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PubMed2006

Ultrahydrophobicity indicates a non-adhesive default state in gecko setae.

Geckos may represent the world's most demanding adhesives application. The adhesive setae on the toes of climbing geckos must adhere strongly yet avoid fouling or attachment at inappropriate times. We tested the hypothesis that gecko setae are non-adhesive in their unloaded default state by comparing the water droplet contact angle (theta) of isolated setal arrays to the smooth surface of eye spectacle scales of tokay geckos (Gekko gecko). At equilibrium, theta was 98.3 +/- 3.4 degrees in spectacle scales of live geckos and 93.3 +/- 3.5 degrees in isolated spectacles. Isolated setal arrays were ultrahydrophobic, with theta of 160.6 +/- 1.3 degrees (means +/- SD). The difference in theta of setal arrays and smooth spectacles indicates a very low contact fraction. Using Cassie's law of surface wettability, we infer that less than 6.6% of the surface of unloaded setae is solid and at least 93.4% is air space. We calculated that the contact fraction must increase from 6.6% in the unloaded state to 46% in the loaded state to account for previously measured values of adhesion. Thus gecko setae may be non-sticky by default because only a very small contact fraction is possible without mechanically deforming the setal array.

Adhesiveness↗
PubMed2003

Radiofrequency-generated glow discharge treatment: potential benefits for polyester ligaments.

This multicenter study has revealed that treating a woven polyethylene terephthalate (polyester) ligament with a radiofrequency (RF)-generated glow discharge (RFGD) produces marked benefits in terms of increased cell attachment and proliferation on the implant surface. In vitro tests of the same material revealed that the number of synovial fibroblasts attached to the treated samples after 14 days was four times that of the untreated material. Many of the cells were spread over the surface of a single filament, and some formed bridges between one filament and the next. The incorporation of [(3)H]-thymidine by synovial stromal cells (a measure of the amount of cell division) growing on the treated material was five times that on the untreated samples. The amount of DNA present on the treated material was also found to be almost an order of magnitude greater than that on untreated samples. This increase in cell attachment and proliferation is almost certainly related to a notable increase in wettability of the polyester surface induced by treatment. Mechanical tests revealed that, for ligaments with a nominal ultimate tensile strength of 2100 N, RF-generated glow treatment reduced the ligament's strength by 12% but increased its stiffness by 15%. After a medium-term fatigue test (10.8 million cycles), however, there appeared to be recovery of the mechanical properties, with the strength and stiffness of untreated and treated samples being essentially the same. After exhaustive fatigue tests (more than 62 million cycles) the residual strength of the treated ligaments was only 9% lower than that of the unfatigued and untreated ligaments.

Biomechanical Phenomena↗
PubMed1993

Accuracy, detail reproduction, and hardness of gypsum casts produced from silicone impressions treated with glow discharge.

Plasma treatment has been reported to improve the wettability of silicone impression materials. This study investigated whether plasma treatment of silicone impressions influenced the linear dimensional accuracy, detail reproducibility, and surface hardness of models produced from a type IV dental die stone. Five silicone impressions materials were used in this study. Linear dimensional accuracy and detail reproduction were tested according to ISO standards. Surface hardness was evaluated with a Vickers hardness test. The results indicated that plasma-treated impressions from Xantopren and Provil silicone impression materials had significantly smaller dimensional change than their respective controls, and the other materials were not influenced. The detail reproduction was superior in casts produced from plasma-treated impressions from President silicone. Surface hardness was not influenced by the treatment. Plasma treatment of silicone impressions has no negative influence on the tested physical properties of die stone models.

Analysis of Variance↗
PubMed1992

Surface properties and castability of elastomeric impression materials after plasma cleaning.

