Single-Chain Atomic Crystals as Extracellular Matrix-Mimicking Material with Exceptional Biocompatibility and Bioactivity

Peptide-Assembled Single-Chain Atomic Crystal Enhances Pluripotent Stem Cell Differentiation to Neurons

Nanomaterials hybridized with biological components have widespread applications. among many candidates, peptides are attractive in that their peptide sequences can self-assemble with the surface of target materials with high specificity without perturbing the intrinsic properties of nanomaterials. Here, a 1D hybrid nanomaterial was developed through self-assembly of a designed peptide. A hexagonal coiled-coil motif geometrically matched to the diameter of the inorganic nanomaterial was fabricated, whose hydrophobic surface was wrapped along the axis of the hydrophobic core of the coiled coil. Our morphological and spectroscopic analyses revealed rod-shaped, homogeneous peptide-inorganic nanomaterial complexes. Culturing embryonic stem cells on surfaces coated with this peptide-assembled single-chain atomic crystal increased the growth and adhesion of the embryonic stem cells. The hybridized nanomaterial also served as an ECM for brain organoids, accelerating the maturation of neurons. New methods to fabricate hybrid materials through peptide assembly can be applied.

Bioessential Inorganic Molecular Wire-Reinforced 3D-Printed Hydrogel Scaffold for Enhanced Bone Regeneration

Materials with physicochemical properties and biological activities similar to those of the natural extracellular matrix are in high demand in tissue engineering. In particular, Mo₃ Se₃ ^- inorganic molecular wire (IMW) is a promising material composed of bioessential minerals and possess nanometer-scale diameters, negatively charged surfaces, physical flexibility, and nanotopography characteristics, which are essential for interactions with cell membrane proteins. Here, an implantable 3D Mo₃ Se₃ ^- IMW enhanced gelatin-GMA/silk-GMA hydrogel (IMW-GS hydrogel) is developed for osteogenesis and bone formation, followed by biological evaluations. The mechanical properties of the 3D printed IMW-GS hydrogel are improved by noncovalent interactions between the Mo₃ Se₃ ^- IMWs and the positively charged residues of the gelatin molecules. Long-term biocompatibility with primary human osteoblast cells (HOBs) is confirmed using the IMW-GS hydrogel. The proliferation, osteogenic gene expression, collagen accumulation, and mineralization of HOBs improve remarkably with the IMW-GS hydrogel. In in vivo evaluations, the IMW-GS hydrogel implantation exhibits a significantly improved new bone regeneration of 87.8 ± 5.9% (p < 0.05) for 8 weeks, which is higher than that from the gelatin-GMA/silk-GMA hydrogel without Mo₃ Se₃ ^- IMW. These results support a new improved strategy with in vitro and in vivo performance of 3D IMW enhanced scaffolds in tissue engineering.

Organic Dispersion of Mo3Se3- Single-Chain Atomic Crystals Using Surface Modification Methods

In this study, single-chain atomic crystals (SCACs), Mo₃Se₃^-, which can be uniformly dispersed, with an atomically thin diameter of ∼0.6 nm were modified to disperse in an organic solvent. Various surfactants were chosen to provide steric hindrance to aqueous-dispersed Mo₃Se₃^- by modifying the surface of Mo₃Se₃^-. The organic dispersions of surface-modified Mo₃Se₃^- SCACs in nonpolar solvent (toluene, benzene, and chloroform) were stable with a uniform diameter of 2 nm, and they have enhanced stability from oxidation (>10 days). With the surfactants that have a polystyrene tail group (PS-NH₂), the surface-modified Mo₃Se₃^- SCAC showed high compatibility with a polystyrene polymer matrix. Using the surface-modified Mo₃Se₃^- SCAC, a homogeneous Mo₃Se₃^-/polystyrene/toluene organogel was prepared. More importantly, the Mo₃Se₃^-/polystyrene organogel exhibits significantly enhanced mechanical properties, with the improvement of 202.27% and 279.52% for tensile strength and elongation, respectively, compared with that of the pure organogel. The surface-modified Mo₃Se₃^- had a similar structure with a polymer matrix, and the properties of the polymer can be improved even with a small addition of Mo₃Se₃^-.

