Nanoscale Topographic Features Research Articles

Nanoengineered Polystyrene Surfaces with Nanopore Array Pattern Alters Cytoskeleton Organization and Enhances Induction of Neural Differentiation of Human Adipose-Derived Stem Cells.

Human adipose-derived stem cells (hADSCs) can differentiate into various cell types depending on chemical and topographical cues. One topographical cue recently noted to be successful in inducing differentiation is the nanoengineered polystyrene surface containing nanopore array-patterned substrate (NP substrate), which is designed to mimic the nanoscale topographical features of the extracellular matrix. In this study, efficacies of NP and flat substrates in inducing neural differentiation of hADSCs were examined by comparing their substrate-cell adhesion rates, filopodia growth, nuclei elongation, and expression of neural-specific markers. The polystyrene nano Petri dishes containing NP substrates were fabricated by a nano injection molding process using a nickel electroformed nano-mold insert (Diameter: 200 nm. Depth of pore: 500 nm. Center-to-center distance: 500 nm). Cytoskeleton and filopodia structures were observed by scanning electron microscopy and F-actin staining, while cell adhesion was tested by vinculin staining after 24 and 48 h of seeding. Expression of neural specific markers was examined by real-time quantitative polymerase chain reaction and immunocytochemistry. Results showed that NP substrates lead to greater substrate-cell adhesion, filopodia growth, nuclei elongation, and expression of neural specific markers compared to flat substrates. These results not only show the advantages of NP substrates, but they also suggest that further study into cell-substrate interactions may yield great benefits for biomaterial engineering.

Techniques for dental implant nanosurface modifications.

PURPOSEDental implant has gained clinical success over last decade with the major drawback related to osseointegration as properties of metal (Titanium) are different from human bone. Currently implant procedures include endosseous type of dental implants with nanoscale surface characteristics. The objective of this review article is to summarize the role of nanotopography on titanium dental implant surfaces in order to improve osseointegration and various techniques that can generate nanoscale topographic features to titanium implants.MATERIALS AND METHODSA systematic electronic search of English language peer reviewed dental literature was performed for articles published between December 1987 to January 2012. Search was conducted in Medline, PubMed and Google scholar supplemented by hand searching of selected journals. 101 articles were assigned to full text analysis. Articles were selected according to inclusion and exclusion criterion. All articles were screened according to inclusion standard. 39 articles were included in the analysis.RESULTSOut of 39 studies, seven studies demonstrated that bone implant contact increases with increase in surface roughness. Five studies showed comparative evaluation of techniques producing microtopography and nanotopography. Eight studies concluded that osteoblasts preferably adhere to nano structure as compared to smooth surface. Six studies illustrated that nanotopography modify implant surface and their properties. Thirteen studies described techniques to produce nano roughness.CONCLUSIONModification of dental osseous implants at nanoscale level produced by various techniques can alter biological responses that may improve osseointegration and dental implant procedures.

Titanium surface hydrophilicity enhances platelet activation.

Titanium implant surface modification is a key strategy used to enhance osseointegration. Platelets are the first cells that interact with the implant surface whereupon they release a wide array of proteins that influence the subsequent healing process. This study therefore investigated the effect of titanium surface modification on the attachment and activation of human platelets. The surface characteristics of three titanium surfaces: smooth (SMO), micro-rough (SLA) and hydrophilic micro-rough (SLActive) and the subsequent attachment and activation of platelets following exposure to these surfaces were determined. The SLActive surface showed the presence of significant nanoscale topographical features. While attached platelets appeared to be morphologically similar, significantly fewer platelets attached to the SLActive surface compared to both the SMO and SLA surfaces. The SLActive surface however induced the release of the higher levels of chemokines β-thromboglobulin and platelet factor 4 from platelets. This study shows that titanium surface topography and chemistry have a significant effect on platelet activation and chemokine release.

Facile Method for Large Scale Alignment of One Dimensional Nanoparticles and Control over Myoblast Orientation and Differentiation

A facile and robust method to align one-dimensional (1D) nanoparticles (NPs) in large scale has been developed. Using flow assembly, representative rod-like nanoparticles, including tobacco mosaic virus (TMV), gold nanorods, and bacteriophage M13, have been aligned inside glass tubes by controlling flow rate and substrate surface properties. The properties of 1D NPs, such as stiffness and aspect ratio, play a critical role in the alignment. Furthermore, these hierarchically organized structures can be used to support cell growth and control the cell orientation and morphology. When C2C12 myoblasts were cultured on surfaces coated with aligned TMV, we found that nanoscale topographic features were critical to guide the cell orientation and myogenic differentiation. This method can therefore be used in the fabrication of complex assemblies with 1D NPs and have wide applications in tissue engineering, sensing, electronics, and optical fields.

