This technology uses a non-toxic phthalocyanine dye to sensitize bacteria to NIR light. The phthalocyanine dye covalently attaches to amine groups on the surface of bacteria via click chemistry and is highly effective at killing gram positive and gram negative bacteria after only 1 minute of exposure to 690nm light (99.8%). This dye is also able to effectively kill amoebas, suggesting it may be a way of targeting lethal, untreatable infections Naegleria fowleri (aka “brain eating amoeba”) infections. The inventors can couple the photoreactive dye to a modified bacteriophage M13 to direct the photoreactive dye specifically to bacterial or amoeba cells. M13 bacteriophages can be loaded with hundreds or thousands of dye molecules, in contrast, antibodies can only load ~3 dye molecules. To achieve target specificity, the inventors engineered a strain of M13 that contains a biotin acceptor peptide (BAP) in one of its capsid proteins. The BAP peptide can be biotinylated and serve as a handle for streptavidin antibody conjugation. This design creates a modular one-step procedure to target any bacteria that has a suitable specific antibody. Together, this M13-dye-antibody conjugation allows very precise delivery of high doses of photoreactive dye. Photosensitization has also been proposed as a cancer treatment mechanism, and the inventors demonstrated successful targeting and killing of ovarian cancer cells in vitro using this method. Importantly, this technology could also be generalized as a way of gently and rapidly disinfecting surfaces, medical devices, or food.