Nicola Zanna

On the antibacterial activity of roots of Capparis spinosa L.

A decoction of Capparis spinosa L. roots, widely used in the traditional folk medicine of southern Italy, was prepared and submitted to antibacterial activity tests, which showed an interesting bacteriostatic activity on the growth of Deinococcus radiophilus. Heterocyclic compounds were also recovered from the chloroformic extract of the roots.

Thixotropic Peptide-Based Physical Hydrogels Applied to Three-Dimensional Cell Culture

Pseudopeptides containing the d-Oxd or the d-pGlu [Oxd = (4R,5S)-4-methyl-5-carboxyl-oxazolidin-2-one, pGlu = pyroglutamic acid] moiety and selected amino acids were used as low-molecular-weight gelators to prepare strong and thixotropic hydrogels at physiological pH. The addition of calcium chloride to the gelator solutions induces the formation of insoluble salts that get organized in fibers at a pH close to the physiological one. Physical characterization of hydrogels was carried out by morphologic evaluation and rheological measurements and demonstrated that the analyzed hydrogels are thixotropic, as they have the capability to recover their gel-like behavior. As these hydrogels are easily injectable and may be used for regenerative medicine, they were biologically assessed by cell seeding and viability tests. Human gingival fibroblasts were embedded in 2% hydrogels; all of the hydrogels allow the growth of encapsulated cells with a very good viability. The gelator toxicity may be correlated with their tendency to self-assemble and is totally absent when the hydrogel is formed.

Factors Affecting the Stabilization of Polyproline II Helices in a Hydrophobic Environment

Several parameters have a critical importance for the stabilization of either polyproline I (PPI) or polyproline II (PPII) helices in a hydrophobic environment. Among them, it was found out that the concentration is crucial as polyprolines at 3 mM concentration stably fold in PPII helices, that are organized in aggregates stable even after several days and are detectable by dynamic light scattering analysis. In more diluted concentration the same molecules stably fold in PPI helices, and no aggregates are found. In contrast, the introduction of a (4S,5R)-4-carboxy-5-methyloxazolidin-2-one (L-Oxd) moiety always inhibits the formation of the PPI helix, regardless of the L-Oxd position and the solution concentration.

Pseudopeptide‐Based Hydrogels Trapping Methylene Blue and Eosin Y

We present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc-l-Phe-d-Oxd-OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO-loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO-loaded hydrogel through π-π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO.

Self-healing hydrogels triggered by amino acids

Nine amino acids with different chemical properties have been chosen to promote the formation of hydrogels based on the bolamphiphilic gelator A: three basic amino acids (arginine, histidine and lysine), one acidic amino acid (aspartic acid), two neutral aliphatic amino acids (alanine and serine) and three neutral aromatic amino acids (phenylalanine, tyrosine and tryptophan). Although hydrogels are obtained under any conditions, strong and thermoreversible hydrogels are formed by the addition of Arg to the bolamphiphilic gelator. These hydrogels have physiological pH and self-healing properties and may be used for regenerative medicine applications.

Study on the interaction between gliadins and a coumarin as molecular model system of the gliadins-anthocyanidins complexes.

To clarify the conformational changes of gliadins (Glia) upon complexation with anthocyanidins (in particular cyanidin, Cya), the interaction of Glia with a coumarin derivative (3-ethoxycarbonylcoumarin, 3-EcC), having a benzocondensed structure similar to that of Cya, has been investigated by NMR, IR, and Raman spectroscopy under acidic and neutral conditions. Raman spectra showed that both molecules produce a similar effect on the Glia structure, i.e. an increase in the α-helix conformation and a decrease in β-sheet and β-turns content. In the presence of both molecules, this effect is more marked; the spectroscopic results showed that both Cya and 3-EcC interact with Glia and 3-EcC favors the complex formation with Glia. The results obtained in this study provide new insights into anthocyanidins-Glia interactions and may have relevance to human health, in the field of the attempts to modify gluten proteins to decrease allergen immunoreactivity.

