Wettability Gradient Surface Research Articles

The responses to surface wettability gradients induced by chitosan nanofilms on microtextured titanium mediated by specific integrin receptors

Microtexture and chemistry of implant surfaces are important variables for modulating cellular responses. Surface chemistry and wettability are connected directly. While each of these surface properties can influence cell response, it is difficult to decouple their specific contributions. To address this problem, the aims of this study were to develop a surface wettability gradient with a specific chemistry without altering micron scale roughness and to investigate the role of surface wettability on osteoblast response. Microtextured sandblasted/acid-etched (SLA, Sa = 3.1 μm) titanium disks were treated with oxygen plasma to increase reactive oxygen density on the surface. At 0, 2, 6, 10, and 24 h after removing them from the plasma, the surfaces were coated with chitosan for 30 min, rinsed and dried. Modified SLA surfaces are denoted as SLA/h in air prior to coating. Surface characterization demonstrated that this process yielded differing wettability (SLA0 < SLA2 < SLA10 < SLA24) without modifying the micron scale features of the surface. Cell number was reduced in a wettability-dependent manner, except for the most water-wettable surface, SLA24. There was no difference in alkaline phosphatase activity with differing wettability. Increased wettability yielded increased osteocalcin and osteoprotegerin production, except on the SLA24 surfaces. mRNA for integrins α1, α2, α5, β1, and β3 was sensitive to surface wettability. However, surface wettability did not affect mRNA levels for integrin α3. Silencing β1 increased cell number with reduced osteocalcin and osteoprotegerin in a wettability-dependent manner. Surface wettability as a primary regulator enhanced osteoblast differentiation, but integrin expression and silencing β1 results indicate that surface wettability regulates osteoblast through differential integrin expression profiles than microtexture does. The results may indicate that both microtexture and wettability with a specific chemistry have important regulatory effects on osseointegration. Each property had different effects, which were mediated by different integrin receptors.

Preparation and characterization of gradient wettability surface depending on controlling Cu(OH)2 nanoribbon arrays growth on copper substrate

Gradient wettability surface was prepared on copper substrate via a facile alkali assistant surface oxidation technique. It was based on the control of cupric hydroxide (Cu(OH)2) nanoribbon arrays growth from the upper part to lower part along the vertically placed copper substrate in an aqueous solution of NaOH and (NH4)2S2O8. Thus the gradient wettability functionalized Cu(OH)2 nanoribbon arrays were directly fabricated on copper substrate by varying the immersing time of different positions along the substrate surface. By using a relative dilute NaOH solution (0.75mol/L) and (NH4)2S2O8 solution (0.03mol/L), and regulating dropping speed, the surface gradient wettability changing from the original contact angle of copper substrate (90.5°) to surperhydrophilicity (3.0°) was prepared. The surface fabricated on copper substrate may keep its gradient wetting property after immersed in water bath at 100°C for 10h. The water contact angle measurement (CA), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the wettability, morphologies, crystal structure, and surface chemical compositions of the Cu(OH)2 nanoribbon arrays on copper substrate. This research is expected to be significant in providing a new strategy for the preparation of novel gradient wettability material with potential industrial applications on copper substrate.

Chemical Imaging of Protein Adsorption and Crystallization on a Wettability Gradient Surface

The use of self-assembled monolayers is an established method to study the effect of surface properties on proteins and other biological materials. The generation of a monolayer with a gradient of chemical properties allows for the study of multiple surface properties simultaneously in a high throughput manner. Typically, in order to detect the presence of proteins or biological material on a surface, the use of additional dyes or tags is required. Here we present a novel method of studying the effect of gradient surface properties on protein adsorption and crystallization in situ through the use of ATR-FTIR spectroscopic imaging, which removes the need for additional labeling. We describe the successful application of this technique to the measurement of the growth of a gradient monolayer of octyltrichlorosilane across the surface of a silicon ATR element. ATR-FTIR imaging was also used to study the adsorption of lysozyme, as a model protein, onto the modified surface. The sensitivity of measurements obtained with a focal plane array (FPA) detector were improved though the use of pixel averaging which allowed small absorption bands to be detected with minimal effect on the spatial resolution along the gradient. Study of the effect of surface hydrophobicity on both adsorption of lysozyme to the element and lysozyme crystallization revealed that more lysozyme adsorbed to the hydrophobic side of the ATR element and more lysozyme crystals formed in the same region. These findings strongly suggest a correlation exists between surface protein adsorption and protein crystallization. This method could be applied to the study of other proteins and whole cells.

