Enzymatic cross-linking versus radical polymerization in the preparation of gelatin PolyHIPEs and their performance as scaffolds in the culture of hepatocytes

Highly open porous biodegradable scaffolds, based on gelatin A3, were fabricated with the aim of using them for tissue-engineering applications. The fabrication process is based on an emulsion-templating technique. In the preparation of gelatin scaffolds two different cross-linking procedures were adopted: (I) radical polymerization of the methacrylate functionalities, previously introduced onto the gelatin chains and (II) formation of isopeptide bridges among the gelatin chains promoted by the enzyme microbial transglutaminase. The method of cross-linking exerts a pronounced effect on the morphology of the porous biomaterials: radical polymerization of methacrylated gelatin allowed the production of scaffolds with a better defined porous structure, while the enzymatically cross-linked scaffolds were characterized by a thinner skeletal framework. A suitable sample of each kind of the differently cross-linked porous biomaterials was tested for the culture of hepatocytes. The scaffold obtained by radical polymerization possessed a morphology characterized by relatively large voids and interconnects, and as a consequence, it was more suitable for hepatocytes colonization. On the other hand, the enzymatically cross-linked scaffold resulted in less cytotoxicity and the cultured hepatocytes expressed a better differentiated phenotype, as evidenced by a greater expression and more correct localization of key adhesion proteins.     

Electrospun scaffold tailored for tissue-specific extracellular matrix

The natural extracellular matrix (ECM) is a complex structure that is built to meet the specific requirements of the tissue and organ. Primarily consisting of nanometer diameter fibrils, ECM may contain other vital substances such as proteoglycans, glycosaminoglycan and various minerals. Current research in tissue engineering involves trying to replicate the ECM such that it provides the environment for tissue regeneration. Electrospinning is a versatile process that results in nanofibers by applying a high voltage to electrically charge a liquid. A variety of polymers and other substances have been incorporated into the artificial nanofibrous scaffold. Surface modification and cross-linking of the nanofibers are some ways to improve the biocompatibility and stability of the scaffold. Electrospun scaffolds with oriented nanofibers and other assemblies can be constructed by modifying the electrospinning setup. Using electrospinning, researchers are able to specifically tailor the electrospun scaffold to meet the requirements of the tissue that they seek to regenerate. In vitro and in vivo experiments demonstrate that electrospun scaffolds hold great potential for tissue engineering applications.     

Formation of collagen-glycosaminoglycan blended nanofibrous scaffolds and their biological properties

The development of blended collagen and glycosaminoglycan (GAG) scaffolds can potentially be used in many soft tissue engineering applications since the scaffolds mimic the structure and biological function of native extracellular matrix (ECM). In this study, we were able to obtain novel nanofibrous collagen-GAG scaffolds by electrospinning collagen blended with chondroitin sulfate (CS), a widely used GAG, in a mixed solvent of trifluoroethanol and water. The electrospun collagen-GAG scaffold with 4% CS (COLL-CS-04) exhibited a uniform fiber structure with nanoscale diameters. A second collagen-GAG scaffold with 10% CS consisted of smaller diameter fibers but exhibited a broader diameter distribution due to the different solution properties in comparison with COLL-CS-04. After cross-linking with glutaraldehyde vapor, the collagen-GAG scaffolds became more biostable and were resistant to collagenase degradation. This is evidently a more favorable environment allowing increased proliferation of rabbit conjunctiva fibroblast on the scaffolds. Incorporation of CS into collagen nanofibers without cross-linking did not increase the biostability but still promoted cell growth. The potential of applying the nanoscale collagen-GAG scaffold in tissue engineering is significant since the nanodimension fibers made of natural ECM mimic closely the native ECM found in the human body. The high surface area characteristic of this scaffold may maximize cell-ECM interaction and promote tissue regeneration faster than other conventional scaffolds.     

