Interpenetrating polymer network matrices of sodium alginate and carrageenan for controlled drug delivery application

Interpenetrating polymer network (IPN) matrices of sodium alginate and carrageenan were prepared for controlled release application. The propranolol-resin complex (resinate) loaded matrices were prepared by wet granulation/covalent crosslinking method and subsequently compressed into tablets. The SEM, DSC and XRD studies confirmed the amorphous nature of drug in the IPN matrix and FTIR confirmed the IPN formation and stability of drug within IPN matrix. The pure drug propranolol HCl showed rapid and complete dissolution within 60 min, while drug release from resinate was extended for 2.5 h and that from IPN tablets was still slower and drug release prolonged over 18 h. The crosslinking time of granules affected the release of drug from IPN matrix.     

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.     

Water-stability and biological behavior of electrospun collagen/PEO fibers by environmental friendly crosslinking

Electronspun collagen fibers have to be crosslinked to improve their mechanical properties and water stability. But, the toxicity of some crosslinkers like glutaraldehyde have been fiercely debated. Others like genipin have been proved to affect the morphology of electrospinning fibers. Citric acid (CA) as a crosslinking agent has the advantages of simple, cheap and nontoxicity. In this paper, the effects of CA crosslinking on the physical and biological properties of electrospun collagen/polyethylene oxide (PEO) nanofibrous membranes were investigated and compared with dehydrothermal (DHT) crosslinking. Collagen/PEO fibers crosslinked by 10 wt% CA had at least 80 % higher crosslinking degree (p<0.05) and better water stability compared with DHT crosslinking (p<0.05). The stress of fibers crosslinked by CA (7.11±0.05 MPa) has been improved compared with non-crosslinked fibers (5.86±0.02 MPa). At the same time, the strain of non-crosslinked fibers was highest (10.90 %). The results of enzymatic (ED) and hydrolytic degradation (HD) of fibers showed crosslinking could improve the resistance of collagen/PEO nanofibers against ED and HD. The hemolytic percentages of fibers after crosslinking was below 5 %, which proved that CA could protect red cells from destroying. The results of cytotoxicity test showed fibers before and after crosslinking both had no cytotoxicity and that of animal acute test indicated membranes treated with DHT and CA had no apparent toxicity.     

Facilitation of α-polylysine in TGase-mediated crosslinking modification for gluten and its effect on properties of gluten films

In this study, α-polylysine was used to enhance the cross-linking effect of TGase on gluten and its effects on properties of gluten films were investigated. The amount of free ammonia released from the cross-linking reaction of gluten induced by TGase at the presence of α-polylysine obviously increased, and more polymers with higher molecular weight were formed from the SDS-PAGE results, which indicated that the TGase-mediated cross-linking reaction ability of gluten was strengthened with the incorporation of α-polylysine. The tensile strength of the films from gluten modified with TGase (20 units/g wheat gluten) and 2% α-polylysine (g/g gluten) for 3 h increased from 4.02 ± 0.09 MPa to 5.28 ± 0.14 MPa, which was more effective than that treated with TGase alone (in which the tensile strength of the films was 4.49 ± 0.10 MPa). The TGase treatment with α-polylysine of gluten improved the water stability of the films much more than that treated with TGase alone. A rougher surface and a more compact cross-section structure were observed by SEM for the films from TGase-α-polylysine treated gluten. The contact angles between the gluten films surface and a water droplet increased because of TGase-mediated cross-linking modification.     

Chitosan-Genipin Microspheres for the Controlled Release of Drugs: Clarithromycin,Tramadol and Heparin

The aim of this study was to first evaluate whether the chitosan hydrochloride-genipin crosslinking reaction is influenced by factors such as time, and polymer/genipin concentration, and second, to develop crosslinked drug loaded microspheres to improve the control over drug release. Once the crosslinking process was characterized as a function of the factors mentioned above, drug loaded hydrochloride chitosan microspheres with different degrees of crosslinking were obtained. Microspheres were characterized in terms of size, morphology, drug content, surface charge and capacity to control in vitro drug release. Clarithromycin, tramadol hydrochloride, and low molecular weight heparin (LMWH) were used as model drugs. The obtained particles were spherical, positively charged, with a diameter of 1–10 μm. X-Ray diffraction showed that there was an interaction of genipin and each drug with chitosan in the microspheres. In relation to the release profiles, a higher degree of crosslinking led to more control of drug release in the case of clarithromycin and tramadol. For these drugs, optimal release profiles were obtained for microspheres crosslinked with 1 mM genipin at 50 ºC for 5 h and with 5 mM genipin at 50 ºC for 5 h, respectively. In LMWH microspheres, the best release profile corresponded to 0.5 mM genipin, 50 ºC, 5 h. In conclusion, genipin showed to be eligible as a chemical-crosslinking agent delaying the outflow of drugs from the microspheres. However, more studies in vitro and in vivo must be carried out to determine adequate crosslinking conditions for different drugs.     