Effect of gradient wetting surface on liquid flow in rectangular microchannels driven by capillary force and gravity: An analytical study

A model is presented for predicting liquid flow velocity in a rectangular microchannel driven by capillary force, gravity and an extra driving force due to the surface wettability gradient. The nth power function, cos θ x = cos θ 0 + ( cos θ L − cos θ 0 ) ( x L ) n , for the cosine of contact angle (CA) with typical n order of 0.5, 1 and 2 is applied to analyze how the inner surface wettability gradient of the microchannel affects the flow velocity. Flow simulations revealed that the velocity of liquid flow decreases with the length of microchannel and the wettability gradient (e.g. from 80° to 2°) on channel surface will accelerate the motion of liquid when the flow-front approaches to the end of the microchannel although the gradient surface may decrease the initial motion of liquid due to the great CA at channel entrance in comparison to the uniform CA channel (with respect to the lowest CA of 2°). The linear function (n = 1) of wetting gradient profile may achieve relatively more stable and higher flow velocity than the other n power functions. The analysis of driving force along the moving path matches well with the flow velocity predicted by the model.

Dynamics of nanodroplets on wettability gradient surfaces

A lubrication model is used to study the dynamics of nanoscale droplets on wettabilitygradient surfaces. The effects of the gradient size, size of the nanodroplets and the slip onthe dynamics have been studied. Our results indicate that the position of the center ofmass of the droplets can be well described in terms of a third-order polynomialfunction of the time of the motion for all the cases considered. By increasing thesize of the droplets the dynamics increases. It is also shown that the slip canconsiderably enhance the dynamics. The results have been compared with theresults obtained using theoretical models and molecular dynamics simulations.

Water-Collecting Capability of Radial-Wettability Gradient Surfaces Generated by Controlled Surface Reactions

In this work, we developed a controlled oxidation reaction of vinyl-terminated self-assembled monolayers (SAMs) to carboxylic acid-terminated ones to generate radially inward wettability gradient surfaces. The hydrophobicity was introduced on a silicon wafer by SAMs of 10-undecenyltrichlorosilane, and after the initial drop in oxidation, followed by the dilution-by-dropping method, radial-wettability gradient surfaces having hydrophilic centers and hydrophobic exteriors were generated. This direct drop reaction on the SAMs did not require an elastomeric stamp to be fabricated, which allowed for facile tuning of the gradients in terms of sizes and shapes. The fabricated wettability gradient surfaces possessed a water-collecting capability toward the hydrophilic center, which was inactive on previous linear wettability gradient surfaces.

Impact of water drops onto the junction of a hydrophobic texture and a hydrophilic smooth surface

Wettability gradient surfaces play a significant role in control and manipulation of liquid drops. The present work deals with the analysis of water drops impacting onto the junction line between hydrophobic texture and hydrophilic smooth portions of a dual-textured substrate made using stainless steel material. The hydrophobic textured portion of the substrate comprised of unidirectional parallel groove-like and pillar-like structures of uniform dimensions. A high-speed video camera recorded the spreading and receding dynamics of impacting drops. The drop impact dynamics during the early inertia driven impact regime remains unaffected by the dual-texture feature of the substrate. A larger retraction speed of drop liquid observed on the hydrophobic portion of the substrate during the impact of low velocity drops makes the drop liquid on the higher wettability portion to advance further (secondary drop spreading). The net horizontal drop velocity towards the hydrophilic portion of the dual-textured substrate decreases with increasing drop impact velocity. The available experimental results suggest that the movement of bulk drop liquid away from the impact point during drop impact on the dual-textured substrate is larger for the impact of low inertia drops.

