Composite scaffold obtained by electro-hydrodynamic technique for infection prevention and treatment in bone repair

Bone infection is a devastating condition resulting from implant or orthopaedic surgery. Therapeutic strategies are extremely complicated and may result in serious side effects or disabilities. The development of enhanced 3D scaffolds, able to promote efficient bone regeneration, combined with targeted antibiotic release to prevent bacterial colonization, is a promising tool for the successful repair of bone defects. Herein, polymeric electrospun scaffolds composed of polycaprolactone (PCL) nanofibres decorated with poly(lactic-co-glycolic acid) (PLGA) particles loaded with rifampicin were fabricated to achieve local and sustained drug release for more efficient prevention and treatment of infection. The release profile showed an initial burst of rifampicin in the first six hours, enabling complete elimination of bacteria. Sustained and long-term release was observed until the end of the experiments (28 days), facilitating a prolonged effect on the inhibition of bacterial growth, which is in agreement with the common knowledge concerning the acidic degradation of the microparticles. In addition, bactericidal effects against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria were demonstrated at concentrations of released rifampicin up to 58 ppm after 24 h, with greater efficacy against S. aureus (13 ppm vs 58 ppm for E. coli). Cell morphology and cytocompatibility studies highlighted the suitability of the fabricated scaffolds to support cell growth, as well as their promising clinical application for bone regeneration combined with prevention or treatment of bacterial infection

Platinum substituted Cobalt(II, III) Oxide: Interplay of tetrahedral Co(II) sites towards electrochemical oxygen evolution activity

Substitution of ionic platinum is carried out in Co3O4 host synthesized by solution combustion strategy. These Pt substituted Co3O4 spinels characterized by XRD show pure crystalline phase of Co3O4 without any separated peaks related to Pt/PtOx. Electrochemical OER activities of these spinels are investigated by cyclic voltammetry, linear sweep voltammetry and chronoamperometry in neutral, alkaline and neutral buffer electrolytes. LSV studies on 1% Pt substituted Co3O4 exhibit a low overpotential (¿) of 455 mV at 20 mA cm-2 in KOH, as compared to PBS medium. Tafel slope value of 117 mV dec-1 in KOH represents one electron EC mechanism. The detailed XPS studies indicate that Pt doping increases the tetrahedral Co2+ sites of Co3O4. XPS studies before and after OER also infers that the mixed valence of Co in the host (Co3O4) undergoes redox (Co2+/Co3+) changes with simultaneous reduction in Pt dopant from Pt4+ to Pt2+ influencing the OER activity

Laser-treated electrospun fibers loaded with nano-hydroxyapatite for bone tissue engineering

Core-shell polycaprolactone/polycaprolactone (PCL/PCL) and polycaprolactone/polyvinyl acetate (PCL/PVAc) electrospun fibers loaded with synthesized nanohydroxyapatite (HAn) were lased treated to create microporosity. The prepared materials were characterized by XRD, FTIR, TEM and SEM. Uniform and randomly oriented beadless fibrous structures were obtained in all cases. Fibers diameters were in the 150–300 nm range. Needle-like HAn nanoparticles with mean diameters of 20 nm and length of approximately 150 nm were mostly encase inside the fibers. Laser treated materials present micropores with diameters in the range 70–120 µm for PCL-HAn/PCL fibers and in the 50–90 µm range for PCL-HAn/PVAC material. Only samples containing HAn presented bioactivity after incubation during 30 days in simulated body fluid. All scaffolds presented high viability, very low mortality, and human osteoblast proliferation. Biocompatibility was increased by laser treatment due to the surface and porosity modification

Evaluation of fatigue life of recycled opaque PET from household milk bottle wastes

