Table of contents

The concept of molecular nanomachines has become a reality in the past few years in organic and supramolecular chemistry, in biochemistry and in atom-scale manipulation with the scanning tunnelling microscope (STM).

In chemistry, molecules can be designed and synthesized to have specific electrical, mechanical, optical or reactive properties. In biochemistry, single natural biomolecules can be isolated and activated as nanomachines. In atom-scale manipulation, the STM can be used to power and to control the operation of individual molecules as molecular nanomachines.

The fields of chemical synthesis, biomolecular machines and atom-scale manipulations, have each developed as a separate entity. However, mutual integration of these different research fields appears to be a very fruitful approach for the future of molecular nanomachines. This special section of Journal of Physics: Condensed Matter is the follow-up to a meeting held in Les Houches (France) on 17–21 January 2005 on molecular nanomachines. The section aims to contribute to the readers' understanding by giving a clear overview of the principal issues of molecular nanomachines. We hope that it will facilitate new collaborations between researchers from these different fields, so necessary for the integrated development of molecular nanomachines.

The extension of the concept of machine to the molecular level is of great interest for the growth of nanoscience and the development of nanotechnology. A molecular machine can be defined as an assembly of a discrete number of molecular components (that is, a supramolecular structure) designed to perform a function through the mechanical movements of its components, which occur under appropriate external stimulation. Hence, molecular machines contain a motor part, that is a device capable of converting energy into mechanical work. Molecular motors and machines operate via nuclear rearrangements and, like their macroscopic counterparts, are characterized by the kind of energy input supplied to make them work, the manner in which their operation can be monitored, the possibility to repeat the operation at will, i.e., establishing a cyclic process, the timescale needed to complete a cycle of operation, and the performed function. Owing to the progresses made in several branches of chemistry, and to the better understanding of the operation mechanisms of molecular machines of the biological world, it has become possible to design and construct simple prototypes of artificial molecular motors and machines. Some examples based on rotaxanes, catenanes, and related interlocked molecules will be described.

A mono-molecular machine is a molecule designed to perform a function providing energy, data and/or orders to the molecule. A 'monumentalization' approach (the synthesis of very large molecules) is used to synthesize technomimetic molecules, i.e. molecules able to transpose macroscopic objects and their motions at the molecular level, and grants access to the study of the mechanical properties of a single molecule. This paper focuses on the mechanical molecular machines developed in our group which are controlled one at a time by the tip of a scanning tunnelling microscope, like the molecular wheelbarrow and the molecular gear, or in the future by an atomic force microscope, as in the case of the molecular motor.

We report here construction of pseudo-rotaxanes of α-cyclodextrin (α-CD) with axle molecules bearing pyridyl end caps via kinetic control of threading of α-CD onto axle molecules. A single substituted pyridyl group attached to the ends of the axle molecule regulates the rate for α-CD passing them. Two methyl substituents can clearly govern the degree of complex formation of α-CD with guest molecules and result in the distinction of face direction of CD molecules entering the axle ends. α-CDs are arranged in one direction at two station units of the axle molecule to give a face-selective pseudo-[3]rotaxane.

Since it was first evidenced in 1995, light-induced mass motion in layers of azobenzene-containing molecules has led to diverging interpretations, and it remains partly unexplained. In this paper, we discuss a light-driven random-walk model where moving chromophores drag the molecule to which they are grafted. It consists in a diffusion motion of the azobenzene functions where each random step follows an isomerizing absorption. After a summary of the main characteristics of the motion, we present the hypotheses of the model and we show how it suits the experimental observations reported. In the frame of this model, where each azobenzene function is put in motion by light, we assess the distance over which an azobenzene-containing molecule can be dragged. We also estimate the energetic output of this dragging process. Finally, we discuss the microscopic origin of these molecular motors and we compare it to the model of thermal ratchets introduced by Feynman and extensively resorted to in Biology nowadays.

