Biomedical subjects

J B Rosenholm

Publications and source records attributed to J B Rosenholm.

8 recordsLinked to original sources

PubMed2006

A critical evaluation of the binary and ternary solid-oil-water and solid-water-oil interaction.

When determining the surface energies of solids the most frequently utilised method is to measure contact angles for particular probe liquids. The measured contact angles (usually measured in air) are then combined with published values of surface- and interfacial tensions of the liquids to give the surface energy of the solid. It is, however, very seldom that sufficient attention is paid to the impurities, to the experimental (e.g. saturated vapour) conditions chosen and to the heterogeneities (chemical and structural) of the solid surface. In this study five typical probe liquids: octane, hexadecane, diiodomethane, alpha-bromonaphthalene and water have been used to establish the dispersion component of the surface energy of the solid and the hydrophobic interaction occurring at the interface of four solids: hydrophobic/hydrophilic SiO2 and hydrophobic/hydrophilic TiO2. Two (solid/liquid) and three (solid/liquid/liquid) component systems were investigated. The results are compared with previously published results when Alkenyl Succinic Anhydride (ASA) was brought into contact with SiO2 under water. The preferential surface vapour pressure and liquid spreading of the one liquid over the solids in the absence and presence of a saturated liquid vapour were evaluated as sources of errors.

Journal Article↗

PubMed2006

Alternative models for determining the surface energy components in offset printing.

Different ways of calculating surface energy components for substrates used in offset printing are compared. The results of the very useful van Oss-Chaudhury-Good bi-bidentate model (vOCG) are simplified to mono-bidentate and mono-monodentate models. The unbalance in the acid-base values often obtained by the vOCG model is strongly reduced when applying the simple mono-monodentate model. Moreover, the frequently encountered problem of negative square roots of the acid and base components is removed. An attempt to describe the ink transfer during offset printing by calculating theoretical works of adhesion between ink/plate and ink/paper is also made. The effect of paper roughness on the wetting was studied with atomic force microscopy (AFM).

Journal Article↗

PubMed2002

Surface properties of in vitro bioactive and non-bioactive sol-gel derived materials.

The acid-base properties of several in vitro bioactive (able to form bone mineral-like calcium phosphate on their surfaces) and non-bioactive sol-gel processed oxides are studied. The amount of Lewis acid sites was calculated from the pyridine adsorption using the Langmuir adsorption model. The Henry adsorption model was used in cases where no specific affinity between the adsorbent and the probe molecule was observed. The results were used to calculate the specific amounts of acidic and basic sites on SiO2- and TiO2-based materials. The zeta potential was measured for dip-coated TiO2 films, calcium- and phosphate-doped TiO2 films and for a non-bioactive Al2O3 film. Also, the calcium phosphate formation in simulated body fluid on in vitro bioactive TiO2 film was studied with zeta potential measurements. The results showed dependence on the negative surface charge and the important role of calcium adsorption in the beginning of the calcium phosphate formation. Surface topography of the films was investigated with atomic force microscopy, including a detailed analysis of the peak heights and distribution over cross sections. It was observed that in vitro bioactivity was strongly dependent on the nanoscale dimensions. Consequently, the in vitro calcium phosphate formation seems to be due to both the chemical interactions and the surface structure.

Adsorption↗

PubMed2001

In vitro bioactivity of aerosol-gel deposited TiO(2) thin coatings.

Bioactive, pure, and Ca- or P-doped TiO(2) thin coatings on Ti metal and Si wafers were prepared by the aerosol-gel technique. The coatings were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. Bioactivity was determined in vitro in a simulated body fluid and was shown to be fully comparable to sol gel-derived TiO(2) coatings prepared by dip-coating. However, the formation rate of carbonate containing apatite decreased with increasing dopant concentration, which was related to changes in chemical composition and topology of the coatings.

Aerosols↗

PubMed1999

Calcium phosphate formation on porous sol-gel-derived SiO2 and CaO-P2O5-SiO2 substrates in vitro.

