The effect of surface functionalization on the interfacial adhesion between two immiscible semicrystalline polymers, polypropylene (PP) and a polyamide (nylon 6, Ny6)), was investigated. The surface of PP was functionalized by a low-energy ion-beam-assisted gas reaction. Surface functional groups containing carboxyl and carbonyl groups created remarkably different interactions at the interface. Fracture toughness was measured using an asymmetric double cantilever beam test (ADCB). The calculated fracture toughness was significantly increased for the functionalized PP case. The system with reactive oxygen gas added showed a higher fracture toughness than the case with only argon-ion-beam irradiation because of more reactions and/or interactions between the functionalized PP surface and Ny6. Analysis on the locus of failure by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) revealed that the fracture toughness between PP and Ny6 was influenced not only by the bonding temperature but also by the bonding time at constant bonding temperature. The fracture toughness increased after some induction time of annealing; then, it reached a plateau value. The fracture toughness increased with the bonding temperature, showed a maximum at 200 °C, and then decreased at a higher temperature of 210 °C. This behavior is different from other reported results. The present system is more or less like a chain tethered to a solid surface. The failure was caused by the weaker of the adhesive strength or the cohesive strength. The effect of bonding temperature is attributed to the cohesive failure in the PP phase. The adhesive strength increased with the bonding temperature while the cohesive strength decreased with the bonding temperature because of less entanglement of reacted chains with the other chains in the bulk. The dependence of the fracture toughness on the bonding time was explained in terms of this fracture mechanism.

A low energy Ar+ ion-beam was used to modify the surface of a high-density polyethylene (HDPE) dry powder. The modification reaction was promoted by the oxygen gas injected during the irradiation. This simple modification route is characterized as a heterogeneous, solvent-free, environmentally favorable process. The surface functional groups of the modified HDPE were confirmed with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy as being various oxygen-containing functional groups. The concentration of the functional groups varied rapidly with the irradiation time, reached a maximum value and then slowly decreased. Because of the low-energy characteristics of the ion beam, the changes in the molecular weight, the melting temperature, and the crystallinity of the modified HDPE were not significant, as evidenced by gel-permeation chromatography and differential scanning calorimetry. The rheological behavior of an HDPE/nylon 66 (Ny66) blend, which depends on the blend composition, was complicated due to immiscibility whereas the ion-beam-irradiated HDPE/Ny66 blend showed a more systematic behavior. Also, the compatibility effect of ion-beam-treated HDPE was investigated in the blend of HDPE/ Ny66. In the ion-beam-irradiated HDPE/blends, a significant decrease in the domain size of the dispersed phase was observed. Theoretical models were used to estimate the interfacial tension of HDPE/Ny66 blends. The calculated interfacial tension of an ion-beam-treated HDPE/Ny66 blend was less than that of a nontreated HDPE/Ny66 blend, indicating a greater interaction between the ion-beam-treated HDPE and the Ny66 phases. In addition, the mechanical properties of the ion-beam-treated HDPE/Ny66 blend showed a positive deviation from the rule of mixture. Finally, an explanation of the compatibilizing effect of ion-beam-treated HDPE is presented.

The effect of glass fibers on the crystallization of poly(butylene terephthalate) (PBT) was investigated by crystallization kinetics analysis under isothermal and nonisothermal conditions. From the crosspolar optical micrographs of melt‐ and solvent‐crystallized PBT composites, the glass fibers were found to increase the number density and decrease the size of crystallites. The glass fibers provided heterogeneous nucleation sites, and thus enhanced the overall rate of PBT crystallization in isothermal experiments. However, the Avrami exponent and the regime transitions were not significantly affected by the presence of glass fibers. For the nonisothermal kinetics of PBT composites, the model prediction was excellent in most ranges of crystallization, but it deviated above 70% of crystallization especially at fast cooling rates (>40°C/min). This discrepancy of the model seemed to result from the growth regime transitions, which were clearly observed especially at high undercoolings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 576–585, 2000

BackgroundSkin is an organ that plays an important role as a physical barrier and has many other complex functions. Skin mimetics may be useful for studying the pathophysiology of diseases in vitro and for repairing lesions in vivo. Cord blood mononuclear cells (CBMCs) have emerged as a potential cell source for regenerative medicine. Human induced pluripotent stem cells (iPSCs) derived from CBMCs have great potential for allogenic regenerative medicine. Further study is needed on skin differentiation using CBMC-iPSCs.MethodsHuman iPSCs were generated from CBMCs by Sendai virus. CBMC-iPSCs were differentiated to fibroblasts and keratinocytes using embryonic body formation. To generate CBMC-iPSC-derived 3D skin organoid, CBMC-iPSC-derived fibroblasts were added into the insert of a Transwell plate and CBMC-iPSC-derived keratinocytes were seeded onto the fibroblast layer. Transplantation of 3D skin organoid was performed by the tie-over dressing method.ResultsEpidermal and dermal layers were developed using keratinocytes and fibroblasts differentiated from cord blood-derived human iPSCs, respectively. A complex 3D skin organoid was generated by overlaying the epidermal layer onto the dermal layer. A humanized skin model was generated by transplanting this human skin organoid into SCID mice and effectively healed skin lesions.ConclusionsThis study reveals that a human skin organoid generated using CBMC iPSCs is a novel tool for in-vitro and in-vivo dermatologic research.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-0958-2) contains supplementary material, which is available to authorized users.

