Nanoengineered hydrogels offer the potential to design shear-thinning bioinks for three-dimensional (3D) bioprinting. Here, we have synthesized colloidal bioinks composed of disk-shaped ...two-dimensional (2D) nanosilicates (Laponite) and poly(ethylene glycol) (PEG). The addition of Laponite reinforces the PEG network and increases viscosity, storage modulus, and network stability. PEG-Laponite hydrogels display shear-thinning and self-recovery characteristics due to rapid internal phase rearrangement. As a result, a range of complex patterns can be printed using PEG-Laponite bioinks. The 3D bioprinted structure has similar mechanical properties compared to the as-casted structure. In addition, encapsulated cells within the PEG-Laponite bioink show high viability after bioprinting. Overall, this study introduces a new class of PEG-Laponite colloidal inks for bioprinting and cell delivery.
We report herein on remote control over a reversible phase transition of robust luminescent hybrid hydrogels as enabled by the rational selection and incorporation of photoswitches. Azobenzene units ...functionalized with a guanidinium group were utilized as the photoswitches and incorporated through a host–guest inclusion method involving α‐cyclodextrins functionalized with 2,6‐pyridinedicarboxylic acid (PDA) groups. While the guanidinium functional groups bind to the negatively charged Laponite matrix surface to connect organic and inorganic components, the PDA groups enable simultaneous coordination with different lanthanide metal ions, thus rendering the hydrogel broadly luminescent. Owing to its conformation‐dependent binding behavior with α‐cyclodextrin, the isomerization of azobenzene induced association or dissociation of the inclusion complexes and thus lead to a reversible photocontrolled sol↔gel phase transition of the luminescent hybrid hydrogels.
Remote control over a reversible sol↔gel phase transition of a robust luminescent hybrid hydrogel (see picture) was enabled by the incorporation of photoswitchable host–guest inclusion compounds into the hydrogel system. Guanidinium groups on the azobenzene guest units bind to a Laponite matrix, and pyridinedicarboxylic acid groups on the α‐cyclodextrin host units coordinate to lanthanide ions, thus rendering the hydrogel broadly luminescent.
Ambient solution and amorphous state room temperature phosphorescence (RTP) from purely organic chromophores is rarely achieved. Remarkable stabilization of triplet excitons is realized to obtain ...deep red phosphorescence in water and in amorphous film state under ambient conditions by a unique supramolecular hybrid assembly between inorganic laponite clay and heavy atom core substituted naphthalene diimide (NDI) phosphor. Structural rigidity and oxygen tolerance of the inorganic template along with controlled molecular organization via supramolecular scaffolding are envisaged to alleviate the unprecedented aqueous phase phosphorescence.
Aqueous phosphorescence: An unprecedented organic‐inorganic hybrid co‐assembly approach is proposed to obtain aqueous state as well as amorphous red‐emitting room temperature phosphorescence. Heavy‐atom effect in the NDI derivative along with its J‐aggregation enhance the intersystem crossing efficiency whereas rigid and oxygen tolerant laponite templates stabilize the triplets.
The engineering of bioadhesives to bind and conform to the complex contour of tissue surfaces remains a challenge. We have developed a novel moldable nanocomposite hydrogel by combining ...dopamine‐modified poly(ethylene glycol) and the nanosilicate Laponite, without the use of cytotoxic oxidants. The hydrogel transitioned from a reversibly cross‐linked network formed by dopamine–Laponite interfacial interactions to a covalently cross‐linked network through the slow autoxidation and cross‐linking of catechol moieties. Initially, the hydrogel could be remolded to different shapes, could recover from large strain deformation, and could be injected through a syringe to adhere to the convex contour of a tissue surface. With time, the hydrogel solidified to adopt the new shape and sealed defects on the tissue. This fit‐to‐shape sealant has potential in sealing tissues with non‐flat geometries, such as a sutured anastomosis.
