Laser Scanning Microscopy Images Research Articles

Quality characteristics and gastrointestinal fate of low fat emulsified sausage formulated with konjac glucomannan/oat β-glucan composite hydrogel

The objective of present study was to evaluate the utilization of konjac glucomannan/oat β-glucan composite hydrogel as partial or complete fat replacer on the quality characteristics and gastrointestinal fate of emulsified sausages. The obtained results indicated that in comparison to control emulsified sausage sample, the incorporation of composite hydrogel at a 75 % fat replacement level could not only enhance emulsion stability, water holding capacity (WHC), and compact structure of formulated emulsified sausage, but also decrease their total fat content, cooking loss, hardness, and chewiness. The in vitro digestion results suggested the addition of konjac glucomannan/oat β-glucan composite hydrogel reduced the protein digestibility of emulsified sausage, while it did not change the molecular weight of digestive products. The confocal laser scanning microscopy(CLSM) image showed the addition of composite hydrogel changed the size of fat and protein aggregate of emulsified sausage during digestion. Based on these findings, the fabrication of composite hydrogel containing konjac glucomannan and oat β-glucan was a promising strategy as fat replacer. Furthermore, this study provided a theoretic basis for designing composite hydrogel based fat replacers.

Extraction of bioactive polysaccharide from Ulva prolifera biomass waste toward potential biomedical application

Ulva prolifera macroalgae blooming caused by water eutrophication seriously affects the marine ecological environment. Exploring an efficient approach to turning algae biomass waste into high-value-added products is significant. The present work aimed to demonstrate the feasibility of the bioactive polysaccharide extraction from Ulva prolifera and to evaluate its potential biomedical application. A short autoclave process was proposed and optimized using the response surface methodology to extract Ulva polysaccharides (UP) with high molar mass. Our results indicated that UP with high molar mass (9.17 × 105 g/mol) and competitive radical scavenging activity (up to 53.4 %) could be effectively extracted with the assistance of Na2CO3 (1.3 %, wt.) at a solid-liquid ratio of 1/10 in 26 min. The obtained UP mainly composes of galactose (9.4 %), glucose (73.1 %), xylose (9.6 %), and mannose (4.7 %). The biocompatibility of the UP and its potential application as a bioactive ingredient in 3D cell culture has been evaluated and confirmed by confocal laser scanning microscopy and fluorescence microscope imaging inspection. This work demonstrated the feasibility of extracting bioactive sulfated polysaccharides with potential applications in biomedicine from biomass waste. Meanwhile, this work also provided an alternative solution to deal with the environmental challenges incurred by algae blooming worldwide.

Bacterial biofilm reduction by 275 and 455 nm light pulses emitted from light emitting diodes

AbstractEradication of biofilms from the food contact surfaces is a challenging task, owing to their increased resistance to sanitizers and regular cleaning practices. The treatment with the light pulses emitted from the light emitting diode (LED) is an emerging surface decontamination technology, that can produce the antibiofilm effect by photodynamic inactivation. The objective of this study was to understand the antibiofilm efficacy of the 275 (Ultraviolet‐C [UV‐C]) and 455 nm (Blue) light pulses emitted from the LEDs against single and dual‐species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03‐09 on stainless steel (SS) coupons formed at different time. The biofilm formation by S. Typhimurium was improved when grown with A. australiensis in dual‐species culture. Both 275 and 455 nm light pulses showed significant antibiofilm activity against S. Typhimurium and A. australiensis in single and dual‐species biofilms. For instance, the 275 nm LED treatment of surfaces of SS coupons with 1.8 J/cm2 dose on each surface, produced reductions of 4.24 and 3.9 log (CFU/cm2) in single (cell attachment) and dual‐species biofilms of S. Typhimurium, and reductions of 4.45 and 4.99 log (CFU/cm2) in single and dual‐species biofilms of A. australiensis. However, the susceptibility of A. australiensis toward 455 nm LED treatments was influenced by the presence of S. Typhimurium in the dual‐species biofilm. The confocal laser scanning microscopy images revealed significant cell membrane damage in the dual‐species biofilms by the LED treatments with 275 and 455 nm light pulses. Overall, several factors like surface temperature increase, strains used, treatment dose, treatment time, and incubation period of biofilms influenced the inactivation efficacy of the 275 and 455 nm LED treatments against the biofilms formed on SS coupons. This study provides an insight into the inactivation efficacy of LED light pulses against bacterial biofilms on food grade SS surfaces.

