Long-term drug release from electrospun fibers for in vivo inflammation prevention in the prevention of peritendinous adhesions

Physical barriers such as electrospun fibrous membranes are potentially useful in preventing peritendinous adhesions after surgery. However, inflammatory responses caused by degradation of barrier materials remain a major challenge. This study aimed to fabricate electrospun composite fibrous membranes based on drug-loaded modified mesoporous silica (MMS) and poly (l-lactic acid) (PLLA). Using a co-solvent-based electrospinning method ibuprofen (IBU)-loaded MMS was successfully and uniformly encapsulated in the PLLA fibers. The electrospun PLLA–MMS–IBU composite fibrous membranes showed significantly lower initial burst release (6% release in the first 12 h) compared with that of electrospun PLLA–IBU fibrous membranes (46% release in the first 12 h) in in vitro release tests. Moreover, the release from PLLA–MMS–IBU was also for significantly longer than that from PLLA–IBU (100 vs. 20 days). In animal studies both PLLA–IBU and PLLA–MMS–IBU showed improved anti-adhesion properties and anti-inflammatory effects compared with PLLA fibrous membrane alone 4 weeks after implantation. Further, animals implanted with PLLA–MMS–IBU for 8 weeks showed the lowest inflammation and best recovery compared with those implanted with PLLA–IBU and PLLA, most likely as a result of its long-term IBU release profile. Therefore, this study provides a platform technique for fabricating fibrous membranes with long-term sustained drug release characteristics which may function as a novel carrier for long-term anti-inflammation and anti-adhesion to prevent peritendinous adhesions.     

Tissue anti-adhesion potential of biodegradable PELA electrospun membranes

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric membrane. In this study, a new anti-adhesion membrane from polylactide–polyethylene glycol tri-block copolymer (PELA) has been synthesized. The synthesized copolymers were characterized by gel permeation chromatography and ¹H nuclear magnetic resonance spectroscopy. PELA membrane was prepared by electrospun. The prepared copolymer membranes were more flexible than the control poly-d-l-lactic acid (PDLLA) membrane, as investigated by the measurements of glass transition temperature. Its biocompatibility and anti-adhesion capabilities were also evaluated. In vitro cell adhesions on the PELA copolymer membrane and PDLLA membrane were compared by the culture of mouse fibroblasts L929 on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the PDLLA and PELA copolymer membranes were implanted between cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the PELA copolymer membrane was very effective in preventing cell or tissue adhesion on the membrane surface, probably owing to the effects of hydrophilic polyethylene glycol.     

The influence of Gelatin/PCL ratio and 3-D construct shape of electrospun membranes on cartilage regeneration

Scaffolds play an important role in directing three-dimensional (3-D) cartilage regeneration. Our recent study reported the potential advantages of electrospun gelatin/polycaprolactone (GT/PCL) membranes in regenerating 3-D cartilage. However, it is still unknown whether the changes of GT/PCL ratio have significant influence on 3-D cartilage regeneration. To address this issue, the current study prepared three kinds of electrospun membranes with different GT/PCL ratios (70:30, 50:50, 30:70). Adhesion and proliferation of chondrocytes on the membranes were examined to evaluate biocompatibility of the membranes. Cartilage with different 3-D shapes was engineered to further evaluate the influences of GT/PCL ratio on cartilage regeneration. The current results demonstrated that all the membranes with different GT/PCL ratios presented good biocompatibility with chondrocytes. Nevertheless, the high PCL content in the membranes significantly hampered early 3-D cartilage formation at 3 weeks in vivo. Unexpectedly, at 12 weeks, all the cylinder-shaped constructs formed mature cartilage-like tissue with no statistical differences among groups. To our surprise, ear-shaped cartilage regeneration obtained quite different results again: the high PCL content completely disrupted cartilage regeneration even at 12 weeks, and only the least PCL content group formed homogeneous and continuous cartilage with a satisfactory shape and elasticity similar to human ear. All these results indicated that the high PCL content was unfavorable for 3-D cartilage regeneration, especially for the cartilage with a complicated shape, and that GT/PCL 70:30 might be a relatively suitable ratio for ear-shaped cartilage regeneration. The research models established in the current study provide detailed information for cartilage and other tissue regeneration based on electrospun GT/PCL membranes.     