Lateral manipulation of fullerenes on clean silicon surfaces may be induced by either an attractive or repulsive interaction between adsorbed molecules and the tip of a scanning probe microscope, and can result in a complex response arising from molecular rolling. The model for rolling is supported by new results which show that manipulation is suppressed for adsorbed functionalized fullerenes due to the presence of phenyl sidegroups. The influence of varying the dwell time of the tip during manipulation is also reported. By reducing this time to a value which is less than the response time of the feedback control loop it is possible to induce manipulation in a quasi-constant height mode which is accompanied by large increases/decreases in current.

External stimulus-induced changes in molecular read-out give rise to bistable nanoscopic switches. Beyond simple bistable species, multistate (multi-input/output) systems lead to the idea of molecular logic gates. Since the appearance of a prototypical molecular logic gate in 1993, different strategies have been described for developing these molecular information processors. Notably, various photophysical processes have been employed to effect the requisite changes in photonic output as a function of the input. Equally, different questions have been addressed with varying degrees of success concerning the connectivity/integration of logic gates and the superposition/multiplexing of optical logic gates. After introducing pertinent processes available in the chemist's toolbox for designing functional nanometric devices, illustrated with a few simple examples, more sophisticated combinatorial logic arrays are described, including molecular systems capable of numeracy.

We report the imaging of chlorobenzene molecules chemisorbed on the Si(111)-(7 × 7) surface at room temperature with the scanning tunnelling microscope, and the desorption of the molecules by the tunnelling current. Detailed voltage-dependent imaging (at positive bias) allows the elucidation of the number and orientation of all the adsorbate configurations in the 7 × 7 unit cell. At negative bias the adsorbate was observed to affect the imaging properties of neighbouring half unit cells. The threshold voltage required for desorption of the chlorobenzene molecules was invariant to small changes in the tip-state, the adsorption site (corner adatom, middle adatom, faulted or unfaulted half of the unit cell) and the kind of doping of the substrate (n or p type).

The electronic contact between a molecular wire and a metallic electrode will play an important role in future molecular electronics as its properties determine the conductivity of the molecule–metal system. Scanning tunnelling microscopy manipulation reveals various advantages for the investigation of electronic contacts at the atomic scale. In this review, several examples of molecular wire–electrode systems are presented, where single molecules are placed in contact in a controlled way. Changed chemical structures of the molecule and, on the other hand, different shapes and dimensions of electrodes lead to a variety of contact configurations. The contact can be characterized using the additional contribution to the tunnelling current, but also using the influence on the electronic states of the electrode and the molecule. The quality of the contact is discussed in terms of the vertical distance between the molecular wire and the metal atoms and of the chemical composition of the molecular end group.

It is suggested that some transition metal based catalysts can be converted to molecular motors providing that their substrate is grafted onto a surface as a self-assembled monolayer.

This approach may open new possibilities, such as the control of molecular motion and chemical reactivity at a sub-nanometre scale under the influence of macroscopic controls such as electric fields, liquid crystal phases or light beams. Such a control may ultimately lead to molecular lithography.

First experimental results towards that goal are described in the last part of the paper.

Powering and controlling the operation of a single molecule adsorbed on a surface can be achieved by using the tip of a scanning tunnelling microscope (STM) as an atomic-size source of electrons. We review the various electronic excitation processes induced by the electrons from the STM tip which are able to activate the functions of a molecular nanomachine. In particular, we review recent results illustrating the electronic control of molecular dynamics at the level of a single molecule.

To work, a unimolecular machine will ultimately depend on its preparation in a non-stationary superposition of its quantum states. We provide a description of the possible unimolecular devices or machineries for mechanics, information transmission, molecular electronics and molecular transduction. Experimenting on each category of machines must help to identify the physics behind the quantum superposition principle which is the driving force of most of those machines. This will help in optimizing their design and efficiency in such areas as the motive power for unimolecular mechanical machines, the capacity for molecular transmission channels, the computing power, speed and dissipated energy for molecular electronics and the sensitivity and response time for a unimolecular transducer.

Motor proteins of the myosin, kinesin and dynein families transport vesicles and other cargo along tracks of actin filaments or microtubules through the cytoplasm of cells. The mechanism by which myosin V, a motor involved in several types of intracellular transport, moves processively along actin filaments, has recently been the subject of many single molecule biophysical studies. Details of the molecular mechanisms by which this molecular motor operates are starting to emerge.

