Category: Biophysics and soft matter

In order to achieve a selective removal of specific pesticides from water, we synthesized, through the sol–gel technique, molecularly imprinted TiO₂ photocatalysts with the only use of the standard reactants of the TiO₂ solgel synthesis together with the pesticide molecules, without any addition of further reactants supports or matrices. It is a new, easy, smart and scalable method that avoid the multistep and solvent–consuming procedures, typical of the molecular imprinting. Two widely–used pesticides, i.e. the herbicide 2,4D, and the insecticide imidacloprid, were chosen as template for the molecular imprinting and as contaminants target for the photocatalytic tests. A remarkable enhancement of the photocatalytic activity was verified with the TiO₂ imprinted with the corresponding pesticide-target. The selectivity of the photodegradation process was verified thanks to the comparison with the degradation of pesticides not–used as template. Furthermore, the eventual toxic effects of the molecularly imprinted materials were evaluated by biological tests.

Contact person: Roberto Fiorenza, IMM c/o Università di Catania

High-throughput single-cell analysis is a challenging target for implementing advanced biomedical applications. An excellent candidate for this aim is label–free tomographic phase microscopy (TPM). We have reviewed some of the methods used to obtain TPM, analyzing advantages and disadvantages of each of them. Moreover, an alternative tomographic technique is described for live cells analysis, and future trends of the method are foreseen. In particular, by exploiting random rolling of cells while they are flowing along a microfluidic channel, it is possible to obtain phase-contrast tomography thus obtaining complete retrieval of both 3D–position and orientation of rotating cells. Thus, a priori knowledge of such information is no longer needed. This approach extremely simplifies the optical system avoiding any mechanical/optical scanning of light source. The proof is given for different classes of bio–samples, red–blood–cells (RBCs) and diatom algae. Accurate characterization of each type of cells is reported and compared to that obtained by other tomographic techniques.

Contact person: Francesco Merola,
ISASI Pozzuoli

Electromechanical coupling through piezoelectric polymer chains allows the emission of organic molecules in active nanowires to be tuned. This effect is evidenced by highly bendable arrays of counter–ion dye–doped nanowires made of a poly(vinylidenefluoride) copolymer. A reversible redshift of the dye emission is found upon the application of dynamic stress during highly accurate bending experiments. By density functional theory calculations it is found that these photophysical properties are associated with mechanical stresses applied to electrostatically interacting molecular systems, namely to counter–ion–mediated states that involve light–emitting molecules as well as charged regions of piezoelectric polymer chains. These systems are an electrostatic class of supramolecular functional stress–sensitive units, which might impart new functionalities in hybrid molecular nanosystems and anisotropic nanostructures for sensing devices and soft robotics.

Contact person: Luana Persano, NANO Pisa

Self–propelled particles, both biological and synthetic, are stably trapped by walls and develop high concentration peaks over bounding surfaces. In swimming bacteria, like E. coli, the physical mechanism behind wall entrapment is an intricate mixture of hydrodynamic and steric interactions with a strongly anisotropic character. We have demonstrated that, by using a combination of three-axis holographic microscopy and optical tweezers, it is possible to obtain volumetric reconstructions of individual E. coli cells that are sequentially released at a controlled distance and angle from a flat solid wall. We have found that hydrodynamic couplings can slow down the cell before collision, but reorientation only occurs while the cell is in constant contact with the wall. In the trapped state, all cells swim with the average body axis pointing into the surface. The amplitude of this pitch angle is anticorrelated to the amplitude of wobbling, thus indicating that entrapment is dominated by near–field couplings between the cell body and the wall.

Contact person: Silvio Bianchi, NANOTEC Rome

We have reported a voltage–free pyroelectrification (PE) process able to induce permanent and 2D patterned dipoles into polymer films, thus producing freestanding bipolar membranes. A single thermal stimulus triggers simultaneously the glass transition and the dipole orientation in the polymer. The technique is surprisingly easy to accomplish since the polymer solution is simply spin–coated onto a pyroelectric lithium niobate crystal that, during the thermal stimulus, generates spontaneously a surface charge density strong enough to orient the polymer dipoles.

Contact person: Simonetta Grilli, ISASI Pozzuoli

We have shown that a suspended red blood cell (RBC) behaves as an adaptive liquid–lens at microscale, thus demonstrating its imaging capability and tunable focal length. In fact, thanks to the intrinsic elastic properties, the RBC can swell up from disk volume of 90 fl up to a sphere reaching 150 fl, varying focal length from negative to positive values. These live optofluidic lenses can be fully controlled by triggering the liquid buffer’s chemistry. Real–time accurate measurement of tunable focus capability of RBCs is reported through dynamic wavefront characterization, showing agreement with numerical modelling. Moreover, in analogy to adaptive optics testing, blood diagnosis is demonstrated by screening abnormal cells through focal–spot analysis applied to an RBC ensemble as a microlens array.

Contact person: Lisa Miccio, ISASI–CNR Pozzuoli