Physical and 3D Printing Properties of Arrowroot Starch Gels.

This paper aims to investigate the physical and 3D printing properties of arrowroot starch (AS), a natural biopolymer with many potential health benefits. Scanning electron microscopy images showed that AS granules had mixed spherical and elongated geometries, with average sizes of 10.5 ± 2.5 µm. The molecular weight of AS measured by gel permeation chromatography (GPC) was 3.24 × 107 g/mol, and the amylose/amylopectin ratio of AS was approximately 4:11. AS has an A-type crystal structure, with a gelatinization temperature of 71.8 ± 0.2 °C. The overlap concentration (C*) of AS in aqueous solutions was 0.42% (w/v). Temperature-dependent dynamic rheological analyses of 10% to 30% (w/v) AS fluids showed that the storage modulus (G') reached the maximum values around the gelatinization temperatures, while the yield stress (τy) and flow stress (τf) values all increased with the increase in AS concentration. The printing accuracy of AS gels was found to be associated with the interplay between the G' values and the restorability after extrusion, determined by the three-interval thixotropy tests (3ITT). The optimum 3D printing condition occurred at 20% (w/v) AS, the nozzle diameter of 0.60 mm, the printing speed of 100 mm/s and the extrusion speed of 100 mm/s. Our research provides a promising biopolymer to be used in the design of novel personalized functional foods.

Development of organogel-based emulsions to enhance the loading and bioaccessibility of 5-demethylnobiletin.

5-Demethylnobiletin (5-DMN), identified in the aged citrus peels, has received increasing attentions due to its outstanding bioactivity among citrus polymethoxyflavones (PMFs). However, the poor water solubility and high crystallinity limit its oral bioavailability. Besides, the solubility of 5-DMN in the oil is very limited, which restricts its loading capacity in emulsions for bioavailability enhancement. In this study, an organogel formulation was developed to improve the solubility of 5-DMN in medium-chain triacylglycerols by 3.5 times higher without crystal formation during 5-day storage at room temperature. Increasing the gelator (i.e., sugar ester) concentration led to the increase of viscosity and a gel-like structure of the organogel. The ternary phase diagram of organogel-based emulsions was explored, and 40% organogel was selected as the oil phase for emulsion preparation. Increasing the concentration of Tween 80 from 0% to 6% decreased the droplet size and viscoelasticity of the emulsions. Two in vitro models, the pH-stat lipolysis model and TNO gastro-intestinal model (TIM-1), were applied to investigate the bioaccessibility of 5-DMN in different delivery systems. Compared with the conventional emulsion and oil suspension, the pH-stat lipolysis demonstrated that the organogel-based emulsion was the most efficient tool to enhance 5-DMN bioacccessibility. Moreover, TIM-1 digestive study indicated that 5-DMN bioaccessibility delivered by organogel-based emulsions was about 3.26-fold higher than that of oil suspension. Our results suggested that the organogel-based emulsion was an effective delivery route to enhance the loading and bioaccessibility of lipophilic compounds of high crystallinity.

Anti-Melanogenic Mechanism of Tetrahydrocurcumin and Enhancing Its Topical Delivery Efficacy Using a Lecithin-Based Nanoemulsion.

Tetrahydrocurcumin (THC) has been well known for its superior antioxidant properties. Therefore, it is speculated that it might be effective to relieve oxidative stress-induced diseases, such as skin hyperpigmentation. In this work, an in vitro B16F10 melanoma cell model was used to study the impact of THC on the melanogenic process under stressed conditions. It was demonstrated that THC could effectively inhibit the α-MSH (melanocyte-stimulating hormone) induced melanin production in B16F10 melanoma cells and the expressions of three key enzymes involved with the biosynthetic process of melanin, tyrosinase (TYR), tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2), were all significantly reduced. In addition, an in vitro human keratinocyte cell model was used to investigate the potential protective role of THC on H2O2-induced cytotoxicity. It was found that THC could prevent H2O2-induced oxidative stress based on the results of both the cell viability study and the intracellular ROS (reactive oxygen species) study assessed by the flow cytometry. Last, THC was formulated into a lecithin based nanoemulsion, and an in vitro Franz diffusion cell study using Strat-M® membrane concluded that the nanoemulsion could significantly enhance the membrane permeation compared to the unformatted THC suspension. This research demonstrated the anti-melanogenic benefits of THC on the melanoma and keratinocyte cell models and the topical delivery efficacy could be significantly enhanced using a lecithin based nanoemulsion.

Evaluation of the bioaccessibility of tetrahydrocurcumin-hyaluronic acid conjugate using in vitro and ex vivo models.

Tetrahydrocurcumin-hyaluronic acid (THC-HA) conjugate was synthesized in order to improve the bioaccessibility of tetrahydrocurcumin (THC). The successful conjugation was confirmed by the results from 1H-nuclear magnetic resonance (1H NMR), Differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Bioaccessibility enhancement from the THC-HA conjugate compared to the free crystalline THC suspension was demonstrated by the results from ex vivo Franz diffusion cell using small intestine from porcine and in vitro TNO dynamic gastrointestinal model-1 (TIM-1). Additionally, in vitro release was studied, and the integrity of the conjugate in both simulated gastric and intestinal conditions was found to maintain for up to 4 h. Mucoadhesive assay and rheological results indicated that the mucoadhesive property of THC-HA, in combination with the aqueous solubility enhancement, might contribute to the increased bioaccessibility. This study provides a promising approach to enhance the bioaccessibility of tetrahydrocurcumin through the innovative conjugation with hyaluronic acid.