Expansile Nanoparticles Research Articles

Radiolabeled Biodistribution of Expansile Nanoparticles: Intraperitoneal Administration Results in Tumor Specific Accumulation.

Nanoparticle biodistribution in vivo is an essential component to the success of nanoparticle-based drug delivery systems. Previous studies with fluorescently labeled expansile nanoparticles, or "eNPs", demonstrated a high specificity of eNPs to tumors that is achieved through a materials-based targeting strategy. However, fluorescent labeling techniques are primarily qualitative in nature and the gold-standard for quantitative evaluation of biodistribution is through radiolabeling. In this manuscript, we synthesize 14C-labeled eNPs to quantitatively evaluate the biodistribution of these particles in a murine model of intraperitoneal mesothelioma via liquid scintillation counting. The results demonstrate a strong specificity of eNPs for tumors that lasts one to 2 weeks postinjection with an overall delivery efficiency to the tumor tissue of 30% of the injected dose which is congruent with prior reports of preclinical efficacy of the technology. Importantly, the route of administration is essential to the eNP's material-based targeting strategy with intraperitoneal administration leading to tumoral accumulation while, in contrast, intravenous administration leads to rapid clearance via the reticuloendothelial system and low tumoral accumulation. A comparison against nanoparticle delivery systems published over the past decade shows that the 30% tumoral delivery efficiency of the eNP is significantly higher than the 0.7% median delivery efficiency of other systems with sufficient quantitative data to define this metric. These results lay a foundation for targeting intraperitoneal tumors and encourage efforts to explore alternative, nonintravenous routes, of delivery to accelerate the translation of nanoparticle therapies to the clinic.

Pilot-scale production of expansile nanoparticles: Practical methods for clinical scale-up

One of the foremost challenges in translating nanoparticle technologies to the clinic is the requirement to produce materials on a large-scale. Scaling nanoparticle production methods is often non-trivial, and the success of these endeavors is frequently governed by whether or not an intermediate level of production, i.e., “pilot-scale” production, can be achieved. Pilot-scale production at the one-liter scale serves as a proof-of-concept that large-scale production will be possible. Here, we describe the pilot-scale production of the expansile nanoparticle (eNP) technology including verification of activity and efficacy following scaleup. We describe the challenges of sonication-based emulsification procedures and how these were overcome by use of a Microfluidizer technology. We also describe the problem-solving process that led to pre-polymerization of the nanoparticle polymer—a fundamental change from the lab-scale and previously published methods. Furthermore, we demonstrate good control over particle diameter, polydispersity and drug loading and the ability to sterilize the particles via filtration using this method. To facilitate long-term storage of these larger quantities of particles, we investigated six lyoprotectants and determined that sucrose is the most compatible with the current system. Lastly, we demonstrate that these changes to the manufacturing method do not adversely affect the swelling functionality of the particles, their highly specific localization to tumors, their non-toxicity in vivo or their efficacy in treating established intraperitoneal mesothelioma xenografts.

Expansile Nanoparticles Encapsulate Factor Quinolinone Inhibitor 1 and Accumulate in Murine Liver upon Intravenous Administration.

Expansile nanoparticles (eNPs) are a promising pH-responsive polymeric drug delivery vehicle, as demonstrated in multiple intraperitoneal cancer models. However, previous delivery routes were limited to intraperitoneal injection and to a single agent, paclitaxel. In this study, we preliminarily evaluate the biodistribution and in vivo toxicity of eNPs in mice after intravenous injection. The eNPs localize predominantly to the liver, without detectable acute toxicity in the liver or other key organs. On the basis of these results, we encapsulated FQI1, a promising lead compound for treatment of hepatocellular carcinoma, in eNPs. eNPs are taken up by cancerous and noncancerous human liver cells in vitro, although at different rates. FQI1-loaded eNPs release FQI1 in a pH-dependent manner and limit proliferation equivalently to unencapsulated FQI1 in immortalized hepatocytes in vitro. eNPs are a versatile platform delivery system for therapeutic compounds and have potential utility in the treatment of liver disease.

