Ultra-sonophorated Oxygen-Loaded Nanobubbles effectively improve transcutaneous oxygenation in mice.

Aim. Dextran-shelled, decafluoropentane-containing Oxygen-Loaded Nanobubbles (OLNs), ~600 nm-sized and negatively charged, are new oxygenating drugs developed to treat hypoxia-associated dermal pathologies, including cutaneous chronic wounds (diabetic foot, critical limb ischemia). In the present work, OLN abilities to deliver O2 in vivo were analyzed by measuring oxygen transcutaneous tension (TcPO2) of topically treated mice. Methods. All procedures were done in accordance with the EU guidelines and with the approval of the University of Torino animal care committee. The shaved abdomens of six mice, anaesthetized by injecting intramuscularly a mixture of tiletamine/zolazepam 20 mg/Kg (Zoletil 100; Virbac) and 5 mg/Kg xylazine (Rompun; Bayer), were topically treated with a liquid formulation of OLNs, prepared as previously described (1), and ultrasonicated for 15 sec using a home-made ultrasound (US) equipment (frequency: 1 MHz). Before and after (45-60 min) treatment, TcPO2 was measured through TINA TCM30 oxymeter (Radiometer Copenhagen). Notable, all TcPO2 measurements were taken after physiologic stabilization. Results. Basal TcPO2 values were highly non-homogeneous, possibly as a consequence of peripheral vasoconstriction induced by anaesthesia. Nevertheless, 45-60 min after topical administration of ultra-sonophorated OLNs, all mice displayed higher oxygenation levels in a time-sustained manner. For more details, see Figure 1, showing tcPO2 values between OLN-treated and untreated skin of each mouse. Figure 1. In vivo O2 release from ultra-sonophorated OLNs. Conclusion. In vivo ultra-sonophorated OLNs proved to be able to cross the skin barrier, and to effectively increase TcPO2 levels of previously hypoxic tissues, confirming that topical administration of exogenous O2, properly encapsulated in nanobubble formulations, might be a new suitable and efficient approach to treat hypoxia-associated cutaneous pathologies. Of great interest would be the clinical application of OLNs, in the treatment of critical limb ischemia and diabetic foot. Furthermore, OLNs proved to be effective in controlling bacterial proliferation (such as by meticillin-resistant Staphylococcus aureus, MRSA). Acknowledgements. Work supported by funding from Ateneo-Compagnia di San Paolo. (1) Preparation and characterization of dextran nanobubbles for oxygen delivery. Cavalli R, Bisazza A, Giustetto P, Civra A, Lembo D, Trotta G, Guiot C, Trotta M.,Int J Pharm. 2009 Nov 3;381(2):160-5.