Mechanistic insights into the adsorption and bioactivity of fibronectin on surfaces with varying chemistries by a combination of experimental strategies and molecular simulations

Proliferation and differentiation of human dental pulp stem cells on phosphorylated cellulose nanofiber scaffolds

Human dental pulp stem cells (hDPSCs) are a promising cell source for tooth regeneration therapies. However, conventional culture scaffold materials are often animal-derived, leading to immunogenicity concerns and limited availability. In this study, we explored phosphorylated cellulose nanofibers (P-CNFs), which have a fine fiber morphology and phosphate groups, as a novel scaffold material for cell culture. Immortalized hDPSCs were cultured on P-CNF scaffolds with different phosphate contents (0-1.42 mmol g-1) prepared by varying the molar ratio of urea and diammonium hydrogen phosphate and the reaction time. Cells cultured on unmodified CNFs exhibited poor adhesion and formed spheroids, indicating low bioadaptability. In contrast, P-CNF scaffolds with moderate phosphate content (0.54-0.78 mmol g-1) significantly improved cell adhesion; further increases in phosphate content decreased cell adhesion, indicating a strong dependence on phosphate content. Intriguingly, even in the absence of differentiation inducers, hDPSCs on P-CNF scaffolds with an optimal phosphate content of 0.78 mmol g-1 showed equal or higher expression of hard tissue marker genes compared to collagen scaffolds with differentiation inducers, suggesting that P-CNFs can directly promote hard tissue differentiation. These findings highlight plant-derived, animal-free P-CNFs as a promising biomaterial for advanced dental tissue engineering.

Molecular dynamics simulation in tissue engineering

Introduction

In tissue engineering, the interaction among three primary elements, namely cells, material scaffolds, and stimuli, plays a pivotal role in determining the fate of cells and the formation of new tissue. Understanding the characteristics of these components and their interplay through various methodologies can significantly enhance the efficiency of the designed tissue engineering system. In silico methods, such as molecular dynamics (MD) simulation, use mathematical calculations to investigate molecular properties and can overcome the limitations of laboratory methods in delivering adequate molecular-level information.

Methods

The studies that used molecular dynamics simulation, either alone or in combination with other techniques, have been reviewed in this paper.

Results

The review explores the use of molecular dynamics simulations in studying substrate formation mechanism and its optimization. It highlights MD simulations' role in predicting biomolecule binding strength, understanding substrate properties' impact on biological activity, and factors influencing cell attachment and proliferation. Despite limited studies, MD simulations are considered a reliable tool for identifying ideal substrates for cell proliferation. The review also touches on MD simulations' contribution to cell differentiation studies, emphasizing their role in designing engineered extracellular matrix for desired cell fates.

Conclusion

Molecular dynamics simulation as a non-laboratory tool has many capabilities in providing basic and practical information about the behavior of the molecular components of the cell as well as the interaction of the cell and its components with the surrounding environment. Using this information along with other information obtained from laboratory tools can ultimately lead to the advancement of tissue engineering through the development of more appropriate and efficient methods.

Novel role of homogalacturonan region of pectin in disrupting the interaction between fibronectin and integrin β1

Pectin interacts with fibronectin (FN), a modular protein in the extracellular matrix. This interaction is significant as FN plays a pivotal role by binding to the receptor integrin α5β1. However, the molecular mechanism underlying the pectin-FN interaction and its impact on integrin binding remains unknown. In this study, water-soluble pectins (WSPs) were extracted from three different pectin sources and subsequently characterized. These included Citrus WSP, which primarily comprises the homogalacturonan region, and Kaki and Yuzu WSPs, both of which are rich in rhamnogalacturonan regions. We investigated the molecular interactions between these WSPs and two FN fragments, Anastellin and RetroNectin, using surface plasmon resonance analysis. Citrus WSP exhibited a notable binding affinity to FN, with a dissociation constant (KD) of approximately 10-7 M. In contrast, Kaki and Yuzu WSPs displayed comparatively weaker or negligible binding affinities. The binding reactivity of Citrus WSP with FN was notably diminished following the enzymatic removal of its methyl-ester groups. Additionally, Citrus WSP disrupted the binding of integrin β1 to RetroNectin without altering the affinity, despite its minimal direct binding to integrin itself. This study furthers our understanding of the intricate pectin-FN interaction and sheds light on their potential physiological relevance and impact on cellular responses.