Paclitaxel-loaded expansile nanoparticles improve survival following cytoreductive surgery in pleural mesothelioma xenografts

ObjectiveMalignant pleural mesothelioma is a lethal malignancy with poor survival and high local recurrence rates despite multimodal therapy with cytoreduction and chemoradiation. We evaluated the antitumor efficacy of a paclitaxel-loaded pH-responsive expansile nanoparticle (PTX-eNP) in 2 clinically relevant murine xenograft models of malignant pleural mesothelioma. MethodsLuciferase-transfected MSTO-211H human mesothelioma cells were injected into the thoracic cavity of immunodeficient Nu/J mice. Tumor burden was monitored by bioluminescent imaging. Animals were randomized into 2 models of disease treatment chemotherapy with PTX-eNPs alone delivered locally for early limited disease or cytoreductive surgery plus local PTX-eNP chemotherapy for advanced disease. Within each disease model, anti-tumor efficacy of PTX-eNP was compared against standard formulation paclitaxel and drug-empty nanoparticles. Influence on survival was calculated. Fluorescently labeled PTX-eNPs and immunohistochemistry evaluated in vivo drug localization to tumor. ResultsIntrathoracic injection of MSTO-211H resulted in large tumor deposits distributed within the pleural space of the murine thoracic cavity. Local multidose treatment with PTX-eNPs alone in limited stage disease more than doubled survival compared with drug-empty nanoparticles (P ≤ .0001) and standard formulation paclitaxel (P = .0004). In the model of advanced disease, local multidose treatment with PTX-eNPs following cytoreductive surgery also prolonged survival by 126% and 69.4% compared with drug-empty nanoparticles (P = .0018) and standard formulation paclitaxel (P = .03457), respectively. Immunohistology demonstrated PTX-eNP accumulation within tumor cells in vitro and in vivo. ConclusionsLocal delivery of paclitaxel via eNPs confers prolonged survival in a murine model of malignant pleural mesothelioma as single modality treatment for limited disease and in combination with cytoreductive surgery for advanced disease.

Verticillin A Causes Apoptosis and Reduces Tumor Burden in High-Grade Serous Ovarian Cancer by Inducing DNA Damage

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy in women worldwide and the fifth most common cause of cancer-related deaths among U.S. women. New therapies are needed to treat HGSOC, particularly because most patients develop resistance to current first-line therapies. Many natural product and fungal metabolites exhibit anticancer activity and represent an untapped reservoir of potential new agents with unique mechanism(s) of action. Verticillin A, an epipolythiodioxopiperazine alkaloid, is one such compound, and our recent advances in fermentation and isolation are now enabling evaluation of its anticancer activity. Verticillin A demonstrated cytotoxicity in HGSOC cell lines in a dose-dependent manner with a low nmol/L IC50 Furthermore, treatment with verticillin A induced DNA damage and caused apoptosis in HGSOC cell lines OVCAR4 and OVCAR8. RNA-Seq analysis of verticillin A-treated OVCAR8 cells revealed an enrichment of transcripts in the apoptosis signaling and the oxidative stress response pathways. Mass spectrometry histone profiling confirmed reports that verticillin A caused epigenetic modifications with global changes in histone methylation and acetylation marks. To facilitate in vivo delivery of verticillin A and to monitor its ability to reduce HGSOC tumor burden, verticillin A was encapsulated into an expansile nanoparticle (verticillin A-eNP) delivery system. In an in vivo human ovarian cancer xenograft model, verticillin A-eNPs decreased tumor growth and exhibited reduced liver toxicity compared with verticillin A administered alone. This study confirmed that verticillin A has therapeutic potential for treatment of HGSOC and that encapsulation into expansile nanoparticles reduced liver toxicity.