Accelerating the Development of Hippocampal Neurons using Nanopillar Structures

During the development of a neuron cell, multiple dendrites and a single axon, which have molecularly and functionally distinct domains, will generate from the soma to enable the directional communication between cells. The initiation and extension of such structures are critical to neuron development and neural circuit formation. In vitro neuron culture system has been a major model to study axon initiation and elongation, and many regulating genes have been identified in the in vitro model. However, only a few of the genes have been proven to be required in vivo, which may mainly due to the lack of extracellular cues in the in vitro model. The importance of extracellular cues to axon initiation and outgrowth is therefore emerging as a major theme in neural development. Nanostructures and nanomaterials serve as promising candidates to provide topographical cues to neuronal adhesion and development. Previous studies showed that neuron cells were able to sense nanoscale structures and responded differently in their neurite extension. In the present work, we use patterned nanopillar structures as controllable topographical cues to culture hippocampal neurons, and found that nanopillars have significant guidance effect on neurite outgrowth and elongation. More interestingly, the axon specification occurs in the first 12 hours after cell plating, which is much earlier than the usual time point for cells growing on normal flat surfaces. It indicated that the topographical cues can indeed accelerating neural development. We further studied this topographical influence on axon initiation and elongation by varying the diameter, height, pitch and shape of the nanopillars, and different effects were observed. This work will provide new insights on the role of topographical cues for neuronal development in vivo, as well as the possibility of using nanoscale topographic features to control neuronal development.

Nanotopography-Guided Migration of T Cells

T cells navigate a wide variety of tissues and organs for immune surveillance and effector functions. Although nanoscale topographical structures of extracellular matrices and stromal/endothelial cell surfaces in local tissues may guide the migration of T cells, there has been little opportunity to study how nanoscale topographical features affect T cell migration. In this study, we systematically investigated mechanisms of nanotopography-guided migration of T cells using nanoscale ridge/groove surfaces. The velocity and directionality of T cells on these nanostructured surfaces were quantitatively assessed with and without confinement, which is a key property of three-dimensional interstitial tissue spaces for leukocyte motility. Depending on the confinement, T cells exhibited different mechanisms for nanotopography-guided migration. Without confinement, actin polymerization-driven leading edge protrusion was guided toward the direction of nanogrooves via integrin-mediated adhesion. In contrast, T cells under confinement appeared to migrate along the direction of nanogrooves purely by mechanical effects, and integrin-mediated adhesion was dispensable. Therefore, surface nanotopography may play a prominent role in generating migratory patterns for T cells. Because the majority of cells in periphery migrate along the topography of extracellular matrices with much lower motility than T cells, nanotopography-guided migration of T cells would be an important strategy to efficiently perform cell-mediated immune responses by increasing chances of encountering other cells within a given amount of time.

Substratum Topography Modulates Corneal Fibroblast to Myofibroblast Transformation

The transition of corneal fibroblasts to the myofibroblast phenotype is known to be important in wound healing. The purpose of this study was to determine the effect of topographic cues on TGFβ-induced myofibroblast transformation of corneal cells. Rabbit corneal fibroblasts were cultured on nanopatterned surfaces having topographic features of varying sizes. Cells were cultured in media containing TGFβ at concentrations ranging from 0 to 10 ng/mL. RNA and protein were collected from cells cultured on topographically patterned and planar substrates and analyzed for the myofibroblast marker α-smooth muscle actin (αSMA) and Smad7 expression by quantitative real time PCR. Western blot and immunocytochemistry analysis for αSMA were also performed. Cells grown on patterned surfaces demonstrated significantly reduced levels of αSMA (P < 0.002) compared with planar surfaces when exposed to TGFβ; the greatest reduction was seen on the 1400 nm surface. Smad7 mRNA expression was significantly greater on all patterned surfaces exposed to TGFβ (P < 0.002), whereas cells grown on planar surfaces showed equal or reduced levels of Smad7. Western blot analysis and αSMA immunocytochemical staining demonstrated reduced transition to the myofibroblast phenotype on the 1400 nm surface when compared with cells on a planar surface. These data demonstrate that nanoscale topographic features modulate TGFβ-induced myofibroblast differentiation and αSMA expression, possibly through upregulation of Smad7. It is therefore proposed that in the wound environment, native nanotopographic cues assist in stabilizing the keratocyte/fibroblast phenotype while pathologic microenvironmental alterations may be permissive for increased myofibroblast differentiation and the development of fibrosis and corneal haze.

