Controlling the release of bFGF from silk fibroin membrane.

Since neurotrophic factor is easy to degrade and aggregate, it usually has a short half-life in vitro. To overcome this shortage, neurotrophic factor has been combined with the silk fibroin (SF) membrane to realize less degradation, optimal loading efficiency, sustained release, and good adsorption. By optimizing its binding conditions, main parameters were investigated and its optimal loading efficiency was obtained. bFGF was combined to SF membrane by layer by layer (LbL) static adsorption technique. The natural and nontoxic chondroitin sulfate (CS) was used as a crosslinking agent. Optimization was carried out in three aspects: the concentration of bFGF, the concentration of CS, and the reaction time. This experiment provides a better environment for the growth of cells and offers a new kind material of absorbing neurotrophic factor to meet increasing demand for biological materials.

[In vitro effect of total flavones of Fructus Chorspondiatis on expression of collagen type I and type III mRNA and protein of cultured rat cardiac fibroblasts].

This study aims to investigate the effect of total flavones of Fructus Chorspondiatis (TFFC) on the mRNA and protein expression of collagen type I and III of rat cardiac fibroblasts (CFs) induced by angiotensin II (Ang II), and explore its anti-myocardial fibrosis molecular mechanism. Neonatal rat CFs were prepared from Sprague-Dawley rats (1-3 d after birth). The expression of collagen type I and III mRNA and protein were measured by RT-PCR and Western blotting, respectively. The study showed that stimulation of neonatal rat CFs with 100 nmol.L-1 of Ang II for 72 h resulted in a significant increase of the expression of collagen type I and III mRNA and protein. The changes on the expression level were blocked by TFFC. The results demonstrated that TFFC can inhibit myocardial fibrosis induced by Ang II in rats, which is probably associated with the collagen type I and III mRNA and protein levels up-regulated by Ang II, and TFFC was shown to decrease the expression levels of collagen type I and III mRNA and protein.

Highly efficient gel-state dye-sensitized solar cells prepared using poly(acrylonitrile-co-vinyl acetate) based polymer electrolytes.

Poly(acrylonitrile-co-vinyl acetate) (PAN-VA) is utilized as a gelation agent to prepare gel-state electrolytes for dye-sensitized solar cell (DSSC) applications. Based on the synergistic effect of PAN-VA and TiO(2) fillers in the electrolyte, the gel-state DSSC can achieve a conversion efficiency higher than that of a liquid counterpart. The high performance of the gel-electrolyte is attributed to the in situ gelation property of the gel-electrolyte, the contribution of the PAN-VA to the charge transfer, as well as the enhancement effect of TiO(2) fillers on the charge transfer at the Pt-electrolyte interface. The experimental results show that the efficiencies of the gel-state cells have little dependence on the conductivity of the electrolytes with various contents of PAN-VA, but are closely related to the penetration situation of the electrolyte in the TiO(2) film. For PAN-VA concentrations ≤15 wt%, the electrolyte can be easily injected at room temperature based on its in situ gelation property. For higher PAN-VA concentrations, good penetration of the high viscous electrolyte can be achieved by elevating the operation temperature. By utilizing a heteroleptic ruthenium dye (coded CYC-B11), gel-state DSSCs with an efficiency of above 10% are obtained. Acceleration tests show that the cell is stable under one-sun illumination at 60 °C.

Divergent effects of cholesterol on the structure and fluidity of liposome and catanionic vesicle membranes.

Lipid-like ion-pair amphiphile vesicles, or catanionic vesicles, have emerged as potential drug carriers. The effects of cholesterol on the properties of catanionic vesicles have yet been systematically studied. Here, we compared the effects of cholesterol on the structures and fluidities of dipalmitoylphosphatidylcholine liposomes and catanionic vesicles with similar main transition temperatures (Tm ). For liposomes, fluorescence anisotropy (FA) thermograms reveal typical condensing and disordering effects of cholesterol above and below Tm respectively. In contrast, FA and molecular simulation data reveal that catanionic bilayers below Tm are more fluidic due to shorter alkyl chains. This leads to only condensing effects of cholesterol for catanionic vesicles at all temperatures. Our results provide important insights into the fabrication of catanionic vesicles as novel drug carriers.

