Biomedical subjects

Tai-Horng Young

Publications and source records attributed to Tai-Horng Young.

At least 19 recordsLinked to original sources

PubMed2006

Role of phase diagram of membrane formation system in controlling the crystallinity and degradation rate of PLLA membranes.

In this work, the theoretical phase diagram of membrane formation system of ethanol, methylene chloride, and poly-L-lactide (PLLA) was studied. On the basis of the phase diagram, particulate and porous membranes, dominated by crystallization and liquid-liquid demixing, respectively, were prepared. Furthermore, degradation of PLLA membranes with particulate, porous, and dense morphologies was performed in phosphate buffered solution (PBS) at 37 degrees C for 168 days and was investigated by mass loss, scanning electron microscopy (SEM), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Besides the membrane morphology, a close relationship between the phase behavior of the membrane formation system and the membrane crystallinity was found, which in turn influenced the degradation rate of these membranes significantly. In the case of dense membranes, it showed the lowest initial crystallinity and the greatest rate of mass loss and molecular weight decrease compared with particulate and porous membranes. In contrast, the particulate membranes had the highest crystallinity and the slowest degradation rate in this study. Therefore, the phase diagram of membrane formation system could not only anticipate membrane morphology, but could also control the membrane crystallinity and degradation rate simultaneously.

Biocompatible Materials↗

PubMed2006

Assessment of GaN chips for culturing cerebellar granule neurons.

In this work, the behaviors of cerebellar granule neurons prepared from 7-day-old Wistar rats on gallium nitride (GaN) were investigated. We believe that this is the first time that the GaN has been used as a substrate for neuron cultures to examine its effect on cell response in vitro. The GaN surface structure and its relationship with cells were examined by atomic force microscopy (AFM), metallography microscopy, scanning electron microscopy (SEM), lactate dehydrogenase (LDH) release and Western blot analysis. GaN is a so-called III-V compound semiconductor material with a wide bandgap and a relatively high bandgap voltage. Compared with silicon used for most neural chips, neurons seeded on GaN were able to form an extensive neuritic network and expressed very high levels of GAP-43 coincident with the neurite outgrowth. Therefore, the GaN structure may spatially mediate cellular response that can promote neuronal cell attachment, differentiation and neuritic growth. The favorable biocompatibility characteristics of GaN can be used to measure electric signals from networks of neuronal cells in culture to make it a possible candidate for use in a microelectrode array.

Animals↗

PubMed2006

Proliferation and differentiation of neural stem cells on lysine-alanine sequential polymer substrates.

The purpose of this study was to explore the phenotypic potential of embryonic rat cerebral cortical stem cells by inducing differentiation on lysine-alanine sequential (LAS) polymer substrates at neurosphere level. LAS polymer is a heterologous polymer of lysine and alanine and has been demonstrated to enhance axon growth of neurons in a serum-free medium in vitro. It was found that very few cells migrated outside of the neurospheres but extremely long processes extended from differentiated cells could form a network between remote neurospheres when cells were cultured on LAS substrates at a low density of 120 neurospheres/cm(2) in the serum-free medium. On the contrary, when the neurosphere density was increased to 360 neurospheres/cm(2), many neurosphere-forming cells migrated out from their original aggregate and exhibited short processes morphology. Furthermore, when serum was added to the culture system, the neurosphere-forming cells could be induced into an extensive cellular substratum of protoplasmic cells upon which process-bearing cells spread. Clearly, neurospheres could exhibit different behaviors on LAS substrates according to the complex environmental conditions. Here, we proposed that neurospheres would change their social communication and adopt different strategies to communicate with other neurospheres when they detected each other's presence. Therefore, the mediation of cell behavior on LAS substrates by communication between neurospheres should be taken into account.

Animals↗

PubMed2006

Elucidating in vitro cell-cell interaction using a microfluidic coculture system.

