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Crystal network structure and stability of beeswax-based oleogels with different polyunsaturated fatty acid oils

Han W, Chai X, Liu Y, Xu Y, Tan CP

Food Chem, 2021 Dec 04;381:131745.
PMID: 35124493 DOI: 10.1016/j.foodchem.2021.131745

The effect of different types of oils including camellia oil (CLO), sunflower oil (SFO), corn oil (CO) and linseed oil (LO) on the formation, crystal network structure and mechanical properties of 4%wt beeswax (BW) in oleogel was investigated. BW oleogels containing oils with higher contents of polyunsaturated fatty acids gelled first (1%wt), especially LO with higher contents of linolenic acid rather than CLO with higher contents of monounsaturated fatty acids. In comparison, oils with higher polyunsaturated fatty acid contents exhibited higher Db with more extensive microstructure at different cooling rates, which was related to shorter nucleation induction time of crystal and higher crystallinity. Stronger van der Waals forces were observed in oleogels with higher polyunsaturated fatty acid contents especially for LO oleogel. Rheology also showed that LO oleogel with higher content of linolenic acid had higher crystallinity and lower crystal melting interfacial tension, resulting in the formation of a more stable network structure.
Fulltext Organotypic slice culture based on in ovo electroporation for chicken embryonic central nervous system

Yang C, Li X, Li S, Chai X, Guan L, Qiao L, et al.

J Cell Mol Med, 2019 03;23(3):1813-1826.
PMID: 30565384 DOI: 10.1111/jcmm.14080

Organotypic slice culture is a living cell research technique which blends features of both in vivo and in vitro techniques. While organotypic brain slice culture techniques have been well established in rodents, there are few reports on the study of organotypic slice culture, especially of the central nervous system (CNS), in chicken embryos. We established a combined in ovo electroporation and organotypic slice culture method to study exogenous genes functions in the CNS during chicken embryo development. We performed in ovo electroporation in the spinal cord or optic tectum prior to slice culture. When embryonic development reached a specific stage, green fluorescent protein (GFP)-positive embryos were selected and fluorescent expression sites were cut under stereo fluorescence microscopy. Selected tissues were embedded in 4% agar. Tissues were sectioned on a vibratory microtome and 300 μm thick sections were mounted on a membrane of millicell cell culture insert. The insert was placed in a 30-mm culture dish and 1 ml of slice culture media was added. We show that during serum-free medium culture, the slice loses its original structure and propensity to be strictly regulated, which are the characteristics of the CNS. However, after adding serum, the histological structure of cultured-tissue slices was able to be well maintained and neuronal axons were significantly longer than that those of serum-free medium cultured-tissue slices. As the structure of a complete single neuron can be observed from a slice culture, this is a suitable way of studying single neuronal dynamics. As such, we present an effective method to study axon formation and migration of single neurons in vitro.
Synergistic effect of hydrophilic polyglycerol fatty acid esters and protein on the stability of interfacial membrane in low-fat aerated emulsions with different homogenization conditions

Han W, Chai X, Zaaboul F, Sun Y, Tan CP, Liu Y

Food Chem, 2024 Mar 01;435:137584.
PMID: 37774617 DOI: 10.1016/j.foodchem.2023.137584

This study investigates the impact of various chain lengths of hydrophilic polyglycerol fatty acid esters (HPGEs), namely SWA-10D, M-7D and M-10D on protein interactions and their influence on the surface morphology and interfacial properties of low-fat aerated emulsions under different pressures conditions. M-7D and M-10D samples exhibited larger particle sizes, higher ζ-potential and rougher surface compared to SWA-10D sample at 1 % concentration of HPGEs. Consequently, M-7D and M-10D samples demonstrated lower values of G', G'', and higher values tan δ at the oil-water interface as pressure increased, thereby promoting the formation of less viscoelastic structures. M-7D sample, characterized by lower content of α-helix structures, resulted in an observable redshift in the NH and CO groups of the protein. Molecular docking analysis affirmed that M-7D sample exhibited a lower absolute binding energy value, indicating stronger interaction with the protein compared to other samples, ultimately contributing to the unstable interfacial membrane formed.
Effect of different chain lengths of monoglyceride on the O/W interfacial properties with high-melting and low-melting crystals in low-fat aerated emulsion

Han W, Chai X, Zaaboul F, Sun Y, Tan CP, Liu Y

Food Chem, 2023 Nov 30;427:136656.
PMID: 37393637 DOI: 10.1016/j.foodchem.2023.136656

