Biomedical subjects

Jouko Yliruusi

Publications and source records attributed to Jouko Yliruusi.

43 records · Page 3Linked to original sources

PubMed2002

Rheological properties of three component creams containing sorbitan monoesters as surfactants.

Creams from three components, surfactant, purified water and oil, were prepared. Comparable molar fractions of components were used in order to better understand the structural properties of the components used. The surfactants were sorbitan monoesters, sorbitan monolaurate, monopalmitate, monostearate and monooleate, which differed from each other in the length or structure of the hydrocarbon chain. The oils used were isopropylpalmitate and myristate, and they differed from each other in the length of the fatty acid chain. Rheological properties, droplet size distributions and types (either o/w or w/o) of the creams were studied. The rheological tests used were oscillation stress sweep test, creep recovery test and viscosity test. The modelling of the creep phase was based on the creep recovery test. Sorbitan monolaurate and monostearate formed w/o creams, sorbitan monopalmitate and monooleate o/w creams. It appeared that the double-bonded structure of the surfactant made the cream less elastic. Elasticity was increased due to lengthening of the alkyl chain of the surfactant and increased amount of surfactant. Also the lengthening of the fatty acid chain of the oil made the creams more elastic. The results of the rheological tests and droplet size distributions correlated well each other. According to the modelling of the creep phase, creams could be represented either with the Burger model or with the Maxwell model.

Elasticity↗

PubMed2002

Tablet film-coating with amylose-rich maize starch.

The purpose of the present study was to investigate an aqueous-based amylose-rich maize starch (Hylon VII) film-coating process of tablets performed by a side-vented pan coating system. Three formulation or process parameters of potential importance, including the plasticizer concentration (X(1)), the temperature of coating pan (X(2)) and the spray rate of the coating solution (X(3)), were evaluated using a central composite face-centred experimental design. Only a few process-related limitations associated with the aqueous film coating of Hylon VII were observed, and, in general, the coated tablets were of fairly good quality. At low spray rates, the temperature of the coating pan did not affect the roughness of the coated tablets. At higher spray rates, higher temperature gave smoother films. As regards surface quality and smoothness, a plasticizer concentration (i.e., a 1:1 mixture of sorbitol and glycerol) of approximately 65% of the polymer weight, seems to be suitable for the present formulations. The dissolution of all Hylon VII-coated tablets in an acidic medium was rapid, more than 75% of the drug (theophylline) dissolved within 15 min. On the basis of the present results, it can be concluded that amylose-rich maize starch (Hylon VII) may be considered as an aqueous film-coating agent to be used for pharmaceutical purposes and in established film-coating processes.

Amylose↗

PubMed2002

Does a powder surface contain all necessary information for particle size distribution analysis?

The aim of this study was to utilise a new approach where digital image information is used in the characterisation of particle size distributions of a large set of pharmaceutical powders. A novel optical set-up was employed to create images and calculate a stereometric parameter from the digital images of powder surfaces. Analysis was made of 40 granule batches with varying particle sizes and compositions prepared with fluidised bed granulation. The extracted digital image information was then connected to particle size using multivariate modelling. The modelled particle size distributions were compared to particle size determinations with sieve analysis and laser diffraction. The results revealed that the created models corresponded well with the particle size distributions measured with sieve analysis and laser diffraction. This study shows that digital images taken from powder surfaces contain all necessary data that is needed for particle size distribution analysis. To obtain this information from images careful consideration has to be given on the imaging conditions. In conclusion, the results of this study suggest that the new approach is a powerful means of analysis in particle size determination. The method is fast, the sample size needed is very small and the technique enables non-destructive analysis of samples. The method is suitable in the particle size range of approximately 20-1500 microm. However, further investigations with a broad range of powders have to be made to obtain information of the possibilities and limitations of the introduced method in powder characterisation.

Particle Size↗

PubMed2002

Hydrate formation during wet granulation studied by spectroscopic methods and multivariate analysis.

