Electrospinning of Sodium Alginate-Pectin Ultrafine Fibers

ABSTRACT:  In this study, we investigated the electrospinning process of sodium alginate-pectin fibers intended to be used as a carrier for stabilizing folic acid. Fiber-forming solutions containing 0.01% (w/w) folic acid were prepared by blending low- or medium-viscosity sodium alginate with pectin in a 70 : 30 ratio to form LSAP and MSAP solutions, respectively. Similar to other polysaccharide polymers reported previously, these solutions could not be electrospun. However, the incorporation of poly(ethylene oxide) (PEO) effectively enabled the electrospinning process. Electrospun fibers of different morphologies, ranging from fiber to fiber-bead, were obtained, depending on the blend ratio, concentration, and viscosity of the polymer-PEO solution used. Fibers electrospun from 3% MSAP/PEO (80%/20% w/w) had the smallest diameter (about 40 nm), whereas fibers containing higher PEO contents were larger in diameter. Bead-free fibers were formed when 4% LSAP/PEO (50/50) and 5% LSAP/PEO (80/20 to 50/50) were electrospun. The electrical conductivity and surface tension lowering effects of PEO on the polymer solution were likely the contributing factors for the observed electrospinning behaviors. By adjusting the formulation of the polymer solution, fibers of various morphologies may be obtained to suit different end-use applications. A study is currently ongoing to investigate the effectiveness of these fibers for stabilizing folic acid.     

Tannic acid cross-linked gelatin–gum arabic coacervate microspheres for sustained release of allyl isothiocyanate: Characterization and in vitro release study

Tannic acid cross-linked gelatin-gum arabic coacervate microspheres, capable of sustained release of allyl isothiocyanate (AITC) with high encapsulation efficiency, were developed for safe and efficient oral delivery of AITC. The microspheres were spherical in shape and clustered. Statistical screening and optimization studies revealed that a maximum AITC encapsulation efficiency could be obtained when the microspheres were prepared with 4.5% total biopolymer, 6.5% oil, and 5.9% AITC in oil phase. Release studies showed that the sustained release performance of the optimized microspheres was greatly enhanced by using more tannic acid without loss in the encapsulation efficiency. The microspheres optimized with 1.5% tannic acid, having an encapsulation efficiency of 83.75% and a mean cluster size of 116.80 ??m, released 46% of encapsulated AITC after 2 h in pepsin-containing simulated gastric fluid (pH 1.2), followed by releasing additional 48% in 6 h after being transferred to pancreatin-containing simulated intestinal fluid (pH 7.5).     

Effect of alginate concentrations on survival of microencapsulated Lactobacillus casei NCDC-298

This study reports the tolerance of Lactobacillus casei NCDC-298 encapsulated in different alginate concentrations (2%, 3% or 4%), to low pH (1.5), high bile salt concentration (1% or 2%) and heat processing (55, 60 or 65 °C for 20 min). The release of encapsulated cells in simulated aqueous solution of colonic pH was also assessed. The survival of encapsulated L. casei was better at low pH, high bile salt concentration and during heat treatment as compared to free cells. The survival increased proportionately with increasing alginate concentrations without affecting the release of entrapped cells in solution of colonic pH.     

海藻酸纤维吸附及释放锌离子的性能

为深入了解海藻酸纤维吸附及释放锌离子的性能,通过湿法纺丝方法制备纯海藻酸锌纤维,并通过盐酸处理海藻酸钙纤维制备海藻酸纤维。在不同时间、温度及锌离子浓度的条件下研究海藻酸纤维吸附锌离子的性能。结果显示,通过控制硫酸锌及海藻酸纤维的质量比可制备锌离子含量不同的海藻酸纤维。采用生理盐水及不同浓度的蛋白质水溶液处理海藻酸锌纤维,并测试接触液中锌离子的浓度发现,低温时比高温下的锌离子释放量大,溶液中的蛋白质可促进锌离子的释放。     

Optimisation of the microencapsulation conditions and physicochemical properties of enteric‐coated lactase microcapsules

Enteric double‐coated lactase microcapsules were developed, and the encapsulation conditions were optimised using response surface methodology. The optimum concentration of the enteric coating material was 4.85 g/100 mL, and the amount of core material was 1.85 mL. The particle size of the zein‐coated microcapsules was 2.868 μm, which was smaller than that of the other microcapsules. All microcapsules showed high zeta‐potential values between pH 6 and 8. The in vitro release rates of hydroxypropyl methyl cellulose phthalate (HPMCP)‐ and shellac‐coated microcapsules were superior to that of the zein‐coated microcapsules. Finally, the microcapsules were barely hydrolysed in simulated gastric fluid; however, almost all the microcapsules coated with HPMCP or shellac released their contents in simulated intestinal fluid within 2 h (93.23 and 97.27%, respectively).     

