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Surface-induced phase transition of asymmetric diblock copolymer in selective solvents is first theoretically investigated by using the real-space version of self-consistent field theory (SCFT). By varying the distance between two parallel hard surfaces (or the film thickness) Wand the block copolymer concentration fp, several morphologies are predicted and the phase diagram is constructed. Self-assembly morphologies of the diblock copolymer in dilute solution are found to change significantly with different film thickness. In confined systems, stable morphologies found in the bulk solution become unstable due to the loss of polymer conformation entropy. We find that in a very dilute block copolymer solution, phase separation can be induced through polymer depletion as the solution becomes more confined. Our findings provide an interesting starting point for a renewed effort in both experimental and theoretical investigations of confined block copolymer solutions. [ABSTRACT FROM AUTHOR]

Multicellular aggregates of circulating tumor cells (CTC clusters) are potent initiators of distant organ metastasis. However, it is currently assumed that CTC clusters are too large to pass through narrow vessels to reach these organs. Here, we present evidence that challenges this assumption through the use of microfluidic devices designed to mimic human capillary constrictions and CTC clusters obtained from patient and cancer cell origins. Over 90% of clusters containing up to 20 cells successfully traversed 5- to 10-µm constrictions even in whole blood. Clusters rapidly and reversibly reorganized into single-file chain-like geometries that substantially reduced their hydrodynamic resistances. Xenotransplantation of human CTC clusters into zebrafish showed similar reorganization and transit through capillary-sized vessels in vivo. Preliminary experiments demonstrated that clusters could be disrupted during transit using drugs that affected cellular interaction energies. These findings suggest that CTC clusters may contribute a greater role to tumor dissemination than previously believed and may point to strategies for combating CTC cluster-initiated metastasis. [ABSTRACT FROM AUTHOR]

The translocation process of star polymers through a nanochannel is investigated by dissipative particle dynamics simulations. The translocation process is strongly influenced by the star arm arrangement as the polymer enters the channel, and a scaling relation between the translocation time s and the total number of beads Ntot is obtained. Qualitative agreements are found with predictions of the nucleation and growth model for linear block co-polymer translocation. In the intermediate stage where the center of the star polymer is at the channel entrance, the translocation time is found to have power law-dependence on the number of arms outside the channel and very weakly dependent on the number of arms in the channel. Increasing the total number of star arms also increases the star translocation time. [ABSTRACT FROM AUTHOR]