Homogenizer encapsulation efficiency

Table 1 Encapsulation efficiency and entrapped volumes of vesicles prepared using a high-pressure homogenizer...

Qiang Zhang et al. prepared stearic acid nanoparticles loaded with cyclosporin A by the classical and simple melt - homogenization method. The mean size and encapsulation efficiency of the cyclosporin A stearic acid nanoparticles are 316.1 run and 88.36%, respectively. In addition, no chemical reaction between cyclosporin A and stearic acid was observed, and the nanoparticles exhibited improved bioavailability and sustained drug release property [9]. Woo JO et al. improved this technique to prepare salicylic acid loaded nanoparticles, wherein they combined stearic acid and oleic acid in the lipid phase and prepared the nanoparticles by melt emulsification method and further ultrasonication technique. In this formulation, different amount of oleic acid contributed to different degrees of crystallinity of the nanoparticles matrix, thereby improving the encapsulation efficiency. 

With the comprehensive research base that has developed in this area, if therapeutic peptides or proteins can be successfully and, to some extent, economically microencapsulated to produce a homogeneous and stable dmg delivery system, the potential for a successful system is unchallengeable. However, although many systems are in the process ofpreclinical and even early clinical trials, there are still many issues in this field that need to be addressed and resolved. Certain studies are performed with compounds that, for a number of reasons, are not viable commercially for oral delivery, usually because of related issues such as dose, cost, and encapsulation efficiency. Although many such studies are cited as proof of concept, it is extremely difficult to define a model peptide or protein with which to optimize a delivery system. Detailed scientific information on mechanisms of action is also lacking in many circumstances and, if available, would allow logical approaches to system optimization and ultimately potential widespread system application. 

In these studies, polymeric nanocapsules with encapsulated dsDNA (790 base pairs) were produced via anionic polymerization of n-butylcyanoacrylate (BCA) carried out at the interface of homogeneously distributed aqueous droplets in inverse miniemulsion which are in a second step then redispersed in an aqueous continuous phase. The obtained capsules were characterized in terms of size, size distribution, morphology, polymer molecular weight, and encapsulation efficiency of DNA. The effects of surfactant type and concentration, viscosity of the continuous phase, monomer amount, and water-to-oil ratio were investigated and results are discussed in this paper. 

Vladisavljevic et al. (2004b) prepared monodisperse W/O/W emulsions for controlled delivery systems by repeated SPG homogenization. A coarse W/O/W emulsion was passed five times through SPG membrane with a mean pore size of 10.7 gm using the equipment shown in Figure 6.10. The encapsulation efficiency of a marker substance (CaNa2-EDTA) in freshly prepared samples after five passes was 83% to 84% at the transmembrane fluxes exceeding 20m m h . Under optimal conditions the span of the particle size distribution of external droplets in the product emulsions was as low as 0.28. 

Nanospheres of PLGA were prepared by emulsion-evaporation by employing homogenization and a solvent system consisting of acetone in which both the drug and polymer were dissolved [95], The encapsulation of 5FU in these nanospheres was low compared to the more hydrophobic drug, indomethacin. It was reported that the hydrophilic 5FU leaked to the aqueous phase. PGL nanoparticles were prepared by aldol condensation loading 5FU with an efficiency of 14.32% [50]. 

At the same time, one has to consider that the FePc complex is only a finely dispersed powder in the reaction mixture and the reaction most likely occurs via heterogeneous catalysis. It means that it is also possible that not the zeolite encapsulated catalyst has increased specific catalytic activity but the poor solubility of the free complex decreases its efficiency in homogeneous circumstances. 

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