Electrospun poly(l-lactic acid) fiber mats containing crude Garcinia mangostana extracts for use as wound dressings

Poly(l-lactic acid) (PLLA) fiber mats containing two types of crude Garcinia mangostana Linn. (GM) extract [i.e., dichloromethane extract (dGM) and acetone extract (aGM)] were successfully prepared by electrospinning process. Both the neat and the GM-loaded PLLA fibers were smooth, with the average diameters ranging between 0.77 and 1.14 μm. The release characteristics of GM from the GM-loaded PLLA fiber mats were carried out by total immersion method in acetate buffer or simulated body fluid that contained 0.5 % v/v Tween 80 and 3 % v/v methanol (hereafter, A/T/M or S/T/M medium) at either 32 or 37 °C, respectively. The maximum cumulative amounts of GM released from the GM-loaded PLLA fiber mats in the S/T/M medium were greater than those in the A/T/M medium. Moreover, the cumulative amounts of GM released from the aGM-loaded PLLA fiber mats were greater than those from the dGM-loaded PLLA fiber mats in both types of medium. The antibacterial activity of the dGM-loaded PLLA fiber mats was greatest against Staphylococcus aureus DMST 20654, while that of the aGM-loaded PLLA fiber mats was greatest against S. aureus ATCC 25923 and S. epidermidis. Lastly, only the dGM-loaded PLLA fiber mats at extraction ratio of 10 mg mL^?1 were toxic to the human dermal fibroblasts.     

Electrospun cellulose acetate fiber mats containing curcumin and release characteristic of the herbal substance

Ultra-fine cellulose acetate (CA; M_w ≈ 30,000 Da; degree of acetyl substitution ≈ 2.4) fiber mats containing curcumin from the plant Curcuma longa L., widely known for its anti-tumor, antioxidant, and anti-inflammatory properties, were fabricated, for the first time, from the neat CA solution (17% w/v in 2:1 v/v acetone/dimethylacetamide) containing curcumin in various amounts (i.e., 5–20 wt.% based on the weight of CA powder) by electrospinning. Incorporation of curcumin in the neat CA solution did not affect the morphology of the resulting fibers, as both the neat and the curcumin-loaded CA fibers were smooth. The average diameters of the curcumin-loaded CA fibers ranged between 314 and 340 nm. The integrity of the as-loaded curcumin in the curcumin-loaded CA fiber mats was intact as indicated by the ¹H nuclear magnetic resonance spectrometric results and the ability of the as-loaded curcumin in maintaining its free radical scavenging ability. Investigation of the release characteristic of curcumin from the curcumin-loaded CA fiber mats was carried out by the total immersion and the transdermal diffusion through a pig skin method in the acetate buffer solution containing Tween 80 and methanol or the B/T/M medium at 37 °C. In the total immersion method, almost all of the curcumin loaded in the curcumin-loaded CA fiber mat specimens was released into the medium (90 to 95%), while considerably lower values were obtained when the curcumin-loaded CA fiber mats were placed on top of a piece of pig skin. Lastly, the curcumin-loaded CA fiber mats were proven non-toxic to normal human dermal fibroblasts.     

Synthesis,Structure and Luminescence Property of a 3D Diamondoid Interpenetrated Zn(II)-Organic Framework

A new metal–organic framework of Zn(II) ion, [Zn(muco)(bipy)·2H₂O] (where, muco = trans, trans-muconate dianion, bipy = 4,4′-bipyridine) has been synthesized by solvothermal reaction of Zn(II) ion, muco ligand and bipy spacer. X-ray structure determination reveals that compound 1 has a 3D diamondoid (dia) framework with novel fivefold interpenetrating nets. Topological analysis shows the presence of 4-connected Zn(II) nodes with {6⁶} topology. Thermal analysis reveals that the compound is stable up to 340 °C. Photoluminescence study shows the emission of 1 owing to the presence of muco ligand and the intensity of luminescence emission is higher than that of free muco ligand.     