Potential for carbide dispersive precipitation strengthening Ni-based alloy for high temperature

Increasing service temperature of wrought Ni-based superalloy by increasing alloying degree and fraction of γ′ phase has come to a bottleneck. In present work, an attempt is made to make maximum use of carbide to strengthen Ni-based alloy with a simpler chemical composition. Multiple morphology characterization methods and high temperature tensile test show that the newly designed Ni(bal.)-20Cr-0.80C–12Ta (wt%) alloy can be strengthened by TaC and Cr-rich M7C3 carbide and shows good ductility at 800 °C. Phase transformation characteristics detected by differential scanning calorimetry (DSC) and high-temperature confocal laser scanning microscopy (CLSM) images shows that there is a potential for dispersive precipitation of carbide in the alloy to get better mechanical property.

Monitoring biofilm growth and dispersal in real-time with impedance biosensors.

Microbial biofilm contamination is a widespread problem that requires precise and prompt detection techniques to effectively control its growth. Microfabricated electrochemical impedance spectroscopy (EIS) biosensors offer promise as a tool for early biofilm detection and monitoring of elimination. This study utilized a custom flow cell system with integrated sensors to make real-time impedance measurements of biofilm growth under flow conditions, which were correlated with confocal laser scanning microscopy (CLSM) imaging. Biofilm growth on EIS biosensors in basic aqueous growth media (tryptic soy broth; TSB) and an oil-water emulsion (metalworking fluid; MWF) attenuated in a sigmoidal decay pattern, which lead to an ∼22 to 25% decrease in impedance after 24 hours. Subsequent treatment of established biofilms increased impedance by ∼14% and ∼41% in TSB and MWF, respectively. In the presence of Furanone C-30, a quorum sensing inhibitor (QSI), impedance remained unchanged from the initial time point for 18 hours in TSB and 72 hours in MWF. Biofilm changes enumerated from CLSM imaging corroborated impedance measurements, with treatment significantly reducing biofilm. Overall, these results support the application of microfabricated EIS biosensors for evaluating the growth and dispersal of biofilm in situ and demonstrate potential for use in industrial settings.

Characterizing and Quenching Autofluorescence in Fixed Mouse Adrenal Cortex Tissue.

Tissue autofluorescence of fixed tissue sections is a major concern of fluorescence microscopy. The adrenal cortex emits intense intrinsic fluorescence that interferes with signals from fluorescent labels, resulting in poor-quality images and complicating data analysis. We used confocal scanning laser microscopy imaging and lambda scanning to characterize the mouse adrenal cortex autofluorescence. We evaluated the efficacy of tissue treatment methods in reducing the intensity of the observed autofluorescence, such as trypan blue, copper sulfate, ammonia/ethanol, Sudan Black B, TrueVIEWTM Autofluorescence Quenching Kit, MaxBlockTM Autofluorescence Reducing Reagent Kit, and TrueBlackTM Lipofuscin Autofluorescence Quencher. Quantitative analysis demonstrated autofluorescence reduction by 12-95%, depending on the tissue treatment method and excitation wavelength. TrueBlackTM Lipofuscin Autofluorescence Quencher and MaxBlockTM Autofluorescence Reducing Reagent Kit were the most effective treatments, reducing the autofluorescence intensity by 89-93% and 90-95%, respectively. The treatment with TrueBlackTM Lipofuscin Autofluorescence Quencher preserved the specific fluorescence signals and tissue integrity, allowing reliable detection of fluorescent labels in the adrenal cortex tissue. This study demonstrates a feasible, easy-to-perform, and cost-effective method to quench tissue autofluorescence and improve the signal-to-noise ratio in adrenal tissue sections for fluorescence microscopy.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated–ultrasonicated OVA (SU-OVA) had decreased by 3.0–5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of − 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Emulsions stabilised by casein and hyaluronic acid: Effects of high intensity ultrasound on the stability and vitamin E digestive characteristics