Two‐Photon polymerization for microfabrication of three‐dimensional scaffolds for tissue engineering application

In natural tissues cells are embedded in a three‐dimensional fibrous network of biopolymers like collagen, hyaluronic acid etc. This extracellular matrix (ECM) influences the cell fate, the differentiation status, metabolic processes and provides structural integrity. For a three‐dimensional or physiological cell cultivation that are required in biomedical applications (e.g. tissue engineering, BioMEMS) scaffolds are needed. These scaffolds mimic the ECM according to their biocompatibility which comprises aspects of surface compatibility and importantly for tissue engineering applications aspects of structural compatibility. We have evaluated scaffold design parameters for the three‐dimensional cultivation of chondrocytes for the tissue engineering of artificial cartilage. Two‐photon polymerization is a powerful technique for fabrication of polymeric three‐dimensional micro‐ and submicro‐structures. The photoinitiation system for two‐photon polymerization is excited by simultaneous absorption of two photons leading to chemical polymerization reactions. Due to a tight confinement of the excitation volume around the focal point, this method can produce micrometer sized objects maintaining a high spatial resolution down to 100 nm. Two‐photon processes require very high photon densities which are provided by pulsed femtosecond lasers. The potential of this approach for microfabrication of scaffolds for tissue engineering is demonstrated by investigation of the cell response to microstructures with complex three‐dimensional geometry and feature sizes in the range of few micrometers.     

Porous gelatin hydrogels: 2. In vitro cell interaction study

We report on the feasibility of applying porous gelatin hydrogels, prepared by a novel and controlled cryogenic treatment, as cell-interactive scaffolds for tissue engineering applications. Despite the large number of publications on gelatin as a biomaterial, a detailed study of screening a limited number of gelatin scaffolds for their interaction with a panel of human cells has, to the best of our knowledge, not yet been published. In the present work, we have evaluated two types of porous gelatin scaffolds that differ in their pore geometry and pore size. Type I hydrogels contained top-to-bottom transverse channels (i.e. cones) with a decreasing diameter from the top (330 microm) to the bottom (20-30 microm). Type II hydrogels contained spherical pores with a diameter of 135 microm. Both types of scaffolds were evaluated by confocal laser scanning microscopy in terms of adhesion, spreading, and proliferation of human cells (endothelial, epithelial, fibroblast, glial, and osteoblast) by visualizing cells using calcein-acetoxy methyl ester as a vital stain. The results indicated that cells attached, spread, and proliferated on both types of hydrogels. In addition, the scaffolds developed can be used for the long-term culturing of human cells.     

Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate)-based biopolymer systems

Biodegradable biopolymers attract much attention in biology and medicine due to its wide application. The present review considers a biodegradable and biocompatible polymer of bacterial origin, poly(3-hydroxybutyrate), which has wide perspectives in medicine and pharmaceutics. It highlights basic properties of biopolymer (biodegradability and biocompatibility) and also biopolymer systems: various materials, devices and compositions based on the biopolymer. Application of poly(3-hydroxybutyrate)-based biopolymer systems in medicine as surgical implants, in bioengineering as cell culture scaffolds, and in pharmacy as novel drug dosage forms and drug systems are also considered.     

Biomacromolecules electrostatic self-assembly on 3-dimensional tissue engineering scaffold

A poly(ethylenimine) (PEI) was employed to obtain a stable positively charged surface on a poly(D,L-lactide) (PDL-LA) tissue engineering scaffold. An extracellular matrix (ECM)-like biomacromolecule, gelatin, was selected as polyelectrolyte and deposit alternately with PEI on the activated PDL-LA scaffold via ESA technique. The zeta-potential result showed alternating charge of polyelectrolytes (PEI/gelatin) layering on PDL-LA microspheres. Quartz crystal microbalance (QCM) measurement further verified the gradual deposition of PEI/gelatin on the PDL-LA thin film. The combination of PEI aminolysis and the layer-by-layer technique was then explored to construct gelatin coating onto the 3-D porous PDL-LA scaffold. Scanning electronic microscopy showed that there is no notable difference between modified and unmodified PLA scaffolds, with regard to the porosity, pore diameter, and scaffold integration. The dual-tunnel confocal laser scanning microscopy indicated uniform gelatin distribution on the inner surface of the 3-D porous scaffold. The gradual build-up of protein layer on scaffold was investigated by radioiodination technique. Chondrocyte was chosen to test the cell behavior on modified and unmodified PDL-LA scaffolds. The results of the cell viability, total intracellular protein content, and cell morphology on the PEI/gelatin multilayers modified PDL-LA scaffold showed to promote chondrocyte growth. Comparing conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. It may be a promising choice for the surface modification of complex biomedical devices. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.     

