Practical recombinant hybrid mussel bioadhesive fp-151

Mussel adhesive protein blended with gelatin loaded into nanotube titanium dental implants enhances osseointegration

The purpose of this study was to investigate whether mussel adhesive protein (MAP) blended with gelatin loaded into nanotube titanium (Ti) dental implants enhances osseointegration and supports bone formation. Cell viability, crystal violet staining, Western blot analysis, alizarin red S staining, alkaline phosphatase (ALP) activity, micro-computed tomography (μ-CT), hematoxylin and eosin (H&E), and immunohistochemistry (IHC) staining were employed to test the biocompatibility of MAP blended with gelatin (MAP/Gel). MC3T3 E1 cells were used for in vitro and Sprague-Dawley rats for in vivo models in this study. MC3T3 E1 cells cultured in MAP/Gel loaded into nanotube Ti surface demonstrated activation of FAK-PI3K-MAPKs-Wnt/β-catenin signaling pathway and enhanced osteogenic differentiation. μ-CT, H&E, and IHC staining confirmed that MAP/Gel dental implants promoted bone regeneration around the nanotube Ti implants by upregulation of Runx-2, BMP-2/7, Osterix, and OPG in rat mandible model. MAP/Gel supports osseointegration of dental implant after implantation. It is hypothesized that MAP/Gel loaded into nanotube Ti dental implants may be applicable as a potential treatment for bone formation and proper integration of dental implants with alveolar bone. Graphical abstract.

Enhanced antibacterial activity of titanium by surface modification with polydopamine and silver for dental implant application

BACKGROUND

Biofilm formation and microbial colonization on the surface of implant devices may cause dental caries and peri-implantitis. Therefore, various surface treatments have been developed to improve the antibacterial activity of titanium implant.

METHODS

Silver-loaded polydopamine coating was formed by immersing pure titanium in dopamine hydrochloride/HCl buffer solution for 24 h in 50 mL silver nitrate solutions with different concentrations for 30 min. Microbial growth inhibition and microbial growth curve analyses for bacterial solutions of Streptococcus mutans and Porphyromonas gingivalis incubated with the specimens were respectively conducted by counting the numbers of colonies on agar solid medium and by measuring absorbance using enzyme-linked immunosorbent assay reader.

RESULTS

Silver nanoparticles were uniformly distributed over the whole surface of the polydopamine and silver-coated titanium specimens. The numbers of microbial colonies for both bacteria cultured with surface-modified titanium were significantly lower than those cultured with uncoated titanium. When Streptococcus mutans and Porphyromonas gingivalis were cultured with surface-modified titanium, the lag phase of the growth curves for both bacteria was continually maintained, whereas the lag phase for Streptococcus mutans and Porphyromonas gingivalis changed to exponential phase after 9 and 15 h, respectively, when both bacteria were cultured with uncoated titanium.

CONCLUSION

It was confirmed that the coating of polydopamine and silver on the surface of titanium effectively retards the microbial growth, which can cause the formation of biofilm and pathogenesis of gum disease in the mouth.

Covalent immobilization of biomolecules on stent materials through mussel adhesive protein coating to form biofunctional films

It is widely accepted that surface biofunctional modification may be an effective approach to improve biocompatibility and confer new bioactive properties on biomaterials. In this work, mussel adhesive protein (MAP) was applied as a coating on 316 L stainless steel substrates (316 L SS) and stents, and then either immobilized VEGF or CD34 antibody were added to create biofunctional films. The properties of the MAP coating were characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and a water contact angle test. Universal tensile testing showed that the MAP coating has adequate adhesion strength on a 316 L stainless steel material surface. Subsequent cytotoxicity and hemolysis rate tests showed that the MAP coatings have good biocompatibility. Moreover, using N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysulfosussinimide (EDC/NHS) chemistry, VEGF and CD34 antibody were immobilized on the MAP coatings. The amount and immobilized yield of VEGF on the MAP coatings were analyzed by enzyme-linked immuno-assays (ELISA). Finally, an endothelial cells culture showed that the VEGF biofunctional film can promote the viability and proliferation of endothelial cells. An in vitro CD34⁺ cells capturing test also verified the bioactive properties of the CD34 antibody coated stents. These results showed that the MAP coatings allowed effective biomolecule immobilization, providing a promising platform for vascular device modification.

