Porous microcapsules with tunable pore sizes provide easily controllable release and bioactivity

Polysaccharides and proteins-based bionanocomposites for microencapsulation of probiotics to improve stability and viability in the gastrointestinal tract: A review

Probiotics have recently received significant attention due to their various benefits, such as the modulation of gut flora, reduction of blood sugar and insulin resistance, prevention and treatment of digestive disorders, and strengthening of the immune system. One of the major issues concerning probiotics is the maintenance of their viability in the presence of digestive conditions and extended shelf life during storage. To address this concern, numerous techniques have been explored to achieve success. Among these methods, the microencapsulation of probiotics has been proposed as the most effective way to overcome this challenge. The combination of nanomaterials with biopolymer coating is considered a novel approach to improve its viability and effective delivery. The use of polysaccharides and proteins-based bionanocomposites for microencapsulation of probiotics has emerged as an efficient and promising approach for maintaining cell viability and targeted delivery. This review article aims to investigate the use of different bionanocomposites in microencapsulation of probiotics and their effect on cell survival in long-term storage and harsh conditions in the gastrointestinal tract.

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.

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.

Enhancing the Antioxidant Ability of Momordica grosvenorii Saponin to Resist Gastrointestinal Stresses via Microcapsules of Sodium Alginate and Chitosan and Its Application in Beverage

Momordica grosvenorii saponin (MGS), as a promising dietary supplement with remarkable biological properties, has poor stability under acidic conditions and thus hinders its application in functional foods. In this study, capsules of chitosan and sodium alginate were successfully prepared to enhance the stability of MGS. The optimized parameters for preparing MGS capsules were established. Sodium alginate of 20.8 mg/mL and triplication of MGS powder were added to chitosan of 4 mg/mL and calcium chloride of 10 mg/mL at a volume ratio of 3:1, stirring at 1000 r/min for 30 min to form the capsules. In this case, the fresh particles averaged 1687 μm with an encapsulation efficiency (EE) of 80.25% MGS. The capsule tolerated acidic environments better, and in vitro MGS could be controlled to release in a stimulated gastrointestinal tract system. The antioxidant activity and delayed release of MGS could be achieved by microencapsulation of chitosan/sodium alginate. Moreover, one drink containing 19 mg/mL MGS was successfully developed for the fruit.

Functional nanoemulsion and nanocomposite microparticles as an anticolorectal cancer and antimicrobial agent: applied in yogurt

Great concern for human health has led the food industry to focus on functional products. Microparticles based on nanoemulsions (M1) and nanocomposites (M2) were developed to deliver vital agents against colorectal cancer and microbial infection. The functional microparticles were prepared by coating extra virgin olive oil (EVOO), probiotics, and fig leaves extract with sodium alginate (SA) and whey protein concentrate (WPC) using the freeze drying technique. The antimicrobial, cytotoxic, apoptotic, encapsulation efficiency (EE %), release rate, and antioxidant activity were investigated. The yogurt was loaded with microparticles and evaluated microbiology, chemically, and sensory during storage. The results showed that the size of nanoemulsion and nanocomposite was between 476.1 and 517.7 nm, while the zeta potentials were −30.1 and −34.5 mV, respectively. M2 microparticles recorded the lowest IC50 values against human colorectal cancerous Caco-2 and HCT 116 cell lines: 1.10 μg/mL and 15.34 μg/mL, respectively. The inhibition zones were between 11 to 20 and 9 to 18 mm for M1 and M2, respectively. The highest EE% was 89.20% for EVOO and 91.34% for probiotics in M2 microparticles. The induction period of the EVOO from M1 and M2 microparticles was 15.37 h and 13.09 h, respectively. The antioxidant activity was between 78 and 65.8% for M1 and M2 microparticles, respectively. The probiotics in yogurt with microparticles were more than un-coated cells, and the taste of these samples was acceptable during storage. This study suggests that microencapsulation could be considered an interesting therapeutic tool when EVOO and probiotics are used in functional food.

