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Biomedical subjects

I G Jolliffe

Publications and source records attributed to I G Jolliffe.

10 recordsLinked to original sources
PubMed2005

Alginate rafts and their characterisation.

Alginate/antacid anti-reflux preparations are designed to provide symptom relief by forming a physical barrier on top of the stomach contents in the form of a neutral floating gel or raft. This study tested the in vitro effectiveness of a range of liquid products in forming rafts that were cohesive, buoyant, voluminous, resistant to reflux and durable under conditions of movement (resilient). The products tested had a wide range of acid neutralising capacities (ANCs). It was found that products with a high ANC and no calcium ion source formed rafts of low strength, weight and volume, which appeared more as floating precipitates than coherent gels. Products with a high ANC and a calcium ion source formed medium strength, weight and volume rafts. Products with a low ANC formed strong coherent rafts with medium to large weight and volume, and those with low ANC and a calcium ion source formed the strongest rafts. Products with stronger rafts were found to be more resilient and more resistant to reflux in an in vitro reflux model. Significant overall differences in raft buoyancy were found between products forming coherent rafts but these could not be related to the product formulation or amount of available carbon dioxide.

Alginates↗
PubMed2004

Feasibility of a bioadhesive drug delivery system targeted to oesophageal tissue.

This contribution examines the feasibility of utilising an oesophageal-adhesive alginate layer to support model drug particles. Such a bioadhesive system offers the prospect of local drug delivery to the oesophagus, which in turn has applications in the treatment of conditions including gastro-oesophageal reflux disease and oesophageal cancer. Surface-modified (amine, carboxylate and sulfate) as well as neutral fluorescent beads were investigated as model drug particles. A fluorescence assay technique was utilised to quantify the extent and duration of adhesion of a fixed dose of these particles to excised porcine oesophageal tissue. Retention of the particles was investigated both from aqueous systems and within an adhesive alginate solution. After 30 min significantly higher adhesion of neutral beads was recorded from the alginate solution as compared to the aqueous suspension (n = 6, P < 0.05). The beads that possessed a negative charge showed significantly greater retention within the alginate carrier (n = 6, P < 0.05). However, the amine-modified beads showed retention profiles that were similar both within the alginate carrier and within the aqueous suspension (n = 6, P > 0.05).

Adhesives↗
PubMed2002

An in vitro mucosal model for prediction of the bioadhesion of alginate solutions to the oesophagus.

This paper discusses the development of an in vitro model utilised to assess the adhesion of alginate solutions to porcine oesophageal tissue. The methodology involved the construction of retention apparatus onto which sections of tissue were mounted. Fluorescently labelled alginate solutions of known rheological profile were dispensed onto the tissue at a concentration of 2% w/v. A washing solution was applied at a specified rate to mimic saliva flow and the eluted material collected. Fluorimetric analysis allowed dose retention to be assessed as a function of time. The effect of the nature of the washing solution and the choice of alginate were investigated. It was found that after 30 min up to 20% of the applied alginate dose remained associated with the tissue, regardless of the alginate selected from the range examined. The nature of the washing medium did not have a significant effect on retention, irrespective of the inherent mucin concentration. Overall this study indicated that the technique presented offers a viable means of studying bioadhesion of liquids and also demonstrates that alginate solutions may have an application as bioadhesive agents for localisation within the oesophagus.

Adhesiveness↗
PubMed1983

The effect of dosator nozzle wall texture on capsule filling with the mG2 simulator.

The effect on capsule filling, using an mG2 simulator, of the surface texture of the bore of the dosator nozzle has been investigated for size fractions of lactose. Since the angle of powder-wall friction between the powder and the nozzle cannot be readily measured insitu, this was determined using flat plates with similar surface textures fitted into a Jenike shear cell apparatus. The problems of reproducing surface textures on both types of surface are discussed and a lapping process employed as the most suitable method. Angles of wall friction for the nozzle surfaces were extrapolated from the values obtained from flat plates of similar roughness. Capsule filling experiments, using the mG2 simulator, showed the three resurfaced nozzles produced more uniform fill weights with smaller measured compression and ejection stresses than an untreated nozzle surface. One lapped nozzle surface produced a slightly greater improvement than the others. This supports the concept of an optimum angle of wall friction for powder retention (and hence uniformity of fill) with a minimum of applied compression stress.

