The
inherent shortcomings of polylactide (PLA) including brittleness,
low glass transition temperature, and melt strength during processing
were addressed through a facile melt blending of PLA with polybutadiene-g-poly(styrene-co-acrylonitrile) (PB-g-SAN) core–shell impact modifier and poly(methyl
methacrylate) (PMMA). Highly tough PLA-based ternary blends with drastically
enhanced glass transition temperature (≈ 21 °C) and melt
strength were successfully prepared. The effect of PMMA content (ranging
from 0 to 30 wt %) on the phase miscibility, morphology, mechanical
properties, thermal behavior, rheological properties, and toughening
mechanisms of PLA/PB-g-SAN/PMMA blends with 30% PB-g-SAN was systematically investigated. It was found that
PMMA can effectively tune the interfacial interactions, phase morphology
and performance of incompatible PLA/PB-g-SAN blend
owing to its partial miscibility with PLA matrix and miscibility with
SAN shell of PB-g-SAN, as evidenced by DMTA analysis.
Increase in PMMA content promoted the phase adhesion and dispersion
state of PB-g-SAN terpolymer in the blends and highly
toughened blends were achieved which showed incomplete break of impact
specimen. The significant effect of phase morphology on imparting
tremendous improvement in impact toughness was clarified. The maximum
impact strength (about 500 J/m), elongation-at-break and glass transition
were obtained for ternary blend with 25% PMMA. The PLA crystallinity
was gradually suppressed in ternary blends upon progressive increase
in PMMA content. Rheological studies showed solid-like behavior with
enhanced viscosities for ternary blends. Micromechanical deformations
and toughening mechanisms were studied by post-mortem fractography.
Massive matrix shear yielding was found as the main source of energy
dissipation triggered by suitable interfacial adhesion and microvoid
formation.
Polycaprolactone-tricalcium phosphate (PCL-TCP), a new composite scaffold, has been shown to facilitate early revascularization and speed up bone regeneration process. The objective of this study was to evaluate the effect of PCL-TCP seeded with mesenchymal stem cells (MSCs) on healing of the vertical bone critical sized defect in dog's mandible. Bone marrow aspirate from dog humerous was cultured and the stemness of the cells was examined by differentiation staining methods and flow cytometric analysis. Third passage subculture cells (5 × 10⁵ cells) were loaded on 20 × 10 × 10 mm³ and incubated for 48 h. The presence of MSCs in the pores was evaluated by scanning electron microscope. Bilateral mandibular premolar teeth were extracted in four dogs and the buccal and lingual bone plates were reduced to make a vertical defect. Cell-loaded scaffolds were fixed in right side and left side received pure PCL-TCP scaffolds as a control side defects. Histomorphometric analysis after 8 weeks of the scaffold implantation showed higher amount of lamellar bone in the test side (48.63%) than control side (17.27%) (p < 0.05).The results suggest that PCL-TCP may be an appropriate scaffold for loading MSCs in bone regeneration.
Transplantation of islet is a promising method in treatment of patients with type 1 diabetes mellitus (T1DM), however, is limited by islet shortage. The aim of this study was to prepare a polyethersulfone (PES) nanofibrous scaffolds to evaluate the pancreatic differentiation of human induced pluripotent stem cells (hiPSCs). The differentiation process in tissue culture dishes and PES scaffolds was evaluated at mRNA and protein level by RT-qPCR and immunofluorescence assay, respectively. The functionality of differentiated cells was determined by insulin and C-peptide release in response to glucose challenges. The results of this study showed that cells cultured on PES nanofibrous scaffolds exhibit more pancreatic b-cell characteristics as they express more pancreatic tissue-specific genes and proteins. Furthermore, the immunoassay showed that differentiated cells in both culture plates and PES scaffolds groups are functional and secrete C-peptide and insulin in response to glucose challenges. Altogether, the results of this study demonstrated that PES nanofibrous scaffold could provide the microenvironment that promotes the differentiation of induced pluripotent stem cells (iPSCs) into insulin producing cells.
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