Kinesin is a dimeric molecular motor, which processively moves along the microtubule in a sequence of 8 nm steps. The stepping dynamics needs to be clarified: there are controversial reports about the existence of substructures in the mechanical step and the step timescale. We present observations of the kinesin steps in the absence of external forces, measured with subnanometre precision and microsecond time resolution using a technique which we have recently introduced and named travelling wave tracking. The data suggest that, at zero load, the 8 nm step occurs in less than 30 µs and without any long mechanical substeps.

The full text of the preface and a complete listing of the scientific programme of this workshop are given in the PDF.

In this paper various deterministic and statistical models, based on new quantized theories proposed by the author, are presented for estimating the strength of a real, and thus defective, space elevator cable. The cable, ∼100 000 km in length, is composed of carbon nanotubes, ∼100 nm long: thus, its design involves nanomechanics and megamechanics. The predicted strengths are extensively compared with the experimental and atomistic simulation results for carbon nanotubes available in the literature. All these approaches unequivocally suggest that the megacable strength will be reduced by a factor at least of ∼70% with respect to the theoretical nanotube strength, today (erroneously) assumed in the cable design. The reason is the unavoidable presence of defects in so huge a cable. Preliminary in-silicon tensile experiments confirm the same finding. The deduced strength reduction is sufficient to place in doubt the effective realization of the space elevator, that if built as designed today will certainly break (in the author's opinion). The mechanics of the cable is also revised and possible damage sources discussed.

The characterization of several differently sized aluminium powders, by BET (specific surface), EM (electron microscopy), XRD (x-ray diffraction), and XPS (x-ray photoelectron spectroscopy), was performed in order to evaluate their application in solid rocket propellant compositions. These aluminium powders were used in manufacturing several laboratory composite solid rocket propellants, based on ammonium perchlorate (AP) as oxidizer and hydroxil-terminated polybutadiene (HTPB) as binder. The reference formulation was an AP/HTPB/Al composition with 68/17/15% mass fractions respectively. The ballistic characterization of the propellants, in terms of steady burning rates, shows better performance for propellant compositions employing nano-aluminium when compared to micro-aluminium. Results obtained in the pressure range 1–70 bar show that by increasing the nano-Al mass fraction or decreasing the nano-Al size, larger steady burning rates are measured with essentially the same pressure sensitivity.

The influence of surface treatments on the mechanical strength of adhesive joints was investigated. The attention was focused on AA2024 alloy because it is extensively used in both the automotive and aerospace industries. Adhesive joints fabricated with pure aluminium were also investigated in order to evidence possible differences in the surface features after identical treatments. Before joining with a commercial epoxy adhesive, metal substrates were subjected to different kinds of treatment and the surfaces were characterized by SEM analysis. The formation of a microporous surface in the AA2024 alloy, upon etching and anodizing, is discussed on the basis of the role of the intermetallic particles and their electrochemical behaviour with respect to the aluminium matrix. Moreover, nanostructured porous oxide layers on both type of substrate were also formed, as a consequence of the anodizing process. Differences in their morphologies were revealed as a function of both the applied voltage and the presence of alloying elements. On this basis, an explanation of the different values of fracture energy measured by means of T-peel tests carried out on the corresponding joints was attempted.

Small analytes such as glucose, L-glutamine (Gln), and ammonium nitrate are detected by means of optical biosensors based on a very common nanostructured material, porous silicon (PSi). Specific recognition elements, such as protein receptors and enzymes, were immobilized on hydrogenated PSi wafers and used as probes in optical sensing systems. The binding events were optically transduced as wavelength shifts of the porous silicon reflectivity spectrum or were monitored via changes of the fluorescence emission. The biosensors described in this article suggest a general approach for the development of new sensing systems for a wide range of analytes of high social interest.

