Sandcastle worms have developed protein‐based adhesives, which they use to construct protective tubes from sand grains and shell bits. A key element in the adhesive delivery is the formation of a ...fluidic complex coacervate phase. After delivery, the adhesive transforms into a solid upon an external trigger. In this work, a fully synthetic in situ setting adhesive based on complex coacervation is reported by mimicking the main features of the sandcastle worm's glue. The adhesive consists of oppositely charged polyelectrolytes grafted with thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) chains and starts out as a fluid complex coacervate that can be injected at room temperature. Upon increasing the temperature above the lower critical solution temperature of PNIPAM, the complex coacervate transitions into a nonflowing hydrogel while preserving its volume—the water content in the material stays constant. The adhesive functions in the presence of water and bonds to different surfaces regardless of their charge. This type of adhesive avoids many of the problems of current underwater adhesives and may be useful to bond biological tissues.
A fully synthetic in situ setting adhesive based on complex coacervation is reported by mimicking the main features of the sandcastle worm's glue. The adhesive consists of oppositely charged polyelectrolytes grafted with thermoresponsive poly(N‐isopropylacrylamide) chains. The adhesive starts out as an injectable fluid at room temperature. Upon increasing the temperature, the complex coacervate transitions into a nonflowing hydrogel which bonds to different surfaces.
Many marine organisms have developed adhesives that are able to bond under water, overcoming the challenges associated with wet adhesion. A key element in the processing of several natural underwater ...glues is complex coacervation, a liquid–liquid phase separation driven by complexation of oppositely charged macromolecules. Inspired by these examples, the development of a fully synthetic complex coacervate‐based adhesive is reported with an in situ setting mechanism, which can be triggered by a change in temperature and/or a change in ionic strength. The adhesive consists of a matrix of oppositely charged polyelectrolytes that are modified with thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) grafts. The adhesive, which initially starts out as a fluid complex coacervate with limited adhesion at room temperature and high ionic strength, transitions into a viscoelastic solid upon an increase in temperature and/or a decrease in the salt concentration of the environment. Consequently, the thermoresponsive chains self‐associate into hydrophobic domains and/or the polyelectrolyte matrix contracts, without inducing any macroscopic shrinking. The presence of PNIPAM favors energy dissipation by softening the material and by allowing crack blunting. The high work of adhesion, the gelation kinetics, and the easy tunability of the system make it a potential candidate for soft tissue adhesion in physiological environments.
A complex coacervate‐based injectable adhesive, whose setting is exclusively triggered by a change in the environmental conditions (namely an increase in temperature and/or a decrease in ionic strength), is reported. High adhesive properties are measured in completely submerged conditions resembling a physiological environment, showing that the material is a potential candidate for soft tissue repair purposes.
We investigate the macroscopic adhesion energy (W a) in pure water between a positively charged hydrogel of varying cross-link densities made from (methacryloyloxyethyl)trimethylammonium chloride ...and acrylamide poly(MAETAC-co-AAm) and a negatively charged and cross-linked poly(acrylic acid) (PAA) thin film gel grafted on a silicon wafer. Adhesion tests were carried out on a custom-built probe-tack setup fully immersed in pure water. The interfacial charge density on the PAA hydrogel thin film was estimated from streaming potential measurements and the molecular architecture of the thick hydrogel was obtained from mechanical testing. For a fixed interfacial charge density, W a increased weakly with contact time (in stark contrast with the case where adhesion is due to H-bonds) but strongly with debonding rate. For a given gel, the work of adhesion increased linearly with the interfacial charge density of the thin PAA film, whereas at constant interfacial charge density, W a was found to decrease with the modulus of the gel. The results were analyzed with a simple kinetic bond model proposed by Chaudhury for weak adhesion of elastomers. Using realistic values of the spring constant of the polymer chain and of the characteristic time of bond dissociation, we demonstrate that the work of adhesion can be understood by a combination of a strain rate-dependent bond breaking kinetics and a pH-dependent areal density of electrostatic interactions.
In this work, we report the systematic investigation of a multiresponsive complex coacervate-based underwater adhesive, obtained by combining polyelectrolyte domains and thermoresponsive poly(
...-isopropylacrylamide) (PNIPAM) units. This material exhibits a transition from liquid to solid but, differently from most reactive glues, is completely held together by non-covalent interactions, i.e., electrostatic and hydrophobic. Because the solidification results in a kinetically trapped morphology, the final mechanical properties strongly depend on the preparation conditions and on the surrounding environment. A systematic study is performed to assess the effect of ionic strength and of PNIPAM content on the thermal, rheological and adhesive properties. This study enables the optimization of polymer composition and environmental conditions for this underwater adhesive system. The best performance with a work of adhesion of 6.5 J/m
was found for the complex coacervates prepared at high ionic strength (0.75 M NaCl) and at an optimal PNIPAM content around 30% mol/mol. The high ionic strength enables injectability, while the hydrated PNIPAM domains provide additional dissipation, without softening the material so much that it becomes too weak to resist detaching stress.
