Influence of the surface tension of wet massing liquid on the functionality of microcrystalline cellulose as pelletization aid

Objective: To study microcrystalline cellulose II (MCCII) as new pelletization aid for a high and low solubility drugs such as verapamil. HCl and carbamazepine, respectively.Methods: Approximately, 30 g of MCCII and drug mixtures were hydrated passed through a # 20 mesh sieved and spheronizated at a frequency of 6 Hz and residence time of 480 s. A microscopy analysis was used to evaluate the shape and size descriptors. Pellets properties such as compressibility, friability, density, flowability and product yield were also evaluated. Drug release properties were tested according to the USP specifications and compared to those of MCCI.Results: The wetting level of the excipients depended on drug loading and drug solubility. Thus, a high drug loading (>50%) rendered pellets having a low yield, flowability and caused a detriment on size descriptors. Likewise, the regular morphology and strength of MCCII-based pellets was highly affected by increasing drug loads. Verapamil. HCl pellets were less friable and compressible and showed better flowability than carbamazepine pellets. Regardless of drug loading and drug solubility, MCCII-based pellets released more than 80% of verapamil. HCl within 10 min, whereas released more than 75% of carbamazepine within 15 min. Conversely, MCCI pellets had a satisfactory verapamil. HCl release, but ~30% carbamazepine release within 1h.Conclusion: MCCII proved to be a better excipient than MCCI to yield beads having optimal pellet characteristics and rendered an immediate release profile for verapamil. HCl and carbamazepine.

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ASSESSMENT OF THE PRODUCTION VARIABLES ON THE PELLETIZATION PROPERTIES OF MICROCRYSTALLINE CELLULOSE II (MCCII)

International Journal of Pharmacy and Pharmaceutical Sciences ◽

10.22159/ijpps.2017v9i10.20580 ◽

2017 ◽

Vol 9 (10) ◽

pp. 73

Author(s):

John Rojas ◽

David Correa

Keyword(s):

Microcrystalline Cellulose ◽

Total Porosity ◽

Operating Conditions ◽

Cellulose Ii ◽

Shape Descriptors ◽

Pellet Size ◽

Surface Design ◽

Operational Conditions ◽

High Moisture Level ◽

Pelletization Aid

Objective: To study microcrystalline cellulose II (MCCII) as new pelletization aid using the extrusion/spheronization technology.Methods: The effect of the spheronization rate and spheronization time was assessed by a response surface design. The shape descriptors and physical properties of pellets were taken as response variables. Approximately, 30 g of MCCII were hydrated, passed through a # 20 mesh sieve and spheronizated at frequencies of 6, 9 and 12 Hz and residence times of 15, 240 and 480 s in 9 experimental runs. In a separate experimental set, moisture levels of 25, 50, 75, 100 and 125% were employed at the optimal operating conditions of 6 Hz and 480 s. A microscopy analysis was used to evaluate the shape descriptors. Pellets properties such as compressibility, friability, porosity, strength, flow rate and mass were also evaluated.Results: Pellets having a small size and a high value of shape descriptors related to morphology were obtained employing a spheronization rate and spheronization time of 6Hz and 480s and 100% wetting level. The spheronization time increased pellet densification but decreased the total porosity. Pellet mass was also favoured by using high spheronization rates. A high moisture level (>100%) rendered pellets having a large size, mass, low porosity and good yield. Conversely, pellet size decreased as sample load increased, whereas porosity and compressibility increased as sample load augmented.Conclusion: MCCII offers the potential for use as an alternative pelletization agent rendering pellets having a good flowability, high mechanical strength and low friability at the optimal operational conditions.

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Immunoferritin localization of intracellular antigens in positively stained frozen sections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008170x ◽

1978 ◽

Vol 36 (2) ◽

pp. 168-169

Author(s):

K. T. Tokuyasu

Keyword(s):

Surface Tension ◽

Water Surface ◽

Thin Layers ◽

The Other ◽

Positive Staining ◽

Frozen Sections ◽

The Past ◽

Ultrathin Frozen Sections ◽

Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

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The Critical Point Drying Method Applied to Scanning Electron Microscopy of L-929 Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100068382 ◽

1970 ◽

Vol 28 ◽

pp. 278-279

Author(s):

Charles TurnbiLL ◽

Delbert E. Philpott

Keyword(s):

Electron Microscopy ◽

Carbon Dioxide ◽

Surface Tension ◽

Critical Point ◽

Freeze Drying ◽

Attractive Alternative ◽

Crystal Formation ◽

Critical Point Drying ◽

Time Required ◽

Scanning Electron

The advent of the scanning electron microscope (SCEM) has renewed interest in preparing specimens by avoiding the forces of surface tension. The present method of freeze drying by Boyde and Barger (1969) and Small and Marszalek (1969) does prevent surface tension but ice crystal formation and time required for pumping out the specimen to dryness has discouraged us. We believe an attractive alternative to freeze drying is the critical point method originated by Anderson (1951; for electron microscopy. He avoided surface tension effects during drying by first exchanging the specimen water with alcohol, amy L acetate and then with carbon dioxide. He then selected a specific temperature (36.5°C) and pressure (72 Atm.) at which carbon dioxide would pass from the liquid to the gaseous phase without the effect of surface tension This combination of temperature and, pressure is known as the "critical point" of the Liquid.

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The Use of Styrenes as Embedding Media for Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066498 ◽

1971 ◽

Vol 29 ◽

pp. 488-489

Author(s):

Edward D. De-Lamater ◽

Eric Johnson ◽

Thad Schoen ◽

Cecil Whitaker

Keyword(s):

Electron Microscopy ◽

Surface Tension ◽

Ultraviolet Light ◽

Methyl Ethyl Ketone Peroxide ◽

Methyl Ethyl ◽

Styrene Polymerization ◽

Radical Initiation ◽

Tertiary Butyl ◽

Low Viscosity ◽

Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

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The nucleation of cavities at grain boundaries

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126299 ◽

1987 ◽

Vol 45 ◽

pp. 288-291

Author(s):

P. J. Goodhew

Keyword(s):

Surface Tension ◽

Surface Energy ◽

Grain Boundaries ◽

Radiation Damage ◽

Impurity Concentration ◽

Driving Force ◽

Nucleation And Growth ◽

Phase Boundaries ◽

Cavity Nucleation ◽

Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

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