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PubMed2003

Processing of nimesulide-PEG 400-PG-PVP solid dispersions: preparation, characterization, and in vitro dissolution.

The objective of this investigation was to study the influence of dissolution enhancers such as polyethylene glycol 400, propylene glycol, polyvinylpyrrolidone K30, sodium lauryl sulfate, and Tween 80 on in vitro dissolution of a model active pharmaceutical material--nimesulide. Preliminary studies were conducted using a physical blend of nimesulide, and the adjuvants and solid dispersions were prepared using solvent evaporation and cogrinding methods. Aqueous solution of adjuvants was first triturated with nimesulide, followed by mixing with lactose and microcrystalline cellulose, and finally water was evaporated under vacuum in a cogrinding method. A 33 factorial design was adopted in a cogrinding method using the concentration of polyethylene glycol 400, propylene glycol, and polyvinylpyrrolidone K30 as independent variables. Tween 80 and sodium lauryl sulfate were added in all the batches. Full and reduced models were evolved for different dependent variables. The reduced models were validated using two checkpoints. Angle of repose < 35 degrees, percentage of drug released in 30 min (Q30) > 40%, 45 min (Q45) > 50%, and 120 min (Q12) > 60% were used as constraints for the selection of an optimized batch. Contour plots are presented for the selected dependent variables. Polyvinylpyrrolidone was found to be more effective in increasing the drug dissolution, compared with polyethylene glycol 400 and propylene glycol. The granule flow was adversely affected when high levels of liquid adjuvants were used in formulations. Wettability study was conducted to measure wetting time for pure drug and the optimized batch. Improved drug dissolution was attributed to improved wetting and the solubilizing effect of adjuvants from the pseudosolid dispersions of nimesulide. Significant improvement in drug dissolution was observed (Q120 = 70%), compared with pure drug powder (Q120 = 15%). In conclusion, dissolution of nimesulide can be modulated using an appropriate blend of pharmaceutical adjuvants.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

Thermoresponsive terpolymeric films applicable for osteoblastic cell growth and noninvasive cell sheet harvesting.

A novel multifunctional linear block copolymer, poly(N-isopropylacrylamide-co-acrylic acid)-b-poly( L-lactic acid) (NAL), was synthesized to expand the concept of cell sheet engineering by using its thermoresponsive property and processibility. The chemical structure of synthesized NAL was confirmed by Fourier transform infrared spectroscopy, and its molar mass (103,500 g.mol(-1)) and molar mass distribution were determined by matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. NAL copolymer was fabricated into thin films by spin-casting. Spin-cast NAL films displayed thermoresponsive properties as demonstrated by surface wettability and topology changes from relatively more hydrophobic (contact angle of 56 degrees) and rougher at 37 degrees C to relatively more hydrophilic (contact angle of 40 degrees) and smoother at 22 degrees C, as assessed by contact angle measurement and atomic force microscopy, respectively. Murine osteoblastic MC3T3-E1 cells displayed comparable adhesion but slower proliferation on NAL films than on poly(L-lactic acid) (PLLA) films and tissue culture polystyrene (TCPS). Within 9 days of cell culture, the highest alkaline phosphatase activity of MC3T3-E1 cells occurred later (on day 9) on NAL films than on PLLA films and TCPS (on day 6). A well-established MC3T3-E1 cell sheet was successfully detached from NAL films, in the absence of enzymes, within about 5 min by simply lowering the temperature from 37 degrees C to room temperature. NAL copolymer has potential for use in the controlled release of therapeutic agents while simultaneously supporting cell growth. In addition, it may be applicable for noninvasive two- or three-dimensional cell sheet harvesting.

Alkaline Phosphatase↗
PubMed2000

Effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus in patients undergoing mechanical ventilation.