Droplet Transportation on a Wettability Gradient Surface Generated by Electrowetting-on-Dielectric

This paper presents a novel microdevice for droplet transportation using a wettability gradient surface that is generated by EWOD (Electrowetting-on-dielectric). Velocity of a droplet on this device can be controlled by changing the frequency of a square-wave voltage that is applied between two interdigitated and wedge-shaped electrodes. When a square wave voltage of 50 V and 10 Hz was applied, the transportation velocity of a 5 μl deionized (DI) water droplet was 3.9 mm/s. Also, we succeeded in transporting not only DI water but also organic solution (dimethyl sulphoxide, DMSO) and electrolyte solution (KCl and phosphate bufferd saline, PBS), and investigated the relationship between their transportation velocities and voltage frequencies.

Effect of channel surface wettability and temperature gradients on the boiling flow pattern in a single microchannel

The objective of this paper is to investigate the effects of channel surface wettability and temperature gradients on the boiling flow pattern in a single microchannel. The test section consists of a bottom silicon substrate bonded with a top glass cover. Three consecutive parts of an inlet fluid plenum, a central microchannel and an outlet fluid plenum were etched in the silicon substrate. The central microchannel had a width of 800 µm and a depth of 30 µm. Acetone liquid was used as the working fluid. High outlet vapor qualities were dealt with here. The flow pattern consists of a fluid triangle (shrinkage of the liquid films) and a connected long liquid rivulet, which is generated in the central microchannel in the timescale of milliseconds. The peculiar flow pattern is formed due to the following reasons: (1) the liquid rivulet tends to have a large contact area with the top hydrophilic channel surface of the glass cover, but a smaller contact area with the bottom silicon hydrophobic surface. (2) The temperature gradient in the chip width direction at the top channel surface of the glass cover not only causes the shrinkage of the liquid films in the central microchannel upstream, but also attracts the liquid rivulet populated near the microchannel centerline. (3) The zigzag pattern is formed due to the competition between the evaporation momentum forces at the vapor–liquid interfaces and the force due to the Marangoni effect. The former causes the rivulet to deviate from the channel centerline and the latter draws the rivulet toward the channel centerline. (4) The temperature gradient along the flow direction in the central microchannel downstream causes the breakup of the rivulet to form isolated droplets there. (5) Liquid stripes inside the upstream fluid triangle were caused by the small capillary number of the liquid film, at which the large surface tension force relative to the viscous force tends to populate the liquid film locally on the top glass cover surface.

Control of water droplet motion by alteration of roughness gradient on silicon wafer by laser surface treatment

Surface wettability gradient from super-hydrophobicity to hydrophobicity was produced by creating surface roughness gradient on polished silicon wafer with excimer laser. Water droplets move spontaneously towards a designed route on this gradient surface. In addition, an irreversible moving behavior with good resistance to external disturbances was observed, which makes the surface suitable for liquid directional transfers. It was also found that the wettability gradient does not always agree with the roughness gradient, which depends on the wetting mode of the droplets. A wetting mode transition from Cassie-Baxter to Wenzel was demonstrated necessary for generating self-motion of water drops. Control of water droplet motion can be achieved by employing these roughness gradient surfaces.

Microfluidic Dispensing Device Using Wettability Gradient and Electrowetting

We have designed a novel microfluidic dispensing device using automatic droplet transportation on a wettability gradient surface that is sequentially followed by electrowetting-based liquid handling. While a droplet moves along the wettability gradient in a main channel, a portion of the droplet is drawn into a side channel and stored in a reservoir temporarily. Next, the stored liquid is dispensed into a mixing channel when a voltage is applied between two electrodes. The fabricated device succeeded in dispensing two liquids of different nanoscale volumes after extracting them from a microscale volume droplet.