Electrospun cellulose acetate fiber mats containing asiaticoside or Centella asiatica crude extract and the release characteristics of asiaticoside

Ultra-fine cellulose acetate (CA; M_w ≈ 30,000 Da; degree of acetyl substitution ≈ 2.4) fiber mats containing asiaticoside (AC) from the plant Centella asiatica L. either in the form of pure substance (PAC) or a crude extract (CACE) were fabricated by electrospinning. Incorporation of either PAC or CACE (40 wt.% based on the weight of CA) in the neat CA solution (17% w/v in 2:1 v/v acetone/dimethylacetamide) did not affect the morphology of the obtained fibers, as both the neat and the herb-loaded CA fibers were smooth. The average diameters of these fibers ranged between 301 and 545 nm. Determination of the release characteristics of AC from the herb-loaded CA fiber mats was carried out by the total immersion and the transdermal diffusion through a pigskin method in acetate or phosphate buffer solution that contained methanol (hereafter, A/B/M or P/B/M medium) at either 32 or 37 °C, respectively. In the total immersion method, the maximum amounts of the AC released from the PAC- and the CACE-loaded CA fiber mats into the A/B/M medium were ∼24 and ∼10% (based on the weight of the specimens), while those of the AC released into the P/B/M medium were ∼26 and ∼12%, respectively. Considerably lower values were, however, obtained when the materials were placed on top of a piece of pigskin. Lastly, the herb-loaded CA fiber mats released no substance that was harmful to normal human dermal fibroblasts, rending their potential for use as topical/transdermal or wound dressing patches.     

Oil absorbency of cellulose/butylmethacrylate graft polymer fibers

Cotton pulp cellulose and butyl methacrylate were used as the main raw materials to synthesize cellulose/butylmethacrylate graft polymer (Cell-g-PBMA) via homogeneous ATRP method, after which the graft polymer was dissolved in N,N-dimethylacetamide to prepare a spinning solution, and the novel oil-absorbent Cell-g-PBMA graft polymer fibers were spun by wet-spinning method. The morphology of the polymer fibers before and after oil absorption was analyzed using a high-powered microscope and scanning electron microscope and the saturated oil absorption rate as well as buoyancy recovery of the fiber products were also studied. The results showed that Cell-g-PBMA polymer fibers had a rough surface and exhibited a void network structure that was specific to oil-absorbent materials. The saturated absorption rates of the Cell-g-PBMA polymer fibers for crude oil, vegetable oil, dichloromethane and diesel were 96.5, 78.7, 38.4, and 27.2 g/g, respectively, which were about 3–6 times that of a commercial polypropylene sorbent. The Cell-g-PBMA fibers also displayed excellent oil/water selectivity and high buoyancy recovery in the clean-up of oil over water. Its excellent oil absorbency demonstrated oil absorbent characteristics of both traditional oil-absorbing materials and synthetic oil-absorbing resins, rendering it an excellent fibrous oil-absorbent material.     

Electrospinning of chitosan/poly(lactic acid-co-glycolic acid)/hydroxyapatite composite nanofibrous mats for tissue engineering applications

Electrospinning, which is a fiber fabrication technique using electrical forces to produce fibers with diameters ranging from nanometers to several micrometers, can be used to prepare materials mimicking the extracellular matrix proteins for potential use as tissue engineering scaffolds. In this study, nanofibrous mats of chitosan (CH) and poly(lactic acid-co-glycolic acid) (PLGA) having fiber diameters between 167 to 525 nm, and containing hydroxyapatite (HAp), were prepared by electrospinning technique. Morphological, chemical, thermal and degradation tests and cell affinity tests were carried out. Chitosan mats were stable in aqueous media and showed degradability in the presence of lysozyme. In PBS solution, PLGA mats disintegrated completely in 2 weeks. Meanwhile, CH-PLGA mats containing equal amounts of both CH and PLGA fibers and CH-PLGA-HAp samples containing 20 % HAp lost 50 and 40 % of their initial weight in 4 weeks, respectively. Cell culture tests showed that all electrospun fibrous mats promoted SaOs-2 cell attachment and proliferation. However, cell proliferation on CH-PLGA-HAp fibrous mats was higher compared to the others after 7 days demonstrating the positive effect of HAp on cell affinity properties compared to pristine CH or PLGA fibrous scaffolds.     

