Microencapsulation advantages

At present there is no reason evident why poly(N-acylhydroxy-proline esters) should not be suitable for the formation of microcapsules or microspheres as well. For microencapsulated drug fonmula-tions the longer degradation times of poly(N-acylhydroxyproline esters) as compared to poly (lactic acid) could again be a distinctive advantage for long-term applications. 

Sol-gel microencapsulation in silica particles shares the versatility of the sol-gel molecular encapsulation process, with further unique advantages. Sol-gel controlled release formulations are often more stable, potent and tolerable than currently available formulations. The benefits of microencapsulation can be customized to deliver the maximum set of benefits for each active ingredient. Overall, these new and stable combinations of active pharmaceutical ingredients (APIs) result in improved efficacy and usability. 

The so-called UCLA bioartificial liver involves the direct hemoperfusion of microencapsulated porcine hepatocytes in an extracorporeal chamber (Eigure 7.3). Since it permits perfusion with whole blood, it has an advantage over the hollow fiber technique that has to be perfused with plasma. The hepatocytes are isolated from pig livers and microencapsulated in an alginate-polylysine membrane. Microencapsulated hepatocytes are approximately 300 to 700 pm in diameter. 

With the recent advance of biotechnology and polymer chemistry, the use of microparticle systems will continue to grow for a variety of applications. The objective of this article is to provide a review of the technical aspects of the microencapsulation techniques that have been widely used in the pharmaceutical industry and recent advances of the technology so that the pharmaceutical scientists can take full advantage of the existing assets of this area in developing new microparticle systems. 

Debenedetti and coworkers (88,89) provided one of the first examples of microencapsulation of a drug in the polymeric matrix. Richard and coworkers (90) provided a recent example of the microencapsulation process when they produced microparticles with the encapsulated model protein that showed sustained release. Foster and coworkers (87) also reported precipitation of copper-indomethacin by PVP with a 96-fold enhancement in the dissolution rate of indomethacin. These examples clearly demonstrated the advantages of using supercritical fluid processing for the preparation of polymer-drug formulations with potentially improved therapeutic properties. 

Abstract. Three types of polymer-supported rare earth catalysts, Nafion-based rare earth catalysts, polyacrylonitrile-based rare earth catalysts, and microencapsulated Lewis acids, are discussed. Use of polymer-supported catalysts offers several advantages in preparative procedures such as simplification of product work-up, separation, and isolation, as well as the reuse of the catalyst including flow reaction systems leading to economical automation processes. Although the use of immobilized homogeneous catalysts is of continuing interest, few successful examples are known for polymer-supported Lewis acids. The unique characteristics of rare earth Lewis acids have been utilized, and efficient polymer-supported Lewis acids, which combine the advantages of immobilized catalysis and Lewis acid-mediated reactions, have been developed. 

This system might prove to be useful for the microencapsulation of various cores (drugs, oils, flavors, etc.), with the further advantage that NaCMC has demonstrated bioadhesive properties. 

Microencapsulation with complex coacervation has many advantages. It can produce capsules with a payload as high as 95%. The wall of the microcapsules is non-water soluble when it is either cross-linked with chemicals or treated with heat. This is a significant advantage over the microcapsules prepared with other technologies, such as spray drying or fluid bed coating by which the microcapsule wall produced is often water soluble. The microcapsules produced have excellent oxidation stability at low relative humidity, and core release can be initiated by different mechanisms. 

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