Antibacterial properties of photoactive starch/porphyrin-based materials

Photodynamic therapy (or PDT) has been used with success for many years as a cancer therapy but more recently has gained popularity as an alternative to the conventional antimicrobial approaches. Microorganisms have the ability to evolve and select resistant strains to antimicrobials [1,2]. In fact, it is estimated that by 2050, deaths due to antimicrobial resistance will exponentially rise above 10 million deaths per year globally, surpassing the current number of 700,000 deaths per year [1]. Therefore, other methodologies and treatments against resistant microorganisms are needed and antimicrobial photodynamic therapy (or aPDT) may prove to be a solution. Porphyrin derivatives when combined simultaneously with light and dioxygen, have been identified as good antimicrobial agents through a photodynamic action on the microbial structures. However, considering some clinical applications, like wound treatments, for instance, the delivery in a solution may not be practical. The evidence that the incorporation of porphyrinic sensitizers (PS) into solid supports maintain the photodynamic activity lead us to use glycomaterials, namely potato starch to develop antimicrobial photoactive materials. In this work the sensitizer 5,10,15,20-tetrakis(1- methylpyridinium-4-yl)porphyrin tetra-iodide (TMPyP) was prepared and further incorporated through melt-mixing into starch-based formulations. The biological properties of starch/TMPyPbased material was assessed. In this communication, it will be discussed the synthesis of TMPyP, its immobilization on the support and in vitro and ex vivo (porcine skin) antimicrobial properties of the developed photoactive starch/TMPyP-based material against methicillin-resistant Staphylococcus aureus (MRSA), a strain responsible for many hospital acquired infections, and with increasing prevalence [3].