The irrational or excessive use of antibiotics causes the emergence of bacterial resistance, making antibiotics less effective or ineffective. As the number of resistant antibiotics increases, it is crucial to develop new strategies and innovative approaches to potentiate the efficacy of existing antibiotics. In this paper, we report that some existing antibiotics can produce reactive oxygen species (ROS) directly under light irradiation. Thus, a novel antibacterial photodynamic therapy (PDT) strategy is proposed by using existing antibiotics for which the activities are potentiated via light-activation. This antibiotic-based PDT strategy can achieve efficient bacteria killing with a low dosage of antibiotics, indicating that bacterial killing can be enhanced by the light-irradiated antibiotics. Moreover, the specific types of ROS produced by different antibiotics under light irradiation were studied for better elucidation of the antibacterial mechanism. The findings can extend the application of existing antibiotics and provide a promising strategy for treatment of bacterial infections and even cancers.

Sensitive detection of uracil-DNA glycosylase (UDG) activity is very important in the study of many fundamental biochemical processes and clinical applications. Here, we develop a novel assay for the detection of UDG activity by using the self-initiating multiple rolling circle amplification (SM-RCA) strategy. We first design a trigger probe modified with NH 2 at its 3′-terminal and uracil base in the middle of sequence, which is complementary to a cyclized padlock probe. In the presence of UDG, a uracil base can be excised by UDG to generate an apurinic/apyrimidinic (AP) site. The AP site is recognized and cleaved by endonuclease IV (Endo IV), releasing the primer with 3′-OH. The primer can trigger the rolling circle amplification (RCA) reaction, producing a long and repeated DNA strand embedded some uracil bases. These uracil bases can be cleaved by UDG and Endo IV again, and then, more primers are generated to initiate SM-RCA reaction, producing large amounts of DNA product. Afterward, the DNA product is measured by a specific DNA fluorescence dye for quantitative detection of UDG activity. The linear range of the method is 5 × 10 –5 to 1.25 × 10 –3 U/mL, and the detection limit is 1.7 × 10 –5 U/mL. This method not only utilizes the target UDG itself to trigger RCA but also further induces SM-RCA reaction, providing a simple, sensitive, and cost-effective strategy for the detection of glycosylase and clinical diagnosis.