Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties to improve relaxivity and to enhance image contrast. Here, we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudinal proton relaxivity r₁ was observed: Magnevist, r₁ ≈ 14 mM⁻¹ s⁻¹/Gd³⁺ ion (∼8.15 × 10⁺⁷ mM⁻¹ s⁻¹/construct); gadofullerenes, r₁ ≈ 200 mM⁻¹ s⁻¹/Gd³⁺ ion (∼7 × 10⁺⁹ mM⁻¹ s⁻¹/construct); gadonanotubes, r₁ ≈ 150 mM⁻¹ s⁻¹/Gd³⁺ ion (∼2 × 10⁺⁹ mM⁻¹ s⁻¹/construct). These relaxivity values are about 4 to 50 times larger than those of clinically available gadolinium-based agents (∼4 mM⁻¹ s⁻¹/Gd³⁺ ion). The enhancement in contrast is attributed to the geometrical confinement of the agents, which influences the paramagnetic behaviour of the Gd³⁺ ions. Thus, nanoscale confinement offers a new and general strategy for enhancing the contrast of gadolinium-based contrast agents.

We fabricated a microfluidic device consisting of ciliated micropillars, forming a porous silicon nanowire-on-micropillar structure. We demonstrated that the prototype device can preferentially trap exosome-like lipid vesicles, while simultaneously filtering out proteins and cell debris. Trapped lipid vesicles can be recovered intact by dissolving the porous nanowires in PBS buffer.

In this study, we investigate a novel in vitro model to mimic heterogeneous breast tumors without the use of a scaffold while allowing for cell-cell and tumor-fibroblast interactions. Previous studies have shown that magnetic levitation system under conventional culturing conditions results in the formation of three-dimensional (3D) structures, closely resembling in vivo tissues (fat tissue, vasculature, etc.). Three-dimensional heterogeneous tumor models for breast cancer were designed to effectively model the influences of the tumor microenvironment on drug efficiency. Various breast cancer cells were co-cultured with fibroblasts and then magnetically levitated. Size and cell density of the resulting tumors were measured. The model was phenotypically compared to in vivo tumors and examined for the presence of ECM proteins. Lastly, the effects of tumor stroma in the 3D in vitro model on drug transport and efficiency were assessed. Our data suggest that the proposed 3D in vitro breast tumor is advantageous due to the ability to: (1) form large-sized (millimeter in diameter) breast tumor models within 24 h; (2) control tumor cell composition and density; (3) accurately mimic the in vivo tumor microenvironment; and (4) test drug efficiency in an in vitro model that is comparable to in vivo tumors.