Hierarchical Composite Scaffold with Deferoxamine Delivery System to Promote Bone Regeneration via Optimizing Angiogenesis

A bone defect refers to the loss of bone tissue caused by trauma or lesion. Bone defects result in high morbidity and deformity rates worldwide. Autologous bone grafting has been widely applied in clinics as the gold standard of treatment; however, it has limitations. Hence, bone tissue engineering has been proposed and developed as a novel therapeutic strategy for treating bone defects. Rapid and effective vascularization is essential for bone regeneration. In this study, a hierarchical composite scaffold with deferoxamine (DFO) delivery system, DFO@GMs-pDA/PCL-HNTs (DGPN), is developed, focusing on vascularized bone regeneration. The hierarchical structure of DGPN imitates the microstructure of natural bone and interacts with the local extracellular matrix, facilitating cell adhesion and proliferation. The addition of 1 wt% of halloysite nanotubes (HNTs) improves the material properties. Hydrophilic and functional groups conferred by polydopamine (pDA) modifications strengthen the scaffold bioactivity. Gelatin microspheres (GMs) protect the pharmacological activity of DFO, achieving local application and sustained release for 7 days. DFO effectively promotes angiogenesis by activating the signaling pathway of hypoxia inducible factor-1 α. In addition, DFO synergizes with HNTs to promote osteogenic differentiation and matrix mineralization. These results indicate that DGPN promotes bone regeneration and accelerates cranial defect healing.

An antibacterial nanoclay- and chitosan-based quad composite with controlled drug release for infected skin wound healing

Microbial infections of surgical sites and other wounds represent a major impediment for patients. Multifunctional low-cost dressings promoting tissue reparation while preventing infections are of great interest to medical professionals. Here, clay-based laponite nanodiscs (LAP) were loaded with the antibacterial drug kanamycin (KANA) before being embedded into a poly(lactic-co-glycolic acid) (PLGA) membrane and coated with the biopolymer chitosan (CS). Results indicated that these biocompatible materials combined the excellent capacity of LAP for controlled drug release with the mechanical robustness of PLGA and the antibacterial properties of CS as well as its hydrophilicity to form a composite highly suitable as an infection-preventing wound dressing. In vitro, PLGA/LAP/KANA/CS released drugs in a sustainable manner over 30 d, completely inhibited the growth of infectious bacteria, prompted the adhesion fibroblasts, and accelerated their proliferation 1.3 times. In vivo, the composite enabled the fast healing of infected full-thickness skin wounds with a 96.19 % contraction after 14 d. During the healing process, PLGA/LAP/KANA/CS stimulated re-epithelization, reduced inflammation, and promoted both angiogenesis and the formation of dense collagen fibers with an excellent final collagen volume ratio of 89.27 %. Thus, multifunctional PLGA/LAP/KANA/CS made of low-cost components demonstrated its potential for the treatment of infected skin wounds.

Accelerated Bone Regeneration on the Metal Surface through Controllable Surface Potential

Surface potential is rarely investigated as an independent factor in influencing tissue regeneration on the metal surface. In this work, the surface potential on the titanium (Ti) surface was designed to be tailored and adjusted independently, which arises from the ferroelectricity and piezoelectricity of poled poly(vinylidene fluoride-trifluoroethylene) (PVTF). Notably, it is found that such controllable surface potential on the metal surface significantly promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro as well as bone regeneration in vivo. In addition, the intracellular calcium ion (Ca2+) concentration measurement further proves that such controllable surface potential on the metal surface could activate the transmembrane calcium channels and allow the influx of extracellular Ca2+ into the cytoplasm. That might be the reason for improved osteogenic differentiation of BMSCs and bone regeneration. These findings reveal the potential of the metal surface with improved bioactivity for stimulation of osteogenesis and show great prospects for fabricable implantable medical devices with adjustable surface potential.