Proliferation rate of fibroblast cells on polyethylene surfaces with wettability gradient

AbstractSurface wettability on anchorage‐dependent cells has an important role in cell growth rate. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using corona discharge treatment from a knife‐type electrode whose power increased gradually along the sample length. The PE surfaces were oxidized gradually with increasing power and characterized by Fourier transform infrared spectroscopy, contact angle goniometry, and electron spectroscopy for chemical analysis. The purpose of this study is to determine the rate of proliferation on polymer surfaces with different wettability. The behavior of cell growth for NIH/3T3 fibroblast cells attached on the polymer surfaces with different hydrophilicity was investigated using wettability gradient PE surfaces prepared by corona discharge treatment. They were investigated for the number of grown cells from 24 to 60 h in terms of surface wettability. From the slope of cell number on PE gradient surface versus culture time, the proliferation rates (number of cell/cm2 · h) were calculated. It was observed that the proliferation rate was increased more on positions with moderate hydrophilicity of the wettability gradient surface than on the more hydrophobic or hydrophilic positions, i.e., 1111 (number of cell/cm2 · h) of 57° of water contact angle at the 2.5‐cm position (P &lt; 0.05). This result seems closely related to the serum protein adsorption on the surface: the serum proteins were also adsorbed more on the moderately hydrophilic surface. In conclusion, surface wettability plays an important role in cell adhesion, spreading, and proliferation on the polymer surfaces. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 599–606, 2004

The effect of surface wettability on induction and growth of neurites from the PC-12 cell on a polymer surface

Surface properties of polymeric devices that are used to regenerate nervous damage are a point to be considered for axon regeneration in nerve system. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using a corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces were oxidized gradually with increasing power. The effect of surface wettability on the different types of cells has an important role for cell adhesion and proliferation. The purpose of this study is to investigate neurite formation on polymer surfaces with different wettability. Induction and growth of neurites from the rat pheochromocytoma (PC-12) cells attached on the polymer surfaces with different hydrophilicity were investigated using the wettability gradient PE surfaces prepared by a corona discharge treatment. Neurites were investigated for number and length of neurites in terms of surface wettability. It was observed that neurite formation of PC-12 cells was increased more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. From those results, it could be assumed that initial adhesion of PC-12 cells was caused by more calf serum (CS) protein than nerve growth factor (NGF), whereas the neurite formation of PC-12 cells was caused by more NGF than CS protein. It follows from what has been said thus far that PC-12 cells are a differentiated neuronal phenotype with a long neurite at around the position 2.5 cm (water contact angle of about 55 deg). In conclusion, surface wettability plays an important role for neurite formation on the polymer surfaces for axon regeneration.

The Effect of Fluid Shear Stress on Endothelial Cell Adhesiveness to Polymer Surfaces with Wettability Gradient

In this study, the adhesive strength of endothelial cells (ECs) attached on polymer surfaces with different hydrophilicity was investigated using wettability gradient polyethylene (PE) surfaces prepared by corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The EC-attached wettability gradient surfaces were mounted on parallel-plate flow chambers in a flow system prepared for cell adhesiveness test. Three different shear stresses (150, 200, and 250 dyne/cm2) were applied to the flow chambers and each shear stress was maintained for 120 min to investigate the effect of shear stress and surface hydrophilicity on the EC adhesion strength. It was observed that the ECs were adhered more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion of the cells appeared at around water contact angles of 55°. The EC adhesion strength was higher on the hydrophilic positions than on the hydrophobic ones. However, the maximum adhesion strength of the cells also appeared at around water contact angles of 55°. More than 90% of the adhered cells remained on that position after applying the shear stress, 250 dyne/cm2 for 2 h, whereas the cells were completely detached on the hydrophobic position (water contact angle, about 86°) within 10 min after applying the same shear stress. It seems that surface hydrophilicity plays a very important role for cell adhesion strength.

