Few natural, biocompatible, and inexpensive emulsifiers are available because such emulsifiers must satisfy severe requirements, be produced synthetically rather than naturally, be nontoxic, and require minimal effort to produce. Therefore, the synthesis of food-grade and biocompatible nanoparticles as an alternative to surfactants has recently received attention in the industry. However, many previous efforts involved chemical modification of materials or the introduction of secondary cocomponents for emulsion formation. To achieve the goal of simple preparation, we consider here chitosan nanoparticles to prepare Pickering emulsions of food-grade oil through the control of pH, without further chemical modification or extra additives. A mild process can prepare nanoparticles from chitosan by simply increasing the pH from 3.0 to 6.0. The results showed that the average radius of chitosan at pH 6.0 was 170 nm, while large aggregates were formed at pH 6.5. These nanoparticles were utilized to prepare the Pickering emulsion. The average size of emulsion droplets decreased upon increasing the pH from 3.0 to 6.0. Moreover, Pickering emulsions at different oil fractions and nanoparticle concentrations were stable and showed a low creaming index for 45 days. The emulsions were stable against coalescence and flocculation and behaved rheologically as gel-like, shear-thinning fluids (G′ > G″). Pickering emulsion prevents the growth of the microorganism (Staphylococcus aureus) at different pH values and chitosan concentrations. These results demonstrate that chitosan nanoparticles could be a cost-effective and biocompatible emulsifier for the food or pharmaceutical industry for encapsulation and bioactive compounds, and Pickering emulsions have promising antibacterial effects for further applications.

Nanosized organosilica particles with tunable morphology are of great interest for versatile applications because of their enhanced properties. However, it is still a great challenge to control the morphology during fabrication of organosilica nanoparticles (NPs). In this study, a facile approach based on flash nanoprecipitation (FNP) technique is presented, which achieves an efficient fabrication of organosilica NPs with controllable morphology by utilizing an amphiphilic block copolymer poly(2-(dimethylamino)ethylmethylacrylate-b-poly(ε-caprolactone) (PDMAEMA-b-PCL) as the stabilizer. Such a preparation process is performed in a multi-inlet vortex mixer that enables an intense mixing of the silicon precursor with the aqueous solution of a catalyst at an ultrashort time scale, leading to the formation of numerous tiny reaction droplets stabilized by PDMAEMA-b-PCL, followed by the basic-catalyzed hydrolytic condensation. Interestingly, by controlling the composition and mixing parameter of feeding streams involved in the FNP process, golf ball-like, cubic, bowl-like, and hollow organosilica NPs can be easily obtained. The resultant NPs show a narrow size distribution and are expected to find potential applications in various fields, such as nanomedicine, nanocatalysts, and adsorption separation.

As one of the effective broad-spectrum antimicrobial and anti-inflammatory drugs, tilmicosin (TIM) is applied extensively in a wide range of veterinary treatments. However, the low bioavailability typically leads to overuse of TIM in practical applications, which can cause residual accumulation in the environment and contamination of foodstuffs. Here, we report a precipitation method that allows us to prepare TIM-loaded poly(methyl methacrylate- co -methacrylic acid) (P(MMA- co -MAA)) nanoparticles. Specifically, TIM and biocompatible P(MMA- co -MAA) are dissolved in methanol and then water is introduced as an antisolvent, which triggers the co-precipitation and leads to well-controlled nanoparticles. Depending on the drug/polymer mass ratio and the total concentration of drug and polymer, the formed nanoparticles display a tunable radius from 27 to 80 nm with a narrow size distribution, a high drug loading content, and a controlled release of TIM. The encapsulation does not interrupt the antibacterial function of TIM while reducing its cytotoxicity enormously. Moreover, the formed nanoparticles could be dried to powder through freeze-drying, and the redispersion of the particles hardly disturbs the particle size, size distribution, and drug loading content. Our study developed a facile and robust precipitation method for the controlled construction of TIM-loaded polymeric nanoparticles with tunable properties and functions, as well as improved biocompatibility, which shall improve the bioavailability of TIM and enhance the practical applications.