Expanding the DOPA Universe with Genetically Encoded, Mussel-Inspired Bioadhesives for Material Sciences and Medicine

Catechols are a biologically relevant group of aromatic diols that have attracted much attention as mediators of adhesion of "bio-glue" proteins in mussels of the genus Mytilus. These organisms use catechols in the form of the noncanonical amino acid l-3,4-dihydroxyphenylalanine (DOPA) as a building block for adhesion proteins. The DOPA is generated post-translationally from tyrosine. Herein, we review the properties, natural occurrence, and reactivity of catechols in the design of bioinspired materials. We also provide a basic description of the mussel's attachment apparatus, the interplay between its different molecules that play a crucial role in adhesion, and the role of post-translational modifications (PTMs) of these proteins. Our focus is on the microbial production of mussel foot proteins with the aid of orthogonal translation systems (OTSs) and the use of genetic code engineering to solve some fundamental problems in the bioproduction of these bioadhesives and to expand their chemical space. The major limitation of bacterial expression systems is their intrinsic inability to introduce PTMs. OTSs have the potential to overcome these challenges by replacing canonical amino acids with noncanonical ones. In this way, PTM steps are circumvented while the genetically programmed precision of protein sequences is preserved. In addition, OTSs should enable spatiotemporal control over the complex adhesion process, because the catechol function can be masked by suitable chemical protection. Such caged residues can then be noninvasively unmasked by, for example, UV irradiation or thermal treatment. All of these features make OTSs based on genetic code engineering in reprogrammed microbial strains new and promising tools in bioinspired materials science.

Developing Regenerative Treatments for Developmental Defects, Injuries, and Diseases Using Extracellular Matrix Collagen-Targeting Peptides

Collagen is the most widespread extracellular matrix (ECM) protein in the body and is important in maintaining the functionality of organs and tissues. Studies have explored interventions using collagen-targeting tissue engineered techniques, using collagen hybridizing or collagen binding peptides, to target or treat dysregulated or injured collagen in developmental defects, injuries, and diseases. Researchers have used collagen-targeting peptides to deliver growth factors, drugs, and genetic materials, to develop bioactive surfaces, and to detect the distribution and status of collagen. All of these approaches have been used for various regenerative medicine applications, including neovascularization, wound healing, and tissue regeneration. In this review, we describe in depth the collagen-targeting approaches for regenerative therapeutics and compare the benefits of using the different molecules for various present and future applications.

Bio-inspired swellable hydrogel-forming double-layered adhesive microneedle protein patch for regenerative internal/external surgical closure

Significant tissue damage, scarring, and an intense inflammatory response remain the greatest concerns for conventional wound closure options, including sutures and staples. In particular, wound closure in internal organs poses major clinical challenges due to air/fluid leakage, local ischemia, and subsequent impairment of healing. Herein, to overcome these limitations, inspired by endoparasites that swell their proboscis to anchor to host's intestines, we developed a hydrogel-forming double-layered adhesive microneedle (MN) patch consisting of a swellable mussel adhesive protein (MAP)-based shell and a non-swellable silk fibroin (SF)-based core. By possessing tissue insertion capability (7-times greater than the force for porcine skin penetration), MAP-derived surface adhesion, and selective swelling-mediated physical entanglement, our hydrogel-forming adhesive MN patch achieved ex vivo superior wound sealing capacity against luminal leaks (139.7 ± 14.1 mmHg), which was comparable to suture (151.0 ± 23.3 mmHg), as well as in vivo excellent performance for wet and/or dynamic external and internal tissues. Collectively, our bioinspired adhesive MN patch can be successfully used in diverse practical applications ranging from vascular and gastrointestinal wound healing to transdermal delivery for pro-regenerative or anti-inflammatory agents to target tissues.

Exploiting mammalian low-complexity domains for liquid-liquid phase separation-driven underwater adhesive coatings

Many biological materials form via liquid-liquid phase separation (LLPS), followed by maturation into a solid-like state. Here, using a biologically inspired assembly mechanism designed to recapitulate these sequential assemblies, we develop ultrastrong underwater adhesives made from engineered proteins containing mammalian low-complexity (LC) domains. We show that LC domain-mediated LLPS and maturation substantially promotes the wetting, adsorption, priming, and formation of dense, uniform amyloid nanofiber coatings on diverse surfaces (e.g., Teflon), and even penetrating difficult-to-access locations such as the interiors of microfluidic devices. Notably, these coatings can be deposited on substrates over a broad range of pH values (3 to 11) and salt concentrations (up to 1 M NaCl) and exhibit strong underwater adhesion performance. Beyond demonstrating the utility of mammalian LC domains for driving LLPS in soft materials applications, our study illustrates a powerful example of how combining LLPS with subsequent maturation steps can be harnessed for engineering protein-based materials.