Natural bone-mimicking nanopore-incorporated hydroxyapatite scaffolds for enhanced bone tissue regeneration

Background

A considerable number of studies has been carried out to develop alloplastic bone graft materials such as hydroxyapatite (HAP) that mimic the hierarchical structure of natural bones with multiple levels of pores: macro-, micro-, and nanopores. Although nanopores are known to play many essential roles in natural bones, only a few studies have focused on HAPs containing them; none of those studies investigated the functions of nanopores in biological systems.

Method

We developed a simple yet powerful method to introduce nanopores into alloplastic HAP bone graft materials in large quantities by simply pressing HAP nanoparticles and sintering them at a low temperature.

Results

The size of nanopores in HAP scaffolds can be controlled between 16.5 and 30.2 nm by changing the sintering temperature. When nanopores with a size of ~ 30.2 nm, similar to that of nanopores in natural bones, are introduced into HAP scaffolds, the mechanical strength and cell proliferation and differentiation rates are significantly increased. The developed HAP scaffolds containing nanopores (SNPs) are biocompatible, with negligible erythema and inflammatory reactions. In addition, they enhance the bone regeneration when are implanted into a rabbit model. Furthermore, the bone regeneration efficiency of the HAP-based SNP is better than that of a commercially available bone graft material.

Conclusion

Nanopores of HAP scaffolds are very important for improving the bone regeneration efficiency and may be one of the key factors to consider in designing highly efficient next-generation alloplastic bone graft materials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00253-x.

Ultrathin, High-Aspect Ratio, and Free-Standing Magnetic Nanowires by Exfoliation of Ferromagnetic Quasi-One-Dimensional van der Waals Lattices

Driven by numerous discoveries of novel physical properties and integration into functional devices, interest in one-dimensional (1D) magnetic nanostructures has grown tremendously. Traditionally, such structures are accessed with bottom-up techniques, but these require increasing sophistication to allow precise control over crystallinity, branching, aspect ratio, and surface termination, especially when approaching the subnanometer regime in magnetic phases. Here, we show that mechanical exfoliation of bulk quasi-one-dimensional crystals, a method similar to those popularized for two-dimensional van der Waals (vdW) lattices, serves as an efficient top-down method to produce ultrathin freestanding nanowires that are both magnetic and semiconducting. We use CrSbSe₃ as a representative quasi-1D vdW crystal with strong magnetocrystalline anisotropy and show that it can be exfoliated into nanowires with an average cross-section of 10 ± 2.8 nm. The CrSbSe₃ nanowires display reduced Curie-Weiss temperature but higher coercivity and remanence than the bulk phase. The methodology developed here for CrSbSe₃, a representative for a vast class of 1D vdW lattices, serves as a blueprint for investigating confinement effects for 1D materials and accessing functional nanowires that are difficult to produce via traditional bottom-up methods.

Bio-essential Inorganic Molecular Nanowires as a Bioactive Muscle Extracellular-Matrix-Mimicking Material

Many physiochemical properties of the extracellular matrix (ECM) of muscle tissues, such as nanometer scale dimension, nanotopography, negative charge, and elasticity, must be carefully reproduced to fabricate scaffold materials mimicking muscle tissues. Hence, we developed a muscle tissue ECM-mimicking scaffold using Mo₆S₃I₆ inorganic molecular wires (IMWs). Composed of bio-essential elements and having a nanofibrous structure with a diameter of ∼1 nm and a negative surface charge with high stability, Mo₆S₃I₆ IMWs are ideal for mimicking natural ECM molecules. Once Mo₆S₃I₆ IMWs were patterned on a polydimethylsiloxane surface with an elasticity of 1877.1 ± 22.2 kPa, that is, comparable to that of muscle tissues, the proliferation and α-tubulin expression of myoblasts enhanced significantly. Additionally, the repetitive one-dimensional patterns of Mo₆S₃I₆ IMWs induced the alignment and stretching of myoblasts with enhanced α-tubulin expression and differentiation into myocytes. This study demonstrates that Mo₆S₃I₆ IMWs are promising for mimicking the ECM of muscle tissues.

