Showing papers by "Piergiorgio Gentile published in 2012"

Bioactive glass/polymer composite scaffolds mimicking bone tissue.

Abstract: The aim of this work was the preparation and characterization of scaffolds with mechanical and functional properties able to regenerate bone. Porous scaffolds made of chitosan/gelatin (POL) blends containing different amounts of a bioactive glass (CEL2), as inorganic material stimulating biomineralization, were fabricated by freeze-drying. Foams with different compositions (CEL2/POL 0/100; 40/60; 70/30 wt %/wt) were prepared. Samples were crosslinked using genipin (GP) to improve mechanical strength and thermal stability. The scaffolds were characterized in terms of their stability in water, chemical structure, morphology, bioactivity, and mechanical behavior. Moreover, MG63 osteoblast-like cells and periosteal-derived stem cells were used to assess their biocompatibility. CEL2/POL samples showed interconnected pores having an average diameter ranging from 179 ± 5 μm for CEL2/POL 0/100 to 136 ± 5 μm for CEL2/POL 70/30. GP-crosslinking and the increase of CEL2 amount stabilized the composites to water solution (shown by swelling tests). In addition, the SBF soaking experiment showed a good bioactivity of the scaffold with 30 and 70 wt % CEL2. The compressive modulus increased by increasing CEL2 amount up to 2.1 ± 0.1 MPa for CEL2/POL 70/30. Dynamical mechanical analysis has evidenced that composite scaffolds at low frequencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E' and E″ at 1 Hz was observed, and for higher frequencies both moduli increased again. Cells displayed a good ability to interact with the different tested scaffolds which did not modify cell metabolic activity at the analyzed points. MTT test proved only a slight difference between the two cytotypes analyzed.

Biomimetic coating on bioactive glass-derived scaffolds mimicking bone tissue

Abstract: Bioceramic "shell" scaffolds, with a morphology resembling the cancellous bone microstructure, have been recently obtained by means of a new protocol, developed with the aim to overcome the limits of the conventional foam replication technique. Because of their original microstructure, the new samples combine high porosity, permeability, and manageability. In this study, for the first time, the novel bioactive glass shell scaffolds are provided with a gelatin-based biomimetic coating to realize hybrid implants which mimic the complex morphology and structure of bone tissue. Moreover, the presence of the coating completely preserves the in vitro bioactivity of the bioactive glass samples, whose surfaces are converted into hydroxyapatite after a few days of immersion in a simulated body fluid solution (SBF).

Processing and characterization of innovative scaffolds for bone tissue engineering.

Abstract: A new protocol, based on a modified replication method, is proposed to obtain bioactive glass scaffolds. The main feature of these samples, named "shell scaffolds", is their external surface that, like a compact and porous shell, provides both high permeability to fluids and mechanical support. In this work, two different scaffolds were prepared using the following slurry components: 59 % water, 29 % 45S5 Bioglass(®) and 12 % polyvinylic binder and 51 % water, 34 % 45S5 Bioglass(®), 10 % polyvinylic binder and 5 % polyethylene. All the proposed samples were characterized by a widespread microporosity and an interconnected macroporosity, with a total porosity of 80 % vol. After immersion in a simulated body fluid (SBF), the scaffolds showed strong ability to develop hydroxyapatite, enhanced by the high specific surface of the porous systems. Moreover preliminary biological evaluations suggested a promising role of the shell scaffolds for applications in bone tissue regeneration. As regards the mechanical behaviour, the shell scaffolds could be easily handled without damages, due to their resistant external surface. More specifically, they possessed suitable mechanical properties for bone regeneration, as proved by compression tests performed before and after immersion in SBF.

