Surface Nanotopography Research Articles

Implementing Heterogeneous Crystal Surface Reactivity in Reactive Transport Simulations: The Example of Calcite Dissolution

Both surface reactivity and fluid dynamics control the dissolution kinetics of crystalline material. In this study, we performed a 3D reactive transport simulation to investigate the impact of surface topography heterogeneity superimposed to fluid transport heterogeneity on the dissolution rate of calcite. The model simulates the chemical reaction of calcite dissolution, solute transport, and crystal surface geometry evolution. Importantly, we introduce heterogeneous surface reactivity into the reactive transport simulation. We test the surface slope factor as a proxy value for the intrinsic surface reactivity of dissolving crystal surface nanotopographies. Experimental data sets collected using vertical scanning interferometry validate this approach. The novel parametrization allows for the simulation of surface-controlled heterogeneous reactivity in reactive transport simulations of mineral surface dissolution.

Efficient osteoblastic differentiation of human adipose-derived stem cells on TiO2 nanoparticles and metformin co-embedded electrospun composite nanofibers

In the present study, TiO2 nanoparticle (nTiO2) and metformin (MET)-co-embedded composite electrospun poly-ε-Caprolactone/gelatin nanofibers (PCL/GEL NFs) were developed as functional biomimetic scaffolds for improved osteoblastic differentiation of human adipose-derived stem cells (hADSCs). Morphological features and chemical configuration of fabricated electrospun fibers were characterized via FE-SEM, TEM, TGA, and FTIR. Improved mechanical properties were detected on the composite NFs due to the presence of inorganic particles, nTiO2. Besides, FE-SEM images and PicoGreen assay were demonstrated the enhanced adhesion and proliferation rate of hADSCs grown on the nTiO2/MET-loaded NFs, respectively. Moreover, a synergistic effects of nTiO2-generated surface nanotopography and the released MET led to a great capacity in the scaffold to induce differentiation toward osteoblasts via enhanced mineralization content and increased expression levels of osteoblastic markers. Overall, this preliminary work demonstrated the nanocomposite scaffold can be deemed as a strong potential candidate for bone tissue regeneration and engineering.

Importance of Surface Topography in Both Biological Activity and Catalysis of Nanomaterials: Can Catalysis by Design Guide Safe by Design?

It is acknowledged that the physicochemical properties of nanomaterials (NMs) have an impact on their toxicity and, eventually, their pathogenicity. These properties may include the NMs’ surface chemical composition, size, shape, surface charge, surface area, and surface coating with ligands (which can carry different functional groups as well as proteins). Nanotopography, defined as the specific surface features at the nanoscopic scale, is not widely acknowledged as an important physicochemical property. It is known that the size and shape of NMs determine their nanotopography which, in turn, determines their surface area and their active sites. Nanotopography may also influence the extent of dissolution of NMs and their ability to adsorb atoms and molecules such as proteins. Consequently, the surface atoms (due to their nanotopography) can influence the orientation of proteins as well as their denaturation. However, although it is of great importance, the role of surface topography (nanotopography) in nanotoxicity is not much considered. Many of the issues that relate to nanotopography have much in common with the fundamental principles underlying classic catalysis. Although these were developed over many decades, there have been recent important and remarkable improvements in the development and study of catalysts. These have been brought about by new techniques that have allowed for study at the nanoscopic scale. Furthermore, the issue of quantum confinement by nanosized particles is now seen as an important issue in studying nanoparticles (NPs). In catalysis, the manipulation of a surface to create active surface sites that enhance interactions with external molecules and atoms has much in common with the interaction of NP surfaces with proteins, viruses, and bacteria with the same active surface sites of NMs. By reviewing the role that surface nanotopography plays in defining many of the NMs’ surface properties, it reveals the need for its consideration as an important physicochemical property in descriptive and predictive toxicology. Through the manipulation of surface topography, and by using principles developed in catalysis, it may also be possible to make safe-by-design NMs with a reduction of the surface properties which contribute to their toxicity.