This work presents a novel microfluidic coculture system that improves the accuracy of evaluating the interaction between cocultured cell types. A microfluidic coculture chip, fabricated by CO(2) laser direct-writing on polymethyl methacrylate (PMMA), was designed to separate two cell types using a microchannel, while permitting transfer of cellular media. The system has two up-stream wells and five down-stream wells. As an example, released inflammatory cytokines (e.g., interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha)), activated in up-stream macrophages, flow through a microfluidic mixing system, generating linear concentration gradients in down-stream wells and inducing down-stream osteoblasts to release prostaglandin E2 (PGE2), a well-known bone resorption marker. Osteoblast viability was assessed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. This novel coculture system can be applied to evaluate cell-cell interaction while physically separating interacting cells.

Cell Communication↗

PubMed2005

Enhanced cell survival of melanocyte spheroids in serum starvation condition.

Autologous melanocyte transplantation for vitiligo treatment by use of melanocyte suspension has drawbacks including cell damage in cell preparation and transportation, difficult manipulation and low engraftment rate in acral vitiligious lesions. We have proposed the concept of cellular patch as an alternative solution. In the development of melanocyte patches, we have shown that chitosan membrane supports the growth and phenotype expression of melanocytes. Surprisingly, melanocytes spontaneously grow into three-dimensional spheroids on chitosan-coated surface. In this work, we demonstrate that, compared with monolayered melanocytes, melanocyte spheroids show a better survival in growth factor and serum-deprived condition. Survival of melanocytes is further ameliorated when a greater portion of melanocytes is precultured into spheroidal morphology. Melanocyte spheroids disintegrate and the cells return to a physiological dendritic morphology after they are reinoculated on collagen I-coated surface. Our results show that melanocytes are morphologically transformable depending on the substratum used and spheroidal melanocytes have a superior survival to that of monolayered dendritic melanocytes in stringent conditions. Preculturing melanocytes into spheroids can provide melanocytes a survival advantage. Chitosan-based melanocyte patch can be a promising method to enhance the engraftment rate and facilitate the cell preparation and transplantation procedures in melanocyte transplantation for vitiligo treatment.

Biocompatible Materials↗

PubMed2005

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.

Adult↗

PubMed2005

Interactions of acinar cells on biomaterials with various surface properties.

The purpose of this study is to evaluate the interactions of rat parotid acinar cells on biomaterials with different surface properties. The biomaterials used in this study included polyvinyl alcohol (PVA), chitosan, poly (ethylene-co-vinyl alcohol) (EVAL), and polyvinylidene fluoride (PVDF). Cell morphology was observed by photomicroscope. Cell growth and differentiated characteristic function were separately assayed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction activity and amylase activity. Results indicated that behaviors of acinar cells on materials might differ to a great extent depending on the surface hydrophilicity and morphology of the materials. On the relatively hydrophobic materials, the abilities of acinar cells to adhere and proliferate increased simultaneously. In addition, porous PVDF had higher cell growth compared with dense PVDF. Therefore, the hydrophobic PVDF with a porous structure was the best substrate for culturing acinar cells. According to our findings, a tubular PVDF scaffold with dense outer surface to prevent saliva leakage and with porous inner surface for the cell growth was proposed to serve as an artificial salivary gland for future use in the treatment of patients with salivary hypofunction.

Amylases↗

PubMed2005

Determination of surface charge properties of PC-12 cells by electrophoresis.

The electrophoretic behavior of pheochromocytoma (PC-12) cells was investigated both experimentally and theoretically. Cell mobility in aqueous media at different pHs and ionic concentrations was measured, and a model, which assumed that the cell surface contains both acidic and basic functional groups, was proposed. As a result, it was revealed that the experimental data gathered can be described satisfactorily by assuming that the cell surface contains two types of monovalent acidic functional groups and one basic functional group. The values of the dissociation constants of the acidic and basic groups are found to be close to those of acidic amino acids, which indicates that the acidic amino acids may play an important role in the surface electrical properties of PC-12 cells.

Animals↗

PubMed2005

Using a microfluidic device for 1 microl DNA microarray hybridization in 500 s.

