Lisa Bauer

Enhanced Delivery of Chemotherapy to Tumors Using a Multicomponent Nanochain with Radio-Frequency-Tunable Drug Release

While nanoparticles maximize the amount of chemotherapeutic drug in tumors relative to normal tissues, nanoparticle-based drugs are not accessible to the majority of cancer cells because nanoparticles display patchy, near-perivascular accumulation in tumors. To overcome the limitations of current drugs in their molecular or nanoparticle form, we developed a nanoparticle based on multicomponent nanochains to deliver drug to the majority of cancer cells throughout a tumor while reducing off-target delivery. The nanoparticle is composed of three magnetic nanospheres and one doxorubicin-loaded liposome assembled in a 100 nm long chain. These nanoparticles display prolonged blood circulation and significant intratumoral deposition in tumor models in rodents. Furthermore, the magnetic particles of the chains serve as a mechanical transducer to transfer radio frequency energy to the drug-loaded liposome. The defects on the liposomal walls trigger the release of free drug capable of spreading throughout the entire tumor, which results in a widespread anticancer effect.

Targeted nanotechnology for cancer imaging.

Targeted nanoparticle imaging agents provide many benefits and new opportunities to facilitate accurate diagnosis of cancer and significantly impact patient outcome. Due to the highly engineerable nature of nanotechnology, targeted nanoparticles exhibit significant advantages including increased contrast sensitivity, binding avidity and targeting specificity. Considering the various nanoparticle designs and their adjustable ability to target a specific site and generate detectable signals, nanoparticles can be optimally designed in terms of biophysical interactions (i.e., intravascular and interstitial transport) and biochemical interactions (i.e., targeting avidity towards cancer-related biomarkers) for site-specific detection of very distinct microenvironments. This review seeks to illustrate that the design of a nanoparticle dictates its in vivo journey and targeting of hard-to-reach cancer sites, facilitating early and accurate diagnosis and interrogation of the most aggressive forms of cancer. We will report various targeted nanoparticles for cancer imaging using X-ray computed tomography, ultrasound, magnetic resonance imaging, nuclear imaging and optical imaging. Finally, to realize the full potential of targeted nanotechnology for cancer imaging, we will describe the challenges and opportunities for the clinical translation and widespread adaptation of targeted nanoparticles imaging agents.

Treatment of invasive brain tumors using a chain-like nanoparticle

Glioblastoma multiforme is generally recalcitrant to current surgical and local radiotherapeutic approaches. Moreover, systemic chemotherapeutic approaches are impeded by the blood-tumor barrier. To circumvent limitations in the latter area, we developed a multicomponent, chain-like nanoparticle that can penetrate brain tumors, composed of three iron oxide nanospheres and one drug-loaded liposome linked chemically into a linear chain-like assembly. Unlike traditional small-molecule drugs or spherical nanotherapeutics, this oblong-shaped, flexible nanochain particle possessed a unique ability to gain access to and accumulate at glioma sites. Vascular targeting of nanochains to the αvβ3 integrin receptor resulted in a 18.6-fold greater drug dose administered to brain tumors than standard chemotherapy. By 2 hours after injection, when nanochains had exited the blood stream and docked at vascular beds in the brain, the application of an external low-power radiofrequency field was sufficient to remotely trigger rapid drug release. This effect was produced by mechanically induced defects in the liposomal membrane caused by the oscillation of the iron oxide portion of the nanochain. In vivo efficacy studies conducted in two different mouse orthotopic models of glioblastoma illustrated how enhanced targeting by the nanochain facilitates widespread site-specific drug delivery. Our findings offer preclinical proof-of-concept for a broadly improved method for glioblastoma treatment.