Cover Image, Volume 9, Issue 3

image The cover image, by Aaron H. Colby et al., is based on the Advanced Review Nanoparticle drug‐delivery systems for peritoneal cancers: a case study of the design, characterization and development of the expansile nanoparticle, DOI: 10.1002/wnan.1451.

Nanoparticle drug-delivery systems for peritoneal cancers: a case study of the design, characterization and development of the expansile nanoparticle.

Nanoparticle (NP)-based drug-delivery systems are frequently employed to improve the intravenous administration of chemotherapy; however, few reports explore their application as an intraperitoneal therapy. We developed a pH-responsive expansile nanoparticle (eNP) specifically designed to leverage the intraperitoneal route of administration to treat intraperitoneal malignancies, such as mesothelioma, ovarian, and pancreatic carcinomatoses. This review describes the design, evaluation, and evolution of the eNP technology and, specifically, a Materials-Based Targeting paradigm that is unique among the many active- and passive-targeting strategies currently employed by NP-delivery systems. pH-responsive eNP swelling is responsible for the extended residence at the target tumor site as well as the subsequent improvement in tumoral drug delivery and efficacy observed with paclitaxel-loaded eNPs (PTX-eNPs) compared to the standard clinical formulation of paclitaxel, Taxol®. Superior PTX-eNP efficacy is demonstrated in two different orthotopic models of peritoneal cancer-mesothelioma and ovarian cancer; in a third model-of pancreatic cancer-PTX-eNPs demonstrated comparable efficacy to Taxol with reduced toxicity. Furthermore, the unique structural and responsive characteristics of eNPs enable them to be used in three additional treatment paradigms, including: treatment of lymphatic metastases in breast cancer; use as a highly fluorescent probe to visually guide the resection of peritoneal implants; and, in a two-step delivery paradigm for concentrating separately administered NP and drug at a target site. This case study serves as an important example of using the targeted disease-state's pathophysiology to inform the NP design as well as the method of use of the delivery system. WIREs Nanomed Nanobiotechnol 2017, 9:e1451. doi: 10.1002/wnan.1451 For further resources related to this article, please visit the WIREs website.

Highly Specific and Sensitive Fluorescent Nanoprobes for Image-Guided Resection of Sub-Millimeter Peritoneal Tumors.

A current challenge in the treatment of peritoneal carcinomatosis is the inability to detect, visualize, and resect small or microscopic tumors of pancreatic, ovarian, or mesothelial origin. In these diseases, the completeness of primary tumor resection is directly correlated with patient survival, and hence, identifying small sub-millimeter tumors (i.e., disseminated disease) is critical. Thus, new imaging techniques and probes are needed to improve cytoreductive surgery and patient outcomes. Highly fluorescent rhodamine-labeled expansile nanoparticles (HFR-eNPs) are described for use as a visual aid during cytoreductive surgery of pancreatic carcinomatosis. The covalent incorporation of rhodamine into ∼30 nm eNPs increases the fluorescent signal compared to free rhodamine, thereby affording a brighter and more effective probe than would be achieved by a single rhodamine molecule. Using the intraperitoneal route of administration, HFR-eNPs localize to regions of large (∼1 cm), sub-centimeter, and sub-millimeter intraperitoneal tumor in three different animal models, including pancreatic, mesothelioma, and ovarian carcinoma. Tumoral localization of the HFR-eNPs depends on both the material property (i.e., eNP polymer) as well as the surface chemistry (anionic surfactant vs PEGylated noncharged surfactant). In a rat model of pancreatic carcinomatosis, HFR-eNP identification of tumor is validated against gold-standard histopathological analysis to reveal that HFR-eNPs possess high specificity (99%) and sensitivity (92%) for tumors, in particular, sub-centimeter and microscopic sub-millimeter tumors, with an overall accuracy of 95%. Finally, as a proof-of-concept, HFR-eNPs are used to guide the resection of pancreatic tumors in a rat model of peritoneal carcinomatosis.

