Antimicrobial fibers based on chitosan and polyvinyl-alcohol

A series of antimicrobial fibers with different weight ratio of chitosan (CS) and polyvinyl alcohol (PVA) were fabricated via a primarily industrialized trail of wet-spinning method, and the morphology and structure of the resulting fibers were studied with the aid of scanning electron micrography (SEM), infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The CP60 blend fiber (60 % chitosan content) was confirmed as the best optimal sample among the blend fibers owing to strong intermolecular hydrogen bonds between PVA and chitosan and showed the maximum mechanical, antistatic, moisture absorption/desorption properties. The CP60 also exhibited good antimicrobial effects against Escherichia coli and Staphylococcus aureus as the chitosan fiber and could be recommended as the alternative material for the wound dressing and the food packing.     

Preparation and characterization of electrospinning PLA/curcumin composite membranes

In this paper, curcumin-loaded electrospinning Poly(lactic acid) (PLA) composite membranes were prepared. Curcumin with different contents (1, 3, and 5 wt%) was loaded to study its anticoagulation property as a drug-eluting stent. The structure of the composite membrane was analyzed by Fourier Transform Infrared (FTIR) spectroscopy, and the results suggested that both PLA and curcumin were present in the composite membrane without chemical reaction between them. Scanning electron microscopy (SEM) and related analysis revealed that the average diameters of composite nanofibers were between 756 and 971 nm with better uniformity in the range of the experiment, furthermore the average diameters of composite nanofibers decreased with the curcumin content increase; The in vitro anticoagulation behavior of curcumin-eluting stents was investigated through static platelet adhesion test, revealing that the anticoagulation property of composite membranes was superior to the pure PLA membrane, and the anticoagulation behavior significantly improved with increasing curcumin by dint of SEM observation.     

Paclitaxel delivery from cobalt-chromium alloy surfaces using self-assembled monolayers

Polymer-based platforms in drug-eluting stents (DESs) can cause adverse reactions in patients. Hence, the development of a polymer-free drug delivery platform may reduce adverse reactions to DES. In this study, the use of a polymer-free platform, self-assembled monolayers (SAMs), is explored for delivering an antiproliferative drug [paclitaxel (PAT)] from a stent material [cobalt-chromium ((Co-Cr) alloy]. Initially, carboxylic acid terminated phosphonic acid SAMs were coated on Co-Cr alloy. Two different doses (25 and 100 μg/cm2) of PAT were coated on SAM coated Co-Cr surfaces using a microdrop deposition method. Also, control experiments were carried out to coat PAT directly on Co-Cr surfaces with no SAM modification. The PAT coated specimens were characterized using the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). FTIR spectra showed the successful deposition of PAT on SAM coated and control-Co-Cr surfaces. SEM images showed islands of high density PAT crystals on SAM coated surfaces, while low density PAT crystals were observed on control-Co-Cr alloy. AFM images showed molecular distribution of PAT on SAM coated as well as control-Co-Cr alloy surfaces. In vitro drug release studies showed that PAT was released from SAM coated Co-Cr surfaces in a biphasic manner (an initial burst release in first 7 days was followed by a slow release for up to 35 days), while the PAT was burst released from control-Co-Cr surfaces within 1-3 days. Thus, this study demonstrated the use of SAMs for delivering PAT from Co-Cr alloy surfaces for potential use in drug-eluting stents.     

Preparation and blood compatibility of electrospun PLA/curcumin composite membranes

In this article, curcumin-loaded electrospun Polylactic acid (PLA) composite membranes were prepared. Curcumin with different concentrations (1, 3 and 5 wt%) was loaded to the PLA membranes to study its anticoagulant property as a drug-eluting stent. X-ray diffraction (XRD) characterization of the prepared membranes indicates that PLA and curcumin mix together well through the method of electrospinning and the composite membrane has larger crystallinity than that of PLA membrane. The in vitro blood compatibility of curcumin-eluting stents was investigated by static platelet adhesion and blood coagulation time (APTT and PT) tests, revealing that the blood compatibility of composite membranes is superior to the pure PLA membrane, and the blood compatibility significantly improves with curcumin concentration increasing by dint of observing SEM images and calculating the inhibition rate of platelet aggregation. Moreover, PLA/curcumin membrane can effectively prolong the blood coagulation time compared with the plasma, and the blood coagulation time of composite membranes improves significantly as curcumin concentration increasing.     

