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.     

Kinetics of leucine-lysine peptide adsorption and desorption at -CH3 and -COOH terminated alkylthiolate monolayers

The kinetics of adsorption and desorption of two highly asymmetrical model peptides were studied at methyl- and carboxylic acid-terminated alkylthiolate self-assembled monolayer (SAM) surfaces on gold. The model peptides were leucine-lysine (LK), α-helical (LKα14), and β-strand (LKβ15) peptides that have a well-defined secondary structure with the leucines localized on one side and the lysines on the other side. These secondary structures were previously shown to be maintained after adsorption and to control LK peptide orientation on these surfaces. The kinetics of peptide adsorption were analyzed by surface plasmon resonance as a function of peptide solution concentrations at pH 7.4. Peptide desorption was measured by rinsing with a buffer at various times along the adsorption curve. Both peptides had a saturation coverage of approximately 1 ML (monolayer) on the carboxyl SAM. Both peptides exhibited mostly irreversible binding on both surfaces, but the LKα14 peptide showed some limited reversible binding. Reversibly bound peptides could be in the second adlayer interacting only with peptides in the first layer or peptides interacting with a partially covered adsorption site and therefore not able to fully bind to the SAM surface. The near complete lack of reversible binding for LKβ15 is possibly due to strong peptide-peptide hydrogen bonding in β-sheet structures within the adsorbed layer. For a given dose of either peptide, much less peptide adsorbed on the methyl SAMs. The adsorption rate of irreversibly bound LKα14 on carboxylic acid SAMs was first-order with respect to solution concentration. Both peptides showed nucleation-like adsorption kinetics on the carboxylic acid SAM, indicating that peptide-peptide bonding is needed to stabilize the adsorbed layer. Adsorption on the methyl SAM was much lower in quantity for both peptides and seemed to require prior aggregation of the proteins in solution, at least for LKβ15.     

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.     

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.     

Development and characterization of bamboo gauze fabric coated with polymer and drug for wound healing

The bamboo yarn of Ne 40^s was used for the preparation of the Gauze fabric. The physical properties such as areal density and stiffness of fabrics were measured. The fabric was then scoured and bleached as per the standard procedure using distilled water. Chitosan-sodium alginate, Calcium-sodium alginate polymer and their mixture were coated separately on the gauze structure to improve the antibacterial and wound healing property of the bandage. Scanning electron microscope (SEM) analysis was carried out to observe the uniform distribution of polymers in the samples. The antibiotic drugs were selected based on the antibiotic sensitivity test. The drugs such as Tetracycline hydrochloride (250 mg), Chloramphenicol (250 mg) and Rifampicin (250 mg) were immobilized on the polymer coated fabrics to increase the rate of wound healing and antibacterial activity. The drug loaded samples were subjected to drug release study for about four days in a static condition. The results show that good amount of drug was released during all the four days. Further, the antibacterial activity of the drug loaded and polymer coated samples were evaluated against S. aureus and Proteus bacteria. The results show excellent antibacterial activity.     

Antibacterial properties of PLA nonwoven medical dressings coated with nanostructured silver

In this paper, magnetron sputtering was applied to deposit nano-structured silver films on the surfaces of polylactic acid (PLA) nonwovens, which were used in medical dressings. The influence of the coating thickness of the nano-structured sliver films on the antibacterial property of the nonwovens was studied. The antibacterial properties of the medical dressings were measured by shake flask test. The surface morphology of nano-structured silver films and the grain sizes of silver agglomerates were analyzed by atomic force microscope (AFM). Energy dispersive X-ray (EDX) was employed to analyze the surface elemental compositions. The study revealed that the antibacterial properties were improved as the film thickness increased. AFM images of the coated samples indicated that as the sputtering time prolonged, the film thickness was increased, the film became compacter, and the specific area of the film was also increased. Thus, the release rate of silver ions increased, leading to the improved antibacterial property. It was found that the reduction percentage of both tested bacteria-Staphylococcus aureus and Escherichia coli reached 100 % as the coating thickness exceeded 1 nm.     

