Bioinspired functional organohydrogels with synergistic multiphases heterostructure

Developing Safe Organohydrogel Sunscreens Using Polyelectrolyte-Betaine Surfactant Complexes

Oil-in-water emulsions are extensively used in skincare products due to their improved texture, stability, and effectiveness. There is limited success in developing effective delivery systems that can selectively target the active sunscreen ingredients onto the skin surface. Herein, an organohydrogel was prepared by physical cross-linking of an oil-in-water nanoemulsion with chitosan under neutral pH conditions. In the presence of a small quantity of coconut oil, lauramidopropyl betaine and glycerol were able to emulsify the active sunscreen ingredients into nanoscale droplets with enhanced ultraviolet light absorption. A facile pH-triggered interfacial cross-linking approach was applied to transform the nanoemulsion into an organohydrogel sunscreen. Furthermore, the organohydrogel sunscreen displayed encouraging characteristics including efficient UV-blocking capacity, resistance to water, simple removal, and minimal skin penetration. This facile approach provides an effective pathway for scaling up the organohydrogels, which are highly suitable for the safe application of sunscreen.

Cryogelation reactions and cryogels: principles and challenges

Cryogelation is a powerful technique for producing macroporous hydrogels called cryogels. Although cryogelation reactions and cryogels were discovered more than 70 years ago, they attracted significant interest only in the last 20 years mainly due to their extraordinary properties compared to the classical hydrogels such as a high toughness, almost complete squeezability, a mechanically stable porous structure with honeycomb arrangement, poroelasticity, and fast responsivity against external stimuli. In this mini review, general properties of cryogelation systems including the cryoconcentration phenomenon responsible for the unique properties of the cryogels are discussed. The squeezability and poroelasticity of cryogels comparable to those seen with articular cartilage are also discussed. Cryogelation reactions conducted within the pores of preformed cryogels and some novel cryogels with attractive properties are then discussed in the last section.

Silk Fibroin-Based Shape-Memory Organohydrogels with Semicrystalline Microinclusions

Inspired by nature, we designed organohydrogels (OHGs) consisting of a silk fibroin (SF) hydrogel as the continuous phase and the hydrophobic microinclusions based on semicrystalline poly(n-octadecyl acrylate) (PC18A) as the dispersed phase. SF acts as a self-emulsifier to obtain oil-in-water emulsions, and hence, it is a versatile and green alternative to chemical emulsifiers. We first prepared a stable oil-in-water emulsion without an external emulsifier by dispersing the n-octadecyl acrylate (C18A) monomer in an aqueous SF solution. To stabilize the emulsions for longer times, gelation in the continuous SF phase was induced by the addition of ethanol, which is known to trigger the conformational transition in SF from random coil to β-sheet structures. In the second step, in situ polymerization of C18A droplets in the emulsion system was conducted under UV light in the presence of a photoinitiator to obtain high-strength OHGs with shape-memory function, and good cytocompatibility. The incorporation of hydrophilic N,N-dimethylacrylamide and noncrystallizable hydrophobic lauryl methacrylate units in the hydrogel and organogel phases of OHGs, respectively, further improved their mechanical and shape-memory properties. The shape-memory OHGs presented here exhibit switchable viscoelasticity and mechanics, a high Young's modulus (up to 4.3 ± 0.1 MPa), compressive strength (up to 2.5 ± 0.1 MPa), and toughness (up to 0.68 MPa).

Anti-Freezing Nanocomposite Organohydrogels with High Strength and Toughness

Hydrogels based on nanocomposites (NC) structure have acquired a great deal of interest, but they are still limited by relatively low mechanical strength, inevitably losing elasticity when applied below subzero temperatures, due to the formation of ice crystallization. In this study, an anti-freezing and mechanically strong Laponite NC organohydrogel was prepared by a direct solvent replacement strategy of immersing Laponite NC pre-hydrogel into ethylene glycol (EG)/water mixture solution. In the organohydrogel, a part of water molecules was replaced by EG, which inhibited the formation of ice crystallization even at extremely low temperatures. In addition, the formation of hydrogen bonds between Laponite and the monomers of N-isopropylacrylamide (NIPAM) and hydroxyethyl acrylate (HEA) endowed the organohydrogels with high mechanical strength and toughness. The NC organohydrogel can maintain its mechanical flexibility even at −25 °C. The compressive stress, tensile stress, and elongation at the break of N₅H₅L reached 3871.71 kPa, 137.05 kPa, and 173.39%, respectively, which may be potentially applied as ocean probes in low temperature environment.

Temperature-Sensitive Anti-Inflammatory Organohydrogels Containing Janus Particle Stabilized Phase-Change Microinclusions

A fabrication strategy for multifunctional organohydrogels is proposed, which combines phase-change microinclusions within a double-network (DN) hydrogel under the stabilization of Janus particles. Janus particles possess reactivity and colloidal stability for more robust organohydrogels, while the interstice among Janus particles enhances the mass transfer between the phase interfaces. Moreover, DN hydrogels are achieved through dynamic cross-linking networks, endowing organohydrogels with injectability and self-healing performance. Phase-change microinclusions are beneficial to the organohydrogels with temperature-responsive mechanical property and temperature-programed shape-memory performance. Organohydrogels can be employed for temperature therapy through the melting-crystallization process of phase-change microinclusions. Simultaneously, the payloads within microinclusions can be released for antibacteria upon melting the encapsulated wax. The organohydrogels can be served as an ideal dressing with temperature-responsive mechanical property, temperature therapy effectiveness, and temperature-triggered antibacterial ability.

Bioinspired organohydrogels with heterostructures: Fabrications, performances, and applications

Since emerging in 1960, the artificial hydrogels have garnered enormous attentions in scientific community due to their high level of similarities to biological soft tissues in both structures and properties. With the proceeding of research, the concern of hydrogels is gradually shifted from fundamental investigation to abundant functionalization. In contrast to the natural soft tissues, the current artificial hydrogels still possess relatively simple structures and unsatisfactory environmental adaptability, extremely limiting their practical applications in complex environments. Enlightened by the prominent adaptability of biological organisms, the binary cooperative complementary principle is utilized to develop bioinspired organohydrogels by combining two components with opposite but cooperative physiochemical features. The present review provides the advanced progresses of bioinspired organohydrogels with sophisticated heterogeneous networks and desirably environmental adaptabilities. We clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples, including macroscopic organohydrogels, organohydrogels with binary solvent, organohydrogels with heteronetworks, and emulsion-based organohydrogels. Meanwhile, the intriguing features of the reported organohydrogels, such as temperature resistance, switchable mechanics, adaptive wettability, and opposite components compatibility, are also clearly highlighted with a short overview of their promising applications. Ultimately, the current challenges and perspectives on the future development of bioinspired organohydrogels are also discussed.