Acetalized starch-based nanoparticles stabilized acid-sensitive Pickering emulsion as a potential antitumor drug carrier.

Pickering emulsions are attracting increased attention owing to their therapeutic applications. However, the slow-release property of Pickering emulsions and the in vivo solid particle accumulation caused by the solid particle stabilizer film limit their applications in therapeutic delivery. In this study, drug-loaded, acid-sensitive Pickering emulsions were prepared using acetal-modified starch-based nanoparticles as stabilizers. The acetalized starch-based nanoparticles (Ace-SNPs) not only act as a solid-particle emulsifier to stabilize Pickering emulsions but also exhibit acid sensitivity and degradability, conducive to the destabilization of Pickering emulsions to release the drug and reduce the effect of particle accumulation in an acidic therapeutic environment. In vitro drug release profiles show that 50 % of curcumin was released in 12 h in an acidic medium (pH 5.4), whereas only 14 % of curcumin was released in 12 h at higher pH (7.4), indicating that the Ace-SNP stabilized Pickering emulsion possess good acid-responsive release characteristics in acidic environments. Moreover, acetalized starch-based nanoparticles and their degradation products showed good biocompatibility, and the resulting curcumin-loaded Pickering emulsions exhibited significant anticancer activity. These features suggest that the acetalized starch-based nanoparticle-stabilized Pickering emulsion has the potential for application as an antitumor drug carrier to enhance therapeutic effects.

Facile Fabrication of Starch-Based Microrods by Shear-Assisted Antisolvent-Induced Nanoprecipitation and Solidification.

Rod-like particles have attracted increasing attention because of their unique shape-dependent properties, which enable their superior performance compared to their isotropic counterparts. Thus, rod-like particles have potential applications in many fields, especially in biomedicine. However, the fabrication of uniform rod-like particles is challenging because of the principle of interfacial energy minimization. Herein, we present a facile, rapid, and cost-effective strategy for preparing starch-based microrods with tunable aspect ratios via shear-assisted antisolvent-induced nanoprecipitation and solidification. The preformed spherical particles swollen by the mixed solvent were elongated by the shear force and solidified in rod-like shape by antisolvent induction. The resulting starch-based microrods can encapsulate hydrophobic active substances and be modified with functional groups, indicating their potential applications as drug carriers and biologically active materials. The formation mechanism of the starch-based microrods discovered in this study provides a new perspective on the fabrication of rod-like polymer particles.

Application and mechanism of ultrasonic static mixer in heavy oil viscosity reduction.

In the present study, heavy oil viscosity reduction in Daqing oil field was investigated by using an ultrasonic static mixer. The influence of the ultrasonic power on the viscosity reduction rate was investigated and the optimal technological conditions were determined for the ultrasonic treatment. The mechanism for ultrasonic viscosity reduction was analyzed. The flow characteristics of heavy oil in the mixer under the effect of cavitation were investigated using numerical modeling, and energy consumptions were calculated during the ultrasonic treatment and vis-breaking processes. The experimental results indicated that the ultrasonic power made the largest impact on the viscosity reduction rate, followed by the reaction time and temperature. The highest viscosity reduction rate was 57.34%. Vacuole was migrated from the axis to the wall along the fluid, accelerating the two-phase transmission and enhancing the radial flow of the fluid, which significantly improved the ultrasonic viscosity reduction. Compared to the vis-breaking process, the energy consumption of ultrasonic treatment process was 43.03% lower when dealing with the same quality heavy oil. The optimal process conditions were found to be as follows: ultrasonic power of 1.8kW, reaction time of 45min and reaction temperature of 360°C. The dissociation of the molecules of heavy oil after ultrasonication has been checked. After being kept at room temperature 12days, some light components were produced by the cavitation cracking, so the viscosity of the residual oil could not return to that of the original residual oil, which meant that the "cage effect" was not reformed.

A novel multi-responsive polyampholyte composite hydrogel with excellent mechanical strength and rapid shrinking rate.

Series of hydrophilic core-shell microgels with cross-linked poly(N-isopropylacrylamide) (PNIPAAm) as core and poly(vinyl amine) (PVAm) as shell are synthesized via surfactant-free emulsion polymerization. Then, the microgels are treated with a small amount of potassium persulfate (KPS) to generate free radicals on the amine nitrogens of PVAm, which subsequently initiate the graft copolymerization of acrylic acid (AA), acryloyloxyethyl trimethyl ammonium chloride (DAC), and acrylamide (AAm) onto microgels to prepare multi-responsive composite hydrogels. The composite hydrogels consist of cross-linked ungrafted polyampholyte chains as the first network and microgels with grafted polyampholyte chains as graft point and second network and show surprising mechanical strength and rapid response rate. The investigation shows the compress strength of composite hydrogels is up to 17-30 MPa, which is 60-100 times higher than that of the hydrogel matrix. The composite hydrogel shows reversible switch of transmittance when traveling the lowest critical temperature (LCST) of microgels. When the composite hydrogel swollen in pH 2.86 solution at ambient condition is immersed into the pH 7.00 solution at 45 °C, a rapid dynamic shrinking can be observed. And the character time (τ) of shrinking dynamic of composite hydrogel is 251.9 min, which is less than that of hydrogel matrix (τ=2273.7 min).