Multimicroscopic study of curcumin effect on fixed nonmalignant and cancerous mammalian epithelial cells.

The morphology changes, in particular the organization of microtubules in mammalian nonmalignant HMEC 184A1 and cancerous MCF-7 cells during curcumin treatment 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. Topography analyses of fixed HMEC 184A1 and MCF-7 before 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 indepth optical sectioning capacity multiphoton microscopy provided valuable complementary information on curcumin'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 microtubules in the malignant MCF7cell, whereas it has measurable effects on those of the nonmalignant HMEC 184A1 cells, revealing also morphology modifications over the nuclear area of these cells.

Sensing by means of nonlinear optics with functionalized GaAs/AlGaAs photonic crystals.

We report on specific functionalization of GaAs/AlGaAs photonic structures for molecular sensing via the optical second harmonic generation signal in the visible range exhibited by these nanostructures. Functionalization has been achieved by peptides selected by the phage display technology, revealing specific recognition for semiconducting surfaces. These small peptides when biotinylated serve for controlled placement of biotin onto the substrate to capture then streptavidin. Functionalization (with biotinylated peptide) and molecular recognition (of streptavidin) events both result in enhancing the nonlinear optical response of the samples. Adsorption and infiltration of biomolecules into the GaAs/AlGaAs photonic structure were monitored by atomic force and scanning electron microscopy combined with Energy Dispersive X-ray spectroscopy. We demonstrate that once functionalized with specific peptides, photonic structures could be used as miniature biosensors down to femtomolar detection sensitivity, by monitoring changes in the second harmonic signal when molecules are captured. Our results prove the outstanding sensitivity of the nonlinear approach in biosensing with photonic crystal waveguides as compared to linear absorption techniques on the same samples. The present work is expected to pioneer development of a new class of extremely small affinity-based biosensors with high sensitivity and demonstrates that photonic structures support device functionality that includes strongly confined and localized nonlinear radiation emission and detection processes.

Biosensing and protein fluorescence enhancement by functionalized porous silicon devices.

Porous silicon (PSi) is a promising biomaterial presenting the advantage of being biocompatible and bioresorbable. Due to the large specific surface area and unique optical features, these microporous structures are excellent candidates for biosensing applications. Investigating device functionality and developing simple Si-based transducers need to be addressed in novel biological detection. Our work demonstrates that, among the various PSi configurations for molecular detection, PSi microcavity structure demonstrates the best biosensing performance, reflected through the enhanced luminescence response and the changes in the refractive index. For successful immobilization, molecular infiltration and confinement are the two key factors that are controlled by the pore size distribution of the PSi microcavities and by the surface modification obtained by silane-glutaraldehyde chemistry. Enhancement of the fluorescence emission of confined fluorescent biomolecules in the active layer of PSi microcavities was observed for a nonlabeled protein with a natural green fluorescence, the glucose oxidase enzyme (GOX). An increase in the fluorescence emission was also observed when functionalized PSi material was used to detect specific binding between biotin and a low concentration of labeled streptavidin. Evidence for the enzymatic activity of GOX in its adsorbed form is also presented. Use of smart silicon devices, enabling enhancement of fluorescence emission of biomolecules, offers easy-to-use biosensing, based on the luminescence response of the molecules to be detected.