OBJECTIVE: To evaluate the effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus and transportability by cilia and cough in patients undergoing invasive mechanical ventilation (up to 72 hrs). DESIGN: Prospective, randomized, clinical study. SETTING: General intensive care unit and university research laboratory. PATIENTS: A total of 32 consecutive patients with acute respiratory failure, who were intubated and mechanically ventilated in the intensive care unit setting, were enrolled in the study. INTERVENTIONS: Patients were randomly assigned to receive as a humidifying system a heat and moisture exchanger (HME) or heated humidified water (HHW) at the onset of mechanical ventilation (time 0). Respiratory mucus samples were collected by suction using a sterile technique at time 0, 24, 48, and 72 hrs of mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: Eleven patients were excluded from this study because of either extubation or death before 72 hrs of mechanical ventilation, leaving 12 patients in the HME group and nine patients in the HHW group. Ventilatory variables including minute volume, mean airway pressure, positive end-expiratory pressure, Fio2, as well as Pao2/Fio2 ratio, fluid balance (last 6 hrs), furosemide, and inotrope administration (last 4 hrs) were recorded. In vitro mucus transportability by cilia was evaluated on the mucus-depleted frog palate model, and the results were expressed as the mucus transport rate. Cough clearance (an estimation of the interaction between the flow of air and the mucus lining the bronchial walls) was measured using a simulated cough machine, the results being expressed in millimeters. Mucus wettability was measured by the contact angle between a mucus sample drop and a flat glass surface. Mucus rheologic properties (mechanical impedance [log G*] and the ratio between viscosity and elasticity [tan delta]) were measured using a magnetic microrheometer at 1 and 100 cGy/sec deformation frequency. The two humidification groups were comparable in terms of the Acute Physiology and Chronic Health Evaluation II score, age, gender, ventilatory variables, fluid balance, use of inotropes, and furosemide. CONCLUSION: Ours results indicate that air humidification with either HME or HHW at 32 degrees C (89.6 degrees F) has similar effects on mucus rheologic properties, contact angle, and transportability by cilia in patients undergoing mechanical ventilation, except for transportability by cough, which diminished after 72 hrs of mechanical ventilation in the HME group (p = .0441).

APACHE↗
PubMed1996

Spoilation and clinical performance of monthly vs. three monthly Group II disposable contact lenses.

Twelve subjects were fitted with a high water content, nonionic contact lens (Pilkington Barnes-Hind "Precision UV"), which was either replaced every month for 3 months or worn for 3 consecutive months before replacement occurred. Visual quality, high and low contrast acuity, and comfort were unaltered with either replacement schedule, but overall satisfaction was significantly greater with the shorter replacement schedule (p = 0.04). Front surface wettability revealed a large amount of intersubject variability and was reduced at the 3-month visit with the longer replacement period lenses (p = 0.003). Visible deposits also increased with longer replacement times (p < 0.05). Laboratory-based analytical results showed that both gross lipid and gross extractable protein significantly increased in the 3-month lenses compared with the 1-month lenses, with 44% less lipid accumulation and 60% less protein deposition occurring with the shorter replacement time. The results support the replacement of high water content lenses on a monthly basis.

Adult↗
PubMed2006

Influence of day and night wear on surface properties of silicone hydrogel contact lenses and bacterial adhesion.

PURPOSE: The aim of this study was to determine the effect of continuous wear on physicochemical surface properties of silicone hydrogel (S-H) lenses and their susceptibility to bacterial adhesion. METHODS: In this study, volunteers wore 2 pairs of either "lotrafilcon A" or "balafilcon A" S-H contact lenses. The first pair was worn continuously for a week and the second pair for 4 weeks. One lens of each pair was used for surface characterization and the other one for bacterial adhesion experiments. Lens surfaces were characterized by examination of their wettability, roughness, elemental composition, and proteins attached to their surfaces. Adhesion of Staphylococcus aureus 835 and Pseudomonas aeruginosa #3 to a lens was studied using a parallel plate flow chamber. RESULTS: Before use, the lotrafilcon A lens was rougher than the balafilcon A lens and had a lower water contact angle and a higher affinity for S. aureus 835. After wear, both lens types had similar water contact angles, whereas the differences in elemental surface composition decreased as well. S. aureus 835 adhered in higher numbers to worn balafilcon A lenses, whereas the opposite was seen for P. aeruginosa #3. The initial deposition rates of both bacterial strains to lotrafilcon A lenses decreased by wearing and were found to correlate significant (P < 0.001) with the surface roughness of worn lenses. CONCLUSIONS: In this study, the differences in surface properties between 2 types of S-H lenses were found to change after 1 week of continuous wear. Generally, bacteria adhered in lower numbers and less tenaciously to worn lenses, except S. aureus 835, adhering in higher numbers to worn balafilcon A lenses.