Capsules↗
PubMed1983

Capsule filling studies using an mG2 production machine.

A production mG2 G36 machine has been employed to study the effects of compression on the capsule filling properties of four particle size fractions of lactose having a range of flow properties. The effect of the surface texture of the dosator nozzle bore on capsule filling is also investigated. Fine, cohesive powders gave uniform fill weights over a whole range of compression settings but as increasingly free-flowing powders were used, this range diminishes. For both types of powder, the upper limit on compression is set by compaction of powder which produces poor fill weights; coarse, free-flowing powders, which are less compressible, compact at lower compressions. Free-flowing powders, in particular, also require a minimum compression to be retained. Resurfaced nozzles produced improved capsule filling. One nozzle surface produced slightly more uniform fill weights and was unaffected by powder coating of the nozzle suggesting that an optimum surface texture exists for capsule filling. The results are similar to those obtained using the mG2 simulator and hence validate the latter's use in studying production capsule filling.

Capsules↗
PubMed1982

The design and use of an instrumented mG2 capsule filling machine simulator.

The problems of instrumenting a continuous motion dosator nozzle capsule filling machine (mG2 type) are discussed and the construction of an mG2 simulator is described. A standard filling turret is employed with mechanical modification so that the dosator does not rotate. This allows instrumentation in the form of the strain dosator piston, to measure compression and ejection stresses during filling, as well as distance transducers, to measure the corresponding piston and dosator movements. An experimental method is described for using this machine to study the filling of lactose powders.

Capsules↗
PubMed1982

Practical implications of theoretical consideration of capsule filling by the dosator nozzle system.

Eight lactose size fractions with mean particle sizes ranging from 15.6 to 155.2 micrometers were characterized by their failure properties using a Jenike shear cell. The effective angle of internal friction was found to be constant for all size fractions, with a mean value of 36.2 degrees. Jenike flow factors could only be obtained for the two most cohesive size fractions presumably due to limitations of the shear cell. Angles of wall friction, phi, were determined for all size fractions on face ground and turned stainless steel surfaces. These decreased with increasing particle size up to around 40 micrometers, above which they became effectively constant for both surfaces. The rougher turned plate gave consistently higher values of phi for each particle size. Simple retention experiments with a dosator nozzle and a range of powder bed bulk densities showed good retention was possible only up to a particle size of around 40 micrometers. Retention was difficult or impossible above this size. Values of phi were applied to equations derived in the theoretical approach described previously (Jolliffe et al 1980). This showed that the strength required within a powder to ensure arching increases with increasing particle size up to around 40 micrometers. Above this size, this strength requirement becomes constant. This is related to the powder retention observations. Finally, the failure data was used to calculate the minimum compressive stresses required to ensure powder retention within the dosator nozzle, by employing the equations described by Jolliffe et al (1980). This suggested that, as powders became more free flowing, a larger compressive stress is necessary and that the angle of wall friction should be lower to ensure stress is transmitted to the arching zone.

Capsules↗
PubMed1982

An investigation of the relationship between particle size and compression during capsule filling with an instrumented mG2 simulator.

An instrumented mG2 capsule filling machine simulator has been employed to study the effects of the amount of compression (compression ratio) on the capsule fill weight uniformity and measured compression and ejection stresses. Four size fractions of lactose were studied (mean particle sizes 15.6, 17.8, 37.5 and 155.2 micron). The range of compression over which satisfactory filling could be achieved was large for fine, cohesive powders but decreased with increasing particle size. The lower limit of filling ability was the ability to retain the powder and the amount of compression needed to achieve retention increased with increasing particle size. The upper limit on compression, was the compaction of the powder which prevented the piston acting to cause retention. Large particle sizes were able to undergo only a small change in volume before compaction occurred whilst fine, cohesive powders were considerably more compressible and hence could be filled satisfactorily at higher compression settings.

Capsules↗