Three-dimensional Hydrogel Constructs Research Articles

A Novel In Vitro and In Silico System for Analyzing Complex Mechanobiological Behavior of Chondrocytes in Three-Dimensional Hydrogel Constructs.

Physiological loading is essential for the maintenance of articular cartilage through the regulation of tissue remodeling. To correctly understand the behavior of chondrocytes in their native environment, cell stimulating devices and bioreactors have been developed to examine the effect of mechanical stimuli on chondrocytes. This study describes the design and validation of a novel system for analyzing chondrocyte deformation patterns. This involves an in vitro mechanical device for a controlled application of multi-axial-loading regimes to chondrocyte-seeded agarose constructs and in silico models for analyzing chondrocyte deformation patterns. The computer-controlled device precisely applies compressive, tensile, and shear strains to hydrogel constructs using a customizable macro-based program. The synchronization of the displacements is shown to be accurate with a 1.2% error and is highly reproducible. The device design allows housing for up to eight novel designed free-swelling three-dimensional hydrogel constructs. Constructs include mesh ends and are optimized to withstand the application of up to 7% mechanical tensile and 15% shear strains. Constructs were characterized through mapping the strain within as mechanical load was applied and was validated using light microscopy methods, chondrocyte viability using live/dead imaging, and cell deformation strains. Images were then analyzed to determine the complex deformation strain patterns of chondrocytes under a range of dynamic mechanical stimulations. This is one of the first systems that have characterized construct strains to cellular strains. The features in this device make the system ideally suited for a systematic approach for the investigation of the response of chondrocytes to a complex physiologically relevant deformation profile.

3D printed stimuli-responsive magnetic nanoparticle embedded alginate-methylcellulose hydrogel actuators

Magnetic hydrogels have a myriad of promising applications including soft electronics, flexible robotics, biomedical devices, and wastewater treatment. However, their potential is limited by conventional fabrication methods which impede creating convoluted geometries. 3D printing may replace traditional fabrication techniques as it has an ability to fabricate complex shapes using a wide variety of materials. A new 3D printing ink, a bionanocomposite based on alginate, methylcellulose and magnetic nanoparticles (MNPs) was used to print pre-designed high-quality 3D structures. Three-dimensional hydrogel constructs had good mechanical stability and exhibited responsiveness to an applied magnetic field. Inclusion of the MNPs within the hydrogel and its precursor (ink) influenced their rheological properties - and mechanical stability. MNPs were found to play dual roles: (1) as a nanofiller that interacts with polymer backbone and alters its physicochemical properties, and (2) as a function provider that renders a bionanocomposite magnetic. The magnetic ink allows for the fabrication of multi-material structures such as hydrogels with a magnetic nanoparticle gradient. 3D-printed objects can be remotely actuated via magnetic fields.

Hydrogels for neuroprotection and functional rewiring: a new era for brain engineering.

The neurological devastation of neurodegenerative and cerebrovascular diseases reinforces our perseverance to find advanced treatments to deal with these fatal pathologies. High-performance preclinical results have failed at clinical level, as it has been the case for a wide variety of neuroprotective agents and cell-based therapies employed to treat high prevalent brain pathologies such as stroke, Alzheimer’s and Parkinson’s diseases. An unquestionable reality is the current absence of effective therapies to neuroprotect the brain, to arrest neurodegeneration and rewire the impaired brain circuits. Part of the problem might arise from the lack of adequate in vitro and in vivo models and that most of the underlying pathophysiological mechanisms are not yet clarified. Another contributing factor is the lack of efficient systems to sustain drug release at therapeutic concentrations and enhance the survival and function of grafted cells in transplantation procedures. For medical applications the use of biomaterials of different compositions and formats has experienced a boom in the last decades. Although the greater complexity of central nervous system has probably conditioned their extensive use with respect to other organs, the number of biomaterials-based applications to treat the injured brain or in the process of being damaged has grown exponentially. Hydrogel-based biomaterials have constituted a turning point in the treatment of cerebral disorders using a new form of advanced therapy. Hydrogels show mechanical properties in the range of cerebral tissue resulting very suitable for local implantation of drugs and cells. It is also possible to fabricate three-dimensional hydrogel constructs with adaptable mesh size to facilitate axonal guidance and elongation. Along this article, we review the current trends in this area highlighting the positive impact of hydrogel-based biomaterials over the exhaustive control of drug delivery, cell engraftment and axonal reinnervation in brain pathologies.

Chondrogenesis of human bone marrow mesenchymal stem cells in 3-dimensional, photocrosslinked hydrogel constructs: Effect of cell seeding density and material stiffness.

Engineering cartilage with physiologically relevant mechanical properties for point-of-care applications represents a major challenge in orthopedics, given the generally low mechanical strengths of traditional hydrogels used in cartilage tissue engineering. In this study, we characterized a new material that possesses high mechanical strength similar to native cartilage, and determined the optimal cell density and scaffold stiffness to achieve the most efficient chondrogenic response from seeded human bone marrow stem cells. Results show robust chondrogenesis and strongly suggest the potential of this material to be applied clinically for point-of-care repair of cartilage defects.

Modulating the phenotype of host macrophages to enhance osteogenesis in MSC-laden hydrogels: Design of a glucomannan coating material.

