Biomedical subjects

J Yliruusi

Publications and source records attributed to J Yliruusi.

At least 37 records · Page 2Linked to original sources

PubMed2000

Surface Pressure, Hysteresis, Interfacial Tension, and CMC of Four Sorbitan Monoesters at Water-Air, Water-Hexane, and Hexane-Air Interfaces.

The purpose of this study was to investigate the interfacial properties of sorbitan monoesters (Span 20, 40, 60, and 80). The surface pressure was investigated at the water-air interface using a Langmuir-Blodgett apparatus. Interfacial tensions at n-hexane-air and water-n-hexane interfaces were measured by a du Nouy tensiometer. The effects of different surface-active agents and their concentrations on the interfacial properties of surfactant films were determined. With saturated sorbitan monoesters the lengthening of the hydrocarbon chain increases the collapse pressure and molecular area at the water-air interface. Unsaturated Span 80 had a lower collapse pressure and a larger molecular area than its saturated counterpart Span 60. Under compression-expansion cycles, all sorbitan monoesters showed hysteresis effects. At the n-hexane-air interface there were no differences in the interfacial tension between different sorbitan monoesters. At the water-n-hexane interface, differences in CMCs were small, but the surface excess of Span 80 was markedly smaller and the molecular area larger than the corresponding values of other sorbitan monoesters. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Next generation fluidized bed granulator automation.

A system for fluidized bed granulator automation with in-line multichannel near infrared (NIR) moisture measurement and a unique air flow rate measurement design was assembled, and the information gained was investigated. The multivariate process data collected was analyzed using principal component analysis (PCA). The test materials (theophylline and microcrystalline cellulose) were granulated and the calibration behavior of the multichannel NIR set-up was evaluated against full Fourier Transform (FT) NIR spectra. Accurate and reliable process air flow rate measurement proved critical in controlling the granulation process. The process data describing the state of the process was projected in two dimensions, and the information from various trend charts was outlined simultaneously. The absorbence of test material at correction wavelengths (NIR region) and the nature of material-water interactions affected the detected in-line NIR water signal. This resulted in different calibration models for the test materials. Development of process analytical methods together with new data visualization algorithms creates new tools for in-process control of the fluidized bed granulation.

Calibration↗

PubMed2000

Extrusion-spheronization of pH-sensitive polymeric matrix pellets for possible colonic drug delivery.

The aim of this study was to investigate extrusion-spheronization pelletization for preparing pH-sensitive matrix pellets for colon-specific drug delivery. The effects of three independent variables (amounts of Eudragit S, citric acid and spheronizing time) on pellet size, shape (roundness and aspect ratio), and drug release were studied with central composite design. The pellets contained ibuprofen as a model drug, citric acid as a pH-adjusting agent, Eudragit S as a pH-sensitive binder and microcrystalline cellulose (MCC). The pellets were prepared with Nica extrusion-spheronizing equipment and subsequently enteric-coated using an air-suspension technique. Eudragit S as a pH-sensitive matrix former in pellets increased the pellet size and influenced pellet roundness. In small amounts Eudragit S increased pellet roundness but in larger amounts pellet roundness was reduced. Citric acid promoted the pelletization process resulting in a narrower area distribution. The pH-sensitive matrix pellet failed to delay the drug release. The combination of citric acid and enteric coating, however, delayed the drug release for 15 min in a pH 7.4 phosphate buffer.

Acrylic Resins↗

PubMed2000

Controlled release injectable liposomal gel of ibuprofen for epidural analgesia.