Hugs tight, holds tight: A moldable nanocomposite hydrogel was developed by combining a mussel‐inspired polymer and a nanosilicate. The hydrogel is remoldable, injectable, and able to adhere to tissue with a convex contour (see picture).
Investigating microstructure of suspensions with particles having anisotropic shape that share complex interactions is a challenging task leading to competing claims. This work investigates phase ...behavior of one such system: aqueous Laponite suspension, which is highly contested in the literature, using rheological and microscopic tools. Remarkably, we observe that over a broad range of Laponite (1.4 to 4 wt %) and salt concentrations (0 to 7 mM), the system overwhelmingly demonstrates all the rheological characteristics of the sol–gel transition leading to a percolated network. Analysis of the rheological response leads to fractal dimension that primarily depends on the Laponite concentration. We also obtain the activation energy for gelation, which is observed to decrease with increase in Laponite as well as salt concentration. Significantly, the cryo-TEM images of the postgel state clearly show the presence of a percolated network formed by interparticle bonds. The present work therefore conclusively establishes the system to be in an attractive gel state resolving a long-standing debate in the literature.
Three-dimensional printing of cell-laden hydrogels has evolved as a promising approach on the route to patient-specific or complex tissue-engineered constructs. However, it is still challenging to ...print structures with both, high shape fidelity and cell vitality. Herein, we used a synthetic nanosilicate clay, called Laponite, to build up scaffolds utilising the extrusion-based method 3D plotting. By blending with alginate and methylcellulose, a bioink was developed which allowed easy extrusion, achieving scaffolds with high printing fidelity. Following extrusion, approximately 70%-75% of printed immortalised human mesenchymal stem cells survived and cell viability was maintained over 21 days within the plotted constructs. Mechanical properties of scaffolds comprised of the composite bioink decreased over time when stored under cell culture conditions. Nevertheless, shape of the plotted constructs was preserved even over longer cultivation periods. Laponite is known for its favourable drug delivery properties. Two model proteins, bovine serum albumin and vascular endothelial growth factor were loaded into the bioink. We demonstrate that the release of both growth factors significantly changed to a more sustained profile by inclusion of Laponite in comparison to an alginate-methylcellulose blend in the absence of Laponite. In summary, addition of a synthetic clay, Laponite, improved printability, increased shape fidelity and was beneficial for controlled release of biologically active agents such as growth factors.
The capacity to simulate the construction of natural extracellular matrix is an effective approach to guided bone regeneration (GBR). Here, novel nanocomposite fibrous membranes of silk fibroin ...(SF)-Laponite® (LAP) were developed through electrospinning approach. The membranes were considered according to the physical and mechanical characteristics, degradation rate, in vitro bioactivity evaluation and biological properties. Results showed that the optimized nanocomposite fibrous membrane with meaningfully enhanced tensile strength, toughness and elastic modules was obtained via incorporation of 5 wt% LAP nanoplates into SF membrane. LAP nanoplates incorporation in the SF membrane promoted its hydrophilicity, swelling ratio, and degradation rate, while induced apatite mineralization in simulated body fluid. Moreover, nanocomposite fibrous membranes revealed meaningfully superior cellular responses compared to SF membrane. Consequently, nanocomposite SF-LAP fibrous membranes anticipated to being appealing for GBR applications.
•Silk-Laponite(LAP) fibrous membranes were develop for bone tissue engineering.•Incorporation of LAP in Silk fibers noticeably enhanced mechanical properties.•LAP meaningfully promoted bioactivity and degradation ability of silk.•LAP considerably improved the attachment and proliferation of stem cells.
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.
A multicomponent hydrogel platform that combines oxidative coupling with supramolecular co‐assembly to enable the tunability of physical, mechanical, and biological properties desirable in bone tissue regeneration is reported. The strategy permits the integration of the osteogenic properties of Laponite (Lap), the nanofibrous structure of peptide amphiphiles, the pro‐angiogenic properties of glycyl‐histidyl‐lysine (GHK) peptide, and the instant gelation of tyramine‐modified hyaluronic acid (HA‐Tyr).
