Dynamic visualization monitoring of cell membrane damage using polarity-responsive amphiphilic carbon dots

Development of organelle-targeted fluorescent carbon dots (CDs) has attracted extensive attention recently, however, the application of CDs for monitoring cell membrane integrity is rarely reported. Herein, we propose a kind of amphiphilic CDs (∼2.84 nm) derived from o-phenylenediamine and urea (termed M−CDs). M−CDs display high-affinity capacity to polysaccharide structures, which allows the rapid (∼within 30 s), wash-free fluorescence (FL) imaging of microbes, including bacteria and fungi. For mammalian cells, M−CDs can selective bind to the intracellular cytoskeletal filaments when the cells undergo cytomembrane destruction. More interestingly, the FL feature of M−CDs is polarity-dependent that emits the maximum emission wavelength from 501 to 561 nm when the solvent polarity increases from 0.02 to 0.32, which offers the opportunity to detect the polarity microenvironment. We observe that the polarity increases significantly when M−CDs pass through the broken cytomembrane. M−CDs are finally adopted for the fast morphometric analysis of abnormal erythrocytes in haematuria, providing a novel avenue for the rapid test of membrane-related diseases.