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Narcisa Mandras,1 Monica Argenziano,2 Mauro Prato,1 Janira Roana,1 Anna Luganini,3 Valeria Allizond,1 Vivian Tullio,1 Nicole Finesso,4 Sara Comini,1 Bruno Emilio Bressan,4 Francesca Pecoraro,4 Giuliana Giribaldi,4 Adriano Troia,5 Roberta Cavalli,2 Anna Maria Cuffini,1,* Giuliana Banche1,* 1Department of Public Health and Pediatric Sciences, University of Torino, Turin, 10126, Italy; 2Department of Drug Science and Technology, University of Torino, Turin, 10125, Italy; 3Department of Life Sciences and Systems Biology, University of Torino, Turin, 10123, Italy; 4Department of Oncology, University of Torino, Turin, 10126, Italy; 5Istituto Nazionale di Ricerca Metrologica, Turin, 10135, Italy*These authors contributed equally to this workCorrespondence: Valeria Allizond, Department of Public Health and Pediatric Sciences, University of Torino, Via Santena 9, Turin, 10126, Italy, Tel +390116705644, Fax +390112365644, Email valeria.allizond@unito.itPurpose: Medium versus low weight (MW vs LW) chitosan-shelled oxygen-loaded nanodroplets (cOLNDs) and oxygen-free nanodroplets (cOFNDs) were comparatively challenged for biocompatibility on human keratinocytes, for antimicrobial activity against four common infectious agents of chronic wounds (CWs) – methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pyogenes, Candida albicans and C. glabrata – and for their physical interaction with cell walls/membranes.Methods: cNDs were characterized for morphology and physico-chemical properties by microscopy and dynamic light scattering. In vitro oxygen release from cOLNDs was measured through an oximeter. ND biocompatibility and ability to promote wound healing in human normoxic/hypoxic skin cells were challenged by LDH and MTT assays using keratinocytes. ND antimicrobial activity was investigated by monitoring upon incubation with/without MW or LW cOLNDs/cOFNDs either bacteria or yeast growth over time. The mechanical interaction between NDs and microorganisms was also assessed by confocal microscopy.Results: LW cNDs appeared less toxic to keratinocytes than MW cNDs. Based on cell counts, either MW or LW cOLNDs and cOFNDs displayed long-term antimicrobial efficacy against S. pyogenes, C. albicans, and C. glabrata (up to 24 h), whereas a short-term cytostatic effects against MRSA (up to 6 h) was revealed. The internalization of all ND formulations by all four microorganisms, already after 3 h of incubation, was showed, with the only exception to MW cOLNDs/cOFNDs that adhered to MRSA walls without being internalized even after 24 h.Conclusion: cNDs exerted bacteriostatic and fungistatic effects, due to the presence of chitosan in the outer shell and independently of oxygen addition in the inner core. The duration of such effects strictly depends on the characteristics of each microbial species, and not on the molecular weight of chitosan in ND shells. However, LW chitosan was better tolerated by human keratinocytes than MW. For these reasons, the use of LW NDs should be recommended in future research to assess cOLND efficacy for the treatment of infected CWs.Keywords: chitosan nanodroplets, methicillin-resistant Staphylococcus aureus, Streptococcus pyogenes, Candida spp, chronic wounds |
