Red blood cell membrane biomimetic nanoprobes for ratiometric imaging of reactive oxygen species level in atherosclerosis

Atherosclerosis (AS) is a major pathological factor to cardiovascular diseases, wherein reactive oxygen species (ROS) serve as the initiating link for the development of AS. However, direct and accurate assessment of ROS levels in AS plaque sites remains challenging. Herein, by embedding a ROS-responsive fluorescent small molecule (HDB with positive response or Cy7 with negative response) and a stable ROS-independent fluorescent dye CH1055 into red blood cell membrane (RBCM)-biomimetic liposomes, two biomimetic nanoprobes (R-Lipo@HDB/CH1055 and R-Lipo@Cy7/CH1055) were developed for indicating the existence of AS plaques and direct in situ ratiometric imaging of ROS at plaque sites. The fused RBCM endows the nanoprobes with attractive immune escape properties and the ability to accumulate at the AS sites. They not only can indicate the presence of plaques by the second near-infrared (NIR-II) fluorescence of CH1055, but also enable the accurate response to ROS levels through the upward or downward ratiometric fluorescence of HDB or Cy7 to CH1055, avoiding the interference of probe accumulation fluctuation or metabolism at the disease site and thus allowing for more accurate imaging compared to traditional monochromatic imaging. Via the specific responses of HDB and Cy7 to different species of ROS, we verified the upregulation of these ROS at the AS site using these two nanoprobes, and demonstrated their potential to assess the therapeutic effect of AS drugs. This study paves a feasible way to construct a ratiometric imaging platform using RBCM biomimetic liposomes to simultaneously encapsulate several functional molecules, achieving the disease diagnosis, pathological analysis and drug effect evaluation.