This work describes a novel and simple modification of the current microarray format. It reduces the sample/reagent volume to 1 microl and the hybridization time to 500 s. Both 20mer and 80mer oligonucleotide probes and singly labeled 20mer and 80mer targets, representative of the T-cell acute lymphocytic leukemia 1 (TAL1) gene, have been used to elucidate the performance of this hybridization approach. In this format, called shuttle hybridization, a conventional flat glass DNA microarray is integrated with a PMMA microfluidic chip to reduce the sample and reagent consumption to 1/100 of that associated with the conventional format. A serpentine microtrench is designed and fabricated on a PMMA chip using a widely available CO2 laser scriber. The trench spacing is compatible with the inter-spot distance in standard microarrays. The microtrench chip and microarray chip are easily aligned and assembled manually so that the microarray is integrated with a microfluidic channel. Discrete sample plugs are employed in the microchannel for hybridization. Flowing through the microchannel with alternating depths and widths scrambles continuous sample plug into discrete short plugs. These plugs are shuttled back and forth along the channel, sweeping over microarray probes while re-circulation mixing occurs inside the plugs. Integrating the microarrays into the microfluidic channel reduces the DNA-DNA hybridization time from 18 h to 500 s. Additionally, the enhancement of DNA hybridization reaction by the microfluidic device is investigated by determining the coefficient of variation (CV), the growth rate of the hybridization signal and the ability to discriminate single-base mismatch. Detection limit of 19 amol was obtained for shuttle hybridization. A 1 mul target was used to hybridize with an array that can hold 5000 probes.

Basic Helix-Loop-Helix Proteins↗

PubMed2005

Polyethylene failure of the patellar component in New Jersey low-contact stress total knee arthroplasties.

In a postoperative 5- to 12-year follow-up study of 598 New Jersey low-contact stress total knee arthroplasties, 32 required revision. All retrieved patellar components were examined for polyethylene damage. These 32 cases had 3 types of failure: split rupture (7 cases), peripheral wear (21), and cantilevering breakage (4), respectively 75%, 64.3%, and 100% of which showed subluxation and/or tilting of the patellar component on the prerevision roentgenograms. Misalignment at the joint contact surfaces and rotational blockage of the mobile patellar component were considered the major causes of the failure. A design of a flatter metallic button (giving larger focal thickness of the polyethylene) and a dome-shaped polyethylene (reducing stress concentration at the pinnacle) may alleviate the failure driving mechanism should subluxation or tilting of the patellar component take place.

Arthroplasty, Replacement, Knee↗

PubMed2005

Formation of melanocyte spheroids on the chitosan-coated surface.

The search for biocompatible materials that can maintain function of melanocytes as the cellular patch is a feasible alternative for use in the autologous melanocyte transplantation for vitiligo. In this study, we demonstrated that the surface of chitosan-coated polystyrene wells supported the growth and phenotype expression of melanocytes. Depending on the seeding density and culture time, melanocytes were monolayered or spheroidal in morphology. At seeding densities above 10 x 10(3) cells/cm2, human melanocytes started to aggregate on the surface of chitosan after 2 days in culture. These aggregates grew into compact melanocyte spheroids on day 3 and more melanocyte spheroids were observed when a higher seeding density was used. Cells remained viable in the spheroids and grew into dendritic melanocytes when they were reinoculated on polystyrene wells. Conversely, the time for the formation of melanocyte spheroids needed a longer period at lower seeding density. For example, melanocytes at as low as 1.25 x 10(3) cells/cm2 did not aggregate until the 20th day of culture. In order to interpret the phenomenon further, we proposed the formation of melanocyte spheroids on the chitosan is mediated by a balance between two competing forces: the interactions of cell-chitosan and cell-cell.

Cell Adhesion↗

PubMed2005

Behavior of embryonic rat cerebral cortical stem cells on the PVA and EVAL substrates.

