Hierarchical Micro-Nano Topography Promotes Cell Adhesion and Osteogenic Differentiation via Integrin α2-PI3K-AKT Signaling Axis

Co-assembling bioactive short peptide nanofibers coated silk scaffolds induce neurite outgrowth of PC12 cells

Controlling biomolecular-cell interactions is crucial for the design of scaffolds for tissue engineering (TE). Regenerated silk fibroin (RSF) has been extensively used as TE scaffolds, however, RSF showed poor attachment of neuronal cells, such as rat pheochromocytoma (PC12) cells. In this work, amphiphilic peptides containing a hydrophobic isoleucine tail (I3) and laminin or fibronectin derived peptides (IKVAV, PDSGR, YIGSR, RGDS and PHSRN) were designed for promoting scaffold-cell interaction. Three of them (I3KVAV, I3RGDS and I3YIGSR) can self-assemble into nanofibers, therefore, were used to enhance the application of RSF in neuron TE. Live / dead assays revealed that the peptides exhibited negligible cytotoxicity against PC12 cells. The specific interaction between PC12 cells and the peptides were investigate using atomic force microscopy (AFM). The results indicated a synergistic effect in the designed peptides, promoting cellular attachment, proliferation and morphology changes. In addition, AFM results showed that co-assembling peptides I3KVAV and I3YIGSR possesses the best regulation of proliferation and attachment of PC12 cells, consistent with immunofluorescence staining results. Moreover, cell culture with hydrogels revealed that a mixture of peptides I3KVAV and I3YIGSR can also promote 3D neurites outgrowth. The approach of combining two different self-assembling peptides shows great potential for nerve regeneration applications.

Fabrication and in vitro biocompatibility of hierarchical cellulose acetate/polyvinylpyrrolidone@titania nanowire hollow microfibers

In this study, hierarchical cellulose acetate/polyvinylpyrrolidone hollow microfibers (CA/PVP HMFs) were first prepared via a dip coating method using a steel wire as tubular template and then supported a sol-gel deposition of titania nanoparticles (NPs) to derive CA/PVP@titania NP HMFs. After hydrothermally treated in NaOH solution, CA/PVP@titania NP HMFs were transformed to CA/PVP@titania nanowire (NW) HMFs. SEM observation showed that CA/PVP@titania NW HMFs had a hollow structure with diameters of 450-600 μm and exhibited a hierarchical and nanofibrous structure. Their surfaces were constructed by numerous titania NWs with diameters of 10-30 nm and lengths of 1-5 μm. The incorporation of PVP not only caused a significant change in surface wettability from hydrophobic CA HMFs to hydrophilic CA/PVP HMFs, but also promoted the sol-gel deposition of titania NPs on CA/PVP HMFs. CA/PVP@titania NW HMFs exhibited the highest hydrophilicity with water contact angle of 32° and the largest specific surface area of 86.1 m2/g. In vitro biocompatible evaluation indicated that CA/PVP@titania NW HMFs exhibited much higher cell adhesion and proliferation than CA/PVP@titania NP HMFs and CA/PVP HMFs within 7 days due to the presence of nanofibrous surface architecture. Thus, the present CA/PVP titania NW HMFs have potential as biocompatible cell supporting matrices.

Nanotube topography rejuvenates the senescence of mesenchymal stem cells by activating YAP signalling

Improving the regenerative ability of senescent stem cells is a critical issue in combating aging. The destiny and function of senescent stem cells are controlled by the niche, including the physical architecture of the surface of the extracellular matrix (ECM). In this study, we explored the functions of TiO2 nanotube topography on mesenchymal stem cells (MSCs) under senescence, as well as its mechanical effects on senescence. First, we created different nanotube topographies on the titanium samples. Next, we cultured senescent mesenchymal stem cells (S-MSCs) on samples with various nanotube topographies to determine suitable parameters. We found nanotube with a diameter of 10 nm significantly alleviated the cellular senescence of S-MSCs and improved the osteogenic differentiation of S-MSCs in vitro. Using an ectopic periodontium regeneration model, we confirmed that specific nanotube topography could promote tissue regeneration of S-MSCs in vivo. Moreover, we demonstrated that nanotube topography activated YAP in S-MSCs and reformed nuclear-cytoskeletal morphology to inhibit senescence. Taken together, our study establishes a bridge linking between nano-topography, mechanics, and senescence, suggesting a potential strategy to improve tissue regeneration in aged individuals by providing optimized surface topography on biomaterials.

Enhancing Vasculogenesis in Dental Pulp Development: DPSCs-ECs Communication via FN1-ITGA5 Signaling

BACKGROUND

Dental pulp regeneration therapy is a challenge to achieve early vascularization during treatment. Studying the regulatory mechanisms of vascular formation during human dental pulp development may provide insights for related therapies. In this study, we utilized single-cell sequencing analysis to compare the gene expression of dental pulp stem cells (DPSCs) and vascular endothelial cells (ECs) from developing and mature dental pulps.

METHOD

Immunohistochemistry, Western blot, and real-time polymerase chain reaction (RT-PCR) were used to detect fibronectin 1 (FN1) expression and molecules, such as PI3K/AKT. Cell proliferation assay, scratch assay, tube formation assay and were used to investigate the effects of DPSCs on the vasculogenetic capability of ECs. Additionally, animal experiments involving mice were conducted.

RESULT

The results revealed that DPSCs exist around dental pulp vasculature. FN1 expression was significantly higher in DPSCs from young permanent pulps than mature pulps, promoting HUVEC proliferation, migration, and tube formation via ITGA5 and the downstream PI3K/AKT signaling pathway.

CONCLUSION

Our data indicate that intercellular communication between DPSCs and ECs mediated by FN1-ITGA5 signaling is crucial for vascularizationduring dental pulp development, laying an experimental foundation for future clinical studies.

Investigation of synergic effects of nanogroove topography and polyaniline-chitosan nanocomposites on PC12 cell differentiation and axonogenesis

Axonal damage is the main characteristic of neurodegenerative diseases. This research was focused on remodeling cell morphology and developing a semi-tissue nanoenvironment via mechanobiological stimuli. The combination of nanogroove topography and polyaniline-chitosan enabled the manipulation of the cells by changing the morphology of PC12 cells to spindle shape and inducing the early stage of signal transduction, which is vital for differentiation. The nanosubstarte embedded with nanogooves induced PC12 cells to elongate their morphology and increase their size by 51% as compared with controls. In addition, the use of an electroconductive nanocomposite alongside nanogrooves resulted in the differentiation of PC12 cells into neurons with an average length of 193 ± 7 μm for each axon and an average number of seven axons for each neurite. Our results represent a combined tool to initiate a promising future for cell reprogramming by inducing cell differentiation and specific cellular morphology in many cases, including neurodegenerative diseases.

