Nanotechnology in antimicrobial photodynamic inactivation

Photodynamic therapy (PDT) and photodynamic inactivation (PDI) are technologies that utilize visible light and photosensitizers (PS) to inactivate cells. PDT is currently in use for the treatment of several types of tumors. Although cancer has been successfully treated with PS and light, antimicrobial PDI is emerging as a new treatment modality for bacterial infections due to its effectiveness and less likelihood of inducing bacterial resistance. Resistance to therapy is in part due to the ability of the organisms to form a biofilm, which provides a microenvironment that protects the microorganism from antibiotics and attack by the host's immune system. In vitro, PDI nonetheless was shown to be effective against Gram-negative and Gram-positive bacteria. When used in-vivo however, several factors were shown to influence and diminish the effectiveness of PDI, such as aggregation of PS and plasma protein binding. To circumvent these factors, different nanotechnology platforms were used to enhance the photodynamic inactivation efficacy, such as liposomes, micelles and nanoparticles, by reducing the PS aggregation and albumin binding to the PS. In general, studies have shown that photodynamic inactivation efficacy could be enhanced when suitable nanocarriers are used to deliver the PS.