Electrospun Poly-lactic Acid/Chitosan Nanofibers Loaded with Paclitaxel for Coating of a Prototype Polymeric Stent

Electrospun composite fibers of poly-lactic acid (PLA), chitosan (Ch) and paclitaxel (PTX) were fabricated for surface covering of a polymeric prototype PLA stent by means of single nozzle electrospinning approach to prepare a low cytotoxicity drug-eluting stent. Different concentrations of the drug (40 %, 60 %, 80 %, 100 % and 120 %) and chitosan (3 %, 5 %, 7 % and 9 %) were incorporated to reach the optimum composite fibers. The electrospun composite fibers were subjected to detailed analyses including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile test, MTT assay, cell culture and in vitro drug release. Results have confirmed a proper physical encapsulation of PTX in the polymeric matrix in which no chemical bonding was detected between the polymers and the drug. Among the fabricated composite fibers, specimens including 40 % and 60 % drug also exhibited an excellent cytotoxicity and controlled drug release. SEM images have proved the effect of paclitaxel in resisting cell adhesion and propagation on the fibers. Findings from this study suggest a novel polymer/drug coating that could be potentially applicable in surface covering of polymeric stents e.g. PLA stents.     

Effects of electron-beam irradiation crosslinking on PA6 fibers

Irradiation crosslinking of PA6 fibers with and without the presence of triallyl cyanurate (TAC) was investigated. The dose for incipient gel formation was 500 kGy for pristine PA6 fibers and it decreased to 12 kGy when 5 % TAC was incorporated. Changes in structure and properties of irradiated PA6 fibers were analyzed by X-ray diffraction, infrared spectroscopy and thermal gravimetric analysis. Irradiation crosslinking improved the anti-dripping properties of PA6 fibers effectively. Irradiated samples showed an increase of the breaking strength and then a decrease at further doses due to radiolysis effect, the elongation at break decreased during the irradiation process. Irradiation crosslinking had not changed the crystal form and crystallinity decreased first and then increased to some extent. DSC measurement reported that the melting temperature decreased with increasing the dose. The thermal stability decreased after irradiation whereas the amount of nonvolatile residue at 600 °C increased as the irradiation dosage increased. The infrared spectra of irradiated samples were identical with the unirradiated, no new bands were observed.XPS analysis showed that the number of C-C band increased after irradiation which proves that branching and crosslinking has occurred.     

Water-resistant Lignin/Poly(vinyl alcohol) Blend Fibers for Removal of Hexavalent Chromium

Lignin is the second most abundant renewable biomass-derived natural resource that has been used to replace traditional petrochemical-based materials. However, fabricating the lignin component into the various forms required for practical application is still challenging. In this work, we fabricated water-resistant lignin/poly(vinyl alcohol) (PVA) blend fibers by wet spinning and glutaraldehyde crosslinking methods. The effect of the lignin/PVA blend ratio and glutaraldehyde crosslinking process on the physicochemical properties of wet-spun lignin/PVA blend fibers were studied using maximum draw ratios, hydrolytic degradation profiles, and mechanical properties. Furthermore, the hexavalent chromium [Cr(VI)] removal behavior of lignin/PVA blend fibers was investigated according to the effect of pH, initial Cr(VI) concentration, and contact time. The wet-spun lignin/PVA blend fiber achieved excellent water stability through glutaraldehyde crosslinking and exhibited notable Cr(VI) adsorption capacity (350.87 mg/g) and good regeneration ability. These findings demonstrate that glutaraldehyde-crosslinked lignin/PVA blend fibers could be promising adsorbents for the remediation of heavy metal species containing textile wastewater.     

The effect of bentonite concentration on the drug delivery efficacy of a pH-sensitive alginate/bentonite hydrogel

We produced a protein loaded, pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a nontoxic polysaccharide with favorable pH-sensitive properties that make it useful for the intestinal delivery of protein drugs. However, the use of alginate for drug delivery is limited by drug leaching and rapid dissolution of alginate at the higher pH, which may result in lower entrapment efficiency and a burst in the release of entrapped protein drugs. To overcome these problems, we created a novel cross-linked alginate-bentonite hydrogel by combining mineral-rich bentonite with the alginate matrix along with an additive to ensure controlled release. We analyzed the gel in the drug loading process in an aqueous environment by looking at the release profiles of a model protein drug (BSA) from the hydrogel at pH values of 4.5, 5.2 (skin area) and 7.4, 9.2 (wound area). The swelling ratio decreased with bentonite concentration, but did not fall below 6. The rate of drug release was slowest at a pH value of 4.5 and fastest at a pH value of 9.2. The rate of drug release decreased with bentonite concentration. The presence of bentonite prevents the rapid dissolution of alginate at the higher pH, ensuring the controlled release of the entrapped drug.     

