New insight into photoacoustic conversion efficiency by plasmon-mediated nanocavitation: Implications for precision theranostics

The probe-assisted integration of imaging and therapy into a single modality offers significant advantages in bio-applications.As a newly developed photoacoustic (PA) mechanism,plasmon-mediated nanocavitation,wherebyphotons are effectively converted into PA shockwaves,has excellent advantages for image-guided therapy.In this study,by simulating the laser absorption,temperature field,and nanobubble dynamics using both finite-element analysis and computational fluid dynamics,we quantified the cavitation-induced PA conversion efficiency of a water-immersed gold nanosphere,revealing new insights.Interestingly,sequential multi-bubble emission accompanied by high PA signal production occur under a single high-dose pulse of laser irradiation,enabling a cavitation-induced PA conversion efficiency up to 2％,which is ～50 times higher than that due to thermal expansion.The cavitation-induced PA signal has unique frequency characteristics,which may be useful for a new approach for in vivo nanoparticle tracking.Our work offers theoretical guidance for accurate diagnosis and controllable therapy based on plasmon-mediated nanocavitation.