Giuseppe Maruccio

Charge transport and intrinsic fluorescence in amyloid-like fibrils.

The self-assembly of polypeptides into stable, conductive, and intrinsically fluorescent biomolecular nanowires is reported. We have studied the morphology and electrical conduction of fibrils made of an elastin-related polypeptide, poly(ValGlyGlyLeuGly). These amyloid-like nanofibrils, with a diameter ranging from 20 to 250 nm, result from self-assembly in aqueous solution at neutral pH. Their morphological properties and conductivity have been investigated by atomic force microscopy, scanning tunneling microscopy, and two-terminal transport experiments at the micro- and nanoscales. We demonstrate that the nanofibrils can sustain significant electrical conduction in the solid state at ambient conditions and have remarkable stability. We also show intrinsic blue-green fluorescence of the nanofibrils by confocal microscopy analyses. These results indicate that direct (label-free) excitation can be used to investigate the aggregation state or the polymorphism of amyloid-like fibrils (and possibly of other proteinaceous material) and open up interesting perspectives for the use of peptide-based nanowire structures, with tunable physical and chemical properties, for a wide range of nanobiotechnological and bioelectronic applications.

Electrostatic spin crossover effect in polar magnetic molecules

The magnetic configuration of a nanostructure can be altered by an external magnetic field, by spin-transfer torque or by its magnetoelastic response. Here, we explore an alternative route, namely the possibility of switching the sign of the exchange coupling between two magnetic centres by means of an electric potential. This general effect, which we name electrostatic spin crossover, occurs in insulating molecules with super-exchange magnetic interaction and inversion symmetry breaking. As an example we present the case of a family of di-cobaltocene-based molecules. The critical fields for switching, calculated from first principles, are of the order of 1 V nm(-1) and can be achieved in two-terminal devices. More crucially, such critical fields can be engineered with an appropriate choice of substituents to add to the basic di-cobaltocene unit. This suggests that an easy chemical strategy for achieving the synthesis of suitable molecules is possible.

Projecting the nanoworld: Concepts, results and perspectives of molecular electronics

A bottom-up approach is a promising alternative to build nanodevices and/or nanomachines starting from molecular building blocks. The idea of molecular electronics comes from a farsighted paper by Aviram and Ratner, predicting that single molecules with a donor–spacer–acceptor structure would have rectifying properties when placed between two electrodes. Today, molecular electronics is emerging as an alternative to Si-nanoelectronics for building integrated devices. This review aims to give an overview of this emerging field, analysing the concepts, the key results and the perspectives.

Amyloid-like Fibrils in Elastin-Related Polypeptides : Structural Characterization and Elastic Properties

We report on the structural characterization of amyloid-like fibrils, self-assembled from synthetic polypentapeptides poly(ValGlyGlyLeuGly), whose monomeric sequence is a recurring, simple building block of elastin. This polymer adopts a beta-sheet structure as revealed by circular dichroism and Fourier transform infrared spectroscopy. Furthermore, Thioflavin-T and Congo red birefringence assays confirm the presence of amyloid-like structures. To analyze the supramolecular assembly and elastic properties of the fibrils, we employed atomic force microsocopy and spectroscopy, measuring also the elasticity of mature elastin for a comparative analysis. In the case of fibrils we estimated a Youngs modulus ranging from 3.5 to 7 MPa, whereas for elastin it is around 1 MPa. The possibility to section individual fibrils with nanometric control by the AFM tip, realizing biomolecular gaps in the 100 nm range, is also demonstrated. These results are expected to open interesting perspectives for the fabrication of protein-inspired nanostructures with specific physical and chemical properties for applications in biotechnology and tissue engineering.

Cytomechanical and topological investigation of MCF-7 cells by scanning force microscopy.

