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Biomedical subjects

M L Shively

Publications and source records attributed to M L Shively.

6 recordsLinked to original sources
PubMed1997

Multiple emulsions for the delivery of proteins.

Multiple emulsions are unique in that a true liquid phase is maintained separate from an external aqueous phase. This may be especially important for bioactive molecules that cannot be appropriately stabilized in the solid state. In addition, the separation of aqueous phases enables highly specialized environments, conducive to protein activity, to be prepared. The physical instability of conventional systems remains a major factor limiting their wider application. Attempts to improve the physical stability of the aqueous dispersions through interfacial complexation and the use of micro-emulsions are improving the short-term stability. As an alternative approach, solid-state emulsions attempt to store the multiple emulsion as a solid. Although solid-state emulsions appear to have the potential to be useful protein delivery systems, a substantial experimental data base has yet to be generated.

Adjuvants, Immunologic↗
PubMed1994

Solid-state emulsions: evaluation by 1H and 13C solid-state nuclear magnetic resonance.

The molecular environment of sucrose and mineral oil within sucrose and mineral oil solid state emulsions was investigated by NMR techniques. The 13C and 1H chemical shifts of sucrose and mineral oil to those observed in solid state emulsions (comprised of sucrose and mineral oil) were equivalent, indicating that the local structure of sucrose is unaffected by the presence of mineral oil in the solid-state emulsion. Cross-polarization, magic angle spinning 13C (CP-MAS) in conjunction with single-pulse studies indicated that the 1H-13C dipole-dipole interactions are very weak, i.e., mineral oil is highly mobile. Spinning side bands were observed, however, in 1H single-pulse, magic angle spinning (SPMAS) spectra of the solid-state emulsion, indicating that the mineral oil has solid properties. Although the mineral oil was shown to be highly mobile, it also appears to be constrained or included by the sucrose.

Emulsions↗
PubMed1993

Characterization of oil-in-water emulsions prepared from solid-state emulsions: effect of matrix and oil phase.

Emulsions (o/w) were prepared from solid-state emulsions comprised of various matrix materials and oils and the resultant particle size properties determined. Results suggest that for those matrices that can form solid-state emulsions, the droplet size decreased as a function of time, as previously observed. The final droplet size was dependent on the oil utilized but was independent of the matrix material. The use of mineral oil resulted in the smallest droplet diameter (approximately 1.5 microns) while isopropyl myristate resulted in the largest droplet diameter (approximately 3 microns). With the exception of mineral oil, the oil/water interfacial tension was found to be directly proportional to the droplet diameter. The rate of emulsification appeared to be biphasic. The initial emulsification phase appeared to be independent of the matrix material while the terminal phase was a function of the matrix material. Most importantly, it was found that solid state emulsions could be prepared from a diverse, yet specific, list of matrices.

Chemical Phenomena↗
PubMed1993

Solid-state emulsions: the effects of process and storage conditions.

The effects of process and storage conditions of solid-state emulsions were studied. Oil-in-water emulsions may be prepared from solid state emulsions by adding an aqueous phase to the solid. Solid-state emulsions are prepared by processing an oil phase and an aqueous solution of matrix material via a solvent removal process. Sucrose, the carrier material utilized in this report, results in a metastable solid or glass, which can transform upon aging to a more stable thermodynamic state. Aging was determined by monitoring the crystallinity as a function of time, temperature, relative humidity, and grinding. The crystallinity of solid-state emulsions was determined with X-ray diffraction and differential scanning calorimetry. Results indicate that solid-state emulsions should be stored between 15 and 25% relative humidity at 25 degrees C. Grinding has no apparent effect on the crystallinity of the sample, as detected by X-ray diffraction, although the microcrystallinity is increased. The utilization of silinized glassware enabled the sample-to-sample microcrystalline variability to be reduced.

Calorimetry, Differential Scanning↗
PubMed1991

Analysis of mercury porosimetry for the evaluation of pore shape and intrusion-extrusion hysteresis.

The use of mercury porosimetry to determine pore size and pore distribution is currently applied in a variety of areas where powders or membranes are utilized. Conventional analysis of mercury porosimetry data assumes a cylindrical pore configuration. The method of analysis presented in this study requires no geometrical assumptions to be made and provides a means to graphically delineate between different pore geometries. This method of analysis also provides data that shows evidence for the existence of different pore shapes within the same sample, where only cylindrical pores have been assumed in the past. Furthermore, this method of analysis makes it possible to evaluate intrusion and extrusion data and to postulate as to the validity of contact angle and volume hysteresis.

Chemistry, Physical↗