Increasing oxidative stability in corn oils through extraction of γ-oryzanol from heat treated rice bran

Corn oil was mixed with heated rice bran with different extraction periods and ratios of rice bran to corn oil to extract γ-oryzanol from rice bran. Selected corn oils based on the content of γ-oryzanol were heated at 180 °C for 100 min or 60 °C for 16 days, and oxidative stability was evaluated. Corn oils recovered from the mixture of rice bran showed higher oxidative stability at both 60 and 180 °C treatment compared to control corn oils. At 180 °C, corn oils of a 1:5 ratio of rice bran to corn oil (w/w) showed higher oxidative stability than did those of 1:3 and 1:7 (w/w), whereas at 60 °C, corn oils of 1:7 (w/w) showed higher oxidative stability than did others. γ-Oryzanol can be extracted through a corn-oil mixture at 80–90 mg/100 g oil, which is about 4.0% recovery of 2244 mg/100 g crude rice-bran oil. Oxidative stability of corn oils increased significantly, partly because of the extraction of γ-oryzanol under current experimental conditions.     

Preparation,structure and properties of boron modified high-ortho phenolic fibers

Boron modified high-ortho phenolic fibers (o-BPFs) were prepared by melt-spinning from boron modified highortho phenolic resins (o-BPRs) with the weight-average molecular weight of 4973 g/mol, followed by being cured in a solution of formaldehyde and hydrochloric, and then heat-treated under high temperature. Gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR) were used to measure the average molecular weight and ortho/para (o/p) ratio of o-BPRs. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the chemical and morphological structures of o-BPRs and o-BPFs. Thermogravimetric analysis (TGA) was employed to examine the thermal stability properties of different resins and fibers and the tensile strength of fibers was measured by a tensile tester. It was found that under proper curing and heat-treatment conditions, the tensile strength of o-BPFs reached 213.6 MPa and the char yield in N₂ atmosphere at 800 °C attained 75.4 %. Compared with phenolic fibers (PFs), the decomposition temperatures at 5 % weight loss of o-BPFs in N₂ and air atmospheres were increased by 156.8 °C and 219.0 °C, respectively.     

Laccase-mediated enhancement of the properties of regenerated fibers from wheat gliadin

In this study, laccase-mediated crosslinking was used to develop regenerated protein fibers from wheat gliadin with good mechanical properties and water stability. The oxygen consumption during laccase catalyzed oxidation of gliadin, molecular weight of gliadin, mechanical properties, water stability, thermal properties and morphology of gliadin fibers were tested to prove the effect of laccase as the crosslinker of gliadin. The rapid decrease of dissolved oxygen in gliadin solution indicated laccase was active in oxidizing gliadin. The results of SDS-PAGE and SEC demonstrated that laccase-mediated crosslinking reaction effectively occurred. The mechanical properties and water stability of the gliadin fibers with laccase treatment significantly were improved. The fibers from gliadin with laccase treatment exhibited a much smoother and more uniform surface was observed by SEM for the laccase-mediated modified gliadin fibers.     

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.     

Microstructure, fundamental rheology and baking characteristics of batters and breads from different gluten-free flours treated with a microbial transglutaminase

Gluten is a fundamental component for the overall quality and structure of breads. The replacement of the gluten network in the development of gluten-free cereal products is a challenging task for the cereal technologist. The functionality of proteins from gluten-free flours could be modified in order to improve their baking characteristics by promoting protein networks. Transglutaminase (TGase) has been successfully used in food systems to promote protein cross-linking. In this study, TGase was investigated for network forming potential on flours from six different gluten-free cereals (brown rice, buckwheat, corn, oat, sorghum and teff) used in breadmaking. TGase was added at 0, 1 or 10 U/g of proteins present in the recipe. The effect of TGase on batters and breads was evaluated by fundamental rheological tests, Texture Profile Analysis and standard baking tests. Three-dimensional elaborations of Confocal Laser Scanning Microscopy (CLSM) images were performed on both batters and breads to evaluate the influence of TGase on microstructure. Fundamental rheological tests showed a significant increase in the pseudoplastic behaviour of buckwheat and brown rice batters when 10 U of TGase were used. The resulting buckwheat and brown rice breads showed improved baking characteristics as well as overall macroscopic appearance. Three-dimensional CLSM image elaborations confirmed the formation of protein complexes by TGase action. On the other side, TGase showed negative effects on corn flour as its application was detrimental for the elastic properties of the batters. Nevertheless, the resulting breads showed significant improvements in terms of increased specific volume and decreased crumb hardness and chewiness. Under the conditions of this study, no effects of TGase could be observed on breads from oat, sorghum or teff. Overall, the results of this study show that TGase can be successfully applied to gluten-free flours to improve their breadmaking potentials by promoting network formation. However, the protein source is a key element determining the impact of the enzyme.     