Despite enormous advances in breast cancer biology, there is an increased demand for new technologies/methods that are able to provide supplementary information to genomics and proteomics. Here, we exploit scanning force microscopy (SFM) in combination with confocal microscopy, to investigate the morphological and mechanical properties of two neoplastic cell lines: (i) MCF-7 (human breast cancer) and (ii) HeLa (human cervical carcinoma). Living and fixed cells either in phosphate buffer solution (PBS) or in air have been studied, and the viscoelastic properties (including the Youngs modulus) of cells grown onto standard and modified (e.g. by fibronectin, one of the cellular matrix components) substrates have been measured. We observed different Youngs modulus values, influenced by the adhesion and growth behaviour onto specific substrate surfaces.

Electronic rectification in protein devices

We show that the electron-transfer protein azurin can be used to fabricate biomolecular rectifiers exploiting its native redox properties, chemisorption capability and electrostatic features. The devices consist of a protein layer interconnecting nanoscale electrodes fabricated by electron beam lithography. They exhibit a rectification ratio as large as 500 at 10 V, and operate at room temperature and in air.

Wavelength control from 1.25 to 1.4 μm in InxGa1−xAs quantum dot structures grown by metal organic chemical vapor deposition

This letter reports on the realization of long-wavelength InGaAs quantum dots (QDs) fabricated by metal organic chemical vapor deposition. By controlling the In incorporation in the QD layers and/or in the barrier embedding the QDs, we are able to tune the wavelength emission continuously from 1.25 to 1.4 μm at room temperature. Efficient stacking of dots emitting at 1.3 μm is also demonstrated.

Solid‐State Molecular Rectifier Based on Self‐Organized Metalloproteins

Recently, great attention has been paid to the possibility of implementing hybrid electronic devices exploiting the self-assembling properties of single molecules. Impressive progress has been done in this field by using organic molecules and macromolecules. However, the use of biomolecules is of great interest because of their larger size (few nanometers) and of their intrinsic functional properties. Here, we show that electron-transfer proteins, such as the blue copper protein azurin (Az), can be used to fabricate biomolecular electronic devices exploiting their intrinsic redox properties, self assembly capability and surface charge distribution. The device implementation follows a bottom-up approach in which the self assembled protein layer interconnects nanoscale electrodes fabricated by electron beam lithography, and leads to efficient rectifying behavior at room temperature.

Hybrid molecular electronic devices based on modified deoxyguanosines

A new type of organic semiconductor, based on self-assembled modified DNA nucleosides (deoxyguanosine lipophilic derivative), is employed to fabricate hybrid molecular devices. Two different modifications of the guanosine are synthesized in order to change the oxidation potential of the active molecular system. The influence of the solvent on the self-assembly process and on the carrier transport is investigated by atomic force microscopy and electrical measurements, respectively. Our results demonstrate that upon appropriate engineering of the molecule and choice of the solvent, self-organization of molecules in ordered structures is achieved, resulting in high conductivity and electronic rectification in solid-state, planar molecular devices. The transport properties depend strongly on the molecular structure and on the arrangement of the molecules into the hybrid devices, thus opening the route to molecular transport engineering in hybrid molecular electronics.

Automatic transwell assay by an EIS cell chip to monitor cell migration

Here an EIS (electrochemical impedance spectroscopy) biochip to detect cell migration is demonstrated. This biochip has been inspired by a traditional transwell assay/modified Boyden chamber and consists of two compartments separated by a porous membrane. This structure (PDMS-based) is aligned to EIS sensors. Cells are seeded in the upper chamber through microfluidic channels. During migration cells go through the pores of the membrane and get in touch with the electrodes that detect migrated cells. The performance of our cell-chip was tested by investigating the migratory ability of hepatocellular carcinoma (HCC) cells as a function of microenvironment. For this purpose we challenged HCC cells to migrate on different extra-cellular matrix (ECM) components including laminin 1, collagen IV and laminin 5. The results reveal that our cell chip provides reliable results that consistently overlap with those obtained with traditional standardized Boyden chambers. Thus, we demonstrate a new, easy tool to study cell migration and to perform automatic assays. This approach is easier and faster than traditional transwell assays and can be suitable for high-throughput studies in drug discovery applications.