Development of Novel Dimpled Electrospun P(VDF‐TrFE) Nanofibers

AbstractElectrospun polymeric nanofibrous membranes find application in various fields such as biomedical, energy, defense, etc. The flexibility of the electrospinning process and various parameters like temperature, solvent volatility, and polymer nature helps to design nanofibers with desired properties. The wide range application of nanofibers is because of its large surface to volume ratio. The surface area of a nanofiber can be further increased by fabricating dimpled or porous fibers. In the present work, dimpled electrospun polyvinylidene fluoride‐co‐trifluoroethylene (P(VDF‐TrFE)) nanofibers are prepared. The surface nanotopography of the fiber is studied using SEM and TEM analysis. The influence of rough surface on the wettability is evaluated by contact angle analysis. The result indicates that the nanofibrous membrane exhibits a very high contact angle (140°). In addition to this, mechanical property and thermal behavior of the membrane are also studied. The study reveals that the dimpled electrospun nanofibrous membrane is an excellent candidate in various applications where a large surface area is required.

Interplay of mechanics and chemistry governs wear of diamond-like carbon coatings interacting with ZDDP-additivated lubricants

Friction and wear reduction by diamond-like carbon (DLC) in automotive applications can be affected by zinc-dialkyldithiophosphate (ZDDP), which is widely used in engine oils. Our experiments show that DLC’s tribological behaviour in ZDDP-additivated oils can be optimised by tailoring its stiffness, surface nano-topography and hydrogen content. An optimal combination of ultralow friction and negligible wear is achieved using hydrogen-free tetrahedral amorphous carbon (ta-C) with moderate hardness. Softer coatings exhibit similarly low wear and thin ZDDP-derived patchy tribofilms but higher friction. Conversely, harder ta-Cs undergo severe wear and sub-surface sulphur contamination. Contact-mechanics and quantum-chemical simulations reveal that shear combined with the high local contact pressure caused by the contact stiffness and average surface slope of hard ta-Cs favour ZDDP fragmentation and sulphur release. In absence of hydrogen, this is followed by local surface cold welding and sub-surface mechanical mixing of sulphur resulting in a decrease of yield stress and wear.

Cell Alignment Modulated by Surface Nano-Topography – Roles of Cell-Matrix and Cell-Cell Interactions

Cell alignment is critical in numerous areas, from tissue engineering to biohybrid robotics. Cell alignment is modulated through many features including surface topographies, mechanical cues from cell-matrix interactions, and cell-cell interactions. In this study, we present our approach to examine the role of surface topographies and cell-cell interactions with respect to cell alignment. We developed an approach to create wavy surface topographies at the nanometer size scale, which when integrated with cell culture affects cell alignment. Within a defined range of wavelengths and amplitudes of the surface topographies, cell alignment is dependent on culture confluency. This cell alignment’s dependence on confluency suggests that cell-cell interactions related to alignment may be correlated to cell-matrix interactions. Thus, we inhibited N-cadherin related cell-cell interactions through introduced anti-N-cadherin while culturing cells on our controlled surface topographies. We found that when using anti-N-cadherin, cells on patterned surfaces required greater confluency to achieve the same alignment to cell culture not in the presence of the antibody. Our results will be important in numerous areas including tissue repair, cell differentiation, and biohybrid systems.

Dissolution and sorption mechanisms at the aluminosilicate and carbonate mineral-AMD (Acid Mine Drainage) interface

Aluminosilicate/silicate and carbonate materials (pure and industrial) interacted with natural Acid Mine Drainage (AMD) under ambient conditions for different time periods in order to elucidate the chemical processes at the aluminosilicate and carbonate mineral-AMD interface. More precisely, powdered materials were subjected to macroscopic neutralization experiments (using on-line pH-measurements, Inductively Coupled Plasma Optical Emission Spectroscopy, Powder X-ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy), whereas interacted mm-sized single crystals were examined by means of nanoscale microscopic (in-situ Atomic Force Microscopy) and surface & bulk spectroscopic techniques (X-ray Photoelectron Spectroscopy, 12C-Rutherford Backscattering Spectroscopy, Solid-State 29Si and 27Al Magic-Angle-Spinning Nuclear Magnetic Resonance). The carbonates were proven to be more effective for neutralization of AMD, related to adequate removal of metals from the contaminated aqueous medium, but they are readily dissolved. The application of aluminosilicate/silicates showed that the removal of metals is considerably lower, and the pH stabilized at lower values, but they are more resistant. The investigation of interacted zeolite and calcite crystals revealed changes to the macrotopography, microtopography and nanotopography of surfaces. It was indicated that coupled dissolution and sorption (surface precipitation/co-precipitation, nucleation/crystal growth, adsorption or even absorption-including solid-state diffusion) phenomena occur simultaneously. Based on the experimental results, two generalized models -in nano(molecular)-scale- can be suggested regarding interaction of AMD with aluminosilicate and carbonate mineral surfaces.