Treatment of cancer micrometastasis using a multicomponent chain-like nanoparticle

While potent cytotoxic agents are available to oncologists, the clinical utility of these agents is limited due to their non-specific distribution in the body and toxicity to normal tissues leading to use of suboptimal doses for eradication of metastatic disease. Furthermore, treatment of micrometastases is impeded by several biobarriers, including their small size and high dispersion to organs, making them nearly inaccessible to drugs. To circumvent these limitations in treating metastatic disease, we developed a multicomponent, flexible chain-like nanoparticle (termed nanochain) that possesses a unique ability to gain access to and be deposited at micrometastatic sites. Moreover, coupling nanochain particles to radiofrequency (RF)-triggered cargo delivery facilitated widespread delivery of drug into hard-to-reach cancer cells. Collectively, these features synergistically facilitate effective treatment and ultimately eradication of micrometastatic disease using a low dose of a cytotoxic drug.

Magnetic Particle Imaging Tracers: State-of-the-Art and Future Directions.

Magnetic particle imaging (MPI) is an emerging imaging modality with promising applications in diagnostic imaging and guided therapy. The image quality in MPI is strongly dependent on the nature of its iron oxide nanoparticle-based tracers. The selection of potential MPI tracers is currently limited, and the underlying physics of tracer response is not yet fully understood. An in-depth understanding of the magnetic relaxation processes that govern MPI tracers, gained through concerted theoretical and experimental work, is crucial to the development of optimized MPI tracers. Although tailored tracers will lead to improvements in image quality, tailored relaxation may also be exploited for biomedical applications or more flexible image contrast, as in the recent demonstration of color MPI.

Modeling the Brownian relaxation of nanoparticle ferrofluids: Comparison with experiment

We obtain good agreement between the calculated and measured ratio of harmonics only when the model includes nanoparticles which have a distribution in the hydrodynamic diameter - that is polydisperse. We are unable to find good agreement if the diameter of the nanoparticles is constrained to only one value - that is monodisperse. In Fig. 1 we plot the measured [3] ratios of 5th/3rd harmonics of the magnetization for samples using “100 nm” iron oxide particles (top plot) and “40 nm” iron oxide particles (bottom plot). The measurements were collected with the nanoparticles in ferrofluid solutions with a range of water/glycerol ratios corresponding to different viscosities (and therefore different Brownian relaxation times.) As described in [3] the data are plotted as a function of ωτB. Also shown in Fig. 1 are the calculations of the ratios of 5th/3rd harmonics assuming both monodisperse and polydisperse ferrofluids. Details of the calculations and parameters used in the models can be found in [5].

Vascular targeting of nanoparticles for molecular imaging of diseased endothelium.

&NA; This review seeks to highlight the enormous potential of targeted nanoparticles for molecular imaging applications. Being the closest point‐of‐contact, circulating nanoparticles can gain direct access to targetable molecular markers of disease that appear on the endothelium. Further, nanoparticles are ideally suitable to vascular targeting due to geometrically enhanced multivalent attachment on the vascular target. This natural synergy between nanoparticles, vascular targeting and molecular imaging can provide new avenues for diagnosis and prognosis of disease with quantitative precision. In addition to the obvious applications of targeting molecular signatures of vascular diseases (e.g., atherosclerosis), deep‐tissue diseases often manifest themselves by continuously altering and remodeling their neighboring blood vessels (e.g., cancer). Thus, the remodeled endothelium provides a wide range of targets for nanoparticles and molecular imaging. To demonstrate the potential of molecular imaging, we present a variety of nanoparticles designed for molecular imaging of cancer or atherosclerosis using different imaging modalities.

Magnetic particle spectroscopy of magnetite-polyethylene nanocomposite films: A novel sample for MPI tracer design

Several harmonic spectra are plotted in Figure 2. An important result is the comparison of free particles embedded in agar and films (Figure 2c). The particles embedded in the films are “frozen” in place, while those in agar, unless bound within the matrix, should still have some freedom to rotate. Particles in both should have identical Neel relaxation times, as that is dependent only on the structure of the iron core and not local environment, provided magnetic interactions can be excluded. A calculation of the Neel relaxation time yields values in the range of 0.12-171 microseconds (for crystal anisotropies in the range of 11-21kJ/m3). The Brownian relaxation time for the films is assumed to be infinite, such that relaxation is only possible through the Neel mechanism. However, the Brownian relaxation times for particles in agar are long enough that relaxation is also assumed to be dominated by the Neel mechanism. While Brownian relaxation may play a role in explaining the signal difference, it is likely due to magnetic interactions between neighboring particles that steepen the magnetization curve. Figure 2c demonstrates that a low interparticle distance generally results in a higher signal. In samples with high local concentrations (such as the films presented here, or samples that exhibit significant aggregation), the average distance between two particles is small enough that dipole-dipole interactions must be considered. Such interactions are one possible explanation for the performance of Feridex IV and Resovist.

Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization

The development of magnetic particle imaging (MPI) has created a need for optimized magnetic nanoparticles. Magnetic particle relaxometry is an excellent tool for characterizing potential tracers for MPI. In this paper, we describe the design and construction of a high-throughput tabletop relaxometer that is able to make sensitive measurements of MPI tracers without the need for a dedicated shield room.

Abstract 1473: CXCL12 inhibition with NOX-A12 (olaptesed pegol) increases T-cell infiltration in tumor-stroma spheroids and synergizes with PD-1 immune checkpoint blockade

Immune checkpoint inhibition promotes T cell-mediated killing of cancer cells and can induce striking responses, but objective control of tumor growth is observed in only 10-30% of patients with cancer types that generally respond to this treatment (Fearon 2014, Cancer Immunol Res 2:187). A possible cause for this limitation of checkpoint inhibition may be an immune-privileged tumor microenvironment (TME) which excludes the cytotoxic T cells from the vicinity of cancer cells. The chemokine CXCL12 has recently been described as an important T cell exclusion factor in the TME-driven immune suppression. In this study we aimed to investigate whether CXCL12 inhibition by the clinical stage L-aptamer (Spiegelmer®) NOX-A12 (olaptesed pegol) is able to enhance T cell infiltration in 3D tumor-stroma spheroids, thereby facilitating effective immunotherapy. We established 3D multicellular microtissues that mimic a solid tumor with a CXCL12-abundant TME. For this purpose, CXCL12-expressing murine stromal MS-5 cells were co-cultured with solid human cancer cell lines in ultra-low attachment plates for three days. Primary human T cells isolated from healthy donors were added to the spheroids in the presence of various concentrations of NOX-A12. The next day, spheroids were washed and dissociated for T cell quantification by flow cytometry. T cell localization in the 3D microtissues was assessed by immunohistochemistry (IHC). In order to examine T cell activation in the spheroids, a bioluminescent reporter-based PD-1/PD-L1 blockade bioassay (Promega) was adapted to the 3D format: Jurkat-PD-1/Luc T cells were incubated with anti-PD-1 and added to NOX-A12-treated spheroids (CHO-PD-L1 + MS-5). We found that NOX-A12 increases the amount of T cells in tumor-stroma spheroids in a dose-dependent manner; flow cytometry analyses revealed a 2-3 fold increase in spheroid T cell infiltration at 10 nM NOX-A12 in all examined 3D co-culture types. Enhanced T cell infiltration in the presence of NOX-A12 was corroborated by IHC. In line with this, we found increased infiltration and activation of Jurkat-PD-1/luc T cells in the MS-5/CHO-PD-L1 spheroids treated with NOX-A12. Importantly, NOX-A12 synergized with anti-PD1-induced T cell activation. Taken together, in heterotypic 3D models that mimic the complexity of the TME, the CXCL12 antagonist NOX-A12 improved T cell-based tumor immunotherapy by increasing T cell infiltration. By modulating the CXCL12 gradients within the complex 3D structure, NOX-A12 appears to break the immune-privilege of the TME, thereby paving the way for T cell migration into the tumor. These data provide a rationale for the combination of NOX-A12 with checkpoint inhibitors as well as other T cell-based therapies in patients with solid cancer. Citation Format: Dirk Zboralski, Lisa Bauer, Dirk Eulberg, Axel Vater. CXCL12 inhibition with NOX-A12 (olaptesed pegol) increases T-cell infiltration in tumor-stroma spheroids and synergizes with PD-1 immune checkpoint blockade. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1473.