Development and characterization of alginate-chitosan-hyaluronic acid (ACH) composite fibers for medical applications

Natural materials and plants have a long history of medical applications due to their broad range of favorable biological functions including biocompatibility, anti-bacterial, anti-oxidant and anti-inflammatory properties. Main objective of this study was to develop alginate-chitosan-hyaluronic acid (ACH) composite fibers with controlled drug release, and liquid retention properties for better moist wound healing. The dope comprising sodium alginate was extruded into calcium chloride (CaC1₂) coagulation bath. The developed calcium alginate fibers were then passed through a bath containing hydrolyzed chitosan and dip coated with hyaluronic acid for 24 hours. The resulting ACH composite fibers were then rinsed with deionized water and dried using acetone. These fibers were tested for tensile properties, % swelling, liquid absorption (g/g) and controlled drug release. The results concluded that ACH composite fibers can be produced by wet spinning and have adequate tensile properties, high % swelling, liquid absorption (g/g) and controlled release of hyaluronic acid for improved wound healing.     

The influence of fiber diameter of electrospun poly(lactic acid) on drug delivery

Electrospinning is a simple process for the production of fibers with diameters in the range from submicron to micron. Herein we aim to explore the influence of fibrous diameter on the drug delivery. The feasible methods by making choice of solvents and changing flow rate were used to prepare 5-fluorouracil-loaded polylactide (PLA) fibers with a large diameter gap. The drug release behavior in vitro was investigated and analyzed in phosphate buffer solution. The drug distribution and fiber diameter both affected the initial burst release. The results showed that all the asspun fibers could not avoid of burst release. The coarse fibers exhibited slight burst release as compared to fine fibers. During the second stage, the fine fibers released faster than that of the coarse fibers. For the whole release stage, the large-diameter fibers seemed to be beneficial for drug release in the long term and smoothly. The MTT results showed that the cytotoxicity of drugs was maintained.     

Electrospun poly(L-lactic)acid/nanoalumina (PLA/Al2O3) composite fiber mats with potential biomedical application — Investigation of cytotoxicity

PLA fibrous mats containing nanoalumina filler were fabricated by electrospinning method. The morphology of the mats was characterized by SEM, and TEM. In vitro biocompatibility of the electrospun fiber mats was also evaluated. Indirect cytotoxicity evaluation of the fiber mats with human skin fibroblasts revealed that the materials were non-toxic to living cells. The cells cultured on the fibrous mat exhibited normal cells shapes and were integrated well with surrounding fibers. The obtained results confirmed the potential for use of the electrosupun PLA/Al₂O₃ fiber mats for biomedical application.     

Fabrication and characterization of nanofibers based on poly(lactic acid)/chitosan blends by electrospinning and their functionalization with phospholipase A1

In this work, electrospinning of poly(lactic acid) (PLA), chitosan and their blends has been investigated, and nanofibers with a diameter ranging from 90 nm to 1.9 microns were produced and used as carriers for immobilization of the phospholipase A1. A strong influence of chitosan (CS) and the solvent trifluoroacetic acid (TFA) on the morphology, distribution of the nanofibers diameter and on their hydrophobicity was observed. The yield of phospholipase A1 (PLA1) on non-woven fibers was evaluated using the method of Bradford. Their activities and their reutilisability were assessed titrimetrically using soybean lecithin as substrate. The results showed that the degree of immobilization on the non-woven fibers of pure PLA and mixtures PLA/CS4 and PLA/SC6 are 73, 54, 45 % respectively and can be reused up to 4 cycles without significant loss of enzyme activity. Moreover, a remarkable improvement of the activity of phospholipase A1 on non-woven based on pure PLA fibers was observed, indicating that most of the enzymes were probably in their active form.     

Fabrication of Gelatin-Based Electrospun Composite Fibers for Anti-Bacterial Properties and Protein Adsorption

A major goal of biomimetics is the development of chemical compositions and structures that simulate the extracellular matrix. In this study, gelatin-based electrospun composite fibrous membranes were prepared by electrospinning to generate bone scaffold materials. The gelatin-based multicomponent composite fibers were fabricated using co-electrospinning, and the composite fibers of chitosan (CS), gelatin (Gel), hydroxyapatite (HA), and graphene oxide (GO) were successfully fabricated for multi-function characteristics of biomimetic scaffolds. The effect of component concentration on composite fiber morphology, antibacterial properties, and protein adsorption were investigated. Composite fibers exhibited effective antibacterial activity against Staphylococcus aureus and Escherichia coli. The study observed that the composite fibers have higher adsorption capacities of bovine serum albumin (BSA) at pH 5.32–6.00 than at pH 3.90–4.50 or 7.35. The protein adsorption on the surface of the composite fiber increased as the initial BSA concentration increased. The surface of the composite reached adsorption equilibrium at 20 min. These results have specific applications for the development of bone scaffold materials, and broad implications in the field of tissue engineering.     