The role of type 1 fimbriae in adhesion of Escherichiacoli to hydrophilic and hydrophobic surfaces

Adhesion of two different Escherichia coli strains and their respective isogenic fimbriated and non-fimbriated mutants to hydrophilic, hydrophobic and wettability gradient surfaces was studied with respect to the expression of type 1 fimbriae and cell surface characters. Generally, initial adhesion of fimbriated strains was lower than for non-fimbriated strains. However, after an additional 1 h of incubation, the relative distribution of firmly attached cells on wettability gradient surfaces showed that adhesion of fimbriated strains was high on the hydrophobic part and low on the hydrophilic part of the gradient while non-fimbriated strains showed an opposite relationship. Moreover, on hydrophobic surfaces the strength of adhesion was enhanced by fimbriae as assessed by exposing attached bacteria to 0.04% sodium dodecyl sulphate (SDS). Purified fimbriae also adsorbed more and stronger to hydrophobic surfaces than to hydrophilic surfaces. Our results suggest that fimbriae do not facilitate the initial contact of bacterial cells to a surface, but contribute to increased subsequent interaction of bacteria with hydrophobic surfaces due to a higher cell surface hydrophobicity, a lower electrokinetic potential, and possibly by increased interactions through conformational changes of type 1 fimbriae on the surface. On hydrophilic surfaces, however, type 1 fimbriae may have an adverse effect and hinder cells from firm adhesion.

Interaction of Different Types of Cells on Polymer Surfaces with Wettability Gradient

Gradient surfaces whose properties are changed gradually along the sample length are of particular interest for basic studies of the interaction between biological species and surfaces since the effect of a selected property can be examined in a single experiment on one surface. We prepared a wettability gradient on low density polyethylene (PE) sheets by treating them in air with the corona from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power, and the wettability gradient was created on the surfaces as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the interaction of different types of cells (Chinese hamster ovary, fibroblast, and endothelial cells) as well as serum proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The cells adhered and grown on the gradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion and growth of the cells appeared at around water contact angles of 55°, regardless of the cell types used. This result seems closely related to the serum protein adsorption on the surfaces; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability gradient surface.

Platelet adhesion onto wettability gradient surfaces in the absence and presence of plasma proteins

A wettability gradient was prepared on lowdensity polyethylene (PE) sheets by treating them in air with a corona from a knife-type electrode the power of which increased gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power and a wettability gradient was created on the surfaces, as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the adhesion behavior of platelets in the absence and presence of plasma proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The platelets adhered to the wettability gradient surfaces along the sample length were counted and examined by scanning electron microscopy (SEM). It was observed that the platelet adhesion in the absence of plasma proteins increased gradually as the surface wettability increased along the sample length. The platelets adhered to the hydrophilic positions of the gradient surface also were more activated (possessed more pseudo pods as examined by SEM) than on the more hydrophobic ones. However, platelet adhesion in the presence of plasma proteins decreased gradually with the increasing surface wettability; the platelets adhered to the surface also were more activated on the hydrophobic positions of the gradient surface. This result is closely related to plasma protein adsorption on the surface. Plasma protein adsorption on the wettability gradient surface increased with the increasing surface wettability. More plasma protein adsorption on the hydrophilic positions of the gradient surface caused less platelet adhesion, probably due to platelet adhesion inhibiting proteins, such as high-molecular-weight kininogen, which preferably adsorbs onto the surface by the so-called Vroman effect. It seems that both the presence of plasma proteins and surface wettability play important roles for platelet adhesion and activation.

Platelet adhesion onto wettability gradient surfaces in the absence and presence of plasma proteins

A wettability gradient was prepared on low-density polyethylene (PE) sheets by treating them in air with a corona from a knife-type electrode the power of which increased gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power and a wettability gradient was created on the surfaces, as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the adhesion behavior of platelets in the absence and presence of plasma proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The platelets adhered to the wettability gradient surfaces along the sample length were counted and examined by scanning electron microscopy (SEM). It was observed that the platelet adhesion in the absence of plasma proteins increased gradually as the surface wettability increased along the sample length. The platelets adhered to the hydrophilic positions of the gradient surface also were more activated (possessed more pseudo pods as examined by SEM) than on the more hydrophobic ones. However, platelet adhesion in the presence of plasma proteins decreased gradually with the increasing surface wettability; the platelets adhered to the surface also were more activated on the hydrophobic positions of the gradient surface. This result is closely related to plasma protein adsorption on the surface. Plasma protein adsorption on the wettability gradient surface increased with the increasing surface wettability. More plasma protein adsorption on the hydrophilic positions of the gradient surface caused less platelet adhesion, probably due to platelet adhesion inhibiting proteins, such as high-molecular-weight kininogen, which preferably adsorbs onto the surface by the so-called Vroman effect. It seems that both the presence of plasma proteins and surface wettability play important roles for platelet adhesion and activation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 304–311, 1998.