Topographical Control of Crystal Nucleation

Surface topography is here investigated as a route to controlling crystal nucleation. The nucleation from vapor of crystals of neo-pentanol and tetrabromomethane was studied on flat surfaces of glass and mica, and on identical substrates scratched with diamond powders of varying particle size. The result is a study which presents a systematic comparison of the nucleating ability of surfaces with the same chemistry and wettability, but varying surface topography. An increase in nucleation density of up to an order of magnitude was observed on scratched mica surfaces compared to unscratched ones, and there was a decrease in the induction time by up to 60%. Larger diamond particles led to enhanced effects, particularly on the nucleation density. Although the nucleation density and induction time on unscratched glass were similar to those on mica, the surface scratches on glass had no significant effect on nucleation density or induction time. The results suggest that a high density of nanoscale features of the surface topography, such as those produced as the diamond particles fracture the mica, is necessary for an enhancement of nucleation. The apparent length scale of the topographical features on mica is discussed with reference to classical nucleation theory and other models. These results show that both a quantitative reduction in induction time and an increase in nucleation density can be achieved as a result of mechanically produced topographical surface defects, which suggests that the engineering of nanoscale topographical features has real potential for control of heterogeneous nucleation.

Cell Adhesion on Nanotextured Slippery Superhydrophobic Substrates

In this work, the response of Saos2 cells to polymeric surfaces with different roughness/density of nanometric dots produced by a tailored plasma-etching process has been studied. Topographical features have been evaluated by atomic force microscopy, while wetting behavior, in terms of water-surface adhesion energy, has been evaluated by measurements of drop sliding angle. Saos2 cytocompatibility has been investigated by scanning electron microscopy, fluorescent microscopy, and optical microscopy. The similarity in outer chemical composition has allowed isolation of the impact of the topographical features on cellular behavior. The results indicate that Saos2 cells respond differently to surfaces with different nanoscale topographical features, clearly showing a certain inhibition in cell adhesion when the nanoscale is particularly small. This effect appears to be attenuated in surfaces with relatively bigger nanofeatures, though these express a more pronounced slippery/dry wetting character.

Biomechanical, histological and ultrastructural analyses of laser micro‐ and nano‐structured titanium implant after 6 months in rabbit

Short-term, experimental studies of partly laser-modified implants with nano-scale surface topographical features have recently shown a considerable increase in the biomechanical anchorage to bone. The aim of this study is to evaluate the biomechanical and bone-bonding ability of partly laser-modified implants compared with machined implants after a healing period of 6 months in a rabbit model. The results showed a 170% increase in removal torque. Histology and scanning electron microscopy demonstrated osseointegration for both implant types, but also revealed a different fracture pattern at the interface and in the bone. Transmission electron microscopy and chemical analysis showed coalescence between mineralized tissue and the nano-structured surface of the laser modified implant. Taken together, the results indicate that nano-structured surfaces promote in vivo long-term bone bonding and interface strength.

Nanoscale topography reduces fibroblast growth, focal adhesion size and migration-related gene expression on platinum surfaces

Controlling cellular responses on biomaterial surfaces is crucial in biomedical applications such as tissue engineering and implantable prosthetics. Since cells encounter various nanoscale topographic features in their natural environment, it has been postulated that surface nanotopography may be an alternative route to fabricate biomaterials with a desirable cellular response. In this framework, we investigated the responses of primary human fibroblasts to platinum substrates with different levels of surface roughness at the nanoscale. The nanorough surfaces were fabricated by using the glancing angle deposition technique (GLAD). We found that levels of cellular responses depended on the surface roughness and the size of the nanoscale features. We showed that in response to nanotopography cells spread less and have an elongated morphology, displaying signs of actin cytoskeleton impairment and reduced formation of focal adhesion complexes. Although cell growth and adhesion were impaired on the nanorough substrates, cell viability was not affected by topography. To a minor extent our results also indicate that cell migration might be reduced on the nanorough surfaces, since a significantly lower gene expression of migration related genes were found on the roughest surfaces as compared to the flat reference. The results presented here demonstrate that surface nanotopography influences fibroblasts responses on platinum, which may be used to reduce cellular adhesion on platinum implant surfaces such as implantable neural electrodes.