Nanoscaled Titanium Oxide Layer Provokes Quick Osseointegration on 3D-Printed Dental Implants: A Domino Effect Induced by Hydrophilic Surface

Three-dimensional printing is a revolutionary strategy to fabricate dental implants. Especially, 3D-printed dental implants modified with nanoscaled titanium oxide layer (H-SLM) have impressively shown quick osseointegration, but the accurate mechanism remains elusive. Herein, we unmask a domino effect that the hydrophilic surface of the H-SLM facilitates blood wetting, enhances the blood shear rate, promotes blood clotting, and changes clot features for quick osseointegration. Combining computational fluid dynamic simulation and biological verification, we find a blood shear rate during blood wetting of the hydrophilic H-SLM 1.2-fold higher than that of the raw 3D-printed implant, which activates blood clot formation. Blood clots formed on the hydrophilic H-SLM demonstrate anti-inflammatory and pro-osteogenesis effects, leading to a 1.5-fold higher bone-to-implant contact and a 1.8-fold higher mechanical anchorage at the early stage of osseointegration. This mechanism deepens current knowledge between osseointegration speed and implant surface characteristics, which is instructive in surface nanoscaled modification of multiple 3D-printed intrabony implants.

Synergistic effect of hierarchical topographic structure on 3D-printed Titanium scaffold for enhanced coupling of osteogenesis and angiogenesis

The significance of the osteogenesis-angiogenesis relationship in the healing process of bone defects has been increasingly emphasized in recent academic research. Surface topography plays a crucial role in guiding cellular behaviors. Metal-organic framework (MOF) is an innovative biomaterial with nanoscale structural and topological features, enabling the modulation of scaffold physicochemical properties. This study involved the loading of varying quantities of UiO-66 nanocrystals onto alkali-heat treated 3D-printed titanium scaffolds, resulting in the formation of hierarchical micro/nano topography named UiO-66/AHTs. The physicochemical properties of these scaffolds were subsequently characterized. Furthermore, the impact of these scaffolds on the osteogenic potential of BMSCs, the angiogenic potential of HUVECs, and their intercellular communication were investigated. The findings of this study indicated that 1/2UiO-66/AHT outperformed other groups in terms of osteogenic and angiogenic induction, as well as in promoting intercellular crosstalk by enhancing paracrine effects. These results suggest a promising biomimetic hierarchical topography design that facilitates the coupling of osteogenesis and angiogenesis.

Shape-Morphing Photoresponsive Hydrogels Reveal Dynamic Topographical Conditioning of Fibroblasts

The extracellular environment defines a physical boundary condition with which cells interact. However, to date, cell response to geometrical environmental cues is largely studied in static settings, which fails to capture the spatiotemporally varying cues cells receive in native tissues. Here, a photoresponsive spiropyran-based hydrogel is presented as a dynamic, cell-compatible, and reconfigurable substrate. Local stimulation with blue light (455 nm) alters hydrogel swelling, resulting in on-demand reversible micrometer-scale changes in surface topography within 15 min, allowing investigation into cell response to controlled geometry actuations. At short term (1 h after actuation), fibroblasts respond to multiple rounds of recurring topographical changes by reorganizing their nucleus and focal adhesions (FA). FAs form primarily at the dynamic regions of the hydrogel; however, this propensity is abolished when the topography is reconfigured from grooves to pits, demonstrating that topographical changes dynamically condition fibroblasts. Further, this dynamic conditioning is found to be associated with long-term (72 h) maintenance of focal adhesions and epigenetic modifications. Overall, this study offers a new approach to dissect the dynamic interplay between cells and their microenvironment and shines a new light on the cell's ability to adapt to topographical changes through FA-based mechanotransduction.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

An engineered lamellar bone mimicking full-scale hierarchical architecture for bone regeneration

Lamellar bone, compactly and ingeniously organized in the hierarchical pattern with 6 ordered scales, is the structural motif of mature bone. Each hierarchical scale exerts an essential role in determining physiological behavior and osteogenic bioactivity of bone. Engineering lamellar bone with full-scale hierarchy remains a longstanding challenge. Herein, using bioskiving and mineralization, we attempt to engineer compact constructs resembling full-scale hierarchy of lamellar bone. Through systematically investigating the effect of mineralization on physicochemical properties and bioactivities of multi-sheeted collagen matrix fabricated by bioskiving, the hierarchical mimicry and hierarchy-property relationship are elucidated. With prolongation of mineralization, hierarchical mimicry and osteogenic bioactivity of constructs are performed in a bidirectional manner, i.e. first rising and then descending, which is supposed to be related with transformation of mineralization mechanism from nonclassical to classical crystallization. Construct mineralized 9 days can accurately mimic each hierarchical scale and efficiently promote osteogenesis. Bioinformatic analysis further reveals that this construct potently activates integrin α5-PI3K/AKT signaling pathway through mechanical and biophysical cues, and thereby repairing critical-sized bone defect. The present study provides a bioinspired strategy for completely resembling complex hierarchy of compact mineralized tissue, and offers a critical research model for in-depth studying the structure-function relationship of bone.

4D Printing of Personalized-Tunable Biomimetic Periosteum with Anisotropic Microstructure for Accelerated Vascularization and Bone Healing

An ideal biomimetic periosteum is expected to wrap various bone surfaces to orchestrate an optimal microenvironment for bone regeneration, including facilitating local vascularization, recruiting osteoblasts, and mineralizing the extracellular matrix (ECM). To mimic the role of the natural periosteum in promoting bone repair, a 4D printing technique to inlay aligned cell sheets on shape-shifting hydrogel is used, containing biophysical signals and spatially adjustable physical properties, for the first time. The outer hydrogel layer endows the biomimetic periosteum with the ability to digitally coordinate its 3D geometry to match the specific macroscopic bone shape to maintain a bone healing microenvironment. The inner aligned human mesenchymal stem cells (hMSCs) layer not only promotes the migration and angiogenesis of co-cultured cells but also exhibits excellent osteogenic differentiation properties. In vivo experiments show that apart from morphing preset shapes as physical barriers, the aligned biomimetic periosteum can actively facilitate local angiogenesis and early-stage osteogenesis. Altogether, this present work provides a novel route to construct a personalized biomimetic periosteum with anisotropic microstructure by introducing a tunable shape to maintain the bone reconstruction microenvironment and this strategy can be extended to repair sophisticated bone defects.

