Arrested Phase Separation Enables High-Performance Keratoprostheses

Natural Extracellular Matrix Scaffold-Based Hydrogel Corneal Patch with Temperature and Light-Responsiveness for Penetrating Keratoplasty and Sutureless Stromal Defect Repair

Corneal transplantation remains the gold standard for treating corneal blindness; however, it is hampered globally by donor shortages and the complexity of suture-dependent procedures. Tissue-engineered corneas have demonstrated potential as corneal equivalents. Nevertheless, the development of adhesive corneal patches and full-thickness corneal substitutes remains challenging. In this study, a multifunctional hydrogel corneal patch (MHCP) is constructed by integrating a dual-crosslinked hybrid hydrogel with temperature and light responsiveness with a natural extracellular matrix scaffold. When applied to the ocular surface, MHCP spontaneously releases adhesives at body temperature and forms a stable adhesion with the recipient cornea through photocuring. In addition to its inherent mechanical, optical, and ultrastructural characteristics, which are similar to those of the natural stroma, MHCP demonstrates excellent suture resistance, anti-swelling, and anti-degradation properties after curing. MHCP promotes the proliferation and migration of corneal epithelial cells in vitro and maintains the phenotype of corneal stromal cells. In vivo, MHCP maintains graft hydration and restores corneal structural integrity and transparency during penetrating keratoplasty of various sizes and sutureless lamellar keratoplasty. Collectively, given the advantages of native stroma-like characteristics, operation-facilitating multiple functions, and convenient preparation, MHCP is a promising corneal substitute for clinical applications.

Glycerol Modulated Collagen Fibril Evolution and Lamellar Organization for Biomimetic Corneal Substitutes Construction

Collagen as the main structural component of the cornea exhibits unique and highly organized fibril lamellae, which contribute to the maintenance of corneal structure and transparency. Nevertheless, collagen assembly in vitro to create ideal artificial corneal substitutes with human cornea comparable thickness and optics is still limited. Here, glycerol as a regulator can reconcile collagen thickness, transparency, and permeability, a conflicting goal by current keratoprosthesis strategies. Structure analysis reveals that glycerol treatment induces collagen hydrogels to undergo a sequential three-step multiscale structural evolution: weakened collagen crystallization at the molecular level, followed by ordered and distanced microfibril packaging at the nanoscale, and ultimately lamellar structure as well as fibril diameter and spacing-dependent optics at a macroscopic level. Such ultrastructure is then stabilized by oxazolidine crosslinking to obtain a collagen-based artificial corneal substitute (Col-Gly-OX) with optimal integration of optical clarity, mechanical robustness, high permeability, manufacturability, easy preservation and in vitro biocompatibility. Further in vivo study demonstrates that Col-Gly-OX displays excellent tissue integration, epithelialization, and stromal remodeling in a rabbit lamellar keratectomy. Overall, this work illustrates the potential of glycerol regulator to mediate the multiscale structural organization of collagen, providing a green, simple and effective strategy for the development of bionic artificial cornea.

Rapid spread, slow evaporation: a long-lasting water film on hydrogel nanowire arrays for continuous wearables

A successful flexible wearable not only has to fulfill its function, but also has to ensure long-term wettability and comfort during wearing. In biological systems, tears spread rapidly across the cornea to ensure clear imaging while slowly evaporating to maintain moisture in the eyes. This dynamic behavior of 'rapid spread, slow evaporation' ensures durative humidity and comfort, which can provide design guidelines for continuous wearable devices. However, realizing this dynamic process in vitro remains a challenge. Herein, inspired by a healthy ocular surface, we biomimetically construct a hybrid surface featuring mucin-like hydrophilic layer@hydrogel nanowire arrays (HL@HNWs). A droplet (2 μL) rapidly spreads into a thin film, stabilizing for ∼10 minutes, whereas the contrast sample rapidly ruptures and dewets within 1 minute. We demonstrate that enhancing the proportion of hydrated water (HW), which includes intermediate water (IW) and bound water (BW), and introducing the capillary resistance of the nanowire arrays could synergistically stabilize the water film and improve the wettability. Hydrogel-based nanowire array contact lenses can ensure wettability during continuous wear, and a stable water film can substantially improve comfort and provide superior visual quality.

Engineering a polyvinyl butyral hydrogel as a thermochromic interlayer for energy-saving windows

Achieving mastery over light using thermochromic materials is crucial for energy-saving glazing. However, challenges such as high production costs, limited durability, and recyclability issues have hindered their widespread application in buildings. Herein, we develop a glass interlayer made of a polyvinyl butyral-based hydrogel swollen with LiCl solution. In addition to a fast, isochoric, and reversible transparency-to-opacity transition occurring as ambient temperatures exceed thermally comfortable levels, this hydrogel uniquely encompasses multiple features such as frost resistance, recyclability, scalability, and toughness. The combination of these features is achieved through a delicate balance of polyvinyl butyral's amphiphilicity and the suppression of network-forming phase separation. This design endows a nanostructured polyvinyl butyral-LiCl composite gel with swollen molecular segments linked by dispersed cross-linking sites in the form of hydrophobic nano-nodules. Upon laminating this hydrogel (a thickness of 0.3 mm), the resultant glazing product demonstrates approximately 90% luminous transmittance even at sub-zero temperatures, along with a significant modulation of solar and infrared radiation at 80.8% and 68.5%, respectively. Through simulations, we determined that windows equipped with the hydrogel could reduce energy consumption by 36% compared to conventional glass windows in warm seasons. The widespread adoption of polyvinyl butyral in construction underscores the promise of this hydrogel as a thermochromic interlayer for glazing.