A. Palumbo Piccionello

Perfluorocarbon functionalized hyaluronic acid derivatives as oxygenating systems for cell culture

A set of new hyaluronic acid (HA) derivatives was obtained by binding fluorinated oxadiazole (OXA) moieties to an amino derivative of the polysaccharide (HA-EDA). The obtained HA-EDA-OXA biomaterials are potentially able to improve oxygenation into a scaffold for tissue engineering purposes. The oxygen solubility in aqueous dispersions of the obtained derivatives showed that polymers were able to improve oxygen uptake and maintenance in the medium. The HA-EDA-OXA was employed to form a hydrogel in situ by reaction with a vinyl sulphone derivative of inulin, under physiological conditions. The influence of the presence of OXA moieties on the mechanical properties of the obtained hydrogels as well as on the metabolic activity of incorporated primary fibroblasts was investigated. The produced HA-EDA-OXA biomaterials were able to promote cell growth under hypoxic conditions.

Synthesis of a fluorinated graphene oxide–silica nanohybrid: improving oxygen affinity

An easy method to achieve a fluorinated graphene oxide–silica nanohybrid (GOSF) is presented. Graphene oxide (GO) was synthesized by Hummers modified method, the GO–silica nanohybrid (GOS) was obtained via Fischer esterification, the fluorinated moiety (3-pentadecafluoroheptyl-5-perfluorophenyl-1,2,4-oxadiazole) was introduced by nucleophilic substitution operated by the hydroxyl functionalities onto the GOS surface. Full characterization of the new materials confirmed the formation of covalent bonds between the graphene oxide/silica hybrid matrix and the fluorinated moieties. The proposed methodology offers an easy way to get fluorinated carbon/silica hybrid nanomaterials avoiding the harsh reaction conditions usually involved in the preparation of fluorinated materials, and allowing the selective immobilization of specific fluorotails. Moreover, performed oxygen uptake and release kinetics showed that the introduction of fluorinated moieties increases the oxygen exchange, making the material interesting for prospective applications in the biomedical field, as oxygen delivery system, as filler for biocompatible materials, and in the preparation of membranes for the purification of water.

Extended investigation of the aqueous self-assembling behavior of a newly designed fluorinated surfactant.

The physicochemical behavior of the newly synthesized fluorinated 5-hydroxyamino-3-perfluoroheptyl-1,2,4-oxadiazin-6-one (PFHO) surfactant was investigated. Thermal analysis showed that the pure surfactant is thermally stable under an inert atmosphere to 135 degrees C, which is several degrees higher than the melting point (99 degrees C). PFHO is rather active at the water/air interface where it assumes a standing up configuration. It exhibits an enhanced self-assembling behavior; accordingly, the critical micellar concentrations at some temperatures are 2 orders of magnitude lower than those of a similar surfactant having the same phobicity, such as sodium perfluorooctanoate. Even in the dilute domains, PFHO forms large micelles, detected by dynamic light scattering studies, that are precursors of the gel occurring at rather low composition (only 2.0% w/w at 25 degrees C). Optical microscopy evidenced cylindrical aggregates in gel systems whereas differential scanning calorimetry and viscosity showed that the gels are stable over a wide temperature range to ca. 70 degrees C where they undergo a reversible gel --> fluid transition. Finally, percolation theory combined with data provided by the experimental studies enabled us to predict the PFHO gelation process correctly, in very good agreement with the experimental findings.

Quaternary structures of GroEL and naïve-Hsp60 chaperonins in solution: A combined SAXS-MD study

The quaternary structures of bacterial GroEL and human naive-Hsp60 chaperonins in physiological conditions have been investigated by an innovative approach based on a combination of synchrotron Small Angle X-ray Scattering (SAXS) in-solution experiments and molecular dynamics (MD) simulations. Low-resolution SAXS experiments over large and highly symmetric oligomers are analyzed on the basis of the high-resolution structure of the asymmetric protein monomers, provided by MD. The results reveal remarkable differences between the solution and the crystallographic structure of GroEL and between the solution structures of GroEL and of its human homologue Hsp60.

Concise asymmetric synthesis of Linezolid through catalyzed Henry reaction

A new asymmetric synthesis of the antibiotic Linezolid was performed through a copper-catalyzed Henry reaction as the key step. The use of camphor-derived aminopyridine ligands helped to improve the yields of the chiral precursor and to obtain Linezolid in good overall yield and enantiomeric excess.

Photochemical synthesis of pyrene perfluoroalkyl derivatives and their embedding in a polymethylmethacrylate matrix: a spectroscopic and structural study

A photochemical, alternative and eco-compatible approach to perfluoroalkyl derivatives of pyrene is presented. The perfluoroalkyl chain is regiospecifically introduced at the 1 position of pyrene. The synthesized products have been embedded in a polymethylmethacrylate matrix by photocuring at 365 nm. Both the photochemical reactions can be considered a “green tool” for the synthetic chemist in order to obtain materials with prospective optoelectronic applications. The so-obtained composites have been the object of a study by UV and fluorescence spectroscopy in order to explore their luminescence properties. The small angle X-ray scattering and the transmission electron microscopy techniques were used to investigate the microstructure. A correlation between the optical and the structural properties is herein presented.

Oligomerizing ability of newly made human Hsp60 with its mitochondrial import signal

It is currently accepted that the human Hsp60 resides and works not only in the mitochondria, the canonical residence, but also outside it. It is also known that Hsp60 although coded by a nuclear gene is synthesized in the cytosol and includes an N-terminal mitochondrial import signal (MIS), which directs the polypeptide toward the inside of the organelle where the MIS is removed. Therefore, there are at least two functional types of Hsp60, with and without MIS, the former in the cytosol the latter inside the mitochondria. A key question is: how do these two forms of Hsp60 differ beyond the fact that while one has MIS the other lacks it? How presence or absence of MIS affects the ability of Hsp60 to form oligomers, which are considered important for chaperoning peptides and assist them to reach a native state? We report here our initial observations on this issue. Typically, in the mitochondria, Hsp60 forms ring-shaped heptamers, two of which associate to build a barrel-shaped tetradecamer, the functional chaperoning complex. It is not known if the cytosolic Hsp60 with its MIS, also forms hepta- and tetradecamers. A clarification of this issue will most likely shed light on the physiological functions of extramitochondrial Hsp60, and also on its pathogenic role in Hsp60 chaperonopathies. Consequently, we compared recombinant Hsp60 bearing the MIS with the prokaryotic ortholog GroEL, which under normal conditions forms functional double-ring tetradecamers. Characteristic hydrodynamic sizes of the oligomeric complex for both systems were investigated by small angle X-ray (SAXS) and static and dynamic light scattering (SLS and DLS) in solution under similar physicochemical conditions. High Performance Liquid Chromatography (HPLC) and blue native polyacrylamide-gel electrophoresis were used to further clarify the equilibrium between the different oligomeric species of the two proteins over a wide range of concentrations. Hsp60 with MIS formed hepta- and tetradecamers similarly to GroEL. Oligomerization was dependent on concentration for GroEL and Hsp60, but for the latter, formation of larger oligomers, e.g., tetradecamers, required higher concentrations than the former.