Microspheres suspensions

MA Ramadan, R Tawashi. Effect of surface geometry and morphic features on the flow characteristics of microsphere suspensions. J Pharm Sci 79 929-933, 1990. 

Parenteral depot polymeric delivery system 7.5, 22.5, 30, 45 mg in a single-dose kit for subcutaneous injection Parenteral depot microspheres suspension 3.75, 7.5, 11.25, 15, 22.5, 30 mg in a single-dose kit for IM injection Lutropin [rLH] (Luveris)... 

Shenoy, D. B., D Souza, R. J.,Tiwari, S. B., and Udupa, N. (2003), Potential applications of polymeric microsphere suspension as subcutaneous depot for insulin, Drug Dev. Ind. 

Ramadan, M.A. Tawashi, R. Effects of surface geometry and morphic features on the flow characteristics of microspheres suspensions. J. Pharm. Sci. 1990, 79 (10), 929-932. Suzuki, T. Yano, T. Fractal surface structure of food materials recognized by different molecules. Agric. Biol. Chem. 1991, 55 (4), 967-971. 

Leuprolide acetate IM (microsphere suspension) After reconstitution 0.13% Gelatin 6.6% dl-Lactic and glycolic acid copolymer 13% Mannitol 0.2% Polysorbate 80 1% Carboxymethylcellulose in WFI... 

To fill voids with a short, rigid material (latex or vinyl with a microsphere suspension)... 

When all components of the head were reintegrated and the surface configuration was completed, the head was coated with a heavy latex-microsphere suspension (Figure 31). This coating provided a UV-radia-tion-stable surface, protected the not-UV-stable foam, and permitted further contouring. 

To study the flow within the capillaries, the aqueous phase was seeded with fluorescent microsphere suspensions at 1 % concentration by weight (Thermo Scientific). The fluorescent micro-spheres are made of polystyrene and were dyed with red or blue fluorescent dyes. The refractive index and the density are 1.59 and 1.06 g cm, respectively. The spectral properties of the fluorescent microspheres are shown in Table 3.3. The size of the particles varied between 1 and 3.2 pm depending on the channel size. 

An example of such a product is Sterile Medroxyprogestrone Acetate Suspension used for its contraceptive property. Such an injection is designed to provide up to three months of contraceptive activity. Another such product is a depot injection of leuprolode acetate, an analogue of gonadatropin-releasing hormone (see Drug delivery systems). In this case, the product is a sterilized powder of microspheres to be suspended upon the addition of an appropriate diluent and intended for monthly injection. 

Two-phase suspension systems produce beaded products with broader particle-size distribution (e.g., 1-50 /rm). The microspherical particles usually need to be classified repeatedly to reduce the particle-size distribution in order to improve the resolution and efficiency in the separation for use in chromatography. The actual classification process depends on the size range involved, the nature of the beaded product, and its intended applications. Relatively large (>50 /rm) and mechanically stable particles can be sieved easily in the dry state, whereas small particles are processed more conveniently in the wet state. For very fine particles (<20 /rm), classification is accomplished by wet sedimentation, countflow setting, countflow centrifugation, or air classification. 

Various novel applications in biotechnology, biomedical engineering, information industry, and microelectronics involve the use of polymeric microspheres with controlled size and surface properties [1-31. Traditionally, the polymer microspheres larger than 100 /urn with a certain size distribution have been produced by the suspension polymerization process, where the monomer droplets are broken into micron-size in the existence of a stabilizer and are subsequently polymerized within a continuous medium by using an oil-soluble initiator. Suspension polymerization is usually preferred for the production of polymeric particles in the size range of 50-1000 /Ltm. But, there is a wide size distribution in the product due to the inherent size distribution of the mechanical homogenization and due to the coalescence problem. The size distribution is measured with the standard deviation or the coefficient of variation (CV) and the suspension polymerization provides polymeric microspheres with CVs varying from 15-30%. 

A solid emulsion is a suspension of a liquid or solid phase in a solid. For example, opals are solid emulsions formed when partly hydrated silica fills the interstices between close-packed microspheres of silica aggregates. Gelatin desserts are a type of solid emulsion called a gel, which is soft but holds its shape. Photographic emulsions are gels that also contain solid colloidal particles of light-sensitive materials such as silver bromide. Many liquid crystalline arrays can be considered colloids. Cell membranes form a two-dimensional colloidal structure (Fig. 8.44). 

The culture broth was recovered after 72 h of fermentation, the biomass removed and the total protein content measured. Broth aliquots with a protein content of 1 mg were collected and their pH regulated at different values ranging from 3.5 to 8.0. To each broth fraction, 50 mg of the microspheres sample, previously equilibrated at the corresponding pH, was added and the suspension left under stirring overnight. Then, the microspheres were removed by centrifugation and the protein content and the PG activity were assayed on the resulting supernatant. 

Figure 12.2 AFM images of a PS-fo-P4VP (301 000 19 600) film after immersion in a microsphere/methanol ((a) 20nm, (b) 50 nm) suspension for 75 min and rinsing in methanol for 90 min and the height profiles. S. Machida, H. Nakata, K. Yamada, A. Itaya Position-selective...

Fig. 6 (a) Schematic illustration of a flow cytometer used in a suspension array. The sample microspheres are hydrodynamically focused in a fluidic system and read-out by two laser beams. Laser 1 excites the encoding dyes and the fluorescence is detected at two wavelengths. Laser 2 is used to quantify the analyte, (b) Scheme of randomly ordered bead array concept. Beads are pooled and adsorbed into the etched wells of an optical fiber, (c) Scheme of randomly-ordered sedimentation array. A set of encoded microspheres is added to the analyte solution. Subsequent to binding of the analyte, microparticles sediment and assemble at the transparent bottom of a sample tube generating a randomly ordered array. This array is evaluated by microscope optics and a CCD-camera. Reproduced with permission from Refs. [85] and [101]. Copyright 1999, 2008 American Chemical Society... 

The coprecipitation technique was based on the dropwise addition of a synthetic polymer solution, in a solvent mixture, into an aqueous protein solution under magnetic stirring. The progressive interaction between the water insoluble polymer and the protein gave rise to the microsphere formation. The glycolipid was then added as an aqueous dispersion to the nanoparticle suspension. No sedimentation was observed after several weeks of storage at room temperature. 

Morphological analysis of the nanoparticle suspensions by SEM showed a homogeneous distribution of spheroidal particles with diameters less than 1 pm embedded in a continuous matrix (Figure 4) consisting of polymeric material not incorporated within the microspheres. 

The nanoparticle suspensions were centrifuged three times at 8,000 rpm for 15 minutes. After each centrifugation the pellets were resuspended in double-distilled water. However, SEM analysis of the pellets showed extensive aggregation-fragmentation of the microspheres (Figure 5), that... 

---