响应面法优化苹果多酚微胶囊工艺

为确定苹果多酚微胶囊的最佳工艺,提高苹果多酚对不利环境的抗性及缓释能力,利用响应面法采用海藻酸钠、壳聚糖和氯化钙为壁材,以包埋率为响应值进行苹果多酚微胶囊工艺优化,并将优化后的微胶囊在模拟人工胃液、肠液中进行耐受性分析。结果显示,海藻酸钠浓度、氯化钙浓度、pH、芯壁比对苹果多酚包埋率均有显著影响。海藻酸钠浓度0.020 g/mL,氯化钙浓度0.040 g/mL,pH7.0,芯壁比2:1时,苹果多酚微胶囊的包埋率达到85.13%。微胶囊产品能减少苹果多酚在胃肠道中受到的破坏,在模拟胃液和肠液环境中得到了很好的释放,肠液中的最大释放率为83.00%。实验结果显示,该方法简单可行,有效提高了苹果多酚微胶囊的包埋率及缓释能力。     

双歧杆菌混凝胶微囊制备及其胃肠释放特性研究

为克服双歧杆菌不耐酸、不耐氧的缺点,本试验建立制备双歧杆菌微胶囊的方法。以海藻酸钠和氯化钙形成海藻酸钙水凝胶,再与壳聚糖复合形成聚电解质膜,通过单因素及Box-Behnken响应面试验优化制备双歧杆菌混凝胶微囊工艺,使用扫描电镜观察胶囊结构,并采用模拟胃液及肠液的独立影响实验和模拟连续消化道实验考察胶囊中双歧杆菌的释放特性及存活率,探究其稳定性。结果表明:离心菌体与1.5%海藻酸钠均匀混合,注射到1.2%氯化钙溶液中,再与0.5%壳聚糖固定化35 min最佳。此条件下胶囊形状完整,扫描电镜图显示微胶囊结构致密、具有较好的包埋性,胃肠释放实验证明胶囊具有肠溶胃不溶和缓释的载体特性,胶囊中的双歧杆菌在肠液中的存活率平均值为72.3%,经模拟消化道处理后的存活率为49.8%。此结果为双歧杆菌微胶囊化提供参考。     

Survival of probiotic bacteria nanoencapsulated within biopolymers in a simulated gastrointestinal model

The objective of this work was to fabricate electrospun nanofiber mats (nano-scale in diameter) using a combination of corn starch (CS) and sodium alginate (SA) and encapsulate probiotic strains of lactobacilli (Lactobacillus acidophilus (LA5) and Lactobacillus rhamnosus 23,527 LGG) and bifidobacteria (Bifidobacterium bifidum and Bifidobacterium animalis) to improve their survival in simulated gastrointestinal fluids. The viability of the lactobacilli and bifidobacteria (determined using plate count method) after electrospinning was 94.1% and 89.4% of the initial population. Upon exposure to in vitro condition of gastric fluid (HCl and pepsin, at 37 °C), the population (starting level of 9 log CFU/mL) of nanoencapsulated lactobacilli and bifidobacteria decreased only by 1.58 and 1.03 log CFU at 120 min. Treated with in vitro prepared intestinal fluid (dipotassium hydrogen phosphate, sodium hydroxide, bovine bile salt, and trypsin) no cell was detected at 30 min and the number of coated lactobacilli and bifidobacteria decreased by 2.90 and 2.23 log CFU at 120 min in comparison to nonencapsulated control. After 180-min exposure to simulated gastrointestinal fluid, population of encapsulated lactobacilli and bifidobacteria decreased by 3.02 and 2.55 log CFU at 180 min. The viability of the probiotic bacteria in simulated gastrointestinal conditions was enhanced significantly (81–100% of the initial population) by nanoencapsulation within nanofiber mats of CS/SA.     

