Biomedical subjects

S T Yang

Publications and source records attributed to S T Yang.

At least 19 recordsLinked to original sources

PubMed2004

Separation of benzene, toluene, ethylbenzene, and xylenes by micellar electrokinetic capillary chromatography.

The use of sodium dodecyl sulfate, urea, beta-cyclodextrin, and methanol as additives to the electrophoretic medium containing a Na2HPO4-boric acid buffer in the micellar electrokinetic capillary chromatography of benzene, toluene, ethylbenzene, and three isomers of xylene (collectively known as BTEX) was investigated. The results showed that with the addition of sodium dodecyl sulfate only, higher selectivity and sensitivity and shorter migration time could be achieved, which consequently resulted in better separation of BTEX studied. For this buffer system, good linearity (R2>0.99) was found over the range of 5 to 500 microg ml(-1) for individual BTEX compound and separation time of less than 5 min for BTEX was possible.

Benzene↗

PubMed2003

Boerhaave's syndrome presenting as a right-sided pleural effusion.

INTRODUCTION: Boerhaave's syndrome is an uncommon condition where there is oesophageal rupture following forceful vomiting, subsequent mediastinitis and is associated with high mortality and morbidity in the absence of therapy. We present a case of Boerhaave's syndrome in a 79-year-old woman who developed a right-sided effusion, an unusual presentation. CLINICAL PICTURE: A 79-year-old woman developed a right-sided empyema and mediastinitis after a bout of repeated vomiting. Gastrograffin swallows and oesophago-gastroduodenoscopy confirmed oesophageal rupture. TREATMENT: The patient was treated with antibiotics and a tube thoracostomy. An open thoracotomy, oesophagostomy and thoracic window was subsequently performed. OUTCOME: The oesophageal rupture was contained but patient died from postoperative complications. CONCLUSIONS: Physicians should have a high index of suspicion of oesophageal rupture when patients present with Meckler's triad of symptoms and especially when pleural fluid cultures grow bacteria native to the gastrointestinal tract.

Aged↗

PubMed2001

Vascular endothelial growth factor isoforms display distinct activities in promoting tumor angiogenesis at different anatomic sites.

The gene for the major angiogenic factor, vascular endothelial growth factor (VEGF), encodes several spliced isoforms. We reported previously that overexpression of two VEGF isoforms, VEGF(121) and VEGF(165), by human glioma U87 MG cells induced tumor-associated intracerebral hemorrhage, whereas expression of a third form, VEGF(189), did not cause vessel rupture. Here, we test whether these VEGF isoforms have distinct activities for enhancing vascularization and growth of gliomas in mice. U87 MG cells that overexpressed VEGF(165) or VEGF(189) grew more rapidly than the parental cells in both s.c. and intracranial (i.c.) locations. However, cells that overexpressed VEGF(121) only showed enhancement of i.c. tumor growth but had a minimal effect on s.c. glioma progression. At both anatomical sties, VEGF(165) and VEGF(189) strongly augmented neovascularization, whereas VEGF(121) only increased vessel density in brain tumors. In each type of glioma, expression of VEGF receptors -1 and -2 largely phenocopied the tumor vasculature, because increased VEGF/VEGF receptor-activated microvessel densities were strongly correlated with the angiogenicity and tumorigenicity elicited by the VEGF isoforms at both anatomical sites. One notable difference between the sites was the expression of vitronectin, a prototypic ligand of alpha(v)beta(3) and alpha(v)beta(5) integrins, detected in i.c. but not in s.c., gliomas. Endothelial cell migration stimulated by VEGF(121) was potentiated by vitronectin to a greater extent than that stimulated by VEGF(165). This data demonstrates that VEGF isoforms have distinct activities at different anatomical sites and suggest that the microenvironment of different tissues affects the function of VEGF isoforms.

Animals↗

PubMed2001

Structure-activity analysis of SMAP-29, a sheep leukocytes-derived antimicrobial peptide.

