This invention relates to a method for tracking stem cells characterized in that the stems cells are labelled with at least one fluorescent conjugated polymer nanodot and the fluorescence of the labelled cells is detected. The fluorescent conjugated polymer nanodot comprises a conjugated polymer such as poly(9,9-dihexylfluorene-alt-2,1,3-benzoxadiazole) (PFBD) capped with an amphiphilic co-polymer such as DSPE-PEG2000 (1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-conjugated polyethylene glycol) and DSPE-PEG2000 maleimide. The method allows for the tracking of stem cells over long periods of time after transplantation exceeding 25 days. The stem cells are not compromised in their behaviours of proliferation, migration, differentiation and secretome by the labelling method of the invention. The method may be useful as a research tool in regenerative stem cell medicine. Corresponding stem cell tracking kits are also disclosed as well as stem cells labelled with the fluorescent conjugated polymer nanodots.
