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Semiconducting polymer dots(Pdots)coupled with bioconjugation have emerged as a new type of nanoprobe that has been used widely for flow cytometry,fluorescence microscopy and biosensing,for example,distribution of biomolecules in vivo,conformation dynamics,target analyte and biomolecule interaction.Here we report the design and synthesis of semiconducting polymers containing antibiotic units.We performed biomolecular conjugation and demonstrated specific bacterial cell labeling by fluorescence imaging and selective photo-killing property for gram-positive bacteria and gram-negative bacteria.The highlights of this work lies in that the developed bioconjuguated Pdots system simultaneously possess the abilities of selective recognition,detection,imaging,and photo-killing for pathogen.Bioconjugeted Pdots have been mainly used for the discriminative detection of bacterial strains from other insensitive cells.1,2 Several bacteria concentrations from 3.1×102 to 5.0×107 cfu mL-1 were prepared by serial dilution in PBS.Figure 4 shows fluorescence response obtained on Van-Pdots and PB-Pdots incubated with different bacterial concentrations.The fluorescence response increased regularly with the increase of bacteria concentrations,indicating that Van-Pdots and PB-Pdots were absorbed onto the surface of bacterial cells to produce a bioprobe-bacterial cells complex.The results for bacteria detection showed that the concentration of bacteria and the response were highly correlated(Figure 1a and 1b).A linear relationship between the response and the logarithm of the S.aureus concentration using Van-Pdots was obtained for concentrations ranging from 1.0×104 to 1.0×106 cfu mL-1,with a slope of 60.9 and a correlation coefficient of 0.994(Figure 1a).Figure 1b show a linear relationship between the response and the logarithm of the P.aeruginosa concentration using PB-Pdots,with a slope of 342.8 and a correlation coefficient of 0.997.We examined whether bioconjugated Pdots could fulfill the purpose of selective photo-killing.Fig.2a and 2b further verified that Van-Pdots and PB-Pdots showed a selective photo-killing for Van-sensitive bacteria,S.aureus and PB-sensitive bacteria,P.aeruginosa,respectively.It was almost completely killed within 1 h in Van-Pdots or PB-Pdots under white light irradiation.The partial inactivation of Van-insistent bacteria or PB-insistent bacteria occurred under the same condition.These results indicated that bioconjugated Pdots was capable of selective phototoxicity to specific bacteria.The antibacterial activity of bioconjugated Pdots can be due to two mechanisms,including the singlet oxygen and other reactive oxygen species in the presence of photosensitizer and oxygen under white light irradiation and the binding of antibiotic andD-Ala-D-Ala of bacterial cells surface3.