Comparative sorption and desorption behaviors of PFHx S and PFOS on sequentially extracted humic substances

The sorption and desorption behaviors of two perfluoroalkane sulfonates（PFSAs）, including perfluorohexane sulfonate（PFHx S） and perfluorooctane sulfonate（PFOS） on two humic acids（HAs） and humin（HM）, which were extracted from a peat soil, were investigated. The sorption kinetics and isotherms showed that the sorption of PFOS on the humic substances（HSs） was much higher than PFHx S. For the same PFSA compound, the sorption on HSs followed the order of HM 〉 HA2 〉 HA1. These suggest that hydrophobic interaction plays a key role in the sorption of PFSAs on HSs. The sorption capacities of PFSAs on HSs were significantly related to their aliphaticity, but negatively correlated to aromatic carbons,indicating the importance of aliphatic groups in the sorption of PFSAs. Compared to PFOS,PFHx S displayed distinct desorption hysteresis, probably due to irreversible pore deformation after sorption of PFHx S. The sorption of the two PFSAs on HSs decreased with an increase in p H in the solution. This is ascribed to the electrostatic interaction and hydrogen bonding at lower p H. Hydrophobic interaction might also be stronger at lower p H due to the aggregation of HSs.

The relief of hypoxic microenvironment using an O_(2) self-sufficient fluorinated nanoplatform for enhanced photodynamic eradication of bacterial biofilms

Hypoxia,an important characteristic of bacterial biofilms,can hinder the generation of reactive oxygen species(ROS)in photodynamic therapy(PDT),leading to reduced therapeutic efficacy of PDT.In order to address this issue,fluorinated liposome was fabricated as an oxygen-sufficient nanoplatform for enhanced photodynamic eradication of bacterial biofilms.The liposomes(denoted as Lip-Ce6-PFH@O_(2))were prepared by co-encapsulation of O_(2) carrier perfluorohexane(PFH)and photosensitizer chlorin e6(Ce_(6)).Lip-Ce6-PFH@O_(2) could achieve efficient biofilm penetration due to the positively charged surface.The hypoxic microenvironment of biofilms would then be relieved,leading to the generation of more ROS under laser irradiation.Therefore,the bactericidal capability of PDT could be significantly improved because of the co-delivered O_(2) carrier PFH.Lip-Ce6-PFH@O_(2) exhibited much better antibiofilm ability than that of Lip-Ce6 both in vitro and in vivo.Meanwhile,Lip-Ce6-PFH@O_(2) also effectively alleviated inflammation symptoms and accelerated wound healing in the mice model.In general,this study provides a new paradigm to enhance the therapeutic efficacy of PDT for efficient biofilm eradication.