The epidural administration is used commonly in the treatment of pain. Nonsteroidal anti-inflammatory drugs, especially ibuprofen, would have potential in epidural use. Like many epidurally useful drugs it, however, has a short duration of action, which is a limiting factor. To improve epidural pain treatment, a long-acting, single-dose gel injection is being developed. In the present study, the possibility of using liposomal systems to control the release and dural permeation of ibuprofen was investigated in vitro. Liposomal solutions of ibuprofen.Na (20 mg/ml) were prepared by high-pressure homogenization from egg phosphatidylcholine. The liposomal gel consisted of poloxamer 407 and the liposomal solution. No signs in the 1H-NMR spectroscopy of line broadenings or chemical shifts were observed. The liposomal formulations were reproducible and stable. Ibuprofen release in phosphate buffer, pH 7.4, at 37 degrees C from the liposomal solution and the liposomal gel were prolonged significantly compared with their respective solution and gel controls. The liposomal gel controlled ibuprofen release and dural permeation in vitro and showed a permeation pattern favourable for maintaining constant drug levels. The liposomal poloxamer gel represents a new formulation approach to increase the local epidural availability of ibuprofen. It appeared to be a promising injectable controlled-release drug delivery system.

Animals↗

PubMed2000

Determination of optimal combination of surfactants in creams using rheology measurements.

The effect of surfactant on the rheological properties of some cream formulations was studied. Two surfactants from two different series were combined to determine the combination which yielded the most viscoelastic structure for creams. The surfactants were the soybean derivatives soya sterol, polyethylene glycol 10 soya sterol and polyethylene glycol 25 soya sterol and the sorbitol derivatives sorbitan monooleate and sorbitan trioleate. The rheological properties of the creams were studied using oscillation stress sweep, oscillation frequency sweep and viscosity tests. Droplet size distribution and conductivity of the creams were also determined. The combination polyethylene glycol 10 soya sterol and sorbitan trioleate yielded the most viscoelastic structure with linearly viscoelastic behaviour.

Electric Conductivity↗

PubMed2000

In-line moisture measurement during granulation with a four-wavelength near infrared sensor: an evaluation of particle size and binder effects.

Factors affecting in-line near infrared (NIR) moisture measurement with a four-wavelength sensor were evaluated (choice of binder used in granulation liquid and the increase in particle size). An entire NIR spectrum is not necessary for the measurement of water, and often the use of only a few NIR wavelengths around the water band enables reliable and high-speed detection of moisture. Glass ballotini and microcrystalline cellulose (MCC) were used as model test materials. The binders studied were poly[1-(2-oxo-1-pyrrolidinyl)ethylene] (PVP) and gelatin. Full off-line NIR spectra of test materials at different levels of binder solutions were measured. The major spectral features for both the binders were bands around 1700 nm (first overtones CH related stretches) and 2200 nm (combination bands). Gelatin also had an NH band around 1500 nm (first overtones of NH stretches) and combination bands at about 2050 nm. Particle size effects were observed as an increase in spectra baseline. All these factors should be considered when choosing NIR wavelengths used for detection of water with a fixed wavelength set-up. A robust calibration model enables the development of in-process control of wet granulation processes.

Calibration↗

PubMed2000

Effect of compression force on the crystal properties of erythromycin acistrate tablets.

The crystal properties of compressed and powdered erythromycin acistrate tablets were studied by the X-ray powder diffraction (XRPD) method. Detailed analysis of X-ray powder diffraction line profiles was performed. Diffraction peak intensities and full width at half maximum (FWHM) values of the peaks corresponding to three different crystal lattice directions were determined. Crystallite size was calculated by Scherrer's equation using the data of integral breadth of the peaks. The preferred orientation of the crystallites is also discussed. According to the results, the crystallite size increased on the tablet surface after a small compression force (4 kN) in all crystal lattice directions studied. Even small compression forces caused recrystallization. With higher compression forces (8-18 kN) the crystallite size and the FWHM values remained rather constant. After the compression force of 18 kN the peaks in different crystal lattice directions behaved differently. In the lattice directions of diffraction maxima 2 and 3, the effect was the same with the small (4 kN) and the high compression force (22 kN). Further recrystallization occurred with 22 kN. However, in the crystal lattice direction of diffraction maximum 1 at the compression force of 8 kN the crystallite broke and crystallinity decreased. These were not seen in the powdered tablet samples. It could be concluded that the effect of compression force on the crystal properties of erythromycin acistrate tablets was seen on the tablet surface but not in the powdered tablets. Compression force also affected the preferred orientation of crystallites on the tablet surface and especially in the lattice direction of diffraction maximum 3. This was not seen in the powdered tablets.

