Antimicrobial chitosan foams with and without polyester blending as tissue engineering scaffolds

Due to its many interesting properties and its high availability at low costs from waste products (i.e. the shell of crustaceans), chitosan is the material of choice for many biomedical applications. In tissue engineering, specifically, chitosan is ideal due to its biocompatibility, intrinsic antimicrobial activity and ability of regulating the coagulation phenomena. However, a good material is not enough and the engineering of proper interconnected porosity is a key feature in the fabrication of scaffolds for tissue engineering applications. The morphology gives crucial stimuli, while the interconnectivity ensures the migration of cells and blood vessels in the inner districts of the scaffold. In this study we propose the development of chitosan foams with interconnected pores by the mean of freeze-drying. These foams are further modified by various routes in order to give them strong antibacterial capability without jeopardizing their cytocompatibility. The possibility of producing antibacterial foams by blending chitosan and polyesters will be presented. In-depth characterization is performed to investigate the morphological, physicochemical and biological properties of so produced scaffolds

Preparation and characterization of a glass matrix composite containing aluminium titanate particles with improved thermal shock resistance

Improving the thermal shock resistance of sintered glasses is an important task to broaden their technical and structural applications. In this study, the incorporation of second phase particles with low Young's modulus (E) into glass matrices to form composite materials is shown to be a convenient approach to increase their thermal shock resistance. Novel aluminosilicate glass matrix composites containing aluminium titanate (Al₂TiO₅) particles were fabricated by powder technology and pressureless sintering. By incorporating up to 30 vol.% of aluminium titanate particles a nearly fourfold increase of the thermal shock resistance was achieved. This was determined by measuring the critical temperature difference necessary to cause superficial cracks in cylindrical samples subjected to water-quench tests. The experimental results are shown to confirm qualitatively the theoretical prediction of the model of Hasselman et al. for the thermal shock resistance of low-E'/high-E composites

Viscous sintering of non-spherical borosilicate-glass powder

Densification by viscous flow - instead of diffusion - may be investigated by comparing densification rates and flow rates without the effect of external load, if possible. This is why the sintering of a borosilicate-glass powder was investigated using a hot-stage microscope. The samples sintered at 888 Κ showed shrinkage anisotropy, being the ratio of the axial to the radial shrinkage < 1. The flow rate varies linearly with the densification rate due to anisotropic densification; and the ratio between flow rate and densification rate may be altered by modifying the grade of anisotropy in densification. Scherer's theory has been used to compare experimental and theoretical values and the interdependence between densification rate and density. Deviations are discussed

Antibacterial biohybrid nanofibers for wound dressings

Globally, chronic wounds impose a notable burden to patients and healthcare systems. Such skin wounds are readily subjected to bacteria that provoke inflammation and hence challenge the healing process. Furthermore, bacteria induce infection impeding re-epithelialization and collagen synthesis. With an estimated global market of $20.4 billion by 2021, appropriate wound dressing materials e.g. those composed of biopolymers originating from nature, are capable of alleviating the infection incidence and of accelerating the healing process. Particularly, biopolymeric nanofibrous dressings are biocompatible and mostly biodegradable and biomimic the extracellular matrix structure. Such nanofibrous dressings provide a high surface area and the ability to deliver antibiotics and antibacterial agents locally into the wound milieu to control infection. In this regard, with the dangerous evolution of antibiotic resistant bacteria, antibiotic delivery systems are being gradually replaced with antibacterial biohybrid nanofibrous wound dressings. This emerging class of wound dressings comprises biopolymeric nanofibers containing antibacterial nanoparticles, nature-derived compounds and biofunctional agents. Here, the most recent (since 2015) developments of antibacterial biopolymeric nanofibrous wound dressings, particularly those made of biohybrids, are reviewed and their antibacterial efficiency is evaluated based on a comprehensive literature analysis. Lastly, the prospects and challenges are discussed to draw a roadmap for further progresses and to open up future research avenues in this area. Statement of Significance: With a global market of$20.4 billion by 2021, skin wound dressings are a crucial segment of the wound care industry. As an advanced class of bioactive wound dressing materials, natural polymeric nanofibers loaded with antibacterial agents, e.g. antimicrobial nanoparticles/ions, nature-derived compounds and biofunctional agents, have shown a remarkable potential for replacement of their classic counterparts. Also, given the expanding concern regarding antibiotic resistant bacteria, such biohybrid nanofibrous wound dressings can outperform classical drug delivery systems. Here, an updated overview of the most recent (since 2015) developments of antibacterial biopolymeric nanofibrous wound dressings is presented. In this review, while discussing about the antibacterial efficiency of such systems, the prospects and challenges are highlighted to draw a roadmap for further progresses in this area.</p

Nature-Derived and Synthetic Additives to poly(ɛ-Caprolactone) Nanofibrous Systems for Biomedicine; an Updated Overview

As a low cost, biocompatible, and bioresorbable synthetic polymer, poly (ɛ-caprolactone) (PCL) is widely used for different biomedical applications including drug delivery, wound dressing, and tissue engineering. An extensive range of in vitro and in vivo tests has proven the favourable applicability of PCL in biomedicine, bringing about the FDA approval for a plethora of PCL made medical or drug delivery systems. This popular polymer, widely researched since the 1970s, can be readily processed through various techniques such as 3D printing and electrospinning to create biomimetic and customized medical products. However, low mechanical strength, insufficient number of cellular recognition sites, poor bioactivity, and hydrophobicity are main shortcomings of PCL limiting its broader use for biomedical applications. To maintain and benefit from the high potential of PCL, yet addressing its physicochemical and biological challenges, blending with nature-derived (bio)polymers and incorporation of nanofillers have been extensively investigated. Here, we discuss novel additives that have been meant for enhancement of PCL nanofiber properties and thus for further extension of the PCL nanofiber application domain. The most recent researches (since 2017) have been covered and an updated overview about hybrid PCL nanofibers is presented with focus on those including nature-derived additives, e.g., polysaccharides and proteins, and synthetic additives, e.g., inorganic and carbon nanomaterials