SAMP-29 is a cathelecidin-derived antimicrobial peptide deduced from sheep myeloid mRNA. To elucidate the structural-activity relationship of SMAP-29, several analogues were synthesized and their antibiotic activity was investigated. Compared to parental SMAP-29, SMAP-29(1-17) and [K(22,25,27)]-SMAP-29 retained relatively effective antimicrobial activity (MIC: 1.0-8.0 microM), but resulted in a complete loss of hemolytic activity. Pro-19 --> Ala substitution ([A19]-SMAP-29) in SMAP-29 induced a significant reduction in antibacterial activity. These results suggested that the N-terminal amphipathic alpha-helical region and the C-terminal hydrophobic region of SMAP-29 are responsible for antimicrobial activity and hemolytic activity, respectively, and the central Pro-19 in SMAP-29 plays a critical role in showing improved antibacterial activity. In particular, [K(2,7,13)]-SMAP-29(1-17) showed potent antimicrobial activity under high salt conditions without hemolytic activity. Thus, this short peptide could serve as an attractive candidate for the development of therapeutic antimicrobial drugs. Structural analysis by circular dichroism suggested that SMAP-29 seems to adopt a helix-bend/turn-extended random conformation.

Amino Acid Sequence↗

PubMed2001

Thermal compression and characterization of three-dimensional nonwoven PET matrices as tissue engineering scaffolds.

Nonwoven fibrous matrices have been widely used as scaffolds in tissue engineering, and modification of microstructure of these matrices is needed to organize cells in three-dimensional space with spatially balanced proliferation and differentiation required for functional tissue development. The method of thermal compression of nonwoven polyethylene terephthalate (PET) fabrics was developed and key parameters of temperature, pressure, and compression duration were evaluated in this study. The permanent deformation was obtained at elevated temperature under pressure and the viscoelastic compressional behaviors were observed, characterized by a distinct apparent modulus change in glass transition temperature region. A liquid extrusion method was further employed to analyze both pore size and its distribution for matrices with porosity ranging from 84 to 93%. It is also found that a more uniformly distributed pore size was resulted from thermal compression and the isotropic nature of nonwoven fabrics was preserved because of the proportional reduction of the pore by compression. The thermally compressed fabric matrices with two different pore sizes (15 and 20 microm in pore radius) were used to culture human trophoblast ED27 and NIH 3T3 cells. It was found that cells cultured in the different pore-size PET matrices had different cell spatial organization and proliferation rates. The smaller pores in the matrix allowed cells to spread better and proliferate faster, while cells in the larger pores tended to form large aggregates and had lower proliferation rate. The thermal compression technique also can be applied to other synthetic fibrous matrices including biodegradable polymers used in tissue engineering to modify the microstructure according to their viscoelastic properties.

3T3 Cells↗

PubMed2001

Genetic diversity among different clones of the gynogenetic silver crucian carp, Carassius auratus gibelio, revealed by transferrin and isozyme markers.

Genetic diversity among four clones (A, D, E, F) of gynogenetic silver crucian carp was studied using transferrin and isozymes in the blood as markers. Of the five proteins investigated, three (transferrin, esterase and superoxide dismutase) indicated polymorphism and eight polymorphic loci were detected. These loci were probably encoded by codominant alleles and their inheritance patterns were analyzed. Intraclonal homogeneity and interclonal heterogeneity were observed in these clones, which allowed us to infer the clonal nature and evolutionary relationship between them. Clonal diversity in this population of silver crucian carp in China was also compared with data reported from gynogenetic crucian carp in Germany.

Alleles↗

PubMed2001

Antibacterial, antitumor and hemolytic activities of alpha-helical antibiotic peptide, P18 and its analogs.