Micro-scale PLA Fibrous Membranes for Adsorption of Cigarette Smoke

Porous PLA fibrous membranes with different morphologies were successfully fabricated by varying the relative humidity. When the relative humidity was higher than 45 %, nanopores morphology appeared on the surface of PLA fibers. The micro-structures of PLA fibers and the packing densities and through-pore sizes of the PLA fibrous membranes were measured and found to greatly influence the smoke adsorption properties. The smoke adsorption was recorded in photos, and the process of how smoke adsorbed on the membranes was observed by SEM. The max removal efficiencies of nicotine, tar, water vapor, and carbon monoxide were 40.0 %, 36.9 %, 5.8 % and 13.6 % measured by a cigarette-smoking machine, and sensory evaluation was conducted to assess the practical application of fibrous membranes for smoke adsorption.     

Preparation,characterization of antibacterial PLA/TP nanofibers

Polylactic acid (PLA)/Tea polyphenol (TP) composite nanofilms were prepared using an electrospinning process. The mixed dichloromethane (DCM) and N,N-dinethylformamide (DMF) (70:30, v/v) was found to be the most suitable solvent for electrospinning. Various blends of PLA/TP solutions were formed. The morphology of the electrospun nano-scale fibers was investigated by scanning electron microscope (SEM), and the antibacterial performance was tested using shake flask method. The average diameter of the fibers is between 380 and 850 nm. It was found that the fiber diameter decreases as TP content increases, however the fibers may become brittle when the blend ratio of PLA and TP reached 50/50 (w/w). The antibacterial performance can be improved at the beginning when TP content increased. But it gradually gets impaired when TP content surpasses a certain value. The highest inhibitory rate against Escherichia coli and Staphylococcus aureus are 96.9 and 97.6 % respectively.     

Fabrication of a Biodegradable Multi-layered Polyvinyl Alcohol Stent

This study aims to develop biodegradable vascular stents that prevent permanent damage caused by rejection of the immune system of the human body. Polyvinyl alcohol (PVA) yarns are twisted to enhance their strength. The twisted yarns are braided and then coated with chitosan (CS). The CS-coated PVA vascular stents are chemically crosslinked with genipin (GP) to improve their flexibility and biodegradability. Their morphological characteristics are also observed using a stereoscopic microscope, and their properties are evaluated through scanning electron microscopy, Fourier transform infrared, bending test, biodegradability test, drug release measurement, and MTT assay. Results reveal that wet PVA-CS-GP vascular stents coated with multiple CS layers can maintain a tubular structure when they are bent. After crosslinking is performed, the compressive strength of the PVA-CS-GP stents is 17.04 times higher than that of pure PVA. The weight loss rate of the PVA-CS-GP vascular stents as <3 % after 30 days. The PVA-CS-GP vascular stents composed of 0.10 % heparin sodium show a good drug release effect. Biological activity test indicates that these stents exhibit good proliferation, and our structural model verifies that they are good vascular stents.     

Porous Laponite/Poly(L-lactic acid) Membrane with Controlled Release of TCH and Efficient Antibacterial Performance

Fabrication of porous polymer membrane with controlled drug release and efficient antibacterial performances is of great interest in biomedical fields. In this study, Laponite (LAP) nanodisks were first used to encapsulate a model antibiotic drug, tetracycline hydrochloride (TCH). Then, drug-loaded LAP nanodisks with an optimized loading efficiency (85.3 %) were mixed with poly(L-lactic acid) (PLLA) polymer to form drug-loaded composite porous membrane via solvent coasting. The structure, morphology and swelling property of the porous membranes formed with varied solvent ratio of methylene dichloride (DCM) and dimethyl formamide (DMF) in the mixture solvent were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and swelling test. In vitro drug release behavior, the cytotoxicity and the antibacterial activity of drug-loaded composite membranes were evaluated. Results showed that the TCH release was dependent on the physical structure of PLLA membrane and the presence of LAP nanodisks effectively weakened the initial burst release of TCH, and improved the sustained release property of porous PLLA membrane. The released TCH of TCH/LAP/PLLA_3:1 and TCH/LAP/PLLA_4:1 was 10.0 % and 5.3 % within initial 1 h, respectively. More importantly, the porous TCH/LAP/PLLA membrane was cytocompatible and displayed considerable antibacterial activity, solely associated with the loaded TCH drug, confirming its potential utility in wound dressings and tissue engineering.     

