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Polyethylenimines (PEIs), a group of polycationic molecules, are known to impair the outer membrane of Gram-negative bacteria and exhibit antimicrobial activity. The outer membrane of Gram-negative strains hinders the uptake of photosensitizer chlorophyllin. In this study, we report chlorophyllin and branched PEI combinations' activity against Escherichia coli strains DH5α and RB791, Salmonella enterica sv. Typhimurium LT2, and Bacillus subtilis 168. The minimal bactericidal concentration (MBC) was determined by plating cells treated with different concentrations of PEI and chlorophyllin on agar and monitoring their growth after 24 h. All tested combinations of PEI and chlorophyllin were lethal for S. enterica after 240 min of incubation in light, whereas PEI alone (<100 µg mL−1) was ineffective. In the darkness, complete inhibition was noted with a combination of ≥2.5 µg mL−1 chlorophyllin and 50 µg mL−1 PEI. If applied alone, PEI alone of ≥800 µg mL−1 of PEI was required to completely inactivate E. coli DH5α cells in light, whereas with ≥5 µg mL−1 chlorophyllin, only ≥100 µg mL−1 PEI was needed. No effect was detected in darkness with PEI alone. However, 1600 µg mL−1 PEI in combination with 2.5 µg mL−1 resulted in complete inactivation after 4 h dark incubation. PEI alone did not inhibit E. coli strain RB791, while cells were inactivated when treated with 10 µg mL−1 chlorophyllin in combination with ≥100 µg mL−1 (in light) or ≥800 µg mL−1 PEI (in darkness). Under illumination, B. subtilis was inactivated at all tested concentrations. In the darkness, 1 µg mL−1 chlorophyllin and 12.5 µg mL−1 PEI were lethal for B. subtilis. Overall, PEI can be used as an antimicrobial agent or potentiating agent for ameliorating the antimicrobial activity of chlorophyllin. [ABSTRACT FROM AUTHOR]

Polyethylenimines (PEIs), a group of polycationic molecules, are known to impair the outer membrane of Gram-negative bacteria and exhibit antimicrobial activity. The outer membrane of Gram-negative strains hinders the uptake of photosensitizer chlorophyllin. In this study, we report chlorophyllin and branched PEI combinations’ activity against Escherichia coli strains DH5α and RB791, Salmonella enterica sv. Typhimurium LT2, and Bacillus subtilis 168. The minimal bactericidal concentration (MBC) was determined by plating cells treated with different concentrations of PEI and chlorophyllin on agar and monitoring their growth after 24 h. All tested combinations of PEI and chlorophyllin were lethal for S. enterica after 240 min of incubation in light, whereas PEI alone (−1) was ineffective. In the darkness, complete inhibition was noted with a combination of ≥2.5 µg mL−1 chlorophyllin and 50 µg mL−1 PEI. If applied alone, PEI alone of ≥800 µg mL−1 of PEI was required to completely inactivate E. coli DH5α cells in light, whereas with ≥5 µg mL−1 chlorophyllin, only ≥100 µg mL−1 PEI was needed. No effect was detected in darkness with PEI alone. However, 1600 µg mL−1 PEI in combination with 2.5 µg mL−1 resulted in complete inactivation after 4 h dark incubation. PEI alone did not inhibit E. coli strain RB791, while cells were inactivated when treated with 10 µg mL−1 chlorophyllin in combination with ≥100 µg mL−1 (in light) or ≥800 µg mL−1 PEI (in darkness). Under illumination, B. subtilis was inactivated at all tested concentrations. In the darkness, 1 µg mL−1 chlorophyllin and 12.5 µg mL−1 PEI were lethal for B. subtilis. Overall, PEI can be used as an antimicrobial agent or potentiating agent for ameliorating the antimicrobial activity of chlorophyllin.

Infectious deaths due to drug resistance of pathogens caused by the abuse of antibiotics have seriously endangered public health in the world. Therefore, it is urgent to develop diversified methods for rapid detection of pathogens and antimicrobial drugs that are not prone to develop resistance. Conjugated polymers (CPs) are macromolecular compounds composed of many luminescent units through covalent bond. They have high molar extinction coefficient and strong light absorption capacity. In addition, they have good photo stability and excellent biocompatibility. In recent years, conjugated polymer nanomaterials (CPNs) have stimulated the research enthusiasm of many researchers because of the materials' small size, high fluorescence intensity, and easy modification. This article reviews the recent research progress of conjugated polymer nanomaterials in the detection and killing of pathogenic microbes.