Stable Ethosome-like Catanionic Vesicles for Transdermal Hydrophilic Drug Delivery with Predictable Encapsulation Efficiency.

Lipid-like pseudo-double-chained catanionic surfactants have emerged as the attractive materials to prepare potential vesicular carriers in drug and gene delivery applications. In particular, the semi-spontaneous process has been developed to fabricate ethosome-like catanionic vesicles for the transdermal drug delivery. In this work, Arbutin (a water-soluble drug) encapsulation efficiency of ethosome-like catanionic vesicles fabricated from decyltrimethylammonium-tetradecylsulfate (DeTMA-TS, CH3(CH2)9 N(CH3)3-CH3(CH2)13SO4) and decyltrimethylammonium-dodecylsulfate (DeTMA-DS, CH3(CH2)9N(CH3)3-CH3(CH2)11SO4) with various amounts of ethanol and cholesterol in tris buffer solution was experimentally determined. A simple unilamellar vesicle (ULV) model, resulting in the theoretical encapsulation efficiency within ±10% error for most vesicle compositions, was also developed. Such agreement indirectly confirmed the formation of unilamellar vesicles by the preparation method. Stable ethosome-like catanionic vesicles by using catanionic surfactants with the aid of suitable amounts of ethanol and cholesterol, which led to polydispersity index (PDI) values of vesicle size distribution less than 0.3, were successfully prepared and their hydrophilic drug encapsulation efficiencies can be accurately predicted. Furthermore, the linear correlations of the trap volume ratio with both vesicle size and concentration of the extra added CHOL also provide important guidelines for controlling the drug loading of ethosome-like catanionic vesicles. The accomplishments reached for the novel vesicles are useful for developing their transdermal drug delivery applications.

Gelation of charged catanionic vesicles prepared by a semispontaneous process.

Various stable charged catanionic vesicles with mean zeta-potential values from +59 mV to -96 mV were successfully prepared from an ion-pair amphiphile (dodecyltrimethylammonium-dodecylsulfate, DTMA-DS) and different amounts of the component ionic surfactants (dodecyltrimethylammonium bromide and sodium dodecyl sulfate) by using a simple semispontaneous process with the aid of cosolvent (1-propanol) addition in water. With the ensuring positively and negatively charged catanionic vesicles, gelation of them by four water-soluble polymers with various charge and hydrophobic characteristics was systematically studied by the tube inversion and rheological characteristic analyses. Four phase maps, which show regions of phase separation, viscous solution, and gel by varying the vesicle composition and polymer content, were thereby constructed. Furthermore, the experimental results of the relaxation time and the storage modulus at 1 Hz for the viscous solutions and gel samples revealed that the interactions at play between charged catanionic vesicles and the water-soluble polymers are of electrostatic and hydrophobic origin. The phase maps and the rheological properties obtained for mixtures of charged catanionic vesicles and polymers may provide useful information for the potential application of catanionic vesicles in mucosal or transdermal delivery of drugs.

[The application of circular stapler in extraperitoneal colostomy].

OBJECTIVE: To evaluate the clinical and application value of circular stapler in extraperitoneal colostomy. METHODS: Retrospective analysis was made to 22 cases that experienced extraperitoneal colostomy with circular stapler from Match 2008 to March 2009 in the department of colon and anal surgery of the first hospital of Jilin University. RESULTS: The length of surgery was (15 +/- 5) min when circular stapler- assisted extraperitoneal colostomy was used, and all of the colostomies were successfully completed during the first procedure. No complications occurred after surgery, such as stoma bleeding, necrosis, infection, retraction, stenosis, intestinal obstruction and hernia beside the stoma etc. Colostomy size of the uniform, beautiful shape formation. Although there were three cases requiring hemostasis due to anastomotic bleeding that occurred during the operation. About 3 months later, staples of the stoma fell off by themselves. All patients were followed up for 6 to 24 months after operation, form and function of colostomy are well. CONCLUSION: The popularization of the application of circular stapler in extraperitoneal colostomy is important and worthwhile for its obvious advantages such as simple operation, good stoma appearance and reduced complications.

Protective effect of S-nitrosoglutathione pretreatment on acute lung injury in septic rats.