Nano-Topographical Control of Ti-Nb-Zr Alloy Surfaces for Enhanced Osteoblastic Response.

Nano-scale surface roughening of metallic bio-implants plays an important role in the clinical success of hard tissue reconstruction and replacement. In this study, the nano-topographical features of titanium-niobium-zirconium (TNZ) alloy surfaces were controlled by using the target-ion induced plasma sputtering (TIPS) technique to improve the in vitro osteoblastic response. The TIPS technique is a novel strategy for etching the surface of metallic bio-implants using bombardment of target metal cations, which were accelerated by an extremely high negative bias voltage applied to the substrates. The nano-topography of the TNZ surfaces was successfully controlled by modulating experimental variables (such as the ion etching energy and the type of substrate or target materials) of TIPS. As a result, various nanopatterns (size: 10–210 nm) were fabricated on the surface of the TNZ alloys. Compared with the control group, experimental groups with nanopattern widths of ≥130 nm (130 and 210 nm groups) exhibited superior cell adhesion, proliferation, and differentiation. Our findings demonstrate that TIPS is a promising technology that can impart excellent biological functions to the surface of metallic bio-implants.

Rebirth of the Eggshell Membrane as a Bioactive Nanoscaffold for Tissue Engineering.

Eggshell membrane (ESM)-based biomaterials have generated significant interest for their potential biomedical applications, including those in tissue engineering and regenerative medicine. Herein, the development of a bioactive ESM-based nanopatterned scaffold for enhancing the adhesion and functions of cells has been described. To control the shape of the raw ESM with entangled protein fibers, a two-step dissolution technique is used. Subsequently, nanoimprint lithography is applied to the ESM solution to fabricate scaffolds with a nanotopographic surface inspired by the fiber alignment of the extracellular matrix. In this way, the morphology and proliferation of attached osteoblasts are sensitively controlled through their response to the nanopatterned topography of the prepared scaffold, allowing significant improvements in their osteogenic differentiation and growth factor secretion. This study demonstrates the potential use of this bioactive ESM-based nanopatterned substrate as an effective cell and tissue engineering scaffold.

Microscopic Characterization of Bioactivate Implant Surfaces: Increasing Wettability Using Salts and Dry Technology.

The surface topography of dental implants plays an important role in cell-surface interaction promoting cell adhesion, proliferation and differentiation influencing osseointegration. A hydrophilic implant leads to the absorption of water molecules and subsequently promotes the adhesion of cells to the implant binding protein. Dried salts on the implant surfaces allow one to store the implant surfaces in a dry environment while preserving their hydrophilic characteristics. This process has been identified as “dry technology”. The aim of the present study is to describe from a micrometric and nanometric point of view the characteristics of this new bioactivated surface obtained using salts dried on the surface. Topographic analysis, energy-dispersive X-ray spectroscopy, and contact angle characterization were performed on the samples of a sandblasted and dual acid-etched surface (ABT), a nanosurface (Nano) deriving from the former but with the adding of salts air dried and a nanosurface with salts dissolved with distilled water (Nano H2O). The analysis revealed promising results for nanostructured surfaces with increased wettability and a more articulated surface nanotopography than the traditional ABT surface. In conclusion, this study validates a new promising ultra-hydrophilic nano surface obtained by sandblasting, double acid etching and surface salt deposition using dry technology.