This study aimed to prepare an emulsion stabilised by an ultrasound-treated casein (CAS)-hyaluronic acid (HA) complex and to protect vitamin E during in vitro digestion. It was found that high-intensity ultrasound (HIU) treatment significantly changed the hydrogen bonding, electrostatic interaction and hydrophobic interaction between CAS and HA, reduced the particle size of the CAS-HA complex, increased the intermolecular electrostatic repulsion, and thus significantly improved the emulsifying properties of the CAS-HA complex. Meanwhile, the creaming index (CI) and confocal laser scanning microscopy images showed that the stability of the CAS-HA-stabilised emulsion was the best when treated at 150 W for 10 min, which could be attributed to the enhanced adsorption capacity of the CAS-HA complex at the oil–water interface and the viscosity of the formed emulsion. In vitro digestion experiments revealed that the emulsion stabilised by the ultrasound-treated CAS-HA complex had a good protective effect on vitamin E. This study is significant for the development of emulsions for the delivery of lipophilic nutrients.

Interactions between sorghum starch and mushroom polysaccharides and their effects on starch gelatinization and digestion

This study aimed at gaining insight into the mechanism of interactions between sorghum starch and mushroom polysaccharides (MPs) obtained from three cultivars Lentinula edodes (LEP), Auricularia auricula (AAP), and Tremella fuciformis polysaccharides (TFP) in relation to gelatinization, retrogradation and digestibility of starch, and microstructures before and after digestion. MPs decreased the degree of gelatinization, activation energy (retrogradation energy), and digestibility of sorghum starch, whilst they increased the particle size of digesta in a concentration dependent manner (0.15–0.6%, w/v). Confocal laser scanning microscopic (CLSM) images of starch suspensions, gels, and digesta illustrated that LEP was able to coat the sorghum starch granules through electrostatic interaction, which promoted starch retrogradation in gels after long-term storage. AAP and TFP were found to possess ability to suppress starch crystallization in sorghum starch gels, achieved through hydrophobic interaction with starch. TFP (glucuronoxylomannan) and most AAP particles were unable to coat sorghum starch granules, although a small number of AAP particles complexed with the starch through hydrogen bonding. The interaction between sorghum starch and MPs depended on the nature of MPs and their concentration. These findings would provide fundamentals for the utilization of MPs as glycaemic controller of starch and starch-rich foods.

Steam explosion pretreatment enhancing enzymatic digestibility of overground tubers of tiger nut (Cyperus esculentus L.).

Tiger nut (TN) is recognized as a high potential plant which can grow in well-drained sandy or loamy soils and provide food nutrients. However, the overground tubers of TN remain unutilized currently, which limits the value-added utilization and large-area cultivation of this plant. In the present study, the overground tubers of TN were subjected to enzymatic hydrolysis to produce fermentable sugars for biofuels production. Steam explosion (SE) was applied to modify the physical-chemical properties of the overground tubers of TN for enhancing its saccharification. Results showed that SE broke the linkages of hemicellulose and lignin in the TN substrates and increased cellulose content through removal of hemicellulose. Meanwhile, SE cleaved inner linkages within cellulose molecules, reducing the degree of polymerization by 32.13-77.84%. Cellulose accessibility was significantly improved after SE, which was revealed visibly by the confocal laser scanning microscopy imaging techniques. As a result, enzymatic digestibility of the overground tubers of TN was dramatically enhanced. The cellulose conversion of the SE treated TN substrates reached 38.18-63.97%, which was 2.5-4.2 times higher than that without a SE treatment. Therefore, SE pretreatment promoted saccharification of the overground tubers of TN, which paves the way for value-added valorization of the TN plants.

Oil Bodies from Chia (Salvia hispanica L.) and Camelina (Camelina sativa L.) Seeds for Innovative Food Applications: Microstructure, Composition and Physical Stability

