[Show abstract][Hide abstract] ABSTRACT: Precise control of media delivery to cells in microfluidic systems in a simple and efficient manner is a challenge for a number of cell-based applications. Conventional syringe pumps can deliver culture media into microfluidic devices at precisely controlled flow rates, but they are large and require a power source. On the other hand, passive microflow-generating systems cannot maintain continuous, controllable and long-term delivery of media. We have developed an on-chip microflow control technology that combines flow rate control and passive, long-term delivery of media to microwell tissue culture chambers. Here, passive flow is initiated using siphon effects and a yarn flow resistor is used to regulate the flow rate in the microchannel. Using the yarn flow resistor, the media flow rate into the microfluidic cell culture system is adjustable to a few hundred microliters per hour. To evaluate the effects of controlled flow on microfluidic cell culture properties (feasibility test), we measured the cell alignment and cytoskeletal arrangement of endothelial cells cultured in a microwell array inside the microfluidic channel.
[Show abstract][Hide abstract] ABSTRACT: Engineering functional muscle tissue requires the formation of densely packed, aligned, and mature myotubes. To enhance the formation of aligned myotubes with improved contractibility, we fabricated aligned electrospun gelatin multi-walled carbon nanotubes (MWNTs) hybrid fibers that were used as scaffolds for the growth of myoblasts (C2C12). The MWNTs significantly enhanced myotube formation by improving the mechanical properties of the resulting fibers and upregulated the activation of mechanotransduction related genes. In addition, the fibers enhanced the maturation of the myotubes and the amplitude of the myotube contractions under electrical stimulation (ES). Such hybrid material scaffolds may be useful to direct skeletal muscle cellular organization, improve cellular functionality and tissue formation.
[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: Tissue engineering (TE) is a multidisciplinary research area that combines medicine, biology, and material science. In recent decades, microtechnology and nanotechnology have also been gradually integrated into this field and have become essential components of TE research. Tissues and complex organs in the body depend on a branched blood vessel system. One of the main objectives for TE researchers is to replicate this vessel system and obtain functional vascularized structures within engineered tissues or organs. With the help of new nanotechnology and microtechnology, significant progress has been made. Achievements include the design of nanoscale-level scaffolds with new functionalities, development of integrated and rapid nanotechnology methods for biofabrication of vascular tissues, discovery of new composite materials to direct differentiation of stem and inducible pluripotent stem cells into the vascular phenotype. Although numerous challenges to replicating vascularized tissue for clinical uses remain, the combination of these new advances has yielded new tools for producing functional vascular tissues in the near future.
Journal of Nanoscience and Nanotechnology 01/2014; 14(1):487-500. · 1.34 Impact Factor
[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: Calcium phosphate-reinforced photosensitizer-loaded polymer nanoparticles have been developed for photodynamic therapy. Chlorin e6 (Ce6)-loaded core-shell-corona polymer micelles of poly(ethylene glycol)-b-poly(L-aspartic acid)-b-poly(L-phenylalanine) (PEG-PAsp-PPhe) were employed as template nanoparticles for mineralization with calcium phosphate (CaP). CaP deposition was performed by the electrostatic localization of calcium ions at the anionic PAsp middle shells and the subsequent addition of phosphate anions. CaP-reinforced nanoparticles exhibited enhanced stability. The CaP mineral layer effectively inhibited Ce6 release from the Ce6-loaded mineralized nanoparticles (Ce6-NP-CaP) at physiological pH value. At an acidic endosomal pH value of 5.0, Ce6 release was enhanced, owing to rapid dissolution of the CaP minerals. Upon irradiation of Ce6-NP-CaP-treated MCF-7 breast-tumor cells, the cell viability dramatically decreased with increasing irradiation time. The phototoxicity of Ce6-NP-CaP was much higher than that of free Ce6. Non-invasive optical-imaging results indicated that Ce6-NP-CaP exhibited enhanced tumor specificity compared with free Ce6 and Ce6-loaded non-mineralized polymer nanoparticles (Ce6-NP).
Chemistry - An Asian Journal 09/2013; · 4.57 Impact Factor
[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: 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. 04/2013; 7:e201304005.
[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.