Layer-by-layer assembly of polysaccharide-based nanostructured surfaces containing polyelectrolyte complex nanoparticles

Nanoscale chemical and topographical features have been demonstrated to influence a variety of significant responses of mammalian cells to biomaterials surfaces. Thus, an important goal for biomaterials scientists is the ability to engineer the nanoscale surface features of biologically active materials. The goal of the current work is to demonstrate that polyelectrolyte complex nanoparticles (PCNs) in polyelectrolyte multilayers (PEMs) can be combined to create surfaces with controlled nanoscale surface topography and nanoscale presentation of surface chemistry. The polysaccharides used in this work are the biomedically relevant chitosan, heparin, and hyaluronan. Nanostructured surface coatings were characterized on both modified gold substrates and tissue-culture polystyrene surfaces. PCNs were adsorbed to oppositely charged PEMs, and were also embedded within PEMs. The construction of the surface coatings was characterized by quartz crystal microbalance with dissipation (QCM-D). The surface morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The chemistry of the coatings was confirmed by both X-ray photoelectron spectroscopy (XPS) and polarization modulation infra-red reflection absorption spectroscopy (PM-IRRAS). Morphologically, we found that PCNs were colloidally stable and homogeneously distributed when adsorbed on or in the PEMs. Chemical analysis confirms that the PCNs adsorbed to PEMs significantly altered the surface chemistry, indicating significant surface coverage. Furthermore, the position of the PCNs normal to the surface can be adjusted by adding PEMs on top of adsorbed PCNs. Thus, PCNs can be used to introduce discrete nanoscale surface topographical features and varying surface chemistry into PEM surface coatings in a controlled way.

Nanoscale Topography–Induced Modulation of Fundamental Cell Behaviors of Rabbit Corneal Keratocytes, Fibroblasts, and Myofibroblasts

Keratocyte-to-myofibroblast differentiation is a key factor in corneal wound healing. The purpose of this study was to determine the influence of environmental nanoscale topography on keratocyte, fibroblast, and myofibroblast cell behavior. Primary rabbit corneal keratocytes, fibroblasts, and myofibroblasts were seeded onto planar polyurethane surfaces with six patterned areas, composed of anisotropically ordered grooves and ridges with a 400-, 800-, 1200-, 1600-, 2000-, and 4000-nm pitch (pitch = groove + ridge width). After 24 hours cells were fixed, stained, imaged, and analyzed for cell shape and orientation. For migration studies, cells on each patterned surface were imaged every 10 minutes for 12 hours, and individual cell trajectories and migration rates were calculated. Keratocytes, fibroblasts, and myofibroblasts aligned and elongated to pitch sizes larger than 1000 nm. A lower limit to the topographic feature sizes that the cells responded to was identified for all three phenotypes, with a transition zone around the 800- to 1200-nm pitch size. Fibroblasts and myofibroblasts migrated parallel to surface ridges larger than 1000 nm but lacked directional guidance on submicron and nanoscale topographic features and on planar surfaces. Keratocytes remained essentially immobile. Corneal stromal cells elongated, aligned, and migrated, differentially guided by substratum topographic features. All cell types failed to respond to topographic features approximating the dimensions of individual stromal fibers. These findings contribute to our understanding of corneal stromal cell biology in health and disease and their interaction with biomaterials and their native extracellular matrix.

FILMPAR: A parallel algorithm designed for the efficient and accurate computation of thin film flow on functional surfaces containing micro-structure

