the invention relates to a novel method of administration , and device employed in the method , for administering a treatment species to the lungs of a recipient patient . the method involves introducing the device of the invention to the venous system of the patient , the size of the treatment species being such that , upon introduction to the venous system of the patient , the device will impact in a region of a lung capillary of the patient . the treatment species gains access to the lung and / or lung epithelia due to proteases associated with the treatments species . the application of the method to the treatment of cystic fibrosis is also claimed .