Microspheres microsphere preparation

The soapless seeded emulsion copolymerization method was used for producing uniform microspheres prepared by the copolymerization of styrene with polar, functional monomers [115-117]. In this series, polysty-rene-polymethacrylic acid (PS/PMAAc), poly sty rene-polymethylmethacrylate-polymethacrylic acid (PS/ PMMA/PMAAc), polystyrene-polyhydroxyethylmeth-acrylate (PS/PHEMA), and polystyrene-polyacrylic acid (PS/PAAc) uniform copolymer microspheres were synthesized by applying a multistage soapless emulsion polymerization process. The composition and the average size of the uniform copolymer latices prepared by multistage soapless emulsion copolymerization are given in Table 11. 

The ability of chitosan hydrochloride to enhance the transcorneal permeability of the drug has been demonstrated [289]. Polyethylene oxide (PEO) was used as a base material to which ofloxacin-containing chitosan microspheres prepared by spray-drying were added and powder compressed resulting in circular inserts (6 mm). 

Extensive studies have been reported with cisplatin in the field of chemoembolization (59,98). Microspheres prepared by a solvent evaporation procedure were characterized in vitro and critical processing parameters in regard to drug release kinetics were identified. 

Several antiinflammatory compounds have been formulated in lactide/ glycolide polymers (107-111). Methylprednisolone microspheres based on an 85 15 DL-lactide/glycolide copolymer were developed for intra-articulate administration (111). The microspheres, prepared by a solvent evaporation procedure, are 5—20 jam in diameter and are designed to release low levels of the steroid over a extended period in the joint. Controlled experiments in rabbits with induced arthritis showed that the microspheres afforded an antiinflammatory response for up to 5 months following a single injection. 

Spenlehauer, G., Vert, M., Benoit, J. P., Chabot, F., and Veillard, M., Biodegradable cisplatin microspheres prepared by the solvent evaporation method Morphology and release characteristics, J. Control. Rel., 7, 217, 1988. 

Epirubicin, a successor to adriamycin, was studied in ovalbumin microspheres (115). The microspheres, prepared by a heat denatu-ration process, were 20 ym in diameter and contained 12.5% drug. 

Magnetically responsive gelatin microspheres, prepared using methods adopted from albumin preparations (161), were evaluated... 

J Herrmann, R Bodmeier. Biodegradable somatostatin acetate containing microspheres prepared by various aqueous and non-aqueous solvent evaporation method. Eur J Pharm Biopharm 45(l) 75-82, 1998. 

Fig. 10 Release of cromolyn sodium (sodium cromoglycate) from human serum albumin microspheres prepared using a water-oil emulsion technique with 5% glutaraldehyde as cross-linking agent. Dissolution medium pH 7 phosphate buffer. (From Ref. 98.)... 

Kubo A, Shinmori H, Takeuchi T (2006). Atrazine-imprinted microspheres prepared using a microfluidic device. Chem Lett 35 588-589... 

S. Harikarnpakdee, V. Lipipun, N. Sutanthavibul, and G. C. Ritthidei. Spray-dried mucoadhesive microspheres Preparation and transport through nasal cell mono-layer. AAPS PharmSciTech 7 E12 (2006). 

Akiyama, Y., Nagahara, N., Kashihara, T., Hirai, S., and Toguchi, H., In vitro and in vivo evaluation of mucoadhesive microspheres prepared for the gastrointestinal tract using polyglycerol esters of fatty acids and a poly(acrylic acid) derivative, Pharm. Res., 12 397-405... 

Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the drug incorporation and surface shape of the microspheres prepared under the various conditions. Particle size was determined using a Tiyoda microscope. Samples of microspheres (180-200) were dispersed on a slide and their diameter was then sized using suitable objectives. 

The approach used to resolve the various technical problems was based on the decision that the minimal amount of microspheres prepared per batch would be 25 g. 

Veronese, F.M., Marsilio, E, Caliceti, P, De Filiis, P, Giunchedi, P, and Lora, S. (1998). Polyorganophosphazene microspheres for drug release polymer synthesis, microsphere preparation, in vitro and in vivo naproxen release. J. Control. Release, 52, 221-237. 

Giunchedi P, Gavini E, Bonacucina G, Palmieri GF. Tabletted polylactide microspheres prepared by a w/o emulsion-spray drying method. J Microencapsul 2000 17(6) 711-720. 

Liquid fluorocarbon was used as continuous phase by Perez-Moral and Mayes [19] as well. They proposed a new method for rapid synthesis of MIP beads, in that they prepared 36 polymers imprinted for propranolol and morphine with different amounts of EDMA as a cross-linker and different functional monomers (MAA, acrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine) directly in SPE cartridges. The properties of MIP microspheres prepared by this method were very similar in terms of size, morphology and extent of rebinding to microspheres prepared by conventional suspension polymerisation in perfluorocarbons as well as to bulk polymers prepared in the same solvent. The most notable advantages of this method are no waste production (no transfer of beads during washing steps) and possible direct use for a variety of screening, evaluation and optimisation experiments. 

Bodmeier, R., Wang, H., Dixon, D. J., et al. Polymeric microspheres prepared by spraying into compressed carbon dioxide. Pharm. Res. 12(8) 1211—1217, 1995. 

Wang, F. J., and Wang, C. H. Sustained release of etanidazole from spray dried microspheres prepared by non-halogenated solvents. J. Contr. Rel. 81(3) 263—280, 2002. 

Bittner, B., Mader, K., et al. Tetracycline-HCl-loaded poly(DL-lactide-co-glycolide) microspheres prepared by a spray drying technique influence of gamma-irradiation on radical formation and polymer degradation. J. Contr. Rel. 59(1) 23—32, 1999. 

Polyelectrolyte multilayer microspheres, prepared by alternating adsorption of dextran sulfate and protamine on melamine formaldehyde cores followed by the partial decomposition of the core, were used to immobilise the peroxidase and glucose oxidase. Retention of enzymic activity of the peroxidase/glucose oxidase system incorporated into the microspheres was demonstrated. These bienzyme system immobilised in the microspheres can be applied for kinetic glucose assays [ 156]. 

Pharmaceutical research has to date been focused on polyanhydrides derived from sebacic acid (SA) and its copolymers with bis(p-carboxyphenoxy)propane (CPP) [75,113,115,119]. More recently, a new class of polyanhydrides was presented, containing fatty acid dimers (FAD) [ 116,118,258]. Erosion characteristics, microsphere preparation, pH-dependence, release rates, morphology, and in vivo performance of polyanhydrides from SA, CPP, and FAD have been intensely studied [75, 111-115,117, 119, 258-260]. Other unsaturated polyanhydrides have been derived from ricinoleic acid [261] and ricinoleic acid half-es-... 

Fig. 15. Schematic illustration of microsphere preparation by oil-in-water (O/W) solvent...

When emulsion techniques are used for microsphere preparation, a number of processing factors influences the final structure of the microspheres, e.g., the choice of solvents and surfactants, phase viscosity, the ratio of the dispersed to the continuous phase, mixing speed, processing temperature, and time. Micro-... 

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