Polyelectrolyte multilayer films functionalized with peptides for promoting osteoblast functions

Layer-by-layer deposition of polyelectrolyte multilayer (PEM) thin films has recently been applied to biomaterial applications. This simple and versatile technique provides a wide variety of potential utilization by insertion of biomolecules such as cell adhesion peptides. In this work dual peptides containing RGD (a cell-binding domain) and LHRRVKI (a heparin-binding domain) were immobilized onto polystyrene by the PEM technique and the effects on osteoblast cell culture were investigated. These peptides were conjugated to the amino groups of poly(allylamine hydrochloride) and then adsorbed onto the top of a 10 layer poly(allylamine hydrochloride)/poly(acrylic acid) film assembled at either pH 2.0 or pH 6.5. Osteoblasts, isolated from neonatal rat calvariae, were then seeded and cultured on the peptide-conjugated surfaces. We found that the cells adhered and grew better on the RGD-conjugated PEM films. The osteoblasts exhibited a better differentiated phenotype on the pH 2.0 films than the pH 6.5 films with respect to calcium deposition. The incorporation of LHRRVKI did not support cell adhesion, growth and matrix mineral deposition. Our results showed that the efficacy of RGD conjugation on osteoblast behavior was affected by the base PEM film.     

Micropatterned surfaces of PDMS as growth templates for HEK 293 cells

In this paper the easy and reliable preparation of precise micropatterns on PDMS surfaces is described and the growth of HEK 293 cells on those patterns during culture over several days is examined. The first patterning approach described is based on soft-lithography and polyelectrolyte multilayer deposition. Two different soft-lithographic techniques are employed for creating surface patterns of PAH, PSS, untreated and oxidized PDMS. The growth behavior of HEK 293 cells is investigated on all the dual combinations of the four surfaces, and decreasing preference of the cells for the surfaces in the order PAH (–NH₂) > ox-PDMS (–OH) >> PSS (–SO₃ ⁻) > PDMS (–CH₃) is revealed. As the second patterning approach a method is introduced, which allows the deposition of gel droplets in a microarray format utilizing differences in the surface wettability. This concept is new and expected to be very useful for various applications. Finally, a speculative explanation for the different cell spreading behavior is provided considering the interplay between individual cell–surface interactions and a permanent cell tractional force.     

载银多聚赖氨酸-海藻酸钠静电自组装多层膜修饰钛表面及其抗菌研究

目的 利用层层自组装技术在钛表面构建聚L赖氨酸（PLL）-海藻酸钠（ALG）多层膜,并在膜层中导入纳米银颗粒,以评价其杀菌效果。方法 利用层层自组装的方法将带正电荷的PLL与带负电荷的ALG在钛片上交替吸附沉积形成聚电解质多层膜,再用盐诱导相分离技术在多层膜中形成一定尺寸的微孔并在其中包裹纳米银粒子。扫描电子显微镜（SEM）、傅立叶红外光谱（FTIR）和能谱分析（EDX）对表面进行表征。并与变形链球菌共培养,观察对细菌的粘附和杀灭的作用。结果 SEM、FTIR和EDX分析证实：多层膜成功沉积在钛片表面,并且纳米银粒子被包裹于其中。荧光显微镜显示纯钛表面有大量的活细菌,沉积聚电解质多层膜后细菌数量减少,导入纳米银离子之后附着于钛片上的细菌数量更少,并且随着膜层数的增多,银离子含量增加,抗菌效果也增强。SEM结果与荧光结果一致。结论 通过层层自组装的方法在钛金属表面沉积载银PLL-ALG聚电解质多层膜,能抑制细菌的粘附。同时,随着膜层数的增加,银粒子含量增加,抗菌效果增强。     

氖气在聚乙烯醇多层塑料球壳内的渗透性能

采用乳液法结合等离子体涂层制备聚苯乙烯（PS）-聚乙烯醇（PVA）-辉光放电聚合物（GDP）多层塑料空心微球。通过测量不同充气平衡时间和平衡温度下球内气体的总量研究了氖气对塑料球的气体渗透系数。研究表明,当充氖温度为60、70、80、90 ℃时,微球充气平衡的时间分别为70~100 h、50~90 h、30~60 h,20~40 h。室温（25 ℃）时氖气对塑料球的渗透系数为0.5×10-19~2.0×10-19 mol/(m·s·Pa),对于直径300 μm,PVA壁厚2 μm的微球,充Ne后的保气半寿命约3～12 d。当外压为4 MPa,平衡温度为80 ℃时,球内可充氖2.6~3.2 MPa。     

维生素B6氯化钠注射液在多层共挤膜输液袋中的稳定性研究

目的 考察强光照射试验、加速试验和长期试验条件下维生素B6氯化钠注射液在多层共挤膜输液袋中的稳定性,为维生素B6氯化钠注射液优选包装提供依据.方法 分别采用非PVC五层共挤输液用膜制备成多层共挤膜输液袋,多层共挤膜输液袋套外袋充氮和多层共挤膜输液袋套外袋充氮并加吸氧剂3种包装条件,置强光照射,加速试验和长期试验条件下,...     

