Herein, novel carbon dots (CDs) with efficient antibacterial activity are prepared by a simple cyclization reaction of 4-formylbenzoic acid and pyrrole and cross-linking with p-phenylenediamine at room temperature. The CDs exhibit the fluorescence property of red emission, greatly reducing the noise interference from bacterial autofluorescence in fluorescence imaging. At the same time, the CDs with the feature of red absorption facilitate the achievement of light excitation of deep tissues in the living body. Owing to the introduction of the porphyrin ring structure as a photosensitizer, the CDs are able to trigger the generation of singlet oxygen. When excited by a 638 nm laser and irradiated for 20 min, 10 μg mL−1 CDs can achieve complete bacterial extinction. Laser confocal microscopy imaging further demonstrates that the CDs act on the outside of bacteria and generate reactive oxygen species under red light irradiation, providing a non-multidrug resistant sterilization method.
Conventional anti-tumor methods face challenges such as limited targetability and severe side effects, even when using carrier-assisted delivery of corresponding agents. Additionally, relying on a single modality often leads to an inadequate treatment response. Leveraging the facultative bacteria’s migration tendency to hypoxic tumor tissue and the effectiveness of physicochemical approaches in bacterial engineering, non-pathogenic Escherichia coli MG1655 was metabolically modified for tumor-targeted and synergistic therapy. By taking advantage of the essential D-alanine (D-Ala) component in bacterial peptidoglycan, chemotherapeutic D-Ala-OXA and photosensitizing D-Ala-PPa were firstly prepared and simultaneously labeled on MG1655, creating the multimodal platform (O/P@MG1655). When exposed to red light irradiation, O/P@MG1655 effectively eliminated tumor cells through chemo-photodynamic therapy and induced immunogenic cell death to trigger immunotherapy. Notably, significant inhibition of tumor growth and excellent biosafety were observed in a subcutaneous CT26 mouse tumor model. This dual metabolic modification strategy represents a remarkable advancement in the development of functionalized targeted bacteria for precise tumor treatment.
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