Double-layer microcapsules based on shellac for enhancing probiotic survival during freeze drying, storage, and simulated gastrointestinal digestion

Probiotics are susceptible to diverse conditions during processing, storage, and digestion. Here, shellac (SC), sodium alginate (SA), coconut oil (CO), soybean oil (SO), and trehalose (AL) were used to prepare microcapsules aiming to improve the survival of Lactiplantibacillus plantarum KLDS1.0318 during freeze-drying, storage process, and gastrointestinal digestion. The results showed that for SA/AL/SC/CO and SA/AL/SC/SO, the survival loss decreased by 51.2 % and 51.0 % after a freeze-drying process compared with microcapsules embedded by SA; the viable bacteria count loss decreased by 4.36 and 4.24 log CFU/mL compared with free cell (CON) during storage for 28 d under 33%RH at 25 °C, respectively; while for simulating digestion in vitro, the survival loss decreased by 3.05 and 2.70 log CFU/mL, 0.63 and 0.55 log CFU/mL after digestion at simulated gastric fluid for 120 min and small intestine fluid for 180 min, respectively (P < 0.05). After microcapsules were added to fermented dairy stored at 4 °C for 21 d, the viable bacteria count of SA/AL/SC/CO and SA/AL/SC/SO significantly increased by 2.10 and 1.70 log CFU/mL compared with CON, respectively (P < 0.05). In conclusion, the current study indicated that shellac-based probiotic microcapsules have superior potential to protect and deliver probiotics in food systems.

Advances in protein-based microcapsules and their applications: A review

Due to their excellent emulsification, biocompatibility, and biological activity, proteins are widely used as microcapsule wall materials for encapsulating drugs, natural bioactive substances, essential oils, probiotics, etc. In this review, we summarize the protein-based microcapsules, discussing the types of proteins utilized in microcapsule wall materials, the preparation process, and the main factors that influence their properties. Additionally, we conclude with examples of the vital role of protein-based microcapsules in advancing the food industry from primary processing to deep processing and their potential applications in the biomedical, chemical, and textile industries. However, the low stability and controllability of protein wall materials lead to degraded performance and quality of microcapsules. Protein complexes with polysaccharides or modifications to proteins are often used to improve the thermal instability, pH sensitivity, encapsulation efficiency and antioxidant capacity of microcapsules. In addition, factors such as wall material composition, wall material ratio, the ratio of core to wall material, pH, and preparation method all play critical roles in the preparation and performance of microcapsules. The application area and scope of protein-based microcapsules can be further expanded by optimizing the preparation process and studying the microcapsule release mechanism and control strategy.

Preparation and thermal responsiveness of microencapsulated fluorinated liquids for automatic fire extinguishing

Most early-stage fires originating in small confined spaces may not be effectively mitigated by automatic fire-extinguishing systems. Leveraging the unique controlled release capability and barrier properties of microcapsules presents a promising avenue for developing multifunctional and intelligent fire-extinguishing agents tailored for early-stage fire suppression. This paper introduces two types of microcapsules that integrate automatic detection and fire extinguishing functions, utilizing fluorinated liquids specifically perfluoro(2-methyl-3-pentanone) and 1,1,1,2,2,3,4,5,5,5 decafluoro-3-methoxy-4(trifluoromethyl)-pentane as core materials. The preparation process was optimized, and the thermal response of the microcapsules was evaluated by directly incorporating them into combustible materials. The results indicated a correlation between the preparation method, coating efficiency, and thermal stability of microcapsules with the core-wall materials. When the fluoride solution in the core material reaches the thermal response threshold temperature, the gas pressure generated during vaporization and phase change can break through the shell, enabling early active fire protection. Beyond a specific threshold of additive microcapsules in the material, the material exhibits self-extinguishing potential during combustion. In cases where the additive amount falls short of achieving self-extinguishing, the fire-resistant performance of materials can be enhanced through various measures. For instance, reducing the amount of fire-extinguishing agents, delaying the ignition time of fuel, and lowering the heat release rate during combustion are effective strategies. Moreover, the degree of improvement is related to the additional amount and the type of core-wall materials. The thermal-response mechanism of microcapsules constitutes a comprehensive mechanism with physical and chemical effects. The finding of this research offer a new technical approach for microencapsulating high-boiling-point gas extinguishing agents, facilitating intelligent and precise prevention of early fires resulting from combustible materials.

Facile encapsulation of cyanoacrylate-based bioadhesive by electrospray method and investigation of the process parameters

Polymer microcapsules containing cyanoacrylates have represented a promising option to develop self-healing biomaterials. This study aims to develop an electrospray method for the preparation of capsules using poly(methyl methacrylate) (PMMA) as the encapsulant and ethyl 2-cyanoacrylate (EC) as the encapsulate. It also aims to study the effect of the electrospray process parameters on the size and morphology of the capsules. The capsules were characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FE-SEM). Moreover, the effects of electrospray process parameters on the size were investigated by Taguchi experimental design. FTIR and TGA approved the presence of both PMMA and EC without further reaction. FE-SEM micrograph demonstrated that an appropriate choice of solvents, utilizing an appropriate PMMA:EC ratio and sufficient PMMA concentration are critical factors to produce capsules dominantly with an intact and spherical morphology. Utilizing various flow rates (0.3-0.5 ml/h) and applied voltage (18-26 kV), capsules were obtained with a 600-1000 nm size range. At constantly applied voltages, the increase in flow rate increased the capsule size up to 40% (ANOVA, p ≤ 0.05), while at constant flow rates, the increase in applied voltage reduced the average capsule size by 3.4-26% (ANOVA, p ≤ 0.05). The results from the Taguchi design represented the significance of solution flow rate, applied voltage, and solution concentration. It was shown that the most effective parameter on the size of capsules is flow rate. This research demonstrated that electrospray can be utilized as a convenient method for the preparation of sub-micron PMMA capsules containing EC. Furthermore, the morphology of the capsules is dominated by solvents, PMMA concentration, and PMMA:EC ratio, while the average size of the capsules can be altered by adjusting the flow rate and applied voltage of the electrospray process.

Effect of silanization of poly (urea-formaldehyde) microcapsules on the flexural strength and self-healing efficiency of an experimental self-healing dental resin composite (An in-vitro study)

OBJECTIVES

This study investigated the impact of using γ-methacryloxypropyl trimethoxy silane (MPS) for surface silanization of poly (urea-formaldehyde) (PUF) microcapsules which enclose a healing liquid of "triethylene glycol dimethacrylate (TEGDMA) and N,N dihydroxyethyl-p-toluidine (DHEPT)" on some mechanical properties of an experimental dental composite as well as its self-healing efficiency.

METHODS

Synthesis of PUF microcapsules was done via in situ polymerization, followed by silanization with MPS silane. Silanized and non-silanized microcapsules were incorporated into a composite containing 30% polymer matrix and 70% fillers at different weight percentages (0%, 5%, 7.5% and 10%). The composite strength and elastic modulus were evaluated by Flexural testing. Fracture toughness KIc and self-healing efficiency were assessed by utilizing the "single edge notched beam" method.

RESULTS

Flexural strength of all groups containing silanized microcapsules was non-significantly different from control group without microcapsules. However, in contrast to control group, all groups containing non-silanized microcapsules displayed considerably decreased flexural strength. Adding silanized and non-silanized microcapsules didn't show a significant change in the KIc-virgin. The silanized microcapsules' groups achieved a self-healing efficiency of about 49-77% recovery in KIc-virgin compared to 38-69% for their non-silanized counterparts.

SIGNIFICANCE

In order to increase the interfacial adhesion with the polymer matrix, improve the mechanical properties, and increase the efficiency of self-healing of dental resin composite, PUF microcapsules were silanized for the first time in the dental field using MPS silane. This innovative silanized microcapsule-containing self-healing composite may hold promise for repairing the damage caused by restorative cracks and extending their service life.

