Fibroblast anchorage to microtextured surfaces

Reducing Cancer Cell Adhesion using Microtextured Surfaces

For the past century, trypsin has been the primary method of cell dissociation, largely without any major changes to the process. Enzymatic cell detachment strategies for large-scale cell culturing processes are popular but can be labor-intensive, potentially lead to the accumulation of genetic mutations, and produce large quantities of liquid waste. Therefore, engineering surfaces to lower cell adhesion strength could enable the next generation of cell culture surfaces for delicate primary cells and automated, high-throughput workflows. In this study, a process for creating microtextured polystyrene (PS) surfaces to measure the impact of microposts on the adhesion strength of cells is developed. Cell viability and proliferation assays show comparable results in two cancer cell lines between micropost surfaces and standard cell culture vessels. However, cell image analysis on microposts reveals that cell area decreases by half, and leads to an average twofold increase in cell length per area. Using a microfluidic-based method up to a seven times greater percentage of cells are removed from micropost surfaces than the flat control surfaces. These results show that micropost surfaces enable decreased cell adhesion strength while maintaining similar cell viabilities and proliferation as compared to flat PS surfaces.

Effect of Fibronectin-Coated Micro-Grooved Titanium Surface on Alignment, Adhesion, and Proliferation of Human Gingival Fibroblasts

Background

Surface characters of culture plates affect cellular behaviors such as cellular alignment and elongation. Microgrooves guide the cell growth along the grooves and spread. The aim of this study was to observe the effect of fibronectin (FN)-coated micro-grooved titanium plates on the alignment, spread, adhesion, and proliferation of human gingival fibroblasts (HGFs).

Material/Methods

Micro-grooved titanium plates were fabricated, and FN was immobilized onto the micro-grooved surfaces using silanization. HGFs were cultured on the smoothed or micro-grooved (with 35 μm width, 15 μm bridge, 10 μm depth) titanium plates, with or without the FN coating. We assessed the water contact angle and blood compatibility of the surfaces, and the earlier adhesion, adhesion strength, proliferation and morphology of the cells growing on the different titanium surfaces.

Results

The results revealed that the blood hemolysis rates of different titanium surfaces were within the safety limits. HGFs aligned along the grooves, spread out more evidently, and showed significantly more adhesion in the FN-coated micro-grooved surface compared with other surfaces (p<0.05).

Conclusions

The micro-grooved surface coated with FN guides the HGFs to align along the grooves, and promotes cell spread, adhesion and proliferation, which might be used to improve the efficacy of dental implants.

Nanoscale physicochemical properties of chain- and step-growth polymerized PEG hydrogels affect cell-material interactions

Poly(ethylene glycol) (PEG) hydrogels provide a versatile platform to develop cell instructive materials through incorporation of a variety of cell adhesive ligands and degradable chemistries. Synthesis of PEG gels can be accomplished via two mechanisms: chain and step growth polymerizations. The mechanism dramatically impacts hydrogel nanostructure, whereby chain polymerized hydrogels are highly heterogeneous and step growth networks exhibit more uniform structures. Underpinning these alterations in nanostructure of chain polymerized hydrogels are densely-packed hydrophobic poly(methyl methacrylate) or poly(acrylate) kinetic chains between hydrophilic PEG crosslinkers. As cell-material interactions, such as those mediated by integrins, occur at the nanoscale and affect cell behavior, it is important to understand how different modes of polymerization translate into nanoscale mechanical and hydrophobic heterogeneities of hydrogels. Therefore, chain- and step-growth polymerized PEG hydrogels with macroscopically similar macromers and compliance (for example, methacrylate-functionalized PEG (PEGDM), M_W  = 10 kDa and norbornene-functionalized 4-arm PEG (PEGnorb), M_W  = 10 kDa) were used to examine potential nanoscale differences in hydrogel mechanics and hydrophobicity using atomic force microscopy (AFM). It was found that chain-growth polymerized network yielded greater heterogeneities in both stiffness and hydrophobicity as compared to step-growth polymerized networks. These nanoscale heterogeneities impact cell-material interactions, particularly human mesenchymal stem cell (hMSC) adhesion and spreading, which has implications in use of these hydrogels for tissue engineering applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1112-1122, 2017.

Exploring the Limits of Cell Adhesion under Shear Stress within Physiological Conditions and beyond on a Chip

Cell adhesion processes are of ubiquitous importance for biomedical applications such as optimization of implant materials. Here, not only physiological conditions such as temperature or pH, but also topographical structures play crucial roles, as inflammatory reactions after surgery can diminish osseointegration. In this study, we systematically investigate cell adhesion under static, dynamic and physiologically relevant conditions employing a lab-on-a-chip system. We screen adhesion of the bone osteosarcoma cell line SaOs-2 on a titanium implant material for pH and temperature values in the physiological range and beyond, to explore the limits of cell adhesion, e.g., for feverish and acidic conditions. A detailed study of different surface roughness R_q gives insight into the correlation between the cells’ abilities to adhere and withstand shear flow and the topography of the substrates, finding a local optimum at R_q = 22 nm. We use shear stress induced by acoustic streaming to determine a measure for the ability of cell adhesion under an external force for various conditions. We find an optimum of cell adhesion for T = 37 °C and pH = 7.4 with decreasing cell adhesion outside the physiological range, especially for high T and low pH. We find constant detachment rates in the physiological regime, but this behavior tends to collapse at the limits of 41 °C and pH 4.

