Handbook of Vitamin C Research

Encapsulation Devices for Vitamin C 199encapsulated ascorbic acid than that made by ethyl cellulose using other methods. This showsthat carnauba wax keeps the ascorbic acid more stable. In the solvent evaporation methods, ahigher molecular weight of ethyl cellulose and the addition of plasticizer were also found tobe important for good encapsulation. In the spray drying method, loss of ascorbic acid wasfound to be minimum during microencapsulation. Uddin et al found that the loss of ascorbicacid during encapsulation by spray drying was 20% [96]. Starch and β-cyclodextrinencapsulated ascorbic acid delayed the degradation of ascorbic acid during storage at 38°Cand relative humidity 84.0%.Trindade and Grosso studied the stability of ascorbic acid microencapsulated in granulesof rice starch and in gum arabic. Microcapsules made from starch were larger than thosemade from gum Arabic [126]. Ninety percent of starch microcapsules had diameters ≤ 57 μmwith an average of 20.5 μm while 90% of gum arabic microcapsules had diameters < 27 μmwith an average of 8.0 μm.Using the simplistic method, spherical and uniform particles powder has been obtainedfrom the commercial granules of poly(DL-lactide-co-glycolide), where the mean particlessize are in the range from 110 to 170nm. The various concentrations of the vitamin C havebeen encapsulated within PLGA particles. The results of the determination of the particleyield for various PLGA/ascorbic acid ratios were similar for each of the samples and in allcases greater than 50% [1,113]. The loading efficiency was determined to be greater than90% in all ratios of PLGA/ascorbic acid particles [1, 113]. The degradation of the PLGAwithout and with ascorbic acid has been followed as well as morphological changes whichoccurred during the degradation [1,127]. The degradation have been tracked for eight weeksand it has been determined that PLGA completely degrades within this period fully releasingall encapsulated ascorbic acid (Figure 8.). In the first 24 days, the samples degrade slowerwhile latter the pace of the degradation increases. In the first 24 days of the degradation, forall samples, less than the 10% of the encapsulated ascorbic acid have been released [1, 113].At the beginning the particles maintain the initial shape, but after 24 days the particles startbeing agglomerated, creating the porous film, where the porosity increases until the completedegradation of the samples. By the end of the experiment the nanoparticles have fullydegraded and there were no more traces of them in the solution. PLGA degrades viabackbone hydrolysis (bulk erosion) and the degradation products are the monomers, lacticacid and glycolic acid. It could be expected that the faster degradation of the lower molarmass fraction, present in copolymer, increases the local acidity, thereby, accelerating thehydrolysis of higher molar mass species. In another words, when acid accumulation creates alocal pH drop, catalytic degradation of the polymer itself occurs. The different ionized formsof the ascorbic acid have different redox properties, so that the redox-chemistry of theascorbic acid is highly pH dependent [128-130]. Ascorbic acid decomposes into biologicallyinactive compounds by auto-oxidation only at alkaline pH [131]. In the solution with low pH,decomposition of the ascorbic acid can happen for example under the influence of theenzymes (enzymatic oxidation) [131].The biological behaviour of PLGA nanospheres without and with encapsulated ascorbicacid is discussed in terms of in vitro toxicity in human hepatoma cells and in vivobiodistribution in rat after intravenous injection [132]. Neither PLGA nanospheres norPLGA/ascorbic acid 85/15% nanoparticles significantly affected the viability of the HepG2