The alpha-helical antibiotic peptide (P18: KWKLFKKIPKFLHLAKKF-NH2) designed from the cecropin A(1-8)-magainin 2 (1-12) hybrid displayed strong bactericidal and tumoricidal activity without inducing hemolysis. The effect of the Pro9 residue at central position of P18 on cell selectivity was investigated by Pro9 --> Leu or Pro9 --> Ser substitution. Either substitution markedly reduced the antibacterial activity of P18 and increased hemolysis, although it did not significantly affect cytotoxicity against human transformed tumor and normal fibroblast cells. These results suggest that a proline kink in alpha-helical antibiotic peptide P18 serves as a hinge region to facilitate ion channel formation on bacterial cell membranes and thus plays an important role in providing high selectivity against bacterial cells. Furthermore, to investigate the structure-antibiotic activity relationships of P18, a series of N- or C-terminal deletion and substitution analogs of P18 were synthesized. The C-terminal region of P18 was related to its antibiotic activity and alpha-helical conformation on lipid membranes rather than N-terminal one. Higher alpha-helicity of the peptides was involved in the hemolytic and antitumor activity rather than antibacterial activity. Except for [L9]-P18 and [S9]-P18, all the designed peptides containing a Pro residue showed potent antibacterial activity, although they did not induce a cytolytic effect against human erythrocyte and normal fibroblast cells at the concentration required to kill bacteria. In particular, P18 and some analogs (N-1, N-2, N-3, N-3L and N-4L) with potent bactericidal and tumoricidal activity and little or no normal cell toxicity may serve as an attractive candidate for the development of novel anti-infective or antitumor agents.

Amino Acid Sequence↗

PubMed2001

Differential screening and characterization analysis of the egg envelope glycoprotein ZP3 cDNAs between gynogenetic and gonochoristic crucian carp.

Gynogenetic silver crucian carp, Carassius auratus gibelio, is an intriguing model system. In the present work, a systemic study has been initiated by introducing suppression subtractive hybridization technique into this model system to identify the differentially expressed genes in oocytes between gynogenetic silver crucian carp and its closely related gonochoristic color crucian carp. Five differential cDNA fragments were identified from the preliminary screening, and two of them are ZP3 homologues. Moreover, the full length ZP3 cDNAs were cloned from their oocyte cDNA libraries. The length of ZP3 cDNAs were 1378 bp for gyno-carp and 1367 bp for gono-carp, and they can be translated into proteins with 435 amino acids. Obvious differences are not only in the composition of amino acids, but also in the number of potential O-linked oligosaccharide sites. In addition, gyno-carp ZP3 amino acid sequence has an unexpected higher identity value with common carp (83.5%) than that with the closely related gono-carp (74.7%). The unique homology may be originated from the ancient hybridization. Northern blot analysis confirmed that expression of the ZP3 gene occurred exclusively in the oocytes. Because O-linked oligosaccharides on ZP3 have been demonstrated to play very important roles in fertilization, it is suggested that the extra O-linked glycosylation sites may be related to the unique sperm-egg recognition mechanism in gynogenesis.

Amino Acid Sequence↗

PubMed2001

Oxygen tension influences proliferation and differentiation in a tissue-engineered model of placental trophoblast-like cells.

A considerable oxygen gradient exists in vivo, which exerts regulatory effects on tissue development and function. The objective of this study was to evaluate the feasibility of controlling cell proliferation and differentiation by regulating oxygen tension in a tissue-engineered bioreactor model. The effects of oxygen tension on proliferation and differentiation of first-trimester human trophoblast cells (known as ED(27) cells) were studied in a fiber-bed perfusion bioreactor system in which cells were grown in polyethylene terephthalate (PET) nonwoven fibrous matrix. By varying the oxygen tension between 2% and 20%, differential responses of trophoblasts in their proliferation and differentiation activities were observed. There was no significant difference in the rates of glucose consumption and lactate production, and lactate dehydrogenase (LDH) level in the culture media for both 2% and 20% oxygen tension cultures, indicating that cell metabolic activities were not limited by low oxygen tension. However, 2% oxygen stimulated cell proliferation but impeded the secretion of a functional hormone, 17beta-estradiol. In contrast, 20% oxygen tension reduced cell proliferation, but yielded higher hormone secretion. A step change in oxygen tension from 2% to 20% caused cells in the bioreactor to increase 17beta-estradiol secretion and shifted cell cycle from proliferation to differentiation, which were verified with the expression levels of cyclin B1 and p27(kip1). However, no significant response to a change from 6% to 20% oxygen tension was observed. It is concluded that changes in oxygen tension can be an effective strategy to control cell cycle and long-term tissue development. This work also demonstrated the important role of oxygen tension in regulating placental trophoblast tissue development and the feasibility of using the bioreactor under well-controlled physiological environment for tissue engineering applications.

Bioreactors↗

PubMed2001

Three-dimensional cell-scaffold constructs promote efficient gene transfection: implications for cell-based gene therapy.

