Tai-Horng Young

Properties of the poly(vinyl alcohol)/chitosan blend and its effect on the culture of fibroblast in vitro

In this work, the properties of poly(vinyl alcohol) (PVA) and PVA/chitosan blended membranes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and electron spectroscopy for chemical analysis (ESCA). The SEM photographs show the PVA/chitosan blended membrane undergoes dramatic changes on the surface and bulk structure during the membrane formation. The DSC analysis shows that PVA and chitosan are not very compatible in the PVA/chitosan blended membrane, whereas the combination of two polymer chains of constitutionally different features is revealed. In addition, the surface of the PVA/chitosan blended membrane is enriched with nitrogen atoms at the ESCA analysis. These reflect the PVA membrane can be modified by blending with chitosan that in turn may affect the biocompatibility of the blended membrane. Therefore, adhesion and growth of fibroblasts on the PVA as well as PVA/chitosan blended membranes were investigated. Cell morphologies on the membranes were examined by SEM and cell viability was studied using MTT assay. It was observed that the PVA/chitosan blended membrane was more favorable for the cell culture than the pure PVA membrane. Cells cultured on the PVA/chitosan blended membrane had good spreading, cytoplasm webbing and flattening and were more compacting than on the pure PVA membrane. Consequently, the PVA/chitosan blended membrane may spatially mediate cellular response that can promote cell attachment and growth, indicating the PVA/chitosan blended membrane should be useful as a biomaterial for cell culture.

Pore formation mechanism of membranes from phase inversion process

Abstract The formation of pores in membranes obtained by phase inversion on the basis of thermodynamics and diffusional aspects of phase separation processes. We demonstrated that different types of phase separation are responsible for the formation of the porous structure in ethylene-vinyl alcohol (EVAL) membranes. Special attention is paid here to the formation mechanism of the finger-like cavities. The results are consistent with observations of pore formation occurring on wet-casting membrane formation process and provide a greater understanding of the formation mechanism of pores of casting membranes.

Targeting efficiency and biodistribution of biotinylated-EGF-conjugated gelatin nanoparticles administered via aerosol delivery in nude mice with lung cancer

Lung cancer is the most malignant cancer today; in order to develop an effective drug delivery system for lung cancer therapy, gelatin nanoparticles (GPs) were modified with NeutrAvidin(FITC)-biotinylated epidermal growth factor (EGF) to form EGF receptor (EGFR)-seeking nanoparticles (GP-Av-bEGF). Aerosol droplets of the GP-Av-bEGF were generated by using a nebulizer and were delivered to mice model of lung cancer via aerosol delivery. Analysis of the aerosol size revealed that 99% of the nanoparticles after nebulization had a mass median aerodynamic diameter (MMAD) within the suitable range (0.5-5 microm) for lower airway deposition. The safety of inhaled nanoparticles was examined by lung edema and myeloperoxidase (MPO) activity assay. Theres no finding suggestive of acute lung inflammation following inhalation. The fluorescence images obtained from live mice showed that the GP-Av-bEGF could target the cancerous lungs in a more specific manner. Fluorescence analysis of the organs revealed that the GP-Av-bEGF was mainly distributed in cancerous lungs. In contrast, nanoparticle accumulation was lower in normal lungs. The histological results indicated that the fluorescent GP-Av-bEGF was colocalized with the anti-EGFR-immunostain due to EGFR binding. The results of this study revealed that GP-Av-bEGF could target to the EGFR-overexpression cancer cells in vivo and may prove to be beneficial drug carriers when administered by simple aerosol delivery for the treatment of lung cancer.

Evaluating cutaneous photoaging by use of multiphoton fluorescence and second-harmonic generation microscopy

The photoaging process of facial skin is investigated by use of multiphoton fluorescence and second-harmonic generation (SHG) microscopy. We obtain the autofluorescence (AF) and SHG images of the superficial dermis from the facial skin of three patients aged 20, 40, and 70 years. The results show that areas of AF increase with age, whereas areas of SHG decrease with age. The results are consistent with the histological findings in which collagen is progressively replaced by elastic fibers. The AF and SHG changes in photoaging are quantified by a SHG to autofluorescence aging index of dermis (SAAID). Our results suggest that SAAID can be a good indicator of the severity of photoaging.