Improved viability of probiotics by encapsulation in chickpea protein matrix during simulated gastrointestinal digestion by succinylated modification

The potential application of succinylated chickpea protein (SCP) as a wall material for spray-dried microencapsulated probiotics was investigated. The results showed that succinylation increased the surface charge of chickpea proteins (CP) and reduced the particle size of the proteins. Meanwhile, succinylated modification decreased the solubility of protein under acidic conditions and increased the solubility in alkaline conditions. The effects of spray drying and in vitro gastrointestinal digestion on probiotics were investigated by microencapsulating chickpea protein with different degrees of N-succinylation. The results showed that all microcapsules had similar morphology, particle size and low water content. The microcapsules prepared by succinylated chickpea protein showed better stability and viability during spray drying and gastrointestinal digestion. The protective effect of probiotics was better as the degree of N-succinylation increased. In particular, the SCP-3-P sample (10 % succinic anhydride modified CP and maltodextrin) lost only 0.29 Log CFU/g throughout gastrointestinal digestion. The superior protective effect provided by succinylated CP in simulated gastric fluid (SGF) was mainly attributed to the reaction of succinic anhydride with protein to cause protein aggregation under gastric acidic conditions, reducing the infiltration of gastric acid and pepsin and maintaining the structural integrity of the microcapsules. Therefore, these findings provide a new strategy for probiotic intestinal delivery and application of chickpea protein.

Encapsulated lignin-based slow-release manganese fertilizer with reduced cadmium accumulation in rice (Oryza sativa L.)

As an essential trace element for plant growth and development, manganese plays a crucial role in the uptake of the heavy metal cadmium by rice (Oryza sativa L.). In this study, we developed a novel slow-release manganese fertilizer named Mn@LNS-EL. Initially, lignin nanoparticles were derived from sodium lignosulfonate, and a one-step emulsification strategy was employed to prepare a water-in-oil-in-water (W/O/W) Pickering double emulsions. These double emulsions served as the template for interfacial polymerization of lignin nanoparticles and epichlorohydrin, resulting in the formation of microcapsule wall materials. Subsequently, manganese fertilizer (MnSO4) was successfully encapsulated within the microcapsules. Hydroponic experiments were conducted to investigate the effects of Mn@LNS-EL on rice growth and the cadmium and manganese contents in the roots and shoots of rice under cadmium stress conditions. The results revealed that the treatment with Mn@LNS-EL markedly alleviated the inhibitory effects of cadmium on rice growth, leading to notably lower cadmium levels in the rice roots and shoots compared to the specimens treated without manganese fertilizer. Specifically, there was a reduction of 37.9 % in the root cadmium content and a 17.1 % decrease in the shoot cadmium content. In conclusion, this study presents an innovative approach for the high-value utilization of lignin through effective encapsulation and slow-release mechanisms of trace-element fertilizers while offering a promising strategy for efficiently remediating cadmium pollution in rice.

Microparticles and multi-unit systems for advanced drug delivery

Microparticles have unique benefits in the formulation of multiparticulate and multi-unit type pharmaceutical dosage forms allowing improved drug safety and efficacy with favorable pharmacokinetics and patient centricity. On the other hand, the above advantages are served by high and well reproducible quality attributes of the medicinal product where even flexible design and controlled processability offer success as well as possible longer product life-cycle for the manufacturers. Moreover, the specific demands of patients can be taken into account, including simplified dosing regimens, flexible dosage, drug combinations, palatability, and ease of swallowing. In the more than 70 years since the first modified-release formulation appeared on the market, many new formulations have been marketed and many publications have appeared in the literature. More unique and newer pharmaceutical technologies and excipients have become available for producing tailor-made particles with micrometer dimensions and beyond. All these have contributed to the fact that the sub-units (e.g. minitablets, pellets, microspheres) that make up a multiparticulate system can vary widely in composition and properties. Some units have mucoadhesive properties and others can float to contribute to a suitable release profile that can be designed for the multiparticulate formula as a whole. Nowadays, there are some available formulations on the market, which are able to release the active substance even for several months (3 or 6 months depending on the type of treatment). In this review, the latest developments in technologies that have been used for a long time are presented, as well as innovative solutions such as the applicability of 3D printing to produce subunits of multiparticulate systems. Furthermore, the diversity of multiparticulate systems, different routes of administration are also presented, touching the ones which are capable of carrying the active substance as well as the relevant, commercially available multiparticle-based medical devices. The versatility in size from 1 µm and multiplicity of formulation technologies promise a solid foundation for the future applications of dosage form design and development.

Microencapsulation for Pharmaceutical Applications: A Review

In order to improve bioavailability, stability, control release, and target delivery of active pharmaceutical ingredients (APIs), as well as to mask their bitter taste, to increase their efficacy, and to minimize their side effects, a variety of microencapsulation (including nanoencapsulation, particle size <100 nm) technologies have been widely used in the pharmaceutical industry. Commonly used microencapsulation technologies are emulsion, coacervation, extrusion, spray drying, freeze-drying, molecular inclusion, microbubbles and microsponge, fluidized bed coating, supercritical fluid encapsulation, electro spinning/spray, and polymerization. In this review, APIs are categorized by their molecular complexity: small APIs (compounds with low molecular weight, like Aspirin, Ibuprofen, and Cannabidiol), medium APIs (compounds with medium molecular weight like insulin, peptides, and nucleic acids), and living microorganisms (such as probiotics, bacteria, and bacteriophages). This article provides an overview of these microencapsulation technologies including their processes, matrix, and their recent applications in microencapsulation of APIs. Furthermore, the advantages and disadvantages of these common microencapsulation technologies in terms of improving the efficacy of APIs for pharmaceutical treatments are comprehensively analyzed. The objective is to summarize the most recent progresses on microencapsulation of APIs for enhancing their bioavailability, control release, target delivery, masking their bitter taste and stability, and thus increasing their efficacy and minimizing their side effects. At the end, future perspectives on microencapsulation for pharmaceutical applications are highlighted.

Preparation and characterization of active films based on oregano essential oil microcapsules/soybean protein isolate/sodium carboxymethyl cellulose

This study aimed to prepare oregano essential oil microcapsules (EOMs) by the active coalescence method using gelatin and sodium alginate as wall materials and oregano essential oil (OEO) as the core material. EOMs were added to the soybean protein isolate (SPI)/sodium carboxymethyl cellulose (CMC) matrix to prepare SPI-CMC-EOM active films, and the physical and chemical features of the active films and EOMs were characterized. The results showed that the microencapsulated OEO could protect its active ingredients. Scanning electron microscopy results showed that EOMs were highly compatible with the film matrix. The solubility of active films decreased upon adding EOMs, and their ultraviolet resistance and thermal stability also improved. When the added amount of EOMs was 5 %, the active films had the best mechanical properties and the lowest water vapor permeability. The active films prepared under this condition had excellent comprehensive performance. Also, adding EOMs considerably enhanced the antioxidant of the active films and endowed them with antibacterial properties. The application of the SPI-CMC-EOM films to A. bisporus effectively delayed senescence and maintained the freshness of the postharvest A. bisporus. This study provided a theoretical foundation for the incorporation of EOMs into active films based on biological materials.

The effects of stiffness on the specificity and avidity of antibody-coated microcapsules with target cells are strongly shape dependent

Antibody modification is a common method for endowing drug carriers with the ability to target specific cells. Recent studies suggest that the efficacy of these antibody-modified drug carriers is closely related to their physicochemical properties, such as size, shape, stiffness, charge, and surface chemistry. In this study, we functionalized microcapsules with antibodies to investigate the combined effect of shape and stiffness on their targeting ability. We synthesized hollow microcapsules, both spherical and rod-shaped, with adjustable stiffness using calcium carbonate particles as templates and silk fibroin (SF) as the shell material. These microcapsules were then functionalized with trastuzumab (TTZ) to enhance targeting capabilities. Our analysis revealed that increasing stiffness significantly improved the specificity and avidity of TTZ-coated rod-shaped microcapsules, but not spherical ones, indicating a strong shape-dependent influence of stiffness on these properties. Additionally, we explored the mechanisms of endocytosis using various inhibitors and found that both macropinocytosis and clathrin played critical roles in the cellular uptake of microcapsules. Furthermore, we loaded microcapsules with doxorubicin (DOX) to evaluate their anti-tumor efficacy. The stiffest TTZ-coated, DOX-loaded rod-shaped microcapsules demonstrated the most potent anti-tumor effects on BT-474 cells and the highest uptake in BT-474 3D spheroids. This research contributes to the development of more effective microcapsule-based target delivery systems and the realization of the full potential of microcapsule drug delivery systems.