Cell behavior is determined by intrinsic programs and complex interactions among cells, medium components and substrates. Several previous reports have demonstrated the usefulness of extrinsic signals coming from soluble growth factors and cell-cell contact for regulating the proliferation and differentiation of neural stem cells. At present, the effects of substrate on neural stem cells are not known. In this study, the behavior of neural stem cells, isolated from embryonic rat cerebral cortex, was observed and compared on the polyvinyl alcohol (PVA) and poly (ethylene-co-vinyl alcohol) (EVAL) substrates in the presence of the mitogenic effect of basic fibroblast growth factor (bFGF) in the serum-free medium. It was found that PVA and EVAL exerted different influences on the fate of neural stem cells. The behavior of neural stem cells on the EVAL was independent of cell density at the single-cell level. Single neural stem cells seemed to remain dormant on the EVAL. Conversely, the development of cell clusters, termed neurospheres, was in a density-dependent manner on the EVAL. Neurospheres continuously proliferated under high-density culture condition, but differentiated into neurons and astrocytes under low-density culture condition. However, regardless of single cells or neurospheres, cultured cells could not survive on the PVA. Therefore, it is reasonable to assume that biomaterials may stimulate or inhibit the proliferation and differentiation of neural stem cells. These in vitro results are very encouraging since this information should be useful for the development of strategies for regulating the preservation, proliferation and differentiation of neural stem cells.

Animals↗

PubMed2004

Preparation of PLLA membranes with different morphologies for culture of MG-63 Cells.

In this work, poly L-lactide (PLLA) membranes with different morphologies were prepared and the equilibrium phase diagram of membrane formation system of ethanol, methylene chloride, and PLLA was studied. Based on the phase diagram, particulate and porous membranes, dominated by crystallization and liquid-liquid demixing, respectively, could be prepared by changing the PLLA concentration of casting solution. In addition, in vitro interaction of MG-63 osteosarcoma cells and PLLA membranes with dense, porous and particulate morphologies was investigated. It was found that the particulate membrane not only could improve cell adhesion and growth, but also could upregulate the osteoblastic phenotype. Therefore, the PLLA membrane with particulate morphology satisfies the biomaterial requirement necessary for temporary scaffold to transplanted osteoblasts and provides a means for the architectural design of more complex tissue-engineered systems.

Adolescent↗

PubMed2003

Change in electrophoretic mobility of PC12 cells after culturing on PVA membranes modified with different diamines.

The cell-biomaterial interaction is of extreme importance in regulating the numerous functions necessary for cell adhesion, growth, and differentiation. In the current study, electrophoresis was used to investigate the interactions between cells and biomaterials by measuring the change in electrophoretic mobility of pheochromocytoma (PC12) cells after they were cultured on the poly (vinyl alcohol) membranes modified with different diamines. Variations in cellular activity and electrophoretic mobility of cultured cells were compared. It was found that the intracellular metabolism and the cell surface charge properties were altered after cells contacting biomaterials and the variation of the latter occurred earlier than that of the former. Although the precise mechanism by which the variation of electrophoretic mobility of cultured PC12 cells was unknown, the biomaterials could influence the cell mobility within a short incubation time. It was hypothesized that changes in extracellular matrix components of cell surface may be in part responsible.

Animals↗

PubMed2003

Behavior of MG-63 cells on nylon/chitosan-blended membranes.

In this work, the properties of nylon, chitosan, and their blended membranes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction analysis. The SEM photographs show that the undulating surface of the nylon membrane became less obvious by blending with chitosan. The DSC and X-ray diffraction analysis show that constitutionally different features in the combination of two polymer chains were revealed, suggesting that nylon and chitosan are immiscible at the microscopic level in the blended membranes. Furthermore, an attempt was made to understand whether the two components contribute independently to the adhesion, growth, and activation of MG-63 osteoblastlike cells. The cell adhesion increased with increasing chitosan content, indicating that the affinity between the cells and the membranes increased with increasing chitosan content. Although the blended membranes with higher nylon content exerted an inhibitory effect on cell adhesion, cells cultured on the nylon membrane proliferated at higher rates and the nylon membrane was the least stimulating of MG-63 cell cytokine production over a 4-day period when compared with all the other membranes. Combined with the result of cell growth and cell activation, the chitosan content in the blended membrane did not proportionally influence the behavior of MG-63 cells. It is proposed that cell's size was larger than the scale of nylon or chitosan domain in the blended membranes because of the incomplete miscibility between them. Therefore, even if the composition of the blended membranes is systematically changed, every cell covers a multiphase surface that is considered a totally new material for cells. Consequently, cell growth and cell activation on a blended membrane are not simply proportional to their composition. In contrast, cell adhesion is a simpler process, like a physical adsorption process, which is related to the bulk property of a blended membrane.