Preparation and Characterization of Pendimethalin Microcapsules Based on Microfluidic Technology

Microencapsulation of pesticides is a promising attempt to reduce environmental pollution and prevent the active ingredients from the interference of external factors. In this paper, pendimethalin microcapsules were prepared by the interfacial polymerization of 4,4-methylenediphenyl diisocyanate (MDI) and ethylenediamine (EDA) based on microfluidic technology. Effects of the microchannel structure, reaction temperature, surfactant type, and fluid flow rates were investigated and evaluated. The results showed that pendimethalin microcapsules prepared under suitable conditions had a smooth surface, good monodispersity, a high encapsulation efficiency (96.7%), and excellent thermal stability. The size and morphology control of microcapsules were realized by adjusting the flow rates of the continuous phase and the hydrophilic monomer EDA aqueous solution. The release of pendimethalin had a sustained release characteristic that was closely related to the morphology of microcapsules. Compared with the pendimethalin emulsifiable concentrate, pendimethalin microcapsules exhibited outstanding herbicidal activity in the weed control experiments. Therefore, pendimethalin microcapsules with tunable properties were successfully obtained from the microfluidic device and showed great potential in agricultural applications.

Advances in Controlled-Release Pesticide Formulations with Improved Efficacy and Targetability

Pesticides are commonly used in modern agriculture and are important for global food security. However, postapplication losses due to degradation, photolysis, evaporation, leaching, surface runoff, and other processes may substantially reduce their efficacy. Controlled-release formulations can achieve the permeation-regulated transfer of an active ingredient from a reservoir to a target surface. Thus, they can maintain an active ingredient at a predetermined concentration for a specified period. This can reduce degradation and dissipation and other losses and has the potential to improve efficacy. Recent developments in controlled-release technology have adapted the concepts of intelligence and precision from the pharmaceutical industry. In this review, we present recent advances in the development of controlled-release formulations and discuss details of the preparation methods, material improvements, and application technologies.

Improving the efficacy against crop foliage disease by regulating fungicide adhesion on leaves with soft microcapsules

BACKGROUND

Increasing pesticide retention on crop leaves is a key approach for guaranteeing efficacy when products are applied to foliage. Evidently, the formulation plays an important role in this process. Microcapsules (MCs) are a promising formulation, but whether and how their adhesion to the leaf surface affects retention and efficacy is not well understood.

RESULTS

In this study, we found that the incorporation of polyethylene glycol (PEG) with different molecular weights into the MC shell affects the release profile of MCs and the contact area of these MCs to leaves by changing their softness. The cumulative release rates of pyraclostrobin (Pyr) MCs fabricated with PEG200, PEG400, PEG800 and PEG1500 were 80.61%, 90.98%, 94.07% and 97.40%, respectively. Scanning electron microscopy observations showed that the flexibility of the MCs increased with increasing PEG molecular weight. The median lethal concentration (LC₅₀ ) of the MCs with different PEG to the zebrafish were 12.10, 8.10, 3.90 and 1.46 mg L^-1 , respectively, which also indirectly reflected their release rate. Rainwater had less influence on the retention of the MCs prepared with PEG1500 than with the other PEG, which indicates a better adhesion to the target leave surfaces. MCs with the highest residual efficacy had better control efficacy on peanut leaf spot in field trials.

CONCLUSION

Overall, adding PEG with an appropriate molecular weight to the MC shell can regulate the structure of the MC shell to improve the affinity between the MCs and leaves, which further improves the utilization of pesticides and reduces the environmental risks of pesticides. © 2021 Society of Chemical Industry.

Inter-capsule fusion and capsule shell destruction using dynamic covalent polymers

Herein, capsule shells containing hindered urea bonds were prepared using interfacial polymerization in an oil-in-oil Pickering emulsion stabilized by functionalized graphene oxide nanosheets.

Lignin-Modified Electronegative Epoxy Resin Nanocarriers Effectively Deliver Pesticides against Plant Root-Knot Nematodes (Meloidogyne incognita)

It is highly desirable to fabricate a pesticide delivery system with excellent permeability to reduce the damage caused by root-knot nematodes in the soil. In this work, a novel electronegative pesticide nanocarrier was established by bonding anionic lignosulfonate with epoxy resin nanocarriers, which were loaded with abamectin (Aba). The results demonstrated that nanoparticles were negatively charged (-38.4 mV) spheres with an average size of 150 nm, and the encapsulation efficiency of nanocarriers for Aba was 93.4%. Polymer nanocarriers could prevent premature release of Aba and protect active ingredients from microbiological degradation. The adsorption strength of the soil to Aba loaded in nanocarriers was reduced by 6 to 10 times, so nanonematicides have remarkable soil mobility. Meanwhile, nanoparticles could easily penetrate the roots and nematodes. The application test confirmed that the control effect of this nanopesticide was 26-40% higher than that of the other agrochemicals. In consideration of its superior bioactivity and utilization rate, this pesticide delivery system has promising potential to control root-knot nematodes and improve the pesticide's utilization efficiency.