Enhance the resistance of probiotics by microencapsulation and biofilm construction based on rhamnogalacturonan I rich pectin

Microcapsules were always used as functional material carriers for targeted delivery and meanwhile offering protection. However, microcapsule wall materials with specific properties were required, which makes the choice of wall material a key factor. In our previous study, a highly branched rhamnogalacturonan I rich (RG-I-rich) pectin was extracted from citrus canning processing water, which showed good gelling properties and binding ability, indicating it could be a potential microcapsule wall material. In the present study, Lactiplantibacillus plantarum GDMCC 1.140 and Lactobacillus rhamnosus were encapsulated by RG-I-rich pectin with embedding efficiencies of about 65 %. The environmental tolerance effect was evaluated under four different environmental stresses. Positive protection results were obtained under all four conditions, especially under H2O2 stress, the survival rate of probiotics embedded in microcapsules was about double that of free probiotics. The storage test showed that the total plate count of L. rhamnosus encapsulated in RG-I-rich pectin microcapsules could still reach 6.38 Log (CFU/mL) at 25 °C for 45 days. Moreover, probiotics embedded in microcapsules with additional incubation to form a biofilm layer inside could further improve the probiotics' activities significantly in the above experiments. In conclusion, RG-I-rich pectin may be a good microcapsule wall material for probiotics protection.

Preparation and characterization of a modified Canna starch as a wall material for the encapsulation of methyleugenol improves its antifungal activity against Fusarium trichothecioides

In this study, α-amylase (α-A) and 2-octenylsuccinic anhydride (OSA)-modified Canna starch (Cs) were prepared and characterized as wall materials and encapsulated with methyleugenol (α-A-OSA-Cs-methyleugenol); their in vitro antifungal activity against Fusarium trichothecioides (F. trichothecioides) was also investigated. The encapsulation efficiency under optimal encapsulation conditions was 83.98%. The results of particle size, polydispersity index (PDI), zeta potential, electron scanning microscopy and Fourier transform infrared spectroscopy showed that the modified Cs had superior physicochemical properties; it was also demonstrated that methyleugenol successfully entered the pores of Cs. The in vitro release study showed that α-A-OSA-Cs could effectively reduce their volatility under different temperature environments. α-A-OSA-Cs have excellent performance as slow-release wall materials, and after encapsulation with methyleugenol, the inhibition ability of F. trichothecioides mycelium growth was dose-dependent and improved, extending the shelf life of potatoes, which has good commercial value in the field of slow-release preservatives.

Preparation and synbiotic interaction mechanism of microcapsules of Bifidobacterium animalis F1-7 and human milk oligosaccharides (HMO)

Probiotics such as Bifidobacterium spp. generally possess important physiological functions. However, maintaining probiotic viability is a challenge during processing, storage, and digestive transit period. Microencapsulation is widely considered to be an attractive approach. In this study, B. animalis F1-7 microcapsules and B. animalis F1-7-HMO microcapsules were successfully prepared by emulsification/internal gelation with high encapsulation efficiency (90.67 % and 92.16 %, respectively). The current study revealed that HMO-supplemented microcapsules exhibited more stable lyophilized forms and thermal stability. Additionally, a significant improvement in probiotic cell viability was observed in such microcapsules during simulated gastrointestinal (GI) fluids or storage. We also showed that the individual HMO mixtures 6'-SL remarkably promoted the growth and acetate yield of B. animalis F1-7 for 48 h (p < 0.05). The synbiotic combination of 6'-SL with B. animalis F1-7 enhanced SCFAs production in vitro fecal fermentation, decreasing several harmful intestinal bacteria such as Dorea, Escherichia-Shigella, and Streptococcus while enriching the probiotic A. muciniphila. This study provides strong support for HMO or 6'-SL combined with B. animalis F1-7 as an innovative dietary ingredient to bring health benefits. The potential of the synbiotic microcapsules with this combination merits further exploration for future use in the food industry.

Release mechanism of UV responded chitosan-decorated TiO2 microcapsules: Regulation of humidity

In this research, the synergistic influences of UV light and relative humidity on the structure and immediate triggered release abilities of microcapsules loaded with oregano essential oil (OEO) were investigated. The microcapsules sufficiently were encouraged to release OEO by UV irradiation and regulated by ambient humidity. Relatively low humidity from 23 to 58% had no impact on the encapsulation efficiency and release processes of microcapsules in food simulations and air significantly. Analysis of microstructure showed that UV irradiation and higher relative humidity were conducive to fracturing glycosidic bonds of microcapsule shell through hydroxyl radicals generated by TiO2 and vapour. Finally, microcapsules were applied to the preservation of chicken breasts for 6 d and the results showed that chicken breasts with microcapsules that had been irradiated by UV light at 76 %RH would have better quality and the shelf life was extended, which evidenced its excellent foreground in meat preservation.

Synthesis and characterisation of microcapsules for self-healing dental resin composites

AIM

The purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures.

MATERIALS & METHODS

Microcapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently.

RESULT

Average diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 μm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%.

CONCLUSION

TEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.

Eucalyptol-loaded microcapsules combined with Cynanchum komarovii extracts provide long-term and low-risk management of Chinese wolfberry (Lycium barbarum L.)

Realizing eco-friendly, long-term, and low-risk aphid control on Lycium barbarum (medicinal cash crop) using a Cynanchum komarovii extracts and eucalyptus oil-loaded microcapsules (EOMCs) formulation compositions is viable. In this study, the aim is to optimize the composition of Cynanchum komarovii extracts and EOMCs formulation for effective control of aphids, the release of EOMCs was controlled by changing the cross-linking degree of the shell to match the aphid control characteristics of Cynanchum komarovii extracts. Four types of polyamines were used as cross-linking agents for the preparation of EOMCs by interfacial polymerization. The bioactivity, wettability, and field application efficacy of Cynanchum komarovii extracts and different EOMCs formulation compositions were evaluated. These EOMCs exhibited an encapsulation efficiency exceeding 85 %. The control efficiency of the formulation compositions of microcapsules with a moderate release rate and Cynanchum komarovii extracts on aphids remained at 62.86 %, while the control efficiency of the combination of microcapsules with the fastest and slowest rates with Cynanchum komarovii extracts was only 48.62 % and 57.11 %, respectively. The formulation compositions of Cynanchum komarovii extracts with all four types of EOMCs were found to be safe for Chinese wolfberry plants. Overall, by selecting appropriate polyamines during fabrication, the release rate can be effectively controlled to achieve sustainable and low-risk aphid control in Lycium barbarum through compounding with selected microcapsules.

Smart antibacterial nanocellulose packaging film based on pH-stimulate responsive microcapsules synthesized by Pickering emulsion template

Spoilage results in food waste and endangers consumer health, and the smart antibacterial packaging can effectively inhibit bacterial growth and reduce food spoilage. In this study, the smart antibacterial nanocellulose packaging films were developed by adding the pH-stimulated responsive microcapsules into cellulose nanofibril (CNF) film-forming. The microcapsules were synthesized by interfacial polymerization of Pickering emulsion. Carboxylated cellulose nanocrystals as solid particles stabilized the composited oil phase to prepare the oil-in-water Pickering emulsion. The emulsion with the particle concentration of 1.25 wt% and the oil phase mass fraction of 7.5 % processes excellent stability and uniform particle size, was chosen to synthesize microcapsules. The cinnamaldehyde in the film with the addition amount of microcapsules 0.6 g burst released in the first 1 h and then slowly, and the cumulative release at pH 2.0, 4.0, 5.5 and 7.2 was 28.43 μg/cm2, 18.84 μg/cm2, 16.52 μg/cm2 and 12.89 μg/cm2, respectively. The inhibitory rate of film against both E. coli and L. monocytogenes reached 99 % at pH 4.0. The shelf life of pork packed by the film prolonged to nearly 9 d at room temperature. The developed films have the potential to be used in food packaging.