Bacterial Adhesion↗
PubMed2005

Effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell initial attachment.

The clinical success of dental implants is governed in part by surface properties of implants and their interactions with the surrounding tissues. The objective of this study was to investigate the effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell attachment in vitro. Passivated titanium samples used in this study were either non heat treated or heat treated at 750 degrees C for 90 minutes. It was observed that the contact angle on heat-treated titanium surfaces was statistically lower compared with the non-heat-treated titanium surfaces. The non-heat-treated titanium surface was also observed to be amorphous oxide, whereas heat treatment of titanium resulted in the conversion of amorphous oxide to crystalline anatase oxide. No significant difference in albumin and fibronectin adsorption was observed between the heat-treated and non-heat-treated titanium surfaces. In addition, no significant difference in initial cell attachment was observed between the two groups. It was concluded that heat treatment of titanium resulted in significantly more hydrophilic surfaces compared to non-heat-treated titanium surfaces. However, differences in oxide crystallinity and wettability were not observed to affect protein adsorption and initial osteoblast precursor cell attachment.

Adsorption↗
PubMed2005

Three-dimensional mixed-wet random pore-scale network modeling of two- and three-phase flow in porous media. II. Results.

We use the model described in Piri and Blunt [Phys. Rev. E 71, 026301 (2005)] to predict two- and three-phase relative permeabilities of Berea sandstone using a random network to represent the pore space. We predict measured relative permeabilities for two-phase flow in a water-wet system. We then successfully predict the steady-state oil, water, and gas three-phase relative permeabilities measured by Oak (Proceedings of the SPE/DOE Seventh Symposium on Enhanced Oil Recovery, Tulsa, OK, 1990). We also study secondary and tertiary gas injection into media of different wettability and initial oil saturation and interpret the results in terms of pore-scale displacement processes.

Absorption↗
PubMed2004

Hydrodynamics within the electric double layer on slipping surfaces.

We show, using extensive molecular dynamics simulations, that the dynamics of the electric double layer (EDL) is very much dependent on the wettability of the charged surface on which the EDL develops. For a wetting surface, the dynamics, characterized by the so-called zeta potential, is mainly controlled by the electric properties of the surface, and our work provides a clear interpretation for the traditionally introduced immobile Stern layer. In contrast, the immobile layer disappears for nonwetting surfaces, and the zeta potential deduced from electrokinetic effects is considerably amplified by the existence of a slippage at the solid substrate.

Computer Simulation↗
PubMed2005

The wetting of surface-treated silicone impression materials by gypsum mixes containing disinfectants and modifiers.