Enhanced alginate microspheres as means of oral delivery of bacteriophage for reducing Staphylococcus aureus intestinal carriage

Bacteriophage therapy could provide additional treatment for control of intestinal colonization of microbial pathogens. But, efficacy of its oral application may be reduced by sensitivity of certain phages to the low pH in the stomach. The aim of this study was to develop an improved encapsulation formulation with enhanced acid protection for oral delivery of Staphylococcus aureus phage K. Calcium carbonate microparticles were co-encapsulated with phage K into alginate microspheres and tested their efficacy for improved phage viability under in vitro acidic conditions. Free phage was completely destroyed when exposed to simulated gastric fluid (SGF) of pH 2.5. In contrast, alginate encapsulated phage K had a decrease of only 2.4 log units in viability when incubated for 1 h in SGF at pH 2.5. By adding calcium carbonate as an antacid excipient to the alginate microspheres, the survival of encapsulated phage K in SGF was significantly improved, with only a 0.17 log units reduction after 2 h exposure to SGF at pH 2.5. A number of protective agents including trehalose, sucrose, skim milk, and maltodextrin were also tested and were found to increase the viability of encapsulated phage K when subjected to drying. The protective effects varied with the type and concentration of each incorporated additives. The improved encapsulation formulation increased efficacy of phage K survival when exposed to the simulated gastric condition. Here we tested S. aureus phage K as a model but further improvement of the encapsulation formulation could provide a potential technology for reducing intestinal colonization of other pathogens.     

Whey protein improves survival and release characteristics of bacteriophage Felix O1 encapsulated in alginate microspheres

Bacterial contamination is a major cause of food poisoning in humans worldwide. Phage therapy is a potential alternative to antibiotics in food animal production. Gastric acidity has been shown to compromise the viability of phage in vitro, hence, may affect the effectiveness of the phage treatment. Microencapsulation of bacteriophage in alginate microspheres protected phage against gastric acids; however, the release rate of phage was too slow when applied in chicks. The current study investigated the in vitro protection and release characteristics of alginate–whey protein microspheres (AWM) containing phage Felix O1 prepared by an extrusion method. Free phage was completely inactivated within minutes in simulated gastric fluid (SGF) at pH 2.0 and pH 2.5, while phage encapsulated in AWM mostly retained their viability after 2.0 h incubation. Encapsulated phage was completely released from the AWM in simulated intestinal fluid (SIF) within 3 h. Moreover, addition of maltodextrin to the encapsulation formula improved phage stability during air drying and storage. Our results show that addition of whey to alginate microsphere improved phage protection against acidic conditions and accelerated the release rate in SIF. AWM could be more suitable for oral phage therapy in chickens.     

Iron‐encapsulated cold‐set whey protein isolate gel powder – Part 1: Optimisation of preparation conditions and in vitro evaluation

A central composite design with a quadratic model was used to investigate the effects of three independent variables involved in the synthesis of iron‐encapsulated cold‐set whey protein isolate gel (WPI) on encapsulation efficiency (EE) and L*, a*, b* colour characteristics. The optimal conditions for maximum EE with minimum colour alteration were determined as 6.8% WPI, 18.8 mM iron and pH 7. In an in vitro gastrointestinal assay, only about 28% of the encapsulated iron was released in the gastric condition (with pepsin at pH 1.2), compared to 95% in the intestinal condition (with pancreatin at pH 7.5).     

Application of chitosan–alginate microspheres for the sustained release of bacteriophage in simulated gastrointestinal conditions

This study was designed to evaluate the acid stability, release property and antimicrobial efficacy of Escherichia coli O157:H7 bacteriophages encapsulated in chitosan–alginate microspheres under the simulated gastrointestinal conditions. The bacteriophages belonging to Myoviridae family were stable at the pH above 4 in trypticase soy broth. The chitosan–alginate microspheres exhibited protective effect on the viability of bacteriophages in the simulated gastric conditions at pH 2.0 and pH 2.5, showing 4.8 and 5.6 log PFU mL^‐1, respectively, after 1 h of incubation at 37 °C. The release per cent of bacteriophages from microspheres gradually increased up to 65% in the simulated intestinal condition (pH 7.5) at 37 °C for 6 h. The lytic efficacy of chitosan‐ and alginate‐encapsulated bacteriophages against E. coli O157:H7 was significantly maintained in the simulated intestinal conditions to 10 h of incubation (1.3 log reduction). The results suggest that the chitosan–alginate microspheres can be used as a reliable delivery system for bacteriophages.     

