[show abstract][hide abstract] ABSTRACT: Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices.
[show abstract][hide abstract] ABSTRACT: Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE including cell alignment and differentiation. We address the structure and organization of muscle and describe the methods for myoblasts alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and describe different methods to induce myoblast differentiation into myotubes. We then provide an overview of different co-culture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are discussed.
Tissue Engineering Part B Reviews 12/2013; · 4.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: Like a carpet for cells, micropatterned polymeric nanosheets are developed toward local cell delivery. The nanosheets directed morphogenesis of retinal pigment epithelial (RPE) cells and allowed for the injection of an engineered RPE monolayer through syringe needles without loss of cell viability. Such an ultrathin carrier has the promise of a minimally invasive delivery of cells into narrow tissue spaces.
[show abstract][hide abstract] ABSTRACT: In this study we describe the generation and influences on in vitro and in vivo osteogenesis of photo-cured hyaluronic acid (HA) hydrogels loaded with growth and differentiation factor 5 (GDF-5). Prior to loading GDF-5, we characterized the release profiles from these hydrogels and tested their respective cell viability, differentiation and in vivo bone regeneration. The results from this testing indicated that GDF-5 was observed to release in a sustained manner from the HA hydrogels I-III. MTT and live/dead assays showed that the HA hydrogels I-III have good biocompatibility for use as scaffolds for bone tissue regeneration. In vitro cell tests showed a higher level of MC3T3-E1 cell proliferation and differentiation on HA hydrogels I-III than on HA hydrogel 0. Moreover, in vivo animal tests showed that the HA hydrogels I and III had a significant improvement on osteogenesis. Overall, our results suggest that the HA-based hydrogel is a good biomaterial to deliver osteogenic differentiation factors such as GDF-5, and GDF-5 can be useful as an effective alternative to aid new bone formation.
[show abstract][hide abstract] ABSTRACT: Using DNA as programmable, sequence-specific 'glues', shape-controlled hydrogel units are self-assembled into prescribed structures. Here we report that aggregates are produced using hydrogel cubes with edge lengths ranging from 30 μm to 1 mm, demonstrating assembly across scales. In a simple one-pot agitation reaction, 25 dimers are constructed in parallel from 50 distinct hydrogel cube species, demonstrating highly multiplexed assembly. Using hydrogel cuboids displaying face-specific DNA glues, diverse structures are achieved in aqueous and in interfacial agitation systems. These include dimers, extended chains and open network structures in an aqueous system, and dimers, chains of fixed length, T-junctions and square shapes in the interfacial system, demonstrating the versatility of the assembly system.
[show abstract][hide abstract] ABSTRACT: Controlling the cellular microenvironment can be used to direct the cellular organization, thereby improving the function of synthetic tissues in biosensing, biorobotics and regenerative medicine. In this study, we were inspired by the microstructure and biological properties of the extracellular matrix, to develop freestanding ultra-thin polymeric films (referred as "nanomembranes") that were flexible, cell adhesive, and had a morphologically tailorable surface. The resulting nanomembranes were exploited as flexible substrates, on which cell-adhesive micropatterns were generated to align C2C12 skeletal myoblasts and embedded fibril carbon nanotubes (CNTs) enhanced the cellular elongation and differentiation. Functional nanomembranes with tunable morphology and mechanical properties hold great promise in studying cell-substrate interactions and in fabricating biomimetic constructs towards flexible biodevices.
[show abstract][hide abstract] ABSTRACT: Graphene is a novel material whose application in biomedical sciences has only begun to be realized. In the present study, we have employed three-dimensional graphene foams as culture substrates for human mesenchymal stem cells and provide evidence that these materials can maintain stem cell viability and promote osteogenic differentiation.
[show abstract][hide abstract] ABSTRACT: Bone marrow-derived human mesenchymal stem cells (hMSCs) either promote or inhibit cancer progression, depending on factors that heretofore have been undefined. Here we have utilized extreme hypoxia (0.5% O2) and concurrent treatment with metal carcinogen (nickel) to evaluate the passage-dependent response of hMSCs toward cancerous transformation. Effects of hypoxia and nickel treatment on hMSC proliferation, apoptosis, gene and protein expression, replicative senescence, reactive oxygen species (ROS), redox mechanisms, and in vivo tumor growth were analyzed. The behavior of late passage hMSCs in a carcinogenic hypoxia environment follows a profile similar to that of transformed cancer cells (i.e., increased expression of oncogenic proteins, decreased expression of tumor suppressor protein, increased proliferation, decreased apoptosis, and aberrant redox mechanisms), but this effect was not observed in earlier passage control cells. These events resulted in accumulated intracellular ROS in vitro and excessive proliferation in vivo. We suggest a mechanism by which carcinogenic hypoxia modulates the activity of three critical transcription factors (c-MYC, p53, and HIF1), resulting in accumulated ROS and causing hMSCs to undergo cancer-like behavioral changes. This is the first study to utilize carcinogenic hypoxia as an environmentally relevant experimental model for studying the age-dependent cancerous transformation of hMSCs.-Crowder, S. W., Horton, L. W., Lee, H. H., McClain, C. M., Hawkins, O. E., Palmer, A. M. Bae, H., Richmond, A., Sung, H.-J. Passage-dependent cancerous transformation of human mesenchymal stem cells under carcinogenic hypoxia.