Soft underwater adhesives that can function in physiological environments are in high demand for biomedical applications. This study establishes a clear link between the composition and mechanical ...properties of complex coacervates from poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and poly(N,N-(dimethylamino) propylmethacrylamide) (PMADAP) with degrees of polymerization (DP) close to 100. Choosing such low DP offers several advantages including low water contents corresponding to strong mechanical properties while remaining in the unentangled regime to allow injectability at high salt concentrations. Most importantly, this strategy favors the occurrence of the salt-induced sol–gel transition near physiological concentrations, where these materials form sticky hydrogels because of their viscoelastic dissipative nature. The fluidlike coacervate prepared at 0.75 M NaCl behaves as a soft adhesive when injected in physiological conditions. This adhesive satisfies a nontrivial trade-off between injectability and final mechanical properties. Alternatively, the gel-like coacervate prepared at 0.1 M NaCl offers an instant-stick solution in physiological conditions with a remarkable underwater adhesion energy reaching 65 J m–2 at 2 s−1 without the need for a trigger or any form of postreinforcement. These coacervates mimic the behavior of soft adhesives in air and may be useful as biomedical adhesives.
Most commercially available soft tissue glues offer poor performance in the human body. We have developed an injectable adhesive whose setting mechanism is activated by a change in environmental ...factors, i.e., temperature and/or ionic strength. The material and setting process are inspired by the adhesive processing mechanism observed in natural maritime glues. Complex coacervation, a liquid–liquid phase separation between oppositely charged polyelectrolytes, is thought to play an important role in the processing. Complex coacervates are characterized by a high water content, which inevitably weakens the glue. Here, we aim to increase the adhesive performance by systematically tuning the water content. Among the several strategies here explored, the most effective one is the mechanical removal of water using an extruder, resulting in an increase of work of adhesion by 1 order of magnitude compared to the original formulation.
Synthetic vascular access for hemodialysis exhibits biological and mechanical material properties mismatch with the native vessels. These limitations prevent infiltration of endothelial cells and ...decrease grafts long-term patency, particularly in small diameter vessels. We aimed to design a curved structural reinforced small intestinal submucosa (SIS) vascular graft for hemodialysis access and to evaluate in a porcine animal model graft patency by Doppler ultrasonography, tissue remodeling by histology, and vascular wall Young's modulus after implantation by biaxial tensile test. Curved 4 mm inner diameter, 0.5 mm thickness, and 150 mm length SIS grafts were designed. Small intestinal submucosa vascular grafts were preliminary tested in vivo in a porcine animal model (n=3) constructing an arteriovenous fistula between the carotid artery and the jugular vein; GORE-TEX grafts were implanted as control. Small intestinal submucosa grafts remained patent 46 ± 7 days against the control, 30 ± 3 days. Histology showed thrombus formation on the lumen (80% to 100% surface area) of all explanted grafts. Small intestinal submucosa grafts exhibited neovascularization and endothelial cells alignment on the graft wall, indicating regeneration. Biaxial tensile tests demonstrated no significant differences in Young's moduli between SIS grafts (ECirc = 2.5 ± 1.0 MPa, ELong = 5.7 ± 2.6 MPa) and native artery (ECirc = 1.4 ± 0.8 MPa, ELong = 5.5 ± 1.1 MPa), indicating similar wall stiffness. This study proposes an innovative design of a tissue-engineered vascular graft for hemodialysis access that, besides its structural characteristics similar to those of current synthetic grafts, could enhance biological performance because of its composition.
Hybrid Complex Coacervate Dompé, Marco; Cedano-Serrano, Francisco Javier; Vahdati, Mehdi ...
Polymers,
02/2020, Letnik:
12, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Underwater adhesion represents a huge technological challenge as the presence of water compromises the performance of most commercially available adhesives. Inspired by natural organisms, we have ...designed an adhesive based on complex coacervation, a liquid-liquid phase separation phenomenon. A complex coacervate adhesive is formed by mixing oppositely charged polyelectrolytes bearing pendant thermoresponsive poly(
-isopropylacrylamide) (PNIPAM) chains. The material fully sets underwater due to a change in the environmental conditions, namely temperature and ionic strength. In this work, we incorporate silica nanoparticles forming a hybrid complex coacervate and investigate the resulting mechanical properties. An enhancement of the mechanical properties is observed below the PNIPAM lower critical solution temperature (LCST): this is due to the formation of PNIPAM-silica junctions, which, after setting, contribute to a moderate increase in the moduli and in the adhesive properties only when applying an ionic strength gradient. By contrast, when raising the temperature above the LCST, the mechanical properties are dominated by the association of PNIPAM chains and the nanofiller incorporation leads to an increased heterogeneity with the formation of fracture planes at the interface between areas of different concentrations of nanoparticles, promoting earlier failure of the network-an unexpected and noteworthy consequence of this hybrid system.
The image represents a complex coacervate‐based adhesive which can be injected through a syringe (1) on a tissue wound. When released in a physiological environment, the liquid adhesive turns into a ...solid (2). The liquid‐to‐solid transition is exclusively ascribed to the formation of non‐covalent interactions, e.g. electrostatic and hydrophobic (3), between the polymer chains constituting the material. More details can be found in article number 1901785 by Marco Dompé, Marleen Kamperman, and co‐workers.
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