Nanotopography as Artificial Microenvironment for Accurate Visualization of Metastasis Development via Simulation of ECM Dynamics

Metastatic progression is mediated by complex interactions between deregulated extracellular matrix (ECM) and cancer cells and remains a major challenge in cancer management. To investigate the role of ECM dynamics in promoting metastasis development, we developed an artificial microenvironment (AME) platform comprised of nanodot arrays of increasing diameter. Cells cultured on the platform showed increasing signs of mesenchymal-like cell transition as AME diameter increased, suggesting accurate simulation of ECM-mediated gene regulation. Gene expression was analyzed to determine genes significant to transition, which were then used to select appropriate small molecule drugs for time course treatments. Our results suggest that the platform can identify critical target genes as well as possible drug candidates. Overall, the AME platform allows for the study of intricate ECM-induced gene expression trends across metastasis development that would otherwise be difficult to visualize in vivo and may open new avenues toward successful personalized cancer management.

A study on the bio-applicability of aqueous-dispersed van der Waals 1-D material Nb2Se9 using poloxamer

In this research, dispersion of a new type of one-dimensional inorganic material Nb₂Se₉, composed of van der Waals bonds, in aqueous solution for bio-application study were studied. To disperse Nb₂Se₉, which exhibits hydrophobic properties in water, experiments were carried out using a block copolymer (poloxamer) as a dispersant. It was confirmed that PPO, the hydrophobic portion of Poloxamer, was adsorbed onto the surface of Nb₂Se₉, and PEO, the hydrophilic portion, induced steric hinderance to disperse Nb₂Se₉ to a size of 10 nm or less. To confirm the adaptability of muscle cells C2C12 to the dispersed Nb₂Se₉ using poloxamer 188 as dispersant, a MTT assay and a live/dead assay were performed, demonstrating improvement in the viability and proliferation of C2C12 cells.

Hierarchical Surface Texturing of Hydroxyapatite Ceramics: Influence on the Adhesive Bonding Strength of Polymeric Polycaprolactone

The tailored manipulation of ceramic surfaces gained recent interest to optimize the performance and lifetime of composite materials used as implants. In this work, a hierarchical surface texturing of hydroxyapatite (HAp) ceramics was developed to improve the poor adhesive bonding strength in hydroxyapatite and polycaprolactone (HAp/PCL) composites. Four different types of periodic surface morphologies (grooves, cylindric pits, linear waves and Gaussian hills) were realized by a ceramic micro-transfer molding technique in the submillimeter range. A subsequent surface roughening and functionalization on a micron to nanometer scale was obtained by two different etchings with hydrochloric and tartaric acid. An ensuing silane coupling with 3-aminopropyltriethoxysilane (APTES) enhanced the chemical adhesion between the HAp surface and PCL on the nanometer scale by the formation of dipole-dipole interactions and covalent bonds. The adhesive bonding strengths of the individual and combined surface texturings were investigated by performing single-lap compressive shear tests. All individual texturing types (macro, micro and nano) showed significantly improved HAp/PCL interface strengths compared to the non-textured HAp reference, based on an enhanced mechanical, physical and chemical adhesion. The independent effect mechanisms allow the deliberately hierarchical combination of all texturing types without negative influences. The hierarchical surface-textured HAp showed a 6.5 times higher adhesive bonding strength (7.7 ± 1.5 MPa) than the non-textured reference, proving that surface texturing is an attractive method to optimize the component adhesion in composites for potential medical implants.

The Intersection of Mechanotransduction and Regenerative Osteogenic Materials

Mechanical signals play a central role in cell fate determination and differentiation in both physiologic and pathologic circumstances. Such signals may be delivered using materials to generate discrete microenvironments for the purposes of tissue regeneration and have garnered increasing attention in recent years. Unlike the addition of progenitor cells or growth factors, delivery of a microenvironment is particularly attractive in that it may reduce the known untoward consequences of the former two strategies, such as excessive proliferation and potential malignant transformation. Additionally, the ability to spatially modulate the fabrication of materials allows for the creation of multiple microenvironments, particularly attractive for regenerating complex tissues. While many regenerative materials have been developed and tested for augmentation of specific cellular responses, the intersection between cell biology and material interactions have been difficult to dissect due to the complexity of both physical and chemical interactions. Specifically, modulating materials to target individual signaling pathways is an avenue of interdisciplinary research that may lead to a more effective method of optimizing regenerative materials. In this work, the aim is to summarize the major mechanotransduction pathways for osteogenic differentiation and to consolidate the known materials and material properties that activate such pathways.