Carbon-fibre reinforced glass matrix composites: self-lubricating materials for wear applications in vacuum

The self-lubricating wear behaviour of a C-fibre reinforced borosilicate glass matrix composite in vacuum was investigated by using a rotating pump experimental facility. The vanes were made of the composite material and the stator of the pump was of cast iron. Glass composite wear was accompanied by material transfer onto the stator surface. The formation of isle-type and continuous graphitic films on the counter-body surface was observed. The continuous film provided adequate lubrication during friction, leading to a relatively low wear rate of the composite for the conditions investigated

A Structural Comparison of Ordered and Non-Ordered Ion Doped Silicate Bioactive Glasses

One of the key benefits of sol-gel-derived glasses is the presence of a mesoporous structure and the resulting increase in surface area. This enhancement in textural properties has a significant e ect on the physicochemical properties of the materials. In this context the aim of this study was to investigate how sol-gel synthesis parameters can influence the textural and structural properties of mesoporous silicate glasses. We report the synthesis and characterization of metal ion doped sol-gel derived glasses with di erent dopants in the presence or absence of a surfactant (Pluronic P123) used as structure-directing templating agent. Characterization was done by several methods. Using a structure directing agent led to larger surface areas and highly ordered mesoporous structures. The chemical structure of the non-ordered glasses was modified to a larger extent than the one of the ordered glasses due to increased incorporation of dopant ions into the glass network. The results will help to further understand how the properties of sol-gel glasses can be controlled by incorporation of metal dopants, in conjunction with control over the textural properties, and will be important to optimize the properties of sol-gel glasses for specific applications, e.g., drug delivery, bone regeneration, wound healing, and antibacterial materials.European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 643050, project “HyMedPoly

ELECTROPHORETIC DEPOSITION OF ZEIN/BIOGLASS COMPOSITES WITH INCORPORATION OF ESSENTIAL OILS

In this study, electrophoretic deposition of zein/Bioglass® on stainless steel electrodes was performed using ethanol /water as a solvent under direct current (DC) field. Z potential of the suspensions was measured at different pHs to define the stability of the suspension and the charge of the particles. Films were produced changing voltage and time of deposition. Due to the amphiphilic structure of zein, the β-sheets exhibits a positive charge which bond with the bioglass to form a composite. While the α-sheets leads the deposition process on the anode. Essential oils were added with the aim of enhance the antibacterial properties of the system. Surface morphology was studied using scanning electron microscopy. The amount of bioglass incorporated into the coating was measured using thermogravimetric analysis. The influence of the incorporation of essential oils was cheked with the antibacterial response using gram negative and gram positive bacteria’s. The results showed the influence of the pH in the charge of the particles. The porosity on the surface of the coatings was influenced with voltages higher than 5

Electrofabrication and Characterization of Multifunctional, Asymmetric Bilayer Films Based on Chitosan‐Gelatin and Mesoporous Bioactive Glass Nanoparticles for Guided Bone Regeneration

Please click Additional Files below to see the full abstract

MICROPOROUS ORGANIC-INORGANIC NANOCOMPOSITE COATING ON STAINLESS STEEL VIA EPD FOR BIOMEDICAL APPLICATIONS

Stainless steel implants generally have a bioinert surface which does not integrate with bone tissue easily and thus hinders the formation of permanent orthopedic implants. The present work aims to tackle this issue by coating stainless steel AISI 316L substrates with a microporous organic-inorganic nanocomposite (chitosan/gelatin/halloysite) which is bioactive. This composite coating has the capacity for enhancing the surface functionalisation and improving the biocompatibility and interaction with bone tissue. For fabricating the coating, chitosan (6.0 g/L) and gelatin (14.0 g/L) based suspensions were prepared and then dissolved in HCl solution (0.04 M); to this, varying amounts of nanotube halloysite (0.3-12.0 g/L) were added. A simple electrophoretic deposition (EPD) method was used at room temperature with low applied voltages (3-10 V) and short deposition times (1-5 min). Dense microporous coatings were fabricated and these were characterised using optical microscopy, field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Mechanical properties were determined by bending test. In vitro studies were performed in simulated body fluid (SBF) for 3 and 7 days in order to evaluate the formation of apatite on the coating surface. The microporous coating was found to increase in the extent of porosity with increase in the applied voltage owing to the occurrence of bubbles at the interface between the suspension and substrate. There was good adhesion between the coating and substrate for all halloysite contents for an applied voltage of 5 V. The microporous coating was also observed to be flexible since no fracture was observed even after the plate was bent until 180°. However, the coating thickness increased at the highest voltage (10 V) and this resulted in cracking during the bending test. Interestingly, the halloysite nanotubes were observed to have stimulated the growth of apatite after immersion in SBF solution. Furthermore, apatite growth was extensive with increase in the halloysite content. This occurrence is attributed to the presence of silane (Si-O-Si) groups on the surface of halloysite which contributed to apatite formation. The results show that the fabricated coating can enhance the bioactivity of stainless steel implant surfaces