Mn-doped Zn/S quantum dots as photosensitizers for antimicrobial photodynamic inactivation

摘要

The survival of pathogens on surfaces is a major contributor to infection transmission, and drives the development of selfsterilizingsurfaces. Here, we have investigated if manganese-doped zinc sulfide quantum dots (Mn:ZnS QDs) can be usedas photosensitizers for their potential application in surface disinfection via antimicrobial photodynamic inactivation(aPDI). A small library of Mn:ZnS QDs capped with 3-mercaptopropionic acid was synthesized using a hydrothermalapproach in which both the amount of manganese (0-30 at.%) and heating period (9 - 20 h) were varied. The resultantMn:ZnS QDs were shown by transmission electron microscopy to vary in size from 2.6-3.9 ? as a function of heatingtime, and exhibited a strong emission band at ~598 nm (λ_(ex) = 325 nm). Upon excitation of 5%-Mn:ZnS QDs at 514 nm, anear-IR emission band attributable to singlet oxygen phosphorescence was observed at 1278 nm, confirming that theseQDs may function as photosensitizers via a Type II mechanism. The aPDI efficacy of the Mn:ZnS QDs was evaluatedagainst both Gram-positive [methicillin-resistant S. aureus (MRSA; ATCC-44), vancomycin-resistant E. faecium (VRE;ATCC-2320)], and Gram-negative [multidrug-resistant A. baumannii (MDRAB; ATCC-1605), NDM-1 positive K.pneumoniae (KP; ATCC-2146)] bacteria. Our best results demonstrated detection limit photodynamic inactivation (6 logunits reduction) of KP, MDRAB, and MRSA upon illumination (30 min; 65±5 mW/cm~2; 400-700 nm), but only a ~1 logunit reduction against VRE. Together with antiviral studies of Zika virus that showed ~3 log units of inactivation, thesefindings demonstrate the utility of Mn:ZnS QDs as photosensitizers for aPDI.