Using the biaxially oriented film process, polypropylene (PP)/ ethylene-vinyl alcohol copolymer (EVOH) blends with an improved barrier property could be obtained by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology, induced by biaxial orientation, was found to result in a significant increase in the oxygen barrier property of PP/EVOH (85/15) blends by about 10 times relative to the pure PP. In this study, compatibility in the PP/EVOH blend system was evaluated by investigating the influence of compatibilizer on the rheological, morphological, and mechanical properties of the blends. In addition, the effects of compatibilizer content, draw ratio, and draw temperature on the oxygen permeability and morphology of biaxially drawn blend films were also studied. It was revealed that an optimum amount of compatibilizer, maleic anhydride grafted PP, should be used to improve the barrier property of the PP/EVOH blends with a well-developed laminar structure. The draw ratio and draw temperature had a significant influence on the permeability of the blends. The 192VOL. 20, NO. 3 PROPERTIES OF PP/EVOH BLENDS blend films exhibited a more pronounced laminar structure when the blends were stretched biaxially under processing conditions of higher draw ratio and draw temperature, resulting in higher barrier properties.

Human bone marrow-derived mesenchymal stem cells (MSCs) have been observed to inhibit arthritis in experimental animal models such as collagen-induced arthritis. However, the exact anti-inflammatory mechanisms remain poorly understood. Interleukin-1 receptor antagonist (IL-1Ra) is an anti-inflammatory cytokine produced by immune and stromal cells. We postulated that MSCs could produce IL-1Ra and attenuate experimental arthritis. In this study, 5x106 MSCs were injected into the peritoneal cavity of IL-1Ra knockout (IL-1RaKO) mice. MSCs reduced the severity of the arthritis by histology and decreased pro-inflammatory cytokine levels in IL-1RaKO mice. The ratio of splenic T helper 17 (Th17) cells to regulatory T cells (Treg) was significantly decreased in MSC-injected IL-1RaKO mice. Purified splenic CD4+ T cells from mice in each of the treatment groups were cultured under Th17 polarizing conditions and analyzed by flow cytometry. Less expansion of the Th17 population was observed in the MSC-treated group. Interestingly, MSCs expressed inducible IL-1Ra against inflammatory environmental stimuli. Human recombinant IL-1Ra could suppress Th17 cells differentiation under Th17 polarizing conditions. These results indicate that IL-1Ra expressed by MSCs can inhibit Th17 polarization and decrease the immune response in IL-1RaKO mice. Therefore, MSC-derived IL-1Ra may inhibit inflammation in IL-1RaKO mice via effects on Th17 differentiation.

Rheumatoid arthritis (RA) is a chronic autoimmune disease that typically results in strong inflammation and bone destruction in the joints. It is generally known that the pathogenesis of RA is linked to cardiovascular and periodontal diseases. Though rheumatoid arthritis and periodontitis share many pathologic features such as a perpetual inflammation and bone destruction, the precise mechanism underlying a link between these two diseases has not been fully elucidated. Collagen-induced arthritis (CIA) mice were orally infected with Porphyromonas gingivalis (Pg) or Pg preincubated with an anti-FimA antibody (FimA Ab) specific for fimbriae that are flexible appendages on the cell surface. Pg-infected CIA mice showed oral microbiota disruption and increased alveolar bone loss and had synovitis and joint bone destruction. However, preincubation with FimA Ab led to a significant reduction in the severity of both oral disease and arthritis. Moreover, FimA Ab attenuated bacterial attachment and aggregation on human gingival and rheumatoid arthritis synovial fibroblasts. In addition, we discovered bacteria may utilize dendritic cells, macrophages and neutrophils to migrate into the joints of CIA mice. These results suggest that disrupting Pg fimbriae function by FimA Ab ameliorates RA.

In comparison to other kinds of crosslinked thermoset foam, recyclable polyolefin foam is an environmentally friendly material, but it increases the degree of foaming in the foam extrusion process. In order to overcome this shortcoming, the effect of material and process variables on the degree of foaming and the growth behavior of the gas bubbles was studied by using polyolefins, such as polypropylene (PP), low density polyethylene (LDPE), and high density polyethylene (HDPE). These materials were foamed in extrusion process with a blowing agent consisting of sodium bicarbonate and citric acid. A higher degree of foaming was obtained with a low temperature of cooling water and high melt temperature. The take‐up speed did not influence the degree of foaming. It was also observed from cell morphologies that the size of the gas bubbles was reduced with increased take‐up speed and decreased melt temperature, but the size of the gas bubbles was nearly invariant as the temperature of the cooling water increased. In addition, the effects of the molecular weight, the molecular structure, the melt viscosity, and the melt tension on the degree of foaming and the growth of the gas bubbles were investigated. It was revealed that the degree of foaming and the size of the gas bubbles were directly related to the melt tension of the polymer melt, regardless of the structure and the molecular weight of the polymer resin and the temperature of the polymer melt. This implies that the ability to sustain the cell in the melt state is a critical foaming parameter in the extrusion process. © 2000 John Wiley & Sons, Inc. Adv Polym Techn 19: 97–112, 2000