A Brief Review on the Evolution of Metallic Dental Implants: History, Design, and Application

In recent years, significant advances in the field of medical materials have begun to emerge, especially in nanotechnology. The modern area of nanostructured implants possesses wide applications in various medical implants including their dental use. Nano-surface functions present substantial resolutions to medical obstacles through improved biomaterial proficiency, innovative dental-implant designs, and surface design procedures, such as nanoscale adhesive surfaces, bio-chemical anodization, and surface modification technique. This work covers dental implant history, nanotechnological advances, and its development that includes a description, basic properties, and the related results of composites and surface morphology, and the different types of nanomaterials used in dental implants. Significant attempts have been made over the last few decades to strengthen osteointegration and prevent bacterial attachment to the implant surfaces. The micro and nano-topography of the hierarchical surface orchestrate the biological reactions of implants and may solve the problems associated with implant-tissue issues. This research investigates the implant articles from 1964 to 2021, which offers a brief description of the nanostructured biomaterials to enhance dental implants’ performance and may open new frontiers in the advancement of implant technology.

Influence of Muscovite (001) Surface Nanotopography on Radionuclide Adsorption Studied by Kinetic Monte Carlo Simulations

Mechanistic understanding and prediction of solute adsorption from fluids onto mineral surfaces is relevant for many natural and technical processes. Mineral surfaces in natural systems are often exposed to fluids at non-equilibrium conditions resulting in surface dissolution reactions. Such reactions cause the formation of surface nanotopography and, consequently, the exposure of different types of surface atoms. The quantitative effect of nanotopography on the efficiency of adsorption reactions at crystal surfaces is not known. Using kinetic Monte Carlo simulations, we combined a model of muscovite (001) face dissolution with a consequent model of radionuclide adsorption on the rough mineral surface. The model considers three different adsorption sites based on the muscovite surface cations: silicon, tetrahedral, and octahedral aluminum. Two different nanotopography configurations are investigated, both showing similar adsorption behavior. Octahedral aluminum surface atoms defined by having the highest reactivity toward adsorption are exposed solely on steps and pits on the muscovite (001) face. Thus, their availability directly depends on the surface nanotopography. The model results show the need for a more precise parameterization of surface site-specific adsorption, taking into account the coordination of the involved surface cation such as kink, step, or terrace sites.

Greater Osseointegration Potential with Nanostructured Surfaces on TiZr: Accelerated vs. Real-Time Ageing.

Surface chemistry and nanotopography of dental implants can have a substantial impact on osseointegration. The aim of this investigation was to evaluate the effects of surface chemistry and nanotopography on the osseointegration of titanium-zirconium (TiZr; Roxolid®) discs, using a biomechanical pull-out model in rabbits. Two discs each were placed in both the right and left tibiae of 16 rabbits. Five groups of sandblasted acid etched (SLA) discs were tested: (1) hydrophobic without nanostructures (dry/micro) (n = 13); (2) hydrophobic with nanostructures, accelerated aged (dry/nano/AA) (n = 12); (3) hydrophilic without nanostructures (wet/micro) (n = 13); (4) hydrophilic with nanostructures, accelerated aged (wet/nano/AA; SLActive®) (n = 13); (5) hydrophilic with nanostructures, real-time aged (wet/nano/RTA). The animals were sacrificed after four weeks and the biomechanical pull-out force required to remove the discs was evaluated. Adjusted mean pull-out force was greatest for group wet/nano/RTA (64.5 ± 17.7 N) and lowest for group dry/micro (33.8 ± 10.7 N). Multivariate mixed model analysis showed that the pull-out force was significantly greater for all other disc types compared to the dry/micro group. Surface chemistry and topography both had a significant effect on pull-out force (p < 0.0001 for both), but the effect of the interaction between chemistry and topography was not significant (p = 0.1056). The introduction of nanostructures on the TiZr surface significantly increases osseointegration. The introduction of hydrophilicity to the TiZr implant surface significantly increases the capacity for osseointegration, irrespective of the presence or absence of nanotopography.

Recent Advances in Promoting Chondrogenesis of Human Mesenchymal Stem Cells Using Physically and Chemically Modified Hydrogels

Tissue engineering strategies for regenerating damaged cartilage using hydrogels have garnered significant attention due to the limited self-healing capacity of damaged cartilage tissue and the restrictions of current medical treatment methods. In particular, using human mesenchymal stem cells (hMSCs) as the cell source has shown the potential to differentiate along a chondrogenic lineage. Hydrogels, whether made of synthetic polymers, natural polymers, or combinations, are widely explored as scaffolding materials mimicking the natural cartilage environment. Based on the understanding of the importance of surface nanotopographies and mechanical stiffness, hydrogels have been presented in various forms and tested for the differentiation of hMSCs. The primary focus of this review is to provide a summary of recent advances in physically and chemically modified hydrogels promoting the chondrogenesis of hMSCs. Advances in micromachining have helped in forming surfaces with the required roughness or an array of micropillars of defined architecture. Hydrogels have been combined with various stimulants such as small peptides, growth factors, and many modified matrix elements. Creating anisotropic hydrogels mimicking the extracellular matrix of cartilage has also been reported. These studies show promising results and identify a niche for in-vitro differentiation of chondrocytes from hMSCs.