PURPOSE: The aim was to follow hydrate formation of two structurally related drugs, theophylline and caffeine, during wet granulation using fast and nondestructive spectroscopic methods. METHODS: Anhydrous theophylline and caffeine were granulated with purified water. Charge-coupled device (CCD) Raman spectroscopy was compared with near-infrared spectroscopy (NIR) in following hydrate formation of drugs during wet granulation (off-line). To perform an at-line process analysis, the effect of water addition was monitored by NIR spectroscopy and principal components analysis (PCA). The changes in the crystal arrangements were verified by using X-ray powder diffraction (XRPD). RESULTS: Hydrate formation of theophylline and caffeine could be followed by CCD Raman spectroscopy. The NIR and Raman spectroscopic results were consistent with each other. NIR revealed the state of water, and Raman spectroscopy gave information related to the drug molecule itself. The XRPD confirmed the spectroscopic results. PCA with three principal components explained 99.9 of the spectral variation in the second derivative NIR spectra. CONCLUSIONS: Both CCD Raman and NIR spectroscopic methods can be applied to monitoring of hydrate formation processes. However, NIR is more suitable for monitoring solid-water interactions.

Multivariate Analysis↗

PubMed2002

Development of an automation system for a tablet coater.

An instrumentation and automation system for a side-vented pan coater with a novel air-flow rate measurement system for monitoring the film-coating process of tablets was designed and tested. The instrumented coating system was tested and validated by film-coating over 20 pilot-scale batches of tablets with aqueous-based hydroxypropyl methylcellulose (HPMC). Thirteen different process parameters were continuously measured and monitored, and the most significant ones were logged for analysis. Laser profilometry was used to measure the surface roughness of the coated tablets. The instrumentation system provided comprehensive and quantitative information on the process parameters monitored. The measured process parameters and the responses of the film-coated tablet batches showed that the coating process is reproducible. The inlet air-flow rate influenced the coating process and the subsequent quality of the coated tablets. Increasing the inlet flow rate accelerated the drying of the tablet surface. At high inlet flow rate, obvious film-coating defects (ie, unacceptable surface roughness of the coated tablets) were observed and the loss of coating material increased. The instrumented and automated pan-coating system described, including historical data storage capability and a novel air-flow measurement system, is a useful tool for controlling and characterizing the tablet film-coating process. Monitoring of critical process parameters increases the overall coating process efficiency and predictability.

Automation↗

PubMed2001

The Behavior of Sorbitan Surfactants at the Water-Oil Interface: Straight-Chained Hydrocarbons from Pentane to Dodecane as an Oil Phase.

The interfacial tension of four sorbitan surfactants (Span 20, sorbitan monolaurate; Span 40, sorbitan monopalmitate; Span 60, sorbitan monostearate; and Span 80, sorbitan monooleate) was determined at the water-oil interface. Seven straight-chained hydrocarbons from pentane to dodecane were used as an oil phase. From the interfacial tension measurements the following values were calculated: critical micelle concentration (cmc), the interfacial tension at the cmc (gamma(cmc)), surface pressure at the cmc (pi(cmc)), area per molecule at the cmc (A(cmc)), standard free energy of micellization (DeltaG degrees (mic)), and standard free energy of adsorption (DeltaG degrees (ad)). The shorter chained Span 20 and unsaturated Span 80 had higher cmc values and Span 80 had a larger molecular area than the other surfactants. With the same oil phase, differences between pi(cmc) values of the four sorbitan monoesters were small, but the gamma(cmc) was slightly lowered as the hydrophobicity of the surfactant was increased. DeltaG degrees (mic) was less negative for Span 20 and the DeltaG degrees (ad) value was slightly more negative for Span 80. The effect of the oil phase was obvious. Increasing the hydrocarbon chain length of the oil phase increased gamma(cmc) and cmc values while pi(cmc) and A(cmc) were decreased. As the length of the hydrocarbon chain of the oil phase was increased, DeltaG degrees (mic) and DeltaG degrees (ad) became less negative, which means a less spontaneous reaction. Copyright 2001 Academic Press.

Journal Article↗

PubMed2001

The Effect of Temperature on Sorbitan Surfactant Monolayers.

The effect of temperature on four sorbitan ester (Span 20, sorbitan monolaurate; Span 40, sorbitan monopalmitate; Span 60, sorbitan monostearate; and Span 80, sorbitan monooleate) monolayers was analyzed. The covered temperature range was from 22 to 42 degrees C. Surface pressure-molecular area isotherms were measured with a Langmuir-type instrument. As the temperature was increased, the monolayers expanded more. This change can also be seen from the surface compressional modulus that was lowered as the temperature was increased. Also, the collapse pressure was lowered as the temperature was increased. Copyright 2001 Academic Press.

Journal Article↗