[show abstract][hide abstract] ABSTRACT: There is a growing need to understand muscle cell behaviors and to engineer muscle tissues to replace defective tissues in the body. Despite a long history of the clinical use of electric fields for muscle tissues in vivo, electrical stimulation (ES) has recently gained significant attention as a powerful tool for regulating muscle cell behaviors in vitro. ES aims to mimic the electrical environment of electroactive muscle cells (e.g., cardiac or skeletal muscle cells) by helping to regulate cell-cell and cell-extracellular matrix (ECM) interactions. As a result, it can be used to enhance the alignment and differentiation of skeletal or cardiac muscle cells and to aid in engineering of functional muscle tissues. Additionally, ES can be used to control and monitor force generation and electrophysiological activity of muscle tissues for bio-actuation and drug-screening applications in a simple, high-throughput, and reproducible manner. In this review paper, we briefly describe the importance of ES in regulating muscle cell behaviors in vitro, as well as the major challenges and prospective potential associated with ES in the context of muscle tissue engineering.
[show abstract][hide abstract] ABSTRACT: Hyperbranched polyesters (HPE) have a high efficiency to encapsulate bioactive agents, including drugs, genes and proteins, due to their globe-like nanostructure. However, the use of these highly branched polymeric systems for tissue engineering applications has not been broadly investigated. Here, we report synthesis and characterization of photocrosslinkable HPE hydrogels with sustained drug release characteristics for cellular therapies. These HPE can encapsulate hydrophobic drug molecules within the HPE cavities, due to the presence of hydrophobic inner structure that is otherwise difficult to achieve in conventional hydrogels. The functionalization of HPE with photocrosslinkable acrylate moieties renders the formation of hydrogels with highly porous interconnected structure, and mechanically tough network. The compressive modulus of HPE hydrogels was tunable by changing the crosslinking density. The feasibility of using these HPE networks for cellular therapies was investigated by evaluating cell adhesion, spreading and proliferation on hydrogel surface. Highly crosslinked and mechanically stiff HPE hydrogels have higher cell adhesion, spreading, proliferation compared to soft and complaint HPE hydrogels. We also investigated possibility of using HPE hydrogels for cell sheet engineering. Overall, we showed that hydrogels made from HPE could be used for biomedical applications that require control cell adhesion and control release of hydrophobic clues.
[show abstract][hide abstract] ABSTRACT: The objective of this study was to modify zirconium dioxide (ZrO(2)) with photo-cured hyaluronic acid hydrogel (pcHAgel), and to subsequently evaluate the bone regeneration potential of the modified ZrO(2). In the present study, HA grafted onto a ZrO(2) substrate was investigated for its biocompatibility and other properties. We describe the positive influences of ZrO(2) surface-modified with pcHAgel (Zr-3) containing two different loads of growth and differentiation factor-5 (GDF-5) to aid new bone formation as compared to the same amount of BMP-2 (Zr-4-7). We characterized the Zr-3 for their surface morphology and chemical properties. Atomic force microscopy (AFM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) showed that the pcHAgel was successfully grafted onto the ZrO(2) surface. The sustained release of GDF-5 and BMP-2 were observed to occur in the Zr-4-7. In vitro cell tests showed a higher level of MG63 cell proliferation and differentiation on Zr-4-7 than on Zr-3. The Zr-3 is a good biomaterial to deliver osteogenic differentiation factors such as BMP-2 and GDF-5, and GDF-5 can be useful as an effective alternative to aid new bone formation as compared to BMP-2.
[show abstract][hide abstract] ABSTRACT: We engineered functional cardiac patches by seeding neonatal rat cardiomyocytes onto carbon nanotube (CNT) incorporated photocrosslinkable gelatin methacrylate (GelMA) hydrogel. The resulting cardiac constructs showed excellent mechanical integrity and advanced electrophysiological functions. Specifically, myocardial tissues cultured on 50 μm thick CNT-GelMA showed 3 times higher spontaneous synchronous beating rates and 85% lower excitation threshold, compared to those cultured on pristine GelMA hydrogels. Our results indicate that the electrically conductive and nanofibrous networks formed by CNTs within a porous gelatin framework is the key characteristics of CNT-GelMA leading to improved cardiac cell adhesion, organization, and cell-cell coupling. Centimeter-scale patches were released from glass substrates to form 3D biohybrid actuators, which showed controllable linear cyclic contraction/extension, pumping, and swimming actuations. In addition, we demonstrate for the first time that cardiac tissues cultured on CNT-GelMA resist damage by a model cardiac inhibitor as well as a cytotoxic compound. Therefore, incorporation of CNTs into gelatin, and potentially other biomaterials, could be useful in creating multifunctional cardiac scaffolds for both therapeutic purposes and in vitro studies. These hybrid materials could also be used for neuron and other muscle cells to create tissue constructs with improved organization, electroactivity, and mechanical integrity.