Polar adhesion of Treponema denticola on wettability gradient surfaces

The effects of surface wettability and protein conditioning on adhesion orientation and viability of Treponema denticola were studied using wettability gradient surfaces containing hydrophobic –Si(CH 3) 2 bound to silicon or glass. Adhesion and viability were also compared using hydrophobic and hydrophilic plastics used in bacteriology and tissue culture, respectively. Adhesion to gradients on opaque silicon surfaces was quantified by fluorescence microscopy, and the percentage of bacteria adherent in polar orientation to gradients on transparent surfaces was determined by darkfield microscopy. The experiments were repeated with fibronectin (Fn), fibrinogen and bovine serum albumin conditioned surfaces. Determination of viability was attempted by using fluorescent staining with a carboxyfluorescein diacetate (CFDA) and propidium iodide (PI) mixture as well as scanning the surfaces for microcolonies when the adherent bacteria were placed under growth-promoting conditions. More bacteria bound to hydrophobic sectors of the gradient than to the hydrophilic sector. Virtually all the treponemes on the hydrophobic sector were oriented flat on the surface. In samples rinsed conventionally with buffer, they were deformed, and relatively few stained with CFDA or survived under growth-promoting conditions. Many of the cells adherent to hydrophilic surfaces were tip-oriented, and they retained typical treponemal morphology. Within limitations of the method, the percentage staining with CFDA and excluding PI was higher than on hydrophobic surfaces. More microcolonies were detected on hydrophilic surfaces under growing conditions. Conditioning the gradient surfaces with proteins nearly equalized the number of adherent bacteria among the sectors. Fn conditioning promoted time-dependent polar orientation and survival of bacteria with typical treponemal morphology and CFDA staining. Many more bacteria survived on hydrophobic surfaces that were continuously immersed in buffer and not exposed to the atmosphere during rinsing. Directly staining adherent bacteria with the fluorescent vitality indicators was too unreliable for determining whether individual tip-oriented T. denticola cells survived preferentially. Polar orientation is a phenotype common in treponemal adhesion to biological and wettable inanimate surfaces preconditioned with specific proteins, but direct evidence that it is a major factor for maintaining viability is elusive.

Cellular Responses on a Wettability Gradient Surface with Continuous Variations in Surface Compositions of Carbonate and Hydroxyl Groups

This article reports adhesion, spreading, migration, and proliferation responses of bovine endothelial cells (ECs) on the surface with a unidirectional wettability gradient. The surface chemical gradient, in which molar fractions of cyclic carbonate and hydroxyl groups were inversely varied, was prepared by continuous immersion of a poly(vinylene carbonate) (PVCa) film into an aqueous solution of sodium hydroxide at a constant speed. Advancing water contact angles of the surface, which ranged from 60° for an untreated PVCa surface to around 20° for a well-treated surface, gradually decreased with the distance from the untreated end of the film. Quantitative analyses of cellular characteristics of adhered cells on the gradient surface, which included the initial adhesion rate and the morphological indices of adhered cells such as spreading area, peripheral length, and circular coefficient, showed that these cells gave the highest values on the untreated PVCa surface and rapidly decreased on the surface regions with shorter periods of hydrolysis, followed by a slower decrease on surface regions with longer periods ofhydrolysis with increasing distance from the untreated end. Little adhesion occurred in a well-hydrolyzed, very hydrophilic surface region. The highest migration rate of adhered cells occurred on the slightly hydrophobic surface region (advancing contact angle, 35°) where adhered cells tended to delaminate as tissue formation proceeded. These results indicate that each cellular potential of ECs is dependent on the wettability of the gradient surface, producing polymorphorous states of adhered cells. Thus, the wettability gradient surface served as an excellent substrate to simultaneously study cellular response dependence on surface chemical composition and wettability.