(481h) Response Studies of Microcapsules to pH, Ionic Strength and Osmotic Pressure

Microcapsules find wide-ranging applications in pharmaceutical, food, and consumer industry by serving as miniature containers to store, deliver, and release substances. Nanoparticle-assembled capsules (NACs) are one such model structure, which we can prepare through nanoparticle (NP) assembly on polymer-salt aggregates [1-5]. In this polymer-salt aggregate templating route, a solution of linear cationic polymer like poly (allylamine hydrochloride) is combined with a multivalent anionic salt solution, to form a suspension of salt-bridged polymer aggregates. An aqueous suspension of NPs, such as silica NPs, is then added to form polymer-filled capsules, water-filled capsules or polymer/inorganic solid spheres, depending on the synthesis conditions. This electrostatically-driven route is attractive for scale-up of microcapsule synthesis because the formation reaction occurs in water at mild pH values and at room temperature.

NACs containing macromolecules such as enzymes and drugs are difficult to release unless one takes definite measures to unlock or break open the capsule. This measure can be achieved by tuning the responsive parameters such as pH, ionic strength and osmotic pressure. The objective of study is to gain an understanding of the behavior of NACs in response to pH, ionic strength and osmotic pressure. As an illustration, capsules can be made either polymer filled or water filled by changing pH between 3 and 10. On the other hand, outside this pH range NACs can be dissembled. Similar controlled studies were performed by changing the ionic strength with NaCl and changing the osmotic pressure [6] with poly(styrenesulfonate sodium salt) and poly(ethylene glycol). Understanding the sensitivity of NACs towards the various conditions would help in better understanding and perhaps tailoring their properties for drug delivery and controlled release.

Keywords: Microcapsule, hollow, nanoparticle, NACs

References:

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[2] V. S. Murthy et al., J. Phys. Chem. B., 110 (51), 25619 -25627 (2006)

[3] J. Yu et al., Chem. Commun. 10, 1097-1099 (2006)

[4] J. Yu et al., Chem. Mater. 19(6), 1277 ? 1284(2007)

[5] S. B. Kadali et al., Topic. Catal, accepted (2008)

[6] C. Gao, et. al., Eur. Phys. J. E., V5, 21(2001)