A mitochondrial genome phylogeny of Mytilidae (Bivalvia: Mytilida)

The family Mytilidae is a family of bivalve mussels that are distributed worldwide in diverse marine habitats. Within the family, classification systems and phylogenetic relationships among subfamilies remain not yet fully resolved. In this study, we newly determined 9 mitochondrial genome sequences from 7 subfamilies: Bathymodiolus thermophilus (Bathymodiolinae), Modiolus nipponicus (Modiolinae), Lithophaga curta (the first representative of Lithophaginae), Brachidontes mutabilis (Brachidontinae), Mytilisepta virgata (Brachidontinae), Mytilisepta keenae (Brachidontinae), Crenomytilus grayanus (Mytilinae), Gregariella coralliophaga (Crenellinae), and Septifer bilocularis (the first representative of Septiferinae). Phylogenetic trees using maximum likelihood and Bayesian inference methods for 28 mitochondrial genomes (including 19 previously published sequences) showed two major clades with high support values: Clade 1 ((Bathymodiolinae + Modiolinae) + (Lithophaginae + Limnoperninae)) and Clade 2 (((Mytilinae + Crenellinae) + Septiferinae) + Brachidontinae). The position of the genus Lithophaga (representing Lithophaginae) differed from a previously published molecular phylogeny. Divergence time analysis with a molecular clock indicated that lineage splitting among the major subfamilies of Mytilidae (including the habitat transition from marine to freshwater environments by ancestral Limnoperninae) occurred in the Mesozoic period, coinciding with high diversification rates of marine fauna during that time. This is the first mitochondrial genome-based phylogenetic study of the Mytilidae that covers nearly all subfamily members, excluding the subfamily Dacrydiinae.

Effect of mussel adhesive protein coating on osteogenesis in vitro and osteointegration in vivo to alkali-treated titanium with nanonetwork structures

Purpose: On the basis of reasonable superposition of various surface treatment methods, alkali-treated titanium with nanonetwork structures (TNS) was coated with mussel adhesive protein (MAP) and named TNS-MAP. The aims were to optimize the biological properties of TNS, endue it with new properties, and enhance its utility in clinical dental applications. Methods: TNS disks were coated with MAP and the product surface was characterized. Its osteogenic properties were determined by evaluating its effects on cell adhesion, cell proliferation, the expression of osteogenesis-related genes, and in vivo experiments. Results: The treated materials showed excellent hydrophilicity, good surface roughness, and advantages of both TNS and MAP. TNS-MAP significantly promoted initial cell attachment especially after 15 mins and 30 mins. At every time point, cell adhesion and proliferation, the detection rate of osteogenesis-related markers in the extracellular matrix, and the expression of osteogenesis-related genes were markedly superior on TNS-MAP than the control. The in vivo experiments revealed that TNS-MAP promoted new bone growth around the implants and the bone-implant interface. Conclusion: We verified through in vitro and in vivo experiments that we successfully created an effective TNS-MAP composite implant with excellent biocompatibility and advantages of both its TNS and MAP parent materials. Therefore, the new biocomposite implant material TNS-MAP may potentially serve in practical dentistry and orthopedics.

Multi-dimensional bioinspired tactics using an engineered mussel protein glue-based nanofiber conduit for accelerated functional nerve regeneration

Limited regenerative capacity of the nervous system makes treating traumatic nerve injuries with conventional polymer-based nerve grafting a challenging task. Consequently, utilizing natural polymers and biomimetic topologies became obvious strategies for nerve conduit designs. As a bioinspired natural polymer from a marine organism, mussel adhesive proteins (MAPs) fused with biofunctional peptides from extracellular matrix (ECM) were engineered for accelerated nerve regeneration by enhancing cell adhesion, proliferation, neural differentiation, and neurite formation. To physically promote contact guidance of neural and Schwann cells and to achieve guided nerve regeneration, MAP was fabricated into an electrospun aligned nanofiber conduit by introducing synthetic polymer poly(lactic-co-glycolic acid) (PLGA) to control solubility and mechanical property. In vitro and in vivo experiments demonstrated that the multi-dimensional tactics of combining adhesiveness from MAP, integrin-mediated interaction from ECM peptides (in particular, IKVAV derived from laminin α1 chain), and contact guidance from aligned nanofibers synergistically accelerated functional nerve regeneration. Thus, MAP-based multi-dimensional approach provides new opportunities for neural regenerative applications including nerve grafting. STATEMENT OF SIGNIFICANCE: Findings in neural regeneration indicate that a bioinspired polymer-based nerve conduit design should harmoniously constitute various factors, such as biocompatibility, neurotrophic molecule, biodegradability, and contact guidance. Here, we engineered three fusion proteins of mussel-derived adhesive protein with ECM-derived biofunctional peptides to simultaneously provide biocompatibility and integrin-based interactions. In addition, a fabrication of robust aligned nanofiber conduits containing the fusion proteins realized suitable biodegradability and contact guidance. Thus, our multi-dimensional strategy on conduit design provided outstanding biocompatibility, biodegradability, integrin-interaction, and contact guidance to achieve an accelerated functional nerve regeneration. We believe that our bioengineered mussel adhesive protein-based multi-dimensional strategy would offer new insights into the design of nerve tissue engineering biomaterials.

