of a highly selective and sensitive hydrogen sensor.     

The effects of organic additives on induction time and characteristics of precipitated calcium carbonate

The effects of an organic additive, polyoxyethylene sorbitan trioleate (Tween 85), on the induction time for the precipitation of calcium carbonate are experimentally and theoretically investigated. Calcium carbonate was precipitated from aqueous solutions of K₂CO₃ and Ca(NO)₃ at moderate supersaturations ranging between 5 and 16 with and without the organic additive. Experimentally it has been noticed that the induction period for CaCO₃ precipitation increases at low supersaturation and is also influenced by temperature. An increase of the induction time was noticed when Tween 85 was added in the system. The “cluster coagulation model” proposed by Qian and Botsaris (1997), which combines nucleation models and coagulation theory, was used to explain the effects of operating parameters on the induction time in terms of interfacial energy and cluster sizes.     

Rheological and thermal behaviour of poly(N‐isopropylacrylamide)/alginate smart polymeric networks

Interpenetrating polymeric networks based on sodium alginate and poly(N‐isopropylacrylamide) (PNIPAAm) covalently crosslinked with N,N′‐methylenebisacrylamide have been investigated using rheology, thermogravimetry, differential scanning calorimetry, X‐ray diffraction measurements and scanning electron microscopy (SEM). An improved elastic response of the samples with a higher PNIPAAm content and increased amount of crosslinking agent was found. The temperature‐responsive behaviour of the hydrogel samples was evidenced by viscoelastic measurements performed at various temperatures. It is shown that the properties of these gels can be tuned according to composition, amount of crosslinking agent and temperature changes. X‐ray scattering analysis revealed that the hydrophobic groups are locally segregated even in the swollen state whilst cryo‐SEM showed the highly heterogeneous nature of the gels. Copyright © 2011 Society of Chemical Industry     

BiFeO3-synthesis,characterization and its photocatalytic activity towards doxorubicin degradation from water

Pure bismuth ferrite was successfully obtained through the thermolysis of new bismuth ferrioxalate coordination compound, namely BiFe(C₂O₄)₃·3H₂O. The synthesized precursor was characterized by chemical analysis, infrared spectroscopy and thermal analysis. The bismuth ferrite obtained after a heating treatment of the precursor for at 450–800?°C/1?h was investigated by X-ray diffraction, FE-SEM, TEM and HRTEM. The obtained pure bismuth ferrite nanoparticles (480?°C) was tested as photocatalyst towards the degradation of doxorubicin (DOX), a well-known anti-cancer drug commonly used for the treatment of various cancer types, which has been detected in hospital effluent water. The comparative results of DOX degradation through photolysis and photocatalysis under UV irradiation showed a great photocatalytic activity of bismuth ferrite towards DOX degradation and mineralization from water. The kinetics aspects were discussed based on the first-order kinetics model that fitted the best the experimental photocatalysis results.