Heterogeneous Fenton oxidation of 2,4-dichlorophenol catalyzed by PEGylated nanoscale zero-valent iron supported by biochar.

The excessive use of herbicides and fungicides containing 2,4-dichlorophenol (2,4-DCP) has led to serious environmental water pollution; 2,4-DCP is chemically stable and difficult to be degraded effectively by biological and physical methods. And the degradation of 2,4-DCP using advanced oxidation techniques has been a hot topic. Biochar, polyethylene glycol, ferrous sulfate, and sodium borohydride were used to synthesize the heterogeneous catalyst PEGylated nanoscale zero-valent iron supported by biochar (PEG-nZVI@BC). The catalyst was characterized using scanning electron microscope (SEM) and other means to determine its physicochemical properties. Catalytic performance and mechanism of this catalyst with hydrogen peroxide for the oxidation of 2,4-DCP were investigated. The results showed that PEG-nZVI@BC had good dispersibility, stability, and inoxidizability; the degradation efficiency of 50 mg/L 2,4-DCP by PEG-nZVI@BC/H2O2 system 92.94%, 1.68 times higher than that of nZVI/H2O2 system; there are both free radical and non-free radical pathways in PEG-nZVI@BC/H2O2 system; the degradation process of 2,4-DCP includes hydroxylation, dechlorination, and ring-opening. Overall, PEG-nZVI@BC is a promising heterogeneous catalyst for the degradation of 2,4-DCP.

Smart Asymmetric Vesicles with Triggered Availability of Inner Cell-Penetrating Shells for Specific Intracellular Drug Delivery.

Smart nanocarriers attract considerable interest in the filed of precision nanomedicine. Dynamic control of the interaction between nanocarriers and cells offers the feasibility that in situ activates cellular internalization at the targeting sites. Herein, we demonstrate a novel class of enzyme-responsive asymmetric polymeric vesicles self-assembled from matrix metalloproteinase (MMP)-cleavable peptide-linked triblock copolymer, poly(ethylene glycol)-GPLGVRG-b-poly(ε-caprolactone)-b-poly(3-guanidinopropyl methacrylamide) (PEG-GPLGVRG-PCL-PGPMA), in which the cell-penetrating PGPMA segments asymmetrically distribute in the outer and inner shells with fractions of 9% and 91%, respectively. Upon treatment with MMP-2 to cleave the stealthy PEG shell, the vesicles undergo morphological transformation into fused multicavity vesicles and small nanoparticles, accompanied by redistribution of PGPMA segments with 76% exposed to the outside. The vesicles after dePEGylation show significantly increased cellular internalization efficiency (∼10 times) as compared to the original ones due to the triggered availability of cell-penetrating shells. The vesicles loading hydrophobic anticancer drug paclitaxel (PTX) in the membrane exhibit significantly enhanced cytotoxicity against MMP-overexpressing HT1080 cells and multicellular spheroids. The proposed vesicular system can serve as a smart nanoplatform for in situ activating intracellular drug delivery in MMP-enriched tumors.