Combinational Biomimicking of Lotus Leaf, Mussel, and Sandcastle Worm for Robust Superhydrophobic Surfaces with Biomedical Multifunctionality: Antithrombotic, Antibiofouling, and Tissue Closure Capabilities

Surface wetting occurring in daily life causes undesired contaminations, which are critical issues in various fields. To solve these problems, the nonwetting property of a superhydrophobic (SH) surface has proven its utility by preventing contaminant infiltration, serious infections, or malfunction. However, the application of SH surfaces in the biomedical field has been limited due to the weak durability and toxicity of the related components. To overcome these limitations, we developed a robust and biocompatible SH surface through combinational biomimicking of three natural organisms, lotus leaf, mussel, and sandcastle worm, for the first time. Using the water-immiscible and polycationic characteristics of mussel adhesive protein (iMglue), an SH iMglue-SiO₂(TiO₂/SiO₂)₂ coating was fabricated by solution-based electrical charge-controlled layer-by-layer growth of nanoparticles (NPs). The fabricated iMglue-SiO₂(TiO₂/SiO₂)₂ SH surface showed excellent durable nonwetting properties and was applied to an intracatheter tube coating to develop antithrombotic catheters under blood flow. Furthermore, we developed a iMglue-employed SH patch for a tissue closure bandage by spraying hydrophobic SiO₂ NPs on the iMglue-covered cotton pads. The prepared iMglue-employing SH patch showed perfect bifunctionality with excellent antibiofouling and tissue closure capabilities. Our work presents a novel, useful strategy for fabricating a biomedically multifunctional, robust SH surface through combinational mimicking of natural organisms.

Prolonged cell persistence with enhanced multipotency and rapid angiogenesis of hypoxia pre-conditioned stem cells encapsulated in marine-inspired adhesive and immiscible liquid micro-droplets

Stem cell therapies are emerging regenerative treatments for ischemic and chronic diseases. Although high cell retention and prompt angiogenesis are prerequisites to improving efficacy, advancements have not yet been developed. Here, we proposed long-term surviving and angiogenesis-inducing stem cell with high cell retention thanks to fluid immiscible liquid micro-droplets bio-inspired by a glue modality 'complex coacervate' found in the sandcastle worm. Formed by the Coulombic force between polycationic MAP and polyanionic hyaluronic acid, the exploited coacervate micro-droplets enabled the encapsulation of stem cells. The underwater adhesiveness facilitated integrating the encapsulated stem cells onto various surfaces with impressive cell retention after facile injection. Stem cells encapsulated in the coacervate platform formed cell clusters capable of pre-adjusting to hypoxia by expressing hypoxia-inducible factor 1α (HIF-1α), increasing viability and reducing apoptosis under hypoxia and ischemia as well as normoxia. Interestingly, multipotent and angiogenic factors were significantly enhanced by HIF-1α expression. In the in vivo evaluation, the coacervate platform showed impressive angiogenesis with biocompatibility and long-term cell retention capacity with sustainable release as protein factories. Therefore, the proposed MAP-based water-immiscible, injectable, sticky, and bioactive 3D coacervate micro-droplets offers a promising tool for chronic diseases in body fluid-rich environments. STATEMENT OF SIGNIFICANCE: High cell retention, long-term survival, and rapid angiogenesis are prerequisites of successful stem cell therapy. However, no previous advancements have simultaneously satisfied all of these requirements. In this work, we clearly developed a novel, revolutionary stem cell carrier platform with underwater adhesiveness from a mussel-derived glue protein and water immiscibility from a sandcastle-worm-inspired glue modality via 'complex coacervation'. To the best of our knowledge, no report has emerged employing coacervate as a stem cell therapeutic platform. This fluid-immiscible, injectable, sticky, and bioactive 3-dimensional stem cell micro-droplets demonstrated the excellent stem cell retention and viability under hypoxia environments and enhanced multipotent and angiogenic effects with minimal immune response.

Biomimetic characteristics of mussel adhesive protein-loaded collagen membrane in guided bone regeneration of rabbit calvarial defects

Purpose

The aim of the present study was to evaluate the biocompatibility and barrier function of mussel adhesive protein (MAP)-loaded collagen membranes in guided bone regeneration (GBR).

Methods

Eight male New Zealand white rabbits were used. Four circular defects (diameter: 8 mm) were created in the calvarium of each animal. The defects were randomly assigned to 1) a negative control group, 2) a cyanoacrylate (CA)-loaded collagen membrane group (the CA group), 3) a MAP-loaded collagen membrane group (the MAP group), and 4) a group that received a polycaprolactone block with MAP-loaded collagen membrane (the MAP-PCL group). Specimens were harvested at 2 weeks (n=4) and 8 weeks (n=4) postoperatively for observational histology and histometric analysis.

Results

In the histologic analysis, MAP was completely absorbed without any byproducts. In contrast, some of the CA adhesive remained, showing an inflammatory reaction, at 8 weeks. In the MAP-PCL group, the MAP-loaded collagen membranes served as a barrier membrane despite their fast degradation in GBR. No significant difference was found in the amount of new bone between the MAP-PCL and MAP groups (1.82±0.86 mm² and 2.60±0.65 mm², respectively).

