The capillary wall is the chief barrier to tissue entry of therapeutic nanoparticles, thereby dictating their efficacy. Collagen fibers are an important component of capillary walls, affecting leakiness in healthy or tumor vasculature. Using a computational model along with in vivo systems, we compared how collagen structure affects the diffusion flux of a 1-nm chemotherapeutic molecule [doxorubicin (DOX)] and an 80-nm chemotherapy-loaded pegylated liposome (DOX-PLD) in tumor vasculature. We found a direct correlation between the collagen content around a tumor vessel to the permeability of that vessel permeability to DOX-PLD, indicating that collagen content may offer a biophysical marker of extravasation potential of liposomal drug formulations. Our results also suggested that while pharmacokinetics determined the delivery of DOX and DOX-PLD to the same tumor phenotype, collagen content determined the extravasation of DOX-PLD to different tumor phenotypes. Transport physics may provide a deeper view into how nanotherapeutics cross biological barriers, possibly helping explain the balance between biological and physical aspects of drug delivery. Cancer Res; 74(16); 4239–46. ©2014 AACR.

Hollow gold nanoshells are more efficient in heat generation triggered by near infrared laser when they are loaded into porous silicon particles, which results in effective cancer‐cell killing in vitro and in vivo. Collective electromagnetic coupling of nanoconfined hollow gold nanoshells leads to dramatic enhancement of thermal ablation.

This manuscript demonstrates a mechanically robust implantable nanofluidic membrane capable of tunable long-term zero-order release of therapeutic agents in ranges relevant for clinical applications. The membrane, with nanochannels as small as 5 nm, allows for the independent control of both dosage and mechanical strength through the integration of high-density short nanochannels parallel to the membrane surface with perpendicular micro- and macrochannels for interfacing with the ambient solutions. These nanofluidic membranes are created using precision silicon fabrication techniques on silicon-on-insulator substrates enabling exquisite control over the monodispersed nanochannel dimensions and surface roughness. Zero-order release of analytes is achieved by exploiting molecule to surface interactions which dominate diffusive transport when fluids are confined to the nanoscale. In this study we investigate the nanofluidic membrane performance using custom diffusion and gas testing apparatuses to quantify molecular release rate and process uniformity as well as mechanical strength using a gas based burst test. The kinetics of the constrained zero-order release is probed with molecules presenting a range of sizes, charge states, and structural conformations. Finally, an optimal ratio of the molecular hydrodynamic diameter to the nanochannel dimension is determined to assure zero-order release for each tested molecule.

Angiogenesis, a hallmark of cancer, is induced by vascular endothelial growth factor–A (hereafter VEGF). As a result, anti-VEGF therapy is commonly used for cancer treatment. Recent studies have found that VEGF expression is also associated with immune suppression in patients with cancer. This connection has been investigated in preclinical and clinical studies by evaluating the therapeutic effect of combining antiangiogenic reagents with immune therapy. However, the mechanisms of how anti-VEGF strategies enhance immune therapy are not fully understood. We and others have shown selective elevation of VEGFR2 expression on tumor-associated myeloid cells in tumor-bearing animals. Here, we investigated the function of VEGFR2 ⁺ myeloid cells in regulating tumor immunity and found VEGF induced an immunosuppressive phenotype in VEGFR2 ⁺ myeloid cells, including directly upregulating the expression of programmed cell death 1 ligand 1. Moreover, we found that VEGF blockade inhibited the immunosuppressive phenotype of VEGFR2 ⁺ myeloid cells, increased T cell activation, and enhanced the efficacy of immune checkpoint blockade. This study highlights the function of VEGFR2 on myeloid cells and provides mechanistic insight on how VEGF inhibition potentiates immune checkpoint blockade.