Biodegradable tocopherol acetate as a drug carrier to prevent ureteral stent-associated infection

Biomaterial-centred bacterial infections present common and challenging complications with medical implants like ureteral stent which provide substratum for the biofilm formation. Hence the purpose of this study is to make antibacterial stent surface with biodegradable polymer (tocopherol acetate) and anti-infective agents (norfloxacin and metronidazole) using a modified dip-coating procedure. This is done by impregnating the stent pieces in the anti-infective solution (a mixture of norfloxacin-metronidazole and polymer) for uniform surface coating (drug-carrier-coated stents). After coating, agar diffusion test was performed as qualitative test to find out the sensitivity of coated stents against the clinical isolates, Staphylococcus epidermidis and Escherichia coli. Quantitative test was measured by calculating the numbers of adhered bacteria on coated and uncoated stents by incubating the stent pieces in artificial urine. Difference in the number of viable bacteria adhered on the surface of coated and uncoated stents were statistically calculated using chi square test with p < 0.05 considered significant. The stent colonising ability of Staphylococcus epidermidis and Escherichia coli in a controlled environment chamber was determined using two-challenge dose of the isolates by in vitro challenge test. In qualitative test, the zone of inhibition around the coated stents showed sensitivity against the clinical isolates. In quantitative test, the number of adhered bacteria on the surface of coated stents was reduced to a significant level (p < 0.05). The polymer, tocopherol acetate is highly biodegradable in nature. Due to its degrading ability in body tissues, it releases the anti-infective drugs at a constant and sustained rate.     

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.     

Effect of changing coating process parameters in the preparation of antimicrobial-coated silk sutures: An in vitro study

Braided silk sutures were coated using a combination of poly(ε-caprolactone) (PCL) and sulfamethoxazole trimethroprim (SMZ) to investigate their antimicrobial performance. SMZ (2500 μg/ml) was combined with different PCL concentrations, i.e., 2.5 %, 5 %, 7.5 %, and 10 % (w/v). Antimicrobial test results showed that SMZ and PCL-treated silk sutures exhibited increasing antimicrobial efficacy against Gram-negative (Escherichia coli) and -positive bacteria (Staphylococcus aureus) with increasing PCL concentrations. The tensile and knot strength of sutures coated with 10 % PCL were significantly higher than those of sutures coated with 7.5 %, 5 %, and 2.5 % PCL. Treatment with PCL exhibited a positive effect on drug release from the sutures. Significant traits of antibacterial activity were observed up to 4 days after instalment of 10 % PCL-coated silk sutures. Under a scanning electron microscope, untreated silk sutures showed a surface heavily coated with bacteria, whereas treated sutures showed a smooth surface without bacteria. The results of this study indicate that SMZ combined with high concentrations of PCL may afford a suitable antibacterial coating agent for braided silk sutures.     

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.     

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.     

转Bar基因抗除草剂稻谷喂养小鼠的食用安全性评价

以转Bar基因抗除草剂水稻品种Bar 68 -1及其受体品种D68(CK)为材料,将其稻谷配制饲料后饲喂体重在18～24 g的SPF级昆明小鼠,喂养90 d后分别检测小鼠腿肌、肝脏、肾脏、脾脏、小肠中是否含有Bar基因片段及其表达蛋白磷丝菌素乙酰转移酶(PAT),同时检测了小鼠消化道内外源蛋白的消化降解和小肠线粒体基因组(mtDNA)的突变情况.结果表明:饲喂转Bar基因稻谷的实验组小鼠各脏器组织中没有检测到Bar基因片段和其表达的PAT蛋白;外源蛋白PAT在小鼠胃肠道内无耐受性,能够被机体完全消化;小鼠小肠mtDNA的测序结果无异常,没有发现突变位点.说明转基因成分没有在小鼠体内残留或发生转移,也没有导致小鼠肠道基因突变.     