Response of mesenchymal stem cells to surface topography of scaffolds and the underlying mechanisms

Mesenchymal stem/stromal cells (MSCs) serve as essential components of regenerative medicine. Their destiny is influenced by the interaction of the cells with the external environment. In addition to the biochemical cues in a microenvironment, physical cues of the topography of the surrounding materials such as the extracellular matrix emerge as a crucial regulator of stem cell destiny and function. With recent advances in technologies of materials production and surface modification, surfaces with micro/nanotopographical characteristics can be fabricated to mimic the micro/nanoscale mechanical stimuli of the extracellular matrix environment and regulate the biological behavior of cells. Understanding the interaction of cells with the topography of a surface is conducive to the control of stem cell fate for application in regenerative medicine. However, the mechanisms by which topography affects the biological behavior of stem cells have not been fully elucidated. This review will present the effects of surface topography at the nano/micrometer scale on stem cell adhesion, morphology, proliferation, migration, and differentiation. It also focuses on discussing current theories about the sensing and recognition of surface topology cues, the transduction of the extracellular cues into plasma, and the final activation of related signaling pathways and downstream gene expression in MSCs. These insights will provide a theoretical basis for the future design of biomaterial scaffolds for application in regenerative medicine and tissue engineering.

Functional chitosan gel coating enhances antimicrobial properties and osteogenesis of titanium alloy under persistent chronic inflammation

Titanium is widely used as surgical bone implants due to its excellent mechanical properties, corrosion resistance, and good biocompatibility. However, due to chronic inflammation and bacterial infections caused by titanium implants, they are still at risk of failure in interfacial integration of bone implants, severely limiting their broad clinical application. In this work, chitosan gels crosslinked with glutaraldehyde were prepared and successfully loaded with silver nanoparticles (nAg) and catalase nanocapsules (n (CAT)) to achieve functionalized coating on the surface of titanium alloy steel plates. Under chronic inflammatory conditions, n (CAT) significantly reduced the expression of macrophage tumor necrosis factor (TNF-α), increased the expression of osteoblast alkaline phosphatase (ALP) and osteopontin (OPN), and enhanced osteogenesis. At the same time, nAg inhibited the growth of S. aureus and E. coli. This work provides a general approach to functional coating of titanium alloy implants and other scaffolding materials.

Analysis of disordered abrasive scratches on titanium surfaces and their impact on nuclear translocation of yes-associated protein

The morphology of the metallic surface of an implant is important for its contact with bone tissue as it directly affects osteoblast functions, such as cell adhesion, proliferation, and differentiation. Firm contact between the implant and cells creates a barrier that prevents inflammation and bacterial infections. Therefore, optimizing surface morphology, such as surface roughness adjustments, is essential to improving the adhesion between the implant and cells for successful tissue regeneration. However, the manner in which the cells sense the surface roughness and morphology remains unclear. Previously, we analyzed cell adhesion behavior and observed that inhibited cell spreading can delay osteoblast functions. Therefore, assuming that the surface morphology can be sensed through cell spreading, we investigated the cell spreading area and yes-associated protein (YAP) localization in mouse osteoblasts (MC3T3-E1) on a titanium surface with disordered abrasive scratches. Surface roughness of 100-150 nm was obtained by polishing, which inhibited the cell spreading, indicating that YAP localization in the nucleus was lower than that on other surfaces. The obtained results indicate that the cells sense the surface environment based on their spreading area, which regulates cellular functions via the Hippo pathway.

Poly(ε-Caprolactone) Substrates with Micro/Nanohierarchical Patterned Structures for Cell Culture

A simple, efficient and controllable one-step template method is proposed to fabricate poly(ε-caprolactone) substrates with micro/nanohierarchical patterned structures. Two kinds of geometric patterns with and without nanowires, i.e., hexagonal and strip with controllable island size and spacing are designed and fabricated. Furthermore, the influence of geometric patterns, island size, island spacing, and patterned nanowires (pNW) on the growth behavior of MG-63 cells is studied in terms of cell density, distribution, proliferation, morphogenesis, and cellular alignment. It is found that MG-63 cells prefer to adhere and grow on the substrate with smaller island size or spacing. Moreover, unlike the hexagonal structure, the strip structure can guide cellular alignment on its surface. In addition, the microisland structures and the pNW play different roles in promoting cell proliferation, distribution, and morphogenesis. It is concluded that the growth behavior of MG-63 cells can be well controlled by precisely adjusting the micro/nanostructure of the substrate surface. A simple and effective method is provided here for the regulation of cell growth behavior.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Micro/Nanostructured Topography on Titanium Orchestrates Dendritic Cell Adhesion and Activation via β2 Integrin-FAK Signals

Background and Purpose

In clinical application of dental implants, the functional state of dendritic cells (DCs) has been suggested to have a close relationship with the implant survival rate or speed of osseointegration. Although microscale surfaces have a stable osteogenesis property, they also incline to trigger unfavorable DCs activation and threaten the osseointegration process. Nanoscale structures have an advantage in regulating cell immune response through orchestrating cell adhesion, indicating the potential of hierarchical micro/nanostructured surface in regulation of DCs’ activation without sacrificing the advantage of microscale topography.

Materials and Methods

Two micro/nanostructures were fabricated based on microscale rough surfaces through anodization or alkali treatment, the sand-blasted and acid-etched (SA) surface served as control. The surface characteristics, in vitro and in vivo DC immune reactions and β2 integrin-FAK signal expression were systematically investigated. The DC responses to different surface topographies after FAK inhibition were also tested.