Conclusions

The MAP-loaded collagen membrane functioned efficiently in this rabbit calvarial GBR model, with excellent biocompatibility. Further research is needed to assess clinical applications in defect types that are more challenging for GBR than those used in the current model.

Sprayable Adhesive Nanotherapeutics: Mussel-Protein-Based Nanoparticles for Highly Efficient Locoregional Cancer Therapy

Following surgical resection for primary treatment of solid tumors, systemic chemotherapy is commonly used to eliminate residual cancer cells to prevent tumor recurrence. However, its clinical outcome is often limited due to insufficient local accumulation and the systemic toxicity of anticancer drugs. Here, we propose a sprayable adhesive nanoparticle (NP)-based drug delivery system using a bioengineered mussel adhesive protein (MAP) for effective locoregional cancer therapy. The MAP NPs could be administered to target surfaces in a surface-independent manner through a simple and easy spray process by virtue of their unique adhesion ability and sufficient dispersion property. Doxorubicin (DOX)-loaded MAP NPs (MAP@DOX NPs) exhibited efficient cellular uptake, endolysosomal trafficking, and subsequent low pH microenvironment-induced DOX release in cancer cells. The locally sprayed MAP@DOX NPs showed a significant inhibition of tumor growth in vivo, resulting from the prolonged retention of the MAP@DOX NPs on the tumor surface. Thus, this adhesive MAP NP-based spray therapeutic system provides a promising approach for topical drug delivery in adjuvant cancer therapy.

Coacervation of the Recombinant Mytilus galloprovincialis Foot Protein-3b

The underwater adhesion of marine mussels is a fascinating example of how proteinaceous adhesives, although water-soluble to begin with, can be used in seawater. Marine mussels adhere to the substrate via adhesive plaques, where the adhesive proteins are located especially at the substratum's interface. One major compound of the adhesives in Mytilidae is the mussel foot protein 3b (mfp-3b). Here, recombinant mfp-3b (rmfp-3b) was produced in Escherichia coli. rmfp-3b showed upper critical solution temperature (UCST) mediated complex coacervation at pH 3.0 in the presence of citrate yielding a liquid-liquid phase separation. Further, the rmfp-3b coacervation could also be induced in seawater conditions such as the respective pH and ionic strength, but without UCST behavior. In particular, sulfate and citrate anions could significantly induce complex coacervation. This study provides insights into the molecular behavior of one of the key proteins of mussels involved in underwater adhesion and may inspire new applications of bioadhesives using recombinant mussel foot proteins.

Mussel adhesive protein fused with VE-cadherin domain specifically triggers endothelial cell adhesion

Endothelium is the only known completely non-thrombogenic material. In the present study, a strategy to mimic the adhesive interactions of endothelial cells (ECs) to alter the vascular microenvironment was established and applied to directing the behaviour of cells. To facilitate the regeneration of a functional endothelium in vascular lesions, we designed a recombinant mussel foot protein (Mfp-5) fused with the VE-cadherin extracellular domain EC1-2, termed VE-M. Surface coating analysis showed that recombinant VE-M successfully formed a coating on substrate materials with uniform nanorods, low roughness, and sufficient hydrophilicity. We then evaluated the effects of VE-M on the adhesion of ECs and the capture of endothelial progenitor cells (EPCs). The result demonstrated that VE-M efficiently promoted the adhesion of ECs and EPCs. The number of ECs and EPCs on VE-M was 5.5- and 1.8-fold higher, respectively, than that on bare 316L SS under static conditions, whereas there was no significant difference in the number of captured smooth muscle cells (SMCs) between VE-M and other substrates. In addition, the number of EPCs captured by VE-M was approximately four times higher than that captured by 316L SS under dynamic conditions. In particular, the result of the neutralization test indicated that VE-M specifically triggered ECs' adhesion via the interaction of VE-cadherin EC1-2. Further investigation showed that VE-M significantly increased the levels of endogenous VE-cadherin in HUVECs as well as the endothelial eNOS content, with little or no endothelial inflammation. Our results showed that VE-M could be a promising biomimetic modification for accelerating endothelialization and vascularization in tissue engineering.

Bioinspired Underwater Adhesives by Using the Supramolecular Toolbox

Nature has developed protein-based adhesives whose underwater performance has attracted much research attention over the last few decades. The adhesive proteins are rich in catechols combined with amphiphilic and ionic features. This combination of features constitutes a supramolecular toolbox, to provide stimuli-responsive processing of the adhesive, to secure strong adhesion to a variety of surfaces, and to control the cohesive properties of the material. Here, the versatile interactions used in adhesives secreted by sandcastle worms and mussels are explored. These biological principles are then put in a broader perspective, and synthetic adhesive systems that are based on different types of supramolecular interactions are summarized. The variety and combinations of interactions that can be used in the design of new adhesive systems are highlighted.

