Multiple equilibria in natural and biological fluids: from speciation to selective sequestering

Natural and biological fluids are complex matrices containing a large number of species (metal, organic and inorganic cations/anions), with variable features/concentrations. Molecular recognition and selective complexation of ionic species in water are key processes which control many biological phenomena (enzyme catalysis, transport through membranes, antibiotic activity) and are also crucial for understanding critical environmental issues (species toxicity and bioavailability). The study of multi-component solutions implies the determination of the "distribution of an element amongst defined chemical species in a system" through a "speciation analysis" (IUPAC 2000). In order to move from speciation to selective sequestering we have selected some systems that may be representative of situations/conditions occurring in nature. The proposal benefits from the Research Units expertise in analytical, modeling, coordination chemistry and thermodynamics of host-guest and ion-ligand systems for the detection/removal of chemical species in fluids of biological/environmental relevance.
Main objectives of the project are:

• Molecular receptors for the recognition of anionic and cationic guests in water. Determination of binding parameters, species distribution, “best” pH window for recognition as well as splitting of ΔG into ΔH and ΔS. Selection of candidates suitable for supramolecular capsules (confinement/transport of guests).
• Synthesis and characterization of new fluorescent sensors for the detection of Cd2+, Hg2+, Pb2+ and Platinum Group Metals (PGM) at very low concentrations.
• Synthesis and characterization of chelators to treat metal (Fe3+ and Al3+) overload in living organisms by in silico design of new ligands followed by the study of the most promising chelators. Metal uptake/release and toxicity of the species resulting from cell culture in vitro.
• Speciation and determination of the binding parameters of complexes of VO2+ and UO22+ with biomolecules, to explore the potential therapeutical applications of VO2+ complexes as insulin mimics and the chemotoxicity of UO22+ species.
• Formation of activated carbons (AC) and carbon nanotubes (CN) functionalized with polydentate ligands able to bind environmentally or biologically relevant cations and anions.
• Study of the ability of natural ligands to sequester metal and organometallic cations and determination of thermodynamic parameters.
• Investigation of the sorption process of toxic metal ions (Cd2+, Pb2+, Hg2+, Pd2+) and organometallic cations by using largely available sorbent materials with low environmental impact and high sequestering ability.
• Modeling of the multiple interactions taking place in most of the above multi-component systems, with analysis of the principal physico-chemical and chemical effects towards the stability of species with the aim of designing more efficient receptors and chelators.