OBJECTIVES: To investigate the protective effect of S-nitrosoglutathione (SNG) pretreatment on acute lung injury (ALI) in septic rats. MATERIALS AND METHODS: We constructed a rat model of sepsis by cecal ligation and perforation (CLP), and randomly divided into Sham, CLP, and CLP+SNG (0.25 and 0.5 mg/kg) groups. We used H&E staining and lung wet/dry ratio to assess the severity of lung injury, detected the levels of protein and cells in bronchoalveolar lavage fluid (BALF) and the levels of TNF-α, IL-1ß, TLR4 mRNA, and NF-κB p65 mRNA in the lung tissue, and assessed the levels of glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase in the lung tissue. RESULTS: A rat model of sepsis was successfully constructed by CLP, and pretreatment of SNG significantly increased the survival of septic rats (P<0.001) and decreased the lung tissue injury scores (P<0.001) and lung wet/dry ratio (P<0.01) in a dose-dependent manner. Furtherly, SNG pretreatment significantly reduced the number of total cells, total protein, neutrophils, and lympholytes (all P<0.001) in BALF, and which also decreased the levels of TNF-α, IL-1ß, TLR4 mRNA, and NF-κB p65 mRNA (all P<0.001) in the lungs of CLP-induced rats. Moreover, pretreatment of SNG significantly increased the levels of anti-oxidant enzymes GSH, SOD, GSH-Px, and catalase (all P<0.001) in the lung tissue of septic rats. CONCLUSION: SNG pretreatment has a protective effect on ALI in septic rats, and the specific mechanism may be related to anti-endotoxic, anti-inflammatory, and anti-oxidative properties.

Diagnostic value of miR-155 for acute lung injury/acute respiratory distress syndrome in patients with sepsis.

OBJECTIVE: We aimed to investigate the diagnostic value of microRNA-155 (miR-155) for acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) in patients with sepsis. METHODS: In this prospective study, we used Spearman correlation analysis to investigate relationships between miR-155 expression and inflammatory factors, oxygenation ratio (PaO2/FiO2), and ALI/ARDS score, and used area under the receiver operating characteristic curve (AU-ROC) to evaluate miR-155's diagnostic accuracy for ALI/ARDS in patients with sepsis. RESULTS: In total, 156 patients with sepsis were enrolled in our study, of which 41 had ALI and 32 had ARDS. miR-155 expression in plasma of patients with sepsis and ALI/ARDS was significantly higher than that of patients with sepsis but no ALI/ARDS. The miR-155 level in patients with sepsis and ALI/ARDS was positively correlated with interleukin (IL)-1ß and tumor necrosis factor (TNF)-α levels and ALI/ARDS score, but negatively correlated with PaO2/FiO2. The AU-ROC of plasma miR-155 for diagnosis of sepsis with ALI/ARDS was 0.87, and plasma miR-155, IL-1ß, and TNF-α had high sensitivity and specificity for the diagnosis of sepsis with ALI/ARDS. CONCLUSION: miR-155 is highly expressed in plasma of patients with septic ALI/ARDS; it is positively correlated with lung function and can be used for early diagnosis.

Proteomic profiling and identification of significant markers from high-grade osteosarcoma after cryotherapy and irradiation.

Biological reconstruction of allografts and recycled autografts have been widely implemented in high-grade osteogenic sarcoma. For treating tumor-bearing autografts, extracorporeal irradiation (ECIR) and liquid nitrogen (LN) freezing techniques are being used worldwide as a gold standard treatment procedure. Both the methods aim to eradicate the tumor cells from the local recurrence and restore the limb function. Therefore, it is essential and crucial to find, and compare the alterations at molecular and physiological levels of the treated and untreated OGS recycled autografts to obtain valuable clinical information for better clinical practice. Thus, we aimed to investigate the significantly expressed altered proteins from ECIR-and cryotherapy/freezing- treated OGS (n = 12) were compared to untreated OGS (n = 12) samples using LC-ESI-MS/MS analysis, and the selected proteins from this protein panel were verified using immunoblot analysis. From our comparative proteomic analysis identified a total of 131 differentially expressed proteins (DEPs) from OGS. Among these, 91 proteins were up-regulated (2.5 to 3.5-folds), and 40 proteins were down-regulated (0.2 to 0.5 folds) (p < 0.01 and 0.05). The functional enrichment analysis revealed that the identified DEPs have belonged to more than 10 different protein categories include cytoskeletal, extracellular matrix, immune, enzyme modulators, and cell signaling molecules. Among these, we have confirmed two potential candidates' expressions levels such as Fibronectin and Protein S100 A4 using western blot analysis. Our proteomic study revealed that LN-freezing and ECIR treatments are effectively eradicating tumor cells, and reducing the higher expressions of DEPs at molecular levels which may help in restoring the limb functions of OGS autografts effectively. To the best of our knowledge, this is the first proteomic study that compared proteomic profiles among freezing, ECIR treated with untreated OGS in recycled autografts. Moreover, the verified proteins could be used as prognostic or diagnostic markers that reveal valuable scientific information which may open various therapeutic avenues in clinical practice to improve patient outcomes.