Chemistry, Pharmaceutical↗

PubMed2000

Waxy corn starch: a potent cofiller in pellets produced by extrusion-spheronization.

The purpose of this study was to assess the usefulness of waxy corn (maize) starch as a cofiller and diluent in pellets produced by aqueous extrusion-spheronization. Waxy corn starch was combined with microcrystalline cellulose (MCC) in the range of 20-50% of the entire composition. Pellets containing ordinary corn starch or lactose with MCC were used as reference. The shape of pellets was characterized using an optical microscopic image analysis system. The surface and cross-sectional structure were investigated by means of scanning electron microscopy (SEM). The replacement of ordinary corn starch by waxy corn starch made it possible to increase the amount of starch from 20 to 40%. The pellets containing 50% waxy corn starch were of poorer quality but superior to those containing 30% corn starch. The surface structure became slightly more irregular with respect to the amount of either starch, and a cavity was formed inside the pellet during the spheronization. The origin of starch did not affect the surface structure of the pellets. Waxy corn starch is a potential cofiller: the amount of MCC can be reduced in pellets produced by extrusion-spheronization by using waxy corn starch as a cofiller. This enables the reduction of the manufacturing cost of pellets with low drug load.

Cellulose↗

PubMed2000

Content-based image retrieval: a new promising technique in powder technology.

The aim of the present study was to introduce a new technique for analyzing powders by examining the content information of images of pharmaceutical powder systems. Texture features of images of microcrystalline cellulose were compared by using a content-based image retrieval system (CBIR), QBIC (Query-by-Image-Content). The rank order and image similarities were compared to particle sizes and appearances of different mixtures. The image order of the similarity values was in close agreement with the appearance and particle size of the mixtures. When the image of pure Avicel PH 101 was used as a query image, the most similar images were always from images of mixtures with a large number of particles with smaller particle mean sizes. When images of pure Avicel PH 200 were used as a query image, the closest matches of image similarity were from images of mixtures with a larger amount of larger particles. The results show that the CBIR system extracts applicable content information on images of powders, but the texture features used were not totally adequate for analysis of the powders used. In general, content-based image retrieval seems to be a promising approach to efficiently use the vast image information that is available from pharmaceutical powders. Nevertheless, to achieve an efficient CBIR tool for powder technology requires development of substantial algorithms for feature extraction.

Cellulose↗

PubMed2000

Mercury porosimetry of mannitol tablets: effect of scanning speed and moisture.

Purpose of the work was to study the effect of the scanning speed of mercury porosimetry and moisture content of the sample on the mercury porosimetry result for mannitol tablets. Tablets were compressed at three different compression pressures from nonhygroscopic mannitol powder and granules. Pore structure of tablets was determined with three different scanning speeds of a high-pressure mercury porosimeter after storage in three different moisture conditions. With low scanning speed, smallest pores of tablets were determined more accurately. Small amounts of moisture, even as low as 1%, before evacuation in nonhygroscopic mannitol tablets decrease the porosity. Decrease in porosity was observed at a pore diameter range of 50-1000 nm, not at the smallest determined pores. Thus, the role of water in pharmaceutical samples appears to be complicated. Reasonably slow scanning is recommended in high-pressure mercury porosimetry. If total pore volume is the only parameter of interest, fast scanning can be used. Pretreatment of the samples by proper drying before mercury porosimetry is important.

Humidity↗

PubMed2000

Use of the near-infrared reflectance method for measurement of moisture content during granulation.

The purpose of this study was to demonstrate the use of a near-infrared (NIR) method for in-process control of a placebo formulation. An NIR setup with a multichannel detector was applied in the measurement of water during fluidized bed granulation. The effects of two critical granulation parameters were studied using the central composite design. The present NIR setup with three wavelengths proved applicable for in-line moisture measurement. The 1990 nm signal was used for measurement of water and the 1745 and 2145 nm signals were used to correct the change in spectra baseline during granulation. Variations in inlet air conditions proved to be critical factors, explaining differences in the granule size distributions. Differences in granule moistening and drying rates resulting from varying inlet air conditions could be measured with the NIR setup. The moisture content of granules at the end of the spraying phase explained part of the differences in granule size distributions. The moisture content of granules at the end of the drying phase affected the tableting behavior of granules. The results suggested that direct measurement of granule moisture content facilitates the in-process control of the granulation.