FILMPAR is a highly efficient and portable parallel multigrid algorithm for solving a discretised form of the lubrication approximation to three-dimensional, gravity-driven, continuous thin film free-surface flow over substrates containing micro-scale topography. While generally applicable to problems involving heterogeneous and distributed features, for illustrative purposes the algorithm is benchmarked on a distributed memory IBM BlueGene/P computing platform for the case of flow over a single trench topography, enabling direct comparison with complementary experimental data and existing serial multigrid solutions. Parallel performance is assessed as a function of the number of processors employed and shown to lead to super-linear behaviour for the production of mesh-independent solutions. In addition, the approach is used to solve for the case of flow over a complex inter-connected topographical feature and a description provided of how FILMPAR could be adapted relatively simply to solve for a wider class of related thin film flow problems. Program summary Program title: FILMPAR Catalogue identifier: AEEL_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEEL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 530 421 No. of bytes in distributed program, including test data, etc.: 1 960 313 Distribution format: tar.gz Programming language: C++ and MPI Computer: Desktop, server Operating system: Unix/Linux Mac OS X Has the code been vectorised or parallelised?: Yes. Tested with up to 128 processors RAM: 512 MBytes Classification: 12 External routines: GNU C/C++, MPI Nature of problem: Thin film flows over functional substrates containing well-defined single and complex topographical features are of enormous significance, having a wide variety of engineering, industrial and physical applications. However, despite recent modelling advances, the accurate numerical solution of the equations governing such problems is still at a relatively early stage. Indeed, recent studies employing a simplifying long-wave approximation have shown that highly efficient numerical methods are necessary to solve the resulting lubrication equations in order to achieve the level of grid resolution required to accurately capture the effects of micro- and nano-scale topographical features. Solution method: A portable parallel multigrid algorithm has been developed for the above purpose, for the particular case of flow over submerged topographical features. Within the multigrid framework adopted, a W-cycle is used to accelerate convergence in respect of the time dependent nature of the problem, with relaxation sweeps performed using a fixed number of pre- and post-Red-Black Gauss–Seidel Newton iterations. In addition, the algorithm incorporates automatic adaptive time-stepping to avoid the computational expense associated with repeated time-step failure. Running time: 1.31 minutes using 128 processors on BlueGene/P with a problem size of over 16.7 million mesh points.

Nanopatterning via Pressure‐Induced Instabilities in Thin Polymer Films

Polymer thin films are the bedrock of modern electronic devices, playing key roles in their fabrication (photoresists) and operation (dielectrics, light emitting layers, sensor films, etc.). Consequently, enormous efforts have been devoted to understanding their fundamental properties and to pattern thin polymer films, especially now that the thickness of the films and the feature sizes are reaching molecular dimensions. The vast bulk of these studies has employed films at thermodynamical equilibrium, but as we will demonstrate here, non-annealed films containing residual stresses from the preparation of the films by spincasting can be harnessed in new patterning strategies. Nanoimprint lithography (NIL) is an extremely powerful technique for rapid largearea nanopatterning. [1,2] Thebasic principle involvesplacing a master with nanoscale topographic features on top of a thin polymer film, and subsequently heating the polymer film above the glass transitions temperature (Tg) while applying pressure, so that the polymerflows tofill therelief pattern ofthemaster.A thin residual layer usually remains beneath the master protrusions, which needs to be removed by a subsequent etching process before the pattern can be transferred into the substrate. Solvent-assisted NIL [3] unexpectedly resulted in pattern replication without any residual film between the features, due to dewetting of the plasticized film. Alternatively, films on completely non-wettable fluorinated surfaces break up during imprinting and heating, leading to individual polymer nano- and microstructures. [4] Scanning-probe lithography has been used extensively to produce nanostructures in self-assembled monolayers on gold by ‘shaving’ the chemisorbed alkanethiols. [5] Interestingly, residue-free nano- to micrometer-scale trenches were generated by scribing poly(3-hexylthiophene-2,5-diyl) (rr-P3HT) thin films with an AFM tip, presumably as a result of the release of residual strain in the films. [6] These examples

Diffusion Dynamics of Motor-Driven Transport: Gradient Production and Self-Organization of Surfaces

The interaction between cytoskeletal filaments (e.g., actin filaments) and molecular motors (e.g., myosin) is the basis for many aspects of cell motility and organization of the cell interior. In the in vitro motility assay (IVMA), cytoskeletal filaments are observed while being propelled by molecular motors adsorbed to artificial surfaces (e.g., in studies of motor function). Here we integrate ideas that cytoskeletal filaments may be used as nanoscale templates in nanopatterning with a novel approach for the production of surface gradients of biomolecules and nanoscale topographical features. The production of such gradients is challenging but of increasing interest (e.g., in cell biology). First, we show that myosin-induced actin filament sliding in the IVMA can be approximately described as persistent random motion with a diffusion coefficient (D) given by a relationship analogous to the Einstein equation (D = kT/gamma). In this relationship, the thermal energy (kT) and the drag coefficient (gamma) are substituted by a parameter related to the free-energy transduction by actomyosin and the actomyosin dissociation rate constant, respectively. We then demonstrate how the persistent random motion of actin filaments can be exploited in conceptually novel methods for the production of actin filament density gradients of predictable shapes. Because of regularly spaced binding sites (e.g., lysines and cysteines) the actin filaments act as suitable nanoscale scaffolds for other biomolecules (tested for fibronectin) or nanoparticles. This forms the basis for secondary chemical and topographical gradients with implications for cell biological studies and biosensing.