Resveratrol attenuates thromboxane A2 receptor agonist-induced platelet activation by reducing phospholipase C activity.

Resveratrol (3,5,4'-trihydroxystilbene) is a naturally occurring compound shown to decrease the incidence of thromboembolic disease. Although considerable data are available as to the inhibitory effect of resveratrol on the platelet aggregation and thrombopoiesis in human, its underlying mechanism, at the cellular level, has not been rigorously studied. In this experiment, we studied the effect of resveratrol and 1-[6-[[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione, a phospholipase C inhibitor (U-73122) on the thromboxane A2 receptor agonist (9,11-dideoxy-11 alpha,9 alpha-epoxymethanoprostaglandin F(2 alpha), U46619)-induced platelet aggregation, platelet P-selectin expression, and the activity of phospho-phospholipase C beta 3 (P-PLC beta 3) and total-phospholipase C beta 3 (T-PLC beta 3), which play key roles in the signal transduction system of platelet in human. It was found that resveratrol blocked platelet aggregation and platelet P-selectin expression induced by U46619 in a concentration-dependent manner. U-73122 and resveratrol had additive effect in inhibiting platelet aggregation and platelet P-selectin expression. Resveratrol (final concentration was 50 microM) could reduce the ratio of P-PLC beta 3 to T-PLC beta 3. Taken together, these results show that resveratrol suppresses U46619-induced platelet aggregation and P-selectin expression partly through the decrease of the activity of phospholipase C beta of platelets.

Langmuir monolayer behavior of an ion pair amphiphile with a double-tailed cationic surfactant.

The spread or Langmuir monolayer behavior of an ion pair amphiphile (IPA), hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), with a double-tailed cationic surfactant, dihexadecyldimethylammonium bromide (DHDAB), at the air/water interface was analyzed with surface pressure-area isotherms, area relaxation curves, and Brewster angle microscope (BAM) images. The surface pressure-area isotherms showed that with increasing the DHDAB molar ratio, X(DHDAB), spread monolayers of HTMA-DS with DHDAB became rigid. In addition, unreasonably small limiting areas per alkyl chain of the molecules in the monolayers were found, especially at X(DHDAB)=0.5, implying the molecular loss from the monolayers at the interface. For spread HTMA-DS/DHDAB monolayers at the interface, a new IPA, DHDA-DS, was proposed to form through the displacement of HTMA(+) from HTMA-DS by DHDA(+), leaving HTMA(+) dissociated. The formation of DHDA-DS and the desorption of dissociated HTMA(+) upon the interface compression were supported by the results obtained from designed monolayer experiments with BAM observations, and were discussed by considering the hydrophilicity, packing efficiency, and headgroup charge characteristic of the species. Moreover, the area relaxation curves of spread HTMA-DS/DHDAB monolayers suggested that the formation of DHDA-DS was strongly related to the improved monolayer stability at the interface, which may have implications for the DHDAB-enhanced physical stability of catanionic vesicles composed of HTMA-DS.

Resveratrol attenuates adenosine diphosphate-induced platelet activation by reducing protein kinase C activity.