Multifunctional Heterogeneous Carbon Nanotube Nanocomposites Assembled by DNA-Binding Peptide Anchors

Although carbon nanotubes (CNTs) are remarkable materials with many exceptional characteristics, their poor chemical functionality limits their potential applications. Herein, a strategy is proposed for functionalizing CNTs, which can be achieved with any functional group (FG) without degrading their intrinsic structure by using a deoxyribonucleic acid (DNA)-binding peptide (DBP) anchor. By employing a DBP tagged with a certain FG, such as thiol, biotin, and carboxyl acid, it is possible to introduce any FG with a controlled density on DNA-wrapped CNTs. Additionally, different types of FGs can be introduced on CNTs simultaneously, using DBPs tagged with different FGs. This method can be used to prepare CNT nanocomposites containing different types of nanoparticles (NPs), such as Au NPs, magnetic NPs, and quantum dots. The CNT nanocomposites decorated with these NPs can be used as reusable catalase-like nanocomposites with exceptional catalytic activities, owing to the synergistic effects of all the components. Additionally, the unique DBP-DNA interaction allows the on-demand detachment of the NPs attached to the CNT surface; further, it facilitates a CNT chirality-specific NP attachment and separation using the sequence-specific programmable characteristics of oligonucleotides. The proposed method provides a novel chemistry platform for constructing new functional CNTs suitable for diverse applications.

Indirect-To-Direct Band Gap Transition of One-Dimensional V2Se9: Theoretical Study with Dispersion Energy Correction

Recently, we synthesized a one-dimensional (1D) structure of V2Se9. The 1D V2Se9 resembles another 1D material, Nb2Se9, which is expected to have a direct band gap. To determine the potential applications of this material, we calculated the band structures of 1D and bulk V2Se9 using density functional theory by varying the number of chains and comparing their band structures and electronic properties with those of Nb2Se9. The results showed that a small number of V2Se9 chains have a direct band gap, whereas bulk V2Se9 possesses an indirect band gap, like Nb2Se9. We expect that V2Se9 nanowires with diameters less than ∼20 Å would have direct band gaps. This indirect-to-direct band gap transition could lead to potential optoelectronic applications for this 1D material because materials with direct band gaps can absorb photons without being disturbed by phonons.

Molecular-Level Interactions between Engineered Materials and Cells

Various recent experimental observations indicate that growing cells on engineered materials can alter their physiology, function, and fate. This finding suggests that better molecular-level understanding of the interactions between cells and materials may guide the design and construction of sophisticated artificial substrates, potentially enabling control of cells for use in various biomedical applications. In this review, we introduce recent research results that shed light on molecular events and mechanisms involved in the interactions between cells and materials. We discuss the development of materials with distinct physical, chemical, and biological features, cellular sensing of the engineered materials, transfer of the sensing information to the cell nucleus, subsequent changes in physical and chemical states of genomic DNA, and finally the resulting cellular behavior changes. Ongoing efforts to advance materials engineering and the cell-material interface will eventually expand the cell-based applications in therapies and tissue regenerations.

Exceptional Mechanical Properties of Phase-Separation-Free Mo3Se3--Chain-Reinforced Hydrogel Prepared by Polymer Wrapping Process

As Mo₃Se₃^- chain nanowires have dimensions comparable to those of natural hydrogel chains (molecular-level diameters of ∼0.6 nm and lengths of several micrometers) and excellent mechanical strength and flexibility, they have large potential to reinforce hydrogels and improve their mechanical properties. When a Mo₃Se₃^--chain-nanowire-gelatin composite hydrogel is prepared simply by mixing Mo₃Se₃^- nanowires with gelatin, phase separation of the Mo₃Se₃^- nanowires from the gelatin matrix occurs in the micronetwork, providing only small improvements in their mechanical properties. In contrast, when the surface of the Mo₃Se₃^- nanowire is wrapped with the gelatin polymer, the chemical compatibility of the Mo₃Se₃^- nanowire with the gelatin matrix is significantly improved, which enables the fabrication of a phase-separation-free Mo₃Se₃^--reinforced gelatin hydrogel. The composite gelatin hydrogel exhibits significantly improved mechanical properties, including a tensile strength of 27.6 kPa, fracture toughness of 26.9 kJ/m³, and elastic modulus of 54.8 kPa, which are 367%, 868%, and 378% higher than those of the pure gelatin hydrogel, respectively. Furthermore, the amount of Mo₃Se₃^- nanowires added in the composite hydrogel is as low as 0.01 wt %. The improvements in the mechanical properties are significantly larger than those for other reported composite hydrogels reinforced with one-dimensional materials.