We propose and demonstrate a purely optical approach to trap and align particles using the interaction of polarized light with periodic nanostructures to generate enhanced trapping force. With a weakly focused laser beam, we observed efficient trapping and transportation of polystyrene beads with sizes ranging from 10 µm down to 190 nm as well as cancer cell nuclei. In addition, alignment of non-spherical dielectric particles to a 1-D periodic nanostructure was achieved with low laser intensity without attachment to birefringent crystals. Bacterial cells were trapped and aligned with incident optical intensity as low as 17 µW/µm 2 ., "Cyclic mechanical strain regulates the development of engineered smooth muscle tissue," Nat. Biotechnol. 17(10), 979-983 (1999). 2. T. Matsuda, and T. Sugawara, "Control of cell adhesion, migration, and orientation on photochemically microprocessed surfaces," J.

Recently biomechanics of cancer cells, in particular stiffness or elasticity, has been identified as an important factor relating to cancer cell function, adherence, motility, transformation and invasion. We report on the nanomechanical responses of metastatic cancer cells and benign mesothelial cells taken from human body cavity fluids using atomic force microscopy. Following our initial study (Cross et al 2007 Nat. Nanotechnol. 2 780-3), we report on the biophysical properties of patient-derived effusion cells and address the influence of cell morphology on measured cell stiffness. Using a cytocentrifugation method, which yields morphologically indistinguishable cells that can be prepared in 1 min and avoids any possible artifacts due to 12 h ex vivo culture, we find that metastatic tumor cells are more than 80% softer than benign cells with a distribution over six times narrower than that of normal cells. Consistent with our previous study, which yielded distinguishable cell populations based on ex vivo growth and morphological characteristics, our results show it is unlikely that morphology alone is sufficient to explain the difference in elastic moduli for these two cell types. Moreover, analysis of non-specific cell adhesion inherent to tumor and normal cells collected from patients show surface adhesion of tumor cells is ∼33% less adhesive compared to that of normal cells. Our findings indicate that biomechanical-based functional analysis may provide an additional platform for cytological evaluation and diagnosis of cancer in the future.

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Alteration of actin polymerization and loss of actin filaments is a marker of cellular dedifferentiation and early malignant transformation. To study this phenomenon, an in vitro human urothelial model consisting of two cell lines, HUC-PC and MC-T11, were incorporated into the study design. These two cell lines have different malignant transformation potential. The effect of green tea extract (GTE), a potential anticancer agent, on actin remodeling was investigated. Upon exposure to the carcinogen 4-aminobiphenyl (4-ABP), the untransformed HUC-PC undergoes malignant transformation whereas the transformed MC-T11 progresses from noninvasive to invasive tumor. GTE induces actin polymerization in MC-T11 cells in a dose-responsive manner, but this effect is less obvious in the untransformed, more differentiated HUC-PC cells, which natively have higher actin polymerization status. In contrast, GTE antagonizes carcinogen 4-ABP induced actin depolymerization and stress fiber disruption in HUC-PC cells. In MC-T11 cells, GTE inhibits 4-ABP induced motility by increasing cell adhesion and focal adhesion complex formation. The effect of GTE on actin remodeling seems to be mediated by the stimulation of small GTP-binding protein Rho activity, because C3 exoenzyme, a specific inhibitor for Rho, blocks GTEmediated Rho activation and stress fiber formation in MC-T11 cells. This study shows that GTE exerts an effect on cytoskeletal actin remodeling and provides further support for the use of GTE as a chemopreventive agent.