Designing a gelatin/chitosan/hyaluronic acid biopolymer using a thermophysical approach for use in tissue engineering

Cell culture on biopolymeric scaffolds has provided treatments for tissue engineering. Biopolymeric mixtures based on gelatin (Ge), chitosan (Ch) and hyaluronic acid (Ha) have been used to make scaffolds for wound healing. Thermal and physical properties of scaffolds prepared with Ge, Ch and Ha were characterized. Thermal characterization was made by using differential scanning calorimetry (DSC), and physical characterization by gas pycnometry and scanning electron microscopy. The effects of Ge content and cross-linking on thermophysical properties were evaluated by means of a factorial experiment design (central composite face centered). Gelatin content was the main factor that affects the thermophysical properties (microstructure and thermal transitions) of the scaffold. The effect of Ge content of the scaffolds for tissue engineering was studied by seeding skin cells on the biopolymers. The cell attachment was not significantly modified at different Ge contents; however, the cell growth rate increased linearly with the decrease of the Ge content. This relationship together with the thermophysical characterization may be used to design scaffolds for tissue engineering.     

The effects of different crossing-linking conditions of genipin on type I collagen scaffolds: an in vitro evaluation

The purpose of this paper is to analyze the properties of fabricating rat tail type I collagen scaffolds cross-linked with genipin under different conditions. The porous genipin cross-linked scaffolds are obtained through a two step freeze-drying process. To find out the optimal cross-link condition, we used different genipin concentrations and various cross-linked temperatures to prepare the scaffolds in this study. The morphologies of the scaffolds were characterized by scanning electron microscope, and the mechanical properties of the scaffolds were evaluated under dynamic compression. Additionally, the cross-linking degree was assessed by ninhydrin assay. To investigate the swelling ratio and the in vitro degradation of the collagen scaffold, the tests were also carried out by immersion of the scaffolds in a PBS solution or digestion in a type I collagenase respectively. The morphologies of the non-cross-linked scaffolds presented a lattice-like structure while the cross-linked ones displayed a sheet-like framework. The morphology of the genipin cross-linked scaffolds could be significantly changed by either increasing genipin concentration or the temperature. The swelling ratio of each cross-linked scaffold was much lower than that of the control (non-cross-linked).The ninhydrin assay demonstrated that the higher temperature and genipin concentration could obviously increase the cross-linking efficiency. The in vitro degradation studies indicated that genipin cross-linking can effectively elevate the biostability of the scaffolds. The biocompatibility and cytotoxicity of the scaffolds was evaluated by culturing rat chondrocytes on the scaffold in vitro and by MTT. The results of MTT and the fact that the chondrocytes adhered well to the scaffolds demonstrated that genipin cross-linked scaffolds possessed an excellent biocompatibility and low cytotoxicity. Based on these results, 0.3 % genipin concentrations and 37 °C cross-linked temperatures are recommended.     

Biocompatibility of hydrogel-based scaffolds for tissue engineering applications

Recently, understanding of the extracellular matrix (ECM) has expanded rapidly due to the accessibility of cellular and molecular techniques and the growing potential and value for hydrogels in tissue engineering. The fabrication of hydrogel-based cellular scaffolds for the generation of bioengineered tissues has been based on knowledge of the composition and structure of ECM. Attempts at recreating ECM have used either naturally-derived ECM components or synthetic polymers with structural integrity derived from hydrogels. Due to their increasing use, their biocompatibility has been questioned since the use of these biomaterials needs to be effective and safe. It is not surprising then that the evaluation of biocompatibility of these types of biomaterials for regenerative and tissue engineering applications has been expanded from being primarily investigated in a laboratory setting to being applied in the multi-billion dollar medicinal industry. This review will aid in the improvement of design of non-invasive, smart hydrogels that can be utilized for tissue engineering and other biomedical applications. In this review, the biocompatibility of hydrogels and design criteria for fabricating effective scaffolds are examined. Examples of natural and synthetic hydrogels, their biocompatibility and use in tissue engineering are discussed. The merits and clinical complications of hydrogel scaffold use are also reviewed. The article concludes with a future outlook of the field of biocompatibility within the context of hydrogel-based scaffolds.     