Microfluidic synthesis of fibronectin-coated polydopamine nanocomplexes for self-supplementing tumor microenvironment regulation and MR imaging-guided chemo-chemodynamic-immune therapy

Development of nanomedicines to overcome the hindrances of tumor microenvironment (TME) for tumor theranostics with alleviated side effects remains challenging. We report here a microfluidic synthesis of artesunate (ART)-loaded polydopamine (PDA)/iron (Fe) nanocomplexes (NCs) coated with fibronectin (FN). The created multifunctional Fe-PDA@ART/FN NCs (FDRF NCs) with a mean size of 161.0 ​nm exhibit desired colloidal stability, monodispersity, r₁ relaxivity (4.96 ​mM^-1s^-1), and biocompatibility. The co-delivery of the Fe²⁺ and ART enables enhanced chemodynamic therapy (CDT) through improved intracellular reactive oxygen species generation via a cycling reaction between Fe³⁺ and Fe²⁺ caused by the Fe³⁺-mediated glutathione oxidation and Fe²⁺-mediated ART reduction/Fenton reaction for self-supplementing TME regulation. Likewise, the combination of ART-mediated chemotherapy and the Fe²⁺/ART-regulated enhanced CDT enables noticeable immunogenic cell death, which can be collaborated with antibody-mediated immune checkpoint blockade to exert immunotherapy having significant antitumor immunity. The combined therapy improves the efficacy of primary tumor therapy and tumor metastasis inhibition by virtue of FN-mediated specific targeting of FDRF NCs to tumors with highly expressed α_vβ₃ integrin and can be guided through the Fe(III)-rendered magnetic resonance (MR) imaging. The developed FDRF NCs may be regarded as an advanced nanomedicine formulation for chemo-chemodynamic-immune therapy of different tumor types under MR imaging guidance.

Tissue engineering modalities in skeletal muscles: focus on angiogenesis and immunomodulation properties

Muscular diseases and injuries are challenging issues in human medicine, resulting in physical disability. The advent of tissue engineering approaches has paved the way for the restoration and regeneration of injured muscle tissues along with available conventional therapies. Despite recent advances in the fabrication, synthesis, and application of hydrogels in terms of muscle tissue, there is a long way to find appropriate hydrogel types in patients with congenital and/or acquired musculoskeletal injuries. Regarding specific muscular tissue microenvironments, the applied hydrogels should provide a suitable platform for the activation of endogenous reparative mechanisms and concurrently deliver transplanting cells and therapeutics into the injured sites. Here, we aimed to highlight recent advances in muscle tissue engineering with a focus on recent strategies related to the regulation of vascularization and immune system response at the site of injury.

Bone ECM-inspired biomineralization chitin whisker liquid crystal hydrogels for bone regeneration

As a particular cell niche, natural bone extracellular matrix (ECM) is an organic-inorganic composite material formed by mineralization of liquid crystal (LC) collagen fiber network. However, designing bone repair materials that highly imitate the LC characteristic and composite components of natural bone ECM is a great challenge. Here, we report a novel kind of bone ECM-inspired biomineralization chitin whisker LC hydrogels. First, photocurable chitin whisker LC hydrogels with bone ECM-like chiral nematic LC state and viscoelasticity are created. Next, biomineralization, guided by LC hydrogels, is carried out to truly mimic the mineralization process of natural bone, so as to obtain the organic-inorganic composite materials with bone ECM-like microenvironment. The chitin whisker LC hydrogels exhibit superior biomineralization, protein adsorption and osteogenesis ability, more importantly, LC hydrogel with negatively charged -COOH groups is more conducive to biomineralization and shows more desirable osteogenic activity than that with positively charged -NH₂ groups. Notably, compared with the pristine LC hydrogels, the biomineralization LC hydrogels display more favorable osteogenesis ability due to their bone ECM-like LC texture and bone-like hydroxyapatite. This study opens an avenue toward the design of bone ECM-inspired biomineralization chitin whisker LC hydrogels for bone regeneration.