Tunable resistive pulse sensing and nanoindentation of pH-responsive expansile nanoparticles

Experimental studies of pH-responsive expansile nanoparticles (eNPs) have been carried out using tunable resistive pulse sensing (TRPS) and nanoindentation. The eNPs are initially ∼200 nm in diameter, but increase in size owing to a compositional change resulting from cleavage of pH-labile protecting groups on the polymer backbone at low pH. TRPS detected expected changes in the size of eNPs, most clearly through an increase in the size distribution close to ∼1 μm diameter with time after exposure to pH 5.0 electrolyte. Heavily cross-linked nanoparticles and eNPs kept at neutral pH did not produce such pronounced changes. Nanoindentation results demonstrate that for accurate measurement of eNP mechanical properties, particles must be precisely located and securely fixed to the substrate. Moreover, the expanded eNPs may be too weak to respond to conventional nanoindentation. Nanoscale physical characterisation of soft matter is of burgeoning importance in medical and biotechnological research and applications.

Tunable resistive pulse sensing and nanoindentation of pH-responsive expansile nanoparticles

Experimental studies of pH-responsive expansile nanoparticles (eNPs) have been carried out using tunable resistive pulse sensing (TRPS) and nanoindentation. The eNPs are initially ∼200 nm in diameter, but increase in size owing to a compositional change resulting from cleavage of pH-labile protecting groups on the polymer backbone at low pH. TRPS detected expected changes in the size of eNPs, most clearly through an increase in the size distribution close to ∼1 μm diameter with time after exposure to pH 5.0 electrolyte. Heavily cross-linked nanoparticles and eNPs kept at neutral pH did not produce such pronounced changes. Nanoindentation results demonstrate that for accurate measurement of eNP mechanical properties, particles must be precisely located and securely fixed to the substrate. Moreover, the expanded eNPs may be too weak to respond to conventional nanoindentation. Nanoscale physical characterisation of soft matter is of burgeoning importance in medical and biotechnological research and applications.

Nanoparticle tumor localization, disruption of autophagosomal trafficking, and prolonged drug delivery improve survival in peritoneal mesothelioma.

The treatment outcomes for malignant peritoneal mesothelioma are poor and associated with high co-morbidities due to suboptimal drug delivery. Thus, there is an unmet need for new approaches that concentrate drug at the tumor for a prolonged period of time yielding enhanced antitumor efficacy and improved metrics of treatment success. A paclitaxel-loaded pH-responsive expansile nanoparticle (PTX-eNP) system is described that addresses two unique challenges to improve the outcomes for peritoneal mesothelioma. First, following intraperitoneal administration, eNPs rapidly and specifically localize to tumors. The rate of eNP uptake by tumors is an order of magnitude faster than the rate of uptake in non-malignant cells; and, subsequent accumulation in autophagosomes and disruption of autophagosomal trafficking leads to prolonged intracellular retention of eNPs. The net effect of these combined mechanisms manifests as rapid localization to intraperitoneal tumors within 4h of injection and persistent intratumoral retention for >14 days. Second, the high tumor-specificity of PTX-eNPs leads to delivery of greater than 100 times higher concentrations of drug in tumors compared to PTX alone and this is maintained for at least seven days following administration. As a result, overall survival of animals with established mesothelioma more than doubled when animals were treated with multiple doses of PTX-eNPs compared to equivalent dosing with PTX or non-responsive PTX-loaded nanoparticles.

Evaluation of expansile nanoparticle tumor localization and efficacy in a cancer stem cell-derived model of pancreatic peritoneal carcinomatosis.

To evaluate the tumor localization and efficacy pH-responsive expansile nanoparticles (eNPs) as a drug delivery system for pancreatic peritoneal carcinomatosis (PPC) modeled in nude rats. A Panc-1-cancer stem cell xeno1graft model of PPC was validated in vitro and in vivo. Tumor localization was tracked via in situ imaging of fluorescent eNPs. Survival of animals treated with paclitaxel-loaded eNPs (PTX-eNPs) was evaluated in vivo. The Panc-1-cancer stem cell xenograft model recapitulates significant features of PPC. Rhodamine-labeled eNPs demonstrate tumor-specific, dose- and time-dependent localization to macro- and microscopic tumors following intraperitoneal injection. PTX-eNPs are as effective as free PTX in treating established PPC; but, PTX-eNPs result in fewer side effects. eNPs are a promising tool for the detection and treatment of PPC.