pH-Triggered Release of NaNO2 Corrosion Inhibitors from Novel Colophony Microcapsules in Simulated Concrete Pore Solution

Herein, pH-sensitive microcapsules containing NaNO₂ corrosion inhibitors for protection of steel reinforced concrete were synthesized via water-in-oil-in-water (W/O/W) double emulsion using colophony as the wall material. The average microcapsule size was 79.07 μm in diameter and exhibited a high encapsulation efficiency of 83.2%. Study of the release of corrosion inhibitors from microcapsules in deionized water (DI water, pH 6.8), carbonate/bicarbonate buffer solution (CBS, pH 9.1), and simulated concrete pore solution (SCPS, pH 12.6) demonstrates that the microcapsules are sensitive to pH and display higher release in alkaline media. This is the first study of colophony as an encapsulating agent for corrosion inhibitors. Furthermore, the alkaline pH-triggered release shows the suitability of its use in reinforced concrete systems. A wide thermal stability range was also found for the colophony microcapsules up to 100 °C. These high pH environments (CBS and SCPS) present pH values above the pK_a of colophony (7.2), thus triggering enhanced inhibitor release by the ionization and deprotonation of colophony shell. The higher release in CBS and SCPS is demonstrated by the increases of the corrosion inhibitor diffusion coefficient by an order of magnitude from 3.30 × 10^-17 m²/s in DI water up to 1.66 × 10^-16 m²/s for SCPS. The release performance indicates that the proposed approach can be used to encapsulate a variety of inhibitors for the protection of steel reinforcements. After immersion in different pH solutions, the corrosion potentials of a carbon steel substrate with microcapsules containing nitrite were more noble than when immersed without microcapsules and the corrosion current densities showed comparable values to free corrosion inhibitors. The formation of a passive ferric oxide layer was confirmed by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy.

Fabrication of abamectin-loaded mesoporous silica nanoparticles by emulsion-solvent evaporation to improve photolysis stability and extend insecticidal activity

Mesoporous silica nanoparticles (MSNs) can be designed to effectively load, protect, and control the release of pesticides. In this study, emulsion-solvent evaporation was used to fabricate abamectin-loaded MSNs. Our method could deliver abamectin in the process of MSN self-assembly, resulting in simple operation, short preparation period, and outstanding drug carrying capacity. The characteristics of abamectin-loaded MSNs, including morphology, loading content, stability against photolysis, controlled release behavior, and toxicological effect, were systematically investigated. Abamectin-loaded MSNs were successfully produced, having spherical shape, rough surface, uniform particle sizes, typically hollow structure, high loading efficiency (44.8%), excellent photodegradation-reducing ability, and controlled-release properties. The biological activity survey for abamectin-loaded MSNs showed excellent toxicological properties against Plutella xylostella larvae, and maintained biological activity until the 15th day, with 70% mortality of the target insect. The results of this study are beneficial for the development of a delivery system for the rational and effective usage of pesticides.

Active Encapsulation in Biocompatible Nanocapsules

Co-precipitation is generally refers to the co-precipitation of two solids and is widely used to prepare active-loaded nanoparticles. Here, it is demonstrated that liquid and solid can precipitate simultaneously to produce hierarchical core-shell nanocapsules that encapsulate an oil core in a polymer shell. During the co-precipitation process, the polymer preferentially deposits at the oil/water interface, wetting both the oil and water phases; the behavior is determined by the spreading coefficients and driven by the energy minimization. The technique is applicable to directly encapsulate various oil actives and avoid the use of toxic solvent or surfactant during the preparation process. The obtained core-shell nanocapsules harness the advantage of biocompatibility, precise control over the shell thickness, high loading capacity, high encapsulation efficiency, good dispersity in water, and improved stability against oxidation. The applications of the nanocapsules as delivery vehicles are demonstrated by the excellent performances of natural colorant and anti-cancer drug-loaded nanocapsules. The core-shell nanocapsules with a controlled hierarchical structure are, therefore, ideal carriers for practical applications in food, cosmetics, and drug delivery.