Exploring and deciphering the biodiversity of oil bodies (OBs) recovered from oilseeds are of growing interest in the preparation of sustainable, natural and healthy plant-based food products. This study focused on chia (Salvia hispanica L.) and camelina (Camelina sativa L.) seed OBs. A green refinery process including ultrasound to remove mucilage, aqueous extraction by grinding and centrifugation to recover OBs from the seeds was used. The microstructure, composition and physical stability of the OBs were examined. Confocal laser scanning microscopy images showed that chia and camelina seed OBs are spherical assemblies coated by a layer of phospholipids and proteins, which have been identified by gel electrophoresis. The mean diameters determined by laser light scattering measurements were 2.3 and 1.6 µm for chia and camelina seed OBs, respectively. The chia and camelina seed OBs were rich in lipids and other bioactive components with, respectively, 64% and 30% α-linolenic acid representing 70% and 53% of the total fatty acids in the sn-2 position of the triacylglycerols, 0.23% and 0.26% phospholipids, 3069 and 2674 mg/kg oil of β-sitosterol, and lipophilic antioxidants: 400 and 670 mg/kg oil of γ-tocopherol. Phenolic compounds were recovered from the aqueous extracts, such as rutin from camelina and caffeic acid from chia. Zeta-potential measurements showed changes from about -40 mV (pH 9) to values that were positive below the isoelectric points of pH 5.1 and 3.6 for chia and camelina seed OBs, respectively. Below pH 6.5, physical instability of the natural oil-in-water emulsions with aggregation and phase separation was found. This study will contribute to the development of innovative and sustainable food products based on natural oil-in-water emulsions containing chia and camelina seed OBs for their nutritional and health benefits.

Automated Cell Viability Analysis in Tissue Scaffolds

Image processing techniques are frequently used for extracting quantitative information (cell area, cell size, cell counting, etc.) from different types of microscopic images. Image analysis of cell biology and tissue engineering is time consuming and requires personal expertise. In addition, evaluation of the results may be subjective. Therefore, computer-based learning applications have been rapidly developed in recent years. In this study, Confocal Laser Scanning Microscope (CLSM) images of the viable pre-osteoblastic mouse MC3T3-E1 cells in 3D bioprinted tissue scaffolds, captured from a bone tissue regeneration study, were analyzed by using image processing techniques. The goal of this study is to develop a reliable and fast algorithm for semi-automatic analysis of CLSM images. Percentages of live and dead cell areas in the scaffolds were determined with image correlation, and then, total cell viabilities were calculated. The other goal of this study is to determine the depth profile of viable cells in 3D tissue scaffold. Manual measurements of four different analysts were obtained. The measurement variations of analysts, also known as the coefficient of variation, were determined from 13.18% to 98.34% for live cell images and from 9.75% to 126.02% for dead cell images. To overcome this subjectivity, a semi-automatic algorithm was developed. Consequently, cross-sectional image sets of three different types of tissue scaffolds were analyzed. As a result, maximum cell viabilities were obtained at intervals of 63 µm and 90 µm from the scaffold surface.

Influence of access cavity design on calcium hydroxide removal using different cleaning protocols: a confocal laser scanning microscopy study.

The purpose of this study was to evaluate the influence of endodontic access cavities design on the removal of calcium hydroxide medication of the apical third of mandibular incisor root canal walls and dentinal tubules with different cleaning protocols: EDDY sonic activation, Er,Cr:YSGG laser-activated irrigation, or conventional irrigation with IrriFlex. Seventy-eight extracted human mandibular incisors were assigned to 6 experimental groups (n = 13) according to the endodontic access cavity and cleaning protocol for calcium hydroxide removal: traditional access cavity (TradAC)/EDDY; ultraconservative access cavity performed in the incisal edge (UltraAC.Inc)/EDDY; TradAC/Er,Cr:YSGG; UltraAC.Inc/Er,Cr:YSGG; TradAC/IrriFlex; or UltraAC.Inc/IrriFlex. Confocal laser scanning microscopy images were used to measure the non-penetration percentage, maximum residual calcium hydroxide penetration depth, and penetration area at 2 and 4 mm from the apex. Data were statistically analyzed using Shapiro-Wilk and WRS2 package for 2-way comparison of non-normally distributed parameters (depth of penetration, area of penetration, and percentage of non-penetration) according to cavity and cleaning protocol with the significance level set at 5%. The effect of cavity and cleaning protocol interactions on penetration depth, penetration area and non-penetration percentage was not found statistically significant at 2 and 4 mm levels (p > 0.05). The present study demonstrated that TradAC or UltraAC.Inc preparations with different cleaning protocols in extracted mandibular incisors did not influence the remaining calcium hydroxide at 2 and 4 mm from the apex.

Improvement of structural, physicochemical, and rheological properties of porcine myofibrillar proteins by high-intensity ultrasound treatment for application as Pickering stabilizers.