The biomaterials-host interaction is a dynamic process in which macrophages play a vital role of regulation. Depending on the biochemical signals they sense, these highly plastic cells can mediate the immune response against the implanted scaffolds and/or exert regenerative potency to varying extent. Designing appropriate 'exterior signals' for scaffolds may exploit the power of endogenous macrophages to aid the regeneration of engineered tissues. To realise this goal, this study devised an injectable, instantaneously-solidifying coating material (acBSP) based on a unique, macrophage-affinitive glucomannan polysaccharide. Coating of three-dimensional hydrogel constructs with acBSP was rapid, neat and complete, requiring neither chemical reactions nor harsh conditions. Comprehensive invitro analyses indicated that acBSP efficiently facilitated the adhesion and activation of macrophages and notably induced the macrophages to express pro-osteogenic/-angiogenic genes. Further invivo assessment of acBSP-coated, mesenchymal stem cells-laden hydrogels in a murine dorsal subcutaneous pocket model demonstrated efficient macrophage activation, desirable scaffold-tissue integration and improved osteogenic differentiation in the delivered cells. In summary, by activating macrophages into a pro-osteogenic phenotype, the acBSP coating has demonstrated its competency as an innovative, open and efficacious platform to harness the power of host immunity for enhancing the regenerative performance of engineered tissue constructs.

Patterned and functionalized nanofiber scaffolds in three-dimensional hydrogel constructs enhance neurite outgrowth and directional control

Objective. Neural tissue engineering holds incredible potential to restore functional capabilities to damaged neural tissue. It was hypothesized that patterned and functionalized nanofiber scaffolds could control neurite direction and enhance neurite outgrowth. Approach. A method of creating aligned electrospun nanofibers was implemented and fiber characteristics were analyzed using environmental scanning electron microscopy. Nanofibers were composed of polycaprolactone (PCL) polymer, PCL mixed with gelatin, or PCL with a laminin coating. Three-dimensional hydrogels were then integrated with embedded aligned nanofibers to support neuronal cell cultures. Microscopic images were captured at high-resolution in single and multi-focal planes with eGFP-expressing neuronal SH-SY5Y cells in a fluorescent channel and nanofiber scaffolding in another channel. Neuronal morphology and neurite tracking of nanofibers were then analyzed in detail. Main results. Aligned nanofibers were shown to enable significant control over the direction of neurite outgrowth in both two-dimensional (2D) and three-dimensional (3D) neuronal cultures. Laminin-functionalized nanofibers in 3D hyaluronic acid (HA) hydrogels enabled significant alignment of neurites with nanofibers, enabled significant neurite tracking of nanofibers, and significantly increased the distance over which neurites could extend. Specifically, the average length of neurites per cell in 3D HA constructs with laminin-functionalized nanofibers increased by 66% compared to the same laminin fibers on 2D laminin surfaces, increased by 59% compared to 2D laminin-coated surface without fibers, and increased by 1052% compared to HA constructs without fibers. Laminin functionalization of fibers also doubled average neurite length over plain PCL fibers in the same 3D HA constructs. In addition, neurites also demonstrated tracking directly along the fibers, with 66% of neurite lengths directly tracking laminin-coated fibers in 3D HA constructs, which was a 65% relative increase in neurite tracking compared to plain PCL fibers in the same 3D HA constructs and a 213% relative increase over laminin-coated fibers on 2D laminin-coated surfaces. Significance. This work demonstrates the ability to create unique 3D neural tissue constructs using a combined system of hydrogel and nanofiber scaffolding. Importantly, patterned and biofunctionalized nanofiber scaffolds that can control direction and increase length of neurite outgrowth in three-dimensions hold much potential for neural tissue engineering. This approach offers advancements in the development of implantable neural tissue constructs that enable control of neural development and reproduction of neuroanatomical pathways, with the ultimate goal being the achievement of functional neural regeneration.

Three-dimensional hydrogel constructs for exposing cells to nanoparticles

In evaluating nanoparticle risks to human health, there is often a disconnect between results obtained from in vitro toxicology studies and those from in vivo activity, prompting the need for improved methods to rapidly assess the hazards of engineered nanomaterials. In vitro studies of nanoparticle toxicology often rely on high doses and short exposure periods due to the difficulty of maintaining monolayer cell cultures over extended time periods as well as the difficulty of maintaining nanoparticle dispersions within the culture environment. In this work, tissue-engineered constructs are investigated as a platform for providing doses of nanoparticles over different exposure periods to cells within a three-dimensional environment that can be tuned to mimic in vivo conditions. Uptake of quantum dots (QDs) by model neural cells was first investigated in a high-dose exposure scenario, resulting in a strong concentration-dependent uptake of carboxyl-functionalised QDs. Poly(ethylene glycol) hydrogel scaffolds with varying mesh sizes were then investigated for their ability to support cell survival and proliferation. Cells were co-encapsulated with carboxyl-functionalised poly(ethylene glycol)-coated QDs at a lower dose than is typical for monolayer cultures. Although the QDs leach from the hydrogel within 24 h, they are also incorporated by cells within the scaffold, enabling the use of these constructs in future studies of cell behaviour and function.