PURPOSE: This work evaluated wettability of silicone impression surfaces by gypsum mixes containing disinfectants. MATERIALS AND METHODS: Two types of dental stone were modified by mixing with aqueous solutions of either sodium hypochlorite or povidone iodine. These materials were subjected to further modification by adding a mixture of 1% gum arabic and 0.132% calcium hydroxide to reduce the water requirement of the hemihydrate. Mix consistency tests were carried out to determine the effect of the disinfectants and the modifying additives on the mix fluidity. Contact angles of the mixed materials were measured when they were poured against a polyvinylsiloxane impression material that had undergone the following treatments (1) no treatment (control), (2) surfactant treated, (3) disinfectant treated, and (4) treated with both surfactant and disinfectant. One-way analysis of variance (ANOVA) was carried out using Dunnett's method to determine if experimental groups were significantly different from the control. RESULTS: Gypsum mix consistency was reduced by the presence of combined gum arabic and calcium hydroxide additives. Contact angle data showed that the additives and disinfectants incorporated into the gypsum had, in general, no beneficial effect on the wetting of an untreated silicone surface, or a surface treated with surfactant. In some instances, better wetting was obtained with disinfectant-treated surfaces, and surfaces that had been disinfected and treated with surfactant. CONCLUSIONS: Fluidity of the mixed gypsum was affected by the modifying additives. Chemical disinfectants incorporated in gypsum have little effect on the wetting behavior of dental gypsum. Modifying dental stone powders with gum arabic and calcium hydroxide additives (before mixing at the manufacturers' recommended liquid/powder ratios), improved the wetting behavior of the mixed materials in some cases, but results were not consistent.

Analysis of Variance↗
PubMed2004

Influence of the hydrophobic and hydrophilic characteristics of sliding and slider surfaces on friction coefficient: in vivo human skin friction comparison.

INTRODUCTION: The objective of this study was to investigate whether hydrophilic/hydrophobic balance (Hi/Ho) of the skin surface strongly modifies the friction coefficient (mu). The Hi/Ho balance is determined using the relationship between the critical surface tension gammac (Zisman's principle:which delimits the wetting capacity) and the surface tension of water gammaH2O (water: reference element of Hi/Ho balance). METHOD: Critical surface tension gammac was determined (according to Zisman's principle) through the measurement of advancing contact angle theta of a series of ethanol/water dilutions. Friction coefficient depends on several parameters: types of probe motions (rotational vs. linear), surface roughness and physicochemical parameters of surfaces in contact). In this study, the wettability parameters for six surfaces (human skin forearm, Teflon, silicone impression material 'Silflo', vinyl polysiloxane impression material 'resin' steel and glass) were measured and their influences were compared to friction coefficient mu. RESULTS: This study shows that the higher hydrophobia tendency of the surfaces, the lower friction coefficient. The use of three sliding materials (Teflon, steel and glass) of different Hi/Ho balance confirms the importance of these physicochemical parameters in mu. For example, Teflon with high hydrophobia has a low mu. Friction coefficient increased when hydrophobia of sliding and slider surfaces decreased. CONCLUSION: Friction coefficient value depends on the type of slider surface and its physicochemical properties. In vivo,the friction coefficient may quantify the influence of lubrificant/emolients/moisturizers. For example, the friction coefficient of hydrated skin (through the action of moisturizing products) is higher than the friction coefficient of dry skin. The relationship between the friction coefficient and the Hi/Ho balance can be reversed in the presence of water and sebum on forehead, for example.

Adult↗
PubMed2003

A reversibly switching surface.

We report the design of surfaces that exhibit dynamic changes in interfacial properties, such as wettability, in response to an electrical potential. The change in wetting behavior was caused by surface-confined, single-layered molecules undergoing conformational transitions between a hydrophilic and a moderately hydrophobic state. Reversible conformational transitions were confirmed at a molecular level with the use of sum-frequency generation spectroscopy and at a macroscopic level with the use of contact angle measurements. This type of surface design enables amplification of molecular-level conformational transitions to macroscopic changes in surface properties without altering the chemical identity of the surface. Such reversibly switching surfaces may open previously unknown opportunities in interfacial engineering.

Adsorption↗
PubMed2005

Wetting-driven structure ordering of a copolymer/homopolymer/nanoparticle mixture in the presence of a modulated potential.