Synthesis and Characterization of Hybrid Polymer/Lipid Expansile Nanoparticles: Imparting Surface Functionality for Targeting and Stability.

The size, drug loading, drug release kinetics, localization, biodistribution, and stability of a given polymeric nanoparticle (NP) system depend on the composition of the NP core as well as its surface properties. In this study, novel, pH-responsive, and lipid-coated NPs, which expand in size from a diameter of approximately 100 to 1000 nm in the presence of a mildly acidic pH environment, are synthesized and characterized. Specifically, a combined miniemulsion and free-radical polymerization method is used to prepare the NPs in the presence of PEGylated lipids. These PEGylated-lipid expansile NPs (PEG-L-eNPs) combine the swelling behavior of the polymeric core of expansile NPs with the improved colloidal stability and surface functionality of PEGylated liposomes. The surface functionality of PEG-L-eNPs allows for the incorporation of folic acid (FA) and folate receptor-targeting. The resulting hybrid polymer/lipid nanocarriers, FA-PEG-L-eNPs, exhibit greater in vitro uptake and potency when loaded with paclitaxel compared to nontargeted PEG-L-eNPs.

Paclitaxel-loaded expansile nanoparticles enhance chemotherapeutic drug delivery in mesothelioma 3-dimensional multicellular spheroids

ObjectivesIntraperitoneal administration of paclitaxel-loaded expansile nanoparticles (Pax-eNPs) significantly improves survival in an in vivo model of malignant mesothelioma compared with conventional drug delivery with the clinically utilized Cremophor EL/ethanol (C/E) excipient. However, in vitro monolayer cell culture experiments do not replicate this superior efficacy, suggesting Pax-eNPs utilize a unique mechanism of drug delivery. Using a mesothelioma spheroid model, we characterized the mechanisms of enhanced tumor cytotoxicity leveraged by Pax-eNPs. MethodsHuman malignant mesothelioma (MSTO-211H) spheroids were co-incubated for 24 hours with Oregon Green-conjugated paclitaxel dissolved in C/E or loaded into eNPs. Oregon Green-paclitaxel uptake was measured as Oregon Green intensity via confocal microscopy and kinetics of tumor cytotoxicity were assessed via propidium iodide staining. Pharmacologic endocytotic inhibitors were used to elucidate mechanisms of eNP uptake into spheroids. ResultsIncreased drug penetration and a 38-fold higher intraspheroidal drug concentration were observed 24 hours after MSTO-211H spheroids were treated with Oregon Green-conjugated paclitaxel loaded into eNPs compared with Oregon Green-conjugated paclitaxel dissolved in C/E (P < .01). Macropinocytosis was the dominant endocytotic pathway of eNP uptake. Spheroids were more susceptible to paclitaxel when delivered via eNP, exhibiting more than twice the propidium iodine intensity compared with an equivalent paclitaxel-C/E dose. ConclusionsCompared with monolayer cell culture, the in vitro 3-D tumor spheroid model better reflects the superior in vivo efficacy of Pax-eNPs. Persistent tumor penetration and prolonged intratumoral release are unique mechanisms of Pax-eNP cytotoxicity. 3-D spheroid models are valuable tools for investigating cytotoxic mechanisms and nanoparticle-tumor interactions, particularly given the costs and limitations of in vivo animal studies.