Inappropriate platelet activation is the key point of thrombogenesis. The aim of the present study was to investigate the effects of resveratrol (RESV), a compound extracted from the Chinese medicinal herb Polygonum cuspidatum sieb et Zucc, on the platelet activation induced by adenosine diphosphate (ADP) and its possible mechanism. The percentage of platelet aggregation and surface P-selectin-positive platelets, and the activity of protein kinase C (PKC) of platelet were observed with platelet aggregometer, flow cytometry and phosphorimaging system, respectively. RESV at 25, 50 and 100 microM showed anti-platelet aggregation and inhibition of surface P-selectin-positive platelets in a concentration-dependent manner. RESV (50 microM) inhibited the activity of PKC in the membrane fraction of platelets and decreased the percentage of membrane associated PKC activity in total PKC activity. Moreover, DL-erythro-1,3-Dihydroxy-2-aminooctadecane, an elective protein kinase C inhibitor (PKCI), and RESV had additive effects of inhibiting the percentage of platelet aggregation and surface P-selectin-positive platelets. It is suggested that RESV may inhibit platelet aggregation, the percentage of surface P-selectin-positive platelets and subsequent thrombus formation. The mechanisms may be partly relative to the decrease of the activity of PKC of platelets.

[Suppressive effect in vitro of resveratrol on ADP induced human platelet aggregation and its active mechanism].

Resveratrol (RESV) is a polyphenolic compound existed in native plants such as grape, fleeceflower root, and peanut, etc. The aim of this study was to investigate the effects in vitro of RESV on adenosine diphosphate (ADP)-induced platelet aggregation, platelet membrane-bound fibrinogen (PFig) its mechanism of action. The effects of RESV and phospholipase Cbeta inhibitor (U73122) on ADP-induced healthy human volunteers platelet aggregation, PFig, and the expression of phospho-phospholipase Cbeta3 (P-PLCbeta3) and total-phospholipase Cbeta3 (T-PLCbeta3) were studied with platelet aggregometer, flow cytometry and Western blotting, respectively. Compared with control group, RESV at 25, 50 and 100 micromol x L(-1) inhibited ADP-induced platelet aggregation and PFig in a dose dependent manner, and RESV at 25 micromol x L(-1) obviously reduced expression of P-PLCbeta3 and ratio of P-PLCbeta3 to T-PLCbeta3 in platelet of healthy human volunteers. Furthermore, RESV and U73122 had additive effect in inhibiting platelet aggregation and PFig. All these suggested that RESV inhibited platelet aggregation and PFig induced by ADP partly through decreasing the activity of PLCbeta of platelets, and that RESV had definite effect of antiplatelet and might be developed as a novel antithrombotic agent.

[Inhibitory effects of emodin on proliferation of rat vascular smooth muscle cell induced by angiotensin II].

OBJECTIVE: To investigate the effects of emodin on the proliferation of cultured rat vascular smooth muscle cell (VSMC) induced by angiotensin II. METHOD: VSMCs were cultured by explant method. Cell proliferation model was established by stimulation with Ang II. Cell proliferation was measured by MTT assay to observe the effects of emodin (10, 20, 40 and 80 micromol x L(-1)) and N(G)-nitro-L-arginine methyl ester (L-NAME, 100 micromol x L(-1)) on VSMC proliferation induced by Ang II. The expression of PCNA was measured by immunohistochemical staining. Nitric oxide (NO) level was measured by Griess reagent. Nitric oxide synthase (NOS) and inducible nitric oxide synthase (iNOS) levels were detected by chemical colorimetric method. mRNA expression of iNOS was measured by reverse transcription polymerase chain reaction (RT-PCR). RESULT: Emodin at the doses range from 10 to 80 mol x L(-1) inhibited cell proliferation in a dose and time-dependent manner. The inhibitory effects were partly blocked by 100 mol x L(-1) of L-NAME. Emodin markedly decreased the expression of PCNA in VSMC, increased NO, NOS and iNOS levels, and increased iNOS mRNA expression in VSMC. CONCLUSION: Emodin could inhibite VSMCs proliferation induced by Ang II. Inhibiting the expression of PCNA, increasing the NO secretion and upregulating the iNOS gene expression might be associated with the inhibitory effects.

Enhanced Physical Stability of Mixed Ion Pair Amphiphile/Double-chained Cationic Surfactant Vesicles in the Presence of Cholesterol.

