Controlled release of a microencapsulated arduous semi-hydrophobic active from coatings: Superhydrophilic polyelectrolyte shells as globally rate-determining barriers

Eco-Friendly Starch Composite Supramolecular Alginate–Ca2+ Hydrogel as Controlled-Release P Fertilizer with Low Responsiveness to Multiple Environmental Stimuli

Environmentally friendly fertilizers (EFFs) have been developed to improve fertilizer efficiency and minimize adverse environmental impacts, but their release behavior under various environmental conditions has been less explored. Using phosphorus (P) in the form of phosphate as a model nutrient, we present a simple method for preparing EFFs based on incorporating the nutrient into polysaccharide supramolecular hydrogels using Cassava starch in the Ca2+-induced cross-link gelation of alginate. The optimal conditions for creating these starch-regulated phosphate hydrogel beads (s-PHBs) were determined, and their release characteristics were initially evaluated in deionized water and then under various environmental stimuli, including pH, temperature, ionic strength, and water hardness. We found that incorporating a starch composite in s-PHBs at pH = 5 resulted in a rough but rigid surface and improved their physical and thermal stability, compared with phosphate hydrogel beads without starch (PHBs), due to the dense hydrogen bonding-supramolecular networks. Additionally, the s-PHBs showed controlled phosphate-release kinetics, following a parabolic diffusion with reduced initial burst effects. Importantly, the developed s-PHBs exhibited a promising low responsiveness to environmental stimuli for phosphate release even under extreme conditions and when tested in rice field water samples, suggesting their potential as a universally effective option for large-scale agricultural activities and potential value for commercial production.

Fabrication of magnetic-responsive controlled-release herbicide by a palygorskite-based nanocomposite

In this work, a type of magnetic-responsive controlled-release herbicide (MCRH) was developed using a nanocomposite including palygorskite (Pal), ferroferric oxide (Fe₃O₄), glyphosate (Gly), and amino silicon oil (ASO). In this system, Pal with the structure of micro/nanonetworks can bind a large quantity of Gly and Fe₃O₄. The movement of Fe₃O₄ particles can be driven by a magnetic field to ensure the controlled release of pesticides. Gly, which is a type of nonselective herbicide, is widely used for weed control. In addition, ASO was selected as the coating agent to prevent Gly from rapidly releasing. In this work, the effects of the magnetic field, temperature, and coexisting ions on the release ratio of pesticides were investigated, and the results suggest that MCRH could effectively improve the utilization efficiency (UE) of Gly. In addition, zebrafish experiments indicate that MCRH has better biosafety than Gly.

Development of leaf-adhesive pesticide nanocapsules with pH-responsive release to enhance retention time on crop leaves and improve utilization efficiency

Pesticides play a very important role in pest control and plant protection. However, they can be limited by a tendency to cause ecological system damage due to significant losses into the environment. To increase pesticide utilization efficiency, we developed highly leaf-adhesive avermectin nanocapsules (Av-pH-cat@CS) with pH-responsive controlled release properties. The Av-pH-cat@CS nanocapsules displayed good thermal stability and photostability in response to UV light irradiation. The Av-pH-cat@CS nanocapsules could be disrupted at low pH and they exhibited excellent controlled release in response to pH, which improved the release of avermectins. In addition, the Av-pH-cat@CS nanocapsules were highly adhesive to crop leaves as a result of strong hydrogen bonding, which prolonged the retention time on crop leaves. The Av-pH-cat@CS nanocapsules with pH-responsive release and strong leaf adhesion improved the control efficacy and enhanced the utilization efficiency. Our findings offer a promising approach to prolonging pesticide duration on crop leaves and improving the utilization efficiency.

Electrically controllable cargo delivery with dextran-rich droplets

The controllable delivery of cargo is of great importance in many areas, ranging from medicine and materials science to food and cosmetic industries. To fulfil the requirements in different areas, the development of new methods for cargo delivery in a controllable manner is always essential. A novel technique of cargo delivery controlled by electric pulse was developed in this paper. In an aqueous two-phase system, the dextran-rich droplets were fabricated as droplet carriers in a continuous polyethylene glycol-rich phase. The loading and releasing of model cargos (polystyrene particles) across the surface of the droplet carriers under electric pulses were demonstrated in microfluidic chips. By controlling the amplitude of the applied electric pulses, the cargos with designed sizes were sorted and loaded into the droplet carriers; hence, the targeted delivery of cargos by size can be achieved. The exchange of cargos between droplet carriers under reversed electric pulses was also investigated, and the results indicated the flexibility of this method in cargo delivery. Moreover, possible application of this method to biological cargos was demonstrated by controlling the loading and releasing of yeast cells under electric pulses. With the advantages of easy operation and fast response, this approach provides a novel route for controllable cargo delivery with droplets.