Preparation and characterization of a new polymer/pharmaceutical-based composite. Part I: Meloxicam

Composites of low-density polyethylene (LDPE), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-octadecene), and an LDPE/EVA blend were prepared with different amounts of meloxicam (1, 3 and 5 wt %) by the melt blending process. Meloxicam was homogenously dispersed in polymer matrices. The polymer–meloxicam composites showed thermal behavior and thermal characteristics similar to those of the original polymers. Meloxicam release from the composites was examined in vitro for 50 days. The composites were incubated in phosphate-buffered solution and meloxicam concentration was determined by high-performance liquid chromatography. The prolonged release of the drug indicates that meloxicam-loaded plastic rings offer potential for control of reproduction and chronic inflammatory conditions.     

Residual monomer release from orthodontic adhesives cured with different light sources

Introduction: The aim of this study was to evaluate the residual monomer release from orthodontic adhesives cured with light-emitting diode (LED) and halogen light sources.

Methods: Seven hundred and twenty stainless steel brackets were divided into 3 groups according to the adhesive system used (Transbond XT light-cure adhesive [TXT], Transbond LR capsule [LR], and Light Bond light-cure adhesive paste [LB]), and each group was divided into 2 subgroups according to light-curing procedure (LED or halogen). Brackets were bonded with adhesives onto tooth buccal surfaces and polymerized. Each specimen contained 24 brackets that simulated the oral environment (n = 5). The specimens were immersed in a 75% ethanol/water solution at 37 °C for 10 min, 1 h, 1 d, 7 d, 14 d, and 30 d, respectively. Eluted monomers (Bis-GMA, UDMA, and TEGDMA) were detected using HPLC.

Results: There was residual monomer release at all time periods, and the highest amount of release was observed cumulatively on the 30th day. The cumulative Bis-GMA released from adhesives was not different (p > 0.05). The cumulative TEGDMA released from adhesives was statistically different (p < 0.05). There was no statistical difference between QTH and LED light-curing units for each adhesive (p > 0.05).

Conclusions: The release of residual monomers stays at a high level for a long time after polymerization. The total leaching of residual monomers from the Light Bond light-cure sealant resin plus Light Bond light-cure adhesive paste was higher than that of other materials for both curing units. Different curing units (LED or QTH) did not affect the monomer release from the orthodontic adhesives.     

Aerobic biodegradation of cellulose acetate

Two separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: an in vitro enrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). The in vitro assay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% (v/v) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2–3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles. In vitro enrichments with CDA (DS = 1.7) films were able to degrade > 80% of the films in 4–5 days. Cellulose acetate (DS = 2.5) films required 10–12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in the in vitro assay. The wastewater treatment assay was less active than the in vitro enrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [1-¹⁴C]-acetate to ¹⁴CO₂ in the in vitro assay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution. © 1993 John Wiley & Sons, Inc.     

Separation and Purification of Bioactive Flavonol Glycosides from Hedyotis diffusa Willd by High-Speed Counter-Current Chromatography

Three flavonoid glycosides including quercetin-3-O-[2″-O-(6″′-O-E-sinapoyl)-β-D-glucopyranosyl]-β-D-glucopyranoside(I), quercetin-3-O-[2″-O-(6″′-O-E-feruloyl)-β-D-glucopyranosyl]-β-D-glucopyranoside(II) and quercetin-3-O-[2″-O-(6″′-O-E-feruloyl)-β-D-glucopyranosyl]-β-D-galactopyranoside(III) were isolated and purified from Hedyotis diffusa Willd by high-speed counter-current chromatography (HSCCC). This run was carried out with a two-phase solvent system composed of n-hexane–ethyl acetate–n-butanol–methanol–1.0% acetic acid (1:1:3.5:1:4.5, v/v) by eluting the lower phase as the mobile phase with a flow-rate at 2.0 ml/min. Consequently, 29.6 mg of I, 35.1 mg of II, 41.3 mg of III with purities of over 95% were obtained from 200 mg of the crude extracts in a single run in less than 130 min. The structure of the isolated compounds was confirmed by MS, ¹H NMR, and ¹³C NMR analysis.     

