Impact of chemistry on the preparation and post-modification of multilayered hollow microcapsules.

In the last few years, various chemical bondings and interactions were rationally adopted to develop different multilayered microcapsules, where the empty interior accommodated various important cargoes, including bioactive molecules, nanoparticles, antibodies, enzymes, etc., and the thin membrane protected/controlled the release of the loaded cargo. Eventually, such materials are with immense potential for a wide range of prospective applications related to targeted drug delivery, sensing, bio-imaging, developing biomimetic microreactors, and so on. The emphasis on the use of various chemistries for the development of functional and useful microcapsules is rarely illustrated in the literature in the past. In this feature article, the rational uses of different chemistries for (a) preparing and (b) post-modifying various functional microcapsules are accounted. The appropriate selection of chemical bondings/interactions, including electrostatic interaction, host-guest interaction, hydrogen bonding, and covalent bonding, allowed the integration of essential constituents during the layer-by-layer deposition process for 'in situ' tailoring of the relevant and diverse properties of the hollow microcapsules. Recently, different chemically reactive hollow microcapsules were also introduced through the strategic association of 'click chemistry', ring-opening azlactone reaction, thiol-ene reaction, and 1,4-conjugate addition reaction for facile and desired post covalent modifications of the multilayer membrane. The strategic selection of chemistry remained as the key basis to synthesize smart and useful microcapsules.