In vitro preliminary study of osteoblast response to surface roughness of titanium discs and topical application of melatonin

Objectives: To observe human osteoblast behavior cultured in vitro on titanium discs (Ti) in relation to surface roughness and melatonin application. Study Design: Human osteoblasts (MG-63) were cultured on 60 Ti6Al4V discs divided into three groups: Group I: discs treated with dual acid etching; Group II dual acid etching and blasting with calcium phosphate particles; Group III (control) machined discs. Surface roughness and topography of the discs were examined with scanning electron microscope (SEM) and confocal laser scanning electron microscope( CLSM). Osteoblast adhesion, proliferation and cell morphology were determined by means of fluorescence microscopy with Image-Pro Plus software and SEM. Results: Group II presented the roughest discs, while the least rough were Group III. Cell adhesion was greatest in Group II. The addition of melatonin improved cell proliferation. Conclusions: 1. Surface treatments (dual acid etching, calcium phosphate impaction) increase surface roughness in comparison with machined titanium. 2. Greater surface roughness tends to favor cell adhesion after 24-hour cell culture. 3. The addition of melatonin tends to favor osteoblast proliferation.

Key words:Osteoblasts, titanium, roughness, melatonin, dental implants, osseointegration.

The electrode-tissue interface: the revolutionary role of steroid-elution

The electrode-tissue interface is that area lying between the cathode of a low-voltage implantable pacemaker or cardioverter-defibrillator (ICD) lead and the endocardium or epi-myocardium of the cardiac chamber being paced. The electrical stimulus that is delivered to this interface is responsible for myocyte depolarization with consequent cardiac contraction. The process by which this occurs is reasonably well understood and any explanation requires a basic understanding of the physics and cellular electrophysiology of pacing. The effective and efficient delivery of electrical energy to the myocardium via the lead is dependent on many factors to be discussed in this review. However, despite numerous evolutionary changes occurring in the cathode's material, design, and surface configuration, it was not until the incorporation of steroid-elution to the electrode-tissue interface that reliable and significantly low stimulation threshold cardiac pacing became possible.

Differential Behavior of Fibroblasts and Epithelial Cells on Structured Implant Abutment Materials: A Comparison of Materials and Surface Topographies

PURPOSE

The aim of this study was to compare the proliferation and attachment behavior of fibroblasts and epithelial cells on differently structured abutment materials.

MATERIALS AND METHODS

Three different surface topographies were prepared on zirconia and titanium alloy specimens and defined as follows: machined (as delivered without further surface modification), smooth (polished), and rough (sandblasted). Energy-dispersive X-ray spectroscopy, topographical analysis, and water contact angle measurements were used to analyze the surface properties. Fibroblasts (HGF1) and epithelial cells (HNEpC) grown on the specimens were investigated 24 hours and 72 hours after seeding and counted using fluorescence imaging. To investigate adhesion, the abundance and arrangement of the focal adhesion protein vinculin were evaluated by immunocytochemistry.

RESULTS

Similar surface topographies were created on both materials. Fibroblasts exhibited significant higher proliferation rates on comparable surface topographies of zirconia compared with the titanium alloy. The proliferation of fibroblasts and epithelial cells was optimal on different substrate/topography combinations. Cell spreading was generally higher on polished and machined surfaces than on sandblasted surfaces. Rough surfaces provided favorable properties in terms of cellular adhesion of fibroblasts but not of epithelial cells.

CONCLUSIONS

Our data support complex soft tissue cell-substrate interactions: the fibroblast and epithelial cell response is influenced by both the material and surface topography.

Microfabricated biomaterials for engineering 3D tissues

Mimicking natural tissue structure is crucial for engineered tissues with intended applications ranging from regenerative medicine to biorobotics. Native tissues are highly organized at the microscale, thus making these natural characteristics an integral part of creating effective biomimetic tissue structures. There exists a growing appreciation that the incorporation of similar highly organized microscale structures in tissue engineering may yield a remedy for problems ranging from vascularization to cell function control/determination. In this review, we highlight the recent progress in the field of microscale tissue engineering and discuss the use of various biomaterials for generating engineered tissue structures with microscale features. In particular, we will discuss the use of microscale approaches to engineer the architecture of scaffolds, generate artificial vasculature, and control cellular orientation and differentiation. In addition, the emergence of microfabricated tissue units and the modular assembly to emulate hierarchical tissues will be discussed.

Engineering skeletal muscle tissue--new perspectives in vitro and in vivo

Muscle tissue engineering (TE) has not yet been clinically applied because of several problems. However, the field of skeletal muscle TE has been developing tremendously and new approaches and techniques have emerged. This review will highlight recent developments in the field of nanotechnology, especially electrospun nanofibre matrices, as well as potential cell sources for muscle TE. Important developments in cardiac muscle TE and clinical studies on Duchenne muscular dystrophy (DMD) will be included to show their implications on skeletal muscle TE.

Three-dimensional plotted scaffolds with controlled pore size gradients: Effect of scaffold geometry on mechanical performance and cell seeding efficiency

Scaffolds produced by rapid prototyping (RP) techniques have proved their value for tissue engineering applications, due to their ability to produce predetermined forms and structures featuring fully interconnected pore architectures. Nevertheless, low cell seeding efficiency and non-uniform distribution of cells remain major limitations when using such types of scaffold. This can be mainly attributed to the inadequate pore architecture of scaffolds produced by RP and the limited efficiency of cell seeding techniques normally adopted. In this study we aimed at producing scaffolds with pore size gradients to enhance cell seeding efficiency and control the spatial organization of cells within the scaffold. Scaffolds based on blends of starch with poly(ε-caprolactone) featuring both homogeneously spaced pores (based on pore sizes of 0.75 and 0.1 mm) and pore size gradients (based on pore sizes of 0.1-0.75-0.1 and 0.75-0.1-0.75 mm) were designed and produced by three-dimensional plotting. The mechanical performance of the scaffolds was characterized using dynamic mechanical analysis (DMA) and conventional compression testing under wet conditions and subsequently characterized using scanning electron microscopy and micro-computed tomography. Osteoblast-like cells were seeded onto such scaffolds to investigate cell seeding efficiency and the ability to control the zonal distribution of cells upon seeding. Scaffolds featuring continuous pore size gradients were originally produced. These scaffolds were shown to have intermediate mechanical and morphological properties compared with homogenous pore size scaffolds. The pore size gradient scaffolds improved seeding efficiency from ∼35% in homogeneous scaffolds to ∼70% under static culture conditions. Fluorescence images of cross-sections of the scaffolds revealed that scaffolds with pore size gradients induce a more homogeneous distribution of cells within the scaffold.