We investigate pattern formation on a solid substrate of a diblock copolymer-homopolymer mixture containing doping wettable nanoparticles with a preferential attraction for one component of the copolymers, using a three-order-parameter model. The presence of doping nanoparticles under the surface-interaction modulation breaks the isotropy in the process of microphase-separation and macrophase-separation. This leads to the formation of orientational microphase and macrophase structures due to the interplay between the phase separation and wetting particle ordering under a modulated potential at the late stage. Simulations suggest that the microphase morphology and macrophase morphology can be changed through adjustment of the wetting strength, the amplitude as well as the period of the modulated potential. It provides some important insights for changing microphase and macrophase structures in polymer blends by wetting-driven spinodal decomposition.

Complex Mixtures↗
PubMed2006

Viscoelastic dewetting of a polymer film on a liquid substrate.

The Dewetting of thin polymer films (60-300 nm) on a non-wettable liquid substrate has been studied in the vicinity of their glass transition temperature. In our experiment, we observe a global contraction of the film while its thickness remains uniform. We show that, in this case, the strain corresponds to simple extension, and we verify that it is linear with the stress applied by the surface tension. This allows direct measurement of the stress/strain response as a function of time, and thus permits the measurement of an effective compliance of the thin films. It is, however, difficult to obtain a complete viscoelastic characterization, as the short time response is highly dependant on the physical age of the sample. Experimental results underline the effects of residual stress and friction when dewetting is analyzed on rigid substrates.

Computer Simulation↗
PubMed2001

Isocyanate-terminated urethane prepolymer as bioadhesive material: evaluation of bioadhesion and biocompatibility, in vitro and in vivo assays.

Attempts have been made to evaluate the degree of bioadhesion and biocompatibility of a synthesized urethane prepolymer with specially tailored microstructure. Wetting behaviour and extent of interfacial adhesion of the prepared prepolymer towards biological substrates were examined by in vitro methods. The former was carried out by measuring the contact angle between drops of the prepolymer liquid and a biological surface, while the latter was determined from the force between the prepolymer and tissue model or mucus. The obtained results exhibited good tissue wettability and bioadhesion by the prepolymer. Preliminary evaluation of biocompatibility for the uncatalytically cured prepolymer films was performed by cytotoxicity and histotoxicity experiments. Results showed a significant growth for the adhered L929 fibroblast cells within a period of 5 days incubation. Also, no severe inflammatory tissue response towards the samples implanted in rabbit for 16 weeks was seen. These observations can support the potentiality of the designed urethane prepolymer to be applied as hemostatic agent.

Adhesiveness↗
PubMed2003

Contact angle, protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium.

Chitosan, a derivative of the bio-polysaccharide chitin, has shown promise as a bioactive material for implant, tissue engineering and drug-delivery applications. The aim of this study was to evaluate the contact angle, protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium. Rough ground titanium (Ti) coupons were solution cast and bonded to 91.2% de-acetylated chitosan (1 wt% chitosan in 0.2% acetic acid) coatings via silane reactions. Non-coated Ti was used as controls. Samples were sterilized by ethylene oxide gas prior to experiments. Contact angles on all surfaces were measured using water. 5 x 10(4) cells/ml of ATCC CRL 1486 human embryonic palatal mesenchyme (HEPM) cells, an osteoblast precursor cell line, were used for the cell attachment study. SEM evaluations were performed on cells attached to all surfaces. Contact angles and cell attachment on all surfaces were statistically analyzed using ANOVA. The chitosan-coated surfaces (76.4 +/- 5.1 degrees) exhibited a significantly greater contact angle compared to control Ti surfaces (32.2 +/- 6.1 degrees). Similarly, chitosan-coated surfaces exhibited significantly greater (P < 0.001) albumin adsorption, fibronectin adsorption and cell attachment, as compared to the control Ti surfaces. Coating chitosan on Ti surfaces decreased the wettability of the Ti, but increased protein adsorption and cell attachment. Increased protein absorption and cell attachment on the chitosan-coated Ti may be of benefit in enhancing osseointegration of implant devices.

Adsorption↗
PubMed1999

Water and the acute biological response to surfaces.