Drug Compounding↗

PubMed1999

Rheological characterization of microcrystalline cellulose and silicified microcrystalline cellulose wet masses using a mixer torque rheometer.

The rheological properties of silicified microcrystalline cellulose (Prosolv 50) were compared with those of standard grades of microcrystalline cellulose (Emcocel 50 and Avicel PH 101). Cellulose samples were analyzed using nitrogen adsorption together with particle size, flowability, density and swelling volume studies. The rheological behaviour of the wet powder masses was studied as a function of mixing time using a mixer torque rheometer (MTR). Silicified microcrystalline cellulose exhibited improved flow characteristics and increased specific surface area compared to standard microcrystalline cellulose grades. Although the silicification process affected the swelling properties and, furthermore, the mixing kinetics of microcrystalline cellulose, the source of the microcrystalline cellulose had a stronger influence than silicification on the liquid requirement at peak torque.

Cellulose↗

PubMed1999

Characterization of particle deformation during compression measured by confocal laser scanning microscopy.

Direct compression of riboflavin sodium phosphate tablets was studied by confocal laser scanning microscopy (CLSM). The technique is non-invasive and generates three-dimensional (3D) images. Tablets of 1% riboflavin sodium phosphate with two grades of microcrystalline cellulose (MCC) were individually compressed at compression forces of 1.0 and 26.8 kN. The behaviour and deformation of drug particles on the upper and lower surfaces of the tablets were studied under compression forces. Even at the lower compression force, distinct recrystallized areas in the riboflavin sodium phosphate particles were observed in both Avicel PH-101 and Avicel PH-102 tablets. At the higher compression force, the recrystallization of riboflavin sodium phosphate was more extensive on the upper surface of the Avicel PH-102 tablet than the Avicel PH-101 tablet. The plastic deformation properties of both MCC grades reduced the fragmentation of riboflavin sodium phosphate particles. When compressed with MCC, riboflavin sodium phosphate behaved as a plastic material. The riboflavin sodium phosphate particles were more tightly bound on the upper surface of the tablet than on the lower surface, and this could also be clearly distinguished by CLSM. Drug deformation could not be visualized by other techniques. Confocal laser scanning microscopy provides valuable information on the internal mechanisms of direct compression of tablets.

Drug Compounding↗

PubMed1999

Microcrystalline cellulose and its microstructure in pharmaceutical processing.

Mercury porosimetry and nitrogen adsorption methods were used in pore structure and pore surface area characterisation of microcrystalline cellulose powder, granules and tablets. The effect of compression on pore structure and surface area of tablets compressed with three different compression pressures of powder and granules was determined. Densification of MCC in wet granulation led to decreased compactibility in tableting. Effects of granulation on the microstructure of microcrystalline cellulose and plastic deformation of powder during compression were detected with nitrogen adsorption, at the diameter range 3-200 nm. Structure of granules was destroyed during tableting when compression pressures of 196 MPa were used. Fragmentation and deformation of granules were observed from the results determined using both methods. Due to different measurement ranges, different theoretical basis of the methods and behaviour of the samples during analysis, results obtained with mercury porosimetry and nitrogen adsorption methods are not strictly comparable. Results obtained with mercury porosimetry give information on the behaviour of powder and granule particles in granulation or compression, whereas nitrogen adsorption brings out the changes in intraparticular structure of particles. The results obtained using these methods together can be used in the characterisation of behaviour of materials in granulation and tableting.

Adsorption↗

PubMed1999

Effects of process variables on the size, shape, and surface characteristics of microcrystalline cellulose beads prepared in a centrifugal granulator.

