${\rm He}\hbox {-}{\rm H}_{2}{\rm O}_{2}$ Plasma Jet Irradiation of Tissue Surfaces: Study of Dominant Pathways For Plasma Chemical Tissue Removal

Surface tissue-removal mechanisms, resulting from atmospheric He-H₂O₂ plasma jet fluxes impinging on tissue surfaces, were investigated. We employed primarily optical emission for cataloging relative concentrations of reactive plasma radicals versus plasma-jet conditions. The reactive radicals were then correlated with measured tissue-removal rates, under varying experimental conditions to determine the dominant role of OH radicals in the tissue removal. Fourier transform infrared (FTIR) molecular spectroscopy was employed to track molecular bond alterations at tissue surfaces, following the plasma irradiation of tissue surfaces. We studied three types of samples: 1) volatilized tissue fragments, filtered out of the effluent; 2) remaining solid-phase tissue samples in the incision region; and 3) nonprocessed contiguous tissue-surface regions. All surface bondings were compared and contrasted by FTIR analysis. In parallel, both the pure electro surgery (ES) with no added plasma radical fluxes and plasma-assisted ES were used as a dual baseline. This three-part study provides evidence that OH radicals drive the observed changes on tissue surfaces both within, and in bordering tissue regions in a He-H₂O₂ atmospheric plasma jet. Moreover, plasma-assisted ES as compared to pure ES reduces buildup of tissue char on the ES device electrodes, which is a practical advantage in ES surgery. FTIR measurement of the surgical margins (surrounding the removed tissue) is possible in pure plasma-jet tissue removal, via measuring changes in amide A bonds, which are indicators of the level of thermal damage to surrounding tissue, and may be a possible control means to achieve minimum collateral damage.