The preparation of prochloraz pH-responsive nanocapsules by the Pickering emulsion polymerization method and the study of their performance

In this work, prochloraz pH-responsive nanocapsules were developed by the Pickering emulsion polymerization method with isophorone diisocyanate (IPDI) as the reaction monomer and nano Fe₃O₄ particle-branched polyethyleneimine (PEI) as the reaction monomer and surfactant. The physical and chemical properties and sustained release properties were determined by a transmission electron microscope (TEM), field emission transmission electron microscope (FETEM), atomic force microscope (AFM), laser particle size analyzer, Fourier transform infrared spectrometer, and contact angle tester. The results indicated that the prochloraz nanocapsules were spherical, the average particle size was about 100 nm, and the encapsulation efficiency and loading rates were 86% and 30%, respectively. The nanocapsules tended to expand in acidic solutions, and this promoted the release of prochloraz more quickly, which could be verified by the biological test of anthrax. At the same time, the prochloraz nanocapsules can protect the pesticide from sunlight. Therefore, this work provides a promising approach to improve the utilization efficiency and prolong the duration of pesticides, which might have a huge potential application prospect.

In this work, prochloraz pH-responsive nanocapsules were developed by the Pickering emulsion polymerization method with isophorone diisocyanate (IPDI) and nano Fe₃O₄ particle-branched polyethyleneimine (PEI).

Bacterial self-defense antibiotics release from organic-inorganic hybrid multilayer films for long-term anti-adhesion and biofilm inhibition properties

Implant-associated bacterial infections pose serious medical and financial issues due to the colonization and proliferation of pathogens on the surface of the implant. The as-prepared traditional antibacterial surfaces can neither resist bacterial adhesion nor inhibit the development of biofilm over the long term. Herein, novel (montmorillonite/poly-l-lysine-gentamicin sulfate)8 ((MMT/PLL-GS)8) organic-inorganic hybrid multilayer films were developed to combine enzymatic degradation PLL for on-demand self-defense antibiotics release. Small molecule GS was loaded into the multilayer films during self-assembly and the multilayer films showed pH-dependent and linear growth behavior. The chymotrypsin- (CMS) and bacterial infections-responsive film degradation led to the peeling of the films and GS release. Enzyme-responsive GS release exhibited CMS concentration dependence as measured by the size of the inhibition zone and SEM images. Notably, the obtained antibacterial films showed highly efficient bactericidal activity which killed more than 99.9% of S. aureus in 12 h. Even after 3 d of incubation in S. aureus, E. coli or S. epidermidis solutions, the multilayer films exhibited inhibition zones of more than 1.5 mm in size. Both in vitro and in vivo antibacterial tests indicated good cell compatibility, and anti-inflammatory, and long-term bacterial anti-adhesion and biofilm inhibition properties.

Bacterial infection microenvironment-responsive enzymatically degradable multilayer films for multifunctional antibacterial properties

The adhesion of bacteria is one of the most important stages in biofilm formation and bacterial infection. Once bacteria have adhered to a biomaterial surface, it is hard to eliminate them, and bacterial growth and infection are inevitable. In the current study, we have designed and constructed enzymatically degradable (hyaluronic acid/chitosan)n-(hyaluronic acid/polylysine)n ((HA/CHI)n-(HA/PLL)n) composite multilayer films via a layer-by-layer self-assembly method. Spectroscopic ellipsometry and scanning electron microscopy cross section measurements showed the exponential growth behavior of (HA/CHI)10-(HA/PLL)10 multilayer films (∼2 μm). The increased secretion of hyaluronidase and chymotrypsin in the bacterial infection microenvironment led to the fast degradation of the outer (PLL/HA)n multilayer films in the first 24 h. Enzymatic degradation of the multilayer films efficiently reduced the adhesion of both Staphylococcus aureus and Escherichia coli (>99%). Bacterial live/dead staining demonstrated the bactericidal action of the remaining bottom (CHI/HA)n multilayer films against the two kinds of bacteria. In vivo subcutaneous tests on New Zealand white rabbits, wound appearance and histopathology analysis showed that the implantation of composite multilayer film-modified PDMS promoted wound healing and the materials demonstrated a self-defense antibacterial effect. The material demonstrated both anti-adhesive and bactericidal properties and could be used to modify biomedical implants.

Formation of titanium dioxide core-shell microcapsules through a binary-phase spray technique

Core-shell microcapsules consisting of a titanium dioxide shell and a hydrophobic solvent core have been prepared with diameters of a few micrometers and a narrow size distribution using a simple and fast airbrush technique. These microcapsules were prepared at room temperature in a single-step process in which an oil with a dissolved titanium alkoxide precursor was forced together with an aqueous solution, containing a surface-active polymer, through a narrow spray nozzle using a nitrogen gas propellant. Several different parameters of chemical, physical, and processing origin were investigated to find an optimal recipe. Two different alkanes, one ketone, and four alcohols were tested and evaluated as core materials, alone or together with the antifungal biocide 2-n-octyl-4-isothiazolin-3-one (OIT). Long-chain alcohols were found suitable as core oil due to their low solubility in water and surface activity. The addition of the surface-active polymers in the water phase was important in aiding the formation and stabilization of the titanium dioxide shell. An impressive loading of 50 wt% of the semi-hydrophobic OIT was possible to encapsulate using this simple and applicable procedure.