Influence of PHA Substrate Surface Characteristics on the Functional State of Endothelial Cells

The needs of modern regenerative medicine for biodegradable polymers are wide and varied. Restoration of the viability of the vascular tree is one of the most important components of the preservation of the usefulness of organs and tissues. The creation of vascular implants compatible with blood is an important task of vascular bioengineering. The function of the endothelial layer of the vessel, being largely responsible for the development of thrombotic complications, is of great importance for hemocompatibility. The development of surfaces with specific characteristics of biomaterials that are used in vascular technologies is one of the solutions for their correct endothelialization. Linear polyhydroxyalkanoates (PHAs) are biodegradable structural polymeric materials suitable for obtaining various types of implants and tissue engineering, having a wide range of structural and physicomechanical properties. The use of PHA of various monomeric compositions in endothelial cultivation makes it possible to evaluate the influence of material properties, especially surface characteristics, on the functional state of cells. It has been established that PHA samples with the inclusion of 3-hydroxyhexanoate have optimal characteristics for the formation of a human umbilical vein endothelial cell, HUVEC, monolayer in terms of cell morphology as well as the levels of expression of vinculin and VE-cadherin. The obtained results provide a rationale for the use of PHA copolymers as materials for direct contact with the endothelium in vascular implants.

Plasma polymerized bio-interface directs fibronectin adsorption and functionalization to enhance "epithelial barrier structure" formation via FN-ITG β1-FAK-mTOR signaling cascade

BACKGROUND

Transepithelial medical devices are increasing utilized in clinical practices. However, the damage of continuous natural epithelial barrier has become a major risk factor for the failure of epithelium-penetrating implants. How to increase the "epithelial barrier structures" (focal adhesions, hemidesmosomes, etc.) becomes one key research aim in overcoming this difficulty. Directly targeting the in situ "epithelial barrier structures" related proteins (such as fibronectin) absorption and functionalization can be a promising way to enhance interface-epithelial integration.

METHODS

Herein, we fabricated three plasma polymerized bio-interfaces possessing controllable surface chemistry. Their capacity to adsorb and functionalize fibronectin (FN) from serum protein was compared by Liquid Chromatography-Tandem Mass Spectrometry. The underlying mechanisms were revealed by molecular dynamics simulation. The response of gingival epithelial cells regarding the formation of epithelial barrier structures was tested.

RESULTS

Plasma polymerized surfaces successfully directed distinguished protein adsorption profiles from serum protein pool, in which plasma polymerized allylamine (ppAA) surface favored adsorbing adhesion related proteins and could promote FN absorption and functionalization via electrostatic interactions and hydrogen bonds, thus subsequently activating the ITG β1-FAK-mTOR signaling and promoting gingival epithelial cells adhesion.

CONCLUSION

This study offers an effective perspective to overcome the current dilemma of the inferior interface-epithelial integration by in situ protein absorption and functionalization, which may advance the development of functional transepithelial biointerfaces. Tuning the surface chemistry by plasma polymerization can control the adsorption of fibronectin and functionalize it by exposing functional protein domains. The functionalized fibronectin can bind to human gingival epithelial cell membrane integrins to activate epithelial barrier structure related signaling pathway, which eventually enhances the formation of epithelial barrier structure.

