Multicomponent Hydrogels for the Formation of Vascularized Bone-like Constructs In Vitro.

The native extracellular matrix (ECM) is a complex gel-like system with a broad range of structural features and biomolecular signals. Hydrogel platforms that can recapitulate the complexity and signaling properties of this ECM would have enormous impact in fields ranging from tissue engineering to drug discovery. Here, we report on the design, synthesis, and proof-of-concept validation of a microporous and nanofibrous hydrogel exhibiting multiple bioactive epitopes designed to recreate key features of the bone ECM. The material platform integrates self-assembly with orthogonal enzymatic cross-linking to create a supramolecular environment comprising hyaluronic acid modified with tyramine (HA-Tyr) and peptides amphiphiles (PAs) designed to promote cell adhesion (RGDS-PA), osteogenesis (Osteo-PA), and angiogenesis (Angio-PA). Through individual and co-cultures of human adipose derived mesenchymal stem cells (hAMSCs) and human umbilical vascular endothelial cells (HUVECs), we confirmed the capacity of the HA-Tyr/RGDS-PA/Osteo-PA/Angio-PA hydrogel to promote cell adhesion as well as osteogenic and angiogenic differentiation in both 2D and 3D setups. Furthermore, using immunofluorescent staining and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), we demonstrated co-differentiation and organization of hAMSCs and HUVECs into 3D aggregates resembling vascularized bone-like constructs

Supramolecular Self-Assembly to Control Structural and Biological Properties of Multicomponent Hydrogels

Self-assembled nanofibers are ubiquitous in nature and serve as inspiration for the design of supramolecular hydrogels. A multicomponent approach offers the possibility of enhancing tunability and functionality of this class of materials. We report on the synergistic multicomponent self-assembly involving a peptide amphiphile (PA) and a 1,3:2,4-dibenzylidene-D-sorbitol (DBS) gelator to generate hydrogels with tunable nanoscale morphology, improved stiffness, enhanced self-healing, and stability to enzymatic degradation. Using induced circular dichroism of Thioflavin T (ThT), electron microscopy, small-angle neutron scattering (SANS), and molecular dynamics approaches we confirm that the PA undergoes self-sorting while the DBS-gelator acts as an additive modifier for the PA nanofibers. The supramolecular interactions between the PA and DBS gelators result in improved bulk properties and cytocompatibility of the two-component hydrogels as compared to the single component systems. The tunable mechanical properties, self-healing ability, resistance to proteolysis, and biocompatibility of the hydrogels suggest future opportunities for the hydrogels as scaffolds for tissue engineering and drug delivery vehicles

Covalent co-assembly between resilin-like polypeptide and peptide amphiphile into hydrogels with controlled nanostructure and improved mechanical properties

Covalent co-assembly holds great promise for the fabrication of hydrogels with controllable nanostructure, versatile chemical composition, and enhanced mechanical properties given its relative simplicity, high efficiency, and bond stability. This report describes our approach to designing functional multicomponent hydrogels based on photo-induced chemical interactions between an acrylamide-functionalized resilin-like polypeptide (RLP) and a peptide amphiphile (PA). Circular dichroism (CD) spectroscopy, electron microscopy, and amplitude sweep rheology were used to demonstrate that the co-assembled hydrogel systems acquired distinct structural conformations, tunable nanostructures, and enhanced elasticity in a PA concentration-dependent manner. We envisage the use of these materials in numerous biomedical applications such as controlled drug release systems, microfluidic devices, and scaffolds for tissue engineering

Growth‐Factor Free Multicomponent Nanocomposite Hydrogels That Stimulate Bone Formation

Synthetic osteo‐promoting materials that are able to stimulate and accelerate bone formation without the addition of exogenous cells or growth factors represent a major opportunity for an aging world population. A co‐assembling system that integrates hyaluronic acid tyramine (HA‐Tyr), bioactive peptide amphiphiles (GHK‐Cu2+), and Laponite (Lap) to engineer hydrogels with physical, mechanical, and biomolecular signals that can be tuned to enhance bone regeneration is reported. The central design element of the multicomponent hydrogels is the integration of self‐assembly and enzyme‐mediated oxidative coupling to optimize structure and mechanical properties in combination with the incorporation of an osteo‐ and angio‐promoting segments to facilitate signaling. Spectroscopic techniques are used to confirm the interplay of orthogonal covalent and supramolecular interactions in multicomponent hydrogel formation. Furthermore, physico‐mechanical characterizations reveal that the multicomponent hydrogels exhibit improved compressive strength, stress relaxation profile, low swelling ratio, and retarded enzymatic degradation compared to the single component hydrogels. Applicability is validated in vitro using human mesenchymal stem cells and human umbilical vein endothelial cells, and in vivo using a rabbit maxillary sinus floor reconstruction model. Animals treated with the HA‐Tyr‐HA‐Tyr‐GHK‐Cu2+ hydrogels exhibit significantly enhanced bone formation relative to controls including the commercially available Bio‐Oss

De Novo Design of Functional Co-Assembling Organic-Inorganic Hydrogels for Hierarchical Mineralization and Neovascularization