Nanofibrillation of cotton fibers by disc refiner and its characterization

Nanofibrils of cellulose were prepared from short staple cotton by refining process using a lab disc refiner that exerts a combination of shear and frictional forces. The nanofibrils were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). From SEM and AFM, it was found that starting average diameter of the cotton fiber (∼25 μm) was reduced to 242 nm after 30 passes of refining. FTIR analysis revealed the increase in amorphous nature of cotton cellulose due to refining process. Supportively, XRD analysis showed a steady decline in percent crystallinity of the cotton fibers as the cotton fibres were passed through the refiner for more number of passes. Similarly, degree of polymerization (DP) was reduced from 2720 to 740 due to the refining process. Nanofibrils of cellulose from short staple cotton have a huge potential for application in nanofilters and as biodegradable fillers in nanocomposites.     

Fabrication of electrospun antimicrobial nanofibers containing metronidazole using nanospider technology

Nanospider technology as a modified electrospinning technique was used for the fabrication of electrospun nanofibers based on poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend as drug delivery system (DDS) for metronidazole (MTZ) as an antimicrobial drug. Electrospun PVA/PEO/MTZ composite nanofibers were stabilized against disintegration in water by heating in oven at 110°C, or by soaking in isopropyl alcohol for 6 hrs. Incorporation of MTZ into electrospun nanofibers was confirmed by SEM, FT-IR spectra and TGA. The drug release results showed that the burst release was suppressed with stabilized electrospun nanofibers compared with non-stabilized ones. Electrospun PVA/PEO/MTZ composite nanofibers exhibited remarkable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Penicillium notatum and Aspergillus flavus which varies with the species of the tested organisms.     

Sustained Release of Risedronate from PLGA Microparticles Embedded in Alginate Hydrogel for Treatment of Bony Lesions

Background:Inflammatory bone resorption in periodontitis can lead to tooth loss. Systemic administration of bisphosphonates such as risedronate for preventing bone resorption can cause adverse effects. ALG and PLGA microparticles have been studied as drug delivery systems for sustained release of drugs. Therefore, the release pattern of risedronate from PLGA microparticles embedded with ALG was studied as a drug delivery system for sustained release of the drug, which can be used in local administrations. Methods:Risedronate-containing PLGA microparticles were fabricated using double emulsion solvent evaporation technique. Ionic cross-linking method was used to fabricate risedronate-loaded ALG. Risedronate-containing PLGA microparticles were then coated with ALG. The calibration curve of risedronate was traced to measure EE and study the release pattern. SEM imaging was carried out, and cell toxicity was examined using MTT assay. Statistical analysis of data was carried out using SPSS ver. 20 software, via one-way ANOVA and Tukey’s tests. Results:SEM imaging showed open porosities on ALGs. The mean EE of PLGA microparticles for risedronate was 57.14 ± 3.70%. Risedronate released completely after 72 h from ALG, and the cumulative release was significantly higher (p = 0.000) compared to PLGA microspheres coated with ALG, which demonstrated sustained released of risedronate until day 28. Risedronate-loaded ALG showed a significant decrease in gingival fibroblasts cell viability (p < 0.05). Conclusion: Alginate-coated PLGA microspheres could release risedronate in a sustained and controlled way and also did not show cell toxicity. Therefore, they seem to be an appropriate system for risedronate delivery in local applications. Key Words: Alginates, Hydrogels, Polylactic acid-polyglycolic acid copolymer, Risedronic acid     

Preparation and flammability properties of hybrid materials containing phosphorous compounds via sol-gel process

Organic-inorganic hybrid coatings containing phosphoric acid (PA) bonded to the organic-inorganic network were prepared from tetraethoxysilane (TEOS) using a sol-gel process. The effect of sol-gel phosphate-based flame retardant coating on polyacrylonitrile fabric properties (flammability, stiffness, and strength) was investigated. Sample characterization of the coated samples were investigated using differential thermal/thermogravimetric analysis (DTA/TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). The results showed that hybrid coating on the polyacrylonitrile fabrics influenced fabric stiffness, strength, and flammability. And also, flammability of the coated samples after washing cycles was investigated, and the flame retardancy properties of the samples after 10 repeated washings were not completely lost.     

