Preparation and Characterization of Chitosan-Gelatin/Glutaraldehyde Scaffolds

Chitosan-gelatin (CG) scaffolds were fabricated with glutaraldehyde as a cross-linker by vacuum freeze-drying. Mixtures of different volumes of chitosan and glutaraldehyde were considered. Morphology, porosity, density, and water absorbency of the scaffolds were studied. Both tensile and compressive properties of the scaffolds were tested. In addition, cellular adherence, proliferation, and morphology on the scaffolds were tested to evaluate the compatibility. It was found that porosity, density, water absorbency, and mechanical properties of CG scaffolds changed with the variation of chitosan or GA content. The adequate adherence, proliferation, and morphology of HaCaT type cells on the scaffolds showed that these scaffolds can be used as carriers for culturing HaCaT. The CG scaffolds, particularly those with chitosan-gelatin volume ratios of 1:1 and adding 6% or 8% volume of 0.25 wt% GA solution, were more suitable than the others through comparing the above properties and could be promising candidates for engineering skin tissue.     

Comparing the Effect of Sodium-Based and Calcium-Based Crosslinkers on the Swelling,Mechanical and Rheological Properties of Chitosan/Gelatin/Starch Films

Abstract

In this research chitosan/gelatin/starch films with a 47.5/47.5/5.0 (vol.%) composition were prepared by a solution casting method. To improve the mechanical and rheological properties of the chitosan-based films, two types of chemical crosslinkers, sodium triphosphate (STP) and calcium triphosphate (CTP), were used and the effects of these crosslinkers on the mechanical properties, swelling, water vapor transmission rate (WVTR) and the rheological-mechanical spectroscopy (RMS) of the films were investigated. For each crosslinker, two concentrations (0.05 and 0.1?wt% solutions) were used. The tensile test results showed that the samples with 0.05?wt% of STP or 0.1?wt% of CTP, had the best performance in enhancing the tensile strength and modulus of the films. The swelling tests indicated that 0.05?wt% of STP had the lowest swelling, and the performance with 0.1?wt% of CTP was also good. The results of the WVTR tests revealed that 0.05?wt% of STP and 0.1?wt% of CTP had the least and the most WVTR, respectively. Also, antibacterial tests were evaluated for the films based on an inhibition zone technique, and the results showed that the films containing the STP crosslinker has the best antibacterial activity. The RMS results indicated that the rheological properties of the films were enhanced by incorporating the crosslinkers, especially 0.1% concentration of CTP, into the film formulations.     

Antibacterial and Miscibility Properties of Chitosan/Collagen Blends

The miscibility, bioactivity, and antibacterial properties of chitosan/collagen specimens were systematically studied. The specimens were prepared by blending collagen and chitosan with varying deacetylation degrees in solutions; the collagen molecules had been extracted from pigskins using the acid swelling-pepsin digestion method. To understand the miscibility properties of collagen and chitosan molecules, the intrinsic viscosity and differential scanning calorimetry analysis of collagen, chitosan, and collagen/chitosan specimens were performed. The instrinsic viscosity measurements suggested that chitosan and collagen molecules with varying deacetylation degrees were miscible at molecular level for all compositions and degrees of deacetylation of chitosan/collagen mixture solutions prepared in this study. Fourier transform infrared analyses suggested that the percentage of preserved triple helix structures present in collagen molecules in collagen/chitosan specimens decreased with increasing chitosan contents, since the ratios of peak absorbance at 1239 cm^?1 of amide III and 1455 cm^?1 of C?H bending of collagen/chitosan specimens decreased significantly with increase in their chitosan contents. Abnormally high denaturation temperatures (T_d) were observed as the chitosan contents of collagen/chitosan specimens reached 40 wt%, at which T_d of collagen molecules was even higher than that of the corresponding pure chitosan molecules with varying deacetylation degrees. The antibacterial activity of collagen/chitosan blends increased consistently with increasing deacetylation degrees and concentrations of chitosan molecules in collagen/chitosan solutions. Possible explanations for these interesting thermal denaturation, antibacterial, and miscibility properties of chitosan/collagen specimens are reported.     