A multidimensional optimization strategy of pyraclostrobin-loaded microcapsules to improve the selectivity between toxicological risk in zebrafish and efficacy in controlling rice blast

Developing microcapsules (MCs) delivery systems can effectively mitigate toxicological risk of highly active/toxic pesticides; whereas the controlled release functions also limiting their practical effectiveness. Therefore, designing a precise regulating strategy to balance the toxicity and bioactivity of MCs is urgently needed. Here, we prepared a series of pyraclostrobin-loaded MCs with different wall materials, particle sizes, core density and shell compactness using interfacial polymerization. The results showed that the MCs released more slowly in water with increasing particle sizes and capsule compactness, and they sunk more quickly with the increasing particle sizes and core density. Additionally, MCs with slower release speed was always accompanied with lower acute toxicity levels to zebrafish. When the release dynamics slowed down to the threshold dose on demand for disease control, facilitating settlement of MCs can further reduce toxicity within spatial and temporal dimensions. The poor accumulation of MCs with larger particle sizes or dense shell in gills was closely related to their efficient detoxification. Importantly, seven of the MCs samples possessed superior selectivity between bio-performance in controlling rice blast and toxicological hazard to fish compared to commercial formulations. The results provide a comprehensive guidance for developing an efficient and safe pesticide delivery system.

10-hydroxycamptothecin-loaded starch-based microcapsules with the stepwise responsive release strategy for targeted controlled release

Controlled and accurate drug release at the target site have been the focus of research. Especially in cancer therapy, economical, convenient and accurate delivery strategies could help to reduce the toxic effects of drugs on normal tissues and improve drug availability. In the study, glutathione (GSH)-responsive microcapsules (FA-RSMCs) were prepared by sonochemical method based on thiolated modified starch. 10-Hydroxycamptothecin (HCPT) was designed as a reactive oxygen species (ROS)-responsive polyprodrug (polyHCPT), which was loaded into the core of the microcapsules to obtain stepwise released drug delivery carriers. In the tumor microenvironment, FA-RSMCs first triggered GSH-responsive cleavage to release polyHCPT, followed by ROS-responsive cleavage of polyHCPT to release intact HCPT drug molecules. The results of experiments in simulated tumor microenvironment showed that FA-RSMCs exhibited good cascade-response release properties in vitro. It exhibited good anti-tumor ability and protection of normal cells in cytotoxicity in vitro. This strategy enhanced the accuracy and safety of targeted delivery of HCPT via microcapsules, which has potential for clinical application.

Novel antimicrobial and self-healing dental resin to combat secondary caries and restoration fracture

OBJECTIVE

Dental resin composites have been the most popular materials for repairing tooth decay in recent years. However, secondary caries and bulk fracture are the major hurdles that affect the lifetime of dental resin composites. This current study synthesized a novel antimicrobial and self-healing dental resin containing nanoparticle-modified self-healing microcapsules to combat secondary caries and restoration fracture.

METHODS

Multifunctional dental resins containing 0-20% nanoparticle-modified self-healing microcapsules were prepared. The water contact angle, antimicrobial properties, mechanical properties, cell toxicity, and self-healing capability of the dental resins were tested.

RESULTS

A novel multifunctional dental resin was synthesized. When the microcapsule mass fraction was 10%, the resin presented a strong bacteriostasis rate (80.3%) and excellent self-healing efficiency (66.1%), while the hydrophilicity, mechanical properties, and cell toxicity were not affected.

SIGNIFICANCE

The novel antimicrobial self-healing dental resin is a promising candidate for use in clinical practice, which provides a simple and highly efficient strategy to combat secondary caries and restoration fracture. This novel dental resin also gives the inspiration to prolong the service life of dental restorations.

Characterization and stability investigation of rhein encapsulated microcapsules using different enteric biopolymers with pullulan and Jiuzao glutelin conjugates via Maillard reaction

The poor water solubility and rhein (RH) stability limit its application in the functional food industry. In the present study, the RH-loaded water-in-oil-in-water nano emulsion and microcapsules were prepared using the conjugates of pullulan-Jiuzao glutelin (JG) (m/m, 2:1, PJC-2) obtained by Maillard reaction and enteric-soluble materials (polymethlacrylic acid, hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate, and D-mannitol). The effects of different formulations on the microstructure, physicochemical properties, and storage stability of microcapsules were analyzed. The results showed that microcapsules exhibited stability against different external environments. The encapsulation efficiency of RH in the four enteric-soluble-PJC-2 double-deck microcapsules (70.03 ± 3.24%-91.08 ± 4.78%) was significantly improved than PJC-2 ones (61.84 ± 0.47%). The antioxidant activity and stability of RH in the microcapsules were improved (ABTS, 49.7%-113.93%; DPPH, 40.85%-101.82%; FRA, 62.32%-126.42%; and FCA, 70.58%-147.20%) after in vitro simulated digestion and extreme environmental conditions compared to free RH. This work provides a microcapsule based on PJC-2 with enteric-soluble materials for insoluble functional ingredients to improve solubility, stability, and bioactivity in the food industry.

Preparation and curing behaviour of microencapsulated curing agents for cold-mixed epoxy asphalt

This study aimed to improve control over the curing behaviour of cold-mixed epoxy asphalt by using a microencapsulated curing agent (2-PZ@PC). Prepared through solvent evaporation, the 2-PZ@PC microcapsules had 2-phenylimidazole as the core material and polycarbonate as the shell material. The research examined the impact of core-shell mass ratio on microcapsule morphology and composition. Various equations, including the kinetics equation, Kissinger equation, Flynn-Wall-Ozawa, and Crane equations, were employed to assess the sustained release effect of 2-PZ@PC microcapsules on epoxy resin curing behaviour. Fluorescence microscopy and viscosity experiments were used to observe the release state of microcapsules and confirm the retardation phenomenon during construction. Optimal 2-PZ@PC microcapsules displayed a smooth spherical morphology and a maximum encapsulation rate of 32 wt% at a 1:1 core-shell ratio. The microencapsulated curing agent effectively regulated cold-mixed epoxy asphalt's curing behaviour, enhancing retention time control and application reliability.

A review on chitosan and alginate-based microcapsules: Mechanism and applications in drug delivery systems

Natural polymers, like chitosan and alginate have potential of appearance, as well as the changes and handling necessary to make it acceptable vehicle for the controlled release of medicines and biomolecules. Microcapsules are characterized as micrometer-sized particulate that can be employed to store chemicals within them. In the present review, we have discussed various advantages, components of microcapsules, release mechanisms, preparation methods, and their applications in drug delivery systems. The preparation methods exhibited strong encapsulation effectiveness and may be used in a wide range of pharmaceutical and biomedical applications. The major advantages of using the microencapsulation technique are, sustained and controlled delivery of drugs, drug targeting, improvement of shelf life, stabilization, immobilization of enzymes and microorganisms. As new biomaterials are developed for the body, they are better suited to the development of pharmaceutical systems than traditional pharmaceuticals because they are more reliable, biocompatible, biodegradable, and nontoxic. Furthermore, the designed microcapsules had been capable of shielding the essential components from hostile environments. More advanced techniques could be developed in the future to facilitate the formulation and applications of microcapsules and working with the pharmaceutical and medical industries.

Covalent Organic Framework Based Crosslinked Porous Microcapsules for Enzymatic Catalysis

The design of porous microcapsules with selective mass transfer and mechanical robustness for enzyme encapsulation is highly desired for biocatalysis, yet the construction remains challenging. Herein, we report the facile fabrication of porous microcapsules by assembling covalent organic framework (COF) spheres at the interfaces of emulsion droplets followed by interparticle crosslinking. The COF microcapsules could offer an enclosed aqueous environment for enzymes, with size-selective porous shells that allow for the fast diffusion of substrates and products while excluding larger molecules such as protease. Crosslinking of COF spheres not only enhances the structural stability of capsules but also imparts enrichment effects. The enzymes encased in the COF microcapsules show enhanced activity and durability in organic media as verified in both batch reaction and continuous-flow reaction. The COF microcapsules offer a promising platform for the encapsulation of biomacromolecules.