Results

Both micro/nano-modified surfaces exhibited unique composite structures, with higher hydrophilicity and lower roughness compared to the SA surface. The DCs showed relatively immature functional states with round morphologies and significantly downregulated β2 integrin-FAK levels on micro/nanostructures. Implant surfaces with micro/nano-topographies also triggered lower levels of DC inflammatory responses than SA surfaces in vivo. The inhibited FAK activation effectively reduced the differences in topography-caused DC activation and narrowed the differences in DC activation among the three groups.

Conclusion

Compared to the SA surface with solely micro-scale topography, titanium surfaces with hybrid micro/nano-topographies reduced DC inflammatory response by influencing their adhesion states. This regulatory effect was accompanied by the modulation of β2 integrin-FAK signal expression. The β2 integrin-FAK-mediated adhesion plays a critical role in topography-induced DC activation, which represents a potential target for material–cell interaction regulation.

A biomimetic piezoelectric scaffold with sustained Mg2+ release promotes neurogenic and angiogenic differentiation for enhanced bone regeneration

Natural bone is a composite tissue made of organic and inorganic components, showing piezoelectricity. Whitlockite (WH), which is a natural magnesium-containing calcium phosphate, has attracted great attention in bone formation recently due to its unique piezoelectric property after sintering treatment and sustained release of magnesium ion (Mg²⁺). Herein, a composite scaffold (denoted as PWH scaffold) composed of piezoelectric WH (PWH) and poly(ε-caprolactone) (PCL) was 3D printed to meet the physiological demands for the regeneration of neuro-vascularized bone tissue, namely, providing endogenous electric field at the defect site. The sustained release of Mg²⁺ from the PWH scaffold, displaying multiple biological activities, and thus exhibits a strong synergistic effect with the piezoelectricity on inhibiting osteoclast activation, promoting the neurogenic, angiogenic, and osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) in vitro. In a rat calvarial defect model, this PWH scaffold is remarkably conducive to efficient neo-bone formation with rich neurogenic and angiogenic expressions. Overall, this study presents the first example of biomimetic piezoelectric scaffold with sustained Mg²⁺ release for promoting the regeneration of neuro-vascularized bone tissue in vivo, which offers new insights for regenerative medicine.

Involvement of PI3K/Akt signaling pathway in promoting osteogenesis on titanium implant surfaces modified with novel non-thermal atmospheric plasma

Non-thermal atmospheric plasma (NTAP) modification to induce a hydrophilic titanium (Ti) surface with less carbon contamination, has been demonstrated to boost the osteogenic responses. In this study, we investigated the underlying bone formation mechanism of NTAP-Ti, and the involvement of PI3K/Akt signaling pathway in regulating osteogenic activities on NTAP-Ti surfaces. NTAP was employed for Ti activation, and PI3K inhibitor, LY294002, was applied to the suppression of PI3K/Akt pathway. We systematically and quantitatively detected the cell morphology, attachment, proliferation, osteogenic differentiation and mineralization of MC3T3-E1 mouse preosteoblasts, and molecular expressions involved in osteogenesis and PI3K/Akt signaling pathway in vivo and in vitro. A descent in osteoblast proliferation on Ti surfaces in relation to LY294002. Alkaline phosphatase (ALP) activity, as well as matrix mineralization, was mitigated by PI3K inhibitor in NTAP-Ti. Likewise, the expression levels of osteogenesis-related genes [ALP, osteocalcin (Ocn), osteopontin (Opn) and runt-related transcription factor 2 (Runx2)] on NTAP-Ti were notably attenuated by LY294002, as confirmed by the results of osteogenesis-related proteins (ALP, and Runx2) expression analysis. In addition, the expression of PI3K/Akt signal pathway proteins further verified the inhibition of LY294002 on Ti surfaces modified by NTAP. Collectively, the PI3K/Akt signal pathway was involved in the amelioration of osteogenesis induced by NTAP modification. NTAP treatment for Ti activation is promising in augmented osteogenic potential through the activation of PI3K/Akt signal pathway.

Delivering Mechanical Stimulation to Cells: State of the Art in Materials and Devices Design

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If the biochemical signals are assumed to be one side of the coin, the other side comprises biophysical cues. There is growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. Here, an overview of the current state of the art in the design and development of such materials and devices is provided, with a focus on their design principles, and challenges and perspectives for future research directions are highlighted.

Network pharmacology of iridoid glycosides from Eucommia ulmoides Oliver against osteoporosis

Eucommia ulmoides Oliver is one of the commonly used traditional Chinese medicines for the treatment of osteoporosis, and iridoid glycosides are considered to be its active ingredients against osteoporosis. This study aims to clarify the chemical components and molecular mechanism of iridoid glycosides of Eucommia ulmoides Oliver in the treatment of osteoporosis by integrating network pharmacology and molecular simulations. The active iridoid glycosides and their potential targets were retrieved from text mining as well as Swiss Target Prediction, TargetNet database, and STITCH databases. At the same time, DisGeNET, GeneCards, and Therapeutic Target Database were used to search for the targets associated with osteoporosis. A protein–protein interaction network was built to analyze the interactions between targets. Then, DAVID bioinformatics resources and R 3.6.3 project were used to carry out Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Moreover, interactions between active compounds and potential targets were investigated through molecular docking, molecular dynamic simulation, and binding free energy analysis. The results showed that a total of 12 iridoid glycosides were identified as the active iridoid glycosides of Eucommia ulmoides Oliver in the treatment of osteoporosis. Among them, aucubin, reptoside, geniposide and ajugoside were the core compounds. The enrichment analysis suggested iridoid glycosides of Eucommia ulmoides Oliver prevented osteoporosis mainly through PI3K-Akt signaling pathway, MAPK signaling pathway and Estrogen signaling pathway. Molecular docking results indicated that the 12 iridoid glycosides had good binding ability with 25 hub target proteins, which played a critical role in the treatment of osteoporosis. Molecular dynamic and molecular mechanics Poisson–Boltzmann surface area results revealed these compounds showed stable binding to the active sites of the target proteins during the simulations. In conclusion, our research demonstrated that iridoid glycosides of Eucommia ulmoides Oliver in the treatment of osteoporosis involved a multi-component, multi-target and multi-pathway mechanism, which provided new suggestions and theoretical support for treating osteoporosis.