Microfluidics: a new cosset for neurobiology

Recently, microfluidic systems have shown great potential in the study of molecular and cellular biology. With its excellent properties, such as miniaturization, integration and automation, to name just a few, microfluidics creates new opportunities for the spatial and temporal control of cell growth and environmental stimuli in vitro. In the field of neuroscience, microfluidic devices offer precise control of the microenvironment surrounding individual cells, and the delivery of biochemical or physical cues to neural networks or single neurons. The intent of this review is to outline recent advances in microfluidic-based applications in neurobiology, with emphasis on neuron culture, neuron manipulation, neural stem cell differentiation, neuropharmacology, neuroelectrophysiology, and neuron biosensors. It also aims to stimulate development of microfluidic-based applications in neurobiology by involving scientists from various disciplines, especially neurobiology and microtechnology.

Biomaterials in orthopaedics

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

Effects of nano-surface properties on initial osteoblast adhesion and Ca/P adsorption ability for titanium alloys

Titanium alloys (Ti6Al4V), while subjected to high temperature surface treatment, experience altered nano-surface characteristics. The effects of such surface treatments are examined, including the initial adhesion force experienced by osteoblasts, the Ca/P adsorption capability, and the nano-surface properties, including the amounts of amphoteric Ti-OH groups, surface topography, and surface roughness. The initial adhesion force is considered a quantitative indicator of cyto-compatibility in vitro. Previously, a cyto-detacher was applied in a pioneer attempt measuring the initial adhesion force of fibroblasts on a metal surface. Presently, the cyto-detacher is further applied to evaluate the initial adhesion force of osteoblasts. Results reveal that (1) titanium alloys subjected to heat treatment could promote the adsorption capability of Ca and P; (2) titanium alloys subjected to heat treatment could have higher initial osteoblast adhesion forces; (3) the adhesion strength of osteoblasts, ranging from 38.5 to 58.9 nN (nanonewtons), appears stronger for rougher surfaces. It is concluded that the heat treatment could have impacted the biocompatibility in terms of the initial osteoblast adhesion force and Ca/P adsorption capability.

Transmission electron microscopy study of the cell-sensor interface

An emerging number of micro- and nanoelectronics-based biosensors have been developed for non-invasive recordings of physiological cellular activity. The interface between the biological system and the electronic devices strongly influences the signal transfer between these systems. Little is known about the nanoscopic structure of the cell-sensor interface that is essential for a detailed interpretation of the recordings. Therefore, we analysed the interface between the sensor surface and attached cells using transmission electron microscopy (TEM). The maximum possible resolution of our TEM study, however, was restricted by the quality of the interface preparation. Therefore, we complemented our studies with imaging ellipsometry. We cultured HEK293 cells on substrates, which had been precoated with different types of proteins. We found that contact geometry between attached cell membrane and substrate was dependent on the type of protein coating used. In the presence of polylysine, the average distance of the membrane-substrate interface was in the range of 35-40 nm. However, the cell membrane was highly protruded in the presence of other proteins like fibronectin, laminin or concanavalin-A. The presented method allows the nanoscopic characterization of the cell-sensor interface.

Surface-textured PEG-based hydrogels with adjustable elasticity: Synthesis and characterization

Poly(ethylene glycol)-dimethacrylate (PEGDMA)-based hydrogels with adjustable shear modulus within the range of 10kPa to 1MPa and precisely predefinable surface textures on a micro-scale were made. It was observed that the volume of all hydrogels after preparation almost exactly matched the volume of the precursor solution and that there were only slight volume changes upon equilibration in excess solvent. This characteristic swelling behavior enables the preparation of textures on the hydrogel's surface with precisely predefinable dimensions. The behavior can be modeled with the Flory-Huggins theory assuming a concentration-dependent polymer-solvent interaction parameter. Additionally, activation of the hydrogels by electrophilic oxirane groups creates reactive sites that will enable the later grafting of the hydrogel's surface with various specific nucleophiles, e.g. biomolecules. Thus, these hydrogels are particularly suitable as biomaterials for systematic investigations of cellular response to surface topography and elasticity of the substrate, both in vivo and in vitro.

Alkaline-treated poly(ε-caprolactone) films: Degradation in the presence or absence of fibroblasts

In the first stage, we observed the study of the degradation behavior of alkaline-treated poly(epsilon-caprolactone) (PCL) in two biologically-related media: phosphate buffered saline (PBS) and Dulbecco's modified Eagle's medium (DMEM) for 18 months, finding a much accelerated degradation in the last one. As expected, the degradation in the presence of cells is much pronounced even considering that the study is limited to 6 months. The characterization of the degraded substrates by chemiluminescence (CL) allows to explain the modifications of the substrate and their relations with transitory oxidative stress phenomena described in the fibroblasts seeded onto the PCL membranes.