The effect of different types of monoglycerides, including monopalmitin, capryl monoglyceride (GMB), and succinylated monoglyceride (GMSA) in combination with palm kernel stearin (PKS) and beeswax (BW), on the formation, crystal network structure, and partial coalescence properties of aerated emulsions (20 % w/w fat) was investigated. The stability of BW and PKS crystals with a 1 % concentration of GMSA and GMB, respectively, in the oil phase was lower than the other crystals. BW-GMSA and PKS-GMB crystals exhibited a lower crystallization rate, higher contact angles and no significant peak shift in the small-angle X-ray scattering results. The BW-GMSA and PKS-GMB emulsions had a lower nucleation rate in the bulk and a higher nucleation rate at the interface, resulting in a higher fraction of crystals adsorbed at the oil/water interface. This reduced the number of interfacial proteins and led to a high degree of partial coalescence and the formation of stable aerated networks.
Effects of N-succinyl-chitosan coating on properties of astaxanthin-loaded PEG-liposomes: Environmental stability, antioxidant/antibacterial activities, and in vitro release

Liu A, Chai X, Zhu S, Chin PT, He M, Xu YJ, et al.

Int J Biol Macromol, 2023 Jul 31;244:125311.
PMID: 37302627 DOI: 10.1016/j.ijbiomac.2023.125311

Astaxanthin (AST) has outstanding antioxidant and anti-inflammation bioactivities, but the low biocompatibility and stability limit its application in foods. In this study, N-succinyl-chitosan (NSC)-coated AST polyethylene glycol (PEG)-liposomes were constructed to enhance the biocompatibility, stability, and intestinal-targeted migration of AST. The AST NSC/PEG-liposomes were uniform in size, had larger particles, greater encapsulation efficiency, and better storage, pH, and temperature stability than the AST PEG-liposomes. AST NSC/PEG-liposomes exerted stronger antibacterial and antioxidant activities against Escherichia coli and Staphylococcus aureus than AST PEG-liposomes. The NSC coating not only protects AST PEG-liposomes from gastric acid but also prolongs the retention and sustained release of AST NSC/PEG-liposomes depending on the intestinal pH. Moreover, caco-2 cellular uptake studies showed that AST NSC/PEG-liposomes had higher cellular uptake efficiency than AST PEG-liposomes. And AST NSC/PEG-liposomes were taken up by caco-2 cells through clathrin mediated endocytic, macrophage pathways and paracellular transport pathway. These results further proved that AST NSC/PEG-liposomes delayed the release and promoted the intestinal absorption of AST. Hence, AST PEG-liposomes coated with NSC could potentially be used as an efficient delivery system for therapeutic AST.
Electrospun microcrystalline cellulose/chitosan porous composite nanofibrous membranes modified by non-thermal plasma for gaseous formaldehyde adsorption

Xiong J, Luo R, Jia Z, Ge S, Lam SS, Xie L, et al.

Int J Biol Macromol, 2024 Jan;256(Pt 2):128399.
PMID: 38007014 DOI: 10.1016/j.ijbiomac.2023.128399

To develop a green and facile adsorbent for removing indoor polluted formaldehyde (HCHO) gas, the biomass porous nanofibrous membranes (BPNMs) derived from microcrystalline cellulose/chitosan were fabricated by electrospinning. The enhanced chemical adsorption sites with diverse oxygen (O) and nitrogen (N)-containing functional groups were introduced on the surface of BPNMs by non-thermal plasma modification under carbon dioxide (CO2) and nitrogen (N2) atmospheres. The average nanofiber diameters of nanofibrous membranes and their nanomechanical elastic modulus and hardness values decreased from 341 nm to 175-317 nm and from 2.00 GPa and 0.25 GPa to 1.70 GPa and 0.21 GPa, respectively, after plasma activation. The plasma-activated nanofibers showed superior hydrophilicity (WCA = 0°) and higher crystallinity than that of the control. The optimal HCHO adsorption capacity (134.16 mg g-1) of BPNMs was achieved under a N2 atmosphere at a plasma power of 30 W and for 3 min, which was 62.42 % higher compared with the control. Pyrrolic N, pyridinic N, CO and O-C=O were the most significant O and N-containing functional groups for the improved chemical adsorption of the BPNMs. The adsorption mechanism involved a synergistic combination of physical and chemical adsorption. This study provides a novel strategy that combines clean plasma activation with electrospinning to efficiently remove gaseous HCHO.
Fulltext Association of Glaucoma Risk Genes with Retinal Nerve Fiber Layer in a Multi-ethnic Asian Population: The Singapore Epidemiology of Eye Diseases Study

Chai X, Low KY, Tham YC, Chee ML, Thakur S, Zhang L, et al.