Poly (Vinyl Alcohol)/Chitosan/Akermanite Nanofibrous Scaffolds Prepared by Electrospinning

Abstract

Electrospinning, as an effective method for preparation of scaffolds for cell growth templates, has attracted great attention. In this study electrospinning was used to prepare poly (vinyl alcohol) (PVA)/chitosan scaffolds for bone tissue engineering. In order to improve the bioactivity and mechanical properties of the fibrous scaffolds, 0.5, 1 and 2?wt% akermanite, a calcium silicate based bioceramic, was added to the electrospinning solution. The morphology of the electrospun scaffolds was observed by using field emission-scanning electron microscopy and their mechanical strengths were analyzed by tension tests. The results showed that the formed scaffolds consisted of fibers with less than 100?nm diameter. In the case of the composite containing 1?wt% akermanite, the fibers were more homogeneous and no beads were formed during electrospinning, while in the composite containing 2?wt% akermanite a considerable number of beads were formed which we attribute to an improper viscosity of the electrospinning solution. Among the different compositions, the composite containing 1?wt% akermanite showed higher ultimate tensile strength (10.6?MPa) and fracture strain (9%). These values were increased by crosslinking the scaffold by reaction with glutaraldehyde, up to 13?MPa and 9.4%, respectively.     

Fabrication and characterization chitosan/functionalized zinc oxide bionanocomposites and study of their antibacterial activity

This study deals with preparation and evaluation of properties of chitosan/zinc oxide bionanocomposites (CT/ZnO BNCs) with different amounts of modified zinc oxide nanoparticles (ZnO NPs) through ultrasonic irradiation technique. Due to the high surface energy and tendency for agglomeration, the surface ZnO NPs was modified by a coupling agent as 3-aminopropyltriethoxysilane (APS) to form APS–ZnO nanoparticles. Fourier transform infrared (FTIR) spectroscopy confirmed that APS was successfully grafted onto the ZnO nanoparticles surface. Thermogravimetric analysis (TGA) revealed a surface coverage of the coupling molecule of 2.6 wt%. The resulting bionanocomposites were characterized by FTIR spectra, X-ray diffraction patterns, and TGA. The antibacterial activity of bionanocomposite films was tested against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The results of CT/ZnO BNCs revealed that the thermal and antibacterial properties obviously improved the presence of ZnO NPs in comparison with the pure CT and that this increase is higher when the NP content increases. Further, it was observed that antibacterial activity of the resulting hybrid biofilms showed somewhat higher for gram-positive bacteria compared to gram-negative bacteria.     

Chitosan Nanoparticles: Preparation and Application in Antibacterial Paper

Chitosan nanoparticles (CSNP) were obtained by H₂O₂ degradation of chitosan. Their morphology and size were determined by atomic force microscope (AFM), and the particles were found smooth and approximately 36 nm in size. CSNP-0.5% HAc solutions (1, 2, 5, and 10 mg/mL) were used in antibacterial paper by addition in pulp, impregnation, dispersion coating on the handsheets, and insufflation. The antibacterial activity of CSNP against Escherichia coli and Staphylococcus aureus was measured by the inhibition zone and bacterial reduction methods. Results showed that the antibacterial activity of CSNP was improved with the increase in concentration. For E. coli, at a CSNP concentration of 5 mg/mL, the antibacterial rate reached approximately 95%. However, for S. aureus, the antibacterial rate only reached 81%. In addition, the antibacterial activity of the antibacterial paper was determined by inhibition zone method. The paper prepared by insufflation had the greatest activity. For E. coli, at a CSNP concentration of 10 mg/mL, the inhibition zone reached 8.0 mm. For S. aureus, the inhibition zone was 6.8 mm.     

On the Effect of Nanosilver Reinforcement on the Mechanical,Physical, and Antimicrobial Properties of Polyethylene Blown Films

The simultaneous effect of silver nanoparticles on the antibacterial, mechanical, and physical properties of polyethylene (PE) films is evaluated. For this aim, uniaxial tensile, film rupture, and permeability tests and X-ray diffraction analysis were conducted. The biocidal performance against Escherichia coli and Staphylococcus aureus bacteria was also assessed. The results show that reinforcements with as little as 1 wt% nanosilver provided absolute antibacterial performance, while generally maintaining the mechanical properties. The reinforcement causes noticeable alterations in the crystallization behavior, which is manifested in the variations of gas permeability of the PE films.     

Biomimetic growth of gallic acid–ZnO hybrid assemblies and their applications

In this study, we probed the biomimetic formation of gallic acid (GA)–ZnO nanoparticle hybrids. It was found that the morphologies formed were dependent upon pH values, resulting in GA–ZnO hybrids of varying shapes such as micro or nanoplates or fibers. The formed supramolecular GA–ZnO hybrids were found to be luminescent as indicated by confocal microscopy and were utilized for the photocatalytic degradation of the organic dye methylene blue. We also explored the bactericidal effects of the hybrids on Staphylococcus aureus (S. aureus) as well as Escherichia Coli (E. Coli). Thus, we have developed a new class of shape-controlled nanohybrid assemblies via mild, green synthetic methods that may be utilized for photocatalytic degradation for environmental remediation as well as for antibacterial applications.     