This study aimed to evaluate the potential of time-dependent (0, 15, 30, 60, 120min) treatment of porcine-derived myofibrillar proteins (MPs) with high-intensity ultrasound (HIU) for utilizing them as a Pickering stabilizer and decipher the underlying mechanism by which HIU treatment increases the emulsification and dispersion stability of MPs. To accomplish this, we analyzed the structural, physicochemical, and rheological properties of the HIU-treated MPs. Myosin heavy chain and actin were observed to be denatured, and the particle size of MPs decreased from 3,342.7nm for the control group to 153.9nm for 120min HIU-treated MPs. Fourier-transformed infrared spectroscopy and circular dichroism spectroscopy confirmed that as the HIU treatment time increased, α-helical content increased, and β-sheet decreased, indicating that the protein secondary/tertiary structure was modified. In addition, the turbidity, apparent viscosity, and viscoelastic properties of the HIU-treated MP solution were decreased compared to the control, while the surface hydrophobicity was significantly increased. Analyses of the emulsification properties of the Pickering emulsions prepared using time-dependent HIU-treated MPs revealed that the emulsion activity index and emulsion stability index of HIU-treated MP were improved. Confocal laser scanning microscopy images indicated that small spherical droplets adsorbed with MPs were formed by HIU treatment and that dispersion stabilities were improved because the Turbiscan stability index of the HIU-treated group was lower than that of the control group. These findings could be used as supporting data for the utilizing porcine-derived MPs, which have been treated with HIU for appropriate time periods, as Pickering stabilizers.

Fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy for deciphering the morphological evolution of supramolecular self-assembly.

The properties and functions of non-covalent interaction-driven fluorescent supramolecular self-assembly depend greatly on their evolution dynamics. Electron microscopy, atomic force microscopy, and confocal laser scanning microscopy have been used to elucidate the formation of molecular self-assembly. However, some pertinent issues, such as the drying or freezing of the sample for electron microscopy, the influence of the interactions between the tip and the sample in atomic force microscopy imaging, and the low spatial resolution of confocal laser scanning microscopy images, often impede the real-time analysis and exploration of the dynamics of molecular self-assembly processes. In this context, fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy have recently been explored to unravel the physical picture of the in situ growth dynamics and stimuli-induced morphological transformation of luminescent self-assembled structures. The current highlight article demonstrates the need for fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy to acquire precise information on the dynamics and morphological evolution of fluorescent self-assembled architectures using a few remarkable recent studies. In addition to the current status and challenges, the future directions for the further exploration of dynamic self-assembly processes towards developing next-generation functional materials have been delineated.

Effect of W/O pre-emulsion prepared with different emulsifiers on the physicochemical properties of soy protein isolate-based emulsion films

The effects of incorporating a water-in-oil pre-emulsion based on different emulsifiers with similar hydrophilic-lipophilic balances on the physicochemical properties of soy protein isolate-based emulsion films were investigated. Confocal laser scanning microscopy images indicated that the oil droplet size in the polyglycerol polyricinoleate and lecithin pre-emulsions was larger than that in the glycerol monostearate, span, and sucrose ester pre-emulsions. By contrast, the oil droplet size in the film-forming emulsions had opposite orders. After drying, the polyglycerol polyricinoleate and lecithin emulsion films contained small and evenly distributed oil droplets and demonstrated a small difference of upper and lower surfaces in oil concentration and contact angle. The water vapor permeability of emulsion films prepared by polyglycerol polyricinoleate and lecithin pre-emulsion was 2.35 × 10−10 g m−1 s−1 Pa−1 and 2.32 × 10−10 g m−1 s−1 Pa−1, respectively, lower than that of other emulsion films. The control emulsion films had the highest tensile strength of 7.43 MPa, whereas polyglycerol polyricinoleate emulsion films had the lowest tensile strength of 4.87 MPa. Furthermore, the polyglycerol polyricinoleate emulsion films had the lowest glass transition temperature among the prepared emulsion films. This study concluded that the properties of film-forming emulsions could be affected by pre-emulsions based on different emulsifiers, resulting in different physicochemical properties of the emulsion films.