Industrially scalable surface treatments to enhance the current density output from graphite bioanodes fueled by real domestic wastewater

SummaryAcid and electrochemical surface treatments of graphite electrode, used individually or in combination, significantly improved the microbial anode current production, by +17% to +56%, in well-regulated and duplicated electroanalytical experimental systems.Of all the consequences induced by surface treatments, the modifications of the surface nano-topography preferentially justify an improvement in the fixation of bacteria, and an increase of the specific surface area and the electrochemically accessible surface of graphite electrodes, which are at the origin of the higher performances of the bioanodes supplied with domestic wastewater. The evolution of the chemical composition and the appearance of C-O, C=O, and O=C-O groups on the graphite surface created by combining acid and electrochemical treatments was prejudicial to the formation of efficient domestic-wastewater-oxidizing bioanodes. The comparative discussion, focused on the positioning of the performances, shows the industrial interest of applying the surface treatment method to the world of bioelectrochemical systems.

Engineered Nanotopography on the Microfibers of 3D-Printed PCL Scaffolds to Modulate Cellular Responses and Establish an In Vitro Tumor Model.

Scaffold-based three-dimensional (3D) cell culture systems have gained increased interest in cell biology, tissue engineering, and drug screening fields as a replacement of two-dimensional (2D) monolayer cell culture and as a way to provide biomimetic extracellular matrix environments. In this study, microscale fibrous scaffolds were fabricated via electrohydrodynamic printing, and nanoscale features were created on the fiber surface by simply leaching gliadin of poly(ε-caprolactone) (PCL)/gliadin composites in ethanol solution. The microstructure of the printed scaffolds could be precisely controlled by printing parameters, and the surface nanotopography of the printed fiber could be tuned by varying the PCL/gliadin ratios. By seeding mouse embryonic fibroblast (NIH/3T3) cells and human nonsmall cell lung cancer (A549) cells on the printed scaffolds, the cellular responses showed that the fiber nanotopography on printed scaffolds efficiently favored cell adhesion, migration, proliferation, and tissue formation. Quantitative analysis of the transcript expression levels of A549 cells seeded on nanoporous scaffolds further revealed the upregulation of integrin-β1, focal adhesion kinase, Ki-67, E-cadherin, and epithelial growth factor receptors over what was observed in the cells grown on the pure PCL scaffold. Furthermore, a significant difference was found in the relevant biomarker expression on the developed scaffolds compared with that in the monolayer culture, demonstrating the potential of cancer cell-seeded scaffolds as 3D in vitro tumor models for cancer research and drug screening.

Micropatterning of Substrates for the Culture of Cell Networks by Stencil-Assisted Additive Nanofabrication.

The fabrication of in vitro neuronal cell networks where cells are chemically or electrically connected to form functional circuits with useful properties is of great interest. Standard cell culture substrates provide ensembles of cells that scarcely reproduce physiological structures since their spatial organization and connectivity cannot be controlled. Supersonic Cluster Beam Deposition (SCBD) has been used as an effective additive method for the large-scale fabrication of interfaces with extracellular matrix-mimicking surface nanotopography and reproducible morphological properties for cell culture. Due to the high collimation of SCBD, it is possible to exploit stencil masks for the fabrication of patterned films and reproduce features as small as tens of micrometers. Here, we present a protocol to fabricate micropatterned cell culture substrates based on the deposition of nanostructured cluster-assembled zirconia films by stencil-assisted SCBD. The effectiveness of this approach is demonstrated by the fabrication of micrometric patterns able to confine primary astrocytes. Calcium waves propagating in the astrocyte networks are shown.