The influence of spheroid formation of human adipose-derived stem cells on chitosan films on stemness and differentiation capabilities.

Adipose-derived stem cells (ASCs) have valuable applications in regenerative medicine, but maintaining the stemness of ASCs during in vitro culture is still a challenging issue. In this study, human ASCs spontaneously formed three-dimensional spheroids on chitosan films. Most ASCs within the spheroid were viable, and the cells produced more extracellular molecules, like laminin and fibronectin. Comparing to monolayer culture, ASC spheroids also exhibited enhanced cell survival in serum deprivation condition. Although cell proliferation was inhibited in spheroids, ASCs readily migrated out and proliferated upon transferring spheroids to another adherent growth surface. Moreover, spheroid-derived ASCs exhibited higher expansion efficiency and colony-forming activity. Importantly, we demonstrated that spheroid formation of human ASCs on chitosan films induced significant upregulation of pluripotency marker genes (Sox-2, Oct-4 and Nanog). By culturing the ASC spheroids in proper induction media, we found that ASC differentiation capabilities were significantly enhanced after spheroid formation, including increased transdifferentiation efficiency into neuron and hepatocyte-like cells. In a nude mice model, we further showed a significantly higher cellular retention ratio of ASC spheroids after intramuscular injection of spheroids and dissociated ASCs. These results suggested that ASCs cultured as spheroids on chitosan films can increase their therapeutic potentials.

Mechanisms of PVDF membrane formation by immersion-precipitation in soft (1-octanol) and harsh (water) nonsolvents

Abstract Crystalline PVDF was precipitated, respectively, from water/DMF and 1-octanol/DMF solutions to produce membranes with asymmetric and uniform morphologies. The formation mechanisms of these specific structures were described both in the aspects of thermodynamics (equilibrium phase behavior) and the kinetics (diffusion trajectory). The phase diagrams of the investigated systems indicated the possibility of liquid–liquid demixing or crystallization or both during the immersion-precipitation process. The sequence of these phase separation events, which determined the ultimate membrane structure, was attributed to the kinetic factors. Into this context, a quantitative model describing the immersion-precipitation process was considered. The calculated diffusion trajectory and concentration distribution in the nascent membrane were found to be consistent with the experimental membrane morphologies. Moreover, the precipitation rate of the PVDF solution in water and 1-octanol were examined by the light transmission experiments. The latter results further confirmed the validity of the mass transfer calculations.

The effect of polymeric additives on the structure and permeability of poly(vinyl alcohol) asymmetric membranes

Abstract The manufacture and dextran-rejection properties of asymmetric poly(vinyl alcohol) (PVA) membranes have been described in this study. Membranes were prepared from a casting solution of PVA, water as solvent, and water-soluble polymeric additive by immersing them in Na 2 SO 4 /KOH/H 2 O as coagulant medium. Experiments showed that the dextran and poly(vinyl pyrrolidone) (PVP) additives exerted a different influence on the structure and permeability of membranes. Especially, the structure of skin layer strongly depended on the polymeric additives in the casting solution. The addition of dextran additives in the system could induce pores in the top layer. Conversely, the PVP additives effectively blocked the interstitial cavities within the top layer to generate a more compact structure. A mechanism describing that the affinity between additive and casting solution as well as between additive and coagulant medium was proposed to investigate the effect of dextran and PVP additives in the formation of PVA membranes. The results presented here offer a better understanding of relationships between the membrane formation mechanism and the skin structure when designing an asymmetric membrane by the addition of polymeric additives in the casting solution.