Comparison of physicochemical properties and volatile flavor compounds of plant-based yoghurt and dairy yoghurt

The aim of this study was to investigate and compare the physicochemical characteristics and volatile flavor compounds of three kinds of yoghurt made from reconstituted milk, soy drink and oat drink. The results showed that with the same fermentation ending pH of 4.5, reconstituted yoghurt had the highest titratable acidity mainly due to the highest buffering capacity and microbial counts (LAB). The textural and water holding capacity (WHC) parameters revealed that soy-based yoghurt had the highest firmness, consistency and WHC, indicating more rigid gel was formed. Meanwhile, rheological analysis showed soy-based yoghurt owned higher G′ and G'' values and higher stability against external stress, demonstrating that more and stronger interactions between soy proteins were built during fermentation. The confocal laser scanning microscopy (CLSM) image witnessed that soy-based yoghurt had the densest and finest network, while oat-based yoghurt had much coarser and looser structure, which was consistent with the lowest firmness and G′ value for oat-based yoghurt. In terms of color, reconstituted yoghurt was the lightest and oat-based yoghurt showed more reddish and yellowish. The main volatile flavor compounds in all yoghurts were ketones, while aldehydes contributed more in soy and oat yoghurt. PCA plot showed that volatile flavor compounds of reconstituted yoghurt and oat-based yoghurt were relatively similar, while soy-based yoghurt was much more different with high OAVs of hexanal, 1-octen-3-one, 1-octen-3-ol and 2-octenal. This study supplied a theoretical basis and an improvement direction for the better development of healthier plant-based yoghurt similar to dairy yoghurt.

Effect of the ratio of phenolic compounds to saccharides in soluble polysaccharides on ethanol fermentation

In this study, soluble polysaccharides (SPs) were used to prepare the complexes with different degrees of polymerization and ratios of saccharide to phenolic acids (PAs) and their effects on yeast growth and ethanol fermentation were studied. Time-of-flight mass spectrometry showed that the lower the degree of saccharide polymerization, the higher the PA content. Oligosaccharide-PAs played an important role in ethanol fermentation. ATP/ADP and flow cytometry indicated that oligosaccharide-PAs could improve cell viability and increase the proportion of living and dead cells. Atomic force microscopy and confocal laser scanning microscopy images showed that the oligosaccharide-PAs induced the formation of extracellular matrixes, maintained the cellular biomorphology. The oligosaccharide-PAs also regulated NAD+/NADH, NAPD+/NADPH, and reduced the intracellular peroxide content. Thus, the oligosaccharide-PAs improved the cell viability by reducing the intracellular peroxide content and maintaining the cellular biomorphology.

Unexpected Photocatalytic Degeneration of NAD + for Inducing Apoptosis of Hypoxia Cancer Cells

Unexpected Photocatalytic Degeneration of NAD ⁺ for Inducing Apoptosis of Hypoxia Cancer Cells

Fabrication and characterization of a bilayered system enabling sustained release of bioflavonoids derived from mandarin biomass

Food-grade hydrogels, those prepared with Generally Recognized as Safe (GRAS) polymers, are promising delivery systems. In this work, alginate hydrogels were studied for their ability to uphold flavonoids laden poly-lactic-co-glycolic acid (PLGA) nanoparticles, and their subsequent release pattern was observed through in vitro gastrointestinal environments. Flavonoids were derived from mandarin peels, and consisted of polymethoxyflavones, chiefly tangeretin and nobiletin, and flavanones, chiefly naringenin. Incorporating these into nanoparticles prepared from GRAS classified PLGA, hereinafter referred to as flavonoids-PLGA nanoparticles, offered the first layer of protection, which were then embedded into alginate hydrogels, offering the second layer of protection. This bilayered system was developed to ensure guarded passage of the bioactives through the severe gastric environment, which would otherwise lead to presystemic metabolism of the flavonoids, rendering them ineffective. The gels were characterised and a 6.0% alginate hydrogel was considered optimal as it offered a dense network, as confirmed by a field emission scanning electron microscope (FE-SEM) image, and a low porosity, which ensured retention of the nanoparticles. Gel rheology revealed the shear thinning behavior of hydrogels, and high resistance to deformation was observed for 6% hydrogel when subjected to a load of 500N. Subjecting the ensemble to gastrointestinal environments showed a negligible 4.0% release of flavonoids in the first 2 hours of the gastric phase, followed by a sustained release through the next 10 hours in the intestinal environment, as confirmed by mass spectrometry (MS) profiles. Confocal laser scanning microscope (CLSM) images of the hydrogel clearly revealed the pH-responsive swelling and release of the nanoparticles from the hydrogel in the intestinal phase. It is envisaged that these, and other similar findings, would eventually manifest into ‘functional hydrogels’ delivery systems that bear the ability to incorporate nutraceuticals whilst retaining their functionality, as viable products in the near future.