Effects of Substitution Ratios of Zinc-Substituted Hydroxyapatite on Adsorption and Desorption Behaviors of Bone Morphogenetic Protein-2

Understanding interactions between bone morphogenetic proteins (BMPs) and biomaterials is of great significance in preserving the structure and bioactivity of BMPs when utilized in clinical applications. Currently, bone morphogenetic protein-2 (BMP-2) is one of the most important growth factors in bone tissue engineering; however, atomistic interactions between BMP-2 and zinc-substituted hydroxyapatite (Zn-HAP, commonly used in artificial bone implants) have not been well clarified until now. Thus, in this work, the interaction energies, binding/debinding states, and molecular structures of BMP-2 upon a series of Zn-HAP surfaces (Zn-HAPs, 1 at%, 2.5 at%, 5 at%, and 10 at% substitution) were investigated by hybrid molecular dynamics (MD) and steered molecular dynamics (SMD) simulations. Meanwhile, cellular studies including alkaline phosphatase (ALP) activity and reverse transcription-polymerase chain reaction (RT-PCR) assay were performed to verify the theoretical modeling findings. It was found that, compared to pure HAP, Zn-HAPs exhibited a higher binding affinity of BMP-2 at the adsorption process; meanwhile, the detachment of BMP-2 upon Zn-HAPs was more difficult at the desorption process. In addition, molecular structures of BMP-2 could be well stabilized upon Zn-HAPs, especially for Zn10-HAP (with a 10 at% substitution), which showed both the higher stability of cystine-knots and less change in the secondary structures of BMP-2 than those upon HAP. Cellular studies confirmed that higher ALP activity and osteogenic marker gene expression were achieved upon BMP-2/Zn-HAPs than those upon BMP-2/HAP. These findings verified that Zn-HAPs favor the adsorption of BMP-2 and leverage the bioactivity of BMP-2. Together, this work clarified the interaction mechanisms between BMP-2 and Zn-HAPs at the atom level, which could provide new molecular-level insights into the design of BMP-2-loaded biomaterials for bone tissue engineering.

Biochip Surfaces Containing Recombinant Cell-Binding Domains of Fibronectin

Surface immobilization and characterization of the functional activity of fibronectin (Fn) type-III domains are reported. The domains FnIII9-10 or FnIII10 containing the RGD loop and PHSRN synergy site were recombinantly produced and covalently bound to chemically activated PEG methacrylate (MA) hydrogel coatings by microcontact printing. Such fabricated biochip surfaces were 6 mm in diameter and consisted of 190 µm wide protein stripes separated by 200 µm spacing. They were analyzed by imaging null ellipsometry, atomic force microscopy and fluorescence microscopy. Also, the coatings were tested in human foreskin fibroblast and HeLa cultures for at least 96 h, thus evaluating their suitability for controlled cell adhesion and proliferation. However, while HeLa cultures were equally well responsive to the FnIII9-10, FnIII10 and Fn surfaces, the fibroblasts displayed lower cell and lower focal adhesion areas, as well as lower proliferation rates on the Fn fragment surfaces as compared to Fn. Nevertheless, full functional activity of the fibroblasts was confirmed by immunostaining of Fn produced by the cells adherent on the biochip surfaces. The observed interaction differences that were either cell type or surface composition-dependent demonstrate the potential use of specifically engineered Fn and other ECM protein-derived domains in biochip architectures.

Simultaneous incorporation of gallium oxide and tantalum microparticles into micro-arc oxidation coating of titanium possessing antibacterial effect and stimulating cellular response