Biomaterials to enhance stem cell transplantation

The successful transplantation of stem cells has the potential to transform regenerative medicine approaches and open promising avenues to repair, replace, and regenerate diseased, damaged, or aged tissues. However, pre-/post-transplantation issues of poor cell survival, retention, cell fate regulation, and insufficient integration with host tissues constitute significant challenges. The success of stem cell transplantation depends upon the coordinated sequence of stem cell renewal, specific lineage differentiation, assembly, and maintenance of long-term function. Advances in biomaterials can improve pre-/post-transplantation outcomes by integrating biophysiochemical cues and emulating tissue microenvironments. This review highlights leading biomaterials-based approaches for enhancing stem cell transplantation.

Advancing bone tissue engineering one layer at a time: a layer-by-layer assembly approach to 3D bone scaffold materials

The layer-by-layer (LbL) assembly technique has shown excellent potential in tissue engineering applications. The technique is mainly based on electrostatic attraction and involves the sequential adsorption of oppositely charged electrolyte complexes onto a substrate, resulting in uniform single layers that can be rapidly deposited to form nanolayer films. LbL has attracted significant attention as a coating technique due to it being a convenient and affordable fabrication method capable of achieving a wide range of biomaterial coatings while keeping the main biofunctionality of the substrate materials. One promising application is the use of nanolayer films fabricated by LbL assembly in the development of 3-dimensional (3D) bone scaffolds for bone repair and regeneration. Due to their versatility, nanoscale films offer an exciting opportunity for tailoring surface and bulk property modification of implants for osseous defect therapies. This review article discusses the state of the art of the LbL assembly technique, and the properties and functions of LbL-assembled films for engineered bone scaffold application, combination of multilayers for multifunctional coatings and recent advancements in the application of LbL assembly in bone tissue engineering. The recent decade has seen tremendous advances in the promising developments of LbL film systems and their impact on cell interaction and tissue repair. A deep understanding of the cell behaviour and biomaterial interaction for the further development of new generations of LbL films for tissue engineering are the most important targets for biomaterial research in the field. While there is still much to learn about the biological and physicochemical interactions at the interface of nano-surface coated scaffolds and biological systems, we provide a conceptual review to further progress in the LbL approach to 3D bone scaffold materials and inform the future of LbL development in bone tissue engineering.

Preparation of Assemblable Chondral and Subchondral Bone Microtissues for Osteochondral Tissue Engineering

Microtissues exhibit great advantages in injecting with minimum invasiveness, mimicking natural tissues, and promoting tissue regeneration. However, very few studies have focused on the construction of osteochondral microtissues that could simultaneously support hyaline-like cartilage and bone tissue regeneration. In this study, chondral microtissues that could favor the formation of hyaline-like cartilages and subchondral bone microtissues that could repair subchondral defects to support the neo-generated cartilages were successfully constructed for osteochondral tissue engineering. For chondral repair, the developed chondral microgels with high porosity and hydrophilicity could make cells spherical, favor the formation of cell aggregates, and show an excellent differentiation effect toward hyaline-like cartilage, thus contributing to the production of chondral microtissues. For subchondral bone repair, the fabricated subchondral microgels realize cell adhesion and proliferation and support the osteogenic differentiation of stem cells, thus favoring the formation of subchondral bone microtissues. The injectable chondral and subchondral bone microtissues could be stably assembled by Michael addition reaction between sulfhydryl groups of microtissues and double bonds of hydrophilic macromolecular cross-linker. At 12 weeks postimplantation, osteochondral microtissues could support the reconstruction of osteochondral-like tissues. The present study provides new insight into the microtissues for repair of osteochondral tissues.

The Bumpy Road to Stem Cell Therapies: Rational Design of Surface Topographies to Dictate Stem Cell Mechanotransduction and Fate

Cells sense and respond to a variety of physical cues from their surrounding microenvironment, and these are interpreted through mechanotransductive processes to inform their behavior. These mechanisms have particular relevance to stem cells, where control of stem cell proliferation, potency, and differentiation is key to their successful application in regenerative medicine. It is increasingly recognized that surface micro- and nanotopographies influence stem cell behavior and may represent a powerful tool with which to direct the morphology and fate of stem cells. Current progress toward this goal has been driven by combined advances in fabrication technologies and cell biology. Here, the capacity to generate precisely defined micro- and nanoscale topographies has facilitated the studies that provide knowledge of the mechanotransducive processes that govern the cellular response as well as knowledge of the specific features that can drive cells toward a defined differentiation outcome. However, the path forward is not fully defined, and the "bumpy road" that lays ahead must be crossed before the full potential of these approaches can be fully exploited. This review focuses on the challenges and opportunities in applying micro- and nanotopographies to dictate stem cell fate for regenerative medicine. Here, key techniques used to produce topographic features are reviewed, such as photolithography, block copolymer lithography, electron beam lithography, nanoimprint lithography, soft lithography, scanning probe lithography, colloidal lithography, electrospinning, and surface roughening, alongside their advantages and disadvantages. The biological impacts of surface topographies are then discussed, including the current understanding of the mechanotransductive mechanisms by which these cues are interpreted by the cells, as well as the specific effects of surface topographies on cell differentiation and fate. Finally, considerations in translating these technologies and their future prospects are evaluated.

Hierarchical microgroove/nanopore topography regulated cell adhesion to enhance osseointegration around intraosseous implants in vivo

Implant surface topography plays a crucial role in achieving successful implantation. Simple and controllable surface topographical modifications are considered a promising method to accelerate bone osseointegration for biomedical applications. Moreover, comprehension of the mechanism between surface topography and cell osteogenic differentiation is vital for the manipulation of these processes to promote bone tissue regeneration. In this study, we investigated the effects of implant surfaces with various sized hierarchical microgroove/nanopore topographies on cell adhesion, osteogenesis, and their underlying mechanism both in vitro and in vivo. Our findings reveal that a titanium surface with an appropriately sized microgroove/nanopore topography (SLM-1MAH) exhibits the more satisfactory adhesive and osteogenic efficiency than the clinically used sand-blasted, large-grit, and acid-etched (SLA) surface. The underlying molecular mechanism lies in the activation of the integrin α2-PI3K-Akt signaling pathway, where the SLM-1MAH surface increased the protein expressions of integrin α2 (Itga2), phosphatidylinositol 3-kinase (PI3K), and phosphorylated serine/threonine kinase Akt (p-Akt) to enhance osteogenesis and osseointegration. Furthermore, the SLM-1MAH surface also displays better osseointegration efficiency with stronger bonding strength than that on the SLA surface. This work provides a novel strategy for implant surface topography design to improve bone-implant osseointegration.

