A surgical spray instrument is disclosed comprising a main body connectable to a transfer tube; a propellant actuator for selectively releasing propellant from the main body and along the transfer tube and out through a distal end thereof. An ion emitter is arranged along the tube, the ion emitter having an ion emission zone. This enables the directed and concentrated delivery of therapeutic, pharmacological and diagnostic agents to tissues inside or outside of the body. There is further disclosed a surgical assembly for enabling uniform deposition of a particulate material to a surface of an intracorporeal cavity of a patient. The surgical assembly comprises an ion emitter; a dispenser having an outlet locatable within the cavity and for dispensing the particulate material therefrom, and a processor for determining a location of the ion emission zone of the ion emitter in dependence upon the position of the outlet of the distributor within the cavity to provide for the uniform deposition.