A Novel 3-D Nanoporous Ce(III) Metal-Organic Framework with Terephthalic Acid; Thermal,Topology, Porosity and Structural Studies

This study describes the synthesis, crystal structure, porosity, and thermal stability of a new three-dimensional nano-porous metal-organic framework, [Ce₂(tp)₃(DMF)₂(DMSO)₂]_n, 1, (H₂tp = terephthalic acid, DMF = dimethyl formamid, DMSO = dimethyl sulfoxide). Compound 1 was synthesized by the solvothermal reaction of Ce(NO₃)₃·6H₂O and H₂tp and was then characterized by single-crystal X-ray diffraction and infrared spectroscopy. Structural analysis of 1 showed that Ce(III) ion has coordination number nine in a distorted mono-capped square anti-prismatic geometry. Gas sorption studies revealed a relatively reversible type-I isotherm characteristic of a porous material with surface area, pore volume, and average pore size of 179.4 m² g^?1, 0.73 cm³ g^?1, and 3.8 Å, respectively.     

Poly(thioether-ester) nanoparticles entrapping clove oil for antioxidant activity improvement

Poly(thioether-ester) was synthesized from dianhydro-d-glucityl diundec-10-enoate (DGU), a fully renewable diester diene monomer, and a dithiol, and employed to nanoencapsulate clove oil, a great source of eugenol, aiming to improve its antioxidant activity. Nanoparticles were obtained by miniemulsion polymerization with clove oil varying from 0 to 25% (w/w of DGU). Spherical and stable nanoparticles were obtained with particle size between 192 and 284 nm and high encapsulation efficiency (~98%). Results of FT-IR and DSC also confirmed the incorporation of clove oil into nanoparticles, with a gradual reduction in the melting point from 66 °C to 50 °C with the addition of clove oil. In addition, monomer conversion and polymer molar masses decreased with the increase of the amount of clove oil, probably due to the occurrence of reactions between thiyl groups and the double bond of eugenol. These results suggest that part of the incorporated clove oil is chemically bound to the polymer chain forming particles with bound/loaded clove oil. Poly(thioether-ester) nanoparticles loaded with 6% of clove oil exhibited an increase in antioxidant activity of ~26% for β-carotene/ linoleic acid assay and a reduction of 66% on EC₅₀ for 2,2-diphenyl-1-picryl hydrazyl assay.     

Synthesis,characterization and in vitro antibacterial assessments of a novel modified poly[maleic anhydride-alt-acrylic acid]/acriflavine conjugate

Water-soluble maleic anhydride-containing poly[maleic anhydride-alt-acrylic acid] (poly(MA-alt-AA) or MAAA) copolymer was synthesized by free-radical chain polymerization reaction, in 1,4-dioxane in the presence of benzoyl peroxide, 0.1 %, as the radical initiator at 70 °C under a nitrogen atmosphere. The purified copolymer was then modified with an anti-external fungal and anti-cancer active agent, acriflavine (AF). The modification reaction was performed 48 h at 70 °C in dimethylformamide organic media, using triethylamine (TEA or Et₃N) as the catalyst. The modified or conjugated copolymer/drug couple was named as MAAA/AF. Detailed structural characterization of the copolymer (MAAA) and modified product (MAAA/AF) was carried out by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (¹H-NMR and ¹³C-NMR). The obtained FTIR, ¹H-NMR, and ¹³C-NMR spectra confirmed that AF was successfully bound to the MAAA copolymer backbone by ring-opening reaction. Antimicrobial susceptibility of the MAAA, AF, and MAAA/AF was evaluated by Kirby Bauer Disc Diffusion method on Mueller–Hinton Agar using Enterecoccus faecium, Enterohaemorrhagic Escherichia coli (EHEC), Staphylococcus aureus and Listeria monocytogenes. Results obtained indicated that MAAA/AF had antibacterial activity on EHEC and S. aureus at 50, 40, and 30 µg. A mechanism for MAAA and AF was then also suggested for the conjugation reaction.     