To date, introduction of gene-modified cells in vivo is still a critical limitation for cell-based gene therapy. In this study, based on tissue engineering techniques, we developed a three-dimensional (3-D) transfection system to be cell-based gene delivery vehicle. Human trophoblast-like ED(27) and fibroblastic NIH3T3 cells were used as model cell lines. Cells were seeded onto PET fibrous matrices and plated on polyethylene terephathalate (PET) films as 2-D transfection control. The cell-matrices and cell-films were transfected with pCMV-betagal and pEGFP (green fluorescent protein) reporter gene vectors using LipofectAmine reagent. Gene expression on 3-D versus 2-D growth surface were investigated. The effects of seeding method, seeding density, porosity of the PET matrix, and culturing time of the cell-matrix complex on cDNA transfection and expression in the 3-D cell-matrix complex were also investigated. The beta-gal assay and GFP detection showed that 3-D transfection promoted a higher gene expression level and longer expression time as compared to 2-D transfection. There existed an optimal initial cell seeding density for gene transfection of 3-D cell-matrix complex. Cells seeded on PET matrices with a lower porosity ( approximately 87%) had higher gene expression activities than cells in the matrices with a higher porosity ( approximately 90%). Also, Higher gene expression levels of beta-gal were obtained for the more uniformly seeded matrices that were seeded with a depth-filtration method. The results from this study demonstrate the potential utility of cells seeded onto 3-D fibrous matrices as cell-based gene delivery vehicle for in vitro study of gene expression or in vivo gene therapy.

3T3 Cells↗

PubMed2001

Human cord cell hematopoiesis in three-dimensional nonwoven fibrous matrices: in vitro simulation of the marrow microenvironment.

Current hematopoietic culture systems mainly utilize two-dimensional devices with limited ability to promote self-renewal of early progenitors. In vivo-like three-dimensional (3-D) culture environments might be conducive to regulating stem cell proliferation and differentiation similar to in vivo hematopoiesis. The few 3-D cultures reported in the literature either produced few progenitors or provided little information about microenvironment. In this study, we constructed a 3-D hematopoietic microenvironment composed of nonwoven matrix and human cord blood (CB) cells to simulate the marrow microenvironment and expand cord progenitors. Nonwoven polyethylene terephthalate (PET) fabric with defined microstructure was used as the 3-D scaffold and the PET surface was modified by hydrolysis to improve cell adhesion. Different cell organizations were formed in a 3-D matrix in a developmental manner, from individual cells and cells bridging between fibers to large cell aggregates. Both stromal and hematopoietic cells were distributed spatially within the scaffold. Compared to two-dimensional (2-D) CD34(+) cell culture, 3-D culture produced 30-100% higher total cells and progenitors without exogenous cytokines. With thrombopoietin and flt-3/flk-2 ligand, it supported two- to three-fold higher total cell number (62.1- vs. 24.6-fold), CD34(+) cell number (6.8- vs. 2.8-fold) and colony-forming unit (CFU) number for 7-9 weeks (n = 6), indicating a hematopoiesis pathway that promoted progenitor production. Culture in 3-D nonwoven matrices enhanced cell-cell and cell-matrix interactions and allowed 3-D distribution of stromal and hematopoietic cells. The formation of cell aggregates and higher progenitor content indicated that the spatial microenvironment in 3-D culture played an important role in promoting hematopoiesis. This 3-D culture system can be used as an in vitro model to study stem cell or progenitor behavior, and to achieve sustained progenitor expansion.

Biocompatible Materials↗

PubMed2001

Therapeutic zygapophyseal joint injections for headaches emanating from the C2-3 joint.

