This article reports a smart water-based ferrofluid that can transform from stable state to unstable state for separating the contained magnetic nanoparticles after use. The ferrofluid is synthesized by preparing polyethylenimine modified Fe 3 O 4 nanoparticles via a one-pot method, and then improved by acidification treatment and ultracentrifugation-based washing. The resultant ferrofluid and intermediate products have been systematically characterized, verifying that the ferrofluid possesses superparamagnetism, high saturation magnetization as well as strong colloidal stability, and the magnetic nanoparticles contained in the ferrofluid have small aggregation size, strong electropositivity and high saturation magnetization. It has been confirmed that the acidification treatment and ultracentrifugation-based washing greatly activate the positive charge and reduce the aggregation size of polyethylenimine modified Fe 3 O 4 nanoparticles, which is the key to our successful synthesis of this new type of ferrofluid. Furthermore, the adsorption behavior of the ferrofluid on the anionic Ponceau S dye has been systematically investigated, demonstrating that the ferrofluid can adsorb anionic Ponceau S dye in a short time (<5 min) with a maximum adsorption capacity of 140.26 mg/g. The experimental data show that the adsorption kinetics follows the pseudo-second-order mode and the Langmuir isotherm model is applicable to describe the adsorption processes . Importantly, the magnetic nanoparticles in the ferrofluid can be easy to separate from solution after adsorbing anionic Ponceau S dye, preventing secondary pollution and showing great potential in wastewater treatment .
Two soy protein 11S fractions with different surface sulfhydryl contents were prepared. Utilizing analytical ultracentrifugation, the effects of storage time and hydrogen peroxide at different concentrations (0.5—100 mmol/L) on the two 11S fractions were investigated. Results show that after removing 2-mercaptoethanol (2-ME) by size exclusion chromatography, the 11S fraction with high surface sulfhydryl content (2.0 mol sulfhydryl/mol 11S) progressively formed 15S and 21S in dilute solutions during storage at 4 °C for 82 days. While, the 11S fraction with low surface sulfhydryl content (0.2 mol sulfhydryl/mol 11S) was stable under the same condition. Moreover, after treating the 11S with high surface sulfhydryl content with 1 mmol/L H 2 O 2 , the weight percentage of 15S reached the maximum value of 20%. The 15S induced by air and H 2 O 2 could be totally converted to 11S with the addition of 10 mmol/L 2-ME, which could be attributed to that the disulfide bond linking two 11S molecules is on the surface of the 15S and easily accessible to the reducing agent 2-ME. This study helps us to deeply understand the formation mechanism of 15S and the stability of 11S.
Functional materials with good biocompatibility have been widely used in the study of genomics, proteomics and disease diagnosis, which has improved the progress of life science. In this paper, the material not only exhibited a strong affinity to the phosphate groups on the exosomal membrane due to the coexistence of Zr–O clusters and Ti 4+ , but also owned great hydrophilicity to reduce non-specific adsorption of contaminated proteins, achieving the separation and purification of exosomes from complex biosamples. The model exosomes extracted by ultracentrifugation (UC) were used to evaluate the feasibility of Fe 3 O 4 @UiO-66-NH 2 @PA-Ti 4+ capturing exosomes. The process of Fe 3 O 4 @UiO-66-NH 2 @PA-Ti 4+ capturing exosomes was simple to operate with a high recovery rate (97.3%) within a short time (5 min). Then Fe 3 O 4 @UiO-66-NH 2 @PA-Ti 4+ was further applied to capture exosomes in media and urine followed by the downstream proteomics analysis. 348 and 284 exosomal proteins were identified for cell medium and urine, respectively. This work shows great potential of the material for subsequent function research of disease-related exosomes by separating exosomes rapidly and efficiently.
危险品化学品经营许可证（带存储）