Paclitaxel interferes with the normal function of microtubule breakdown, induces apoptosis in cancer cells and sequesters free tubulin. As this drug acts also on other cell mechanisms it is important to monitor its accumulation in the cell compartments. The intracellular spreading of the drug was followed using a WITEC 300R confocal Raman microscope equipped with a CCD camera. Hence Atomic force microscopy (an MFP3D- Asylum Research AFM) in imaging and force mode was used to determine the morphological and mechanical modifications induced on living cells. These studies were performed on living epithelial MCF-7 breast cancer cells. Paclitaxel was added to cell culture media for 3, 6 and 9 hours. Among the specific paclitaxel Raman bands we selected the one at 1670 cm-1 because it is not superposed by the spectrum of the cells. Confocal Raman images are formed by monitoring this band, the NH2 and the PO4 band. Paclitaxel slightly accumulates in the nucleus forming patches. The drug is also concentrated in the vicinity of the cell membrane and in an area close to the nucleus where proteins accumulate. Our AFM images reveal that the treated cancerous MCF-7 cells keep the same size as the non treated ones, but their shape becomes more oval. Cell's elasticity is also modified: a difference of 2 kPa in the Young Modulus characterizes the treated MCF-7 mammary cancerous cell. Our observations demonstrate that paclitaxel acts not only on microtubules but accumulates also in other cell compartments (nucleus) where microtubules are absent.

Addressing the surface chemistry of silicon is of fundamental scientific and technical significance due to the wide use of this material in electronics and optics. A novel method to functionalize silicon (Si) via short peptides with binding specificity for Si is presented. The peptide presenting the highest affinity for Si is identified via phage display technology, and the 12-mer LLADTTHHRPWT and SPGLSLVSHMQT peptides were found to be specific for the n+-Si and p+-Si surfaces, respectively. In our sensing application, the obtained peptides are used as functionalizing linkers to allow porous silicon microcavities to bind biotin and then capture streptavidin. Molecular detection is monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure. An improved streptavidin sensing (21 times lower detection limit) with peptide-functionalized porous silicon microcavities is demonstrated, compared to sensing performed with devices functionalized with the commonly used silanization method, suggesting that the modification of Si via Si-specific peptides provides better interface layers for molecular detection. High-resolution atomic force microscopy images corroborate this result and reveal the formation of ordered nanometer-sized molecular layers when peptide-route functionalization is performed.

The morphology changes, in particular the organization of microtubules in mammalian nonmalignant HMEC 184A1 and cancerous MCF-7 cells during curcumin treat- ment have been investigated by utilizing multiphoton, fluorescence, and atomic force (AFM) microscopies. Fluorescence microscopy reveals formation of ring-like structures of microtubules circumscribing the nuclear area in HMEC 184A1 cells after treatment, while in MCF-7 cells, no important changes were observed. Topo- graphy analyses of fixed HMEC 184A1 and MCF-7 be- fore and after treatment with curcumin were performed using AFM and the effect of the employed cells' fixation method was investigated on MCF-7 cells. Due to its in- depth optical sectioning capacity multiphoton microscopy provided valuable complementary information on curcu- min's effect on both cells' types. Combining information provided by AFM and optical fluorescence and biphoton microscopes allows us to gain a better understanding of the cells and their curcumin-induced changes, especially for microtubules which are the main target of antitumor chemotherapy treatments. Our multimicroscopic study demonstrates that 6 h incubation with curcumin does not induce significant modifications in the interphase micro- tubules in the malignant MCF7cell, whereas it has meas- urable effects on those of the nonmalignant HMEC 184A1 cells, revealing also morphology modifications over the nuclear area of these cells.