Biomimicked hierarchical 2D and 3D structures from natural templates: applications in cell biology

Intricate structures of natural surfaces and materials have amazed people over the ages. The unique properties of various surfaces also created interest and curiosity in researchers. In the recent past, with the advent of superior microscopy techniques, we have started to understand how these complex structures provide superior properties. With that knowledge, scientists have developed various biomimicked and bio-inspired surfaces for different non-biological applications. In the last two decades, we have also started to learn how structures of the tissue microenvironment influence cell function and behaviour, both in physiological and pathological conditions. Hence, it became essential to decipher the role and importance of structural hierarchy in the cellular context. With advances in microfabricated techniques, such complex structures were made by superimposing features of different dimensions. However, the fabricated topographies are far from matching the complexities presentin vivo. Hence, the need of biomimicking the natural surfaces for cellular applications was felt. In this review, we discuss a few examples of hierarchical surfaces found in plants, insects, and vertebrates. Such structures have been widely biomimicked for various applications but rarely studied for cell-substrate interaction and cellular response. Here, we discuss the research work wherein 2D hierarchical substrates were prepared using biomimicking to understand cellular functions such as adhesion, orientation, differentiation, and formation of spheroids. Further, we also present the status of ongoing research in mimicking 3D tissue architecture using de-cellularized plant-based and tissue/organ-based scaffolds. We will also discuss 3D printing for fabricating 2D and 3D hierarchical structures. The review will end by highlighting the various advantages and research challenges in this approach. The biomimickedin-vivolike substrate can be used to better understand cellular physiology, and for tissue engineering.

The effects of surface topography modification on hydrogel properties

Hydrogel has been an attractive biomaterial for tissue engineering, drug delivery, wound healing, and contact lens materials, due to its outstanding properties, including high water content, transparency, biocompatibility, tissue mechanical matching, and low toxicity. As hydrogel commonly possesses high surface hydrophilicity, chemical modifications have been applied to achieve the optimal surface properties to improve the performance of hydrogels for specific applications. Ideally, the effects of surface modifications would be stable, and the modification would not affect the inherent hydrogel properties. In recent years, a new type of surface modification has been discovered to be able to alter hydrogel properties by physically patterning the hydrogel surfaces with topographies. Such physical patterning methods can also affect hydrogel surface chemical properties, such as protein adsorption, microbial adhesion, and cell response. This review will first summarize the works on developing hydrogel surface patterning methods. The influence of surface topography on interfacial energy and the subsequent effects on protein adsorption, microbial, and cell interactions with patterned hydrogel, with specific examples in biomedical applications, will be discussed. Finally, current problems and future challenges on topographical modification of hydrogels will also be discussed.

Calcium and integrin binding protein 1 (CIB1) induces myocardial fibrosis in myocardial infarction via regulating the PI3K/Akt pathway

Myocardial infarction (MI) is a severe coronary artery disease resulted from substantial and sustained ischemia. Abnormal upregulation of calcium and integrin binding protein 1 (CIB1) has been found in several cardiovascular diseases. In this study, we established a mouse model of MI by permanent ligation of the left anterior descending coronary artery. CIB1 was upregulated in the heart of MI mice. Notably, CIB1 knockdown by intramuscular injection of lentivirus-mediated short hairpin RNA (shRNA) targeting Cib1 improved cardiac function and attenuated myocardial hypertrophy and infarct area in MI mice. MI-induced upregulation of α-SMA, vimentin, Collagen I, and Collagen III, which resulted in collagen production and myocardial fibrosis, were regressed by CIB1 silencing. In vitro, cardiac fibroblasts (CFs) isolated from mice were subjected to angiotensin II (Ang II) treatment. Inhibition of CIB1 downregulated the expression of α-SMA, vimentin, Collagen I, and Collagen III in Ang II-treated CFs. Moreover, CIB1 knockdown inhibited Ang II-induced phosphorylation of PI3K-p85 and Akt in CFs. The effect of CIB1 knockdown on Ang II-induced cellular injury was comparable to that of LY294002, a specific inhibitor of the PI3K/Akt pathway. We demonstrated that MI-induced cardiac hypertrophy, myocardial fibrosis, and cardiac dysfunction might be attributed to the upregulation of CIB1 in MI mice. Downregulation of CIB1 alleviated myocardial fibrosis and cardiac dysfunction by decreasing the expression of α-SMA, vimentin, Collagen I, and Collagen III via inhibiting the PI3K/Akt pathway. Therefore, CIB1 may be a potential target for MI treatment.

Cornuside I promoted osteogenic differentiation of bone mesenchymal stem cells through PI3K/Akt signaling pathway

Background

Osteoporosis is a common disease closely associated with aging. In this study, we aimed to investigate the role of Cornuside I in promoting osteogenic differentiation of bone mesenchymal stem cells (BMSCs) and the potential mechanism.

Methods

BMSCs were isolated and treated with different concentrations of Cornuside I (0, 10, 30, 60 μM). Cell proliferation was analyzed by Cell Counting Kit-8 (CCK-8) assay. RNA sequencing was performed on the isolated BMSCs with control and Cornuside I treatment. Differentially expressed genes were obtained by the R software. Alkaline phosphatase (ALP) staining and Alizarin Red Staining (ARS) were performed to assess the osteogenic capacity of the NEO. qRT-PCR and western blot were used to detect the expression of osteoblast markers.

Results

Cornuside I treatment significantly improved BMSC proliferation. The optimal dose of Cornuside I was 30 μM (P < 0.05). Cornuside I dose dependently increased the ALP activity and calcium deposition than control group (P < 0.05). A total of 704 differentially expressed genes were identified between Cornuside I and normal BMSCs. Cornuside I significantly increased the PI3K and Akt expression. Moreover, the promotion effects of Cornuside I on osteogenic differentiation of BMSCs were partially blocked by PI3K/Akt inhibitor, LY294002.

Conclusion

Cornuside I plays a positive role in promoting osteogenic differentiation of BMSCs, which was related with activation of PI3K/Akt signaling pathway.