Generation of Ultra-Thin-Shell Microcapsules Using Osmolarity-Controlled Swelling Method

Microcapsules are attractive core-shell configurations for studies of controlled release, biomolecular sensing, artificial microbial environments, and spherical film buckling. However, the production of microcapsules with ultra-thin shells remains a challenge. Here we develop a simple and practical osmolarity-controlled swelling method for the mass production of monodisperse microcapsules with ultra-thin shells via water-in-oil-in-water (W/O/W) double-emulsion drops templating. The size and shell thickness of the double-emulsion drops are precisely tuned by changing the osmotic pressure between the inner cores and the suspending medium, indicating the practicability and effectiveness of this swelling method in tuning the shell thickness of double-emulsion drops and the resultant microcapsules. This method enables the production of microcapsules even with an ultra-thin shell less than hundreds of nanometers, which overcomes the difficulty in producing ultra-thin-shell microcapsules using the classic microfluidic emulsion technologies. In addition, the ultra-thin-shell microcapsules can maintain their intact spherical shape for up to 1 year without rupturing in our long-term observation. We believe that the osmolarity-controlled swelling method will be useful in generating ultra-thin-shell polydimethylsiloxane (PDMS) microcapsules for long-term encapsulation, and for thin film folding, buckling and rupturing investigation.

Fungicide Formulations Influence Their Control Efficacy by Mediating Physicochemical Properties of Spray Dilutions and Their Interaction with Target Leaves

In this study, three types of pyraclostrobin formulations (including emulsifiable concentrate (EC), suspension concentrate (SC), and microcapsules (MCs)) were used to control cucumber anthracnose. Pyraclostrobin EC had the highest inhibitory activity against Colletotrichum orbiculare in vitro. Much different from the bioactivity in vitro, pyraclostrobin MCs exhibited the highest control efficacy on cucumber anthracnose both in pot and field experiments. The physicochemical properties (particle size, surface tension) of the spray dilution, their interaction with target leaves (contact angle, adhesional tension, work of adhesion, retention, crystallization) and dissipation dynamic of the active ingredient were found to be highly potential factors that would significantly influence the control efficacy of pesticide formulations. Results showed that the control efficacies of different formulations of pyraclostrobin were determined mainly by the final behavior of the pesticides at the target interface, namely, the retention, crystallization, and dissipation dynamics of active ingredients. This study had revealed crucial factors that would influence the efficacy of different formulations of pyraclostrobin and thus could guide the rational and efficient use of different formulations of pesticides on target crops.

The Fabrication of Fragrance Microcapsules and Their Sustained and Broken Release Behavior

Their controlled release property is the most important feature of functional microcapsules and carriers. In this work, melamine resin shell fragrance microcapsules were fabricated in a non-ionic system, and their chemical structure, particle size, and morphology were analyzed. The sustained release property of the prepared microcapsules over 2400 h was studied with a weighing calculation method, and based on the fitting results, the release rate trend was consistent with the Peppas model (y = 100 - 2.30t^0.3213). Furthermore, the sustained and broken release behavior of the microcapsules in impregnated fabric samples were investigated for the first time by our proposed Solid Phase Microextraction-Gas Chromatography-Mass Spectrometer (SPME-GC-MS) method. The qualitative and quantitative analysis results showed that the middle and base note compositions were outstanding in the sustained release state, and the top note showed more advantages in the broken release state. In addition, it was found that the characteristic peak species and intensities of the sample finished with the microcapsules were more similar to pure essence oil than the sample finished by traditional methods, suggesting that the prepared microcapsules showed an excellent odor recovery and strength.

Tunable thermal, mechanical, and controlled-release properties of epoxy phenolic novolac resin microcapsules mediated by diamine crosslinkers

Diverse shell structures can endow microcapsules (MCs) with a variety of properties.

Easily Tunable Membrane Thickness of Microcapsules by Using a Coordination Assembly on the Liquid-Liquid Interface

A model solvent, 1,3,5-trimethylbenzene, was encapsulated using coordination assembly between metal ions and tannic acid to reveal the deposition of coordination complexes on the liquid-liquid interface. The deposition was confirmed by zeta potential, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy and transmission electron microscopy were integrated to characterize the microcapsules (MCs). According to atomic force microscopy height analysis, membrane thickness of the MCs increased linearly with sequential deposition. For MCs prepared using the Fe3+-TA system, the average membrane thicknesses of MCs prepared with 2, 4, 6, and 8 deposition cycles were determined as 31.3 ± 4.6, 92.4 ± 15.0, 175.4 ± 22.1, and 254.8 ± 24.0 nm, respectively. Dissolution test showed that the release profiles of all the four tested MCs followed Higuchi kinetics. Membrane thicknesses of MCs prepared using the Ca2+-TA system were much smaller. We can easily tune the membrane thickness of the MCs by adjusting metal ions or deposition cycles according to the application requirements. The convenient tunability of the membrane thickness can enable an extensive use of this coordination assembly strategy in a broad range of applications.