A tyrosinase, mTyr-CNK, that is functionally available as a monophenol monooxygenase

Tyrosinase efficiently catalyzes the ortho-hydroxylation of monophenols and the oxidation of diphenols without any additional cofactors. Although it is of significant interest for the biosynthesis of catechol derivatives, the rapid catechol oxidase activity and inactivation of tyrosinase have hampered its practical utilization as a monophenol monooxygenase. Here, we prepared a functional tyrosinase that exhibited a distinguished monophenolase/diphenolase activity ratio (V_max mono/ V_max di = 3.83) and enhanced catalytic efficiency against _L-tyrosine (k_cat = 3.33 ± 0.18 s⁻¹, K_m = 2.12 ± 0.14 mM at 20 °C and pH 6.0). This enzyme was still highly active in ice water (>80%), and its activity was well conserved below 30 °C. In vitro DOPA modification, with a remarkably high yield as a monophenol monooxygenase, was achieved by the enzyme taking advantage of these biocatalytic properties. These results demonstrate the strong potential for this enzyme’s use as a monophenol monooxygenase in biomedical and industrial applications.

Diatom-Inspired Silica Nanostructure Coatings with Controllable Microroughness Using an Engineered Mussel Protein Glue to Accelerate Bone Growth on Titanium-Based Implants

Silica nanoparticles (SiNPs) have been utilized to construct bioactive nanostructures comprising surface topographic features and bioactivity that enhances the activity of bone cells onto titanium-based implants. However, there have been no previous attempts to create microrough surfaces based on SiNP nanostructures even though microroughness is established as a characteristic that provides beneficial effects in improving the biomechanical interlocking of titanium implants. Herein, a protein-based SiNP coating is proposed as an osteopromotive surface functionalization approach to create microroughness on titanium implant surfaces. A bioengineered recombinant mussel adhesive protein fused with a silica-precipitating R5 peptide (R5-MAP) enables direct control of the microroughness of the surface through the multilayer assembly of SiNP nanostructures under mild conditions. The assembled SiNP nanostructure significantly enhances the in vitro osteogenic cellular behaviors of preosteoblasts in a roughness-dependent manner and promotes the in vivo bone tissue formation on a titanium implant within a calvarial defect site. Thus, the R5-MAP-based SiNP nanostructure assembly could be practically applied to accelerate bone-tissue growth to improve the stability and prolong the lifetime of medical implantable devices.

Complex coacervates based on recombinant mussel adhesive proteins: their characterization and applications

Complex coacervates are a dense liquid phase of oppositely charged polyions formed by the associative separation of a mixture of polyions. Coacervates have been widely employed in many fields including the pharmaceutical, cosmetic, and food industries due to their intriguing interfacial and bulk material properties. More recently, attempts to develop an effective underwater adhesive have been made using complex coacervates that are based on recombinant mussel adhesive proteins (MAPs) due to the water immiscibility of complex coacervates and the adhesiveness of MAPs. MAP-based complex coacervates contribute to our understanding of the physical nature of complex coacervates and they provide a promising alternative to conventional invasive surgical repairs. Here, this review provides an overview of recombinant MAP-based complex coacervations, with an emphasis on their characterization and the uses of such materials for applications in the fields of biomedicine and tissue engineering.

Natural healing-inspired collagen-targeting surgical protein glue for accelerated scarless skin regeneration

Skin scarring after deep dermal injuries is a major clinical problem due to the current therapies limited to established scars with poor understanding of healing mechanisms. From investigation of aberrations within the extracellular matrix involved in pathophysiologic scarring, it was revealed that one of the main factors responsible for impaired healing is abnormal collagen reorganization. Here, inspired by the fundamental roles of decorin, a collagen-targeting proteoglycan, in collagen remodeling, we created a scar-preventive collagen-targeting glue consisting of a newly designed collagen-binding mussel adhesive protein and a specific glycosaminoglycan. The collagen-targeting glue specifically bound to type I collagen in a dose-dependent manner and regulated the rate and the degree of fibrillogenesis. In a rat skin excisional model, the collagen-targeting glue successfully accelerated initial wound regeneration as defined by effective reepithelialization, neovascularization, and rapid collagen synthesis. Moreover, the improved dermal collagen architecture was demonstrated by uniform size of collagen fibrils, their regular packing, and a restoration of healthy tissue component. Collectively, our natural healing-inspired collagen-targeting glue may be a promising therapeutic option for improving the healing rate with high-quality and effective scar inhibition.