Melanin inspired microcapsules delivering immune metabolites for hepatic fibrosis management

Patients with hepatic fibrosis (HF) have a high risk of developing liver cirrhosis and hepatocellular carcinoma, and there is an urgent need for preventive strategies to block this process. Previous studies have found that disordered inflammation and oxidative damage play important roles in HF progression, suggesting two attractive therapeutic targets. Herein, a new kind of bioinspired microcapsules with a core-shell structure is generated using microfluidics. Polydopamine nanoparticles (PDANPs), a synthetic analogue of natural melanin, are embedded in the polymer shell to provide antioxidative properties for these microcapsules. The aqueous core is used to encapsulate ketone body β-hydroxybutyrate (BHB), an energy metabolite recently known to have regulating effects of cellular signals involved in chronic inflammation. In a HF mouse model, the BHB-encapsulated PDANPs-embedded microcapsules (BHB-PDA-MCs) can not only decrease the severity of inflammatory response, but also the level of oxidative stress. As a result, this combinational strategy is demonstrated to prevent the activation of hepatic stellate cells, the accumulation of extracellular matrix, and the damage of hepatic lobules. These findings indicate that BHB-PDA-MCs can be a promising drug delivery system and have a synergistic effect on HF management.

In vitro bioaccessibility evaluation of chlorophyll pigments in single and binary carriers

Chlorophyll was extracted and microencapsulated using different carrier agents. Subsequently, in vitro digestion was performed, and the bioaccessibility of chlorophyll in the different encapsulation systems was carried out. The zeta potential, particle size, and PDI were significantly modified after the micellarization of digested microcapsules. I-W-Chl presented with the highest total chlorophyll recovery and micellarization rate of 54% and 43%, respectively. In the aqueous micellar fraction, the different encapsulation systems had total chlorophylls, pheophytins, and pheophorbides ranging from 13 to 49%, 42 - 77%, and 3 - 22% respectively. The bioaccessibility of total chlorophyll pigment ranging from 7% to 20% is given in the following order: I-W-Chl > WPI-Chl > Z-Chl > Ca-Chl > SCChl^V > SCChl^C. The result established in this study shows that the carrier agent type could inhibit or mediate the bioaccessibility of chlorophyll with the potential to be an efficient delivery system for health promoting compounds.

Protein and polysaccharide based encapsulation of ginger oleoresin: impact of wall materials on powder stability, release rate and antimicrobial characteristics

Ginger oleoresin is widely used as a flavouring agent in many foods. But its bioactive components are unstable as being sensitive to heat, humidity and light. Hence this study proposes the encapsulation of ginger oleoresin in order to protect it and regulate its release in the gastrointestinal system via spray drying utilising whey protein isolate (WPI) and gum Acacia (GA) as wall materials. The feed emulsions used were characterised for emulsion stability, viscosity, droplet size and thermal properties. The GA microcapsules had a substantially greater mean particle diameter (1980 nm) than WPI microcapsules (1563 nm). The WPI microcapsules retained high content of 6-and 8-gingerol (89.57 and 12.54 mg g-1) compared to GA. The WPI microcapsules showed the largest mean inhibition zone with diameter of 16.64 mm against Escherichia coli and 22.68 mm against Staphylococcus aureus making them most effective in preventing the growth of test bacteria. Both WPI and GA microcapsules exhibited zeta potential value in the range of (-21.09 to -27.35 mV) indicating excellent colloidal stability. The highest concentration of antioxidant activity (73.33 %) and total phenols (33.92 mg g-1) was retained by WPI microcapsules in intestinal juice which ensures intestinal regulatory release.

Development of probiotic loaded multilayer microcapsules incorporated into dissolving microneedles for potential improvement treatment of vulvovaginal candidiasis: A proof of concept study

Vulvovaginal candidiasis (VVC) is a vaginal infection caused by abnormal growth of Candida sp., especially Candida albicans, in the vaginal mucosa. A shift in vaginal microbiota is prominent in VVC. The presence of Lactobacillus plays a vital role in maintaining vaginal health. However, several studies have reported resistance of Candida sp. against azoles drugs, which is recommended as VVC treatment. The use of L. plantarum as a probiotic would be an alternative to treat VVC. In order to exert their therapeutic activity, the probiotics needed to remain viable. Multilayer double emulsion was formulated to obtain L. plantarum loaded microcapsules (MCs), thus improving its viability. Furthermore, a vaginal drug delivery system using dissolving microneedles (DMNs) for VVC treatment was developed for the first time. These DMNs showed sufficient mechanical and insertion properties, dissolved rapidly upon insertion, facilitating probiotic release. All formulations proved non-irritating, non-toxic, and safe to apply on the vaginal mucosa. Essentially, the DMNs could inhibit the growth of Candida albicans up to 3-fold than hydrogel and patch dosage forms in ex vivo infection model. Therefore, this study successfully developed the formulation of L. plantarum-loaded MCs with multilayer double emulsion and its combination in DMNs for vaginal delivery to treat VVC.

In vitro bioaccessibility evaluation of pheophytins in gelatin/polysaccharides carrier

The type of carrier agent could impact pheophytin stability and bioaccessibility. Hence, it is important to have an elaborate understanding on the extent and type of pheophytin transformation during in vitro digestion of microcapsules. Four kinds of protein/polysaccharides complex were used to fabricate pheophytin microcapsules and investigated for pigments bioaccessibility. With different carriers, pheophytin pigments showed new characteristics influencing particle size and zeta potential during in vitro digestion. Pheophytin b was widely transformed to pheophorbide b, confirming pheophorbidation of the b series in proper condition. No 15¹-hydroxy lactone chlorophyll or pheophytin derivatives were detected, indicating some protective effect of microencapsulation. Pheophytins loaded in gelatin-pectin complex exhibited a relatively higher recovery rate, micellarization rate, and bioaccessibility index. The result presented in this study shows that the type of carrier agent could initiate the removal of phytyl groups in pheophytins and also inhibit or mediate their bioaccessibility.

Spatiotemporal variation in microplastics derived from polymer-coated fertilizer in an agricultural small river in Ishikawa Prefecture, Japan

Marine plastic pollution has highlighted the need to address the disposal of plastic materials used in agricultural fields and prevent their runoff. To assess the status of microplastics derived from polymer-coated fertilizers (microcapsules), we investigated their seasonal and daily variations in a small agricultural river in Ishikawa Prefecture, Japan, throughout the irrigation period of April to October 2021 and 2022. We also investigated the relationship between microcapsule concentration and water quality. The mean microcapsule concentration over the study period ranged from 0.0 to 783.2 mg/m³ (median 18.8 mg/m³) and was positively correlated with total litter weight, but it was not correlated with common water quality parameters such as total nitrogen or suspended solids. Concentrations of microcapsules in river water showed distinct seasonal variations, being particularly high in late April and late May (median 55.5 mg/m³ in 2021, 62.6 mg/m³ in 2022) and almost undetectable thereafter. The timing of the increase in concentration coincided with the timing of the outflow from paddy fields, suggesting that microcapsules that flowed out of the paddy fields would reach the sea relatively quickly. The results of a tracer experiment supported this conclusion. Intensive observations revealed that microcapsule concentrations varied widely over time, with differences reaching a maximum of 110-fold (range 7.3-783.2 mg/m³) over a 3-day period. Daytime concentrations were higher than those at night, reflecting the fact that microcapsules are discharged from paddies by daytime operations such as puddling and surface drainage. Microcapsule concentrations in the river were not correlated with river discharge, making estimating their loading a future research challenge.