Bioinspired superhydrophobic poly(L‐lactic acid) surfaces control bone marrow derived cells adhesion and proliferation

The aptitude of a cell to adhere, migrate, and differentiate on a compact substrate or scaffold is important in the field of tissue engineering and biomaterials. It is well known that cell behavior can be controlled and guided through the change in micro- and nano-scale topographic features. In this work, we intend to demonstrate that special topographic features that control wettability may also have an important role in the biological performance of biodegradable substrates. Poly(L-lactic acid) surfaces with superhydrophobic characteristics were produced, based on the so-called Lotus effect, exhibiting dual micro- and nano-scale roughness. The water contact angle could be higher than 150 degrees and a value of that order could be kept even upon immersion in a simulated body fluid solution for more than 20 days. Such water repellent surfaces were found to prevent adhesion and proliferation of bone marrow derived cells previously isolated from the femurs of 6-week-old male Wistar rats, when compared with smoother surfaces prepared by simple solvent casting. Such results demonstrate that these superhydrophobic surfaces may be used to control cell behavior onto biodegradable substrates.

Neurite development in PC12 cells cultured on nanopillars and nanopores with sizes comparable with fi lopodia

We investigated the effect ofnanoscale topography on neurite development in pheochromocytoma (PC12 cells) by culturing the cells on substrates having nanoscale pillars and pores with sizes comparable with filipodia. We found that cells on nanopillars and nanopores developed fewer and shorter neurites than cells on smooth substrates, and that cells on nanopores developed more and longer neurites than cells on nanopillars. These results suggest that PC12 cells were spatially aware of the difference in the nanoscale structures of the underlying substrates and responded differently in their neurite extension. This finding points to the possibility of using nanoscale topographic features to control neurite development in neurons.

Nano- and Microscale Holes Modulate Cell-Substrate Adhesion, Cytoskeletal Organization, and $-\beta 1$ Integrin Localization in Sv40 Human Corneal Epithelial Cells

Human corneal epithelial cells (HCECs) interface with a basement membrane in vivo that possesses complex nanoscale topographic features. We report that synthetic substrates patterned with nano- and microscale holes differentially modulate the proliferation, shape and adhesion of SV40 human corneal epithelial cells (SV40-HCECs) as a function of feature size: 1) Cell proliferation was inhibited on nanoscale features (features size less than 800 nm in pitch) compared to microscale features or planar substrates in identical culture conditions. 2) Cells on nanoscale holes had a stellate morphology compared to those on microscale features that were more evenly spread. 3) Cells adhered more to nanoscale features than to microscale features when exposed to shear stress in a laminar flow chamber. Transmission electron microscopy showed that cells cultured on the 400 nm pitch patterns had longer and more numerous filopodia and retraction fibers than cells cultured on the 1600 nm pitch patterns. Immunogold labeling of -beta1 integrins revealed that these receptors were localized at the cell periphery and in the aforementioned cytoskeletal elements. Our findings indicate that surface discontinuities and the activation of mechanochemical cell signaling mechanisms may contribute to the observed responses exhibited by SV40-HCECs cultured on nano- and microscale topography.

Methods for Fabrication of Nanoscale Topography for Tissue Engineering Scaffolds

Observations of how controlling the microenvironment of cell cultures can lead to changes in a variety of parameters has lead investigators to begin studying how the nano-environment of a culture can affects cells. Cells have many structures at the nanoscale such as filipodia and cytoskeletal and membrane proteins that interact with the environment surrounding them. By using techniques that can control the nano-environment presented to a cell, investigators are beginning to be able to mimic the nanoscale topographical features presented to cells by extracellular matrix proteins such as collagen, which has precise and repeating nano-topography. The belief is that these nanoscale surface features are important to creating more natural cell growth and function. A number of techniques are currently being used to create nanoscale topographies for cell scaffolding. These techniques fall into two main categories: techniques that create ordered topographies and those that create unordered topographies. Electron Beam lithography and photo-lithography are two standard techniques for creating ordered features. Polymer demixing, phase separation, colloidal lithography and chemical etching are most typically used for creating unordered surface patterns. This review will give an overview of these techniques and cite observations from experiments carried out using them.