Synthetic nanostructured materials incorporating both organic and inorganic components offer a unique, powerful and versatile class of materials for widespread applications due to the distinct, yet complementary, nature of the intrinsic properties of the different constituents. We report a supramolecular system based on synthetic nanoclay (Laponite™, Lap) and peptide amphiphiles (PAs, PAH3) rationally designed to co-assemble into nanostructured hydrogels with high structural integrity and a spectrum of bioactivities. Spectroscopic and scattering techniques and molecular dynamic simulation approaches were harnessedto confirm that PAH3 nanofibers electrostatically adsorbed and conformed to the surface of Lapnanodisks. Electron and atomic force microscopies also confirmed an increase in diameter and surface areaof PAH3nanofibers after co-assembly with Lap. Dynamic oscillatory rheology revealed that the co-assembled PAH3-Laphydrogels displayed high stiffness and robust self-healing behaviour while gas adsorption analysis confirmed a hierarchical and heterogeneous porosity. Furthermore, this distinctive structure within the three-dimensional matrix(3D) provided spatial confinement for the nucleation and hierarchical organization of high-aspect ratio hydroxyapatite nanorods into well-defined spherical clusters within the 3Dmatrix. Applicability of the organic-inorganic PAH3-Laphydrogels was assessed in vitrousing human bone marrow-derived stromal cells(hBMSCs) and ex vivousing a chick chorioallantoic membrane (CAM) assay. The results demonstrated that the organic-inorganic PAH3-Laphydrogels promote human skeletal cell proliferation and, upon mineralization, integrate with the CAM, are infiltrated by blood vessels, stimulate extracellular matrix production, and facilitate extensive mineral deposition relative to the controls

In vivo comparison of jellyfish and bovine collagen sponges as prototype medical devices

Jellyfish have emerged as a source of next generation collagen that is an attractive alternative to existing sources, such as bovine and porcine, due to a plentiful supply and providing a safer source through lack of bovine spongiform encephalopathy (BSE) transmission risk and potential viral vectors, both of which could be transmitted to humans. Here we compare collagen implantable sponges derived for the first time from the Rhizostoma pulmo jellyfish. A further novelty for the research was that there was a comparison for sponges that were either uncrosslinked or crosslinked using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride (EDC), and an assessment on how this affected resorption, as well as their biocompatibility compared to bovine type I collagen sponges. The scaffolds were prepared and examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) and scanning electron microscopy (SEM). The samples were implanted in adult male Wistar rats for in vivo experimentation. Both crosslinked and uncrosslinked jellyfish collagen sponges showed a significant reduction in histopathology scores over the course of the study, whereas the bovine collagen sponge scores were not significantly reduced. Both jellyfish collagen sponges and the bovine sponge were tolerated well by the hosts, and a recovery was visible in all samples, suggesting that R. pulmo jellyfish‐derived collagen could offer compelling biocompatibility with wound healing applications. We also demonstrate that noncrosslinked samples could be safer with better resorption times than crosslinked samples

A thermosensitive electromechanical model for detecting biological particles

Miniature electromechanical systems form a class of bioMEMS that can provide appropriate sensitivity. In this research, a thermo-electro-mechanical model is presented to detect biological particles in the microscale. Identification in the model is based on analyzing pull-in instability parameters and frequency shifts. Here, governing equations are derived via the extended Hamilton’s principle. The coupled effects of system parameters such as surface layer energy, electric field correction, and material properties are incorporated in this thermosensitive model. Afterward, the accuracy of the present model and obtained results are validated with experimental, analytical, and numerical data for several cases. Performing a parametric study reveals that mechanical properties of biosensors can significantly affect the detection sensitivity of actuated ultra-small detectors and should be taken into account. Furthermore, it is shown that the number or dimension of deposited particles on the sensing zone can be estimated by investigating the changes in the threshold voltage, electrode deflection, and frequency shifts. The present analysis is likely to provide pertinent guidelines to design thermal switches and miniature detectors with the desired performance. The developed biosensor is more appropriate to detect and characterize viruses in samples with different temperatures

Development and characterization of skin substitutes from electrospun polycaprolactone/silk fibroin

Tissue-engineered skin substitutes have great potential to treat chronic wounds and high-degree burns. Existing solutions, such as Integra Dermal Template, are extensively used for skin defects. However, these templates are still lacking in terms of recreating the functionality of the native tissue and providing scarless healing. In this study, polycaprolactone/silk fibroin (PCL/SF)-based nanofibers with varying blends were fabricated and characterized to develop a novel skin substitute. Morphological analysis showed that the nanofiber distribution of each sample was homogenous without showing any beads. In terms of mechanical properties, all the samples other than SF showed sufficient mechanical strength. It was observed that adding a specific amount of SF into the PCL nanofiber improves the tensile strength of the samples due to the introduction of intermolecular interactions from the functional groups of SF. In addition, incorporating SF into PCL improved Young’s modulus of the PCL nanofibers since SF provides stiffness and structural integrity to the overall structure. Water contact angle analysis was performed as the hydrophilicity of a biomaterial is a significant factor in cell functionality. Each sample had a contact angle between 33° and 48°, indicating the adequate hydrophilicity of nanofibers for advanced cell proliferation other than PCL. Cell proliferation and viability studies were conducted with the seeding of primary human keratinocytes on the samples. It was examined that scaffolds containing blends of PCL and SF resulted in higher cell proliferation and viability after 7 days compared to pure PCL and SF nanofibers