The wettability of impression materials is an important requirement for accurate reproduction of intraoral structures. The aims of this study were to evaluate the effect of plasma cleaning on critical surface tension and die stone castability of five silicone impression materials. Critical surface tension was calculated using a contact angle analysis according to Zisman (1964), before and after plasma cleaning. Die stone casts were produced from impressions of a master die and the area extension of the reproduction was measured planimetrically. The results showed a general increase in the critical surface tension and in the polar force component of the composite free energy for materials treated with plasma cleaning. An improvement in castability of all materials was also noted.

Analysis of Variance↗
PubMed1994

Effects of surface treatment on the free surface energy of dentin.

OBJECTIVES: The purpose of this study was to evaluate the influence of six treatments on the dispersive, acid, and base components of the free surface energy of dentin. METHODS: Occlusal dentin surfaces were polished with 4000 grit abrasive paper, washed and air dried. Characteristics of the surface energy were calculated by measuring contact angles of the four following liquids:alpha-bromonaphtalene, glycerol, ethylene glycol, and water. The dentin was then treated with aqueous solutions containing: (1) oxalic acid and glycine (OX/GLY),(2) oxalic acid, glycine, and HEMA (OX/GLY/HEMA), (3) phosphoric acid (PA), (4) maleic acid (MA),(5) EDTA, or (6) NaCIO. After treatment, washing and air drying, the energy characteristics of the samples were evaluated again. RESULTS: Three kinds of wetting behavior were observed: an increase (OX/GLY/HEMA), a stabilization (PA, NaCIO) or a decrease (OX/GLY, MA, EDTA) of the wettability of the dentin surface. The calculations demonstrated that dentin surfaces are basic. SIGNIFICANCE: This study of the evolution of the surface energy components gave information on adhesion mechanisms involving hydrophilic and hydrophobic interactions. The results may be helpful in the formulation of conditioners and primers.

Acid Etching, Dental↗
PubMed1995

Influence of light irradiation of dentine primers on dentine-resin bond.

OBJECTIVE: The purpose of this study was to examine the influence of light irradiation of dentine primers that contain camphoroquinone (CQ) on the shear bond strength to dentine and their contact angle. METHOD: Three dentine bonding systems which contain CQ, Imperva Bond, OptiBond and XR-Bond; and Light Bond, which does not contain CQ, were employed. Labial surfaces of freshly extracted lower bovine incisors were ground with no. 600 grit SiC paper. Dentine primers were applied to the dentine surfaces in two groups, irradiated and non-irradiated. A shear bond strength test was performed and the direct contact angle was measured. RESULTS: Statistical analysis (Newman-Keuls multiple comparison P < 0.05) of the data indicated that light irradiation of the dentine primer for systems containing CQ resulted in increased bond strength and decreased contact angle. CONCLUSION: This study indicates that for these dentine bonding systems containing CQ in their primers, light irradiation of the dentine primer is effective in improving wettability and increasing the bond strength to dentine.

Analysis of Variance↗
PubMed2006

Chemiluminescence-based detection and comparison of protein amounts adsorbed on differently modified silica surfaces.

The biological consequences of protein adsorption on biomaterial surfaces are considered to be of utmost importance for their biocompatibility. A new method based on amino group-labeling coupled to a chemiluminescence reaction for direct determination of proteins adsorbed on material surfaces was employed. This method was used to explore the effects of surface chemistry and surface roughness on protein adsorption in a silicon oxide model system. Corundum sandblasting was applied to silicon wafers to create roughened surfaces while immobilization of fluorocarbon-, hydrocarbon-, and poly(ethylene glycol)-containing silanes produced surfaces of varying wettability. The adsorption behavior of two complex body fluids, human serum and saliva, and of two purified components, human serum albumin and fibronectin, was strongly influenced by the surface parameters. A general tendency to higher amounts of adsorbed protein was found on roughened surfaces and modification with poly(ethylene glycol) or with fluorocarbon moieties reduced protein adsorption. The values obtained with the new method could be confirmed by a colorimetric determination of protein amounts adsorbed on identically modified silica beads and were in accordance with those previously reported utilizing established methods for protein quantification. The presented method, which was methodically simple to perform and allowed the simultaneous measurement of a large number of samples, may be of future value for high-throughput surveying of the protein adsorption characteristics of biomaterials.