Layer-by-layer coating of photoactive polymers for biomedical applications

Abstract: Layer-by-layer (LbL) assembly is a versatile technique for the development of multilayered films with tailored characteristics at the nanometer scale. In this work, photoactive nanostructured films were prepared by LbL assembly of biocompatible photozymes: an anionic zwitterionic copolymer, poly(sodium styrene sulfonate-co-vinyl naphtalene-co-3-dimethyl(methacryloylethyl) ammonium propane sodium sulfonate; ZI) and a cationic polyelectrolyte, chitosan-g-fluorescein (CHFL) on a genipin-crosslinked gelatin substrate (G_GP). The correct organization of the multilayered coating was demonstrated by the static contact angle values, showing an alternate trend. FTIR–ATR spectra showed the main absorption bands of ZI, such as asymmetric (1125 and 1180 cm − 1 ) and symmetric (1036 cm − 1 ) O S O stretching and S O C stretching (1009 cm − 1 ), also confirmed by Energy-dispersive X-ray spectroscopy (EDS) spectra. UV–vis spectra showed the typical fluorescein absorbance peak of CHFL after the 8th layer, which intensity increased with increasing the even layer number. The absorption peak of G_GP (605–610 nm) probably masked the weak FL absorbance for coated samples with a lower layer number than 8. Scanning electron microscopy (SEM) results suggested the agglomerate presence on the coated surface. The obtained nanostructured films are expected to be promising candidates for carrying out efficient electron transfer process, responsible for the anti-microbial activity (ZI) or the osteointegration ability (CHFL) of the coating.

Biomimetic soluble collagen purified from bones

Abstract: Type I collagen has been extensively exploited as a biomaterial for biomedical applications and drug delivery; however, small molecular alterations occurring during the isolation procedure and its interaction with residual bone extracellular matrix molecules or proteins might affect the overall material biocompatibility and performance. The aim of the current work is to study the potential alterations in collagen properties and organization associated with the absence of proteoglycans, which mimic pathological conditions associated with age-related diseases. A new approach for evaluating the effect of proteoglycans on the properties of isolated type I collagen from the bone matrix is described. Additional treatment with guanidine hydrochloride was introduced to remove residual proteoglycans from the collagen matrix. The properties of the isolated collagen with/without guanidine hydrochloride treatment were investigated and compared with a commercial rabbit collagen as control. We demonstrate that the absence of proteoglycans in the isolated type I collagen affects its thermal properties, the extraction into its native structure, and its ability to hydrate and self-assemble into fibers. The fine control and tuning of all these features, linked to the absence of non-collagenous proteins as proteoglycans, offer the possibility of designing new strategies and biomaterials with advanced biomimetic properties aimed at regenerating bone tissue in the case of fragility and/or defects.

Bio-mimetic and biodegradable polymeric cement

Abstract: A biomimetic and biodegradable injectable polymeric cement is described, composed of a mixture comprising a first amount (Q 1 ) of at least one natural polymeric material containing at least one free amino group in the repeating unit; a second amount (Q 2 ) of at least one inorganic phase adapted to reinforce such natural polymeric material; and a third amount (Q 3 ) of at least one crosslinking agent able to react with such free amino groups in order to perform a cross-linking of such natural polymeric material.

Layer-by-layer as a tool to tailor the surface properties of biomedical devices

Abstract: As biomedical materials and implantable devices int eract with cells and biological fluids, it is fundamental to control the properties of interfaces between the material a nd the biological environment to address the organism resp onse towards a specific direction [1], by precisely desi gning surface chemistries [2], [3]. Dressings for wound h ealing should promote tissue regeneration avoiding scar fo rmation [4]. Among cardiovascular devices, stents should pr omote endothelialisation, avoid over- proliferation and m igration of smooth muscle cells to the implant site and prevent an excessive inflammatory response, which are the main reasons of neointimal proliferation and in-stent restenosis [5]. In this context, surface modification techniques are advant ageous, as they allow a modulation of surface properties, with out affecting bulk properties. The layer-by-layer (LbL) technique is a solvent-free process, for the surface coating of substrates of any size and shape with an uniform ultrathin mul tilayered film. LbL is based on the alternating exposure of a charged substrate to solutions of positively and negatively charged polyelectrolytes. A rinsing step is included betwee n each of the previously described process steps, to remove e xcess material as well as to prevent cross-contamination of the polyelectrolyte solutions [6]. In this work, poly(L-lactic acid) (PLLA) films and 316L stainless steel (SS) plates were modified through t he LbL technique, with heparin (HE)/chitosan (CH) and heparin/poly(diallyldimethylammonium chloride) (PDDA) polyelectrolyte couples, respectively. LbL coatings were developed for two different aims: (i) to confer ant ibacterial properties to wound healing dressings and (ii) antithrombogenic properties to cardiovascular stent devices. