Preparation and properties of a chitosan-based carrier of corneal endothelial cells

A novel chitosan-based membrane that was made of hydroxypropyl chitosan, gelatin and chondroitin sulfate was used as a carrier of corneal endothelial cells. The characteristics of the blend membrane, such as transparency, equilibrium water content, permeability, mechanical properties, protein absorption ability, hydrophilicity and surface morphology, were determined. To study the effects of the membrane on cell attachment and growth, rabbit corneal endothelial cells were cultured on this artificial membrane. The biodegradability and biocompatibility of the blend membrane were in vivo evaluated by its implantation into the muscle of the rats. Glucose permeation results demonstrated that the blend membrane had higher glucose permeability than natural human cornea. Scanning electron microscopy (SEM) analysis of the membranes demonstrated that no fibrils were observed. As a result, the optical transparency of the membrane was as good as the natural human cornea. The average value of tensile strength of the membrane was 13.71 MPa for dry membrane and 1.48 MPa for wet membrane. The value of elongation at break of the wet was 45.64%. The cultured rabbit corneal endothelial cells formed a monolayer on the blend membrane which demonstrated that the membrane was suitable for corneal endothelial cells to attach and grow. In addition, the membranes in vivo showed a good bioabsorption property. The mild symptoms of inflammation at sites of treatment could be resolved as the implant was absorbed by the host. The results of this study demonstrated that the hydroxypropyl chitosan-chondroitin sulfate-gelatin blend membrane can potentially be used as a carrier for corneal endothelial cell transplantation.     

角膜内皮细胞载体壳聚糖基共混膜的制备及性质研究

为探讨壳聚糖基共混膜作为组织工程化角膜内皮细胞载体的可行性,制备了羟乙基壳聚糖/明胶/硫酸软骨素共混膜,并评价其性质。结果表明该膜片具有良好的透明度,适宜的含水量;细胞毒性0～1级;体外培养的角膜内皮细胞能够很好地贴附和生长于共混膜上;植入大鼠肌肉内,能够稳定地降解,诱发的炎症反应明显低于不可降解手术缝合线,说明该膜片具有良好的组织相容性,有望作为角膜细胞载体构建组织工程化角膜。     

壳聚糖-硫酸软骨素共混膜性质的研究

以溶液共沸法制成不同共混比例的壳聚糖－硫酸软骨素共混膜,通过观察共混膜的表面形态结构、结晶度、红外吸收及透光率,发现壳聚糖和硫酸软骨素两种分子具有较好的相容性,分子间具有较强的相互作用,所形成的共混膜表面结构均匀单一。通过研究共混膜的各种性质发现硫酸软骨素的混入可以改善膜的力学特性,提高膜的透光性及渗透性,降低膜的吸水性及对蛋白的吸附性。以共混膜为载体培养兔角膜内皮细胞,发现硫酸软骨素的引入可明显提高膜和细胞的相容性,兔角膜内皮细胞可在膜上长期生长,结果提示此共混膜可作为细胞培养的良好载体,用于器官损伤修复及细胞移植。     

壳聚糖-透明质酸共混膜性质的研究

以溶液共混法制成不同比例的壳聚糖一透明质酸共混膜,通过观察各种共混膜的表面形态结构、结晶度、透光率等,发现在以较低比例混入透明质酸所形成的共混膜中两种高分子的相容性较好,分子间存在较强的相互作用力,形成的共混膜表面结构均匀单一。通过对共混膜理化性质的研究,发现透明质酸的混入可以有效的改变壳聚糖膜的力学特性、吸水性、吸附性以及对小分子物质的渗透性。以共混膜和壳聚糖膜为载体培养兔角膜细胞,结果发现较低比例的透明质酸可以显著提高壳聚糖膜与角膜细胞的相容性,能够有效的支持细胞在膜上生长,结果提示以一定共混比例制成的壳聚糖一透明质酸共混膜可以作为细胞体外培养的良好载体,可用于器官损伤修复以及细胞移植。     

Tissue-engineered membrane based on chitosan for repair of mechanically damaged corneal epithelium

In this study, hydroxyethyl chitosan (HECTS), a water-soluble derivative of chitosan, was used to create a blend membrane and its function and application as a scaffold in repair of mechanically damaged corneal epethelia were examined. The results showed that HECTS significantly promoted growth of corneal epithelial cells (CEpCs) in vitro and that CEpCs grew well on the HECTS-based blend membrane. Fluorescent imaging showed that CEpCs were interconnected and formed layers on the membrane. After transplanting the CEpCs-seeded membranes onto the damaged corneal epithelium, we found that the epithelium was repaired faster compared with control. The repaired corneal epithelium with the membrane had a more compact structure and a smoother surface than control when observed by histology and scanning electron microscope. These results demonstrate an ability of the tissue-engineered scaffold to speed up the repair of mechanically damaged corneal epithelium.     

Hydrogel membranes based on genipin-cross-linked chitosan blends for corneal epithelium tissue engineering

Novel polymeric hydrogel scaffolds for corneal epithelium cell culturing based on blends of chitosan with some other biopolymers such as hydroxypropylcellulose, collagen and elastin crosslinked with genipin, a natural substance, were prepared. Physicochemical and biomechanical properties of these materials were determined. The in vitro cell culture experiments with corneal epithelium cells have indicated that a membrane prepared from chitosan-collagen blend (Ch-Col) provided the regular stratified growth of the epithelium cells, good surface covering and increased number of the cell layers. Ch-Col membranes are therefore the most promising material among those studied. The performance of Ch-Col membranes is comparable with that of the amniotic membrane which is currently recommended for clinical applications.     

Corneal critical barrier against the penetration of dexamethasone and lomefloxacin hydrochloride: evaluation by the activation energy for drug partition and diffusion in cornea

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approch to investigate the mechanism of drug permeability.     

Corneal Critical Barrier against the Penetration of Dexamethasone and Lomefloxacin Hydrochloride: Evaluation by the Activation Energy for Drug Partition and Diffusion in Cornea

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approch to investigate the mechanism of drug permeability.     

Preparation and properties of a drug release membrane of mitomycin C with <Emphasis Type="Italic">N</Emphasis>-succinyl-hydroxyethyl chitosan

A novel drug loaded membrane made of N-succinyl-hydroxyethyl chitosan and mitomycin C was used as an implant for glaucoma filtering surgery. The characteristics of the membrane, such as FTIR, equilibrium water content, swelling ratio, permeability, and drug release in vitro were determined. The L929 fibroblast inhibition of drug loaded membranes was compared to hydroxyethyl chitosan film and blank control, detecting by MTT. The biodegradability and biocompatibility were evaluated by implanting membranes into the subcutaneous tissue and muscle of rats. FTIR indicated mitomycin C was introduced. The experimental results indicated the drug loaded membrane was effective on the swelling property, permeability, and drug release in vitro. Cell culture experimental results demonstrated that the destination membrane inhibited fibroblast proliferation. In vivo, the membranes showed bioabsorption and biocompatibility. The experimental results provide a theoretical basis for the future development of the drug loaded membrane as an implant for increasing the success rate of filtering surgery.     

SPPESK/SPEEK共混质子交换膜的制备与性能

以耐溶胀性能较好的磺化聚芳醚砜酮(SPPESK)和吸水性较强的磺化聚醚醚酮(SPEEK)为原料,制备了SPPESK/SPEEK共混质子交换膜。考察了共混膜的水吸收率,水溶胀度,甲醇水溶胀度,甲醇渗透率及质子传导率和力学性能。80℃时,共混膜具有适当的水吸收(101%)和溶胀度(34%),较低的甲醇水溶胀度(20%),较高的质子传导率(0.212 S/cm),与SPPESK膜相比,质子传导率提高了18%。SPEEK的加入改善了共混膜的柔韧性,断裂拉伸应变从16.48%提高到30.43%。     

Smartphone-based imaging of the corneal endothelium at sub-cellular resolution

This aim of this study was to test the feasibility of smartphone-based specular microscopy of the corneal endothelium at a sub-cellular resolution. Quantitative examination of endothelial cells is essential for evaluating corneal disease such as determining a diagnosis, monitoring progression and assessing treatment. Smartphone-based technology promises a new opportunity to develop affordable devices to foster quantitative examination of endothelial cells in rural and underserved areas. In our study, we incorporated an iPhone 6 and a slit lamp to demonstrate the feasibility of smartphone-based microscopy of the corneal endothelium at a sub-cellular resolution. The sub-cellular resolution images allowed quantitative calculation of the endothelial cell density. Comparative measurements revealed a normal endothelial cell density of 2978 cells/mm² in the healthy cornea, and a significantly reduced cell density of 1466 cells/mm² in the diseased cornea with Fuchs’ dystrophy. Our ultimate goal is to develop a smartphone-based telemedicine device for low-cost examination of the corneal endothelium, which can benefit patients in rural areas and underdeveloped countries to reduce health care disparities.     

Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea

Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt.     

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)—the effect of biomolecular ligands to balance cell adhesion and stimulated detachment

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(N-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment. To illustrate the strength of this approach, the novel cell culture carrier was applied to generate transplantable sheets of human corneal endothelial cells (HCEC). Sheets were grown, detached, and transferred onto planar targets. Cell morphology, viability and functionality were analyzed by immunocytochemistry and determination of transepithelial electrical resistance (TEER) before and after sheet detachment and transfer. HCEC layers showed regular morphology with appropriate TEER. Cells were positive for function-associated marker proteins ZO-1, Na⁺/K⁺-ATPase, and paxillin, and extracellular matrix proteins fibronectin, laminin and collagen type IV before and after transfer. Sheet detachment and transfer did not impair cell viability. Subsequently, a potential application in ophthalmology was demonstrated by transplantation onto de-endothelialized porcine corneas in vitro. The novel thermo-responsive cell culture carrier facilitates the generation and transfer of functional HCEC sheets. This paves the way to generate tissue engineered human corneal endothelium as an alternative transplant source for endothelial keratoplasty.     

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)—the effect of biomolecular ligands to balance cell adhesion and stimulated detachment

Abstract

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(N-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment. To illustrate the strength of this approach, the novel cell culture carrier was applied to generate transplantable sheets of human corneal endothelial cells (HCEC). Sheets were grown, detached, and transferred onto planar targets. Cell morphology, viability and functionality were analyzed by immunocytochemistry and determination of transepithelial electrical resistance (TEER) before and after sheet detachment and transfer. HCEC layers showed regular morphology with appropriate TEER. Cells were positive for function-associated marker proteins ZO-1, Na⁺/K⁺-ATPase, and paxillin, and extracellular matrix proteins fibronectin, laminin and collagen type IV before and after transfer. Sheet detachment and transfer did not impair cell viability. Subsequently, a potential application in ophthalmology was demonstrated by transplantation onto de-endothelialized porcine corneas in vitro. The novel thermo-responsive cell culture carrier facilitates the generation and transfer of functional HCEC sheets. This paves the way to generate tissue engineered human corneal endothelium as an alternative transplant source for endothelial keratoplasty.     

新型五孔PVDF共混改性膜抗污染性能研究

观察新型五孔PVDF共混改性纤维膜SEM形貌特征,测量改性膜的接触角和临界通量,1#(PVDF/PMMA/TPU)、2#(PVDF/PMMA/PVC)共混改性膜分别在次临界和超临界通量下进行过滤实验.结果表明:PVDF共混改性膜具有优良的微观结构,且1#共混膜性能较好;1#共混膜的接触角比2#共混膜小;1#、2#共混膜的临界通量分别为10和14L/(m2.h);1#共混膜比2#共混膜抗污染性能好;次临界通量下共混膜的运行比超临界通量下的稳定.两种共混膜分别在次临界通量下采用单独超滤和混凝+超滤工艺处理某市地表水,得出混凝+超滤工艺处理效果较好,且1#共混膜比2#共混膜处理效果好.     

木薯淀粉/壳聚糖可食共混膜的制备及在草莓保鲜中的应用

以木薯淀粉、壳聚糖为基材,制备用于草莓保鲜的可食共混膜,研究共混比、抗菌剂(柠檬酸)和表面活性剂(吐温60)对共混膜性能及保鲜效果的影响。结果表明:当壳聚糖和木薯淀粉质量比为1:1时,共混膜的拉伸强度为25 MPa,断裂伸长率为10.6%,水蒸气渗透率为160 g/(24 h·m2),其综合性能最佳。当添加质量分数为4%的柠檬酸时,共混膜综合性能较好;当同时添加质量分数为1%的吐温60与1%的柠檬酸时,60 h后的草莓失重率比单独添加质量分数为1%的柠檬酸和1%的吐温60分别降低约20%和15%,说明此时保鲜效果最佳。     

Effect of the sterilization method on the properties of Bombyx mori silk fibroin films

We have compared the effects of different sterilization techniques on the properties of Bombyx mori silk fibroin thin films with the view to subsequent use for corneal tissue engineering. The transparency, tensile properties, corneal epithelial cell attachment and degradation of the films were used to evaluate the suitability of certain sterilization techniques including gamma-irradiation (in air or nitrogen), steam treatment and immersion in aqueous ethanol. The investigations showed that gamma-irradiation, performed either in air or in a nitrogen atmosphere, did not significantly alter the properties of films. The films sterilized by gamma-irradiation or by immersion in ethanol had a transparency greater than 98% and tensile properties comparable to human cornea and amniotic membrane, the materials of choice in the reconstruction of ocular surface. Although steam-sterilization produced stronger, stiffer films, they were less transparent, and cell attachment was affected by the variable topography of these films. It was concluded that gamma-irradiation should be considered to be the most suitable method for the sterilization of silk fibroin films, however, the treatment with ethanol is also an acceptable method.     

Hyperfast Water Transport through Biomimetic Nanochannels from Peptide‐Attached (pR)‐pillar[5]arene

Synthetic water channels offer great promise to replace natural aquaporins (AQPs) for making new‐generation biomimetic membranes for water treatment. However, the water permeability of the current synthetic water channels is still far below that of AQPs. Here, peptide‐attached (pR)‐pillar[5]arene (pR‐PH) channels are reported to mimic the high permeability of AQPs. It is demonstrated that the pR‐PH channels with an open pore can transport water smoothly and efficiently. The pR‐PH channels are competitive with AQPs in terms of water permeability and are much superior to diastereomer peptide‐attached (pS)‐pillar[5]arene (pS‐PH) and other reported synthetic water channels. The exceptional water‐transport properties of the pR‐PH channels are further demonstrated in a composite polymeric membrane that incorporates the nanochannels into the top selective layer. This membrane gives a significantly improved water flux while retaining high salt rejection. The results establish a tangible foundation for developing highly efficient artificial water channel‐based biomimetic membrane for water purification applications.     

微纤化纤维素/聚乳酸薄膜的制备及性能分析

目的将微纤化纤维素(MFC)和聚乳酸(PLA)共混成膜,以提高薄膜的透湿、透氧、阻光等性能,满足果蔬等食品的包装要求。方法采用酶解法与机械处理的方法制备MFC,使用硅烷偶联剂KH560对MFC进行疏水改性处理,再将改性处理的微纤化纤维素(MFC-S)与PLA共混制成薄膜。结果当MFC-S的质量分数为0.75%时,MFC-S/PLA共混包装膜的拉伸强度比纯PLA膜增加了13.3%,当MFC-S的质量分数为2%时,MFC-S/PLA共混包装膜的透氧系数为纯PLA膜的1.43倍,透湿系数为纯PLA膜的1.26倍,透光率降低了60%,阻光效果较好。结论 MFC-S的质量分数为0.75%时,包装膜的拉伸强度较好;MFC-S的质量分数为2%时,透氧、透湿、阻光性较好。     

PAN/CA共混复合膜的气体分离与力学性能

聚丙烯腈（PAN）具有较高的气体渗透性,但拉伸强度低,不适宜直接制膜。为达到气体分离膜在力学强度方面的使用要求,利用PAN与乙酸纤维素（CA）共混改善其拉伸性能。结果表明,采用相转化法制备的PAN/CA共混基膜,随着CA与PAN共混比的增加,拉伸强度有明显的上升趋势,由1.74MPa增加到2.08MPa。当共混比为0....