Improvement of biomaterials used in tissue engineering by an ageing treatment

Biomaterials based on crosslinked sponges of biopolymers have been extensively used as scaffolds to culture mammal cells. It is well known that single biopolymers show significant change over time due to a phenomenon called physical ageing. In this research, it was verified that scaffolds used for skin tissue engineering (based on gelatin, chitosan and hyaluronic acid) express an ageing-like phenomenon. Treatments based on ageing of scaffolds improve the behavior of skin-cells for tissue engineering purposes. Physical ageing of dry scaffolds was studied by differential scanning calorimetry and was modeled with ageing kinetic equations. In addition, the physical properties of wet scaffolds also changed with the ageing treatments. Scaffolds were aged up to 3 weeks, and then skin-cells (fibroblasts) were seeded on them. Results indicated that adhesion, migration, viability, proliferation and spreading of the skin-cells were affected by the scaffold ageing. The best performance was obtained with a 2-week aged scaffold (under cell culture conditions). The cell viability inside the scaffold was increased from 60 % (scaffold without ageing treatment) to 80 %. It is concluded that biopolymeric scaffolds can be modified by means of an ageing treatment, which changes the behavior of the cells seeded on them. The ageing treatment under cell culture conditions might become a bioprocess to improve the scaffolds used for tissue engineering and regenerative medicine.     

Encapsulation of osteoblast seeded microcarriers into injectable, photopolymerizable three-dimensional scaffolds based on d,l-lactide and epsilon-caprolactone

UMR-106 seeded microcarriers were encapsulated into in situ, photopolymerizable three-dimensional scaffolds based on d,l-lactide and epsilon-caprolactone. UMR-106 and rat bone marrow cells proliferated and differentiated well on the microcarriers. The microcarriers were completely colonized after 14 days in culture. The viscous polymer paste allowed to mix the UMR-106 seeded microcarriers and gelatin (porosigen) properly. After the photopolymerization process, microcarriers and gelatin were evenly distributed throughout the scaffold. Gelatin was leached out within 7 h, and a porous scaffold was obtained. The microcarriers remained in the scaffold even after 7 days which demonstrates that they were well entrapped in the polymer. Increasing the amount of entrapped microcarriers (20-50%) leads to scaffolds with a reduced cross-linking. Hence, the microcarriers leached out. The encapsulated UMR-106 cells did not show pyknotic nuclei which demonstrates that the photopolymerization and handling the viscous polymer/gelatin/microcarrier paste is not detrimental for the cells.     

Hydrophilic gelatin and hyaluronic acid-treated PLGA scaffolds for cartilage tissue engineering

Tissue engineering provides a new strategy for repairing damaged cartilage. Surface and mechanical properties of scaffolds play important roles in inducing cell growth.?Aim: The aim of this study was to fabricate and characterize PLGA and gelatin/hyaluronic acid-treated PLGA (PLGA-GH) sponge scaffolds for articular cartilage tissue engineering. Methods: The PLGA-GH scaffolds were cross-linked with gelatin and hyaluronic acid. Primary chondrocytes isolated from porcine articular cartilages were used to assess cell compatibility. The characteristic PLGA-GH scaffold was higher in water uptake ratio and degradation rate within 42 days than the PLGA scaffold. Results: The mean compressive moduli of PLGA and PLGA-GH scaffolds were 1.72±0.50 MPa and 1.86±0.90 MPa, respectively. The cell attachment ratio, proliferation, and extracellular matrix secretion on PLGA-GH scaffolds are superior to those of PLGA scaffolds. Conclusions: In our study, PLGA-GH scaffolds exhibited improvements in cell biocompatibility, cell proliferation, extracellular matrix synthesis, and appropriate mechanical and structural properties for potential engineering cartilage applications.     

Gelatin interpenetration in poly N-isopropylacrylamide network reduces the compressive modulus of the scaffold: A property employed to mimic hepatic matrix stiffness

The progression of liver disease from normal to cirrhotic state is characterized by modulation of the stiffness of the extracellular matrix (ECM). Mimicking this modulation in vitro scaffold could provide a better insight into hepatic cell behavior. In this study, interpenetrating poly(N-isopropylacrylamide-co-gelatin) cryogels were synthesized in 48 different compositions to yield scaffolds of different properties. It was observed that a high concentration of N-isopropylacrylamide (NIPAAm) leads to the formation of small pores while gelatin interpenetration on poly-NIPAAm framework renders porous structure. Swelling properties and porosity of the gels decreased with an increase in NIPAAm concentration owing to the increased compactness of the gels. Gelatin interpenetration relaxed the gels and enhanced these properties. An increase in gelatin concentration led to a reduction in compressive moduli indicating that gelatin interpenetration in the poly-NIPAAm network softens the cryogel. With the increase in NIPAAm concentration, the effect of gelatin interpenetration in reducing the compressive moduli expanded. The cytocompatibility studies indicated that the gels are cell-adherent and compatible with HepG2. Furthermore, biochemical and real-time polymerase chain reaction studies revealed that HepG2 and Huh-7 cells cultured on scaffolds mimicking the ECM stiffness of normal liver (1.5–2.5 kPa) exhibited optimum liver-specific functionalities. Increasing the stiffness to fibrotic (4–9 kPa) and cirrhotic (10–20 kPa) ECM decreases the functionality.     