Preparation of microcrystalline cellulose (MCC) beads with a laboratory-scale centrifugal granulating apparatus was studied, and the pharmaceutical quality of the beads was characterized with respect to the subsequent drug layering. Five process parameters of potential importance, including rotor rotation speed X1, slit air X2, spray air pressure X3, spray air rate X4, and height of nozzle setting X5, were evaluated using a fractional factorial design (FFD 2(5-2)) as the experimental design. The responses evaluated were expected yield, mean size, size distribution, shape characteristics (including roundness, circularity, elongation, rectangularity, and modelx), and friability. All five process parameters studied were found to have an influence on the selected properties of the beads, but the effects of rotor rotation speed, slit air flow rate, and spray air rate were statistically significant (p < .05). The effect of the rotor rotation speed was found to be the most potent on all the responses studied. The results also show some significant interactions between the parameters tested. The most significant interactions were between rotor rotation speed and slit air, rotor rotation speed and spray air, and slit air and spray air.

Cellulose↗

PubMed1998

Controlled release and dura mater permeability of lidocaine and ibuprofen from injectable poloxamer-based gels.

Epidural administration of drugs is becoming more common in the treatment of severe forms of pain. To improve present therapies, a long-acting single-dose gel injection would be beneficial. The present study investigated the use of three different polymers as additives in injectable poloxamer gel in controlling the drug release. The release of lidocaine.HCl and ibuprofen.NA from 25% poloxamer (PO) gel and poloxamer gel with hydroxypropylmethylcellulose (HPMC), sodium carboxymethylcellulose (CMC), or dextran (DE) was studied in vitro. Cellulose additives significantly prolonged ibuprofen release, whereas additives were found to have a slight release-increasing effect on lidocaine as compared with the PO gel. The structural differences of the gels, more than the macroviscosity, seem to regulate the release of drugs. The drug permeation-prolonging effect of the respective gels, along with the control solutions, was evaluated in vitro using porcine dura mater membrane. The compact gel depot acted as the rate-limiting step, and significantly prolonged the dural permeation of both drugs in comparison with control solutions. The difference in the drug release and permeation-reducing effects of the gels demonstrated the possibility for interactions between dural membrane and the gel. The findings are promising for further experimental in vivo animal testing of these injectable poloxamer-based gels.

Anesthetics, Local↗

PubMed1998

Pore structure and surface area of mannitol powder, granules and tablets determined with mercury porosimetry and nitrogen adsorption.

Two methods used in pore structure characterisation, mercury porosimetry and nitrogen adsorption, were compared. Pore structure and surface area of mannitol powder, granules produced in wet granulation and tablets compressed with three compression pressures were studied. Greater surface area, more porous structure and greater number of small pores in granules, when compared with powder, increased the compactibility of mannitol granules in tableting. Plastic deformation and fragmentation of powder and granules in compression were observed in volume pore size distributions and surface areas measured with these methods. Pore volume and volume pore size distribution obtained with mercury porosimetry describe densification of mass better than those obtained with nitrogen adsorption. In spite of differences between the methods, the volume pore size distribution curves of samples in the overlapping pore size range had the same shape. The specific surface area of tablets, measured by the nitrogen gas adsorption method described well the deformation under compression. Fragmentation increased the surface area of powder, and plastic deformation decreased the surface area of granules in the pore size range determined. Surface area values measured with mercury porosimetry were larger than those determined with nitrogen adsorption.

Chemistry, Pharmaceutical↗

PubMed1998

Dependence between dissolution rate and porosity of compressed erythromycin acistrate tablets.

The correlation between dissolution rate and porosity of compressed erythromycin acistrate tablets was studied. The total porosity of the tablets, the pore size distribution and the specific surface area of the pores were determined using high-pressure mercury porosimetry. The particle size and specific surface area of the raw material and of the dry granulated mass of the tablets were also determined. The results show that the pore size distribution, showing the differences in pore structure, is more informative than total intruded volume of mercury. However, it is very difficult to explain the dissolution behaviour of erythromycin acistrate tablets only by porosity results of the tablets, and more work is still needed in this field.

Erythromycin↗