Method of analysis for deoxynivalenol and zearalenone from cereal grains

A method was developed to determine deoxynivalenol and zearalenone in corn, wheat, oats, rice and barley. The toxins are extracted with methanol/water (50:50, v/v) (2×) and partially purified by partitioning into ethyl acetate and then defatting with acetonitrile-petroleum ether. Toxins are isolated by silica gel column chromatography. Interfering materials are removed from the column with benzene; zearalenone is eluted with benzene/acetone (95:5, v/v), and after a column wash of chloroform/methanol (95:2, v/v), deoxynivalenol is eluted with chloroform/methanol (95:5, v/v). Zearalenone is quantitated by thin-layer chromatography and deoxynivalenol by gas-liquid chromatography of the trimethylsilyl derivative. The detection limit is about 0.02 μg/g for each toxin. Recoveries of added toxins varied with substrate and level of toxins. Recovery of deoxynivalenol ranged from 58% for 1 ppm in rice to 108% for 1 ppm in corn. Average recoveries for all levels (1, 2 and 5 ppm) ranged from 69% for barley to 89% for oats. Recovered zearalenone ranged from 40% for 5 ppm in wheat to 100% for 1 ppm in barley. Average recoveries for zearalenone at 1, 2 and 5 ppm varied from 53% for wheat to 87% for rice.     

Dual-layer hollow fiber of polyaniline–cellulose acetate prepared with simple wet technique of chemical polymerization of aniline

Polyaniline–cellulose acetate hollow fibers prepared from cellulose acetate (CA) solution of aniline (ANI) were founded to show dual layers structure, when wet technique was applied for using syringe injection of the solution to acidic water for ANI polymerization. In this technique, the polymerization of ANI occurred simultaneously by the monomer injection in coagulated CA fibers. Then, the PANI–CA composite fibers were obtained. The formation of the PANI–CA composite fiber was dependent upon HCl concentration and initiator of ammonium persulfate. Especially, when the coagulation time was 1 min, the obtained PANI–CA fibers showed hollowed dual-layer structure having outer layer of PANI and inner layer of CA. Evidence was presented that the dual structure fiber had 40 μm outer layer and 60 μm inner porous layer in their thicknesses. Cyclic voltammograms of the PANI–CA fiber were indicated that the outer layer was composed of PANI layer showing electrochemical properties with electrical capacity of about 0.003 C.     

CsHSO4 as proton conductor for high-temperature polymer electrolyte membrane fuel cells

The influence of CsHSO₄ inorganic solid acid was evaluated as a possible proton conductor in the catalyst layer of ABPBI (poly(2,5-benzimidazole))-based high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Gas diffusion electrodes (GDEs) were prepared with fixed polytetrafluoroethylene (PTFE) and polyvinylidene diflouride (PVDF) binder content, while the CsHSO₄ loading was varied. Porosimetry data showed that the addition of 10 % CsHSO₄ to the PVDF GDE increased the porosity across all the pore regions, whereas the addition of 10 % CsHSO₄ to the PTFE GDE decreased the GDEs porosity. The CsHSO₄ MEAs showed good proton transfer dynamics and low resistance for fuel cell operation. An optimum loading of 10 % CsHSO₄ in conjunction with either of the binders was observed, with CsHSO₄–PVDF GDE achieving peak power of 498.2 mW cm^?2 at a cell voltage of +352 mV. Higher CsHSO₄ loadings increased the charge transfer resistance and lowered the cell performance of these GDEs.     