Evaluation of electrospun PCL/gelatin nanofibrous scaffold for wound healing and layered dermal reconstitution

The current design requirement for a tissue engineering skin substitute is that of a biodegradable scaffold through which fibroblasts can migrate and populate. This artificial "dermal layer" needs to adhere to and integrate with the wound, which is not always successful for the current artificial dermal analogues available. The high cost of these artificial dermal analogues also makes their application prohibitive both to surgeons and patients. We propose a cost-effective composite consisting of a nanofibrous scaffold directly electrospun onto a polyurethane dressing (Tegaderm, 3M Medical) - which we call the Tegaderm-nanofiber (TG-NF) construct - for dermal wound healing. Cell culture is performed on both sides of the nanofibrous scaffold and tested for fibroblast adhesion and proliferation. It is hoped that these studies will result in a fibroblast-populated three-dimensional dermal analogue that is feasible for layered applications to build up thickness of dermis prior to re-epithelialization. Results obtained in this study suggest that both the TG-NF construct and dual-sided fibroblast-populated nanofiber construct achieved significant cell adhesion, growth and proliferation. This is a successful first step for the nanofiber construct in establishing itself as a suitable three-dimensional scaffold for autogenous fibroblast populations, and providing great potential in the treatment of dermal wounds through layered application.     

Composite electrospun nanofibers of reduced graphene oxide grafted with poly(3-dodecylthiophene) and poly(3-thiophene ethanol) and blended with polycaprolactone

In this paper, an effective method was employed for preparation of nanofibers using conducting polymer-functionalized reduced graphene oxide (rGO). First, graphene oxide (GO) was obtained from graphite by Hommer method. GO was reduced to rGO by NaBH₄ and covalently functionalized with a 3-thiophene acetic acid (TAA) by an esterification reaction to reach 3-thiophene acetic acid-functionalized reduced graphene oxide macromonomer (rGO-f-TAAM). Afterward, rGO-f-TAAM was copolymerized with 3-dodecylthiophene (3DDT) and 3-thiophene ethanol (3TEt) to yield rGO-f-TAA-co-PDDT (rGO-g-PDDT) and rGO-f-TAA-co-P3TEt (rGO-g-PTEt), which were confirmed by Fourier transform infrared spectra. The grafted materials depicted better electrochemical properties and superior solubilities in organic solvents compared to GO and rGO. The soluble rGO-g-PDDT and rGO-g-PTEt composites blended with polycaprolactone were fabricated by electrospinning, and then cytotoxicity, hydrophilicity, biodegradability and mechanical properties were investigated. The grafted rGO composites exhibited a good electroactivity behavior, mainly because of the enhanced electrochemical performance. The electrospun nanofibers underwent degradation about 7 wt% after 40 days, and the fabricated scaffolds were not able to induce cytotoxicity in mouse osteoblast MC3T3-E1 cells. The soluble conducting composites developed in this study are utilizable in the fabrication of nanofibers with tissue engineering application.     

Mechanical properties of electrospun bilayer fibrous membranes as potential scaffolds for tissue engineering

Bilayer fibrous membranes of poly(l-lactic acid) (PLLA) were fabricated by electrospinning, using a parallel-disk mandrel configuration that resulted in the sequential deposition of a layer with fibers aligned across the two parallel disks and a layer with randomly oriented fibers, both layers deposited in a single process step. Membrane structure and fiber alignment were characterized by scanning electron microscopy and two-dimensional fast Fourier transform. Because of the intricacies of the generated electric field, bilayer membranes exhibited higher porosity than single-layer membranes consisting of randomly oriented fibers fabricated with a solid-drum collector. However, despite their higher porosity, bilayer membranes demonstrated generally higher elastic modulus, yield strength and toughness than single-layer membranes with random fibers. Bilayer membrane deformation at relatively high strain rates comprised multiple abrupt microfracture events characterized by discontinuous fiber breakage. Bilayer membrane elongation yielded excessive necking of the layer with random fibers and remarkable fiber stretching (on the order of 400%) in the layer with fibers aligned in the stress direction. In addition, fibers in both layers exhibited multiple localized necking, attributed to the nonuniform distribution of crystalline phases in the fibrillar structure. The high membrane porosity, good mechanical properties, and good biocompatibility and biodegradability of PLLA (demonstrated in previous studies) make the present bilayer membranes good scaffold candidates for a wide range of tissue engineering applications.     