Beta1-integrin/Hedgehog-Gli1 signaling pathway fuels the diameter-dependent osteoblast differentiation on different TiO2 nanotubes: The optimal-diameter nanotubes for osteoblast differentiation

Micro/nanotextured topographies (MNTs) can modulate cell-biomaterial interactions mostly by their controllable geometrics. Among them, TiO₂ nanotubes, regarded as having a highly controllable nanoscale geometry, have been extensively investigated and applied and significantly affect diameter-dependent cell biological behaviors. In this study, we used five typical MNTs decorated with TiO₂ nanotubes with diameters of 30, 50, 70, 100 and 120 nm to explore the optimal nanotube diameter for improving the biofunctional properties and to more deeply understand the underlying mechanisms by which these MNTs affect osteogenic differentiation by revealing the effect of beta1-integrin/Hedgehog-Gli1 signaling on this process. The MNTs affected MG63 osteoblast-like cell spreading, osteogenic gene expression (BMP-2, Runx2 and ALP), mineralization and ALP activity in a diameter-dependent pattern, and the optimal TiO₂ nanotube diameter of 70 nm provided the best microenvironment for osteogenic differentiation as well as beta1-integrin/Hedgehog-Gli1 signaling activation. This enhanced osteogenic differentiation by the optimal-diameter TiO₂ nanotubes of 70 nm was attenuated via suppression of the beta1-integrin/ Hedgehog-Gli1 signaling, which indicated a significant role of this pathway in mediating the diameter-dependent osteogenic differentiation promotional effect of MNTs with different TiO₂ nanotube diameters. These results might provide deeper insights into the signal transduction mechanisms by which different nanoscale geometries influence cellular functions for biomaterial modification and biofunctionalization.

mTORC2 regulates hierarchical micro/nano topography-induced osteogenic differentiation via promoting cell adhesion and cytoskeletal polymerization

Surface topography acts as an irreplaceable role in the long‐term success of intraosseous implants. In this study, we prepared the hierarchical micro/nano topography using selective laser melting combined with alkali heat treatment (SLM‐AHT) and explored the underlying mechanism of SLM‐AHT surface‐elicited osteogenesis. Our results show that cells cultured on SLM‐AHT surface possess the largest number of mature FAs and exhibit a cytoskeleton reorganization compared with control groups. SLM‐AHT surface could also significantly upregulate the expression of the cell adhesion‐related molecule p‐FAK, the osteogenic differentiation‐related molecules RUNX2 and OCN as well as the mTORC2 signalling pathway key molecule Rictor. Notably, after the knocked‐down of Rictor, there were no longer significant differences in the gene expression levels of the cell adhesion‐related molecules and osteogenic differentiation‐related molecules among the three titanium surfaces, and the cells on SLM‐AHT surface failed to trigger cytoskeleton reorganization. In conclusion, the results suggest that mTORC2 can regulate the hierarchical micro/nano topography‐mediated osteogenesis via cell adhesion and cytoskeletal reorganization.

Magnetic Properties of Iron Oxide Nanoparticles Do Not Essentially Contribute to Ferrogel Biocompatibility

Two series of composite polyacrylamide (PAAm) gels with embedded superparamagnetic Fe₂O₃ or diamagnetic Al₂O₃ nanoparticles were synthesized, aiming to study the direct contribution of the magnetic interactions to the ferrogel biocompatibility. The proliferative activity was estimated for the case of human dermal fibroblast culture grown onto the surfaces of these types of substrates. Spherical non-agglomerated nanoparticles (NPs) of 20-40 nm in diameter were prepared by laser target evaporation (LTE) electrophysical technique. The concentration of the NPs in gel was fixed at 0.0, 0.3, 0.6, or 1.2 wt.%. Mechanical, electrical, and magnetic properties of composite gels were characterized by the dependence of Young's modulus, electrical potential, magnetization measurements on the content of embedded NPs. The fibroblast monolayer density grown onto the surface of composite substrates was considered as an indicator of the material biocompatibility after 96 h of incubation. Regardless of the superparamagnetic or diamagnetic nature of nanoparticles, the increase in their concentration in the PAAm composite provided a parallel increase in the cell culture proliferation when grown onto the surface of composite substrates. The effects of cell interaction with the nanostructured surface of composites are discussed in order to explain the results.

Sustainable aquaculture side-streams derived hybrid biocomposite for bone tissue engineering

Despite being a rich source of bioactive compounds, the current exploitation of aquatic biomass is insufficient. Majority of the aquaculture industry side-streams are currently used for low-value purposes such as animal feed or composting material, with low economical returns. To maximize resource reuse and minimize waste generation, valorization efforts should be augmented with the aim to produce high-value products. Herein, we present a novel aquaculture wastes-derived multi-scale osteoconductive hybrid biocomposite that is composed of chemically crosslinked American bullfrog (Rana catesbeiana) skin-derived type I tropocollagen nanofibrils (~22.3 nm) network and functionalized with micronized (~1.6 μm) single-phase hydroxyapatite (HA) from discarded snakehead (Channa micropeltes) fish scales. The bioengineered construct is biocompatible, highly porous (>90%), and exhibits excellent osteoconductive properties, as indicated by robust adhesion and proliferation of human fetal osteoblastic 1.19 cell line (hFOB 1.19). Furthermore, increased expression level of osteo-related ALPL and BGLAP mRNA transcripts, as well as enhanced osteocalcin immunoreactivity and increasing Alizarin red S staining coverage on the hybrid biocomposite was observed over 21 days of culture. Collectively, the devised "waste-to-resource" platform represents a sustainable waste valorization strategy that is amendable for advanced bone repair and regeneration applications.

Facile cell patterning induced by combined surface topography and chemistry on polydopamine-defined nanosubstrates

Cell patterning holds significant implications for cell-based analysis and high-throughput screening. The challenge and key factor for formation of cell patterns is to precisely modulate the interaction between cells and substrate surfaces. Many nanosubstrates have been developed to control cell adhesion and patterning, however, requirements of complicated fabrication procedures, harsh reaction conditions, and delicate manipulation are not routinely feasible. Here, we developed a hierarchical polydimethylsiloxane nanosubstrate (HPNS) coated with mussel-inspired polydopamine (PDA) micropatterns for effective cell patterning, depending on both surface topography and chemistry. HPNSs obtained by facile template-assisted replication brought enhanced topographic interaction between cells and substrates, but they were innately hydrophobic and cell-repellent. The hydrophobic nanosubstrates were converted to be hydrophilic after PDA coatings formed via spontaneous self-polymerization, which greatly facilitated cell adhesion. As such, without resorting to any external forces or physical constraints, cells selectively adhered and spread on spatially defined PDA regions with high efficiency, and well-defined cell microarrays could be formed within 20 min. Therefore, this easy-to-fabricate nanosubstrate with no complex chemical modification will afford a facile yet effective platform for rapid cell patterning.