Orthopedic implants with both osteogenesis and antibacterial functions are particularly promising for bone repair and substitutes. In this study, a micro-arc oxidation (MAO) coating containing titanium dioxide (TiO₂), gallium oxide (Ga₂O₃) and tantalum oxide (Ta₂O₅) on the titanium surface (MGT) was fabricated by dispersing Ga₂O₃ and Ta microparticles in the electrolyte. The results showed that the simultaneous incorporation of Ga₂O₃ and Ta microparticles into the MAO coating resulted in optimized surface performance (e.g., micro-topography, roughness, wettability, surface energy, and protein absorption) of MGT compared with pure titanium (pTi). In addition, MGT exhibited outstanding corrosion resistance owing to the presence of both Ga₂O₃ and Ta microparticles, which exhibit excellent corrosion resistance and their microparticles were incorporated into the micropores of the coating. Moreover, MGT with good cytocompatibility and optimized surface resulted in improved cellular responses (e.g., proliferation and osteogenic differentiation) of rat bone mesenchymal stem cells, which was attributed to Ta microparticles with outstanding osteogenic bioactivity. Furthermore, the excellent antibacterial effect of MGT was attributed to the slow release of Ga³⁺ from the coating. Thus, the simultaneous incorporation of Ga₂O₃ and Ta microparticles into the MAO coating of MGT exhibited excellent cytocompatibility, osteogenic bioactivity, antibacterial functions, and corrosion resistance, suggesting that MGT possesses great potential for bone repair applications.

Fibronectin-Coated Metal-Phenolic Networks for Cooperative Tumor Chemo-/Chemodynamic/Immune Therapy via Enhanced Ferroptosis-Mediated Immunogenic Cell Death

The development of nanomedicine formulations to overcome the disadvantages of traditional chemotherapeutic drugs and integrate cooperative theranostic modes still remains challenging. Herein, we report the facile construction of a multifunctional theranostic nanoplatform based on doxorubicin (DOX)-loaded tannic acid (TA)-iron (Fe) networks (for short, TAF) coated with fibronectin (FN) for combination tumor chemo-/chemodynamic/immune therapy under the guidance of magnetic resonance (MR) imaging. We show that the DOX-TAF@FN nanocomplexes created through in situ coordination of TA and Fe(III) and physical coating with FN have a mean particle size of 45.0 nm, are stable, and can release both DOX and Fe in a pH-dependent manner. Due to the coexistence of the TAF network and DOX, significant immunogenic cell death can be caused through enhanced ferroptosis of cancer cells via cooperative Fe-based chemodynamic therapy and DOX chemotherapy. Through further treatment with programmed cell death ligand 1 antibody for an immune checkpoint blockade, the tumor treatment efficacy and the associated immune response can be further enhanced. Meanwhile, with FN-mediated targeting, the DOX-TAF@FN platform can specifically target tumor cells with high expression of α_vβ₃ integrin. Finally, the TAF network also enables the DOX-TAF@FN to have an r₁ relaxivity of 6.1 mM^-1 s^-1 for T₁-weighted MR imaging of tumors. The developed DOX-TAF@FN nanocomplexes may represent an updated multifunctional nanosystem with simple compositions for cooperative MR imaging-guided targeted chemo-/chemodynamic/immune therapy of tumors.

Effect of Aminosilane Coupling Agent-Modified Nano-SiO2 Particles on Thermodynamic Properties of Epoxy Resin Composites

From the perspective of improving the thermodynamic properties of epoxy resin, it has become the focus of research to enhance the operational stability of GIS (Gas Insulated Substation) basin insulators for UHV (Ultra-High Voltage) equipment. In this paper, three aminosilane coupling agents with different chain lengths, (3-Aminopropyl)trimethoxysilane (KH550), Aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) and 3-[2-(2-Aminoethylamino)ethylamino]propyl-trimethoxysilane (TAPS), were used to modify nano-SiO2 and doped into epoxy resin, respectively, using a combination of experimental and molecular dynamics simulations. The experimental results showed that the surface-grafted KH792 model of nano-SiO2 exhibited the most significant improvement in thermal properties compared with the undoped nanoparticle model. The storage modulus increased by 276 MPa and the Tg increased by 61 K. The simulation results also showed that the mechanical properties of the nano-SiO2 surface-grafted KH792 model were about 3 times higher than that of the undoped nanoparticle model, the Tg increased by 36.5 K, and the thermal conductivity increased by 24.5%.