Surface modification of polycaprolactone with poly(methacrylic acid) and gelatin covalent immobilization for promoting its cytocompatibility

Polycaprolactone (PCL) membrane was modified by grafting copolymerization of methacrylic acid (MAA) initiated under UV light. The covalent immobilization of gelatin on PCL-g-PMAA surface was consequently performed by using condensing agent, 1-ethyl-3-(3-dimethylamino propyl) carbodiimide hydrochloride. The occurrence of grafting copolymerization of PMAA and further immobilization of gelatin was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy characterizations. The existence of carboxyl groups grafted on PCL surface was verified quantitatively by absorbance spectroscopy where rhodamine 6G was employed to react with carboxyl groups to generate an absorbance at 512 nm. The endothelial cell culture proved that the PCL membrane slightly modified with suitable amount of PMAA or gelatin had better cytocompatibility than control PCL or PCL membrane heavily modified with PMAA or gelatin.     

热处理改善聚乳酸纤维膜力学及细胞阻隔性能

静电纺丝(ES)纳米纤维材料具有与天然细胞外基质相似的形态结构,能很好地支持细胞黏附与生长,是一种理想的组织工程支架,但其力学性能较差,易变形开裂,不能满足引导组织再生(GTR)对于膜机械强度的要求。本文将高速卷绕收集的左旋聚乳酸平行纳米纤维膜(PLLA-ANM)在热空气中进行牵伸及退火处理,以提高膜的抗拉性能和细胞阻隔功能。力学结果表明,在100℃下沿纤维排列方向上牵伸2倍、热定型10 min的膜抗拉性能最好,其抗拉强度(σm)和模量(Et)分别达到了103 MPa和1.83 GPa。体外细胞培养结果显示,牙周膜细胞在热处理后的膜表面黏附和生长状况良好,细胞均沿纤维排列的方向铺展成长梭形,但其增殖速率与无纺纤维膜上的情况相比有所减小。由于热处理后的膜更加致密,细胞仅聚集在膜的表面生长,膜的细胞阻隔性能因此得以明显改善。     

In vitro comparative study of white and dark polycaprolactone trifumarate in situ cross-linkable scaffolds seeded with rat bone marrow stromal cells

OBJECTIVE:

Dark poly(caprolactone) trifumarate is a successful candidate for use as a bone tissue engineering scaffold. Recently, a white polymeric scaffold was developed that shows a shorter synthesis time and is more convenient for tissue-staining work. This is an in vitro comparative study of both the white and dark scaffolds.

METHODS:

Both white and dark poly(caprolactone) trifumarate macromers were characterized via Fourier transform infrared spectroscopy before being chemically cross-linked and molded into disc-shaped scaffolds. Biodegradability was assessed by percentage weight loss on days 7, 14, 28, 42 and 56 (n = 5) after immersion in 10% serum-supplemented medium or distilled water. Static cell seeding was employed in which isolated and characterized rat bone marrow stromal cells were seeded directly onto the scaffold surface. Seeded scaffolds were subjected to a series of biochemical assays and scanning electron microscopy at specified time intervals for up to 28 days of incubation.

RESULTS:

The degradation of the white scaffold was significantly lower compared with the dark scaffold but was within the acceptable time range for bone-healing processes. The deoxyribonucleic acid and collagen contents increased up to day 28 with no significant difference between the two scaffolds, but the glycosaminoglycan content was slightly higher in the white scaffold throughout 14 days of incubation. Scanning electron microscopy at day 1 revealed cellular growth and attachment.

