World Health Organization estimated that in 2018 about 12% of women were diagnosed with breast cancer, and 17% of them were found to be triple negative breast cancers. Immunotherapy is currently one of the most appealing and promising cancer treatments. However, conventional systemic administration of immunotherapeutics can often lead to adverse side effects and insufficient anti-tumor immune response. Intratumoral delivery of immunotherapeutics can minimize systemic toxicity, increase tumor exposure, and activate an efficient anti-tumor immune response. We developed a nanofluidic-based device for intratumoral drug delivery named nanofluidic drug-eluting seed (NDES). This device can accomplish the clinical demand for a local and sustained drug delivery system.