A simplex centroid mixture design was used to study the interactions between two chosen solvents, dichloromethane (DCM) and acetone (ACT), as organic-phase components in the formation and physicochemical characterization and cellular uptake of astaxanthin nanodispersions produced using precipitation and condensation processes. Full cubic or quadratic regression models with acceptable determination coefficients were obtained for all of the studied responses. Multiple-response optimization predicted that the organic phase with 38% (w/w) DCM and 62% (w/w) ACT yielded astaxanthin nanodispersions with the minimum particle size (106 nm), polydispersity index (0.191), and total astaxanthin loss (12.7%, w/w) and the maximum cellular uptake (2981 fmol/cell). Astaxanthin cellular uptake from the produced nanodispersions also showed a good correlation with their particle size distributions and astaxanthin trans/cis isomerization ratios. The absence of significant (p > 0.05) differences between the experimental and predicted values of the response variables confirmed the adequacy of the fitted models.

Abstract:The incorporation of lipophilic nutrients, such as astaxanthin (a fat soluble carotenoid) in nanodispersion systems can either increase the water solubility, stability and bioavailability or widen their applications in aqueous food and pharmaceutical formulations. In this research, gelatin and its combinations with sucrose oleate as a small molecular emulsifier, sodium caseinate (SC) as a protein and gum Arabic as a polysaccharide were used as stabilizer systems in the formation of astaxanthin nanodispersions via an emulsification-evaporation process. The results indicated that the addition of SC to gelatin in the stabilizer system could increase the chemical stability of astaxanthin nanodispersions significantly, while using a mixture of gelatin and sucrose oleate as a stabilizer led to production of nanodispersions with the smallest particle size (121.4 ± 8.6 nm). It was also shown that a combination of gelatin and gum Arabic could produce optimal astaxanthin nanodispersions in terms of physical stability (minimum polydispersity index (PDI) and maximum zeta-potential). This study demonstrated that the mixture of surface active compounds showed higher emulsifying and stabilizing functionality compared to using them individually in the preparation of astaxanthin nanodispersions.

In this work, astaxanthin nanodispersions were prepared using selected three component stabilizer system through a solvent-diffusion technique, with the particle size of 98.3 nm. The stability of produced nanodispersions against pH, salts, and heating were then evaluated. The produced nanodispersions exhibited good physical stability under wide ranges of pH (except around isoelectric point), sodium ion concentrations, and relatively high-temperature treatments (up to 60°C). However, formation of large particles was observed in either presence of calcium ions or higher thermal treatments (more than 60°C).

Chitosan is a well-known biodegradable biopolymer, which possesses antimicrobial properties. In this study, the effect of chitosan incorporation on the morphology; thermal, mechanical, and rheological properties; and antibacterial and photodegradation behaviors of polyethylene (PE)/thermoplastic starch (TPS) blends were examined. PE/TPS blends were compatibilized with low-density PE-grafted maleic anhydride copolymer (PE- g-MA) compatibilizer. Scanning electron microscopy (SEM) and tensile test indicated that the addition of chitosan in powder form has a devastating effect on both mechanical and morphological properties of the blends. Therefore, chitosan was plasticized with acetic acid and glycerol (2 wt% chitosan dissolved in acetic acid/glycerol solution) prior to addition to the blends, which considerably improved the mechanical properties of the blends. Dynamic rheological experiments revealed a decrease in the complex viscosity of the blends with the addition of plasticized chitosan compared with unplasticized chitosan. SEM micrographs demonstrated more homogenous microstructure for the blends containing plasticized chitosan and PE- g-MA compatibilizer. Differential scanning calorimetry results indicated that unplasticized chitosan acts as a nucleation agent for PE crystallization. Antibacterial analysis indicated that the incorporation of chitosan had a significant effect on preventing from bacterial population growth. The major part of this article was to study the effect of ultraviolet (UV) exposure on the chemical structure and mechanical properties of the blends, using Fourier transform infrared spectroscopy and tensile properties examination. The results indicated that the slight amount of chitosan may significantly improve the photostability of PE/TPS blends against UV degradation. However, PE- g-MA compatibilizer dramatically decreased the UV resistance of the blends.

Chitosan is an attractive natural biopolymer from renewable resources with the presence of reactive amino and hydroxyl functional groups in its structure. Due to the good biocompatibility of chitosan, it can be used in magnetic-field assisted drug delivery, enzyme or cell immobilization and many other industrial applications. In the past decade, nanotechnology has been a considerable research interest in the area of preparation of immobilized enzyme carriers. This study looks at characteristics and applications of chitosan and chitosan nanoparticles and their potentials as suitable supports for enzyme immobilization. Results indicated that activity of immobilized enzymes and performance of enzyme immobilization onto chitosan nanoparticles are higher than chitosan macro and microparticles. As compared to other biopolymers nanoparticles, application of chitosan nanoparticles to immobilize enzymes strongly increases stability of immobilized enzymes and their easy separability from the reaction mixture at the end of the biochemical process.