Polyethylene terephthalate (PET) is among the most used thermoplastic polymers in large scale manufacturing. Opaque PET is increasingly used in milk bottles to save weight and to bring a glossy white aspect due to TiO2 nanoparticles. The recyclability of opaque PET is an issue: whereas the recycling channels are well established for transparent PET, the presence of opaque PET in household wastes weakens those channels: opaque bottles cannot be mixed with transparent ones because the resulting blend is not transparent anymore. Many research efforts focus on the possibility to turn opaque PET into resources, as one key to a more circular economy. A recent study has demonstrated the improvement of the mechanical properties of recycled PET through reactive extrusion. In the present work, the lifespan of recycled opaque PET has been evaluated throughout tensile–tensile fatigue loading cycles at various steps of the recycling process: The specimens are obtained from flakes after grinding PET wastes (F-r-OPET), from a subsequent homogenization step (r-OPET-hom) and after reactive extrusion (Rex-r-OPET). Virgin PET is also considered as a comparison. First, tensile tests monitored by digital image correlation have been carried out to obtain the elastic modulus and ultimate tensile stress of each type of PET. The fatigue properties of reactive REx-r-OPET increase, probably associated with the rise of cross-linking and branching rates. The fatigue lifespan increases with the macromolecular weight. The fracture surface analysis of specimens brings new insight regarding the factors governing the fatigue behavior and the damaging mode of recycled PET. TiO2 nanoparticles act as stress concentrators, contributing to void formation at multiple sites and thus promoting the fracture process. Finally, the fatigue life of REx-r-OPET is comparable to those of virgin PET. Upcycling opaque PET by reactive extrusion may be a relevant new route to absorb some of the growing amounts of PET worldwide

Pt-CoOx nanoparticles supported on ETS-10 for preferential oxidation of CO reaction

In this paper we prepare bimetallic Pt-CoOx nanoparticles which are further supported in microporous titanosilicate ETS-10. This support has been previously demonstrated as a good candidate for this reaction in the presence of CO2 and H2O. The bimetallic nanoparticles and the supported catalysts containing different loadings of nanoparticles have been extensively characterized and tested in the PROX reaction. The characterization of the nanoparticles discarded the formation of a metallic alloy, although Co and Pt are intimately in contact in the nanoparticle as the HAADF-STEM images revealed. XPS confirmed that the calcined nanoparticles would consist of metallic platinum and cobalt and Pt oxides. The catalyst containing 1.4 wt.% of PtCo nanoparticles can achieve complete CO conversion in the temperature range 120–150 °C working at WHSV = 30 L h-1 g-1

Smart dressings based on nanostructured fibers containing natural origin antimicrobial, anti-inflammatory, and regenerative compounds

A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients’ quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds. In spite of all the efforts that have been made during the recent years towards the development of artificial wound dressings, none of the currently available options combine all the requirements necessary for quick and optimal cutaneous regeneration. Therefore, technological advances in the area of temporary and permanent smart dressings for wound care are required. The development of nanoscience and nanotechnology can improve the materials and designs used in topical wound care in order to efficiently release antimicrobial, anti-inflammatory and regenerative compounds speeding up the endogenous healing process. Nanostructured dressings can overcome the limitations of the current coverings and, separately, natural origin components can also overcome the drawbacks of current antibiotics and antiseptics (mainly cytotoxicity, antibiotic resistance, and allergies). The combination of natural origin components with demonstrated antibiotic, regenerative, or anti-inflammatory nanostructured materials is a promising approach to fulfil all the requirements needed for the next generation of bioactive wound dressings. Microbially compromised wounds have been treated with different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring antimicrobial, anti-inflammatory, and regenerative components but the available evidence is limited and insufficient to be able to draw reliable conclusions and to extrapolate those findings to the clinical practice. The evidence and some promising preliminary results indicate that future comparative studies are justified but instead of talking about the beneficial or inert effects of those natural origin occurring materials, the scientific community leads towards the identification of the main active components involved and their mechanism of action during the corresponding healing, antimicrobial, or regenerative processes and in carrying out systematic and comparative controlled tests. Once those natural origin components have been identified and their efficacy validated through solid clinical trials, their combination within nanostructured dressings can open up new avenues in the fabrication of bioactive dressings with outstanding characteristics for wound care. The motivation of this work is to analyze the state of the art in the use of different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring materials as antimicrobial, anti-inflammatory and regenerative components with the aim of clarifying their potential clinical use in bioactive dressings. We conclude that, for those natural occurring materials, more clinical trials are needed to reach a sufficient level of evidence as therapeutic agents for wound healing management.properties together wit