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.     

Controlling the moisture absorption capacity in a fiber-reinforced thermoplastic starch using sodium trimetaphosphate

A novel biodegradable material derived from thermoplastic potato starch was prepared with intended uses in high moisture environments where its high water sorption characteristics are beneficial, such as wound dressing, transdermal patches or food packaging. A modified composite was prepared for this purpose by reactive extrusion whereby potato starch and 2.5-25% (w/w) sisal cellulose fibers were compounded together in the presence of 2.7% (w/w) sodium trimetaphosphate. The fibers were included to increase the wet strength of the material. A low degree of substitution (0.088-0.113) was sought by bound phosphate groups with anionic character in order to overcome a reduction in moisture absorption capacity resulting from fiber incorporation, yet being insufficient to cause embrittlement via crosslinking. The results showed the approach has sufficient merit to minimize the influence of the hydrophobic fibers on the water absorption capacity of the starch material but adhering to so low of a degree of substitution could not fully prevent a reduction. The results also suggested that the fibers may have participated in the crosslinking reaction.     

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.     

Environment-friendly crosslinking of cornstarch by pentanedioic acid for stabilizing the viscosity of starch paste during warp sizing

Acid-thinned cornstarch was crosslinked with pentanedioic acid to different degrees to enhance viscosity stability of cooked starch paste for replacing the currently used toxic crosslinking agents such as formaldehyde and epichlorohydrin in the preparation of starch sizing agents. The degree of crosslinking was determined according to the stability, adhesion-to-fibers, film properties, desizability, and aerobic biodegradation of crosslinked starch. The degree of crosslinking showed significant effects on the stability, adhesion, desizability, and film properties, but was less sensitive to the biodegradation and wear loss of starch film. Suitable degree of crosslinking resulted in stable viscosity, good adhesion to fibers, strong and bending resistant film, and better desizability. Low degree of crosslinking could be utilized to increase the stability and improve usability of the starch used as warp sizing agent. The degree of crosslinking range (902-477 anhydroglucose units per crosslink) was recommended to stabilize the viscosity of cooked starch paste and improve the sizing properties of starch sizing agents.     

Synthesis and characterization of poly(N-tert-butylacrylamide-<Emphasis Type="Italic">co</Emphasis>-acrylamide) hydrogel with enhanced responsive properties

To synthesize a series of novel temperature sensitive hydrogels, N-tert-butylacrylamide (NtBA) and acrylamide (AAm) were used as the comonomers and polymerized by free-radical crosslinking copolymerizarion. The poly(ethylene glycol) (PEG) with molecular weight of 400, 4000 and 6000 g·mol^-1 was used as the porogen. The equilibrium swelling capacity, swelling/deswelling kinetics and diffusion parameters of obtained hydrogels were systematically evaluated. As revealed by SEM micrographs, the macroporous structure of hydrogels can be modulated by the crosslinking level, PEG molecular weight and dosage. FTIR analysis demonstrated that the porogen PEG was completely leached out of the gel matrix. Compared with the conventional hydrogels, the PEG-modified (PGel) hydrogels exhibited enhanced temperature sensitivity and superior kinetics during the swelling, deswelling and pulsatile swelling processes. Controlled release of salicylic acid also demonstrated the good usability of PGel hydrogel, which rendered it great potential for controlled drug delivery systems.     

Preparation of regenerated cellulose fiber via carbonation (II)

Sodium cellulose carbonate (CC-Na) dissolved in 8.5 wt% NaOH/ZnO (100/2–3, w/w) aqueous solution was spun into some acidic coagulant systems. Diameter of regenerated cellulose fibers obtained was in the range of 15–50μm. Serrated or circular cross sectional views were obtained by controlling salt concentration or acidity in the acid/salt/water coagulant systems. Velocity ratio of take-up to spinning was controlled up to 4/1 with increasing spinning velocity from 5 to 40 m/min. Skin structure of was developed at lower acidity or higher concentration of coagulants. Fineness, tenacity and elongation of the regenerated cellulose fibers were in the range of 1.5–27 denier, 1.2–2.2 g/d, and 8–11.3%, respectively. All of CC-Na and cellulose fibers spun from CC-Na exhibited cellulose II crystalline structure. Crystallinity index was increased with increasing take-up speed.