Biomedical subjects

Emo Chiellini

Publications and source records attributed to Emo Chiellini.

8 recordsLinked to original sources

PubMed2006

Structure and energetics of biocompatible polymer nanocomposite systems: a molecular dynamics study.

Isothermal-isobaric (NPT) molecular dynamics simulations have been performed to investigate the structure, morphology, and energetics of polymer organoclay nanocomposites based on seven nonsteroidal antiinflammatory drugs (NSAIDs), two biocompatible polymers, and hydrotalcite as the clay mineral, both in an anhydrous and in a solvated environment. The results of our theoretical computations show that nanoconfined conformations of smaller NSAIDs are more affected by the presence of water molecules in the clay gallery with respect to their larger counterparts. Moreover, the presence of water in the mineral interlayer space decreases the interaction energy between the NSAID molecules and the clay, and this detrimental effect is further enhanced by the presence of polar moieties onto the NSAIDs. Finally, from the thermodynamics standpoint, the best intercalation results in a solvated environment could be obtained with PVA in the case of less polar drugs, while PHB could be the polymer of choice in the case of highly polar NSAIDs.

Aluminum Hydroxide↗

PubMed2004

Control of surface properties using fluorinated polymer brushes produced by surface-initiated controlled radical polymerization.

Surface-grafted styrene-based homopolymer and diblock copolymer brushes bearing semifluorinated alkyl side groups were synthesized by nitroxide-mediated controlled radical polymerization on planar silicon oxide surfaces. The polymer brushes were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and time-dependent water contact angle measurements. Angle-resolved XPS studies and water contact angle measurements showed that, in the case of the diblock copolymer brushes, the second block to be added was always exposed at the polymer-air interface regardless of its surface energy. Values of z*/Rg were estimated based on the radius of gyration, Rg, of the grafted homopolymer or block copolymer chains for the grafted brushes and thickness of the brush, z*. The fact that z*/Rg > 1 suggests that all these brushes are stretched. These results support the idea that after grafting the first block onto the surface the nitroxide-end capped polymer chains were able to polymerize the second block in a "living" fashion and the stretched brush so formed was dense enough that the outermost block in all cases completely covers the surface. NEXAFS analysis showed a relationship between the surface orientation of the fluorinated side chains and brush thickness with thicker brushes having more oriented side chains. Time-dependent water contact angle measurements revealed that the orientation of the side chains of the brush improved the surface stability toward reconstruction upon prolonged exposure to water.

Absorption↗

PubMed2004

Tapping mode AFM evidence for an amorphous reticular phase in a condensation-cured hybrid elastomer: alpha,omega-dihydroxypoly(dimethylsiloxane)/poly(diethoxysiloxane)/fumed silica nanoparticles.

A new surface phenomenon is reported for hybrid nanocomposites comprising (1) a low Tg poly(dimethylsiloxane) (PDMS) phase cross-linked by (2) a siliceous phase (SP) generated by in situ hydrolysis/condensation of poly(diethoxysiloxane) (PDES), and (3) fumed silica nanoparticles (FSN). After ambient temperature cure, tapping mode atomic force microscopy (TM-AFM) easily reveals near-surface FSN. For nanocomposites with higher PDES content, FSN surprisingly "disappear" after a further cure at 100 degrees C. The observation is explained by further condensation of extant siliceous fragments creating an amorphous reticular phase, which acts as a mechanical barrier between the FSN and the AFM tip.

Biocompatible Materials↗

PubMed2004

Characterization of surface NH3+Cl- groups on poly(styrene-co-Boc-aminostyrene) microspheres obtained by controlled acidic treatment.

Different samples of aminated latex of poly(styrene-co-Boc-aminostyrene) microspheres with mean diameters varying from 0.7 to 1.0 microm were prepared by dispersion copolymerization of styrene (ST) and Boc-aminostyrene (Boc-AMST). The copolymer compositions determined by nuclear magnetic resonance (1H NMR) were Boc-AMST/ST 6.9/93.1 mol/mol % (BOC7 sample) and Boc-AMST/ST 31.3/68.7 mol/mol % (BOC30 sample). The average molecular weights determined by gel permeation chromatography were 126 kDa (BOC7 sample) and 51 kDa (BOC30 sample). The latex containing NH-carbo-tert-butoxy groups (NH-Boc) were treated with 2 M HCl in isopropyl alcohol/water (1:1 vol/vol), at 50 degrees C for 3, 6, 9, 24, and 30 h, in order to control the extent of deprotection reaction of the NH-Boc. The deprotection reaction resulted in the formation of NH3+Cl- groups on the particle surfaces. The kinetic of the deprotection reaction was investigated by 1H NMR analyses and the yield varied from 20 to 40%. The resulting -NH3+Cl- groups on the microsphere surfaces were examined, in particular, by electron spectroscopy imaging (ESI) using an energy-filtered transmission electron microscope (EFTEM) that clearly demonstrated the presence of Cl on the particle surfaces. Scanning electron photomicrographs recorded for the above samples showed that the particle morphology was maintained after the acidic treatment.