A quasielastic neutron scattering investigation, to study the single particle dynamics of water absorbed in a Nafion/zirconium phosphate composite membrane hydrated at a saturation value, is herewith presented. The measurements were done on samples hydrated with both H₂O and D₂O to properly select the spectral contribution of the confined water. Both the elastic incoherent structure factor (EISF) and the linewidth of the quasielastic component are evaluated as a function of the momentum transfer. Their trend suggests that the motion of the system hydrogen atoms can be schematized as a random jumping inside a confining spherical region, which can be related to the boundaries of the cluster that water molecules form around the sulfonic and phosphate acid sites. The size of such a region, the characteristic time necessary to explore the region and the number of mobile protons involved in this motion are similar to those estimated for water absorbed in a simple Nafion membrane at a saturation water content. Also the calculated jump diffusion coefficient resembles that of water confined in a simple Nafion membrane, and both are consistent with the value of bulk water. The results indicate that the dynamical behaviour of water in Nafion membranes is nearly unaffected by the presence of zirconium phosphate nanoparticles.

The advent and development of ultra-intense tabletop laser systems has played a significant role in recent decades thanks to the wide number of applications and studies in which these systems were demonstrated to be appropriate. Among these, one of the main applications of ultra-intense radiation is generation of plasma by solid, liquid or gaseous targets. The by-product of x-radiation found many different applications such as spectroscopy, imaging, microlithography, microscopy, radiographies (in particular of biological samples), radiation–matter interaction, fundamental plasma parameter determination, astrophysics, inertial confinement fusion, high energy physics, quantum electrodynamics, and many others.

In the following a brief description of our tabletop Nd:YAG/glass apparatus (facility of the Quantum Electronic and Plasma Laboratory of the University of Rome 'Tor Vergata'), together with x-ray conversion efficiency studies for different targets, are reported.

Four models of single-walled AlN nanotubes (NTs), which possess (i) two different chiralities (armchair or zigzag type) and (ii) two different uniform diameters for both types of NTs (1 or 6 nm) have been constructed, in order to analyse the dependence of their properties on both morphology and thickness. Periodic one-dimensional (1D) DFT calculations performed on these models have allowed us to analyse how the chirality and curvature of the NT change its properties as compared to both AlN bulk with either wurtzite or zinc-blende structures and their densely packed surfaces. We have found that the larger the diameter of the AlN NT, the smaller the width of its bandgap, the strengths of its bonds and the charge separations in them. This confirms the recent experimental finding of the possibility to adjust electronic properties in ultimate nanoscale optoelectronic devices produced from AlN and other group III nitrides.

The energy level alignment at the interface between fullerene (C₆₀) and Co has been determined by x-ray and ultraviolet photoelectron spectroscopy. To investigate the interfacial electronic structure, a C₆₀ layer was deposited on a clean Co surface in a stepwise manner. The measured onset of the highest occupied molecular orbital energy level was at 1.54 eV from the Fermi level of Co. The vacuum level was shifted 0.41 eV toward lower binding energy with the additional C₆₀ layers, which means that an interface dipole exists at the interface between C₆₀ and Co. The C 1s spectra show that band bending occurs at the interface between C₆₀ and Co. These results indicate that the barrier height of the hole injection from Co to C₆₀ is 1.14 eV, which is a smaller value than that for electron injection (1.46 eV).

Nanopowdered solid solution Ce_1−xY (Nd)_xO_2−δ samples (0.1≤x≤0.25) were made by self-propagating room temperature (SPRT) synthesis. The first-order Raman spectra of Ce_1−xY (Nd)_xO_2−δ samples measured at room temperature exhibit three broad features: the main Raman active F_2g mode at about 450 cm⁻¹ and two broad features at about 550 (545) and 600 cm⁻¹. The mode at ∼600 cm⁻¹ was assigned to the intrinsic oxygen vacancies due to the nonstoichiometry of ceria nanopowders. The mode at about 550 (545) cm⁻¹ was attributed to the oxygen vacancies introduced into the ceria lattice whenever Ce⁴⁺ ions are replaced with trivalent cations (Y³⁺, Nd³⁺). The intensity of this mode increases with doping in both series of samples, indicating a change of O²⁻ vacancy concentration. The mode frequency shifts in opposite direction in Y- and Nd-doped samples with doping level, suggesting that different types of defect space can occur in Y- and Nd-doped ceria nanopowders.

