Natural microshells of alginate–chitosan: Unexpected stability and permeability

We utilized alginate sodium (ALG) and chitosan (CHI) as wall components to construct a natural and biodegradable polyelectrolyte microshell by the electrostatic self-assembly technique. The resultant ALG–CHI shells were found to maintain intact spherical shape in different poly(styrenesulfonate sodium) (PSS) bulk concentrations (maximal detection concentration 20.0 wt%). Compared with the shells composed of PSS and poly(allylamine hydrochloride) (PAH) that collapse or deform at a 4 wt% or more than 4 wt% PSS concentration, the ALG–CHI shells display higher stability. Meanwhile, the permeability of the ALG–CHI shells prior to and after incubation in PSS solutions was directly traced by the fluorescence recovery after photobleaching (FRAP). The composition of the ALG–CHI shells themselves is thought to be responsible for the differences in the stability.