Adsorption↗
PubMedDate not supplied

Studies on bone marrow stromal cells affinity of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).

The objective of this study is to investigate the biocompatibility of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with bone marrow stromal cells in vitro. The adsorption of fibronectin on the material was studied by enzyme-linked immunosorbent assay. After bone marrow stromal cells were seeded and cultured on PHBHHx, their proliferation was investigated by MTT. Differentiation of the cells was assessed by measuring alkaline phosphatase activity and by histochemical assay. The wettability and thermal property of PHBHHx films were also studied by contact angle goniometer, thermogravimetry and differential scanning calorimetry, respectively. The results show that bone marrow stromal cells can attach, proliferate and differentiate into osteoblasts on PHBHHx films. These results suggest that PHBHHx has good affinity with bone marrow stromal cells and may have potential applications in bone tissue engineering.

3-Hydroxybutyric Acid↗
PubMed2004

Decreased fibroblast cell density on chemically degraded poly-lactic-co-glycolic acid, polyurethane, and polycaprolactone.

Select prolonged functions of fibroblasts leading to extensive fibrous tissue encapsulation can be detrimental to numerous implant applications, including materials designed for the bladder, vasculature, and bone. Specifically, overextended functions of fibroblasts at the tissue-implant interface for orthopedic applications lead to callus formation, fibrous encapsulation events, and ultimately soft (not desirable hard-bony) tissue juxtaposition. Such events result in insufficient regeneration of bone and compromise the overall success of the implant. The objective of the present in vitro study was to determine, for the first time, fibroblast densities on NaOH-treated poly-lactic-co-glycolic acid co-polymers (PLGA), HNO(3)-treated polyurethane (PU), and NaOH-treated polycaprolactone (PCL). Previous studies have demonstrated increased bladder, vascular, and bone cell densities on chemically treated compared to unaltered PLGA, PU, and PCL films. Results of this study provided evidence of decreased fibroblast numbers on chemically treated PLGA, PU, and PCL after time periods of up to 5 days. Examination of these substrates revealed that all chemically modified polymers possessed a high degree of nanometer surface roughness compared to their respective unaltered polymers. In contrast, other material properties (such as chemistry and wettability) were different when comparing chemically treated PLGA, PU, and PCL films. Since fibroblasts are anchorage-dependent cells whose adhesion is a critical prerequisite to the prolonged, extensive formation of a fibrous-tissue containing extracellular matrix, the present in vitro results of decreased fibroblast densities on chemically degraded PLGA, PU, and PCL suggest that these materials may be suitable materials for numerous tissue-engineering applications and, thus, deserve further investigation.

Absorbable Implants↗
PubMed2006

Fibrinogen adsorption, platelet adhesion and activation on mixed hydroxyl-/methyl-terminated self-assembled monolayers.

The effect of surface wettability on fibrinogen adsorption, platelet adhesion and platelet activation was investigated using self-assembled monolayers (SAMs) containing different ratios of longer chain methyl- and shorter chain hydroxyl-terminated alkanethiols (C15CH3 vs. C11OH) on gold. Protein adsorption studies were performed using radiolabeled human fibrinogen (HFG). Platelet adhesion and activation studies with and without pre-adsorbed fibrinogen, albumin and plasma were assessed using scanning electron microscopy (SEM) and a glutaraldehyde-induced fluorescence technique (GIFT). Results demonstrated a linear decrease of HFG adsorption with the increase of OH groups on the monolayer (increase of the hydrophilicity). Platelet adhesion and activation also decrease with increase of hydrophilicity of surface. Concerning SAMs pre-immersed in proteins, fibrinogen adsorption was related with high platelet adhesion and activation. The passivant effect of albumin on platelet adhesion and activation was only demonstrated on SAMs contained C11OH. When all the blood proteins are present (plasma) platelet adhesion was almost absent on SAMs with 65% and 100% C11OH. This could be explained by the higher albumin affinity of the SAMs with 65% C11OH and the lower total protein adsorption associated with SAMs with 100% C11OH.