4 种缓控释氮肥的养分释放特征及肥效

水田氮肥利用率通常不到旱地的一半,施用缓控释氮肥是提高水田氮肥利用率的有效措施。以常规施肥为对照,通过动力学模拟,研究水稻田 4 种缓控释氮肥[植物油包膜尿素（PCU）、树脂包膜尿素（JZd）、脲甲醛（UF）、硫包衣尿素（SCU）]的养分释放特征,分析不同缓控释氮肥下水稻的氮素累积吸收量和氮肥利用率。结果表明：（1）4 种缓控释氮素肥料 28 d 的养分累积释放率：JZd（94.5%）＞PCU（63.5%）＞SCU（52.6%）＞UF（22.0%）,在 0~56 d,4 种缓控释氮肥的养分累积释放率均迅速增加;在 70 d 后养分累积释放率趋于稳定;（2）4种不同缓控释氮肥氮素释放符合 Elvoich 方程,氮素的释放速率为：JZd＞PCU＞SCU＞UF;（3）PCU 的氮肥利用率最高,达到 56.8%,比常规施肥处理高 15.2%;其次是 JZd,氮肥利用率最低的是 UF,仅为 33.7%;（4）PCU的产量最高,较常规施肥显著提高了 17.4%。PCU 的氮肥利用率及产量最高,对水田来说是一种较为合适的施肥方式。     

Alginate Hydrogels Coated with Chitosan for Wound Dressing

In this work, a coating of chitosan onto alginate hydrogels was realized using the water-soluble hydrochloride form of chitosan (CH-Cl), with the dual purpose of imparting antibacterial activity and delaying the release of hydrophilic molecules from the alginate matrix. Alginate hydrogels with different calcium contents were prepared by the internal setting method and coated by immersion in a CH-Cl solution. Structural analysis by cryo-scanning electron microscopy was carried out to highlight morphological alterations due to the coating layer. Tests in vitro with human mesenchymal stromal cells (MSC) were assessed to check the absence of toxicity of CH-Cl. Swelling, stability in physiological solution and release characteristics using rhodamine B as the hydrophilic model drug were compared to those of relative uncoated hydrogels. Finally, antibacterial activity against Escherichia coli was tested. Results show that alginate hydrogels coated with chitosan hydrochloride described here can be proposed as a novel medicated dressing by associating intrinsic antimicrobial activity with improved sustained release characteristics.     

Preparation of Durable Antibacterial Cellulose with AgCl Nanoparticles

In this study, a facile method was developed to coat AgCl nanoparticles (NPs) onto knitted cotton fabrics. The AgCl NPs were characterized by ultraviolet absorption spectrum, X-ray diffraction (XRD) and dynamic laser light scattering (DLS). The AgCl NPs were coated onto cotton fabrics through a pad-dry-cure process with the assistance of 1,2,3,4- butanetetracarboxylic acid (BTCA). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ICP-OES analysis and energy-dispersive X-ray spectroscopy (EDX) confirmed that AgCl NPs were successfully coated onto cotton fabrics. The prepared cotton samples exhibited excellent antimicrobial activity against both Gram-positive S. aureus and Gram-negative K. pneumonia bacteria. Rat skin fibroblast cytotoxicity testing demonstrated the treated cotton fabrics to be non-toxic. The washing durability evaluation showed that the antimicrobial function of cotton fabrics was durable to washing. In addition, the wrinkle resistance of the coated cotton fabrics was improved and there was no obvious change in whiteness.     

Composite wound dressing for drug release

Present study is focused on the preparation of two layers composite wound dressing for drug release. The outer layer is made of hydrogel which contains of drug and the core layer is made of fabric. The two layers structure of composite dressing is formed by grafting of polyacrylamide-co-acrylic acid hydrogel on cotton fabric using ammonium per sulphate (APS) as chemical initiator and polyethylene glycol (PEG) as crosslinker. The major factors affecting graft copolymerization of hydrogel on cotton fabric are optimized by varying concentration of monomers & initiator, reaction temperature and addition time of crosslinker. Maximum grafting of hydrogel is obtained at 5 % (w/v) APS and 15 % acrylamide/acrylic acid (1:1 w/w ratio) concentration. The FTIR spectra of composite dressing shows characteristics peak of acrylic acid and acrylamide. The composite wound dressing material is loaded with model drug bovine serum albumin (BSA) and drug release behaviour is studied at different pH. The dressing shows drug release in different pH with maximum release of drug in acidic medium.