Sutureless Transplantation of Amniotic Membrane Using a Visible Light-Curable Protein Bioadhesive for Ocular Surface Reconstruction

Strong Protein Adhesives through Lanthanide-enhanced Structure Folding and Stack Density

Generating strong adhesion by engineered proteins has the potential for high technical applications. Current studies of adhesive proteins are primarily limited to marine organisms, e.g., mussel adhesive proteins. Here, we present a modular engineering strategy to generate a type of exotic protein adhesives with super strong adhesion behaviors. In the protein complexes, the lanmodulin (LanM) underwent α-helical conformational transition induced by lanthanides, thereby enhancing the stacking density and molecular interactions of adhesive protein. The resulting adhesives exhibited outstanding lap-shear strength of ≈31.7 MPa, surpassing many supramolecular and polymer adhesives. The extreme temperature (-196 to 200 °C) resistance capacity and underwater adhesion performance can significantly broaden their practical application scenarios. Ex vivo and in vivo experiments further demonstrated the persistent adhesion performance for surgical sealing and healing applications.

Application of Convergent Science and Technology toward Ocular Disease Treatment

Eyes are one of the main critical organs of the body that provide our brain with the most information about the surrounding environment. Disturbance in the activity of this informational organ, resulting from different ocular diseases, could affect the quality of life, so finding appropriate methods for treating ocular disease has attracted lots of attention. This is especially due to the ineffectiveness of the conventional therapeutic method to deliver drugs into the interior parts of the eye, and the also presence of barriers such as tear film, blood-ocular, and blood-retina barriers. Recently, some novel techniques, such as different types of contact lenses, micro and nanoneedles and in situ gels, have been introduced which can overcome the previously mentioned barriers. These novel techniques could enhance the bioavailability of therapeutic components inside the eyes, deliver them to the posterior side of the eyes, release them in a controlled manner, and reduce the side effects of previous methods (such as eye drops). Accordingly, this review paper aims to summarize some of the evidence on the effectiveness of these new techniques for treating ocular disease, their preclinical and clinical progression, current limitations, and future perspectives.

Molecularly Engineered Protein Glues with Superior Adhesion Performance

Naturally inspired proteins are investigated for the development of bioglues that combine adhesion performance and biocompatibility for biomedical applications. However, engineering such adhesives by rational design of the proteins at the molecular level is rarely reported. Herein, it is shown that a new generation of protein-based glues is generated by supramolecular assembly through de novo designed structural proteins in which arginine triggers robust liquid-liquid phase separation. The encoded arginine moieties significantly strengthen multiple molecular interactions in the complex, leading to ultrastrong adhesion on various surfaces, outperforming many chemically reacted and biomimetic glues. Such adhesive materials enable quick visceral hemostasis in 10 s and outstanding tissue regeneration due to their robust adhesion, good biocompatibility, and superior antibacterial capacity. Remarkably, their minimum inhibitory concentrations are orders of magnitude lower than clinical antibiotics. These advances offer insights into molecular engineering of de novo designed protein glues and outline a general strategy to fabricate mechanically strong protein-based materials for surgical applications.

Sutureless transplantation using a semi-interpenetrating polymer network bioadhesive for ocular surface reconstruction

The conjunctiva covers the largest area of ocular surface and is responsible for tear balance and clear vision. After trauma or surgery, the conjunctiva is prone to scarring and contracture. Transplantation with suture often implies numerous complications, such as inflammation, suture erosion, granuloma. And the suture needs to be removed, which means a secondary trauma. In this study, a (GMO) for sutureless conjunctival transplantation was developed based on a semi-interpenetrating polymer network (sIPN) consisting of gelatin methacrylate (GelMA) and oxidized hyaluronic acid (OHA). The maximum adhesion strength was 157 ± 17 kPa, and the burst pressure was 357 ± 29 kPa, which was 15 times higher than the human intraocular pressure (IOP). GMO bioadhesive hydrogel significantly improved surgical efficiency and secured the collagen scaffold firmly to a rabbit conjunctival defect. The sutureless transplantation approach revealed the promoted tissue repair without scar. In conclusion, GMO bioadhesive may be an attractive alternative to suture for ocular surface reconstruction by avoiding suture-related complications and improving clinical outcome. STATEMENT OF SIGNIFICANCE: Conjunctival tissue is prone to scarring and contracture after trauma, and surgery with sutures often implies numerous complications. In this study, the ocular surface reconstruction was achieved by sutureless transplantation of conjunctival scaffold using bioadhesive hydrogel. The prepared GMO bioadhesive based on the semi-interpenetrating network of gelatin methacrylate (GelMA) and oxidized hyaluronic acid (OHA) had favorable adhesion and mechanical properties. The sutureless transplantation approach significantly improved the operation efficiency, avoided suture-related complications, and promoted the regeneration of conjunctiva. This study highlights the great potential of the sutureless repair strategy for clinical application in ocular surface reconstruction.