Invest Ophthalmol Vis Sci, 2020 08 03;61(10):37.
PMID: 32821913 DOI: 10.1167/iovs.61.10.37

Purpose: Genome-wide association studies have identified several genes associated with glaucoma. However, their roles in the pathogenesis of glaucoma remain unclear, particularly their effects on retinal nerve fiber layer (RNFL) thickness. The aim of this study was to investigate the associations between the identified glaucoma risk genes and RNFL thickness.
Methods: A total of 3843 participants (7,020 healthy eyes) were enrolled from the Singapore Epidemiology of Eye Diseases (SEED) study, a population-based study composing of three major ethnic groups-Malay, Indian, and Chinese-in Singapore. Ocular examinations were performed, and spectral-domain optical coherence tomography (SD-OCT) was used to measure circumpapillary RNFL thickness. We selected 35 independent glaucoma-associated genetic loci for analysis. An linear regression model was conducted to determine the association of these variants with circumpapillary RNFL, assuming an additive genetic model. We conducted association analysis in each of the three ethnic groups, followed by a meta-analysis of them.
Results: The mean age of the included participants was 59.4 ± 8.9 years, and the mean RFNL thickesss is 92.3 ± 11.2 µm. In the meta-analyses, of the 35 glacuoma loci, we found that only SIX6 was significantly associated with reduction in global RNFL thickness (rs33912345; β = -1.116 um per risk allele, P = 1.64E-05), and the effect size was larger in the inferior RNFL quadrant (β = -2.015 µm, P = 2.9E-6), and superior RNFL quadrant (β = -1.646 µm, P = 6.54E-5). The SIX6 association were consistently observed across all three ethnic groups. Other than RNFL, we also found several genetic varaints associated with vertical cuo-to-disc ratio (ATOH7, CDKN2B-AS1, and TGFBR3-CDC7), rim area (SIX6 and CDKN2B-AS1), and disc area (SIX6, ATOH7, and TGFBR3-CDC7). The association of SIX6 rs33912345 with NRFL thickness remained similar after further adjusting for disc area and 3 other disc parameter associated SNPs (ATOH7, CDKN2B-AS1, and TGFBR3-CDC7).
Conclusions: Of the 35 glaucoma identified risk loci, only SIX6 is significantly and independently associated with thinner RNFL. Our study further supports the involvement of SIX6 with RNFL thickness and pathogensis of glaucoma.
Blooms of diatom and dinoflagellate associated with nutrient imbalance driven by cycling of nitrogen and phosphorus in anaerobic sediments in Johor Strait (Malaysia)

Chai X, Li X, Hii KS, Zhang Q, Deng Q, Wan L, et al.

Mar Environ Res, 2021 Jul;169:105398.
PMID: 34171592 DOI: 10.1016/j.marenvres.2021.105398

Coastal eutrophication is one of the pivotal factors driving occurrence of harmful algal blooms (HABs), whose underlying mechanism remained unclear. To better understand the nutrient regime triggering HABs and their formation process, the phytoplankton composition and its response to varying nitrogen (N) and phosphorus (P), physio-chemical parameters in water and sediment in Johor Strait in March 2019 were analyzed. Surface and sub-surface HABs were observed with the main causative species of Skeletonema, Chaetoceros and Karlodinium. The ecophysiological responses of Skeletonema to the low ambient N/P ratio such as secreting alkaline phosphatase, regulating cell morphology (volume; surface area/volume ratio) might play an important role in dominating the community. Anaerobic sediment iron-bound P release and simultaneous N removal by denitrification and anammox, shaped the stoichiometry of N and P in water column. The decrease of N/P ratio might shift the phytoplankton community into the dominance of HABs causative diatoms and dinoflagellates.
Efficient Cr(VI) remediation by electrospun composite porous nanofibers incorporating biomass with metal oxides and metal-organic framework

Luo R, Li R, Zheng Z, Zhang L, Xie L, Wu C, et al.

Environ Pollut, 2024 Apr 23;351:124026.
PMID: 38663509 DOI: 10.1016/j.envpol.2024.124026

To develop a highly efficient adsorbent to remediate and remove hexavalent chromium ions (Cr(VI)) from polluted water, cellulose acetate (CA) and chitosan (CS), along with metal oxides (titanium dioxide (TiO2) and ferroferric oxide (Fe3O4)), and a zirconium-based metal-organic framework (UiO-66) were used to fabricate the composite porous nanofiber membranes through electrospinning. The adsorption performance, influencing factors, adsorption kinetics and isotherms of composite nanofiber membranes were comprehensively investigated. The multi-layer membrane with interpenetrating nanofibers and surface functional groups enhanced the natural physical adsorption and provided potential chemical sites. The thermal stability was improved by introducing TiO2 and UiO-66. CA/CS/UiO-66 exhibited the highest adsorption capacity (118.81 mg g-1) and removal rate (60.76%), which were twice higher than those of the control. The correlation coefficients (R2) of all the composite nanofibers regressed by the Langmuir model were significantly higher than those by the Freundlich model. The pseudo-first-order kinetic curve of CA/CS composite nanofibers showed the highest R2 (0.973), demonstrating that the whole adsorption process involved a combination of strong physical adsorption and weak chemical adsorption by the amino groups of CS. However, the R2 values of the pseudo-second-order kinetic model increased after incorporating TiO2, Fe3O4, and UiO-66 into the CA/CS composite nanofiber membranes since an enhanced chemical reaction with Cr (VI) occured during the adsorption.