Silver nanoparticle containing silk fibroin bionanotextiles

Development of new generation bionanotextiles is an important growing field, and they have found applications as wound dressings, bandages, tissue scaffolds, etc. In this study, silver nanoparticle (AgNP) containing silk-based bionanotextiles were fabricated by electrospinning, and processing parameters were optimized and discussed in detail. AgNPs were in situ synthesized within fibroin nanofibers by UV reduction of silver ions to metallic silver. The influence of post-treatments via methanol treatment and glutaraldehyde (GA) vapor exhibited changes in the secondary structure of silk. Methanol treatment increased the tensile properties of fibers due to supported crystalline silk structure, while GA vapor promoted amorphous secondary structure. AgNP containing silk fibroin bionanotextiles had strong antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa.     

Preparation and Characterization of Poly(L-lactide-co-glycolide-co-ε-caprolactone)/Nano-biaoactive Glass-Nano-β-tricalcium Phosphate Composite Scaffolds

Abstract

Polymeric/ceramic composite scaffolds that are biocompatible and biodegradable are widely used for tissue engineering applications. In this work a series of poly(L-lactide-co-glycolide-co-ε-caprolactone)/nano-biaoactive glass-nano-β-tricalcium phosphate composite scaffolds were successfully fabricated and the influences of the inorganic content and freezing temperature on the physical properties were studied. The composite scaffolds with various inorganic contents showed an interconnected pore structure with irregular shapes. The composite scaffolds had a porosity that was reduced with increasing inorganic content and decreasing freezing temperature. The incorporation of inorganic fillers and decreasing freezing temperature improved the mechanical properties of the hybrid scaffolds. By appropriate control of these two factors (10.0?wt% content of NBAG and β-TCP with freezing at ?30?°C) a suitable composite scaffold was prepared as a potential bone tissue engineering implant.     

Effect of an In-Situ Nucleating Agent on the Polymorphs and Mechanical Properties of Isotactic Polypropylene

The influence of glutaric acid (GA)/cadmium hydroxide [Cd(OH)₂] mixtures on the crystallization and properties of isotactic polypropylene (iPP) was investigated by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized light microscopy, and mechanical tests. It was found that the β-crystalline form was produced in the samples containing 0.15 wt% GA and more than 0.17 wt% Cd(OH)₂. The content of β-crystalline form was maximum, i.e. K_DSC = 65.4% and K_WAXD = 71.4%, when the sample was doped with GA (0.15 wt%)/Cd(OH)₂ (0.20 wt%) (the molar ratio of GA:Cd(OH)₂ was 1:1.2). It was also found that GA/Cd(OH)₂ mixtures not only induced the β-crystalline form but also made spherulites smaller. The results of mechanical tests showed that the toughness of iPP was greatly improved by bicomponent nucleator, while the stiffness decreased a little. Fourier transform infrared spectroscopy analysis indicated that an “in-situ” chemical reaction occurred between GA and Cd(OH)₂ during melt blending, yielding an effective β nucleator (cadmium glutarate).     

Influence of sintering temperature on properties of BNKLLT–6 wt% BCTZ binary lead-free piezoelectric ceramic prepared through the solid-state combustion technique

In this work, a new binary 94 wt%[Bi_0.5(Na_0.68K_0.22Li_0.1)_0.5TiO₃ + 0.10 wt% of La₂O₃]–6 wt% [(Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃] [BNKLLT–6 wt% BCTZ] ceramic was fabricated by the solid-state combustion technique and glycine was used as the fuel. The effect of sintering temperature in the range of 1075–1175 °C for 2 h on phase evolution, microstructure and electrical properties was investigated. The phase formation exhibited a coexistence structure between rhombohedral and tetragonal at low sintering temperature. As the sintering temperature increased, the phase formation changed to pseudo-cubic phase. The average grain size of the ceramics was increased with the increasing sintering temperature. Density, ?_r, ?_SA and T_FA of BNKLLT–6 wt% BCTZ ceramics increased while the T_SA decreased when the sintering temperature increased up to 1125 °C, while after this temperature the opposite trends occurred. At a sintering temperature of 1125 °C, the BNKLLT-6 wt% BCTZ sample showed the highest theoretical density (95.8%), maximum dielectric constant ?_SA (5278), highest d₃₃ (227 pC/N) and fair ferroelectric properties (P_r = 24.5 µC/cm² and E_c = 15.45 kV/cm).     