OBJECTIVE: To report our experience using fluoroscopically guided therapeutic intra-articular C2-3 zygapophyseal joint injections in patients with chronic headaches after a whiplash event. DESIGN: Restrospective study (n = 18 patients) with independent clinical review. Each patient experienced persistent daily headache symptoms which failed to improve after at least 3 mo of physical therapy, activity restriction, and the use of oral analgesics. Each patient demonstrated initially a positive response to a diagnostic intra-articular C2-3 joint injection. Data collection and analysis were performed by an independent clinical reviewer. Outcome measures included headache frequency, medication usage, symptom response to medication, and employment status. RESULTS: Patients' symptom duration before diagnostic injection averaged 34 mo. Follow-up data collection transpired at an average of 19 mo after the final therapeutic injection. In 61% of patients, fewer than three headaches were experienced each week; these headaches were relieved with the use of oral analgesics. CONCLUSIONS: Although the inherent limitations of this study preclude a definitive statement regarding the efficacy of C2-3 injections, these initial findings suggest that therapeutic intra-articular zygapophyseal joint injections are effective in the treatment of headaches emanating from the C2-3 joint after a whiplash event. Future controlled, prospective studies are necessary to clarify the role of such injections in this challenging patient population.

Adult↗

PubMed2000

Effects of pore size in 3-D fibrous matrix on human trophoblast tissue development.

The effects of pore size in a 3-D polyethylene terephthalate (PET) nonwoven fibrous matrix on long-term tissue development of human trophoblast ED27 cells were studied. Thermal compression was used to modify the porosity and pore size of the PET matrix. The pore size distributions in PET matrices were quantified using a liquid extrusion method. Cell metabolic activities, estradiol production, and cell proliferation and differentiation were studied for ED27 cells cultured in the thermally compressed PET matrices with known pore structure characteristics. In general, metabolic activities and proliferation rate were higher initially for cultures grown in the low-porosity (LP) PET matrix (porosity of 0.849, average pore size of 30 microm in diameter) than those in the high-porosity (HP) matrix (porosity of 0.896, average pore size of 39 microm in diameter). However, 17beta-estradiol production and cell differentiation activity in the HP matrix surpassed those in the LP matrix after 12 days. The expression levels of cyclin B1 and p27kip1 in cells revealed progressively decreasing proliferation and increasing differentiation activities for cells grown in PET matrices. Also, difference in pore size controlled the cell spatial organization in the PET matrices and contributed to the tissue development in varying degrees of proliferation and differentiation. It was also found that cells grown on the 2-D surface behaved differently in cell cycle progression and did not show increased differentiation activities after growth had stopped and proliferation activities had lowered to a minimal level. The results from this study suggest that the 3-D cell organization guided by the tissue scaffold is important to tissue formation in vitro.

Blotting, Western↗

PubMed2000

Ethanol potentiates dopamine release during acute hypoxia in rat striatum.

We, and others, have previously demonstrated that N-methyl-D-aspartate (NMDA) receptor is involved in hypoxia or ischemia-mediated responses. We found that the NMDA antagonist ketamine attenuates cortical nitric oxide release during cerebroischemia. It has been reported that ethanol (EtOH) antagonizes NMDA-induced responses in various systems. In the present study, the interaction of EtOH and KCl-evoked striatal dopamine release in vivo during acute hypoxia was examined. High-speed chronoamperometric recording techniques, using Nafion-coated carbon fiber electrodes, were used to evaluate extracellular dopamine (DA) concentration in the striatum of urethane-anesthetized Sprague-Dawley rats. KCl was directly applied to the striatum to evoke release of DA. These anesthetized animals were paralyzed with d-tubocurarine and connected to a respirator to allow controlled respiration. Systemic concentrations of oxygen were altered by changing the rate of the respirator. We previously reported that lowering the respiratory rates from 90 to 20 times/min for 5 min decreased arterial PO(2) and facilitated KCl-induced DA release in the striatum. In this study, we found that application of NMDA antagonist MK801 attenuates hypoxic DA release, suggesting that NMDA receptor is involved in this hypoxic reaction. In contrast, EtOH dose dependently enhanced KCl-evoked DA release during hypoxia. To further examine the interactions of excitatory amino acid and EtOH on DA release, glutamate was locally applied to the striatum. Glutamate-induced DA release was not affected by the systemic application of EtOH. Taken together, these data suggest that EtOH enhances DA release in vivo during short-term hypoxia, possibly through mechanisms other than excitatory amino acid pathways.

Animals↗

PubMed2000

Design and performance of a fibrous bed bioreactor for odor treatment.