User-demand fast-curable ocular glues enforced by multilength tunable networks

Achieving fast and secure wound closure without ocular foreign body sensation is highly desired in ophthalmologic surgery. Sutureless approaches using tissue adhesives are gaining popularity, but their practical use is limited by the difficulty in controlling adhesion time and satisfying safety standards without compromising adhesive performance. Herein, we report user-demand hydrogel-forming ocular glues based on multilength photo-crosslinkable hyaluronic acid (HA), achieving firm tissue adhesion under wet and dynamic conditions and possessing cornea-like optical transparency. The HA-based photocurable glue (HA photoglue) quickly seals wounds upon nontoxic low-energy light exposure (320-500 nm, < 5 s, < 1 J cm-2), and its mechanical and adhesive properties are improved by introducing short and long crosslinkable moieties into HA through one-step synthesis, forming multilength networks. Furthermore, the HA photoglue provides stable sealing in wet environments like ocular mucous surface, a clear vision with a light transmittance of more than 95% over the entire visible range, and a lubricating surface with minimal ocular sensation (generating less than 10% frictional force than suture groups). In a rabbit corneal incision model, the HA photoglue showed improved wound healing efficacy based on histological evaluation compared to control groups.

Crosslinked Decellularized Porcine Pericardium as a Substrate for Conjunctival Reconstruction

Seeking for suitable conjunctival reconstruction substitutes to overcome the limitations of current substitutes, such as amniotic membrane, is urgent. Decellularized tissues have become a promising strategy for tissue engineering. In this study, we prepared decellularized porcine pericardium (DPP) scaffolds by the phospholipase A2 method and crosslinked them with aspartic acid (Asp) and human endothelial growth factor (hEGF) to enhance biological performance on the DPP, obtaining DPP-Asp-hEGF scaffolds. In vitro DPP showed lower apoptosis, highly desirable, well preservation of extracellular matrix components, and favorable macro-microstructure, which was confirmed by histology, immunofluorescence, electron microscopy, collagen and DNA quantification, and cytotoxicity assay, compared to the native porcine pericardium (NPP). The crosslinked efficacy of the DPP-Asp-hEGF was furtherer verified by in vitro experiments with Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Through animal models of conjunctiva defect model, the DPP-Asp-hEGF revealed a closed, multilayer epithelium with an equal amount of goblet cells and no indication for conjunctival scarring after 28 days, compared to amniotic membrane (AM) groups and sham groups. These results suggested that DPP-Asp-hEGF can offer a good conjunctival reconstructive substitute both in structure and in function.

Recent Advances in Bioinspired Hydrogels with Environment- Responsive Characteristics for Biomedical Applications

The development of hydrogel-integrated soft materials via the incorporation of therapeutic medicines into bio-compatible hydrogels, serving as host, will significantly contribute to advances in medical diagnosis and treatment. Furthermore, intelligent hydrogels having the ability to respond to local environmental conditions offer a promising approach for the development of novel solutions in the biomedical field. Bioinspired intelligent hydrogels are now becoming a potentially powerful biomaterial class for tissue engineering, drug delivery, and medical device. Recent advances include bioinspired intelligent hydrogels that possess unique mechanical and optical properties as a result of their nature-inspired complex-structured design. In this review, we highlight the latest advances in intelligent bionic hydrogels, as well as strategies targeting smart response of their characteristics across multiple dimensions (such as temperature, light, pH, among others). Finally, the potential development and prospective application of mimicking the natural intelligence of multifunctional medical hydrogels are also discussed. This article is protected by copyright. All rights reserved.

Bioengineered Protein-based Adhesives for Biomedical Applications

Protein-based adhesives with their robust adhesion performance and excellent biocompatibility have been extensively explored over years. In particular, the unique adhesion behaviours of mussel and sandcastle worm inspired the development of synthetic adhesives. However, the chemical synthesized adhesives often demonstrate weak underwater adhesion performance and poor biocompatibility/biodegradability, limiting their further biomedical applications. In sharp contrast, genetically engineering endows the protein-based adhesives the ability to maintain underwater adhesion property as well as biocompatibility/biodegradability. Herein, we outline recent advances in the design and development of protein-based adhesives by genetic engineering. We summarize the fabrication and adhesion performance of elastin-like polypeptide-based adhesives, followed by mussel foot protein (mfp) based adhesives and other sources protein-based adhesives, such as, spider silk spidroin and suckerin. In addition, the biomedical applications of these bioengineered protein-based adhesives are presented. Finally, we give a brief summary and perspective on the future development of bioengineered protein-based adhesives.