Adsorption↗
PubMed2006

Procoagulant activity of surface-immobilized Hageman factor.

Procoagulant activity of surface-immobilized coagulation factor XIIa (activated Hageman factor) is reported. Activity of FXIIa immobilized onto the surfaces of three silanized-glass procoagulants spanning a wide range of wettability was assayed in normal and FXII-deficient plasmas. Previously published mathematical models were used to characterize the procoagulant activity of protein-immobilized materials and soluble enzymes. Results show that FXIIa activity is unrelated to underlying procoagulant surface chemistry and is similar to soluble FXIIa activity. The uninfluential role of the surface on FXIIa suggests that the solid surface activates FXII in biomaterial-induced blood coagulation but is not otherwise involved in FXIIa activity as described by the classical mechanism.

Adsorption↗
PubMed2005

Adsorption of hydrophobin proteins at hydrophobic and hydrophilic interfaces.

The surface activity of two hydrophobin proteins, HFBII and SC3, at the solid-liquid, liquid-liquid and liquid-vapor interface has been investigated. Hydrophobins are fungal proteins that are known to adsorb and affect the physico-chemical properties of an interface. In this study, the surface activity was determined by measuring the interaction of hydrophobin molecules with various liquids, solid particles and films that are commonly used or produced in industrial processes. We found that a very low concentration of hydrophobin is required to facilitate the wet-in of hydrophobic solid particles, such as Teflon, into aqueous solutions. It is also capable of stabilizing aqueous dispersions of Kevlar nanopulp, reversing the wettability of hydrophobic films and stabilizing polyunsaturated fatty acid (PUFA) oil-in-water emulsions.

Adsorption↗
PubMed2005

Solid-state characterization of spray-dried ice cream mixes.

The main physicochemical properties of spray-dried ice cream mixes (i.e. surface composition, wettability, flowability and microstructure) were analyzed. Emulsions contained 19-44% milk fat on a dry basis and included mixes with no added emulsifier and/or sucrose. The time necessary for complete wetting of the powders correlated with the amount of surface free-fat measured by means of solvent extraction. Non-micellar casein (sodium caseinate) showed to be a better co-encapsulant than micellar casein (skim milk) as demonstrated by surface fat coverage measured by electron spectroscopy for chemical analysis (ESCA). Emulsifiers influenced the fat surface composition of the powders by reducing the amount of surface protein due to their lower interfacial tension. Surface fat caused an initial overestimation of the particle size of the powders due to fat-related caking. Powders showed no flow before and after surface fat extraction which was attributed to fat-related caking and very small particle size (<80 microm), respectively.

Calorimetry, Differential Scanning↗
PubMed2006

Use of the atomic force microscope to determine the effect of substratum surface topography on the ease of bacterial removal.

The ease of removal of differently sized and shaped bacteria from substrata with defined surface topographies and features was investigated. Surfaces with defined surface topography (smooth or with randomly spaced surface features (pits) of 0.5 microm diameter), chemistry (titanium oxide), and wettability (89-93 degrees) were produced. Atomic force microscopy (AFM) was used to determine the ease of bacterial removal from substrata; gram negative Pseudomonas aeruginosa (rods 1 microm width x 3 microm length) and gram positive Staphylococcus aureus (1 microm diameter coccus). The AFM tip was scanned across the retained cells under liquid (contact mode). Over time, using a continuous perpendicular tip force, approximately one third of the cells were removed from the surface following lateral movement of the AFM tip across the surface. When the perpendicular tip force was increased S. aureus were removed more easily from smooth surfaces. In contrast P. aeruginosa cells were removed more easily from the 0.5 microm featured surfaces. The shape of the cell with respect to the shape of the substratum features influences the ease of removal of the cell from the surface: on smooth surfaces the cocci had a smaller cell:surface contact area, whereas the rods had a larger cell:surface contact area. Conversely on featured surfaces the cocci had a larger cell:surface contact area, whereas rods that lay across features had a smaller cell:surface contact area. Using engineered surfaces with defined properties, it has been shown that manipulation of a single parameter (surface roughness) had an effect on the strength of microbial retention.

