(397ay) Nanocapsulation of Ascorbyl Dipalmitate in Chitosan Via Rapid Expansion of Subcritical Solutions Followed By Ionic Crosslinking

Ascorbyl dipalmitate (ADP) nanoparticles encapsulated in chitosan were successfully produced by rapid expansion of subcritical solution (RESOLV) process followed by ionic crosslinking with chitosan-tripolyphosphate.  The rapid expansion of supercritical solution process provided ADP nanoparticles, while ionic crosslinking at the particle surface with chitosan-tripolyphosphate imparted coating and/or encapsulation of the ADP nanoparticles with chitosan.  In general, ADP nanoparticles obtained from RESOLV were spherical with a narrow size distribution between 30 and 70 nm, independent of ADP concentration, pre-expansion temperature and pressure, as well as tripolyphosphate concentration.  Encapsulating ADP nanoparticles in chitosan slightly increased the particle sizes to ~40-90 nm.  The size of ADP nanoparticles encapsulated in chitosan were unaffected by changes in concentration and content of chitosan solution.  However, increasing the concentration and content of chitosan solution led to increased amount of chitosan in the coating layer and decreased the fraction of ADP in the nanocapsules.  Increasing ADP concentration and pre-expansion temperature and pressure did not significantly influence on the size of nanoparticles but increased the degree of particle agglomeration instead.

To obtain ADP nanoparticles coated by chitosan with a narrow size distribution and high loading content of ADP, suitable RESOLV processing conditions, i.e. low pre-expansion temperature and pressure as well as ADP concentration, are required to consistently produce ADP nanoparticles with less degree of particle agglomeration.  In addition, suitable encapsulation/coating conditions, i.e. low concentration and amount of chitosan solutions, are also required to obtain high loading capacity of ADP.  It is possible to control the loading content of ADP in nanoparticles by adjusting the concentration of tripolyphosphate, with the loading capacity being decreased as the tripolyphosphate concentration increased.  With suitable processing conditions, we were able to produce ADP nanoparticles encapsulated in chitosan with an average size range of 55–60 nm and relatively high loading contents of ADP ranging between 43 and 74 %.  The release profiles of ADP in phosphate buffer solution exhibited a rapid burst release within 4 hr followed by a lag phase (~5-24 hr) and a sustained release (during 1-10 day).  In addition, the stability of encapsulated ADP increased as compared with its non-encapsulated counterpart.