Photovoltaic activity in a ZnSe/PEO–chitosan blend electrolyte junction

Thin films of ZnSe and PEO–chitosan blend polymer doped with NH₄I and iodine crystals were prepared to form the two sides of a semiconductor electrolyte junction. ZnSe was electrodeposited on indium tin oxide (ITO) conducting glass. The polymer is a blend of 50 wt% chitosan and 50 wt% polyethylene oxide. The polymer blend was complexed with ammonium iodide (NH₄I), and some iodine crystals were added to the polymer–NH₄I solution to provide the I⁻/I³⁻redox couple. The room temperature ionic conductivity of the polymer electrolyte is 4.32 × 10⁻⁶ S/cm. The polymer film was sandwiched between the ZnSe semiconductor and an ITO glass to form a ZnSe/polymer electrolyte/ITO photovoltaic cell. The open circuit voltage (V _oc) of the fabricated cells ranges between 200 to 400 mV and the short circuit current between 7 to 10 μA.     

Structural and electronic properties of InNxP1-x alloy in full range (0 ≤ x ≤1)

We have performed first-principles method to investigate structural and electronic properties of InN_xP_1?x ternary semiconductor alloy in full range (0 ≤ x ≤ 1) using density functional theory. We have used modified Becke–Johnson potential to obtain accurate band gap results. From the electronic band structure calculation we have found that InN_xP_1?x become metal between 47 and 80% of nitrogen concentration. Additional to our band gap calculations, we have also used the band anticrossing model. The band anticrossing model supplies a simple, analytical expression to calculate the physical properties, such as the electronic and optical properties, of III-N_xV_1?x alloys. The knowledge of the electron density of states is required to understand and clarify some properties of materials such as the band structures, bonding character and dielectric function. In order to have a deeper understanding of these properties of the studied materials, the total and partial density of states has been calculated. Finally, we have calculated the total bowing parameter b of studied alloys, together with three contributions b_VD, b_CE, and b_SR due to volume deformation, different atomic electron negativities and structural relaxation, respectively.     

Novel ocotillol-derived lactone derivatives: design,synthesis, bioactive evaluation,SARs and preliminary antibacterial mechanism

A new series of ocotillol-derived lactone derivatives were designed and synthesized to consider their antibacterial activity, structure–activity relationships (SARs), antibacterial mechanism and in vivo antibacterial efficacy. Compound 6d, which exhibited broad antibacterial spectrum, was found to be the most active with minimum inhibitory concentrations (MICs) of 1–2 μg/mL against Gram-positive bacteria and 8–16 μg/mL against Gram-negative bacteria. The subsequent synergistic antibacterial tests displayed that 6d had the ability to improve the susceptibility of MRSA USA300, B. subtilis 168, and E. coli DH5α to kanamycin and chloramphenicol. This active molecule 6d also induced bacterial resistance more slowly than norfloxacin and kanamycin. Furthermore, compound 6d was membrane active and low toxic against mammalian cells, and it could rapidly inhibit the growth of MRSA and E. coli and did not obviously trigger bacterial resistance. Compound 6d also displayed strong in vivo antibacterial activity against S. aureus RN4220 in murine corneal infection models. Additionally, absorption, distribution, metabolism, and excretion properties of this type of compounds have shown drug-likeness with good oral absorption and moderate blood–brain barrier permeability. The obtained results demonstrated that ocotillol-derived compounds are a promising class of antibacterial agents worthy of further study.

Graphic abstract

     

Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

Combinatorial drug therapies emerge among the most promising strategies to treat complex pathologies such as cancer and severe infections. Biocompatible nanoparticles of mesoporous iron carboxylate metal–organic framework (nanoMOFs) are used here to address the challenging aspects related to the coincorporation of two antibiotics. Amoxicillin and potassium clavulanate, a typical example of drugs used in tandem, are efficiently coincorporated with payloads up to 36 wt%. Due to the occurrence of two distinct pore sizes/apertures within the MOF architecture, each drug is able to infiltrate the porous framework and localize within separate compartments. Molecular simulations predict drug loadings and locations consistent with experimental findings. Drug loaded nanoMOFs that are internalized by Staphylococcus aureus infected macrophages are able to colocalize with the pathogen, which in turn leads to an alleviation of bacterial infection. The data also reveal potential antibacterial properties of nanoMOFs alone as well as their ability to deliver a high payload of drugs to fight intracellular bacteria. These results pave the way toward the design of engineered “all‐in‐one” nanocarriers in which both the loaded drugs and their carrier play a role in fighting intracellular infections.     

