Effects of photodynamic therapy on materials used in hospitals

In the hospital environment, the disinfection and sterilization of medical devices are essential, and the development of efficient techniques with low cost and absence of collateral effects is still necessary. The photodynamic therapy (PDT) is a successful technique for treating infections caused by different microorganisms, but nothing is reported about the effects of PDT on materials often employed in hospitals. In this way, this in vitro study aimed to verify the actions of PDT on polypropylene, aluminum and Aisi 304 steel taking into account the following aspects: cytotoxicity, mechanical properties and effects on bacterial biofilms. For that, this study was splitted into three experimental phases. In the first one, 27 samples of each proposed material (polypropylene, aluminum and Aisi 304 steel) were prepared and randomly distributed in 27 experimental groups (n = 3) for treatment with autoclave (121 °C for 30 min) or PDT (λ = 660nm, 100 mW, 60 J, 111 mW/cm
²
, 66.66 J/cm
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, for 10 minutes) with different repetitions of the treatments (samples treated with 1, 4, 28 and 120 repetitions). After that, it was performed a cytotoxicity test using Vero fibroblasts. In the second experimental phase, 90 samples of each material were prepared, which were randomly distributed in the same previously described 27 experimental groups (n = 10). After the treatments, samples were submitted to tensile strength test. In the third experimental phase, biofilms of Staphylococcus aureus were prepared and then treated with PDT. The data were statistically analyzed at a significance level of 5%. The Vero cells showed similar adhesion, spreading and growth in both experimental groups, and the cytochemical analysis showed no changes in cellular activity in any of the experimental groups. Autoclave sterilization increased the elastic modulus of Aisi 304 steel and polypropylene and reduced it in aluminum after 120 repetitions. PDT increased the elastic modulus of steel, aluminum and polypropylene. PDT significantly reduced the biofilm of Staphylococcus aureus formed on the materials. It was possible to conclude that PDT is a promising alternative technique for decontamination of materials and, although it alters some mechanical properties, PDT seems to be a good technique for future use in hospitals.