title: UV-screening chitosan nanocontainers: increasing the photostability of encapsulated materials and controlled release.
abstract: Methyl ether terminated poly(ethylene glycol)-4-methoxycinnamoylphthaloylchitosan (PCPLC), a UV absorptive polymer, and methyl ether terminated poly(ethylene glycol)-phthaloylchitosan (PPLC) were synthesized, characterized and self-assembled into stable water-dispersible spherical nanoparticles. The encapsulation of a model compound, 2-ethylhexyl-4-methoxycinnamate (EHMC), was carried out to give particles with 67% (w/w) EHMC loading. The E to Z photoisomerization of EHMC encapsulated inside both particles was monitored and compared to non-encapsulated EHMC. Minimal E to Z photoisomerization was observed when EHMC was encapsulated in PCPLC particles prepared from a polymer with a maximum degree of 4-methoxycinnamoyl substitution. The results indicated that the grafted UVB absorptive chromophore, 4-methoxycinnamoyl moieties, situated at the shell of PCPLC nanoparticles acted as a UV-filtering barrier, protecting the encapsulated EHMC from the UVB radiation, thus minimizing its photoisomerization. In vitro experiments revealed the pH-dependent controlled release of EHMC from PCPLC and PPLC particles. Ex vivo experiments, using a Franz diffusion cell with baby mouse skin, indicated that neither PPLC nor PCPLC particles could penetrate the skin into the receptor medium after a 24 h topical application. When applied on the baby mouse skin, both EHMC-encapsulated PPLC and EHMC-encapsulated PCPLC showed comparable controlled releases of the EHMC. The released EHMC could transdermally penetrate the baby mouse skin.
authors.affiliation: The Petrochemistry and Polymer Science Program, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Nattaporm
authors.initials: N
authors.lastname: Anumansirikul
authors.forename: Mayura
authors.initials: M
authors.lastname: Wittayasuporn
authors.forename: Patcharawalai
authors.initials: P
authors.lastname: Klinubol
authors.forename: A
authors.initials: A
authors.lastname: Tachaprutinun
authors.forename: Supason P
authors.initials: SP
authors.lastname: Wanichwecharungruang