The realization of machines of molecular size is a fascinating task for the bottom-up approach to nanoscience and nanotechnology. The research in this area is nowadays possible owing to the advancement of several branches of chemistry, and is stimulated by the outstanding progress made in molecular biology, that has begun to reveal the structures and mechanisms of natural nanomachines which carry out key functions in living organisms.
This research line deals with the design, synthesis and investigation of multicomponent systems (in most cases rotaxanes, catenanes and related species) capable of performing mechanical motions of their molecular components in response to external stimuli (addition of chemical reactants, application of electrical potentials, light irradiation). Although mimicking the complexity of biological nanomachines is at present a prohibitive task for nanoscientists, our group has achieved several interesting results in the development of artificial molecular machines, including molecular elevators and an autonomous nanomachine powered by solar energy. Our current objective consists in the identification of strategies for obtaining mechanical nanodevices capable of performing specific tasks, such as the control of membrane permeability, the uptake and release of small molecules, and eventually the development of mechanical work on the micro- and macroscopic scales (molecular muscles).
In the past few years research in the molecular and supramolecular areas showed the possibility of developing new paradigms for information processing, similar to those employed by living organisms, in which information is transported, transformed and stored using ions and molecules. For instance, many cases of solution-based chemical systems capable of mimicking the binary logic functions performed by semiconductor solid-state circuits have been reported. Our group is among the pioneers in this field, with the realization of the first example of a molecular XOR gate. More recently, we studied a prototype of a molecular electrical extension cable and described the implementation of complex logic functions utilizing simple molecules.
The construction of a chemical computer that could replace current solid-state processors is the most fascinating objective in this area, albeit it is a futuristic task even for basic research. In the short-medium term one can envisage the construction of devices for specific applications in fields such as diagnostics, medicine and materials science where semiconductor electronic circuits cannot be used (for example, inside a cell or in a membrane). The possible products of this research include chemosensors capable of responding simultaneously to a predetermined pattern of different analytes, and systems for intelligent drug delivery, i.e. capable of releasing a drug only in the presence of a specific combination of chemical inputs.
Dendrimers are monodisperse macromolecules with well-defined tree-like architecture, in which we can define three different regions: core, branches and surface. They are an ideal scaffold to assemble a great number of functional units in a volume of nanometric dimension with a precise control on the nature, position, and distance of the various groups. Moreover, thanks to their three-dimensional structure, they possess dynamic cavities in which small ions or molecules can be hosted. The recognition process of the guest may also take advantage of cooperative effects due to multiple interacting units offered by the dendritic structure, compared to a simple host, constituted by a single recognition unit.
Thanks to their peculiar chemical-physical properties dendrimers are currently attracting increasing attention for a wide range of potential applications in such different fields as medicine, biology, chemistry, physics, and engineering.
Our research is focused on dendrimers containing photo- and redox-active units since luminescence and electrochemistry are valuable tools to get information on dendrimer structure and interaction with other species, and to perform useful functions, such as:
- molecular antennae to harvest light and transfer excitation energy to a common acceptor unit;
- luminescent sensors with signal amplification in which the interaction of a single analyte affects the luminescence of all the dendrimer chromophores;
- photoswitchable host in view of their application as photocontrollable membranes and drug delivery systems;
- molecular batteries5 to store charges towards the development of flexible batteries.
Nanoparticles have found many industrial employments in a wide range of fields such as electronics, optoelectronic, biomedical, pharmaceutical, cosmetic, catalytic, and materials areas. In particular, the research in the field of photoactive nanoparticles aims to the development of innovative nanosystems for biological imaging, medical diagnostic and therapeutics.
In this framework we have gained a significant know-how in different synthetic methodologies to prepare dye doped silica nanoparticles with defined and tunable dimensions. We developed new strategies to create multi-shell systems doped with different fluorophores, even inserting metallic or magnetic cores, biocompatible polymeric external layers, and to properly functionalize their surface with receptor groups for complexation or bioconjugation. The binding of biomolecules linked with a luminescent nanoparticle carrying a high number of dyes, induces a passive signal amplification (made possible by the presence in each detection complex of a high number of luminescent species) and the use of ultra sensitive luminescent detection techniques allows the development of highly sensitive analytical methods.
The mixed nanoparticles, i.e., with a magnetic core and one or more dye doped silica shells, are in study to obtain multimodal nanosystems that will allow the simultaneous detection of properly derivatized labels both via MR (magnetic resonance) and optical imaging.