Electrospinning synthesis and characterization of nanofibers of Co, Ce and mixed Co-Ce oxides. Their application to oxidation reactions of diesel soot and CO

Co, Ce and Co-Ce nanofibers were synthesized by the electrospinning method. To obtain mixed fibers, Co was incorporated in two ways: one step synthesis and sequential synthesis. Nanofibers were applied to two reactions: gas-solid (CO oxidation) and solid-solid-gas (combustion of diesel soot). Different activity trends were observed in both reactions. For soot combustion, Co-Ce nanofibers were more active either than Co or Ce nanofibers. For CO oxidation instead, the activity order was Co > Co-Ce > Ce. Moreover, in the case of soot combustion, for all samples the temperature of maximum combustion rate occurred at a relatively narrow range (350-390 °C). On the contrary, for CO oxidation the temperature range for T50 was notably wider (150-325 °C). The high activity shown for all the samples for soot oxidation is related to the multiple contact points between the fibers and the soot particles, and the trend observed for CO oxidation related to the higher redox capacity of Co, as observed from CO-TPR experiments

Electrospun Au/CeO2 nanofibers: A highly accessible low-pressure drop catalyst for preferential CO oxidation

Au/CeO2 catalysts shaped as nanofibers were obtained by supporting Au nanoparticles (ca. 3 nm) on CeO2 nanofibers of around 200 nm diameter. The CeO2 support was prepared by calcining electrospun polymer nanocomposite fibers with a high Ce content; then gold nanoparticles were either synthesized in situ or deposited from a suspension. The prepared catalysts were used in the preferential oxidation of CO in a hydrogen-rich stream. The catalysts prepared by deposition of preformed gold nanoparticles were less stable and underwent sintering due to a weaker nanoparticle–support interaction. In contrast, the catalysts with Au nanoparticles synthesized in situ were active (90% conversion and 46% selectivity) and stable. The fiber-shaped catalyst was able to give maximum reactant access at a much lower pressure drop than catalyst in powder form

Production, characterization and testing of antibacterial PVA membranes loaded with HA-Ag3PO4 nanoparticles, produced by SC-CO2 phase inversion

BACKGROUND: Silver-loaded hydroxyapatite nanoparticles were incorporated into poly(vinyl alcohol) (PVA) membranes obtained by supercritical CO2 (SC-CO2) assisted phase inversion. Ag3PO4 crystals of 2.2 ± 0.6 nm were dispersed in synthesized needle-like hydroxyapatite nanoparticles (20 × 65 nm) and were uniformly deposited on the internal surfaces of the PVA membranes. Operative conditions to produce membranes by SC-CO2, PVA concentration and the effect on membrane porosity and morphology were studied. RESULTS: Solutions at 20% w/w PVA produced membranes with cellular morphology and nanoporous walls, whereas 30% and 50% w/w solutions produced nanostructured membranes. Silver ions were released from PVA membranes mainly by diffusion according to the Peppas–Sahlin model. Membranes obtained at 20% w/w PVA showed a significant E. coli inhibition at an Ag concentration of 9 ppm, reaching the minimal inhibitory concentration (MIC) and improving the bactericidal activity of the nanoparticles. CONCLUSION: A concentration of Ag3PO4 crystals of about 22 ppm was calculated as being capable of completely destroying these bacteria, reaching the minimum bactericidal concentration (MBC)