Microgrooved fibrillar collagen membranes as scaffolds for cell support and alignment

For several years, microgrooved substrates have been evaluated as a means to orient cells in engineered tissues. Recently, we fabricated thin (0.1-5.3 microm) planar and tubular collagen membranes (CMs) from air-dried hydrogels of native, fibrillar type I collagen (Vernon et al., Biomaterials 2004;26:1109-17). The CMs were strong, stable, and permeable and, hence, of potential use as scaffolds for tissue engineering. In the present study, planar CMs supported a robust attachment, spreading, and proliferation of human dermal fibroblasts (HDFs) and human umbilical artery smooth muscle cells (HUASMCs). Collagen hydrogels were air-dried onto microgrooved templates and subsequently removed in the form of grooved CMs with the potential to align cells. The grooved CMs were highly effective at inducing HDFs and HUASMCs to elongate and align, as revealed by scanning electron microscopy and by assays of f-actin and nuclear orientation. Alignment of cells was maintained at high cell densities. CMs with grooves of substantially different widths and depths were similarly effective in causing cell alignment; however, cells aligned poorly on CMs that had grooves less than 1 microm in depth. Grooved CMs with the capability to align cells might be of considerable use in the fabrication of tissue substitutes.

Vascular Endothelial and Smooth Muscle Cell Culture on NaOH-Treated Poly(ɛ-caprolactone) Films: A Preliminary Study for Vascular Graft Development

Tissue engineering offers the potential of providing vessels that can be used to replace diseased and damaged native blood vessels. The endothelization of a synthetic vascular graft minimizes the failures associated with blood clotting and platelet activation. The aim of this study was to culture vascular-derived endothelial and smooth muscle cells on both untreated and NaOH-treated poly(epsilon-caprolactone) (PCL) films, a biocompatible and bio-resorbable polymer, and to evaluate the behavior of both cell types as a preliminary study for vascular graft development. PCL films were prepared by hot pressing; characterized by DSC, IR, SEM, and scanning force microscopy; and treated with NaOH to increase the surface hydrophilicity before cell culture. Endothelial and smooth muscle cells, isolated from pig cava vein, were characterized by immunofluorescence and confocal microscopy studies of endothelial nitric oxide synthase and alpha-smooth muscle actin. Good adhesion, growth, viability and morphology of both the endothelial and smooth muscle cells on PCL films were obtained, but a light stimulation of mitochondrial activity was observed during short culture times. NaOH treatment improved the adhesion and enhanced the proliferation in both cell types. This verified the possible use of this modified polymer as a support in the preparation of a synthetic vascular graft. [Diagram: see text] SEM micrograph of smooth muscle cells cultured on NaOH-treated PCL film. (Original magnification: 1000x).

Nanotopographical guidance of C6 glioma cell alignment and oriented growth

The surface properties of the extracellular matrix play vital roles in cellular behavior such as adhesion, spreading, migration, proliferation and differentiation. While cell attachment and adhesion onto surfaces are mainly mediated by surface molecular interaction, cell morphology and orientation are significantly affected by the topographical cues of the substrate. We reported here the alignment of C6 glioma cells on polystyrene (PS) substrate containing periodic nanotopography. The ridge/groove type structures (210 nm in periodicity, and 30-40 nm in depth) were generated on polystyrene surface using Nd:YAG polarized laser radiation at 266 nm. The cultured cells were shown to align strictly along the direction of the ridges/grooves. And there were distinctive features such as elongated morphology and asymmetrical cell surface extensions, revealed by confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results indicated that ordered and continuous nanostructures on substrates can pattern cell, and guide cell alignment and oriented growth along definite directions. The possible mechanism and significance of these observations were also discussed.

In vitro study of human vascular endothelial cell function on materials with various surface roughness

In recent years, creating a biodegradable polymer scaffold with an endothelialized surface has become an attractive concept for replacement of small-diameter blood vessels. Toward this end, a better understanding of the interaction between endothelial cells and biodegradable polymer substrates is particularly important. Surface roughness of biomaterials is one of the important parameters that affect cell behavior. In this study, human vascular endothelial cells were cultured on electrospun and solvent-cast poly(L-lactic acid) substrates with different surface roughness. Cell responses were evaluated via both qualitative examinations of cell morphology changes as well as quantitative assessment of cell adhesion and proliferation rate on the different substrates. The results proved that endothelial cell function was enhanced on the smooth solvent-cast surface rather than on the rough electrospun surface of poly(L-lactic acid). Together with our previous findings that electrospun substrates favor vascular smooth muscle cell behavior, it is possible to design a unique three-dimensional scaffold for application of tissue-engineered small-diameter vessel replacement by combining the fabrication technique of solvent casting and electrospinning.

Microtextured substrata alter gene expression, protein localization and the shape of cardiac myocytes

Many of the experiments designed to understand fundamental principles in cardiac physiology are performed in vitro using myocytes isolated from adult or neonatal hearts. However, these cells have probably lost some of their original properties in culture prior to study. Our objective is to recapitulate cardiac myocyte structure and function by growing cells on microtextured silicone substrata produced by photolithography and microfabrication techniques. Myocytes are plated on nontextured, micropegged (5 microm high), microgrooved (parallel grooves with a depth of 5 microm) or combination (micropegged and grooved) substrata. Myocytes plated on microtextured surfaces display a change in cell shape with an increase in myofibrillar height and a decrease in cell area. This shape change did not affect the stoichiometry of the myofibrillar proteins but did elicit microenvironmental remodeling of proteins that mechanically attach the cell to its surroundings. Cells terminate in a sarcomeric striation on the vertical interface of the peg whereas on nontextured surfaces they end in long nonstriated cables. Vinculin, a focal adhesion protein, was found to decrease in expression on combination surfaces as compared to nontextured substrata. A three-dimensional microtextured substratum appears to reintroduce a more physiological microarchitecture for tissue culture that may have potential uses in biological research as well as in tissue engineering and diagnostic applications.

Spreading of epithelial cells on machined and sandblasted titanium surfaces: an in vitro study

BACKGROUND

The purpose of this investigation was to determine the influence of the surface structure of dental implants on epithelial cell spreading and growth in vitro. Cell morphology on machined and sandblasted titanium surfaces was investigated.