Mechanical and moisture absorption characterization of PLA composites reinforced with nano-coated flax fibers

This research is intended to improve the interface between the fibers and the matrix and limit water absorption of bio-based material thereby decreasing degradation of the composites when they are exposed to external environment such as high temperature and humidity. In this study, flax fibers were treated with an organic surface coating containing SiO₂ nanoparticles. This coating was a dispersion of silica fume in epoxy. One composite was also made with raw fibers as reference as well as one sample of pure PLA. Flax fibers/PLA composites were manufactured by hot pressing by stacking 4 PLA films and 3 pieces of flax fabric. Morphology and dispersion of the coating on the fibers was observed by scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Accelerated ageing was carried out on the 3 materials by placing them in a 50 °C water bath until saturation to investigate the influence of the coating on water diffusion. Mechanical properties of the different composites were investigated by tensile (before and after conditioning) and short beam shear (SBS) testing in order to evaluate the impact of the coating on the interfacial properties of the materials. The results show that the fibers surface was homogenized and that a better adhesion was reached because of the coating. Coating the fibers also allowed the decrease in water uptake by more than 10 % and their protection during conditioning, preserving their mechanical properties.     

Effect of surface treatment of jute fibers on the interfacial adhesion in poly(lactic acid)/jute fiber biocomposites

Jute fibers have immense potential to be used as natural fillers in polymeric matrices to prepare biocomposites. In the present study jute fibers were surface treated using two methods: i) alkali (NaOH) and ii) alkali followed by silane (NaOH+Silane) separately. Effects of surface treatments on jute fibers surface were characterized using fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analyses. Further, the effects of surface treatments on jute fibers properties such as crystallinity index, thermal stability, and tensile properties were analyzed by X-ray diffraction method (XRD), thermo gravimetric analysis (TGA), and single fiber tensile test respectively. The effects of surface treatment of jute fibers on interphase adhesion between of poly(lactic acid) (PLA) and jute fibers were analyzed by performing single fiber pull-out test and was examined in terms of interfacial shear strength (IFSS) and critical fiber length.     

Electrospun curcumin loaded poly(lactic acid) nanofiber mat on the flexible crosslinked PVA/PEG membrane film: Characterization and <Emphasis Type="Italic">in vitro</Emphasis> release kinetic study

Herein, a biodegradable and biocompatible composite comprising of support membrane based on crosslinked PVA/PEG film and curcumin loaded electrospun poly(lactic acid) (PLA) nanofiber mat is introduced. The membrane film was prepared from PVA/PEG blend followed by crosslinking with an optimum amount of citric acid, 15 wt.%. After then, PLA solutions with different curcumin content, 0-11 wt.%, were electrospinned on the prepared membrane substrate. The prepared film showed high water absorption, water vapor transmission rate and superior mechanical properties with improved elastic modulus, tensile strength and with an elongation of around 320 % with respect to the non-crosslinked one. Also, the scanning electron microscopy was revealed uniformly dispersed pores throughout the membrane film with a nearly narrow in size distribution centered at 36 μm. As well, a nanostructure porous morphology was found for the electrospun fibrous curcumin loaded PLA from the scanning electron microscopy micrographs and the average fiber diameter was decreased with curcumin content. In vitro drug release from the prepared flexible composite into the vertical diffusion cell was recorded by the measuring curcuminoids content using high performance liquid chromatography and drug release kinetic evaluations were revealed that the release pattern of all prepared samples, containing different content of curcumin, well fitted to the Higuchi’s model signifying diffusion-controlled release mechanism. As well, the determined release rate at the second release stages, i.e. steady state flux (J), was varied from 0.31 to 43.53 μg·cm^-2·h^-1 with increasing drug content from 1 to 11 wt.%. Regarding this results, this flexible composite by providing the moist environment along with miraculous healing properties of curcumin, can be potential candidate for transdermal drug delivery.     