CONCLUSIONS:

There was no cell growth advantage between the two forms, but the white scaffold had a slower biodegradability rate, suggesting that the newly synthesized poly(caprolactone) trifumarate is more suitable for use as a bone tissue engineering scaffold.     

Down-regulating ERK1/2 and SMAD2/3 phosphorylation by physical barrier of celecoxib-loaded electrospun fibrous membranes prevents tendon adhesions

Peritendinous adhesions, as a major problem in hand surgery, may be due to the proliferation of fibroblasts and excessive collagen synthesis, in which ERK1/2 and SMAD2/3 plays crucial roles. In this study, we hypothesized that the complication progression could be inhibited by down-regulating ERK1/2 and SMAD2/3 phosphorylation of exogenous fibroblasts with celecoxib. Celecoxib was incorporated in poly(l-lactic acid)-polyethylene glycol (PELA) diblock copolymer fibrous membranes via electrospinning. Results of an in vitro drug release study showed celecoxib-loaded membrane had excellent continuous drug release capability. It was found that celecoxib-loaded PELA membranes were not favorable for the rabbit fibroblast and tenocyte adhesion and proliferation. In a rabbit tendon repair model, we first identified ERK1/2 and SMAD2/3 phosphorylation as a critical driver of early adhesion formation progression. Celecoxib released from PELA membrane was found to down-regulate ERK1/2 and SMAD2/3 phosphorylation, leading to reduced collagen I and collagen Ⅲ expression, inflammation reaction, and fibroblast proliferation. Importantly, the celecoxib-loaded PELA membranes successfully prevented tissue adhesion compared with control treatment and unloaded membranes treatment. This approach offers a novel barrier strategy to block tendon adhesion through targeted down-regulating of ERK1/2 and SMAD2/3 phosphorylation directly within peritendinous adhesion tissue.     

Surface modification of chitosan membranes by complexation-interpenetration of anionic polysaccharides for improved blood compatibility in hemodialysis

Chitosan membrane surface was modified by cornplexation and interpenetration of anionic polysaccharides - heparin and dextran sulfate - for improved blood compatibility in hemodialysis. Electron spectroscopy for chemical analysis results showed a characteristic sulfur (S) and sodium (Na) peaks after modification with dextran sulfate. The sulfur/carbon (S/C) atomic composition ratio increased from 0.03 to 0.08 when the bulk dextran sulfate concentration used for modification was increased from 2.5 to 10 mg ml^-1 . The permeability of urea and creatinine did not change significantly upon modification with heparin or dextran sulfate. Surface modification, however, did decrease the permeability coefficients of glucose, vitamin B-2, and vitamin B-12. Unlike Cuprophan, chitosan and surface-modified chitosan membranes did not significantly activate the complement system as measured by the serum iC3b concentration. Compared to forty and sixty fully-activated platelets present on control surfaces, surface modification with heparin and dextran sulfate significantly reduced the number of adherent platelets per 25 000 μm² area and the extent of platelet activation. Surface modification with anionic polysaccharides, however, did significantly shorten the plasma recalcification time leading to fibrin clot formation. The results of this study show that chitosan membrane surface can be modified by complexation-interpenetration of anionic modifying agents. The modified membranes do resist complement activation and platelet adhesion and activation.     

稽留流产刮宫术后宫腔粘连的防治方法探讨

目的探讨稽留流产刮宫术后宫腔粘连的防治方法。方法选择稽留流产患者共300例,随机分为两组：研究组160例,刮宫术前使用米非司酮配伍米索前列醇,术后服用妈富隆片1片;对照组140例,手术前后无服药。观察两组手术时间、出血量以及术后月经变化。结果研究组患者手术时间和出血量为（4.1±1.8）min、（16.1±9.4）ml,分别较对照组的（7.9±2.3）min、（37.3±13.6）ml短或少,差异有统计学意义（P〈0.05）;术后阴道流血时间和流血量为（4.68±1.21）d、（43.5±12.6）ml,分别较对照组的（7.65±1.23）d、（57.3±13.4）ml短或少,差异有统计学意义（P〈0.05）;月经复潮时间较对照组早,轻、中度宫腔粘连发生较对照组少,差异均有统计学意义（P〈0.05）。结论稽留流产患者刮宫术前使用米非司酮配伍米索前列醇,术后服用妈富隆,可有效预防宫腔粘连的发生。     