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The objective of this study was to develop an injectable and biocompatible hydrogel that can deliver a cocktail of therapeutic biomolecules (secretome) secreted by human ...adipose-derived stem cells (hASCs) to the peri-infarct myocardium. Gelatin and Laponite® were combined to formulate a shear-thinning, nanocomposite hydrogel (nSi Gel) as an injectable carrier of secretome (nSi Gel+). The growth factor composition and the pro-angiogenic activity of the secretome were tested in vitro by evaluating the proliferation, migration and tube formation of human umbilical endothelial cells. The therapeutic efficacy of the nSi Gel + system was then investigated in vivo in rats by intramyocardial injection into the peri-infarct region. Subsequently, the inflammatory response, angiogenesis, scar formation, and heart function were assessed. Biocompatibility of the developed nSi Gel was confirmed by quantitative PCR and immunohistochemical tests which showed no significant differences in the level of inflammatory genes, microRNAs, and cell marker expression compared to the untreated control group. In addition, the only group that showed a significant increase in capillary density, reduction in scar area and improved cardiac function was treated with the nSi Gel+. Our in vitro and in vivo findings demonstrate the potential of this new secretome-loaded hydrogel as an alternative strategy to treat myocardial infarction.
Stem cell based-therapies represent a possible solution to repair damaged myocardial tissue by promoting cardioprotection, angiogenesis, and reduced fibrosis. However, recent evidence indicates that most of the positive outcomes are likely due to the release of paracrine factors (cytokines, growth factors, and exosomes) from the cells and not because of the local engraftment of stem cells. This cocktail of essential growth factors and paracrine signals is known as secretome can be isolated in vitro, and the biomolecule composition can be controlled by varying stem-cell culture conditions. Here, we propose a straightforward strategy to deliver secretome produced from hASCs by using a nanocomposite injectable hydrogel made of gelatin and Laponite®. The designed secretome-loaded hydrogel represents a promising alternative to traditional stem cell therapy for the treatment of acute myocardial infarction.
4D printing has emerged as an important technique for fabricating 3D objects from programmable materials capable of time‐dependent reshaping. In the present investigation, novel 4D thermoinks ...composed of laponite (LAP), an interpenetrating network of poly(N‐isopropylacrylamide) (PNIPAAm), and alginate (ALG) are developed for direct printing of shape‐morphing structures. This approach consists of the design and fabrication of 3D honeycomb‐patterned hydrogel discs self‐rolling into tubular constructs under the stimulus of temperature. The shape morphing behavior of hydrogels is due to shear‐induced anisotropy generated via 3D printing. The compositionally tunable hydrogel discs can be programmed to exhibit different actuation behaviors at different temperatures. Upon immersion in 12 °C water, singly crosslinked sheets roll up into a tubular construct. When transferred to 42 °C water, the tubes first rapidly unfold and then slightly curve up in the opposite direction. Through a dual photocrosslinking of PNIPAAm, it is possible to inverse temperature‐dependent shape morphing and induce self‐folding at higher and unrolling at lower temperatures. The extensive self‐assembling motion is essential to developing thermal actuators with broad applications in, e.g., soft robotics and active implantology, whereas controllable self‐rolling of planar hydrogels is of the highest interest to biomedical engineering as it allows for effective fabrication of hollow tubes.
This study presents a 4D‐printed shape‐morphing patterned planar structure composed of a poly(N‐isopropylacrylamide) (PNIPAAm)‐based hydrogel that is designed to self‐fold into tubes in response to temperature. Novel 4D thermoinks composed of laponite nanoclay, an interpenetrating network of PNIPAAm, and alginate are developed for direct 4D printing of shape‐morphing structures.
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