Effects of carbon nanotubes on morphological structure, thermal and flammability properties of electrospun composite fibers consisting of lauric acid and polyamide 6 as thermal energy storage materials

The ultrafine composite fibers consisting of lauric acid (LA) and polyamide 6 (PA6) as form-stable phase change materials (PCMs), were prepared successfully by electrospinning. The effect of carbon nanotubes (CNTs) on the structural morphology, phase change behaviors, thermal stability, flammability and thermal conductivity properties of electrospun LA/PA6 composite fibers was investigated by field-emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), microscale combustion calorimeter (MCC) and melting/freezing times measurements, respectively. SEM observations indicated that the LA/PA6 and LA/PA6/CNTs composite fibers possessed flat and ribbon-shaped morphologies, but the neat PA6 fibers had cylindrical shape with smooth surface; and the average fiber diameters for LA/PA6 composite fibers decreased generally with the addition of CNTs. DSC measurements indicated that the heat enthalpies of the composite fibers were lower that that of neat LA powders, while the amounts of CNTs had no appreciable effect on the phase change temperatures and heat enthalpies of the composite fibers. TGA results showed that the addition of CNTs increased the onset thermal degradation temperature, maximum weight loss temperature and charred residue at 700 °C of the composite fibers, attributed to the improved thermal stability properties. It could be found from MCC tests that there were two-step combustion processes for composite fibers, and corresponded respectively to combustion of LA and polymer chains (PA6) in composite fibers. The addition of CNTs reduced the peak of heat release rate (PHRR) of electrospun composite fibers, contributing to the decreased flammability properties. The improved thermal conductivity performances of LA/PA6/CNTs composite fibers was also confirmed by comparing the melting/freezing times of LA/PA6 composite fibers with that of neat LA powders. The results from the SEM observation showed that the composite fibers had no appreciable variations in shape and diameter after heating/cooling processes.     

Preparation of electrospun LA-PA/PET/Ag form-stable phase change composite fibers with improved thermal energy storage and retrieval rates via electrospinning and followed by UV irradiation photoreduction method

In this paper, novel electrospun LA-PA/PET/Ag phase change composite fibers with different amount of Ag nanoparticles were prepared via the technique of electrospinning followed by UV irradiation method. The morphological structure, thermal energy storage properties, thermal energy storage and release rates of prepared LA-PA/PET/AgNO₃ and LA-PA/PET/Ag composite fibers were investigated by scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), differential scanning calorimeter (DSC), and the measurement of melting and freezing times, respectively. The SEM images revealed that electrospun LA-PA/PET/AgNO₃ and LA-PA/PET/Ag composite fibers possessed the smooth morphologies with cylindrical shape. The corresponding average fiber diameters gradually decreased with increasing content of the AgNO₃ in the solutions, and slightly smaller than those of the LA-PA/PET composite fibers with oblate morphology and wrinkled surfaces. Yellow-brown coloration of electrospun LA-PA/PET/Ag phase change composite fibers were observed after UV irradiation treatment, which demonstrated that Ag ions were successfully reduced to Ag nanoparticles. The TEM images revealed that these reduced Ag nanoparticles were homogenously dispersed within the composite fibers. The results from DSC measurements indicated that the phase change temperatures and enthalpies of electrospun LA-PA/PET/Ag phase change composite fibers with different Ag content have not be influenced by the UVirradiation treatment. The thermal energy storage and release rates of electrospun LA-PA/PET/Ag phase change composite fibers were also improved due to the combination of reduced Ag nanoparticles. These UV-irradiated electrospun phase change composite fibers with excellent thermal energy storage properties can be acted as a novel form-stable PCMs for the applications related to storage and retrieval of thermal energy.     

Preparation of Cross-linked Chitosan Quaternary Ammonium Salt Hydrogel Films Loading Drug of Gentamicin Sulfate for Antibacterial Wound Dressing

Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.     

Influence of noncellulosic contents on nano scale refinement of waste jute fibers for reinforcement in polylactic acid films

In the present study, nanofibrils of cellulose are extracted from waste jute fibers using high energy planetary ball milling process in wet condition. The rate of refinement of untreated fibers having non-cellulosic contents was found slower than treated fibers due to strong holding of fiber bundles by non-cellulosic contents. At the end of three hours of wet milling, untreated fibers were refined to the size of 850 nm and treated fibers were refined to the size of 443 nm. In the subsequent stage, composite films of poly lactic acid (PLA) were prepared by solvent casting with 3 wt% loading of untreated jute nanofibrils, treated jute nanofibrils and microcrystalline cellulose. The influence of non-cellulosic contents on mechanical properties of PLA films are investigated based on results of tensile test, dynamic mechanical analysis and differential scanning calorimetry. The maximum improvement was observed in case of treated jute nanofibril/PLA composite film where initial modulus and tensile strength increased by 207.69 % and 168.67 %, respectively as compared to neat PLA film. These improvements are attributed to the increased interaction of treated jute nanofibrils with PLA matrix due to their higher precentage of cellulosic contents and mechanically activated surface.