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Through a series of in vitro studies, the essential steps for intracellular drug delivery of paclitaxel using a pH-responsive nanoparticle system have been investigated in breast cancer cells. We successfully encapsulated paclitaxel within polymeric expansile nanoparticles (Pax-eNPs) at 5% loading via a miniemulsion polymerization procedure. Fluorescently tagged eNPs were readily taken up by MDA-MB-231 breast cancer cells grown in culture as confirmed by confocal microscopy and flow cytometry. The ability of the encapsulated paclitaxel to reach the cytoplasm was also observed using confocal microscopy and fluorescently labeled paclitaxel. Pax-eNPs were shown to be efficacious against three in vitro human breast adenocarcinoma cell lines (MDA-MB-231, MCF-7 and SK-BR-3) as well as cells isolated from the pleural effusions of two different breast cancer patients. Lastly, macropinocytosis was identified as the major cellular pathway responsible for eNP uptake, as confirmed using temperature-sensitive metabolic reduction, pharmacologic inhibitors, and fluid-phase marker co-localization.

Although breast cancer patients with localized disease exhibit an excellent long-term prognosis, up to 40% of patients treated with local resection alone may harbor occult nodal metastatic disease leading to increased locoregional recurrence and decreased survival. Given the potential for targeted drug delivery to result in more efficacious locoregional control with less morbidity, the current study assessed the ability of drug-loaded polymeric expansile nanoparticles (eNP) to migrate from the site of tumor to regional lymph nodes, locally deliver a chemotherapeutic payload, and prevent primary tumor growth as well as lymph node metastases. Expansile nanoparticles entered tumor cells and paclitaxel-loaded eNP (Pax-eNP) exhibited dose-dependent cytotoxicity in vitro and significantly decreased tumor doubling time in vivo against human triple negative breast cancer in both microscopic and established murine breast cancer models. Furthermore, migration of Pax-eNP to axillary lymph nodes resulted in higher intranodal paclitaxel concentrations and a significantly lower incidence of lymph node metastases. These findings demonstrate that lymphatic migration of drug-loaded eNP provides regionally targeted delivery of chemotherapy to both decrease local tumor growth and strategically prevent the development of nodal metastases within the regional tumor-draining lymph node basin.

Expansile nanoparticles readily enter human ovarian tumor cells and localize to sites of tumor in vivo with pax-eNP cytotoxicity resulting in superior inhibition of locoregional tumor recurrence following cytoreductive surgery.

The intracellular activity and drug depot characteristics of micrometer-sized hydrogels are described. The hydrogel structure is formed after cellular uptake of a solid polymeric nanoparticle that swells in response to mildly acidic conditions as it transforms from a hydrophobic to a hydrophilic structure. These nanoparticles are rapidly taken up into A549 human non-small cell lung cancer cells with 88.3 ± 0.8% of cells experiencing uptake in 24 h, undergo expansion to release encapsulated drug and can effectively deliver chemotherapeutics in vitro. The anticancer drug paclitaxel was also shown to have a 3- to 4-fold increased affinity for the expanded nanoparticle state, allowing the expansile nanoparticles to act as intracellular drug depots and concentrate the drug locally.

Background To demonstrate feasibility of migration and in situ chemotherapy delivery to regional lymph nodes (LN) in a large animal model using an expansile polymer nanoparticle (eNP) delivery system. Study Design Dual-labeled 50 nm and 100 nm eNP were prepared by encapsulating an IR-813 near-infrared (NIR) fluorescent dye within coumarin-conjugated expansile polymer nanoparticles (NIR-C-eNP). NIR imaging and fluorescent microscopy were utilized to identify intralymphatic migration of NIR-nanoparticles to draining inguinal or mesenteric LN following injection in swine hindlegs or intestine. Nanoparticle-mediated intranodal delivery of chemotherapy was subsequently assessed with Oregon Green paclitaxel-loaded NIR-eNP (NIR-OGpax-eNP). Results NIR imaging demonstrated direct lymphatic migration of 50 nm, but not 100 nm, NIR-C-eNP and NIR-OGpax-eNP to the draining regional LNs following intradermal injection in the hindleg or subserosal injection in intestine. Fluorescent microscopy demonstrated that IR-813 used for NIR real-time trafficking colocalized with both the coumarin-labeled polymer and paclitaxel chemotherapy identified within the subcapsular spaces of the draining LNs. These studies verify nodal migration of both nanoparticle and encapsulated payload, and confirm the feasibility of focusing chemotherapy delivery directly to regional nodes. Conclusions Regionally-targeted intranodal chemotherapy can be delivered to draining LNs for both skin and solid organs using 50 nm paclitaxel-loaded eNP.

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