METHODS

A total of 10 machined and 10 sandblasted discs and 10 glass coverslips were used for the present study. Samples were analyzed using scanning electron microscopy (SEM) and the cell spreading area was determined using a video image analysis system.

RESULTS

After 24 hours incubation, keratinocytes grown on sandblasted titanium samples displayed numerous, long, and branched or dendritic filopodia closely adapted to the surface roughness. Filopodia varied from 3 to 12 microm in length and 0.1 to 0.3 microm in width. Cells cultured on a machined surface did not present such cytoplasmic extensions and displayed a round morphology. Keratinocytes seeded on glass coverslips were flat and edged by filopodia (maximum length 7 to 8 microm) on the spreading site of the cluster. Though cell morphology is comparable with that observed on sandblasted specimens, cytoplasmic extensions suggestive of strong adhesion and spreading attitude were less pronounced.

CONCLUSION

These results indicate that sandblasted surfaces are the optimal substrata for epithelial cell adhesion and spreading.

Interactions between MC3T3-E1 cells and textured Ti6Al4V surfaces

This paper presents the results of an experimental study of the interactions between MC3T3-E1 (mouse calvarian) cells and textured Ti6Al4V surfaces, including surfaces produced by laser microgrooving; blasting with alumina particles; and polishing. The multiscale interactions between MC3T3-E1 cells and these textured surfaces are studied using a combination of optical scanning transmission electron microscopy and atomic force microscopy. The potential cytotoxic effects of microchemistry on cell-surface interactions also are considered in studies of cell spreading and orientation over 9-day periods. These studies show that cells on microgrooved Ti6Al4V geometries that are 8 or 12 microm deep undergo contact guidance and limited cell spreading. Similar contact guidance is observed on the surfaces of diamond-polished surfaces on which nanoscale grooves are formed due to the scratching that occurs during polishing. In contrast, random cell orientations are observed on alumina-blasted Ti6Al4V surfaces. The possible effects of surface topography are discussed for scar-tissue formation and improved cell-surface integration.

Effect of grooved titanium substratum on human osteoblastic cell growth

Various surface treatments have been developed to increase the clinical performance of titanium-based implants. Many in vitro tests have been carried out on substrates with varied surface topography for a complete understanding of osteoblasts. In previous research, we made the observation that surface roughness must be taken into account, not only in terms of amplitude but also in terms of organization. In this study, we tested the adhesion and proliferation of human primary osteoblasts on grooved titanium surfaces with various amplitudes and organizations of topography. The roughness was described at a scale above (macro-roughness) or below (micro-roughness) the cell size. We observed better orientation and proliferation of human osteoblasts on surfaces with a micro-roughness characterized by a lower Order (parameter describing the organization of topography) and by a higher Ra and Rz (parameters describing the amplitude of topography). It appears that cultured human osteoblasts prefer surfaces with relatively high micro-roughness amplitude and with a low level of repeatability.

Microscale three-dimensional polymeric platforms for in vitro cell culture systems

This paper describes fabrication schemes to create multidimensional polymeric platforms to study cell function. A key feature of these constructs is the replication of in vivo geometry and dimensional size scales that will aid in the understanding of fundamental cell-environment interactions. Advantages of these microtextured membranes include the high degree of reproducibility, optical clarity, and the ability to create multiple features on the micron and sub-micron size scale. We have demonstrated the creation of controlled microscale features on hydrogels as well as biodegradable materials such as poly(lactic-glycolic acid). These microtopographies selectively degrade under physiological conditions. Because of the flexibility of substrate material and the ease of creating micron size structures, this technique can be applied to a multitude of physiological and biological systems.

The effect of titanium surface roughness on the adhesion of monocytes and their secretion of TNF-alpha and PGE2

Dental implant surfaces are important in determining the tissue/surface interaction. One of the first cells to adhere to the implant surface is the monocyte. This study examines the effect of surface roughness on monocyte adhesion and cytokine secretion. Monocyte adherence to titanium discs of 4 different degrees of surface roughness and plastic surfaces was assayed. Blood mononuclear cells were incubated for 1.5 h in 16 mm culture wells into which titanium discs had been placed. Non-adherent cells were washed off and the numbers of remaining adherent monocyte determined by DNA quantification. TNF-alpha and PGE2 secretion in media from overnight cultures of attached monocytes stimulated with lipopolysaccharide (LPS) was quantified using ELISA and RIA, respectively. Monocyte adherence to rough titanium surfaces was greater than to turned titanium surfaces, while the lowest adherence was to the plastic surface. No significant differences in adherence to 250, 75 or 25 microm blasted surfaces could be detected. The number of adherent monocytes increased with time, with maximum adhesion after 2 h of incubation. Incubation of monocytes adherent to titanium surfaces resulted in a decrease of less than 30% in their numbers over 7 days, whereas cells attached to plastic surfaces decreased to non-detectable numbers after 48 h. Porphyromonas gingivalis LPS stimulation upregulated TNF-alpha and PGE2 secretion into the media. The LPS-induced TNF-alpha and PGE2 secretion was independent of the titanium surface roughness, however the lowest amounts of TNF-alpha and PGE2 were secreted from cells attached to plastic surfaces. The results of this study indicate that the number of monocytes attached to blasted titanium surfaces is significantly greater than to machined titanium surfaces. PGE2 and TNF-alpha secretion is less influenced by titanium surface roughness.

