Method

We induced specific monoclonal antibodies 4497-IgG1 as carriers, which target wall teichoic acids (WTA) existing on MRSA and its biofilm. Radionuclides actiniumr-225 (²²⁵Ac, α-emitter) and lutetium-177 (¹⁷⁷Lu, β-emitter) were conjugated with mAbs using DOTA as chelator. Quality control was assessed using thin layer chromatography and immunoreactivity assays. ²²⁵Ac- and ¹⁷⁷Lu-labelled 4497-IgG1 were employed to evaluate the susceptibility of MRSA and its biofilm to the radioimmunotherapy in vitro. Planktonic MRSA and biofilms, at concentrations of 10⁸ and 10⁷ CFU/mL, were incubated at 37°C for 60 minutes in PBS containing either ²²⁵Ac-mAb (0 - 14.8 kBq) or ¹⁷⁷Lu-mAb (0 - 14.8 MBq). Radiolabelled dunituximab and free radionuclides serve as isotype-matched negative control. The bacterial viability and metabolic activity were subsequently quantified using CFU and XTT assays.