Bacterial Adhesion↗
PubMed2005

Capillary penetration failure of blood suspensions.

Blood suspension fails to penetrate a capillary with radius R less than 50 microm even if the capillary is perfectly wettable. This invasion threshold is attributed to three red blood cells (RBCs) segregation mechanisms--corner deflection at the entrance, the intermediate deformation-induced radial migration and shear-induced diffusion within a packed slug at the meniscus. The shear-induced radial migration for deformable particles endows the blood cells with a higher velocity than the meniscus to form the concentrated slug behind the meniscus. This tightly packed slug has a higher resistance and arrests the flow. Rigid particles and rigidified blood cells result in wetting behavior similar to that seen for homogeneous liquids, with decreased RBC migration towards the capillary centerline and reduction of packing. Corner deflection with a radial drift velocity accelerates the radial migration for small capillaries. However, deformation-induced radial migration is the key mechanism responsible for penetration failure. This sequence of mechanisms is confirmed through videomicroscopy and scaling theories were applied to capture the dependence of the critical capillary radius as a function of RBC concentrations.

Algorithms↗
PubMed2005

Wetting properties at the surface of iota-carrageenan-based edible films.

Surface properties of edible films composed of a polymeric matrix of carrageenan in association with hydrophobic material were studied by contact angle measurements. The use of this technique not only in a static mode but also in a dynamic way enables investigation of surface hydrophobicity as well as surface wettability. The absorption flux inside the material can be estimated from the wetting kinetic, which can be very useful to quickly compare water barrier efficiency of the tested films. Comparison of carrageenan films with films containing known amounts of additives enables understanding and correlation of changes of the surface properties with the nature of used additives (glycerol used as a plasticizer, glycerol monostearate used as a surfactant, and fat) and their influence on the orientation of polymer chains at the surface during film formation. Very different responses were observed from one surface of the film (film-casting-support interface) to the other (film-air interface), which could be also attributed to the influence of the support on the polymer and to macromolecular orientation during drying after casting.

Absorption↗
PubMed2006

Wetting and electrical properties of the human hair surface: delipidation observed at the nanoscale.

The electrostatic properties and the wetting behaviour of the human hair surface at the nanometric scale have been investigated by using atomic force microscopy (AFM). Surface potential imaging was used to determine the electrostatic properties while non-contact mode AFM was used to investigate the wetting properties of a test liquid, squalane. We have studied natural hair and hair in which different covalently (18-methyleicosanoic acid) and non-covalently bound fatty acids present at the cuticle surface were selectively extracted. This study shows how the removal of these acids causes various profound changes in hair wettability at the cuticle scale.

Electrochemistry↗
PubMed1995

Surface characteristics of polyether and addition silicone impression materials after long-term disinfection.

It has been demonstrated that short-term disinfection can affect the surface properties of impression materials. This study evaluated advancing contact angle, receding contact angle, inhibition and mass loss of a polyether impression materials, and two different viscosities of an addition silicone impression material after long-term immersion disinfection (18 hours). The brand names of the impression materials tested were Impregum F, Extrude Extra, and Extrude Wash, and all were tested by use of the Wilhelmy technique; first, for the nondisinfected state, which served as controls, and then after 1 and 18 hours of disinfection in a full-strength solution of acid glutaraldehyde. Weight changes before and after the disinfection process were also measured to detect weight loss and mass change over time. All materials exhibited some degree of inhibition. Polyether lost 0.4% mass in air, which indicated loss of a volatile component. Polyether and addition silicone were both relatively hydrophobic and could be disinfected with acid glutaraldehyde for up to 18 hours without affecting wettability.

Analysis of Variance↗