[show abstract][hide abstract] ABSTRACT: Chitosan has been used as a scaffolding material in tissue engineering due to its mechanical properties and biocompatibility. With increased appreciation of the effect of micro- and nanoscale environments on cellular behavior, there is increased emphasis on generating microfabricated chitosan structures. Here we employed a microfluidic coaxial flow-focusing system to generate cell adhesive chitosan microtubes of controlled sizes by modifying the flow rates of a chitosan pre-polymer solution and phosphate buffered saline (PBS). The microtubes were extruded from a glass capillary with a 300 μm inner diameter. After ionic crosslinking with sodium tripolyphosphate (TPP), fabricated microtubes had inner and outer diameter ranges of 70-150 μm and 120-185 μm. Computational simulation validated the controlled size of microtubes and cell attachment. To enhance cell adhesiveness on the microtubes, we mixed gelatin with the chitosan pre-polymer solution. During the fabrication of microtubes, fibroblasts suspended in core PBS flow adhered to the inner surface of chitosan-gelatin microtubes. To achieve physiological pH values, we adjusted pH values of chiotsan pre-polymer solution and TPP. In particular, we were able to improve cell viability to 92 % with pH values of 5.8 and 7.4 for chitosan and TPP solution respectively. Cell culturing for three days showed that the addition of the gelatin enhanced cell spreading and proliferation inside the chitosan-gelatin microtubes. The microfluidic fabrication method for ionically crosslinked chitosan microtubes at physiological pH can be compatible with a variety of cells and used as a versatile platform for microengineered tissue engineering.
[show abstract][hide abstract] ABSTRACT: Recently, a wide range of nanotechnologies has been approached for material modification by realizing the fact that the extracellular matrix (ECM) consists of nanoscale components and exhibits nanoscale architectures. Moreover, cell-cell and cell- ECM interactions actively occur on the nanoscale and ultimately play large roles in determining cell fate in tissue engineering. Nanomaterials have provided the potential to preferentially control the behavior and differentiation of cells. The present paper reviews the need for nanotechnology in regenerative medicine and the role of nanotechnology in repairing, restoring, and regenerating damaged body parts, such as blood vessels, lungs, and the heart.
Computational and structural biotechnology journal. 01/2013; 7:e201304005.
[show abstract][hide abstract] ABSTRACT: Recent advances in stem cell research have demonstrated the importance of microenvironmental cues in directing stem cell fate towards specific cell lineages. For instance, the size of the embryoid body (EB) was shown to play a role in stem cell differentiation. Other studies have used cell adhesive RGD peptides to direct stem cell fate towards endothelial cells. In this study, materials and cell-based approaches are combined by using microwell arrays to produce size-controlled EBs and encapsulating the resulting aggregates in high molecular weight PEG-4 arm acrylate with and without conjugated RGD to study their effect on stem cell differentiation in a 3D microenvironment. Increasing EB size is observed along with a decrease in the total number of EBs in pristine PEG hydrogel, regardless of the initial EB size. In correlation with this aggregation, EBs in PEG show enhanced cardiogenic differentiation compared to RGD-PEG hydrogel. Both aggregation and cardiogenic differentiation are significantly reduced when RGD peptides are introduced to the microenvironment, while endothelial cell differentiation is accelerated by 3 to 5 days, depending on the EB size, and doubled over the course of cell culture for both EB sizes. Presented results indicate that RGD sequence has a dominant effect in driving endothelial cell differentiation in size-controlled EBs, while pristine multi-arm, high molecular weight PEG can induce cardiogenic differentiation, possibly through EB aggregation. The photopatternable nature of the hydrogel used in this study enabled patterning of such domains devoid or abundant of cell attachment sequences. Therefore, these hydrogels can potentially be used for spatially patterned embryonic stem cell differentiation, which may be beneficial for tissue engineering and regenerative medicine applications.
[show abstract][hide abstract] ABSTRACT: Only a few engineered tissues-skin, cartilage, bladder-have achieved clinical success, and biomaterials designed to replace more complex organs are still far from commercial availability. This gap exists in part because biomaterials lack a vascular network to transfer the oxygen and nutrients necessary for survival and integration after transplantation. Thus, generation of a functional vasculature is essential to the clinical success of engineered tissue constructs and remains a key challenge for regenerative medicine. In this Perspective, we discuss recent advances in vascularization of biomaterials through the use of biochemical modification, exogenous cells, or microengineering technology.
Science translational medicine 11/2012; 4(160):160ps23. · 10.76 Impact Factor