Microspheres spray drying

Microspheres Spray drying Carbamazepine Chitosan In sheep Increased drug dissolution 25... 

FIGURE 19.10 Silica porous microspheres spray dried 5 W/O aqueous slurry of Cab-O-Sil EH—5 rotary atomizer 45M RPM. 

Engelhard s in-situ FCC catalyst technology is mainly based on growing zeolite within the kaolin-based particles as shown in Figure 3-9A. The aqueous solution of various kaolins is spray dried to form micR)spheres. The microspheres are hardened in a high-temperature l,3f)(TF/704°C) calcination process. The NaY zeolite is produced by digestion of the microspheres, which contain metakaolin, and mullite with caustic or sodium silicate. Simultaneously, an active matrix is formed with the microspheres. The crystallized microspheres are filtered and washed prior to ion exchange and any final treatment. 

Spray-drying of chitosan salt solutions provides chitosan microspheres having diameters close to 2-5 p.m and improved binding fimctionaUty. The chitosan microsphere free-flowing powder is compressible and hence most suitable as a drug carrier [ 195-204]. The following are some examples. 

Chitosan has been recently found to be soluble in alkaline media, viz. NH4HCO3 solutions, where it assumes the ammonium carbamate form Chit-NHC02 NH4, i.e., a transient anionic form that keeps it soluble at pH 9.6, while reversibly masking the polycationic nature of chitosan. Because ammonium carbamates and NH4HCO3 decompose thermally and liberate CO2, NH3 and water, this alkaline system is suitable for producing chitosan microspheres by spray-drying (Table 1) [206]. 

For the preparation of spray-dried polyelectrolyte complexes, the polyanion was dissolved in dilute NH4HCO3 solution and mixed with the chitosan carbamate solution just before spray-drying. The excess NH4HCO3 decomposed thermally between 60 and 107 °C on the other hand, the carbamate function released carbon dioxide under the effect of the temperature at which the spray-drier was operated, thus regenerating chitosan at the moment of the polyelectrolyte microsphere formation (Fig. 5). 

The emulsion technique is convenient when the drug is particularly sensitive to certain parameters connected to the spray-drying. The emulsion technique may be associated to cross-Unking or other treatments of the microspheres. The following examples are self-explanatory. 

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). 

Grattard, N., Pernin, M., Marty, B., Roudaut, G., Champion, D. and Le Meste, M. (2002) Study ofrelease kinetics of small and high molecular weight substances dispersed into spray-dried ethylcellulose microspheres. Journal of Controlled Release, 84, 125-135. 

PCA [Precipitation with a compressed anti-solvent] A process for making a solid with unusual morphology by spraying a solution of it into a supercritical fluid. The process resembles spray drying into a supercritical fluid. Used for making microspheres, microporous fibers, and hollow microporous fibers. 

A significant recent advance has been the development of microfiltration and ultrafiltration membranes composed of inorganic oxide materials. These are presently produced by two main techniques (a) deposition of colloidal metal oxide on to a supporting material such as carbon, and (b) as purely ceramic materials by high temperature sintering of spray-dried oxide microspheres. Other innovative production techniques lead to the... 

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). 

Microspheres by solvent extraction method were obtained with rate of mixing equal 300 rev/s. Particles by spray drying were produced with spray dryer operated with an inlet temperature of 50°C and outlet temperature of 45°C. The air flow indicator was set at 700 and the aspirator at 5. The polymer solution (concentration 0.5% wt/v) was supplied at 10 mL/min. The concentrations of monomer, initiator, and surfactant in ring-opening dispersion polymerization leading to microspheres were as follows [Lc]o = 2.77 10 mol/L, [tin(II) 2-ethyUiexanoate]o = 4.9 10 mol/L, [poly(DA-CL)] = 1.6 g/L. 

Attempts to obtain regular spherical shaped particles by spray drying were unsuccessful. Apparently, collisions of not completely solidified particles in the jet stream supplying primary droplets into the drying chamber result in their coalescence and/or distortion of shape. The perspective of obtaining microspheres with well-controlled shape, diameter, and diameter... 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

Silica-based microspheres are typically between 5 and 200 j,m in diameter, have wall thicknesses of 0.5-20 pm and can be filled with up to 100 M Pa of H2. The spheres are formed by melting spray-dried microparticles in free fall and the evolving gases... 

Desai, K.G., Park, H.J. (2005). Encapsulation of vitamin C in tripolyphosphate cross-linked chitosan microspheres by spray drying. Journal of Microencapsulation, 2, 179-192. 

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. 

Spray drying. Microencapsulation by spray drying is an ideal method for poorly water-soluble drugs. The drug is dispersed in polymer (coating) solution, and then this dispersion is atomized into an airstream. The air, usually heated, supplies the latent heat of vaporization required to remove the solvent and forms the microencapsulated product. This technique is employed most commonly when microcapsules are intended for oral use because the resulting microspheres are porous in nature, and large batch sizes are required.89... 

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. 

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