Micron-scale positioning of features influences the rate of polymorphonuclear leukocyte migration

Microfabrication technology was used to create regular arrays of micron-size holes (2 microm x 2 microm x 210 nm) on fused quartz and photosensitive polyimide surfaces. The patterned surfaces, which possessed a basic structural element of a three-dimensional (3-D) network (i.e., spatially separated mechanical edges), were used as a model system for studying the effect of substrate microgeometry on neutrophil migration. The edge-to-edge spacing between features was systematically varied from 6 microm to 14 microm with an increment of 2 microm. In addition, collagen was used to coat the patterned quartz surfaces in an attempt to change the adhesive properties of the surfaces. A radial flow detachment assay revealed that cell adhesion was the strongest on the quartz surface (approximately 50% cell attached), whereas it was relatively weaker on polyimide and collagen-coated quartz (approximately 25% cell attached). Cell adhesion to each substrate was not affected either by the presence of holes or by the spacing between holes. A direct visualization assay showed that neutrophil migration on each patterned surface could be characterized as a persistent random walk; the dependence of the random motility coefficient (mu) as a function of spacing was biphasic with the optimal spacing at approximately 10 microm on each substrate. The presence of evenly distributed holes at the optimal spacing of 10 microm enhanced mu by a factor of 2 on polyimide, a factor of 2.5 on collagen-coated quartz, and a factor of 10 on uncoated quartz. The biphasic dependence on the mechanical edges of neutrophil migration on 2-D patterned substrate was strikingly similar to that previously observed during neutrophil migration within 3-D networks, suggesting that microfabricated materials provide relevant models of 3-D structures with precisely defined physical characteristics. In addition, our results demonstrate that the microgeometry of a substrate, when considered separately from adhesion, can play a significant role in cell migration.

Substrate microtopography can enhance cell adhesive and migratory responsiveness to matrix ligand density

The regulation of cell motility by ligand density on substrates with variable microtopography is not well understood. In this report, we studied the adhesion and motility behavior of HepG2 cells on microtextured poly(glycolic-co-lactic)acid (PGLA) copolymer substrates, whose surface bioactivity was differentially modified through the adsorption of 0-5.5 ng/cm(2) collagen. Microtextured PGLA substrates were fabricated as thin films with a uniform surface distribution of micropores of median size of 3.1 +/- 1.5 microm and three-dimensional root mean squared roughness of 0.253 microm. Even in the absence of collagen, cells on microtextured substrates responded to substrate topography by exhibiting a 200% increase in adhesion strength compared with untextured controls and ventral localization of the intracellular adhesion protein vinculin. Further enhancement in adhesion strength (420% over untextured, untreated substrates) was demonstrated with bioactivated, microtextured surfaces, indicating that cell adhesion responses to topography and surface ligand density were cooperative. Our motility studies of cells on untextured substrates adsorbed with different levels of collagen demonstrated that a classical biphasic relationship between the cell population averaged migration rate, mu, and the collagen ligand density was preserved. However, comparison of cell motility responses between untextured and microtextured substrates indicates that the motility versus ligand density curve shifted, such that equivalent levels of cell motility were achieved at lower ligand density on microtextured surfaces. Furthermore, the maximum mu values achieved on the microtextured substrates exceeded those on untextured substrates by twofold. Taken together, we show that the magnitude of subcellular scale microtexture of a polymer substrate can sensitize the cell motility responsiveness to substrate ligand concentration; we suggest that the underlying mechanisms involve alteration in the degree of cell-substrate adhesivity as well as changes in the nature of ligand-induced cell activation processes.

Controlling human polymorphonuclear leukocytes motility using microfabrication technology

We describe a new approach for controlling cell motility on a material surface. Transparent, photosensitive polyimide materials were used to fabricate physical structures on glass; cell motility was then followed over time using optical microscopy. Arrays of pillars and holes with 2 micron square, 4-microm height (or depth) separated by 10 microm were successfully patterned using photolithography. Neutrophils attached and spread on the smooth glass surface and surfaces with pillars. In contrast, cells were rounded and did not adhere to either smooth polyimide film or films with holes. The migration of neutrophils was much faster on holes than on polyimide surface, but it was significantly slower on pillars than on glass. These results suggest that physical patterning may be an effective tool to manipulate cell migration in the design of biomaterials for tissue engineering.

Attachment of astroglial cells to microfabricated pillar arrays of different geometries

We studied the attachment of astroglial cells on smooth silicon and arrays of silicon pillars and wells with various widths and separations. Standard semiconductor industry photolithographic techniques were used to fabricate pillar arrays and wells in single-crystal silicon. The resulting pillars varied in width from 0. 5 to 2.0 micrometer, had interpillar gaps of 1.0-5.0 micrometer, and were 1.0 micrometer in height. Arrays also contained 1.0-micromter-deep wells that were 0.5 micrometer in diameter and separated by 0.5-2.0 micrometer. Fluorescence, reflectance, and confocal light microscopies as well as scanning electron microscopy were used to quantify cell attachment, describe cell morphologies, and study the distribution of cytoskeletal proteins actin and vinculin on surfaces with pillars, wells, and smooth silicon. Seventy percent of LRM55 astroglial cells displayed a preference for pillars over smooth silicon, whereas only 40% preferred the wells to the smooth surfaces. Analysis of variance statistics performed on the data sets yielded values of p > approximately.5 for the comparison between pillar data sets and < approximately.0003 in the comparison between pillar and well data sets. Actin and vinculin distributions were highly polarized in cells found on pillar arrays. Scanning electron microscopy clearly demonstrated that cells made contact with the tops of the pillars and did not reach down into the spaces between pillars even when the interpillar gap was 5.0 microm. These experiments support the use of surface topography to direct the attachment, growth, and morphology of cells. These surfaces can be used to study fundamental cell properties such as cell attachment, proliferation, and gene expression. Such topography might also be used to modify implantable medical devices such as neural implants and lead to future developments in tissue engineering.

