Low-frequency ultrasound-assisted application of Ag/Cu nanocomposites as a promising strategy for the treatment of purulent wounds

The purpose of this experimental study was to systematically evaluate the synergistic effects of combining low-frequency ultrasound (LF US) with silver/copper nanocomposites (Ag/Cu NCs) for treating experimental purulent wounds infected with multidrug-resistant (MDR) bacteria. The Ag/Cu NCs (size of 73.2 ± 16.7 nm) were synthesized using a combined ultrasound-assisted polyol method. In vitro testing showed that LF US treatment significantly reduced the minimum inhibitory and bactericidal concentrations of Ag/Cu NCs for all tested MDR strains, including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. In vivo experiments on rats with purulent wounds revealed that the combination therapy (Ag/Cu NCs + LF US) led to a significantly accelerated healing rate and superior to single-modality treatments of Ag/Cu NCs, LF US or Chlorhexidine. Histological and immunohistochemical analyses provided insights, showing that the combined therapy rapidly resolved inflammation, evidenced by a significantly faster decrease in the pro-inflammatory M1 macrophages and a corresponding earlier and more robust increase in the anti-inflammatory M2 macrophages by day 3. This rapid polarization shift, along with the faster clearance of the bacterial load, promoted the earlier formation of granulation tissue, restoration of normal microcirculation, and epithelialiation. The use of LF US in combination with Ag/Cu NCs promoted local accumulation and systemic absorption of silver and copper with an acceptable safety profile. The combined application of Ag/Cu NCs and LF US presents a promising and highly effective strategy for treating purulent, MDR-infected wounds. These preclinical studies provide strong support for the further optimization and translation of this integrated approach into clinical practice.