Time-lapse confocal reflection microscopy of collagen fibrillogenesis and extracellular matrix assembly in vitro

The development of the next generation of biomaterials for restoration of tissues and organs (i.e., tissue engineering) requires a better understanding of the extracellular matrix (ECM) and its interaction with cells. Extracellular matrix is a macromolecular assembly of natural biopolymers including collagens, glycosaminoglycans (GAGs), proteoglycans (PGs), and glycoproteins. Interestingly, several ECM components have the ability to form three-dimensional (3D), supramolecular matrices (scaffolds) in vitro by a process of self-directed polymerization, "self-assembly". It has been shown previously that 3D matrices with distinct architectural and biological properties can be formed from either purified type I collagen or a complex mixture of interstitial ECM components derived from intestinal submucosa. Unfortunately, many of the imaging and analysis techniques available to study these matrices either are unable to provide insight into 3D preparations or demand efforts that are often prohibitory to observations of living, dynamic systems. This is the first report on the use of reflection imaging at rapid time intervals combined with laser-scanning confocal microscopy for analysis of structural properties and kinetics of collagen and ECM assembly in 3D. We compared time-lapse confocal reflection microscopy (TL-CRM) with a well-established spectrophotometric method for determining the self-assembly properties of both purified type I collagen and soluble interstitial ECM. While both TL-CRM and spectrophotometric techniques provided insight into the kinetics of the polymerization process, only TL-CRM allowed qualitative and quantitative evaluation of the structural parameters (e.g., fibril diameter) and 3D organization (e.g., fibril density) of component fibrils over time. Matrices formed from the complex mixture of soluble interstitial ECM components showed an increased rate of assembly, decreased opacity, decreased fibril diameter, and increased fibril density compared to that of purified type I collagen. These results suggested that the PG/GAG components of soluble interstitial ECM were affecting the polymerization of the component collagens. Therefore, the effects of purified and complex mixtures of PG/GAG components on the assembly properties of type I collagen and interstitial ECM were evaluated. The data confirmed that the presence of PG/GAG components altered the kinetics and the 3D fibril morphology of assembled matrices. In summary, TL-CRM was demonstrated to be a new and useful technique for analysis of the 3D assembly properties of collagen and other natural biopolymers which requires no specimen fixation and/or staining.Copyright 2000 John Wiley & Sons, Inc.     

Biodegradable fumarate-based polyHIPEs as tissue engineering scaffolds

PolyHIPEs show great promise as tissue engineering scaffolds due to the tremendous control of pore size and interconnectivity afforded by this technique. Highly porous, fully biodegradable scaffolds were prepared by polymerization of the continuous phase of high internal phase emulsions (HIPEs) containing the macromer poly(propylene fumarate) (PPF) and the cross-linker propylene fumarate diacrylate (PFDA). Toluene was used as a diluent to reduce the viscosity of the organic phase to enable HIPE formation. A range of polyHIPE scaffolds of different pore sizes and morphologies were generated by varying the diluent concentration (40-60 wt %), cross-linker concentration (25-75 wt %), and macromer molecular weight ( M n = 800-1000 g/mol). Although some formulations resulted in macroporous monoliths (pore diameter >500 microm), the majority of the polyHIPEs studied were rigid, microporous monoliths with average pore diameters in the range 10-300 microm. Gravimetric analysis confirmed the porosity of the microporous monoliths as 80-89% with most scaffolds above 84%. These studies demonstrate that emulsion templating can be used to generate rigid, biodegradable scaffolds with highly interconnected pores suitable for tissue engineering scaffolds.     