Recent approaches in designing bioadhesive materials inspired by mussel adhesive protein

Marine mussels secret protein-based adhesives, which enable them to anchor to various surfaces in a saline, intertidal zone. Mussel foot proteins (Mfps) contain a large abundance of a unique, catecholic amino acid, Dopa, in their protein sequences. Catechol offers robust and durable adhesion to various substrate surfaces and contributes to the curing of the adhesive plaques. In this article, we review the unique features and the key functionalities of Mfps, catechol chemistry, and strategies for preparing catechol-functionalized polymers. Specifically, we reviewed recent findings on the contributions of various features of Mfps on interfacial binding, which include coacervate formation, surface drying properties, control of the oxidation state of catechol, among other features. We also summarized recent developments in designing advanced biomimetic materials including coacervate-forming adhesives, mechanically improved nano- and micro-composite adhesive hydrogels, as well as smart and self-healing materials. Finally, we review the applications of catechol-functionalized materials for the use as biomedical adhesives, therapeutic applications, and antifouling coatings. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 9-33.

Elastic sealants for surgical applications

Sealants have emerged as promising candidates for replacing sutures and staples to prevent air and liquid leakages during and after the surgeries. Their physical properties and adhesion strength to seal the wound area without limiting the tissue movement and function are key factors in their successful implementation in clinical practice. In this contribution, the advances in the development of elastic sealants formed from synthetic and natural materials are critically reviewed and their shortcomings are pointed out. In addition, we highlight the applications in which elasticity of the sealant is critical and outline the limitations of the currently available sealants. This review will provide insights for the development of novel bioadhesives with advanced functionality for surgical applications.

Rapidly light-activated surgical protein glue inspired by mussel adhesion and insect structural crosslinking

Currently approved surgical tissue glues do not satisfy the requirements for ideal bioadhesives due to limited adhesion in wet conditions and severe cytotoxicity. Herein, we report a new light-activated, mussel protein-based bioadhesive (LAMBA) inspired by mussel adhesion and insect dityrosine crosslinking chemistry. LAMBA exhibited substantially stronger bulk wet tissue adhesion than commercially available fibrin glue and good biocompatibility in both in vitro and in vivo studies. Besides, the easily tunable, light-activated crosslinking enabled an effective on-demand wound closure and facilitated wound healing. Based on these outstanding properties, LAMBA holds great potential as an ideal surgical tissue glue for diverse medical applications, including sutureless wound closures of skin and internal organs.

Mussel-Inspired Protein Nanoparticles Containing Iron(III)-DOPA Complexes for pH-Responsive Drug Delivery

A novel bioinspired strategy for protein nanoparticle (NP) synthesis to achieve pH-responsive drug release exploits the pH-dependent changes in the coordination stoichiometry of iron(III)-3,4-dihydroxyphenylalanine (DOPA) complexes, which play a major cross-linking role in mussel byssal threads. Doxorubicin-loaded polymeric NPs that are based on Fe(III)-DOPA complexation were thus synthesized with a DOPA-modified recombinant mussel adhesive protein through a co-electrospraying process. The release of doxorubicin was found to be predominantly governed by a change in the structure of the Fe(III)-DOPA complexes induced by an acidic pH value. It was also demonstrated that the fabricated NPs exhibited effective cytotoxicity towards cancer cells through efficient cellular uptake and cytosolic release. Therefore, it is anticipated that Fe(III)-DOPA complexation can be successfully utilized as a new design principle for pH-responsive NPs for diverse controlled drug-delivery applications.

Ionically cross-linked poly(allylamine) as a stimulus-responsive underwater adhesive: ionic strength and pH effects

Gel-like coacervates that adhere to both hydrophilic and hydrophobic substrates under water have recently been prepared by ionically cross-linking poly(allylamine) (PAH) with pyrophosphate (PPi) and tripolyphosphate (TPP). Among the many advantages of these underwater adhesives (which include their simple preparation and low cost) is their ability to dissolve on demand when exposed to high or low pH. To further analyze their stimulus-responsive properties, we have investigated the pH and ionic strength effects on the formation, rheology and adhesion of PAH/PPi and PAH/TPP complexes. The ionic cross-linker concentrations needed to form these adhesives decreased with increasing pH and ionic strength (although the complexes ceased to form when the parent solution pH exceeded ca. 8.5; i.e., the effective pKa of PAH). Once formed, their ionic cross-links were most stable (as inferred from their relaxation times) at near-neutral or slightly alkaline pH values (of roughly 6.5-9) and at low ionic strengths. The decrease in ionic cross-link stability within complexes prepared at other pH values and at elevated (150-300 mM) NaCl concentrations diminished both the strength and longevity of adhesion (although, under most conditions tested, the short-term tensile adhesion strengths remained above 10(5) Pa). Additionally, the sensitivity of PAH/PPi and PAH/TPP complexes to ionic strength was demonstrated as a potential route to injectable adhesive design (where spontaneous adhesive formation was triggered via injection of low-viscosity, colloidal PAH/TPP dispersions into phosphate buffered saline). Thus, while the sensitivity of ionically cross-linked PAH networks to pH and ionic strength can weaken their adhesion, it can also impart them with additional functionality, such as minimally invasive, injectable delivery, and ability to form and dissolve their bonds on demand.

