The treatment of oily wastewater by thermo-responsive calcium alginate capsules immobilized Pseudomonas aeruginosa.

A microfluidic strategy of smart calcium alginate (CA) capsules is presented to immobilize Pseudomonas aeruginosa to treat oil slicks effectively. The capsule wall is embedded with poly (N-isopropyl acrylamide) sub-microspheres as thermo-responsive switches. CA capsules, with a diameter of 3.26 mm and a thin wall thickness about 12.8 µm, have satisfying monodispersity, cavity structure, and dense surface structures. The capsules possess excellent encapsulation of bacteria, which are fixed in a restricted space and become more aggregated. It overcomes the disadvantages of a long fermentation production cycle, easy loss of bacteria, and susceptibility to shear effect. The smart CA capsules immobilized with bacteria treat model wastewater containing soybean oil or diesel and display favorable fermentation ability. The capsules can effectively treat oil slicks with high concentration, and it is an economical way for processing oily wastewater. PRACTITIONER POINTS: A thermo-responsive calcium alginate capsule was prepared by microfluidic strategy. Pseudomonas aeruginosa is environmentally friendly in treating oil slicks. The capsules, immobilized bacteria, treat oil slicks effectively. This study provides an economical way for processing different oily water.

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.

Thermo-responsive monodisperse core-shell microspheres with PNIPAM core and biocompatible porous ethyl cellulose shell embedded with PNIPAM gates.

Monodisperse microspheres composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) core and biocompatible porous ethyl cellulose (EC) shell embedded with PNIPAM gates have been successfully prepared by microfluidic emulsification, solvent evaporation and free radical polymerization. Attributing to the coating of EC shell, the mechanical strength and biocompatibility of the core-shell microsphere are much better than those of the PNIPAM core itself. Fourier transform infrared (FT-IR) spectrometer and scanning electron microscopy (SEM) are employed to examine chemical compositions and microstructures of prepared microparticles. By the cooperative action of EC shell with PNIPAM gates and PNIPAM core, the proposed core-shell microspheres exhibit satisfactory thermo-responsive controlled release behaviors of model drug molecules rhodamine B (Rd B) and VB12. At temperatures above the volume phase transition temperature (VPTT) of PNIPAM, the release rate of solute molecules is much faster than that at temperatures below the VPTT. The controlled factor of the prepared core-shell microspheres for VB12 release reaches to as high as 11.7. The proposed microspheres are highly attractive for controlled drug delivery.

Monodisperse microspheres with poly(N-isopropylacrylamide) core and poly(2-hydroxyethyl methacrylate) shell.

Monodisperse core-shell microspheres, composed of poly(N-isopropylacrylamide) (PNIPAM) core with thermo-responsive swelling/shrinking function and biocompatible poly(2-hydroxyethyl methacrylate) (PHEMA) shell with "open/close" switching function, have been successfully prepared by microfluidic emulsification, free-radical polymerization and atom transfer radical polymerization (ATRP). The effects of grafting time for the ATRP and polyvinyl alcohol (PVA) concentration inside the core on the thermo-responsive behavior of core-shell microspheres are investigated. For the core-shell microspheres prepared with PVA concentration of 2% (w/v) and grafting time of 2 h, the PNIPAM core is in the shrunken state and the solid PHEMA shell protect the whole PNIPAM core at temperatures above the volume phase transition temperature (VPTT); as environmental temperature decreases below the VPTT, the PNIPAM core swells dramatically and the PHEMA shell ruptures a large area. The thermo-responsive function of the core-shell microspheres is reversible and the appearance/recovery of PHEMA shell crack exhibits an "open/close" switching function. Such core-shell microspheres are highly attractive for developing drug delivery systems with both biocompatible and thermo-responsive characteristics.

Effects of surface wettability and roughness of microchannel on flow behaviors of thermo-responsive microspheres therein during the phase transition.

The flow characteristics of monodisperse thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) microspheres during the phase transition in microchannels with different surface wettabilities and roughnesses are investigated systematically. Glass microchannels are modified by hydroxylation treatment to achieve hydrophilic surface, by self-assembly of chlorotrimethylsilane to realize hydrophobic surface, and by coating with silica nanoparticles to generate rough surface. The phase transition of PNIPAM microspheres in microchannels is induced by local heating. The results show that the surface wettability and roughness of microchannel significantly affect the flow behaviors of PNIPAM microspheres during the phase transition. It is much easier for the PNIPAM microspheres in microchannel with hydrophobic surface to stop right after the phase transition than those in microchannel with hydrophilic surface, and it is also much easier for the PNIPAM microspheres in microchannel with rough surface to stop right after the phase transition than those in microchannel with smooth surface. These results indicate that hydrophobic and rough surface properties of the microchannel can enhance the site-specific targeting of PNIPAM microspheres caused by the phase transition. The results in this study provide valuable information for the application of thermo-responsive drug carriers in site-specific targeting therapy.