Complete recombinant silk-elastinlike protein-based tissue scaffold

Due to their improved biocompatibility and specificity over synthetic materials, protein-based biomaterials, either derived from natural sources or genetically engineered, have been widely fabricated into nanofibrous scaffolds for tissue engineering applications. However, their inferior mechanical properties often require the reinforcement of protein-based tissue scaffolds using synthetic polymers. In this study, we report the electrospinning of a completely recombinant silk-elastinlike protein-based tissue scaffold with excellent mechanical properties and biocompatibility. In particular, SELP-47K containing tandemly repeated polypeptide sequences derived from native silk and elastin was electrospun into nanofibrous scaffolds, and stabilized via chemical vapor treatment and mechanical preconditioning. When fully hydrated in 1× PBS at 37 °C, mechanically preconditioned SELP-47K scaffolds displayed elastic moduli of 3.4-13.2 MPa, ultimate tensile strengths of 5.7-13.5 MPa, deformabilities of 100-130% strain, and resilience of 80.6-86.9%, closely matching or exceeding those of protein-synthetic blend polymeric scaffolds. Additionally, SELP-47K nanofibrous scaffolds promoted cell attachment and growth, demonstrating their in vitro biocompatibility.     

Dependence of invadopodia function on collagen fiber spacing and cross-linking: computational modeling and experimental evidence

Invadopodia are subcellular organelles thought to be critical for extracellular matrix (ECM) degradation and the movement of cells through tissues. Here we examine invadopodia generation, turnover, and function in relation to two structural aspects of the ECM substrates they degrade: cross-linking and fiber density. We set up a cellular automaton computational model that simulates ECM penetration and degradation by invadopodia. Experiments with denatured collagen (gelatin) were used to calibrate the model and demonstrate the inhibitory effect of ECM cross-linking on invadopodia degradation and penetration. Incorporation of dynamic invadopodia behavior into the model amplified the effect of cross-linking on ECM degradation, and was used to model feedback from the ECM. When the model was parameterized with spatial fibrillar dimensions that closely matched the organization, in real life, of native ECM collagen into triple-helical monomers, microfibrils, and macrofibrils, little or no inhibition of invadopodia penetration was observed in simulations of sparse collagen gels, no matter how high the degree of cross-linking. Experimental validation, using live-cell imaging of invadopodia in cells plated on cross-linked gelatin, was consistent with simulations in which ECM cross-linking led to higher rates of both invadopodia retraction and formation. Analyses of invadopodia function from cells plated on cross-linked gelatin and collagen gels under standard concentrations were consistent with simulation results in which sparse collagen gels provided a weak barrier to invadopodia. These results suggest that the organization of collagen, as it may occur in stroma or in vitro collagen gels, forms gaps large enough so as to have little impact on invadopodia penetration/degradation. By contrast, dense ECM, such as gelatin or possibly basement membranes, is an effective obstacle to invadopodia penetration and degradation, particularly when cross-linked. These results provide a novel framework for further studies on ECM structure and modifications that affect invadopodia and tissue invasion by cells.     

Improved cellular response on functionalized polypyrrole interfaces

Neuroregeneration strategies involve multiple factors to stimulate nerve regeneration. Neural support with chemical and physical cues to optimize neural growth and replacing the lesion neuron and axons are crucial for designing neural scaffolds, which is a promising treatment approach. In this study, polypyrrole polymerization and its functionalization at the interface developed by glycine and gelatin for further optimization of cellular response. Nanofibrous scaffolds were fabricated by electrospinning of polyvinyl alcohol and chitosan solutions. The electrospun scaffolds were polymerized on the surface by pyrrole monomers to form an electroactive interface for further applications in neural tissue engineering. The polymerized polypyrrole showed a positive zeta potential value of 57.5 ± 5.46 mV. The in vitro and in vivo biocompatibility of the glycine and gelatin-functionalized polypyrrole-coated scaffolds were evaluated. No inflammatory cells were observed for the implanted scaffolds. Further, DAPI nucleus staining showed a superior cell attachment on the gelatin-functionalized polypyrrole-coated scaffolds. The topography and tuned positively charged polypyrrole interface with gelatin functionalization is expected to be particularly efficient physical and chemical simultaneous factors for promoting neural cell adhesion.     

模拟微重力条件下大鼠肝细胞三维培养支架材料的筛选（简报）

组织工程是一门新兴的边缘学科,它是利用体外培养的人体功能细胞与适当的细胞外基质或支架材料相结合,然后将其移植到体内病损部位以期达到修复目的。微重力组织工程(Microgravity Tissue Engineering)是近年来由美国空间生物技术研究人员开创的一个独特研究领域,其核心技术是