Nanoengineered Bifidobacterium bifidum with Optical Activity for Photothermal Cancer Immunotheranostics.

There is substantial interest regarding the understanding and designing of nanoengineered bacteria to combat various fatal diseases. Here, we report the nanoengineering of Bifidobacterium bifidum using Cremophor EL to encapsulate organic dye molecules by simple incubation and washing processes while maintaining the bacterial morphology and viability. The prepared functional bacteria exhibit characteristics such as optical absorbance, unique fluorescence, powerful photothermal conversion, low toxicity, excellent tumor targeting, and anticancer efficacy. They also displayed significant in vivo fluorescent expression in implanted colorectal cancerous tumors. Moreover, the powerful photothermal conversion of the functional bacteria could be spatiotemporally evoked by biologically penetrable near-infrared laser for effective tumor regression in mice, with the help of immunological responses. Our study demonstrates that a nanoengineering approach can provide the strong physicochemical traits and attenuation of living bacterial cells for cancer immunotheranostics.