We discuss correlated lattice models with a time-dependent potential across a barrier and show how to implement a Josephson junction-like behaviour. The pairing occurs by a correlation effect enhanced by the symmetry of the system. In order to produce the effect we need a mild distortion which causes avoided crossings in the many-body spectrum. The Josephson-like response involves a quasi-adiabatic evolution in the time-dependent field. We also observe an inverse Josephson (Shapiro) current by applying an AC bias; a supercurrent in the absence of electromotive force can also be excited. The qualitative arguments are supported by explicit exact solutions in prototype five-atom clusters with on-site repulsion. These basic units are then combined in ring-shaped systems, where one of the units sits at a higher potential and works as a barrier. In this case the solution is found by mapping the low-energy Hamiltonian into an effective anisotropic Heisenberg chain. Once again, we present evidence for a superconducting flux quantization, i.e. a Josephson junction-like behaviour suggesting that an effective order parameter is already being built up in few-electron systems. Some general implications for the quantum theory of transport are also briefly discussed, stressing the nontrivial occurrence of asymptotic current oscillations for long times in the presence of bound states.

The radiation of relativistic charged particles for quasiperiodic motion in a transparent medium is considered. For motion of the general kind the differential probability of the process is obtained. For planar motion the spectral intensity of the radiation is found. Different cases of radiation in medium-filled undulators are studied. In particular, the influence of Cherenkov radiation on the undulator radiation is discussed.

We investigated different AlN nano-systems using spectroscopic methods. Experiments were performed at the Synchrotron Radiation Facility of the Laboratori Nazionali di Frascati using both XANES (x-ray absorption near edge spectroscopy) and FTIR (Fourier transform infrared spectroscopy) techniques in order to investigate materials with both interesting tribological and electronic properties. Comparisons have been performed between measurements by standard x-ray diffraction (XRD) and x-ray absorption (XRS) at the K-edge of Al, a spectroscopy method sensitive to the local order and correlated to the local and empty density of states of this wide band-gap semiconductor. Preliminary XAS simulations at the Al K edge are also presented. Correlations between XRD and XAS have been drawn, since x-ray absorption reveals structural information complementary to that addressed by x-ray diffraction. Moreover, a comparison has been performed by infrared (IR) absorption both in the mid- and in the far-IR ranges between different AlN forms: namely, powders, nanoparticles and nanotubes. Data clearly show changes connected with the electronic properties and the optical phonon modes of AlN nano-systems.

The transport properties of 4 Å diameter carbon nanotubes have been studied in recent experiments by Tang et al, and evidence of superconductivity at about 15 K has been claimed. The only metallic nanotubes compatible with such a small radius are the (3, 3) armchair and the (5, 0) zigzag respectively. In this paper we study the electronic properties of both these systems, paying special attention to the screening effects coming from the surrounding environment characterizing the experimental set-up. We look for the low temperature instabilities in the Luttinger liquid description of the correlated electron system. The phase diagram is investigated by taking into account the competition between the Coulomb repulsion and the phonon-mediated electron–electron interaction.

Recently, ultra-small diameter single wall nanotubes with diameter of ∼0.4 nm have been produced and many unusual properties were observed, such as superconductivity, leading to a transition temperature T_c∼15 K, much larger than that observed in the bundles of larger diameter tubes.

By a comparison between two different approaches, we discuss the issue of whether a superconducting behaviour in these carbon nanotubes can arise by a purely electronic mechanism in the armchair geometry. The first approach is based on the Luttinger model while the second one, which emphasizes the role of the lattice and short range interaction, is developed starting from the Hubbard Hamiltonian. By using the latter model we predict a transition temperature of the same order of magnitude as the measured one.

The realization of organic light-emitting transistors (OLETs) with high quantum efficiency and fast switching time is crucial for the development of highly integrated organic optoelectronic systems. In order to reach such a goal, fabrication of devices with ambipolar transport and high charge mobility values is needed. At present, organic materials having intrinsically ambipolar transport are restricted in number and show poor performance. This limits their use in efficient and fast switching single layer ambipolar OLETs. In this framework, we have taken the approach of combining p-type and n-type materials in two complementary configurations. The first one is based on realizing layered structures (bi-layer heterojunction) where materials are sequentially deposited. The second one is based on simultaneously evaporating two materials with variable composition (bulk heterojunction) to form a mixed film. In this paper, the charge transport and electroluminescence properties of OLETs based on these heterostructures are presented. A correlation between the active layer structure and the electrical performances has been obtained by means of laser scanning confocal microscopy, here employed for morphology and spectroscopy analysis. Differences between the two approaches are critically discussed.