Promoting β-cells function by the recapitulation of in vivo microenvironmental differentiation signals

The study aims to transdifferentiate rat bone marrow-derived mesenchymal stem cells (BM-MSCs) more efficiently into islet-like cells and encapsulate and transplant them with vital properties like stability, proliferation, and metabolic activity enhanced for the treatment of T1DM. Trans-differentiation of BM-MCs into islet-like cells induced by high glucose concentration combined with Nicotinamide, ꞵ-Mercaptoethanol, ꞵ-Cellulin, and IGF-1. Glucose challenge assays and gene expression profiles were used to determine functionality. Microencapsulation was performed using the vibrating nozzle encapsulator droplet method with a 1% alginate concentration. Encapsulated ꞵ-cells were cultured in a fluidized-bed bioreactor with 1850 μL/min fluid flow rates and a superficial velocity of 1.15 cm/min. The procedure was followed by transplanting transdifferentiated cells into the omentum of streptozotocin (STZ)-induced diabetic Wistar rats. Changes in weight, glucose, insulin, and C-peptide levels were monitored for 2 months after transplantation. PDX1, INS, GCG, NKx2.2, NKx6.1, and GLUT2 expression levels revealed the specificity of generated β-cells with higher viability (about 20%) and glucose sensitivity about twofold more. The encapsulated β-cells decreased the glucose levels in STZ-induced rats significantly (P < 0.05) 1 week after transplantation. Also, the weight and levels of insulin and C-peptide reached the control group. In contrast to the treated, the sham group displayed a consistent decline in weight and died when loss reached > 20% at day ~ 55. The coated cells secrete significantly higher amounts of insulin in response to glucose concentration changes. Enhanced viability and functionality of β-cells can be achieved through differentiation and culturing, a promising approach toward insulin therapy alternatives.

Engineering Flexible Metal-Phenolic Networks with Guest Responsiveness via Intermolecular Interactions

Flexible metal-organic materials are of growing interest owing to their ability to undergo reversible structural transformations under external stimuli. Here, we report flexible metal-phenolic networks (MPNs) featuring stimuli-responsive behavior to diverse solute guests. The competitive coordination of metal ions to phenolic ligands of multiple coordination sites and solute guests (e.g., glucose) primarily determines the responsive behavior of the MPNs, as revealed experimentally and computationally. Glucose molecules can be embedded into the dynamic MPNs upon mixing, leading to the reconfiguration of the metal-organic networks and thus changes in their physicochemical properties for targeting applications. This study expands the library of stimuli-responsive flexible metal-organic materials and the understanding of intermolecular interactions between metal-organic materials and solute guests, which is essential for the rational design of responsive materials for various applications.

Microcapsules loaded with date seed extract and its inhibitory potential to modulate the toxic effects of mycotoxins in mice received mold-contaminated diet

Mycotoxins are the secondary fungal metabolites generally produced by wide range of fungi including aflatoxins (AF), ochratoxin A (OTA), fumonisins (FB), zearalenone (ZEN), and deoxynivalenol (DON). Nowadays, they are main concern to food and agricultural commodities due to undesirable health and socio-economic effect. This investigation was designed to synthesized microcapsules loaded the bioactive compounds of date seed and evaluated its inhibitory activities in mice received mold-contaminated diet. The finding revealed that the developed microcapsule is homogenous and mostly spherical with size of 2.58 μm with acceptable PDI of 0.21. The main phytochemical has been confirmed by HPLC analysis were xylose, fructose, mannose, glucose, and galactose with the respective values of 41.95%, 2.24%, 5.27%, and 0.169%. The in vivo analyses manifested that the mice received date seed microcapsules significantly (p < 0.05) improved the average daily weight gain, feed intake, liver enzymes (ALT, ALP, and AST), and lipid peroxidation values compare to mice group received mycotoxin-contaminated diet. Furthermore, encapsulation date seed bioactive compounds notably up-regulated the expression of GPx, SOD, IFN-γ, and IL-2 genes while down-regulated the iNOS gene. Consequently, the novel microcapsules loaded date seed is suggested to be considered as a promising mycotoxin inhibitor.

A method for real-time mechanical characterisation of microcapsules

Characterising the mechanical properties of flowing microcapsules is important from both fundamental and applied points of view. In the present study, we develop a novel multilayer perceptron (MLP)-based machine learning (ML) approach, for real-time simultaneous predictions of the membrane mechanical law type, shear and area-dilatation moduli of microcapsules, from their camera-recorded steady profiles in tube flow. By MLP, we mean a neural network where many perceptrons are organised into layers. A perceptron is a basic element that conducts input-output mapping operation. We test the performance of the present approach using both simulation and experimental data. We find that with a reasonably high prediction accuracy, our method can reach an unprecedented low prediction latency of less than 1 millisecond on a personal computer. That is the overall computational time, without using parallel computing, from a single experimental image to multiple capsule mechanical parameters. It is faster than a recently proposed convolutional neural network-based approach by two orders of magnitude, for it only deals with the one-dimensional capsule boundary instead of the entire two-dimensional capsule image. Our new approach may serve as the foundation of a promising tool for real-time mechanical characterisation and online active sorting of deformable microcapsules and biological cells in microfluidic devices.

Capsule-based colorimetric temperature monitoring system for customizable cold chain management

The COVID-19 pandemic and the resulting supply chain disruption have rekindled crucial needs for safe storage and transportation of essential items. Despite recent advances, existing temperature monitoring technologies for cold chain management fall short in reliability, cost, and flexibility toward customized cold chain management for various products with different required temperature. In this work, we report a novel capsule-based colorimetric temperature monitoring system with precise and readily tunable temperature ranges. Triple emulsion drop-based microfluidic technique enables rapid production of monodisperse microcapsules with an interstitial phase-change oil (PCO) layer with precise control over its dimension and composition. Liquid-solid phase transition of the PCO layer below its freezing point triggers the release of the encapsulated payload yielding drastic change in color, allowing user-friendly visual monitoring in a highly sensitive manner. Simple tuning of the PCO layer's compositions can further broaden the temperature range in a precisely controlled manner. The proposed simple scheme can readily be formulated to detect both temperature rise in the frozen environment and freeze detection as well as multiple temperature monitoring. Combined, these results support a significant step forward for the development of customizable colorimetric monitoring of a broad range of temperatures with precision.

Synthesis of microcapsules containing a formaldehyde scavenger for the sustainable control of hazardous chemical release from particleboard

Formaldehyde scavenger microcapsules were introduced into particleboard to prepare an ecofriendly particleboard with a low pollution release in response to the problem of long-term unstable free formaldehyde release from particleboards. By analyzing key parameters of formaldehyde emission from particleboard, the effects of microcapsules on the diffusion, migration and inhibition of free formaldehyde in particleboard pore structures was discussed. The results showed that microencapsulated formaldehyde scavenger prepared by an emulsification cross-linking method with chitosan as the wall material and urea as the core material resulted in a good long-term controlled release effect on formaldehyde emission. Compared with that of the control panel, the formaldehyde emission of the particleboard with microcapsules decreased by 51.4 % and 25.8 % at 28 d and 180 d, respectively. The addition of formaldehyde scavenger microcapsules increased the particleboard macroscopic pore volume, which facilitated the conversion of adsorbed formaldehyde into free formaldehyde in the pore structure, thereby promoting its migration and diffusion in the particleboard pores. Moreover, the synergistic effect of the addition-condensation and nucleophilic cross-linking of the core and wall materials quickly captured the free formaldehyde in the panels and reduced the releasable concentration of formaldehyde in the material, thus achieving the long-term effective control of formaldehyde emission.

Ion exchange fabrication of lanthanide functionalized layered double hydroxides microcapsules for rapid and visual detection of anthrax biomarker

Lanthanide ion probes have recently been considered as promising sensing materials due to their high sensitivity and good optical properties. Herein, the 3D hierarchical lanthanide functionalized layered double hydroxides microcapsules were synthesized via a facile ion exchange strategy and further developed as novel fluorescent probes for detecting trace amounts of the anthrax biomarker dipicolinicacid (DPA). Benefiting from the 3D porous superstructure and abundant unsaturated coordination sites of lanthanide ion, the ternary Ni-Fe-Ln-LDHs (Ln = Tb/Eu) not only possess a large reactive contact area to improve the sensitivity of DPA detection, but also demonstrate very fast reaction rate. The design of inexpensive fluorescent test strips can perform the on-site and real-time detection via a smartphone with a color recognition application. More prominently, the sensitivity of the system was evaluated by actual spore samples with the detection limit as low as 3.54 × 10⁴ spores/mL. The 3D lanthanide functionalized LDHs nanoprobe constructed by ion exchange exhibits a new vision for the development of a sensing platform in other research areas.

