Microplastics-sorbed phenanthrene and its derivatives are highly bioaccessible and may induce human cancer risks.

Microplastics (MPs) are ubiquitous in environmental media and human diets and can enrich organic contaminants, including polycyclic aromatic hydrocarbons (PAHs) and their derivatives. The bioaccessibilities and triggering cancer risks of MP-sorbed PAHs and PAH derivatives are closely linked with human health, which, however, were rarely focused on. This study explored the sorption behaviors of phenanthrene (PHE) and PHE derivatives on polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs, and assessed their bioaccessibilities in gastrointestinal fluids as well as their inducing human cancer risks. PE MPs harbored the highest sorption capacity, secondly the PP MPs, then the PS ones. Sorption of PHE and PHE derivatives on MPs was positively correlated with their hydrophobicities. The bioaccessibilities of sorbed PHE and PHE derivatives could reach 53.59 %±0.46 %-90.28 %±0.92 % in gastrointestinal fluids and 81.34 %±0.77 %-98.72 %±1.44 % in gastrointestinal fluids with the addition of Tenax (more close to the bioavailability). The hydrophobicities also controlled the bioaccessibilities of PHE and PHE derivatives in gastric fluids, and those in intestinal fluids with Tenax for PS MPs. The incremental lifetime cancer risk (ILCR) values for PHE, PHE-Cl, and PHE-NO2 on MPs at tested concentrations were all higher than the USEPA-suggested safety limit (10-6), and most of them were even higher than 10-4, which thus indicates serious cancer risks. This study promoted our understanding of the potential health threats posed by organic pollutant-bearing MPs in the environment.

Non-covalent binding interaction between phthalic acid esters and DNA.

The interaction of phthalic acid esters (PAEs) with DNA is known to be responsible for the disruption of endocrine functions and the teratogenic and carcinogenic effects. However, the binding strength and mechanism of this important process has often been neglected. Here, we confirmed the binding interaction between PAEs and DNA via fluorescence titration quenching experiment. The linear fitting curve proved that PAEs could bind to DNA, and the binding constants (KA) were 4.11 × 105, 1.04 × 105, 7.60 × 104, 1.99 × 104, and 1.42 × 103 L/mol for diethyl phthalate (DEP), bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), dimethyl phthalate (DMP), and benzyl butyl phthalate (BBP), respectively. DNA melting point, UV-vis spectra and Fourier transform infrared spectroscopy (FTIR) analyses revealed that PAEs interact predominantly with thymines in the DNA minor groove. Quantum chemical calculations showed that hydrogen bonding and van der Waals force formation between PAEs and DNA bases dominated the binding interaction. However, PAEs-DNA binding did not induce any DNA conformation change since the circular dichroism and FTIR spectra of B-DNA were not change. The electrostatic surface potential (ESP) might act an important role in PAEs-DNA binding interaction. This work will broaden our understanding of the interaction between PAEs and genetic materials.

Sphingomonads in Microbe-Assisted Phytoremediation: Tackling Soil Pollution.

Soil pollution has become a major concern in various terrestrial ecosystems worldwide. One in situ soil bioremediation strategy that has gained popularity recently is microbe-assisted phytoremediation, which is promising for remediating pollutants. Sphingomonads, a versatile bacteria group comprising four well-known genera, are ubiquitous in vegetation grown in contaminated soils. These Gram-negative microbes have been investigated for their ability to induce innate plant growth-promoting (PGP) traits, including the formation of phytohormones, siderophores, and chelators, in addition to their evolutionary adaptations enabling biodegradation and microbe-assisted removal of contaminants. However, their capacity for bacterial-assisted phytoremediation has to date been undervalued. Here, we highlight the specific features, roles, advantages, and challenges associated with using sphingomonads in plant-microbe interactions, from the perspective of future phytotechnologies.