Development of functional alginate fibers for medical applications

In this study, antibacterial alginate fibers were developed by using two approaches for fiber development. Firstly, replacing the sodium ions of sodium alginates with metal ions like zinc. Secondly, replacing the sodium ions of sodium alginate with biologically inactive ions like calcium and loading the fibers with ZnO nanorods. Fibers were characterized by liquid absorption and ion release measurements, by placing them separately in distilled water, solution A (0.8298% NaCl & 0.0368% CaCl2) and normal saline solution. Results showed that release of ions from fibers was affected by liquid absorption, physiology of solution and contact time with solution. More ions were released from fibers with higher absorption and longer contact time. Calcium alginate fibers containing zinc ions showed greater absorbency as well as the greater metal ions release. Fibers containing zinc ions, and ZnO nanorods were also tested for their mechanical properties and antibacterial properties against Staphylococcus aureus and Escherichia coli. Alginate fibers containing ZnO nanorods were stronger than alginate fibers containing zinc ions. However, calcium fibers containing zinc ions exhibited more antibacterial activity.     

海藻糖基麦芽五糖及其微球的体外消化和酵解

为研究包埋前后的海藻糖基麦芽五糖(N-G7)在模拟消化液及体外酵解过程中的变化,采用口腔、胃部及小肠的体外消化模型分析消化前后溶液中N-G7的质量和N-G7微球(ALGCa)中的糖组成变化,应用体外发酵技术评价N-G7微球的发酵行为,检测不同时间点的pH值、菌体浓度(OD₆₀₀)、产气量、短链脂肪酸(SCFA)浓度等指标的变化,并探究其对人体肠道微生物构成的影响。结果表明：N-G7在口腔消化2 min后在强酸性的胃部环境中几乎不被水解,在小肠中N-G7的水解率达到了82.70%。采用不同质量分数(1%、2%、3%)的海藻酸钙对其进行包埋,形成的微球保留80%以上的N-G7到达结肠。在体外酵解中,各实验组的pH随时间延长逐渐降低,OD600随时间延长逐渐增加。质量分数2%的ALG-Ca组产气量和碳源消耗率在0～6 h内达到最低,而后逐渐增加,证明包埋后的N-G7发酵体系属于缓慢发酵。与对照相比,质量分数2%的ALG-Ca组产生大量SCFA,肠道菌群组成发生变化,更有利于益生菌的生长。     

The effect of alginates on in vitro gastric digestion of particulated whey protein

The aim of the study was to investigate how microparticulated and nanoparticulated whey proteins mixed with alginate respond to simulated in vitro gastric digestion conditions at pH 3.0. Initially, particle size distributions and zeta potential were measured in all mixtures at pH 3.0. Particle size distributions as well as SDS‐PAGE were used to investigate the rate of protein degradation by pepsin during simulated in vitro gastric digestion. The complexation of nanoparticulated and microparticulated whey protein with alginates causes formation of insoluble and soluble complexes, which can resist pepsin degradation to a different degree. These results highlight the potential of developing new food products, which can enhance satiety.     

Co-encapsulation of probiotics with prebiotics on alginate matrix and its effect on viability in simulated gastric environment

Two potential probiotic strains namely Staphylococcus succinus (MAbB4) and Enterococcus fecium (FIdM3) selected from previous probiotic property studies were co-encapsulated with complementary prebiotics. Two different prebiotics selected by in vitro fermentation viz. sugarbeet and chicory were separately encapsulated with both the strains in 2 g/100 mL alginate and were tested for the efficiency in improving the viability compared to free cells under in vitro acidic conditions. Results indicated significant improvement (P < 0.05) in survival of co-encapsulated cells when exposed to acidic (pH 2.0–3.0) and bile (0.3, 0.6 and 0.8 g/100 mL) conditions. The encapsulated cells showed about 98.75–88.75% of survivability in simulated gastric environment. Viability was maintained throughout the storage period and ranges from 8.1 log cfu/mL (Colony Forming Unit) to 7.9 log cfu/mL for about a period of 30 days at 4 °C. Interestingly it is the first work to use oligosaccharides rich carbohydrate source as such in encapsulation and was found to have an improved survival rate of probiotic strains along with alginate.     