Interactions of polar lipids with cholesteryl ester multilayers elucidate tear film lipid layer structure

PurposeThe tear film lipid layer (TFLL) covers the tear film, stabilizing it and providing a protective barrier against the environment. The TFLL is divided into polar and non-polar sublayers, but the interplay between lipid classes in these sublayers and the structure-function relationship of the TFLL remains poorly characterized. This study aims to provide insight into TFLL function by elucidating the interactions between polar and non-polar TFLL lipids at the molecular level.MethodsMixed films of polar O-acyl-ω-hydroxy fatty acids (OAHFA) or phospholipids and non-polar cholesteryl esters (CE) were used as a model of the TFLL. The organization of the films was studied by using a combination of Brewster angle and fluorescence microscopy in a Langmuir trough system. In addition, the evaporation resistance of the lipid films was evaluated.ResultsPhospholipids and OAHFAs induced the formation of a stable multilamellar CE film. The formation of this film was driven by the interdigitation of acyl chains between the monolayer of polar lipids and the CE multilayer lamellae. Surprisingly, the multilayer structure was destabilized by both low and high concentrations of polar lipids. In addition, the CE multilayer was no more effective in resisting the evaporation of water than a polar lipid monolayer.ConclusionsFormation of multilamellar films by major tear film lipids suggest that the TFLL may have a similar structure. Moreover, in contrast to the current understanding, polar TFLL lipids may not mainly act by stabilizing the non-polar TFLL sublayer, but through a direct evaporation resistant effect.     

Penetration Profile of Taurine in the Human Skin and Its Distribution in Skin Layers

PURPOSE: To measure in vitro release of taurine from a semisolid standard formulation (amphiphilic cream, DAC) containing 1% taurine, a multi-layer membrane system was used. The content and distribution of taurine in different healthy skin layers (stratum corneum, epidermis and dermis) before (native taurine) and after application of the DAC cream were determined using capillary electrophoresis. METHODS: The release of taurine from the DAC cream was studied using a multilayer membrane system. Due to the high hydrophilic properties of taurine, the artificial model membranes consisted of collodion as matrix and glycerol as the acceptor phase. In order to determine whether taurine shows the potential for dermal penetration a Franz diffusion cell system was used. The distribution of taurine in the skin layers was determined before and after application of the DAC cream followed by the incubation in a Franz diffusion cell. The excised skin sample was cut in horizontal sections using a cryomicrotome. In order to detect taurine, fluorescamine was used as a derivatization agent. RESULTS: Experiments with a multilayer membrane system were performed to verify the release of taurine at different times (1, 2 and 5 h). Approximately 42.5% taurine was released from the semisolid standard formulation, accumulating in the first membrane (17.63%). The native taurine content was quantified in human isolated skin layer before and after the application of the semisolid standard formulation followed by incubation in a Franz-type diffusion cell for 1 and 5 h. No statistically significant difference (p < 0.05) of the taurine content in the skin layers existed between exposure times (1 and 5 h) studied. The highest taurine content was found in the epidermis both before (256.01 microg taurine/g skin layer) and after (555.5 microg taurine/g skin layer) the application of the DAC cream. CONCLUSIONS: The distribution profile of taurine in the skin layers was very similar for the times studied, which suggests that taurine is accumulated in specific cells of the skin. The study suggests that taurine is effectively released from the semisolid standard formulation and can be used for topical application in dermatopharmaceutics.     

A fuzzy clustering neural network architecture for classification of ECG arrhythmias

Accurate and computationally efficient means of classifying electrocardiography (ECG) arrhythmias has been the subject of considerable research effort in recent years. This study presents a comparative study of the classification accuracy of ECG signals using a well-known neural network architecture named multi-layered perceptron (MLP) with backpropagation training algorithm, and a new fuzzy clustering NN architecture (FCNN) for early diagnosis. The ECG signals are taken from MIT-BIH ECG database, which are used to classify 10 different arrhythmias for training. These are normal sinus rhythm, sinus bradycardia, ventricular tachycardia, sinus arrhythmia, atrial premature contraction, paced beat, right bundle branch block, left bundle branch block, atrial fibrillation and atrial flutter. For testing, the proposed structures were trained by backpropagation algorithm. Both of them tested using experimental ECG records of 92 patients (40 male and 52 female, average age is 39.75 +/- 19.06). The test results suggest that a new proposed FCNN architecture can generalize better than ordinary MLP architecture and also learn better and faster. The advantage of proposed structure is a result of decreasing the number of segments by grouping similar segments in training data with fuzzy c-means clustering.