Large porous particles

Fig. 3.1a. Silica particles used in hplc (/) Large porous particles...

The large porous particles are the oldest of these materials, and are no longer used in analytical hplc, although because of their high sample capacity they are still useful in preparative work. Columns packed with the large particles have relatively low efficiencies because of the long time it takes for solute species to diffuse into and out of the porous structure (slow mass transfer). 

N. and Langer, R. (1997) Large porous particle for pulmonary drug delivery. Science, 276,... 

Ben-Jebria A, Eskew ML, Edwards DA (2000) Inhalation systems for pulmonary aerosol delivery in rodents using large porous particles. Aerosol Sci Technol 32 421-433. 

Fiegel J, Ehrhardt C, Schaefer UF, Lehr CM, Hanes J (2003) Large porous particle impingement on lung epithelial cell monolayers—toward improved particle characterization in the lung. Pharm Res 20(5) 788-796. 

In an attempt to increase the amount of particles retained in the lungs, large porous particles with low density (p < 0.1 g/cm2) have been designed (Edwards et al. 1997). The particles were composed of 50% lactide and 50% glycolide. Porous and nonporous particles loaded with testosterone were aerosolized into a cascade impactor system from a dry powder inhaler (DPI) and the respirable fraction was measured. Nonporous particles (d = 3.5 pm, p = 0.8 g/cm3) exhibited a respirable fraction of 20.5 3.5%, whereas 50 + 10% of porous particles (d = 8.5 pm, p = 0.1 g/cm3) were respirable, even though the aerodynamic diameter of the two particle types were nearly identical. Porous particles as a consequence of their large size and low mass density can... 

Figure 8.14 Scanning electron micrograph of spray-dried large porous particles (airborne particles) developed by Alkermes. [From Peart and Clarke (2001). Reproduced with permission from Russell Publishing.]...

Edwards, D., Hanes, J., Caponetti, G., et al. Large porous particles for pulmonary drug delivery. Science 276 1868-1871, 1997. 

Vanbever, R., Mintzes, J. D., Wang, J., et al. Formulation and physical characterization of large porous particles for inhalation, Pharm. Res. 16 1735-1742, 1999a. 

A. Ben-Jebria, D. Chen, M. L. Eskew, R. Vanbever, R. Langer, and D. A. Edwards, Large porous particles for sustained protection from carbachol-induced broncho-constriction in guinea pigs, Pharm. Res. 16 555 (1999). 

Dunbar, C., Scheuch, G., Sommerer, K., DeLong, M., Verma, A., and Batycky, R. (2002), In vitro and in vivo dose delivery characteristics of large porous particles for inhalation, Int. J. Pharm., 245,179-189. 

Likewise, particles which appear to be visually of similar size and shape may have different aerodynamic diameter if their densities vary, and geometrically large porous particles can have aerodynamic diameters in the respirable range (between 1 and 5 pm), owing to their low density ... 

Interestingly, large porous particles have been found to be more appropriate than smaller, dense particles... 

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