Biocompatible Materials↗

PubMed2003

Electrophoresis of biological cells: charge-regulation and multivalent counterions association model.

The electrophoresis of a biological cell is analyzed theoretically. An entity, which is of amphoteric nature, is used to simulate its electrophoretic behavior. To reflect conditions of practical interest, we assume that the liquid phase contains mixed (a:b)+(c:b) electrolytes, where a and c are the valences of cations, and b is the valence of anions. We consider the case where the surface of a cell contains both bivalent acidic and monovalent basic functional groups, the dissociation/association of them yields fixed surface charge, and the multivalent cations in the liquid phase are allowed to combine with dissociated acidic functional groups, which has the effect of lowering the charge density on cell surface. The electrophoretic behaviors of a cell under various conditions are illustrated. The results obtained can be used to identify the types of functional groups that may be present on cell surface. On the other hand, if the surface functional groups involved in cell electrophoresis are known, then their density and the associated dissociation/association constants can be estimated from experimental data.

Cations↗

PubMed2003

Covalent bonding of lysine to EVAL membrane surface to improve survival of cultured cerebellar granule neurons.

Polylysine is a commonly used coating material in the preparation of neuronal cultures. In the present study, poly (ethylene-co-vinyl alcohol) (EVAL) membranes were modified by the covalent bonding of lysine via isocyanation of surface hydroxyl groups to improve cell behavior in cultured cerebellar granule neurons from 7-day-old Wistar rats. Cell survival and death ratio were assayed by MTT reduction activity and lactate dehydrogenase release, respectively. Cell morphology and neurite growth were observed by a scanning electron microscope. It was found that immobilizing lysine onto the EVAL membranes could improve neuronal MTT reduction activity and delay the death rate of neurons. In addition, neurons seeded on the lysine-immobilized EVAL membrane were able to regenerate with the formation of an extensive neuritic network, indicating that the surface modification on the EVAL membrane should be useful for culturing of neurons. Furthermore, the influence exerted by the modification of different amino acids (glycine, arginine and ornithine) onto the EVAL membranes on the neuronal behavior were investigated. We found that the effect of the terminal primary amine of the side chain of the basic amino acids on the neuronal behavior should be taken into account because the immobilized glycine molecules did not improve neuronal cultures. In order to interpret the phenomenon further, in the surface modification process, both the two amino groups of lysine were designed to react with the EVAL membrane surface to form a cyclic structure. On such a surface, neuronal MTT reduction activity was decreased and neuronal death was not delayed. The result shows that the lysine molecules immobilized on the EVAL membrane surface can mediate cellular response to promote neuronal cell survival and guidance of neuritic processes, indicating a delicate interaction of neuron with lysine molecules on the EVAL membrane surface.

Animals↗

PubMed2003

Kinetic modelling of blood glucose variation in a bioartificial pancreas.

Methods are presented for assessing the performance of biomaterials for a bioartificial pancreas using a kinetic model of blood glucose variation. The model is composed of simultaneous differential equations that simulate variation of blood glucose concentration of rats outside the biomaterial and decrease of islet number inside the biomaterial. The resulting calculations agree well with the in vivo experimental data and indicate that the characteristics of bioartificial pancreas can be expressed as the actually working number of islets from the viewpoint of rats, regardless of the functioning of the bioartificial pancreas. The contributions of the capability of a biomaterial permeable to insulin and against immune rejection, and other factors that may induce cell death were involved in the actually working number of islets, i.e., the model used a lumped-parameter expression for assessment of the performance of biomaterials for a bioartificial pancreas. This model would be useful as a research tool for analysis of clinical investigation of bioartificial pancreas and physiological significance of blood glucose variation dynamics.

Animals↗