Fabrication of microtextured membranes for cardiac myocyte attachment and orientation

To understand the role of tissue adaptation to altered physiological states, a more physiologically and dimensionally relevant in vitro model of cardiac myocyte organization has been developed. A microtextured polymeric membrane with micron range dimensions promotes myocyte adhesion through substrate/cell interlocking and, thus, provides a more suitable stretchable matrix for studying overlying cell populations. These microtextured membranes are created using photolithography and microfabrication techniques. Biologically, mechanically, and optically compatible interfaces with specified microarchitecture and surface chemistry have been designed, microfabricated, and characterized for this purpose. Cardiac myocytes plated on these membranes display greater attachment and cell height compared to conventional culture substrates. Advantages of the microtextured membranes include the high degree of reproducibility and the ability to create features on the micron and submicron size scale. Because of the flexibility of substrate material and the ease of creating micron size structures, this technique can be applied to many other physiological and biological systems.

Osteoblast adhesion on biomaterials

The development of tissue engineering in the field of orthopaedic surgery is now booming. Two fields of research in particular are emerging: the association of osteo-inductive factors with implantable materials; and the association of osteogenic stem cells with these materials (hybrid materials). In both cases, an understanding of the phenomena of cell adhesion and, in particular, understanding of the proteins involved in osteoblast adhesion on contact with the materials is of crucial importance. The proteins involved in osteoblast adhesion are described in this review (extracellular matrix proteins, cytoskeletal proteins, integrins, cadherins, etc.). During osteoblast/material interactions, their expression is modified according to the surface characteristics of materials. Their involvement in osteoblastic response to mechanical stimulation highlights the significance of taking them into consideration during development of future biomaterials. Finally, an understanding of the proteins involved in osteoblast adhesion opens up new possibilities for the grafting of these proteins (or synthesized peptide) onto vector materials, to increase their in vivo bioactivity or to promote cell integration within the vector material during the development of hybrid materials.

Qualitative and quantitative study of human osteoblast adhesion on materials with various surface roughnesses

We quantitatively evaluated the adhesion of human osteoblasts on orthopedic metallic substrates (Ti6Al4V alloy) with various surface roughnesses at several times after inoculation and studied its correlation with qualitative changes in the expression of adhesion proteins and with parameters extensively describing the surface topographies. Cells were orientated in a parallel order on polished surfaces. This orientation was not affected by residual grooves after polishing. On sandblasted surfaces the cells never attained confluence and had a stellate shape, and the cell layer had no particular organization. Extracellular matrix (fibronectin, type I collagen, osteopontin) and cytoskeletal protein (actin, vinculin) orientation reflected the cell layer organization. In our experiment human osteoblasts expressed alpha3beta1 integrin but not alpha2beta1 integrin. In addition to currently analyzed roughness magnitude parameters, we calculated roughness organization parameters (fractal dimension parameters) of the substrates. We observed lower adhesion and proliferation on less organized surfaces (i.e., sandblasted ones). The significant statistical correlation observed between fractal dimension parameters (describing surface roughness organization) and cell parameters adds a new concept to the studies of substratum roughness influence on cell behavior. An attempt at modelization of the cell-surface interaction was made that includes the influence of fractal dimensions parameters.

Contact guidance of rat fibroblasts on various implant materials

Providing a substrate surface with micrometer-sized parallel grooves influences the behavior of cells growing on such substrates in vitro. Cells elongate in the direction of the groove and migrate guided by the grooves. It has been suggested that cellular alignment on microgrooves is predominantly dependent on groove dimensions and that surface chemical variation of the substrate material has little effect. Therefore we seeded primary rat dermal fibroblasts (RDF) on smooth and microgrooved (groove width 1-10 microm, depth 0.5 microm) polystyrene (PS), poly-L-lactic acid (PLA), silicone (SIL), and titanium (Ti) substrates. The production process was found to be more accurate for PS and PLA than for SIL and Ti substrates. A proliferation study, scanning electron microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed differences between RDF behavior on the materials. Our conclusions are (1) the accuracy of microtexture production by casting depends greatly on the material used; (2) even if no sharp discontinuities are present, microtextures still are potent tools for inducing contact guidance; and (3) besides surface texture, surface chemistry has a definitive influence on cell morphology.

Contact guidance of rat fibroblasts on various implant materials

Providing a substrate surface with micrometer-sized parallel grooves influences the behavior of cells growing on such substrates in vitro. Cells elongate in the direction of the groove and migrate guided by the grooves. It has been suggested that cellular alignment on microgrooves is predominantly dependent on groove dimensions and that surface chemical variation of the substrate material has little effect. Therefore we seeded primary rat dermal fibroblasts (RDF) on smooth and microgrooved (groove width 1-10 microm, depth 0.5 microm) polystyrene (PS), poly-L-lactic acid (PLA), silicone (SIL), and titanium (Ti) substrates. The production process was found to be more accurate for PS and PLA than for SIL and Ti substrates. A proliferation study, scanning electron microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed differences between RDF behavior on the materials. Our conclusions are (1) the accuracy of microtexture production by casting depends greatly on the material used; (2) even if no sharp discontinuities are present, microtextures still are potent tools for inducing contact guidance; and (3) besides surface texture, surface chemistry has a definitive influence on cell morphology.

Atomic Force Microscopic Study of Commercially Available Implant Abutments

BACKGROUND

Clinical studies have reported a correlation between the surface roughness of implant abutments and the rate of supragingival and subgingival plaque formation. In order to maintain periimplant health, it is important to understand the relationship between abutment surface characteristics and plaque formation.

PURPOSE

The aim of this study was to use high image resolution imaging techniques for analysis of implant abutment surface topography.