Journal Article↗

PubMed2004

Environmentally degradable bio-based polymeric blends and composites.

Blends and composites based on environmentally degradable-ecocompatible synthetic and natural polymeric materials and fillers of natural origin have been prepared and processed under different conditions. Poly(vinyl alcohol) (PVA) was used as the synthetic polymer of choice by virtue of its capability to be processed from water solution or suspension as well as from the melt by blow extrusion and injection molding. Starch and gelatin were taken as the polymeric materials from renewable resources. The fillers were all of natural origin, as waste from food and agro-industry consisted of sugar cane bagasse (SCB), wheat flour (WF), orange peels (OR), apple peels (AP), corn fibres (CF), saw dust (SD) and wheat straw (WS). All the natural or hybrid formulations were intended to be utilized for the production of: a) Environmentally degradable mulching films (hydro-biomulching) displaying, in some cases, self-fertilizing characteristics by in situ spraying of water solutions or suspensions; b) Laminates and containers to be used in agriculture and food packaging by compression and injection molding followed by baking. Some typical prototype items have been prepared and characterized in relation to their morphological and mechanical properties and tested with different methodology for their propensity to environmental degradation and biodegradation as ultimate stage of their service life. A relationship between chemical composition and mechanical properties and propensity to biodegradation has been discussed in a few representative cases.

Biodegradation, Environmental↗

PubMed2004

Design of highly specific ligands of fibrin for therapeutic applications.

The work presented here is aimed at designing high-affinity ligands for the fibrin gamma (312-324) epitope. This epitope is specific for fibrin recognition, as it is exposed only on the fibrin surface, while in fibrinogen it is buried in the protein bulk. This property makes it very useful for therapeutic applications. In fact, it may be exploited in driving systems for targeted delivery of thrombolytic drugs toward the specific compartment where they are needed. It will then allow avoidance of serious unwanted side effects produced by a conventional systemic administration. The approach chosen for designing putative ligands is based on the known three-dimensional (3D) structure of the epitope. A wide virtual library made up of oligo-peptides and analogues designed by a combinatorial approach, on the basis of chemical complementarity criteria, has been screened by means of a docking/scoring approach (DOCK program). The peculiarity of the problem under study required a considerable effort in finding a method enabling the experimental validation of the design work results. In fact the selected biological target is absolutely new, so that neither a endogenous, nor a synthetic high-affinity ligand is known up to now. It does not allow for the validation of computational results by means of classical binding tests based on the use of known labeled high-affinity ligands. Preliminary binding essayes were so carried out by means of the Plasmon Surface Resonance (PSR) technique. The experimental results suggested that most of the molecules predicted to be good ligands by means of the selected computational tools, could carry the wanted affinity toward the selected target.

Amino Acid Sequence↗

PubMed2003

New perspectives for (S)-dolichol and (S)- nor dolichol synthesis and biological functions.

A procedure is described for the preparation of (S)-dolichol and (S)- nor dolichol starting from the polyprenyl fraction extracted from Gingko biloba integer or exhausted leaves. The procedure appears extremely valuable in obtaining the two chiral isoprenoid compounds in good chemical yields and retention of a high degree of enantiomeric excess. Also, the (S)- nor dolichol represents a good chiral precursor for the preparation of (14)C-labelled (S)-dolichol to be used in biological investigations into the (S)-dolichol catabolism in the functional living cell. Furthermore, the possible role of (S)-dolichol as a free radical scavenger in the cell membrane was preliminarily evaluated by means of a (1)H-NMR analytical method. Apparently, experimental results substantiate this hypothesis.

Animals↗

PubMedDate not supplied

Bio-based polymeric composites comprising wood flour as filler.

The increasing effort on development of bio-based polymeric materials in recent years is motivated by the basic concept of meeting the sustainability criteria for industrial development in the third millennium. Within this framework, our research group is currently involved in assessing the potentiality of some agro-industrial overproduction and byproducts in the formulation of eco-compatible bio-based polymeric materials displaying, among others, the propensity to biodegrade under controlled environment conditions. In the present work, beech wood flour (Bwf) composites were prepared from plasticized poly(3-hydroxybutyrate) (PHB). The type of plasticizer [tri(ethylene glycol) bis(2-ethylhexanoate) (TEGB) and poly(ethylene glycol) (PEG200)] and the amount [5 and 20 wt %] were selected as independent variables in a factorial design. Thermal and mechanical properties of 90 wt % PHB composites were investigated. Incorporation of PEG200 was found to compromise thermal stability of PHB as demonstrated by the higher decrease on the onset decomposition temperature (T(d)) and the drop in its average molecular weight (M(w)). The present study underlines the fact that TEGB/PHB/beech wood flour composites can be optimized to obtain new materials for disposable items.

Biodegradation, Environmental↗