Blood-Compatible Materials: Vascular Endothelium-Mimetic Surfaces that Mitigate Multiple Cell-Material Interactions.

When flowing whole blood contacts medical device surfaces, the most common blood-material interactions result in coagulation, inflammation, and infection. Many new blood-contacting biomaterials have been proposed based on strategies that address just one of these common modes of failure. This study proposes to mitigate unfavorable biological reactions that occur with blood-contacting medical devices by designing multifunctional surfaces, with features optimized to meet multiple performance criteria. These multifunctional surfaces incorporate the release of the small molecule hormone nitric oxide (NO) with surface chemistry and nanotopography that mimic features of the vascular endothelial glycocalyx. These multifunctional surfaces have features that interact with coagulation components, inflammatory cells, and bacterial cells. While a single surface feature alone may not be sufficient to achieve multiple functions, the release of NO from the surfaces along with their modification to mimic the endothelial glycocalyx synergistically improves platelet-, leukocyte-, and bacteria-surface interactions. This work demonstrates that new blood-compatible materials should be designed with multiple features, to better address the multiple modes of failure of blood-contacting medical devices.

Physicochemical properties of anodized-hydrothermally treated titanium with a nanotopographic surface structure promote osteogenic differentiation in dental pulp stem cells

Purpose Implants made of anodized-hydrothermally treated commercially pure titanium with a nanotopographic surface structure (SA-treated c.p.Ti) may advantageously promote contact osteogenesis during the early stages of healing. We hypothesized that utilizing SA-treated c.p.Ti with dental pulp stem cells (DPSCs) might improve osteoconduction during the process of osseointegration. This in vitro study investigated the effect of initial adhesion of DPSCs to SA-treated c.p.Ti compared with conventional c.p.Ti and anodic oxide (AO) c.p.Ti.Methods DPSCs were obtained from the mandibular incisors of Sprague-Dawley rats and cultured without osteogenic induction medium on c.p.Ti, AO c.p.Ti, and SA-treated c.p.Ti disks for up to 14 days. The morphology, proliferation, and differentiation of DPSCs were assessed by scanning electron microscopy, an MTT assay, and Alizarin Red S staining, respectively. A real-time quantitative polymerase chain reaction was used to quantify the mRNA expression of osteocalcin, osteopontin, and bone sialoprotein.Results On all disks, the DPSCs appeared flattened with the formation of extensions over time. The filopodium-like extensions were closely bound to the SA-treated c.p.Ti surface. The proliferation of DPSCs was not significantly different among the c.p.Ti treatments. However, DPSCs on SA-treated c.p.Ti showed the greatest mRNA levels of osteopontin, osteocalcin, and bone sialoprotein, as well as increased Alizarin Red S staining.Conclusions The results of the present in vitro study demonstrate that the surface properties of SA-treated c.p.Ti disks enhance osteogenic differentiation of DPSCs and may facilitate mineralized matrix formation on SA-treated c.p.Ti implant surfaces, which can enhance early bone regeneration.

Electrospun Fiber Scaffolds for Engineering Glial Cell Behavior to Promote Neural Regeneration.

Electrospinning is a fabrication technique used to produce nano- or micro- diameter fibers to generate biocompatible, biodegradable scaffolds for tissue engineering applications. Electrospun fiber scaffolds are advantageous for neural regeneration because they mimic the structure of the nervous system extracellular matrix and provide contact guidance for regenerating axons. Glia are non-neuronal regulatory cells that maintain homeostasis in the healthy nervous system and regulate regeneration in the injured nervous system. Electrospun fiber scaffolds offer a wide range of characteristics, such as fiber alignment, diameter, surface nanotopography, and surface chemistry that can be engineered to achieve a desired glial cell response to injury. Further, electrospun fibers can be loaded with drugs, nucleic acids, or proteins to provide the local, sustained release of such therapeutics to alter glial cell phenotype to better support regeneration. This review provides the first comprehensive overview of how electrospun fiber alignment, diameter, surface nanotopography, surface functionalization, and therapeutic delivery affect Schwann cells in the peripheral nervous system and astrocytes, oligodendrocytes, and microglia in the central nervous system both in vitro and in vivo. The information presented can be used to design and optimize electrospun fiber scaffolds to target glial cell response to mitigate nervous system injury and improve regeneration.