A comparative study of different microchips for capillary electrophoresis with electrochemical detection

This work describes a comparison of the performance of different microchip configuration for microchip capillary electrophoresis with electrochemical detection. Two electrodes gold and multistrand carbon fibers and two microchip construction materials polydimethylsiloxane/polydimethylsiloxane (PDMS/PDMS) and polydimethylsiloxane/glass hybrid (PDMS/glass) were analyzed. The electrode is integrated into the microchip for in-channel triple pulse amperometric detection. Two different mixtures were analyzed (i.e., paracetamol (PA)-4-aminophenol (4-AP) and Dopamine (DO)-Dopac) to demonstrate the electrode and microchips performance. Other variables, such as injection and separation potentials, buffer pH, surfactants addition and injection time, were also analyzed. Hydrodynamic voltammograms were used to select working potential values, and +0.9 V for PA and 4-AP and +0.8 V for DO and dopac were chosen. The migration potential was modified in the 1,500–2,500 V range, and the employed value depends on the microchip materials. The separation process was tested by analyzing the current and migration time variation coefficients. The experimental results demonstrated that the hybrid PDMS/glass microchip with a carbon fiber electrode exhibited a better performance for both samples analyzed.     

Gel-sol synthesis of surface-treated TiO2 nanoparticles and incorporation with waterborne acrylic resin systems for clear UV protective coatings

Visible transparent UV protective coatings were developed by incorporating nano-TiO₂ into waterborne acrylic systems to provide UV protection for UV-sensitive color cool roofing. Water-based high crystalline TiO₂ nanoparticle suspension was prepared via a gel-sol method at a basic pH. The TiO₂ nanoparticles have an average size of 20 nm and are stable against agglomeration. As-prepared TiO₂ nanosuspension is ready to be well dispersed in commercial waterborne acrylic resin system without extra-surface modification. The fabricated TiO₂/acrylic nanocomposite coating achieved a UV cut-off below 350 nm with a visible transmission greater than 85% at 700 nm. It is also demonstrated by using Rhodamine 6G that surface modification of nano-TiO₂ with a SiO₂ insulation layer would suppress the catalytic activity of nano-TiO₂ and improve the UV protection for UV and photocatalysis sensitive dyes.     

Production and characterization of membranes of recycled waste materials: Cellulose acetate,obtained from sugarcane bagasse with polystyrene from plastics cups

Membranes of cellulose acetate from sugarcane bagasse (CA), as well as blends of this cellulose acetate and polystyrene from plastic cups (CA/PS) were produced by casting utilizing dichloromethane as solvent at the concentration 12% w/w. The membranes were characterized regarding ion diffusion by dialysis and properties of pure water permeation rate, PEG rejection (utilizing an aqueous solution 1% w/v of polyethylene glycol (PEG), 45 and 80 kDa). Thermal characterization by thermogravimetric analysis and differential scanning calorimetry were also performed. The morphology of the membranes' cross‐sections was evaluated by scanning electron microscopy. The experiment of ion diffusion by dialysis showed that the ion diffusion coefficient of CA membrane is comparable to that found in the literature for membranes of commercial cellulose triacetate, 8.47 × 10^?8 cm² s^?1, while the ion diffusion coefficient of blends decreased as PS was added to the system. Regarding transport driven by pressure, CA membrane presented low rejection of PEG 80 kDa. These results showed that CA membrane could be used in a range of application comprehending the process of ultrafiltration or microfiltration. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Urothermal Synthesis of a New Cd(II)-Terephthalate: Synthesis,Structure, CO2 Adsorption and Luminescent Properties

A new Cd(II) compound, namely [Cd(pbdc)(e-urea)]_n (1 H₂pbdc = terephthalic acid, e-urea = ethyleneurea), has been synthesized by urothermal reactions of Cd(NO₃)₂, and H₂pbdc. Single crystal X-ray analysis reveals that it features a three-dimensional framework based on Cd(II)-carboxylate inorganic chains. The coordinated e-urea molecules are filled in the rhombic channels. Thermal analysis reveals that it can be stable up to 350 °C. The CO₂ adsorption and luminescent properties of compound 1 were also investigated.