In this study, a pseudodouble-chained ion pair amphiphile (IPA), hexadecyltrimethylammoniumdodecylsulfate (HTMA-DS), and dialkyldimethylammonium bromide (DXDAB) with different chain lengths were used as the main materials to fabricate positively charged catanionic vesicles with various mole fractions of cholesterol. The effects of cholesterol and DXDAB alkyl chain length on physical stability of the catanionic vesicles were then investigated by size, zeta potential, and Fourier transform infrared analyses. With the presence of cholesterol in the mixed HTMA-DS/DXDAB vesicles or with increasing the DXDAB content in the presence of a proper amount of cholesterol, the physical stability of the catanionic vesicles could be enhanced. The spacing effect of cholesterol would reduce the counterion binding tendency at the charged vesicle surfaces, resulting in a more pronounced charge character of the catanionic vesicles. Furthermore, cholesterol-induced disordered structure contributed to the flexibility of the vesicular bilayers. Thus the physical stability of the vesicles was improved by adding cholesterol. With increasing the hydrocarbon chain length of DXDAB, cholesterol located toward the middle of the bilayers, enhancing the effects of cholesterol on charge and molecular packing characteristics of the vesicles. This led to a more pronounced stability enhancement effect on the vesicles with a longer alkyl chain length of DXDAB. The results suggested that the presence of cholesterol in the HTMA-DS/DXDAB catanionic vesicles could enhance vesicle stability through adjusting intra-vesicle and/or inter-vesicle interactions. In addition, the stability enhancement effect was more pronounced in the systems with a long DXDAB alkyl chain. The findings will be useful for developing new formulas of catanionic vesicles as drug delivery carriers.

Novel conductive polypyrrole/silk fibroin scaffold for neural tissue repair.

Three dimensional (3D) bioprinting, which involves depositing bioinks (mixed biomaterials) layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However, it remains challenging to prepare biomaterials with micro-nanostructures that accurately mimic the nanostructural features of natural tissues. A novel nanotechnological tool, electrospinning, permits the processing and modification of proper nanoscale biomaterials to enhance neural cell adhesion, migration, proliferation, differentiation, and subsequent nerve regeneration. The composite scaffold was prepared by combining 3D bioprinting with subsequent electrochemical deposition of polypyrrole and electrospinning of silk fibroin to form a composite polypyrrole/silk fibroin scaffold. Fourier transform infrared spectroscopy was used to analyze scaffold composition. The surface morphology of the scaffold was observed by light microscopy and scanning electron microscopy. A digital multimeter was used to measure the resistivity of prepared scaffolds. Light microscopy was applied to observe the surface morphology of scaffolds immersed in water or Dulbecco's Modified Eagle's Medium at 37°C for 30 days to assess stability. Results showed characteristic peaks of polypyrrole and silk fibroin in the synthesized conductive polypyrrole/silk fibroin scaffold, as well as the structure of the electrospun nanofiber layer on the surface. The electrical conductivity was 1 × 10-5-1 × 10-3 S/cm, while stability was 66.67%. A 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay was employed to measure scaffold cytotoxicity in vitro. Fluorescence microscopy was used to observe EdU-labeled Schwann cells to quantify cell proliferation. Immunohistochemistry was utilized to detect S100ß immunoreactivity, while scanning electron microscopy was applied to observe the morphology of adherent Schwann cells. Results demonstrated that the polypyrrole/silk fibroin scaffold was not cytotoxic and did not affect Schwann cell proliferation. Moreover, filopodia formed on the scaffold and Schwann cells were regularly arranged. Our findings verified that the composite polypyrrole/silk fibroin scaffold has good biocompatibility and may be a suitable material for neural tissue engineering.

Effects of Ethanol and Cholesterol on Thermotropic Phase Behavior of Ion-Pair Amphiphile Bilayers.

