Biomedical subjects

Massimiliano Valentini

Publications and source records attributed to Massimiliano Valentini.

5 recordsLinked to original sources

PubMed2006

In situ and frontal polymerization for the consolidation of porous stones: a unilateral NMR and magnetic resonance imaging study.

Consolidation treatment of porous materials was performed by in situ and frontal polymerization of acrylic monomers inside a porous stone. To study the penetration of the polymer inside the stone and its consolidating effects we used water as a contrast agent, detecting its penetration using unilateral NMR and magnetic resonance imaging. All data obtained on differently treated stones were compared with corresponding ones obtained analyzing both untreated stones and stones simply painted with a well-known polymeric protective agent. In situ polymerization of acrylic monomers inside porous stones has been demonstrated to be an extremely powerful consolidating method, whereas thermally initiated frontal polymerization seems less efficient. In both cases the optimal choice of monomers is still open and requires further study. Our data indicate that unilateral NMR represents an inexpensive and simple technique for the non-invasive observation of the water uptake and of the effect of consolidation procedures in porous materials.

Acrylates↗

PubMed2006

Investigating the interactions of hyaluronan derivatives with biomolecules. The use of diffusional NMR techniques.

[Chemical structure: see text] The interactions between a biomaterial and biomolecules present in body fluids often determine the fate of the biomaterial. This paper presents a study on hyaluronan (HA)-containing materials (in soluble or colloidal form) that focuses on their interactions with lipids and proteins and for the first time uses PFG NMR as an analytical technique for probing these events. The interactions of HA-based polymers with phospholipids (DPPC and DPPG liposomes) are shown to depend both on charge and hydrophobicity factors. Despite the difference in behavior between albumin (substantially non-adhesive) and fibrinogen (adhesive), the interactions of the polymers with proteins do not seem to be based on hydrophobic effects but on surface polar interactions.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2004

Diffusion NMR spectroscopy for the characterization of the size and interactions of colloidal matter: the case of vesicles and nanoparticles.

We report the application of the pulse gradient spin-echo (PGSE) NMR technique (PGSE NMR) to the analysis of large colloidal materials, specifically vesicles formed from macromolecular amphiphiles and nanoparticles. Measurements of size and size distribution were demonstrated to be comparable to those obtained through dynamic light scattering or hydrodynamic chromatography. In comparison to these more common analytical methods, the use of PGSE NMR is particularly advantageous in that, as a spectroscopic technique, it adds chemical selectivity to the study of physical dimensions. In this way, chemically different species contemporarily present in a sample may be individually studied. In addition, we demonstrate the use of PGSE NMR to probe the existence of equilibria between macroamphiphiles present in solution and those present in vesicles or on the surface of nanoparticles. This feature in particular opens exciting possibilities for the characterization of the phase behavior and of the surface adsorption phenomena of colloids.

Colloids↗

PubMed2004

Oxidation-responsive polymeric vesicles.

Vesicles formed in water by synthetic macro-amphiphiles have attracted much attention as nanocontainers having properties that extend the physical and chemical limits of liposomes. We sought to develop ABA block copolymeric amphiphiles that self-assemble into unilamellar vesicles that can be further oxidatively destabilized. We selected poly(ethylene glycol) (PEG) as the hydrophilic A blocks, owing to its resistance to protein adsorption and low toxicity. As hydrophobic B blocks, we selected poly(propylene sulphide) (PPS), owing to its extreme hydrophobicity, its low glass-transition temperature, and most importantly its oxidative conversion from a hydrophobe to a hydrophile, poly(propylene sulphoxide) and ultimately poly(propylene sulphone). This is the first example of the use of oxidative conversions to destabilize such carriers. This new class of oxidation-responsive polymeric vesicles may find applications as nanocontainers in drug delivery, biosensing and biodetection.

Hydrogen Peroxide↗

PubMedDate not supplied

Characterization of methylprednisolone esters of hyaluronan in aqueous solution: conformation and aggregation behavior.

Methylprednisolone steroid esters of hyaluronan differing in degree of functionalization and molecular weight were investigated in aqueous solution. Conformation and aggregation phenomena were elucidated by means of circular dichroism, viscometry, rheology, and nuclear magnetic resonance, mainly by (1)H pulsed field gradient (PFG) NMR, which allows the determination of the diffusion coefficient of the species under investigation. The functionalization of hyaluronan with the steroid induces a reduction of the molecular volume, as a consequence of intramolecular hydrophobic interactions. For concentrated samples we have observed the coexistence of unimolecular collapsed chains and of aggregates, the latter disappearing upon dilution. The methylprednisolone ester of lower molecular weight hyaluronan has a larger molecular volume than its higher molecular weight analogue, even though still smaller than the underivatized polymer. This effect can be explained with the reduced flexibility of the polymer backbone probably impairing intramolecular interactions.

Esters↗