Antibacterial activity against Staphylococcus aureus of curcumin-loaded chitosan spray coupled with photodynamic treatment

Photodynamic treatment is a nonthermal disinfection technology, which uses photosensitizers under specific light conditions to inactivate microorganisms. Curcumin, a component of turmeric and with many medicinal properties, has been used as food additive in many countries. In the study, curcumin was used as a photosensitizer. A controllable LED photodynamic apparatus with a wavelength of 460–465 nm was prepared from a 96-well plate, an LED dimmer and a transformer. The photodynamic activity of curcumin-loaded chitosan against Staphylococcus aureus and its biofilms on stainless-steel were investigated. The results showed that photodynamic inactivation effects relied on curcumin concentration, co-incubation time and illumination time. When 25 μmol/L curcumin-loaded chitosan was co-incubated with Staphylococcus aureus suspension (approximately 6.0 log CFU/mL) for 10 min, the viable count was reduced by 5.0 log CFU/mL, after 10 min exposure to light. On the surface of stainless-steel coupons coated with S. aureus biofilm, the viable count was significantly reduced by more than 5.0 log CFU/cm2 (initial number 5.6 logCFU/m2), after spraying with curcumin (50 μmol/L)-loaded chitosan and 10 min light treatment. So, curcumin photodynamic technology is expected to show great potential application for the inactivation of microbials on the surface of food equipment and fresh food products.