Recent progress in the synthesis of all-aqueous two-phase droplets using microfluidic approaches

An aqueous two-phase system (ATPS) is a system with liquid-liquid phase separation and shows great potential for the extraction, separation, purification, and enrichment of proteins, membranes, viruses, enzymes, nucleic acids, and other biomolecules because of its simplicity, biocompatibility, and wide applicability [1-4]. The clear aqueous-aqueous interface of ATPSs is highly advantageous for their implementation, therefore making ATPSs a green alternative approach to replace conventional emulsion systems, such as water-in-oil droplets. All aqueous emulsions (water-in-water, w-in-w) hold great promise in the biomedical field as glucose sensors [5] and promising carriers for the encapsulation and release of various biomolecules and nonbiomolecules [6-10]. However, the ultralow interfacial tension between the two phases is a hurdle in generating w-in-w emulsion droplets. In the past, bulk emulsification and electrospray techniques were employed for the generation of w-in-w emulsion droplets and the fabrication of microparticles and microcapsules in the later stage. Bulk emulsification is a simple and low-cost technique; however, it generates polydisperse w-in-w emulsion droplets. Another technique, electrospray, involves easy experimental setups that can generate monodisperse but nonspherical w-in-w emulsion droplets. In comparison, microfluidic platforms provide monodisperse w-in-w emulsion droplets with spherical shapes, deal with the small volumes of solutions and short reaction times and achieve portability and versatility in their design through rapid prototyping. Owing to several advantages, microfluidic approaches have recently been introduced. To date, several different strategies have been explored to generate w-in-w emulsions and multiple w-in-w emulsions and to fabricate microparticles and microcapsules using conventional microfluidic devices. Although a few review articles on ATPSs emulsions have been published in the past, to date, few reviews have exclusively focused on the evolution of microfluidic-based ATPS droplets. The present review begins with a brief discussion of the history of ATPSs and their fundamentals, which is followed by an account chronicling the integration of microfluidic devices with ATPSs to generate w-in-w emulsion droplets. Furthermore, the stabilization strategies of w-in-w emulsion droplets and microfluidic fabrication of microparticles and microcapsules for modern applications, such as biomolecule encapsulation and spheroid construction, are discussed in detail in this review. We believe that the present review will provide useful information to not only new entrants in the microfluidic community wanting to appreciate the findings of the field but also existing researchers wanting to keep themselves updated on progress in the field.

Survivability of probiotics encapsulated in kelp nanocellulose/alginate microcapsules on microfluidic device

Probiotics are living microorganisms that can produce health benefits to the host only when they are ingested in sufficient quantities and reach the intestines active state. However, the external environment that probiotics face for a long time before administration and the low pH environment in the stomach after administration can greatly reduce their activity. In this work, we proposed a simple microfluidic encapsulation strategy to efficiently prepare the probiotics-loaded nanocellulose/alginate delivery system, which can improve the storage stability and gastrointestinal survival rate of probiotics. The microcapsules were found to be monodisperse, and the average particle size was<500 μm by observing the microstructure and macroscopic morphology. The kelp nanocellulose was cross-linked in the microcapsule and formed a dense surface with alginate. Through the simulated gastrointestinal digestion experiment, it was found that the survival of probiotics in microcapsules containing 0.5 % and 1.5 % kelp nanocellulose decreased by 1.77 log CFU/g and 1.65 log CFU/g respectively, which was significantly lower than that of nanocellulose-free microcapsules (3.70 log CFU/g). And all the treated groups could release probiotics above 7 log CFU/g after digesting intestinal juice for 6 h. Furthermore, through the storage experiment, it was found that the microcapsules with 1.5 % kelp nanocellulose could still release 8.07 log CFU/g probiotics after four weeks. The results provide a new strategy for probiotics processing and extensive high-value utilization of marine natural products.

Stimulus responsive microcapsules and their aromatic applications

Fragrances and essential oils are promising for a wide range of applications due to their pleasant odors and diverse effects. However, direct addition to consumer products has the disadvantages of short retention time and easy deterioration of odor. At the same time, releasing a large amount of odor in a short time may be an unpleasant experience, which severely limits the practical application of aromatic substances. Microencapsulation perfectly solves these problems. Stimuli-responsive microcapsules, which combine environmental stimulation with microencapsulation, can not only effectively prevent the rapid decomposition and evaporation of aroma components, but also realize the "on-off" intelligent release of aroma substances to environmental changes, which have great promise in the field of fragrances. In this review, the application of stimuli-responsive microcapsules in fragrances is highlighted. Firstly, various encapsulation materials used to prepare stimuli-responsive aromatic microcapsules are described, mainly including some natural polymers, synthetic polymers, and inorganic materials. Subsequently, there is a detailed description of the common release mechanisms of stimuli-responsive aromatic microcapsules are described in detail. Finally, the application and future research directions are given for stimuli-responsive aromatic microcapsules in new textiles, food, paper, and leather.

Development of antioxidant active packaging films with slow release properties incorporated with tea polyphenols-loaded porous starch microcapsules

Slow release active packaging films can realize the sustained release of active agents and prolong the shelf life of food. For this aim, a novel slow release active polyvinyl alcohol (PVA) film was developed by using solution casting method. With porous starch loaded with tea polyphenols (PSTP) as core material and maltodextrin (MD) as wall material, PSTP@MD microcapsules were prepared using freeze drying method and used as slow release carrier of tea polyphenols (TP) in the active films. The interactions between PSTP@MD microcapsules and PVA molecular chains were physical interactions. In addition, the relative crystallinity of the slow release active films was reduced to 23.74 %. The addition of PSTP@MD microcapsules can enhance the ductility of active films and reduce the water content and swelling degree of active films by 46.74 % and 54.38 %, respectively. Moreover, the thermal stability, water vapor and ultraviolet barrier properties of active films were promoted. The transparency and antioxidant activity of active films was high, and the radical scavenging activity of active films was 58 %. The encapsulation of TP with PSTP@MD microcapsules can realize the slow release of TP. The slow release active films had antioxidant activity and sustained release properties, which could be used as an active packaging film to extend the shelf life of food.

Preparation and characterization of long-term antibacterial and pH-responsive Polylactic acid/Octenyl succinic anhydride-chitosan @ tea tree oil microcapsules

Encapsulation technology can increase the stability and maintain the volatile active substances of plant essential oils. In the present study, tree essential oil (TTO) was encapsulated with polylactic acid (PLA) modified by octenyl succinic anhydride chitosan (OSA-CS) as shell materials to form long-term antibacterial and pH-responsive microcapsules. The PLA/OSA-CS@TTO microcapsules were characterized by high performance liquid chromatography (HPLC), scanning electron microscopy (SEM) and antibacterial performance testing. The results showed that the average particle size of microcapsules was 10 μm, and the encapsulation efficiency and drug loading efficiency of TTO reached 81.5 % and 60.3 %. After 4800 min of release in media at different pH (5 and 7) still sequestered 55.32 % and 56.74 % of TTO which approved the shell of microcapsules responded to different pH values. The microcapsules remained stable for 80 days after drying, and preserving 39.7 % of the core material. The morphology of PLA/OSA-CS@TTO microcapsules revealed that the PLA/OSA-CS@TTO microcapsules presented smooth and firm structure. Antibacterial test for staphylococcus aureus of those microcapsules implied that the bacteriostatic rate reached 100 % after 72 h. Bio-based macromolecular modification strategies can provide inspiration for the development of green microcapsules.

Development of blueberry (Vaccinium corymbosum L.) waste powder as a potential food ingredient with functional properties

Salta province, northwestern Argentina, produces blueberries for export and discards fruits with a potential quantity of bioactive compounds. These bioactive compounds have health-promoting properties that prevent or delay the appearance of chronic diseases. This study aimed to formulate blueberry microcapsules using discarded fruit, to determine and evaluate the effect of spray-drying and lyophilization on the bioactive compounds and their physical properties. Fourteen capsule prototypes were obtained by applying a randomized full factorial design with two factors: type of drying and type of wall material. The former factor had two levels (spray-drying and lyophilization) and the latter had three levels, each with defined quantities to be used, namely maltodextrin (0%, 10%, 15%, and 30%), gum Arabic (0%, 10%, 15%, and 30%), and modified starch (0%, 10%, 15%, and 30%). Spray-drying, lyophilization, total polyphenols, anthocyanins, proanthocyanidins, antioxidant activity, and the physical properties of the microcapsules were analyzed using ANOVA, PCA, and cluster analysis. Results showed significant differences between the two processes (P < 0,05), with lyophilization being better at preserving bioactive compounds. The PCA test also showed a positive association between lyophilization and bioactive compounds, while spray-drying powders were related to negative characteristics, like moisture and water activity.