Changes in the phenolic contents and antioxidant activities of citrus peels from different cultivars after in vitro digestion

The aim of this study was to investigate the effects of in vitro digestion on the phenolic contents and antioxidant activities of citrus peels. Three different varieties of citrus peels (mandarin, ponkan and red tangerine) were treated with simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The results showed that the SGF or SIF treatments of the citrus peels did not significantly increase the total phenolic content (TPC) or total flavonoid content (TFC), except for that of the TFC of ponkan peel treated with SGF. However, simulated in vitro digestion did improve the antioxidant activities measured with FRAP and ABTS methods. The effect of SGF was more positive than those of SIF for the FRAP assay, but the opposite was true for ABTS. Notably, both simulated digestion techniques decreased the DPPH free radical scavenging abilities. Simulated digestion in vitro changed the antioxidant activities of the citrus peels.     

Chitosan-coated pectin beads: Characterization and in vitro release of mangiferin

Microspheres of low degree of esterification (DE) pectin with calcium and the same sphere coated with chitosan (PCaC) were prepared. The spheres have diameters in the range 650–680 μm. The layer of chitosan is about of 5–15 μm thick. To obtain firm and stable PCaC beads, chitosan was reacetylated. Two different degrees of acetylation, giving PCaC50 and PCaC80 were adopted. The beads were characterized by FTIR, SEM and swelling measurements. Mangiferin was loaded in PCaC reacetylated in two different ways: by addition in pectin solution (M_p) and by addition in CaCl₂ solution (M_c). The yield in producing the beads, the efficiency in encapsulation and the content of mangiferin in beads were determined. A swelling kinetics study was done in simulated gastric fluid (SGF, pH 1.2) and in simulated intestine fluid (SIF, pH 7.4). The release of mangiferin from the beads was performed in SGF followed by the release in SIF. Based on the yield and efficiency in encapsulation the best bead was found to be PCaC50-M_p. The highest release (7.8 mg of mangiferin/g of bead) was achieved by the PCaC50-M_c. For all beads more bioactive was released in SGF than in SIF.     

Dissolution tests as a tool for predicting bioaccessibility of nutrients during digestion

Bioaccessibility and bioavailability of active ingredients (like vitamins, antioxidants, etc.) into food systems is often compromised by factors like low permeability and/or solubility within the gut, lack of stability during food processing (temperature and oxygen) as well as in the gastrointestinal tract (pH, enzymes, presence of other nutrients). Moreover, little is known on the influence of food structure and breakdown in the gut on nutrient release. The possibility of predicting the release of nutrients from food matrices under simulated gastrointestinal conditions is of great relevance in order to define which food matrix is best for which nutrient, as well as for looking at the interaction of ingredients with the enzymes involved in the digestive process. This study explores the potential relevance of dissolution tests as a tool for predicting bioaccessibility of nutrients during in vitro digestion. Whey protein hydrogels containing green tea extract (GTE) were chosen for this study. Different simulated in vitro gastrointestinal conditions (GI) were applied throughout the dissolution experiments and the GTE was analysed by UV–vis absorption spectroscopy. It was possible to distinguish between two different release kinetics when experiments were performed in simulated gastric or intestinal media. In the gastric step, the kinetic of GTE release was lower than in an intestinal environment, suggesting that more GTE is released and available for absorption into the intestine than in the stomach. The present study shows that it is possible to use the dissolution tester as a screening method to mimic nutrient release from a food matrix in the gastrointestinal tract.     

Control of lipase digestibility of emulsified lipids by encapsulation within calcium alginate beads

Structured delivery systems, fabricated from natural lipids and polymers, are finding increasing use to improve the oral bioavailability of poorly water-soluble drugs and nutraceuticals, as well as to control the release of lipophilic bioactive molecules within the human gastrointestinal tract. This study focused on the development of filled hydrogel particles to control the digestion and release of encapsulated lipids. These filled hydrogel particles were fabricated by trapping sub-micron lipid droplets within calcium alginate beads. These particles remained intact when the pH was varied from 1 to 7, but exhibited some shrinkage at pH 1 and 2. The free fatty acids released from the filled hydrogel particles after addition of pancreatic lipase were monitored using a pH-stat in vitro digestion model. Encapsulation of lipid droplets within calcium alginate beads (d = 2.4 mm) reduced the free fatty acids released from around 100% to less than 12% after 120 min. The rate and extent of lipid digestion increased with decreasing bead size (from 3.4 to 0.8 mm), decreasing degree of cross-linking (i.e., lower calcium or alginate concentrations), and decreasing triglyceride molecular weight (i.e., tributyrin > MCT ≈ corn oil). These results have important implications for the design of delivery systems to protect and release lipophilic bioactive components within the human body, as well as to modulate satiety/satiation by controlling the rate of lipid digestibility.