Mussel-inspired adhesive protein-based electrospun nanofibers reinforced by Fe(iii)–DOPA complexation

The mechanical properties of mussel-inspired electrospun nanofibers were reinforced by the Fe(III)–DOPA complex in the mussel adhesive protein, a key component for a naturally occurring high performance mussel protective coating.

Bioengineered mussel glue incorporated with a cell recognition motif as an osteostimulating bone adhesive for titanium implants

An engineered mussel glue MAP-RGD can be successfully used as a novel functional osteostimulating bone adhesive for titanium implants through improved osteoblastic cell behaviors, blood responses, and eventually enhanced bone regeneration.

Engineered mussel bioglue as a functional osteoinductive binder for grafting of bone substitute particles to accelerate in vivo bone regeneration

Engineered mussel bioglue is a promising functional binder for acceleration of bone substitute-assisted bone regeneration with enhanced osteoconductivity and osteoinductivity.

Surface-independent antibacterial coating using silver nanoparticle-generating engineered mussel glue

During implant surgeries, antibacterial agents are needed to prevent bacterial infections, which can cause the formation of biofilms between implanted materials and tissue. Mussel adhesive proteins (MAPs) derived from marine mussels are bioadhesives that show strong adhesion and coating ability on various surfaces even in wet environment. Here, we proposed a novel surface-independent antibacterial coating strategy based on the fusion of MAP to a silver-binding peptide, which can synthesize silver nanoparticles having broad antibacterial activity. This sticky recombinant fusion protein enabled the efficient coating on target surface and the easy generation of silver nanoparticles on the coated-surface under mild condition. The biosynthesized silver nanoparticles showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria and also revealed good cytocompatibility with mammalian cells. In this coating strategy, MAP-silver binding peptide fusion proteins provide hybrid environment incorporating inorganic silver nanoparticle and simultaneously mediate the interaction of silver nanoparticle with surroundings. Moreover, the silver nanoparticles were fully synthesized on various surfaces including metal, plastic, and glass by a simple, surface-independent coating manner, and they were also successfully synthesized on a nanofiber surface fabricated by electrospinning of the fusion protein. Thus, this facile surface-independent silver nanoparticle-generating antibacterial coating has great potential to be used for the prevention of bacterial infection in diverse biomedical fields.

M13 bacteriophage displaying DOPA on surfaces: fabrication of various nanostructured inorganic materials without time-consuming screening processes

M13 bacteriophage (phage) was engineered for the use as a versatile template for preparing various nanostructured materials via genetic engineering coupled to enzymatic chemical conversions. First, we engineered the M13 phage to display TyrGluGluGlu (YEEE) on the pVIII coat protein and then enzymatically converted the Tyr residue to 3,4-dihydroxyl-l-phenylalanine (DOPA). The DOPA-displayed M13 phage could perform two functions: assembly and nucleation. The engineered phage assembles various noble metals, metal oxides, and semiconducting nanoparticles into one-dimensional arrays. Furthermore, the DOPA-displayed phage triggered the nucleation and growth of gold, silver, platinum, bimetallic cobalt-platinum, and bimetallic iron-platinum nanowires. This versatile phage template enables rapid preparation of phage-based prototype devices by eliminating the screening process, thus reducing effort and time.

Adhesive proteins of stalked and acorn barnacles display homology with low sequence similarities

Barnacle adhesion underwater is an important phenomenon to understand for the prevention of biofouling and potential biotechnological innovations, yet so far, identifying what makes barnacle glue proteins ‘sticky’ has proved elusive. Examination of a broad range of species within the barnacles may be instructive to identify conserved adhesive domains. We add to extensive information from the acorn barnacles (order Sessilia) by providing the first protein analysis of a stalked barnacle adhesive, Lepas anatifera (order Lepadiformes). It was possible to separate the L. anatifera adhesive into at least 10 protein bands using SDS-PAGE. Intense bands were present at approximately 30, 70, 90 and 110 kilodaltons (kDa). Mass spectrometry for protein identification was followed by de novo sequencing which detected 52 peptides of 7–16 amino acids in length. None of the peptides matched published or unpublished transcriptome sequences, but some amino acid sequence similarity was apparent between L. anatifera and closely-related Dosima fascicularis. Antibodies against two acorn barnacle proteins (ab-cp-52k and ab-cp-68k) showed cross-reactivity in the adhesive glands of L. anatifera. We also analysed the similarity of adhesive proteins across several barnacle taxa, including Pollicipes pollicipes (a stalked barnacle in the order Scalpelliformes). Sequence alignment of published expressed sequence tags clearly indicated that P. pollicipes possesses homologues for the 19 kDa and 100 kDa proteins in acorn barnacles. Homology aside, sequence similarity in amino acid and gene sequences tended to decline as taxonomic distance increased, with minimum similarities of 18–26%, depending on the gene. The results indicate that some adhesive proteins (e.g. 100 kDa) are more conserved within barnacles than others (20 kDa).