Sol-gel-derived SiO2 and CaO-P2O5-SiO2 have been shown to be bioactive and bone bonding. In this study bioactive sol-gel-derived SiO2 and CaO-P2O5-SiO2 systems were tested for in in vitro bioactivity. The calcined ceramic monoliths were immersed in a simulated body fluid and analyzed to follow the hydroxyapatite formation on the ceramic surface. Apatite-forming ability was investigated in terms of structural changes by changing the composition and the preparation method. The role of Ca and P dopants in the substrate structure is complicated, and careful characterization is needed. The composition and structure together determine the in vitro bioactivity. The pore structure was analyzed using N2-adsorption/desorption isotherms. The results indicate that a great mesopore volume and a wide mesopore size distribution favor hydroxycarbonate apatite nucleation and a great surface area is not needed. The performed preparation process for silica in a basic environment provides a convenient way to prepare a mesoporous material.

Adsorption↗

PubMed1998

Influence of sol and surface properties on in vitro bioactivity of sol-gel-derived TiO2 and TiO2-SiO2 films deposited by dip-coating method.

Different sol-gel-derived titania and titania-silica films were prepared and their properties related to in vitro bioactivity. The films were prepared by depositing the sols on the substrate surface using a dip-coating method. The sols were monitored carefully as a function of time, using rheological techniques and dynamic light scattering. The topography of the films was characterized using atomic force microscopy, and thicknesses and refractive indexes of the films were evaluated by fitting transmittance spectra measured in a wave length region of 370-1100 nm with a spectrophotometer. The in vitro bioactivity tests were performed in simulated body fluid. Surface topography was found to be of great importance with respect to the bioactivity of the studied films.

Biocompatible Materials↗

PubMed1995

The distribution of oleic acid between salbutamol base drug and different propellant blends.

The distribution of oleic acid between Salbutamol base drug and the solvent in metered-dose inhalers (MDI's) has been investigated. The equilibrium surfactant concentration in the drug dispersions has been determined using a colorimetric method. The samples examined contained Salbutamol base drug particles and oleic acid dispersed in different propellant blends of freon 11 and 12. The maximum equilibrium concentration observed depended on the propellant blend used. The propellant blend and the distribution of the surfactant affected the dispersion stability. The effect of the surfactant is illustrated by the adsorption isotherm for oleic acid onto the Salbutamol particles. The results are correlated with zeta-potentials and particle size measurements made on similar systems in order to characterize the properties of surfactant stabilized MDI's.

Administration, Inhalation↗

PubMed1994

Electrophoretic mobility of salbutamol drug powder in mixed propellant solvents.

The influence of lipids on the dispersion properties of micronized Salbutamol base drug in liquid fluorocarbons has been characterized by electrophoretic mobility measurements and by particle size measurements. A modified Malvern ps26 microelectrophoretic cell was employed, allowing pressurized samples to be analyzed. The measurements were carried out at 25 degrees C in 100:0, 50:50, 40:60, and 30:70 blends of trichlorofluoromethane (P11) and dichlorodifluoromethane (P12) as a function of oleic acid concentration. A limited number of measurements were also done with soybean lecithin or synthetic dipalmitoylphosphatidylcholine (DPPC). A solvent series based on the polarizability (alpha) and on the dipole moment (mu) of the solvent molecules is constructed in order to estimate the acid-base character of the propellants. The results indicate that the type and the amount of lipids and also the type of fluorocarbon mixture plays an important role in the formation of surface charge. The dispersion stability with respect to the measured particle size does not always correlate with the measured electrophoretic mobility, and hence, the surface charge cannot alone explain the dispersion stability. Instead, the wettability of the powders seems to be important as well. Positive surface charge is obtained with the oleic acid or with synthetic dipalmitoylphosphatidylcholine, but negative surface charge exists with soybean lecithin.

Administration, Inhalation↗