Ion-pair amphiphiles (IPAs, also known as catanionic surfactants) are lipid-like double-chained molecules potentially used for fabricating liposome-like vesicular drug and gene carriers. Frequently ethanol and cholesterol are added to modulate the properties of their bilayer membranes. Effects of ethanol and cholesterol on the fundamental properties of IPA bilayers such as thermotropic phase behavior, however, is not known. In this work, the bilayer phase transition behavior of two IPAs (decyltrimethylammonium-tetradecyl sulfate, DeTMA-TS, and dodecyltrimethylammonium-dodecyl sulfate, DTMA-DS) in tris buffer with various amounts of ethanol was studied by using differential scanning calorimetry (DSC). Effect of cholesterol (CHOL) addition on bilayer phase transition of IPAs with 20 vol% ethanol was thereafter systematically investigated. The experimental results showed that the main phase transition temperature (Tm) was monotonously decreased with the increase of ethanol concentration up to 30 vol%. The degree of Tm depression by ethanol is essentially the same for the two IPAs regardless of different symmetry in the hydrocarbon chains. Further addition of CHOL, however, caused a slight decrease in Tm on the one hand and a significant decrease in the enthalpy of phase transition on the other hand. When the added CHOL exceeded a specific amount, the phase transition disappeared. More hasty disappearance of phase transition was found for IPA with asymmetric structure than the symmetric one. Possible mechanisms of ethanol effect based on binding in the headgroup region of the bilayers and CHOL effect based on opposite (condensing and disordering) interactions with IPA molecules in bilayers, respectively, were proposed.

A partition-type tubular scaffold loaded with PDGF-releasing microspheres for spinal cord repair facilitates the directional migration and growth of cells.

The best tissue-engineered spinal cord grafts not only match the structural characteristics of the spinal cord but also allow the seed cells to grow and function in situ. Platelet-derived growth factor (PDGF) has been shown to promote the migration of bone marrow stromal cells; however, cytokines need to be released at a steady rate to maintain a stable concentration in vivo. Therefore, new methods are needed to maintain an optimal concentration of cytokines over an extended period of time to effectively promote seed cell localization, proliferation and differentiation. In the present study, a partition-type tubular scaffold matching the anatomical features of the thoracic 8-10 spinal cord of the rat was fabricated using chitosan and then subsequently loaded with chitosan-encapsulated PDGF-BB microspheres (PDGF-MSs). The PDGF-MS-containing scaffold was then examined in vitro for sustained-release capacity, biocompatibility, and its effect on neural progenitor cells differentiated in vitro from multilineage-differentiating stress-enduring cells (MUSE-NPCs). We found that pre-freezing for 2 hours at -20°C significantly increased the yield of partition-type tubular scaffolds, and 30 µL of 25% glutaraldehyde ensured optimal crosslinking of PDGF-MSs. The resulting PDGF-MSs cumulatively released 52% of the PDGF-BB at 4 weeks in vitro without burst release. The PDGF-MS-containing tubular scaffold showed suitable biocompatibility towards MUSE-NPCs and could promote the directional migration and growth of these cells. These findings indicate that the combination of a partition-type tubular scaffold, PDGF-MSs and MUSE-NPCs may be a promising model for the fabrication of tissue-engineered spinal cord grafts.

Effects of Sterol-Like Additives on Phase Transition Behavior of Ion-Pair Amphiphile Bilayers.

The incorporation of additive in lipid bilayers is one of the ordinary approaches for modulating their properties. Additive effect on phase transition of ion-pair amphiphile (IPA) bilayers, however, is not known. In this work, four double-chained IPAs with different hydrocarbon chain lengths and symmetry were designed and synthesized from single-chained cationic and anionic surfactants by the precipitation method. By using differential scanning calorimetry (DSC), the thermotropic transition behavior from gel phase (Lß) through rippled phase (Pß') if any to liquid-crystalline phase (Lα) was studied for bilayers of these lipid-like IPAs in excess water. The effects of three sterol-like additives (cholesterol, α-tocopherol, and α-tocopheryl acetate) in IPA bilayers on thermal phase behavior were then systematically investigated. The experimental results revealed that with increasing concentration of additive, the phase transition temperatures were unaffected on the one hand and the enthalpies of phase transition were decreased on the other hand. When the addition of additive exceeded a specific amount, the phase transition disappeared. More hasty disappearance of phase transition was found for IPAs with lower total number of carbon atoms in the hydrocarbon chains. For IPAs with the same total number of carbon atoms in the hydrocarbon chains, the disappearance of phase transition is more hasty for the asymmetric one than for the symmetric one. Similar effects on thermal phase behavior of four IPA bilayers were exhibited by the three additives with similar chemical structures. Possible mechanism of additive effects on phase transition of IPA bilayers was then proposed in line with that of lipid bilayers.