Molecular self association in water through hydrogen bonding is a powerful organizational force leading to a three-dimensional hydrogen-bonded network (water structure) that profoundly influences solvent properties. Localized perturbations in the chemical potential of water as by, for example, contacting with a solid surface, induces compensating changes in water structure that can be sensed tens of nanometers from the point of origin using the surface force apparatus (SFA) and ancillary techniques. These instruments reveal attractive or repulsive forces between opposing surfaces immersed in water, over-and-above that anticipated by continuum theory (DLVO), that are attributed to a variable density (partial molar volume) of a more-or-less ordered water structure, depending on the water wettability (surface energy) of the water-contacting surfaces. Water structure at surfaces is thus found to be a manifestation of hydrophobicity and, while mechanistic/theoretical interpretation of experimental results remains the subject of some debate in the literature, convergence of experimental observations permit a quantitative definition of the heretofore relative terms 'hydrophobic' and 'hydrophilic'. In particular, long-range attractive forces (< 100 nm) are detected only between surfaces exhibiting a water contact angle theta > 65 deg (defined as hydrophobic surfaces with pure water adhesion tension tau0 = gamma0 cos theta < 30 dyn cm(-1) where gamma0 is water interfacial tension = 72.8 dyn cm(-1)). Short range repulsive forces (< 5 nm) are detected between surfaces exhibiting theta < 65 deg (hydrophilic surfaces, tau0 > 30 dyn cm(-1)). These findings together with other lines of chemical evidence suggest at least two distinct kinds of water structure and reactivity: a relatively less-dense water region against hydrophobic surfaces with an open hydrogen-bonded network and a relatively more-dense water region against hydrophilic surfaces with a collapsed hydrogen-bonded network. Solvent properties of interfacial water profoundly influence the biological response to materials in a surprisingly straightforward manner when key measures of biological activity sensitive to interfacial phenomenon are scaled against water adhesion tension tau0 of contacting surfaces. Protein adsorption, activation of blood coagulation, and bioadhesion are offered as examples in point, illustrating that the hydrophobic/hydrophilic contrast in the biological response to materials, often disputed in biomaterials science, is very clear when viewed from the perspective of water structure and reactivity at surfaces.

Adsorption↗
PubMed2002

Anode glow discharge plasma treatment enhances calcium phosphate adsorption onto titanium plates.

Glow discharge plasma (GDP) supplied to a cathode (GDP-) has been applied for cleaning, surface activating, and sterilizing biomaterials, because the kinetic energy in the case of the GDP- is larger than that supplied to the anode (GDP+). However, no comparison between GDP+ and GDP- has been reported. In this study, a titanium surface pre-treated with GDP+ and GDP- was characterized by x-ray photoelectron spectroscopy (XPS). In addition, the wettability of the titanium surface was measured with and without GDP. Furthermore, XPS characterized the adsorption of inorganic ions on titanium surfaces with and without GDP and immersed in an electrolyte solution. The findings suggested that GDP+ enhances calcium phosphate nucleation, due to the accumulation of electrons. In addition, calcium phosphate was not nucleated on the specimen with GDP-. We conclude that GDP+ is more suitable for biomineralization on titanium.

Adsorption↗
PubMed2006

Polyelectrolyte multilayer film coating and stability at the surfaces of oral prosthesis base polymers: an in vitro and in vivo study.

A new type of coating involving a layer-by-layer technique has been recently reported. This coating is composed of a polyelectrolyte multilayer film that confers specific properties on surfaces to which it is applied. Here, we studied the applicability of such a technique to the coating of oral prostheses, by first testing the construction of polyelectrolyte multilayer films on several polymers used in oral prosthesis bases, and, subsequently, by studying the stability of these coatings in vitro, in human saliva, and in vivo in a rat model. We demonstrated that the multilayered films are able to coat the surfaces of all tested polymers completely, thus increasing their wettability. We also showed that saliva does not degrade the film after 7 days in vitro and after 4 days in vivo. Taken together, our results establish that the layer-by-layer technique is suitable for the coating of oral devices.

Acrylates↗