Growth and Characterization of Irradiated Organoids from Mammary Glands.

Organoids derived from the digested tissue are multicellular three-dimensional (3D) constructs that better recapitulate in vivo conditions than cell monolayers. Although they cannot completely model in vivo complexity, they retain some functionality of the original organ. In cancer models, organoids are commonly used to study tumor cell invasion. This protocol aims to develop and characterize organoids from the normal and irradiated mouse mammary gland tissue to evaluate the radiation response in normal tissues. These organoids can be applied to future in vitro cancer studies to evaluate tumor cell interactions with irradiated organoids. Mammary glands were resected, irradiated to 20 Gy and digested in a collagenase VIII solution. Epithelial organoids were separated via centrifugal differentiation, and 3D organoids were developed in 96-well low-adhesion microplates. Organoids expressed the characteristic epithelial marker cytokeratin 14. Macrophage interaction with the organoids was observed in co-culture experiments. This model may be useful for studying tumor-stromal interactions, infiltration of immune cells, and macrophage polarization within an irradiated microenvironment.

Nonadditivity of nanoparticle interactions.

Understanding interactions between inorganic nanoparticles (NPs) is central to comprehension of self-organization processes and a wide spectrum of physical, chemical, and biological phenomena. However, quantitative description of the interparticle forces is complicated by many obstacles that are not present, or not as severe, for microsize particles (µPs). Here we analyze the sources of these difficulties and chart a course for future research. Such difficulties can be traced to the increased importance of discreteness and fluctuations around NPs (relative to µPs) and to multiscale collective effects. Although these problems can be partially overcome by modifying classical theories for colloidal interactions, such an approach fails to manage the nonadditivity of electrostatic, van der Waals, hydrophobic, and other interactions at the nanoscale. Several heuristic rules identified here can be helpful for discriminating between additive and nonadditive nanoscale systems. Further work on NP interactions would benefit from embracing NPs as strongly correlated reconfigurable systems with diverse physical elements and multiscale coupling processes, which will require new experimental and theoretical tools. Meanwhile, the similarity between the size of medium constituents and NPs makes atomic simulations of their interactions increasingly practical. Evolving experimental tools can stimulate improvement of existing force fields. New scientific opportunities for a better understanding of the electronic origin of classical interactions are converging at the scale of NPs.

Rod hydrodynamics and length distributions of single-wall carbon nanotubes using analytical ultracentrifugation.

Because of their repetitive chemical structure, extreme rigidity, and the separability of populations with varying aspect ratio, SWCNTs are excellent candidates for use as model rodlike colloids. In this contribution, the sedimentation velocities of length and density sorted single-wall carbon nanotubes (SWCNTs) are compared to predictions from rod hydrodynamic theories of increasing complexity over a range of aspect ratios from <50 to >400. Independently measuring all contributions to the sedimentation velocity besides the shape factor, excellent agreement is found between the experimental findings and theoretical predictions for numerically calculated hydrodynamic radius values and for multiterm analytical expansion approximations; values for the hydrodynamic radii in these cases are additionally found to be consistent with the apparent hydrated particle radius determined independently by buoyancy measurements. Lastly, we utilize this equivalency to calculate the apparent distribution of nanotube lengths in each population from their sedimentation coefficient distribution without adjustable parameters, achieving excellent agreement with distributions from atomic force microscopy. The method developed herein provides an alternative for the ensemble measurement of SWCNT length distributions and others rodlike particles.