Excipient encapsulation efficiency

Encapsulation involves the incorporation of active ingredients such as flavors, enzymes, cells or other materials in small capsules. The choice of excipients for encapsulation is very important for the encapsulation efficiency and protein stability within the matrix. Applications of this technique have increased in the food and pharmaceutical industries since the encapsulated materials can be protected from moisture, heat or other extreme conditions. Thus their stability is improved and their viability maintained. Powder formation can lower the water activity of the material, the reactivity and the diffusivity of encapsulated compounds, and the diffusivity of residual water. In the food industry microencapsulation is often associated with the already discussed retention of flavor compounds during drying and storage. In pharmaceutical applications, the purpose of microencapsulation is to control the release and improve the bioavailability of active ingredients. 

Pure carbon spheres of Cf,(l the fullerenes—react avidly with free radicals with a higher antioxidant ability than the naturally occurring vitamin E (21). Endohedral fullerenes have been shown to be capable of encapsulating a variety of atoms such as radiotracers or noble gases, thereby making them efficient excipients in the delivery of radioisotopes to cancer cells or in magnetic resonance imaging (MRI) (22). 

Tetanus toxoid (the vaccine for tetanus) encapsulated in polyester microspheres was produced for single-injection immunization. The entrapment efficiency of the protein vaccine was significantly improved by coencapsulation with excipients such as trehalose and y-hydroxypropyl cyclodextrin. However, these excipients did not impart stabilizing effect on tetanus toxoid. In contrast, bovine serum albumin was foimd to be the most prominent stabilizer for protein in the body after administration by injection. 

The capsule has the potential to be an efficient drug delivery system. The hard gelatin shell encapsulating the formulation should disrupt quickly, and expose the contents to the G1 fluid, provided that excipients in the formulation and/or the method of manufacture do not impart a hydrophobic nature to the dosage form. 

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