Effects of Cyclic Mechanical Stretching on the mRNA Expression of Tendon/Ligament-Related and Osteoblast-Specific Genes in Human Mesenchymal Stem Cells

The purpose of this study was to explore the influences of cyclic mechanical stretching on the mRNA expressions of tendon/ligament-related and osteoblast-specific marker genes in human MSCs seeded onto a collagen type I-coated surface. The stretch-induced mRNA expressions of mesenchymal stem cell protein (MSCP), matrix metalloproteinase-3 (MMP-3), and marker genes related to tendon/ligament cells (type I collagen, type III collagen, and tenascin-C) and those typical of osteoblasts (core binding factor alpha 1 (Cbfa1), alkaline phosphatase (ALP), and osteocalcin (OCN)) were analyzed by quantitative real-time PCR. The results revealed significant downregulation of MSCP and upregulation of MMP-3 genes in MSCs subjected to mechanical loading, regardless of the magnitude of the stretching (high or low). Moreover, the typical marker genes of the osteoblast lineage were upregulated by low-magnitude stretching, whereas tendon/ligament-related genes were upregulated by high-magnitude stretching for a long period. Cbfa1 and ALP were upregulated starting as early at 8 hr, followed by a downward trend and no significant change in expression at the other time points. The mRNA expressions of type I collagen, type III collagen, and tenascin-C significantly increased in MSCs subjected to 10% stretching for 48 hr, and this effect still existed after the stretched cells had rested for 48 hr. This study demonstrated the effect of cyclic mechanical stretching on differential transcription of marker genes related to different cell lineages. Low-magnitude stretching increased mRNA expressions of Cbfa1 and ALP and was possibly involved in the early osteoblastic differentiation of MSCs, whereas high-magnitude stretching upregulated the mRNA expressions of tendon/ligament-related genes.

Interactive effects of mechanical stretching and extracellular matrix proteins on initiating osteogenic differentiation of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are characterized by their abilities to differentiate into different lineages, including osteoblasts. Besides soluble factors, mechanical strain and extracellular matrix (ECM) proteins play important roles in osteogenic differentiation of hMSCs. However, interactions between them are still not fully understood. The purpose of this study was to investigate the combined effects of insoluble chemical and mechanical factors (ECM proteins vs. cyclic stretching) in driving hMSCs into osteogenic differentiation. To avoid the influence from osteogenic supplements, hMSCs were cultured in regular medium and subjected to cyclic mechanical stretching using a Flexcell Tension system (3% elongation at 0.1 Hz) when they were grown on substrates coated with various ECM proteins (collagen I (Col I), vitronectin (VN), fibronectin (FN), and laminin (LN)). Using alkaline phosphatase (ALP) activity and mineralized matrix deposition as respective indicators of the early and late stages of osteogenesis, we report herein that all of the ECM proteins tested supported hMSC differentiation into osteogenic phenotypes in the absence of osteogenic supplements. Moreover, cyclic mechanical stretching activated the phosphorylation of focal adhesion kinase (FAK), upregulated the transcription and phosphorylation of core‐binding factor alpha‐1 (Cbfa1), and subsequently increased ALP activity and mineralized matrix deposition. Among the ECM proteins tested, FN and LN exhibited greater effects of supporting stretching‐induced osteogenic differentiation than did Col I and VN. The ability of ECM proteins and mechanical stretching to regulate osteogenesis in hMSCs can be exploited in bone tissue engineering via approximate matrix design or application of mechanical stimulation. J. Cell. Biochem. 108: 1263–1273, 2009.

Formation of particulate microporous poly(vinylidene fluoride) membranes by isothermal immersion precipitation from the 1-octanol/ dimethylformamide/poly(vinylidene fluoride) system

Abstract Phase diagrams were determined for poly(vinylidene fluoride) (PVDF) and a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene (VDF/HFP/TFE) in solutions composed of 1-octanol and dimethylformamide at 25°C. From the measured gelation and liquid–liquid phase separation data, binary interaction parameters were computed using a modified Flory–Huggins theory. PVDF microporous membranes were then prepared by isothermal immersion precipitation processes in various doping conditions. The formed membrane exhibited a particulate morphology characterized by a uniform package of spherical particles of identical size. These particles were identified to be full spherulites of PVDF using scanning electron microscopy, differential scanning calorimetry and small angle light scattering techniques.