Embedded multicellular spheroids as a biomimetic 3D cancer model for evaluating drug and drug-device combinations

Multicellular aggregates of cells, termed spheroids, are of interest for studying tumor behavior and for evaluating the response of pharmacologically active agents. Spheroids more faithfully reproduce the tumor macrostructure found in vivo compared to classical 2D monolayers. We present a method for embedding spheroids within collagen gels followed by quantitative and qualitative whole spheroid and single cell analyses enabling characterization over the length scales from molecular to macroscopic. Spheroid producing and embedding capabilities are demonstrated for U2OS and MDA-MB-231 cell lines, of osteosarcoma and breast adenocarcinoma origin, respectively. Finally, using the MDA-MB-231 tumor model, the chemotherapeutic response between paclitaxel delivery as a bolus dose, as practiced in the clinic, is compared to delivery within an expansile nanoparticle. The expansile nanoparticle delivery route provides a superior outcome and the results mirror those observed in a murine xenograft model. These findings highlight the synergistic beneficial results that may arise from the use of a drug delivery system, and the need to evaluate both drug candidates and delivery systems in the research and preclinical screening phases of a new cancer therapy development program.

In vitro activity of Paclitaxel-loaded polymeric expansile nanoparticles in breast cancer cells.

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 colocalization.

Microscopy and tunable resistive pulse sensing characterization of the swelling of pH-responsive, polymeric expansile nanoparticles.

Polymeric expansile nanoparticles (eNPs) that respond to a mildly acidic environment by swelling with water and expanding 2-10× in diameter represent a new responsive drug delivery system. Here, we use a variety of techniques to characterize the pH- and time-dependence of eNP swelling as this is a key property responsible for the observed in vitro and in vivo performance of eNPs. Results demonstrate a significant change in eNP volume (>350×) at pH 5.0 as seen using: scanning electron microscopy (SEM), conventional transmission electron microscopy (TEM), freeze-fracture transmission electron microscopy (ff-TEM), fluorescence microscopy, and a new nanopore based characterization technology, the qNano, which measures both individual particle size as well as overall particle concentration in situ using tunable resistive pulse sensing. eNP swelling occurs in a continuous and yet heterogeneous manner over several days and is pH dependent.

Prevention of nodal metastases in breast cancer following the lymphatic migration of paclitaxel-loaded expansile nanoparticles

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.

Cytoreductive Surgery and Intraoperative Administration of Paclitaxel-loaded Expansile Nanoparticles Delay Tumor Recurrence in Ovarian Carcinoma

Locoregional recurrence significantly impacts survival and quality of life in patients with ovarian carcinoma. We hypothesize that local administration of paclitaxel-loaded expansile nanoparticles (pax-eNP) at the time of cytoreductive surgery decreases local tumor recurrence. In vitro cytotoxicity of pax-eNP was assessed against both the OVCAR-3 human ovarian cancer cell line and tumor cells isolated from a malignant pleural effusion from a patient with multidrug-resistant ovarian cancer. A murine xenogenic model involving surgical cytoreduction of established OVCAR-3 intra-abdominal tumor was used to evaluate in vivo efficacy of intraoperative intraperitoneal (IP) injection of 10 mg/kg of paclitaxel either as pax-eNP or paclitaxel in Cremophor EL/ethanol solution (pax-C/E) versus empty eNP controls. Cytoreductive surgery and intraoperative treatment were performed 4 weeks after established tumor. All animals were sacrificed when empty eNP controls displayed extensive evidence of disease progression. Labeled-eNP entered tumor cells in vitro within 4 h and specifically accumulated at sites of tumor in vivo. Pax-eNP exhibited dose-dependent cytotoxicity in both OVCAR-3 and patient tumor cells isolated from a malignant pleural effusion and effectively prevented tumor recurrence following debulking (p = 0.003 vs. empty eNP). Furthermore, pax-eNP-treated animals did not develop severe recurrent carcinomatosis compared with 43 % of the pax-C/E-treated cohort, suggesting that single-dose intracavitary pax-eNP is more effective than an equivalent dose of pax-C/E. 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.

Hydrogels as Intracellular Depots for Drug Delivery

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.