Plant polysaccharides as novel biomaterials for microcapsule construction and therapeutics delivery

Natural polysaccharides derived from medicinal plants, that are Dendrobium (DPS), Lycium barbarum (LBP), Ginseng (GPS), and Poria Cocos (PCP) were firstly combined with sodium alginate (SA) to construct microcapsules and improved the morphology, encapsulation efficiency, Biocompatibility and protective capability in drug loading. Diverse typical therapeutics, including VO₂@ZIF67 nanoparticles, small molecule drugs salvianolic acid B (SaB)/ginsenoside (Rg1), probiotic Bacillus bifidus, and biomacromolecules SDF-1 were wrapped into 1.5 % GPS-0.5 % SA model microcapsules, respectively. Better mobility and formability were significantly observed, and showed 75 % survival rate of probiotics in simulated gastric juice and around 99 % encapsulation efficiency which is higher than single 2 % SA microcapsules. The microcapsules also obtained a delayed release and a higher cell index for SDF-1, which indicated better stability, biocompatibility and protective effect than single 2 % SA microcapsules. This study provides a strategy in developing plant derived polysaccharides as novel materials for the construction and improvement of traditional microcapsules.

Site-Selective Coordination Assembly of Dynamic Metal-Phenolic Networks

Coordination states of metal‐organic materials are known to dictate their physicochemical properties and applications in various fields. However, understanding and controlling coordination sites in metal‐organic systems is challenging. Herein, we report the synthesis of site‐selective coordinated metal‐phenolic networks (MPNs) using flavonoids as coordination modulators. The site‐selective coordination was systematically investigated experimentally and computationally using ligands with one, two, and multiple different coordination sites. Tuning the multimodal Fe coordination with catechol, carbonyl, and hydroxyl groups within the MPNs enabled the facile engineering of diverse physicochemical properties including size, selective permeability (20–2000 kDa), and pH‐dependent degradability. This study expands our understanding of metal‐phenolic chemistry and provides new routes for the rational design of structurally tailorable coordination‐based materials.

One-step emulsification for controllable preparation of ethyl cellulose microcapsules and their sustained release performance

A simple and versatile strategy for controlled production of monodisperse ethyl cellulose (EC) microcapsules by a single-stage emulsification method has been developed. Monodisperse oil-in-water emulsions, obtained by a microfluidic device, are used as templates for preparing EC microcapsules. Oil-soluble ethyl acetate (EA) is miscible with water, so the interfacial mass transfer between EA and water occurs sufficiently, which leads to water molecules pass through the phase interface and diffuse into emulsion interior. Water molecules aggregate at the interface, and some merge into a large water drop in the central position of the emulsion. After evaporation of EA solvent, monodisperse EC microcapsules create large numbers of pits on the surface with a hollow structure. Curcumin is used as a model drug and embedded in the hollow structure. EC microcapsules have good, sustained drug release efficacy in a simulated intestinal environment, and the release process of EC microcapsules containing 6.14% drug-loaded capacity is fully consistent with the vitro drug release model. Such simple techniques for making EC microcapsules may open a window to the controlled preparation of other multifunctional microcapsules. Besides, it offers theoretical guidance for the study of EC microcapsules as drug carriers and expanding clinical application of curcumin.

Ultrasound-Responsive Aqueous Two-Phase Microcapsules for On-Demand Drug Release

Traditional implanted drug delivery systems cannot easily change their release profile in real time to respond to physiological changes. Here we present a microfluidic aqueous two-phase system to generate microcapsules that can release drugs on demand as triggered by focused ultrasound (FUS). The biphasic microcapsules are made of hydrogels with an outer phase of mixed molecular weight (MW) poly(ethylene glycol) diacrylate that mitigates premature payload release and an inner phase of high MW dextran with payload that breaks down in response to FUS. Compound release from microcapsules could be triggered as desired; 0.4 μg of payload was released across 16 on-demand steps over days. We detected broadband acoustic signals amidst low heating, suggesting inertial cavitation as a key mechanism for payload release. Overall, FUS-responsive microcapsules are a biocompatible and wirelessly triggerable structure for on-demand drug delivery over days to weeks.

Alginate/κ-carrageenan oral microcapsules loaded with Agaricus bisporus polysaccharides MH751906 for natural killer cells mediated colon cancer immunotherapy

The current study explores the effect of the extracted novel Mushroom polysaccharides and its formulation onto Alginate (Alg.)/kappa carrageenan microcapsules to exert immunotherapeutic effect upon activating gut resident natural killer cells (NK) against colon cancer. The extracted polysaccharides of Agaricus bisporus MH751906 was microcapsulated in Alg/κ-carrageenan microcapsules as an oral delivery system for colon cancer. The microcapsule is characterized by SEM, FTIR, Raman and TGA; and showed a superior acidic stability, controlled release, and thermal stability at high temperature with higher hydrogel swelling rate in colon-mimicking pH. Upon activation of human NK cells with microcapsules (^ANK cells), a significant increase in CD16⁺CD56⁺ NK cell populations were recorded. These activated NK cells showed 74.09% cytotoxic effects against human colon cancer Caco-2 cells where majority of cancer cell populations arrested at G0/G1 phase leading to apoptosis. The apoptotic molecular mechanism induced by ^ANK cells on Caco-2 treated cells is through down regulations of both BCL2 and TGF surviving genes and up regulation in IkappaB-α gene expression. Therefore, this novel polysaccharides-alginate/κ-carrageenan microcapsules can be used as an oral targeted delivery system for colon cancer immunotherapy.

Extraction kinetic model of polysaccharide from Codonopsis pilosula and the application of polysaccharide in wound healing

The crude polysaccharide (CPNP) of Codonopsis pilosula was obtained by hot-water extraction technology. The extraction kinetic model established according to Fick's first law of diffusion and related parameters of polysaccharide was studied. CPNP microcapsules were prepared by blending with sodium alginate, Ca2+ ions and crude CPNP. The quality control (Drug loading rate, embedding rate and release rate, etc) of CPNP microcapsules were analyzed by pharmacopeas standards. The structure feature of CPNP microcapsules also were determined with various methods. The wound healing ability of CPNP microcapsules loading with different concentration of CPNP was evaluated using the rat wound model. The activity of various enzymes and the expression levels of pro-inflammatory factors in the model skin tissue also were determined by enzyme linked immunosorbent assay (ELISA). Hematoxylin-eosin staining (HE), Masson, immunohistochemistry were used to investigate the external application effect of CPNP microcapsules on skin wound repair. The extraction kinetics of CPNP was established with the linear correlation coefficient (R2) of 0.83-0.93, implied that the extraction process was fitted well with the Fick's first law of diffusion. The CPNP has good compatibility with sodium alginate and Ca2+ ions by SEM and TEM observation, and the particle size of CPNP microcapsules was 21.25±2.84 μm with the good degradation rate, loading rate (61.59%) and encapsulation rate (55.99%), maximum swelling rate (397.380 ±25.321%). Compared with control group, the redness, and swelling, bleeding, infection, and exudate of the damaged skin decreased significantly after CPNP microcapsules treatment, and the CPNP microcapsules groups exhibited good wound healing function with less inflammatory cell infiltration. The pathological structure showed that in the CPNP microcapsules group, more newborn capillaries, complete skin structure, and relatively tight and orderly arrangement of collagen fibers were observed in the skin of rats. CPNP microcapsules could effectively inhibit the high expression of pro-inflammatory factors in damaged skin, and significantly increase the contents of related enzymes (GSH-Px, T-AOC, LPO) and collagen fibers. The relative expression levels of genes (VEGF and miRNA21) in the CPNP microcapsules group were higher than those in the model group and the negative group. The above results suggested that the CPNP microcapsules could controlled-release the CPNP to the wound surface, and then played a better role in antibacterial, anti-inflammatory and skin wound repair.