Oxazolidinone-Containing Pseudopeptides: Supramolecular Materials, Fibers, Crystals and Gels.

The formation of fibers through self‐assembly is of particular interest, as fibrous proteins (such as collagen, keratin, actin, and so on) are involved in intra‐ and extracellular functions. To understand aggregation phenomena, oligopeptides may be designed and prepared either to mimic or to interfere with these processes. In this article, we will demonstrate that the introduction of the 4‐methyl‐5‐carboxy‐oxazolidin‐2‐one (Oxd) moiety inside a peptide chain favors the formation of fiber‐like materials organized either in β‐sheets or in supramolecular helices, provided that it is combined with other factors, like π‐stacking interactions and intermolecular NH•••OC bonds. The presence of the Oxd moiety is essential for the material formation: when Oxd is replaced with Pro, only liquids or amorphous solids are obtained. Remarkably, some of these molecules are low‐molecular‐weight gelators, as they induce the formation of both organogel and hydrogels that have been used for several applications.

Synthesis and structure analysis of ferrocene‐containing pseudopeptides

Ferrocene with its aromaticity and facile redox properties is an attractive moiety to be incorporated into functional moieties. Medicinal applications of ferrocene are well known and ferrocene itself shows cytotoxic and antianemic properties. In this article, we will describe the synthesis and the structure analysis of two pseudopeptides containing a ferrocene moiety as N‐terminal group. After purification, Fc‐l‐Phe‐d‐Oxd‐OBn [l‐Phel‐phenylalanine; d‐Oxd(4R,5S)‐4‐Methyl‐5‐carboxy‐oxazolidin‐2‐one] appears as bright brown solid that spontaneously forms brown needles. The X‐ray diffraction of the crystals shows the presence of strong π interactions between the ferrocenyl moiety and the phenyl rings, while no NH•••OC hydrogen bonds are formed. This result is confirmed by FT‐IR and 1H NMR analysis. In contrast, both FT‐IR and 1H NMR analysis suggest that Fc‐(l‐Phe‐d‐Oxd)2‐OBn forms a turn conformation stabilized by intramolecular NH•••OC hydrogen bonds in solution. Chiroptical spectroscopies (ECD and VCD) substantially confirmed the absence of a well‐defined folded structure. The presence of the Fc moiety is responsible for specific ECD signals, one of which displayed pronounced temperature dependence and is directly related with the helicity assumed by the Fc core. Solid‐state ECD spectra were recorded and rationalized on the basis of the X‐ray geometry and quantum‐mechanical calculations.

Biocompatible and Light-Penetrating Hydrogels for Water Decontamination

Solar light-activated photocatalyst nanoparticles (NPs) are promising environment-friendly low cost tools for water decontamination, but their dispersion in the environment must be minimized. Here, we propose the incorporation of TiO2-NPs (also in combination with graphene platelets) into highly biocompatible hydrogels as a promising approach for the production of photoactive materials for water treatment. We also propose a convenient fluorescence-based method to investigate the hydrogel photocatalytic activity in real time with a conventional fluorimeter. Kinetics analysis of the degradation profile of a target fluorescent model pollutant demonstrates that fast degradation occurs in the matrix bulk. Fluorescence anisotropy proved that small pollutant molecules diffuse freely in the hydrogel. Rheological and scanning electron microscopy characterization showed that the TiO2-NP incorporation does not significantly alter the hydrogel mechanical and morphological properties.

Peptide-Based Physical Gels Endowed with Thixotropic Behaviour

Thixotropy is one of the oldest documented rheological phenomenon in colloid science and may be defined as an increase of viscosity in a state of rest and a decrease of viscosity when submitted to a constant shearing stress. This behavior has been exploited in recent years to prepare injectable hydrogels for application in drug delivery systems. Thixotropic hydrogels may be profitably used in the field of regenerative medicine, which promotes tissue healing after injuries and diseases, as the molten hydrogel may be injected by syringe and then self-adapts in the space inside the injection site and recovers the solid form. We will focus our attention on the preparation, properties, and some applications of biocompatible thixotropic hydrogels.