New oxidative alginate-biocide hydrogels against stone biodeterioration

To address the problem of the biodeterioration of stone monuments by developing innovative methodologies, two new alginate hydrogels were obtained by using titanium dioxide as photoactivatable biocide and sodium dichloroisocyanurate as reservoir of hypochlorous acid. The effectiveness of both hydrogels in removing the biological patina on artificially colonized Lecce stones without altering the properties of the treated substrates was demonstrated by measurements of light microscopy, colorimetry, SEM/EDS analyses and 1H-NMR relaxometry. The biocidal activity of the new developed hydrogels has been also tested on natural cyanobacterial biofilms collected in Roman Catacombs and grown on agar medium and on calcareous stones. The results are very promising with the complete inhibition of cyanobacterial photosynthesis and without any side effects on the substrates tested.