The electro-optical behaviour of organic light emitting diode devices (OLEDs) is greatly influenced by the morphology of the films. A major parameter is due to the important role that the morphology of the active organic thin films plays in the phenomena that lead to light emission. For vacuum-grown OLEDs, the morphology of the specific thin films can be varied by modification of the deposition conditions. We have assessed the method (ultrahigh-vacuum organic molecular beam deposition) and conditions (variation of the deposition rate) for electro-emission (EL) optimization in a standard α-NPB (N,N'-bis-(1-naphthyl)-N,N' diphenyl-1,1' biphenyl-4-4' diamine)/Alq3 (tris-(8-hydroxyquinoline) aluminium) vacuum-grown OLED device. The best EL performances have been obtained for OLEDs made in ultrahigh vacuum with the Alq3 layer deposited with a differential deposition rate ranging from . The results are consistent with a model of different Alq3 morphologies, allowing efficient charge injection at the metal/organic interface, and of the minimization of grain boundaries at the electron–hole recombination interface, allowing efficient radiative excitonic decay. At the same time, with the objective of controlling and stabilizing the morphology changes and stabilizing the charge transport over a long OLED operating time, we have studied the effect of thermal annealing processing in the standard current behaviour of OLEDs. The large current fluctuations typically observed for standard vacuum-grown OLEDs have been smeared out and kept constant over a long operating time by the given thermal annealing conditions. The results are interpreted in terms of the stabilization of intrinsic polymorphism of the organic film's structure induced by thermal energy and leading the morphology to a lowest-energetic configuration.

The photocatalytic properties of the anatase form of nanocrystalline TiO₂ doped with lanthanide ions (Eu³⁺,Sm³⁺ and Er³⁺), obtained by a sol–gel preparation method, are studied by means of the degradation of methylene blue. It is observed that the presence of Sm³⁺ ion as a dopant significantly improves the photocatalytic activity of anatase TiO₂ with respect to the Eu³⁺ or Er³⁺ ions.

For the understanding of such a catalytic process the charge transport in these systems is studied by an appropriate Monte Carlo simulation which includes phonons, charged impurities and traps. The obtained results evidence the important role of the traps for the transit of the electrons in the systems investigated here. They decrease the diffusion coefficient by about three orders of magnitude with respect to the bulk, from which it is possible to obtain a simple estimate of the reaction rate in agreement with experimental results. All the lanthanide-doped samples show a strong luminescence in the visible region. The emission bands are affected by a notable inhomogeneous broadening, indicating a high disorder of the crystalline environment of the lanthanide ions in the titania host.

The electron states in a cylindrical quantum well with a convex bottom in a magnetic field directed along the wire axis are investigated. The electron wavefunctions, depending on the quantum well characteristics and the magnetic field induction, are found. The absorption coefficient of a monochromatic linearly polarized light wave caused by intersubband transitions of electrons in the quantum wire is calculated. The selection rules are considered and analytical expressions for the absorption coefficient are presented for two cases of light wave polarization.

Two-electron systems consisting of two laterally or vertically coupled quantum dots (QDs) are considered. Their behaviour in external magnetic field is studied. Ground state energies and energy spectra were obtained taking into account interelectron interaction for a wide range of values of confining potential steepness (α), distance between QDs (d), and external magnetic field (B). The spontaneous magnetization and the singlet–triplet transformation of the QD molecule ground state controlled by the magnetic field are studied.

The effects of non-ideal experimental configuration on the mechanical resonance of boron (B) nanowires (NWs) were studied to obtain the corrected value for the Young's modulus. The following effects have been theoretically considered: (i) the presence of intrinsic curvature, (ii) non-ideal clamps, (iii) spurious masses, (iv) coating layer, and (v) large displacements. An energy-based analytical analysis was developed to treat such effects and their interactions. Here, we focus on treating the effect of the intrinsic curvature on the mechanical resonance. The analytical approach has been confirmed by numerical FEM analysis. A parallax method was used to obtain the three-dimensional geometry of the NW.

