In this project, the lab designed a new nanofiber precursor (pNFP), a new generation of nanofibers with preferential lung-targeting and retention properties for treating pulmonary metastases. The nanofibers, which display a very high aspect ratio, can rearrange into a large interfibril network. In the deep alveolar areas, this network favors passive lung targeting and local retention via mechanical trapping. When used as a delivery platform, pNFP improves local drug accumulation with minimal off-target distribution. Additionally, the nanofibers retain onsite to unleash a broad spectrum of antitumor activity over time, leading to a safer and more effective long-term treatment of breast cancer metastatic lung lesions. This new technology could be transposable with additional advancements, thereby locally delivering and releasing various drug molecules for treating other lung malignancies, including cystic fibrosis, pleural effusion and chronic obstructive pulmonary disease.