MATERIALS AND METHODS

Five commercially available implant abutments (Brånemark, Nobel Biocide, AB, Goteborg, Sweden, Astra, Astra Tech AB, Mondal, Sweden, IMZ, Friatec AG, Mannheim, Germany, Steri-Oss, Denar Corp, Anaheim, Calif, USA, and POI, Kyocera Corp, Kyoto, Japan) were visually and quantitatively characterized using an atomic force microscope.

RESULTS

Statistical analysis by analysis of variance and Fishers's Protected Least Significant Differences showed significant differences (p < .05) between arithmetic mean deviation values of surface relative to the center plane (Sa). Power spectral density analysis also was effective as a spacing parameter. Sectional profiles measured the exact length, depth, or height of the specific features on the images.

CONCLUSIONS

Within the limits of this study, the Brånemark, Astra and IMZ abutments displayed turning marks in x direction from the procedure. The Steri-Oss abutment showed smoothest surface among the five abutments tested.

Surface topography, corrosion and microhardness of nitrogen-diffusion-hardened titanium alloy

Mechanical-electrochemical interactions accelerate corrosion in mixed-metal modular hip prostheses. These interactions can be reduced by improving the modular component machining tolerances or by improving the resistance of the components to scratch or fretting damage. Wrought cobalt-alloy (CoCrMo) is known to have better tribological properties compared to the titanium alloy (Ti64). Thus, improving the tribological properties of this mixed-metal interface should center around improving the tribological properties of the Ti64 alloy. This study used scanning probe microscopy (contact, tapping and phase contrast mode), scanning electron microscopy, corrosion testing, and microhardness testing to determine the effect of a nitrogen-diffusion hardening process on the surface morphology, electrochemistry and surface hardness of the Ti64 alloy. The nitrogen-diffusion-hardened titanium alloy samples (N-Ti64) had a more pronounced grain structure, more nodular surface, and significantly (P<0.01) higher mean roughness values than the control-Ti64 samples. The N-Ti64 samples also exhibited at least equivalent corrosion behavior and a definite increase in surface hardness compared to the control Ti64 samples. The equivalent corrosion behavior and improved surface hardness indicate the potential for N-Ti64 samples to resist similar and mixed-metal scratch and fretting damage. The use of N-Ti64 as opposed to control-Ti64 may therefore reduce the occurrence of mechanical-electrochemical degradation in mixed-metal modular total hip prostheses.

Focal adhesions and assessment of cytotoxicity

Focal adhesions are highly ordered assemblies of transmembrane receptors, extracellular matrix proteins, and a large number of cytoplasmic proteins, including structural proteins, as well as tyrosine kinases, phosphatases, and their substrates. They are now accepted as a prime component of signal transduction. Because focal adhesions also play an important role in cell morphology and migration, it can be argued that their presence is indicative of healthy cells. This has been the reason for several research groups to conclude that biomaterials sustaining focal adhesion assembly are biocompatible. In this study we demonstrate that cells under cytotoxic stress may still be able to retain their focal adhesions. Human umbilical vein endothelial cells at passage 2 were exposed to nickel and zinc ion solutions ranging from 1 to 0.01 mM for 4 and 24 h. Cells were seeded on fibronectin precoated glass slides or in tissue culture quality 96-well plates. MTT conversion with 1 and 0.5 mM nickel and zinc was strongly depressed, indicating that these concentrations are cytotoxic. Proliferative activity was also affected by these concentrations. Cells exposed to zinc typically retracted and detached from the surface, whereas cells exposed to nickel remained on the surface without signs of retraction. Nevertheless, cells exposed to nickel were impaired to reach confluency, which was determined by cadherin-5 expression. All these data indicate that nickel ions at a sufficient concentration influence cells in a cytotoxic way. Despite this apparent cytotoxicity, focal adhesion distribution as visualized by immunofluorescence staining of vinculin was not affected. With zinc the morphological changes were accompanied by apparent fusion of focal adhesions during retraction and finally dissolution. These data indicate that the mere presence of focal adhesions does not allow a reliable statement about the functional status of a cell. On the other hand, when focal adhesions are affected it is an excellent monitor of disturbed cell function.

The effect of surface roughness of microporous membranes on the kinetics of oxygen consumption and ammonia elimination by adherent hepatocytes

In membrane hybrid liver support devices (HLSDs) using isolated hepatocytes where oxygen is transported only by diffusion to the cells, about 15-40% of the cell mass is likely to be in direct contact with the semipermeable membranes used as immunoselective barriers: quantitative effects of membrane surface properties on the kinetics of hepatocyte metabolic reactions may also affect HLSD performance. In this paper, we report our investigation of the effects of surface morphology of two microporous commercial membranes on the kinetics of oxygen consumption and ammonia elimination by primary hepatocytes in adhesion culture. Isolated rat hepatocytes were cultured on polypropylene microporous membranes with different surface roughness and pore size in a continuous-flow bioreactor whose fluid dynamics was optimized for the kinetic characterization of liver cell metabolic reactions. Collagen-coated membranes were used as the reference substratum. Hepatocyte adhesion was not significantly affected by membrane surface morphology. The rates of the investigated reactions increased with ammonia concentration according to saturation kinetics: the values of kinetic parameters Vmax and K(M) increased as cells were cultured on the membrane with the greatest membrane surface roughness and pore size. For the reaction of oxygen consumption, Vmax increased from 0.066 to 0.1 pmol h(-1) per cell as surface roughness increased from 70 to 370 nm. For the kinetics of ammonia elimination. K(M) increased from 0.23 to 0.32 mM and Vmax increased from 1.49 to 1.79 pmol h(-1) per cell with membrane surface roughness increasing from 70 to 370 nm. Cells cultured on collagen-coated membranes consistently yielded the highest reaction rates. The Vmax values of 0.18 and 2.84 pmol h(-1) per cell for oxygen consumption and ammonia elimination, respectively, suggest that cell functions are also affected by the chemical nature of the substratum.