Recent advances in nanotechnology have increased the development and production of many new nanomaterials with unique characteristics for industrial and biomedical uses. The size of these new nanoparticles (<100 nm) with their high surface area and unusual surface chemistry and reactivity poses unique problems for biological cells and the environment. This paper reviews the current research on the reactivity and interactions of carbon nanoparticles with biological cells in vivo and in vitro, with ultrastructural images demonstrating evidence of human cell cytotoxicity to carbon nanoparticles characteristic of lipid membrane peroxidation, gene down regulation of adhesive proteins, and increased cell death (necrosis, apoptosis), as well as images of nontoxic carbon nanoparticle interactions with human cells. Although it is imperative that nanomaterials be systematically tested for their biocompatibility and safety for industrial and biomedical use, there are now ways to develop and redesign these materials to be less cytotoxic, and even benign to cell systems. With this new opportunity to utilize the unique properties of nanoparticles for research, industry and medicine, there is a responsibility to test and optimize these new nanomaterials early during the development process, to eliminate or ameliorate identified toxic characteristics.

Several monoolein/water (MO/W) based liquid crystalline (LC) nanostructured mesophases have been revisited in view of the new trends of modern drug delivery formulations. The shape and amphiphilic character of the investigated lipid molecules address the preferential polar–apolar interfacial curvature and the delicate interplay of different intermolecular forces that drive self-assembly and thermodynamic stability of the nanostructures.

Here some preliminary results related to the release of the antiviral drug 1-amine-adamantane hydrochloride, solubilized in the aqueous domain of bicontinuous cubic and reverse hexagonal LC phases, suggest these MO based LC phases as possible nano-depot systems for long term controlled release. Drug release was followed by conductivity measurements during a period of ten days.

An effective and targeted drug delivery often requires a specific molecular recognition. With this aim, the possibility to entrap suitable molecules such as lauroylcholine (LCh, a cationic surfactant having a peptide-like polar head that can 'recognize' membrane proteins) and adenosine monophosphate disodium salt (NaAMP, an electrolyte that can 'recognize' purine receptors) has been tested. The addition of LCh to MO/W cubic gyroid (C_G) LC phase causes a cubic–lamellar phase transition. The addition of NaAMP still allows the formation of the C_G nanostructure. In the presence of both NaAMP and LCh again a C_G LC phase forms. The bicontinuous C_G LC phases have been characterized by NMR and SAXS.

In recent years, biological micro-electro-mechanical systems (commonly referred to as BioMEMS) have found widespread use, becoming increasingly prevalent in diagnostics and therapeutics. Cell-based sensors are nowadays gaining increasing attention, due to cellular built-in natural selectivity and physiologically relevant response to biologically active chemicals. On the other hand, surrogate microbial systems, including yeast models, have become a useful alternative to animal and mammalian cell systems for high-throughput screening for the identification of new pharmacological agents. A main obstacle in biosensor device fabrication is the need for localized geometric confinement of cells, without losing cell viability and sensing capability. Here we illustrate a new approach for cellular patterning using dewetting processes to control cell adhesion and spatial confinement on modified surfaces. By the control of simple system parameters, a rich variety of morphologies, ranging through hexagonal arrays, polygonal networks, bicontinuous structures, and elongated fingers, can be obtained.

In view of the importance of vesicles as models for early cells, several groups have started work looking for conditions under which vesicles can undergo growth and division. Evidence for growth and division has been obtained with the help of ferritin-labelled vesicles; furthermore, it has been shown that in such processes the vesicle size distribution is largely conserved. In both cases, the data suggest that the process under study is mainly characterized by vesicle growth and eventually division into daughter vesicles. However, direct evidence for vesicle division has not been obtained. In this paper, mostly based on freeze-fracture electron microscopy, we describe conditions under which for the first time division intermediates can be trapped in the form of twin vesicles. This finding, together with supporting dynamic light scattering and fluorescence investigations, permits us to establish some additional points in the mechanism of vesicle self-reproduction.