The Role and Activation Mechanism of TAZ in Hierarchical Microgroove/Nanopore Topography-Mediated Regulation of Stem Cell Differentiation

Purpose

To investigate the role and activation mechanism of TAZ in periodontal ligament stem cells (PDLSCs) perceiving hierarchical microgroove/nanopore topography.

Materials and Methods

Titanium surface with hierarchical microgroove/nanopore topography fabricated by selective laser melting combined with alkali heat treatment (SLM-AHT) was used as experimental group, smooth titanium surface (Ti) and sandblasted, large-grit, acid-etched (SLA) titanium surface were employed as control groups. Alkaline phosphatase (ALP) activity assays, qRT-PCR, Western blotting, and immunofluorescence were carried out to evaluate the effect of SLM-AHT surface on PDLSC differentiation. Moreover, TAZ activation was investigated from the perspective of nuclear localization to transcriptional activity. TAZ knockdown PDLSCs were seeded on three titanium surfaces to detect osteogenesis- and adipogenesis-related gene expression levels. Immunofluorescence and Western blotting were employed to investigate the effect of the SLM-AHT surface on actin cytoskeletal polymerization and MAPK signaling pathway. Cytochalasin D and MAPK signaling pathway inhibitors were used to determine whether actin cytoskeletal polymerization and the MAPK signaling pathway were indispensable for TAZ activation.

Results

Our results showed that SLM-AHT surface had a greater potential to promote PDLSC osteogenic differentiation while inhibiting adipogenic differentiation than the other two groups. The nuclear localization and transcriptional activity of TAZ were strongly enhanced on the SLM-AHT surface. Moreover, after TAZ knockdown, the enhanced osteogenesis and decreased adipogenesis in SLM-AHT group could not be observed. In addition, SLM-AHT surface could promote actin cytoskeletal polymerization and upregulate p-ERK and p-p38 protein levels. After treatment with cytochalasin D and MAPK signaling pathway inhibitors, differences in the TAZ subcellular localization and transcriptional activity were no longer observed among the different titanium surfaces.

Conclusion

Our results demonstrated that actin cytoskeletal polymerization and MAPK signaling pathway activation triggered by SLM-AHT surface were essential for TAZ activation, which played a dominant role in SLM-AHT surface-induced stem cell fate decision.

Self-agglomerated collagen patterns govern cell behaviour

Reciprocity between cells and their surrounding extracellular matrix is one of the main drivers for cellular function and, in turn, matrix maintenance and remodelling. Unravelling how cells respond to their environment is key in understanding mechanisms of health and disease. In all these examples, matrix anisotropy is an important element, since it can alter the cell shape and fate. In this work, the objective is to develop and exploit easy-to-produce platforms that can be used to study the cellular response to natural proteins assembled into diverse topographical cues. We demonstrate a robust and simple approach to form collagen substrates with different topographies by evaporating droplets of a collagen solution. Upon evaporation of the collagen solution, a stain of collagen is left behind, composed of three regions with a distinct pattern: an isotropic region, a concentric ring pattern, and a radially oriented region. The formation and size of these regions can be controlled by the evaporation rate of the droplet and initial collagen concentration. The patterns form topographical cues inducing a pattern-specific cell (tenocyte) morphology, density, and proliferation. Rapid and cost-effective production of different self-agglomerated collagen topographies and their interfaces enables further study of the cell shape-phenotype relationship in vitro. Substrate topography and in analogy tissue architecture remains a cue that can and will be used to steer and understand cell function in vitro, which in turn can be applied in vivo, e.g. in optimizing tissue engineering applications.

Enhanced Osseointegration by the Hierarchical Micro-Nano Topography on Selective Laser Melting Ti-6Al-4V Dental Implants

Currently, selective laser melting (SLM) has been thriving in implant dentistry for on-demand fabricating dental implants. Based on the coarse microtopography of SLM titanium surfaces, constructing nanostructure to form the hierarchical micro-nano topography is effective in enhancing osseointegration. Given that current nanomodification techniques of SLM implants, such as anodization and hydrothermal treatment, are facing the inadequacy in costly specific apparatus and reagents, there has been no recognized nanomodified SLM dental implants. The present study aimed to construct hierarchical micro-nano topography on self-made SLM dental implants by a simple and safe inorganic chemical oxidation, and to evaluate its contribution on osteoblastic cells bioactivity and osseointegration. The surface chemical and physical parameters were characterized by FE-SEM, EDS, profilometer, AFM, and contact angle meter. The alteration on bioactivity of MG-63 human osteoblastic cells were detected by qRT-PCR. Then the osseointegration was assessed by implanting implants on the femur condyle of New Zealand Rabbits. The hierarchical micro-nano topography was constituted by the microrough surface of SLM implants and nanoneedles (diameter: 20∼50 nm, height: 150∼250 nm), after nanomodifying SLM implants in 30% hydrogen peroxide and 30% hydrochloride acid (volume ratio 1:2.5) at room temperature for 36 h. Low chemical impurities content and high hydrophilicity were observed in the nanomodified group. Cell experiments on the nanomodified group showed higher expression of mitophagy related gene (PINK1, PARKIN, LC3B, and LAMP1) at 5 days and higher expression of osteogenesis related gene (Runx2 and OCN) at 14 days. In the early stage of bone formation, the nanomodified SLM implants demonstrated higher bone-to-implant contact. Intriguingly, the initial bone-to-implant contact of nanomodified SLM implants consisted of more mineralized bone with less immature osteoid. After the cessation of bone formation, the bone-to-implant contact of nanomodified SLM implants was equal to untreated SLM implants and marketable TixOs implants. The overall findings indicated that the inorganic chemical oxidized hierarchical micro-nano topography could enhance the bioactivity of osteoblastic cells, and consequently promote the peri-implant bone formation and mineralization of SLM dental implants. This study sheds some light on improvements in additive manufactured dental implants.