Comparative performance study of four nanofiltration membranes in the separation of mercury and chromium

In this paper, four nanofiltration membranes, viz., (1) coating of N,O-carboxymethyl chitosan (NOCC) on polyethersulfone ultrafiltration (PES UF) substrate membrane; (2) chitosan and acrylonitrile butadiene styrene (ABS) in the blend ratio of 0:100 (ABS); (3) diethylenetriamine pentaacetic acid coating via casting method on PES UF substrate membrane (DC50); and (4) NOCC and cellulose acetate (CA) polymer blend solution (0.4?wt%) coated on a glass plate (NOCC?CCA), were selected from our previous work. By using these membranes, separation behaviour of mercury and chromium ions was studied at different operating conditions from their salt solutions. From the experimental data, it is evident that ABS membrane gave highest observed solute rejection (92.88 and 88.67?% for 10?ppm feed concentration of mercury sulphate?Cwater system and chromium sulphate?Cwater system, respectively) and NOCC?CCA membrane gave highest permeate volume flux. But from the rejection as well as permeate volume flux point of view, NOCC?CPES membrane is considered to be the best choice among all the membranes.     

Mechanically Robust,Electrically Conductive Biocomposite Films Using Antimicrobial Chitosan‐Functionalized Graphenes

An effective way of covalently functionalizing graphene with a chitosan polymer via a nitrene chemistry is demonstrated. The biofunctionalized graphene is prepared by the chemical reduction of graphene oxide using a nitrene chemistry, and then covalently grafting chitosan to the graphene surface. The effectiveness of the biofunctionalized graphene as a reinforcing filler (4 wt%) in a chitosan polymer matrix is verified by the dramatic enhancement of the mechanical properties (breaking stress = 330%, Young's modulus = 243%) and the electrical conductivity (0.3 S m^?1) without much loss in the elongation‐at‐break. The reinforcing effect can be explained by both the homogeneous dispersion of graphene within the matrix and the strong bond arising from the intrinsically intimate contact between the graphene and the matrix. The high antimicrobial activity of the biofunctionalized graphene compared with graphene oxide and chemically reduced graphene may be because of the presence of chitosan polymer on the edges of the graphene. The strong, antimicrobial graphene‐filled composite film can be used for food packaging and for coating various biomedical devices, where bacterial surface colonization is undesirable.     

Preparation and characterization of antibacterial Au/C core-shell composite

An environment-friendly oxidation-reduction method was used to prepare Au/C core-shell composite using carbon as core and gold as shell. The chemical structures and morphologies of Au/C core-shell composite and carbon sphere were characterized by X-ray diffraction, transmission electron microscope, energy dispersion X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the Au/C core-shell composite against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were examined by the disk diffusion assay and minimal inhibition concentration (MIC) methods. In addition, antibacterial ability of Au/C core-shell composite was observed by atomic force microscope. Results demonstrated that gold homogeneously supported on the surface of carbon spheres without aggregation and showed efficient antibacterial abilities.     

Degradable Bioelastomers Prepared by a Facile Melt Polycondensation of Citric Acid and Polycaprolactone-diol

Citrate-based bioelastomers have great potentials in various biomedical fields. An appropriate selection of diol monomers could tune their properties to fulfill different application requirements. Herein, polycaprolacone diol (PCL-diol) was selected as the diol monomer to fabricate poly(caprolactone-diol citrate) (PCC) degradable bioelastomers by a one pot melt polycondensation coupled with subsequent thermosetting or post-polymerization. The catalyst-free polycondensation reaction was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹H nuclear magnetic resonance (¹HNMR) spectroscopy. The properties of the PCC elastomers were explored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), uniaxial tension tests, dynamics mechanical analysis (DMA), water-contact angle and in-vitro degradation measurements. The results showed that the molar ratio of monomers and thermosetting conditions had significant effects on the ultimate properties of the PCC elastomer. By regulating monomer ratio and thermosetting temperature the crosslink density ranged from 32?±?6?mol/m³ to 292?±?18?mol/m³, the tensile strength ranged from 171?±?28?KPa to 977?±?112?KPa, Young’s modulus ranged from 252?±?36?KPa to 1737?±?212?KPa, ultimate elongation ranged from 70?±?9% to 260?±?32%, the static-water-contact-angle was in the range of 65.4?±?1.8?～?91.0?±?0.9° and the weight loss of the PCC elastomer in phosphate buffered saline (PBS) (pH =7.4) was in the range of 30?～?100?wt% after 8?weeks degradation. An elastic and compressible, porous scaffold was fabricated via a salt leaching method, which has potential use in soft tissue grafts.