Biological processes have become popular for odor treatment. In this study, a novel fibrous bed bioreactor was applied for treatment of odorous gas. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized. The first stage of this work comprised a preliminary study that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs). In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3.h) was studied. VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3.h). At a mass loading of 104.2 g/(m3.h), removal efficiency was found to be 87.7%. In the second stage of the work, the process was scaled up with design and operational considerations, namely, packing medium, process condition, and configuration selections. A trickling biofilter with synthetic fibrous packing medium was selected. It was operated under countercurrent flow of gas and liquid streams. The effects of inlet concentration and empty bed retention time on bioreactor performance were studied. The bioreactor was effective in treating odorous VFAs at mass loadings up to 32 g/(m3.h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degrade all the VFAs introduced. Although VFAs accumulated in the liquid phase, the removal efficiency remained above 99%, implying that the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process. The bioreactor was stable for long-term operation; no clogging and degeneration of the packing medium was observed during the 4-mo operation.

Bioreactors↗

PubMed1999

Biodegradation of benzene, toluene, ethylbenzene, and o-xylene by a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in a fibrous-bed bioreactor.

A fibrous-bed bioreactor containing the coculture of Pseudomonas putida and P. fluorescens immobilized in a fibrous matrix was developed to degrade benzene (B), toluene (T), ethylbenzene (E), and o-xylene (X) in synthetic waste streams. The kinetics of BTEX biodegradation by immobilized cells adapted in the fibrous-bed bioreactor and free cells grown in serum bottles were studied. In general, the BTEX biodegradation rate increased with increasing substrate concentration and then decreased after reaching a maximum, showing substrate-inhibition kinetics. However, for immobilized cells, the degradation rate was much higher than that of free cells. Compared to free cells, immobilized cells in the bioreactor tolerated higher concentrations (> 1000 mg l-1) of benzene and toluene, and gave at least 16-fold higher degradation rates for benzene, ethylbenzene, and o-xylene, and a 9-fold higher degradation rate for toluene. Complete and simultaneous degradation of BTEX mixture was achieved in the bioreactor under hypoxic conditions. Cells in the bioreactor were relatively insensitive to benzene toxicity; this insensitivity was attributed to adaptation of the cells in the bioreactor. Compared to the original seeding culture, the adapted cells from the fibrous-bed bioreactor had higher specific growth rate, benzene degradation rate, and cell yield when the benzene concentration was higher than 100 mg l-1. Cells in the fibrous bed had a long, slim morphology, which is different from the normal short-rod shape found for suspended cells in solution.

Benzene↗

PubMed1999

Biocatalytic production of chiral epichlorohydrin in organic solvents.

Enantioselective hydrolysis of racemic epichlorohydrin was accomplished for the production of enantiopure epichlorohydrin using the whole cells of an isolated Aspergillus niger spps. To overcome the spontaneous chemical degradation of epichlorohydrin that occurs in aqueous buffer, organic solvents were employed in the reaction medium. The enantioselectivity was highly dependent on the solvent structure, water content of the medium, and the initial epichlorohydrin concentration. (S)-epichlorohydrin could be obtained from its racemates (60 mM) with an optical purity of 100% enantiomeric excess (ee) and 20% yield in cyclohexane supplemented with 2.0% (v/v) water.

Journal Article↗

PubMed1999

Development of an in vitro human placenta model by the cultivation of human trophoblasts in a fiber-based bioreactor system.

The in vitro human trophoblast culture system is of significant importance in the study of human placenta development and its role as the transport organ between maternal and fetal circulations in normal physiology and pathology pregnancy. But conventional in vitro model systems fail to reproduce many important features of human placenta in vivo. In our study, a perfusion bioreactor system was developed with a chemically modified poly(ethylene terephthalate) (PET) fibrous matrix as the cell culture scaffold. The dual compartment design of the bioreactor simulates maternal and fetal circulation systems in vivo. First trimester human trophoblast cells readily attached on a chemically modified PET fiber surface. The detection of human fibronectin showed that cells were able to form three-dimensional structures by aggregation and bridging between fibers. Moreover, metabolic and hormone secretion data showed that cells in this perfusion culture system maintained their normal functional activities. The results of this study demonstrate the feasibility of tissue engineering human trophoblast cells in a perfusion bioreactor system for the development of an in vitro drug testing model system.

Biocompatible Materials↗