Preventing the thermal degradation of astaxanthin through nanoencapsulation

The encapsulation of astaxanthin into polymeric nanospheres by solvent displacement was compared for three chemically diverse polymers, namely; poly(ethylene oxide)-4-methoxycinnamoylphthaloylchitosan (PCPLC), poly(vinylalcohol-co-vinyl-4-methoxycinnamate) (PB4) and ethylcellulose (EC). Although capable of forming nanospheres themselves, EC could not encapsulate astaxanthin at all, whilst PB4 yielded a poor encapsulation efficiency. In contrast, PCPLC yielded reasonably good encapsulation efficiency (98%) at a loading of 40% (w/w). Moreover, the freeze-dried astaxanthin-encapsulated PCPLC nanospheres showed good dispersibility in water yielding stable aqueous suspensions of 300–320 nm nanoparticles. A steady release of astaxanthin from the nanospheres up to a maximum of ∼85% payload over 60 min was also demonstrated, at least in acetone. NMR analysis indicated that after a two-hour-heating at 70 °C in an aqueous environment, PCPLC nanoencapsulated astaxanthin showed minimal heat degradation of olefinic functionality in contrast to that of the unencapsulated pigment molecules which were almost completely destroyed.