羊膜预防硬膜外粘连的初步研究

目的：观察羊膜预防椎板切除术后硬膜外粘连的作用，寻求预防硬膜外粘连的有效材料和方法。方法：制备椎板切除模型兔60只，依术前随机分组，分别在硬膜外覆盖羊膜（AM组）、几丁糖膜（CHS组）、空白对照组不做任何覆盖（CON组）。于术后2、4、8、12周每组分别处死5只动物，对标本做大体解剖及组织学观察。结果：CON组暴露的硬膜发生广泛粘连，硬膜外腔几乎消失；AM组和CHS组硬膜外瘢痕稀少，硬膜表面光滑，硬膜外形成潜在腔隙，维持了硬膜外的有效空间：不同时间段三组间粘连度评分以AM组最低，CHS组次之，CON组最高，组间比较有显著性差异（P〈0．05）。结论：羊膜能预防硬膜外瘢痕向椎管内延伸，防止硬膜外粘连，是一种能有效预防硬膜外粘连的生物相容性材料；几丁糖膜亦显示了一定的预防硬膜外粘连作用。     

Moderation of postischemic damage to cardiomyocytic membranes with reperfusion solution

Isolated perfused hearts of Wistar rats subjected to total ischemia and reperfusion were used to examine the possibility of moderating damage to cardiomyocyte membranes with reperfusion solution containing l-aspartic acid, d-glucose, and d-mannitol. During the first 5 minutes of reperfusion, this solution significantly improved recovery of the pumping and contractile functions of the heart compared to the control and reduced the release of lactate dehydrogenase and systems generating short-living ROS into the effluent. To the end of reperfusion, the content of ATP and phosphocreatine was higher and the loss of total creatine was lower in hearts perfused with the test solution compared to the control. It is hypothesized that better integrity of the myocyte sarcolemma in hearts perfused with the test solution results from better preservation of macroergic phosphates and inhibition of ROS generation in this solution. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 1, pp. 20–22, January, 2007     

胎膜早破对妊娠结局的影响及干预效果

目的探讨胎膜早破的分娩方式及早期干预效果。方法对2004年1月1日至2005年12月31日在我院住院分娩的1979例产妇资料进行回顾性分析。结果初产妇胎膜早破的发生率较经产妇明显增高(P<0.01),胎膜早破组早产发生率高(P<0.01),两组分娩方式比较无差异(P>0.05),胎膜早破组手术指征中头盆不称的发生率明显高于对照组(P<0.01),两组新生儿窒息、产后出血及产妇感染的发生率均无明显差异(P>0.05)。结论对胎膜早破患者预防性使用抗生素、适时终止妊娠等积极干预措施,可以减少母儿并发症发生。     

探讨影响早产胎膜早破母儿预后的危险因素

目的探讨胎膜早破对早产母儿的影响,以及影响早产儿预后的危险因素。方法对141例除外其它合并症、并发症的早产母儿临床资料进行回顾性分析(85例合并胎膜早破,56例无胎膜早破)。结果(1)78.82%早产胎膜早破发生在孕35w以后。(2)早产胎膜早破组与早产无胎膜早破组相比,母儿并发症无显著差异。(3)早产儿有并发症组、死亡组的新生儿窒息率均明显高于早产儿无并发症组及存活组,且新生儿出生体重、分娩孕周均明显降低。结论早产胎膜早破多发生在孕35w以后,对其进行合理治疗后胎膜早破并不是影响早产母儿预后的主要因素,早产儿并发症、死亡主要与新生儿窒息、出生体重、分娩孕周密切相关。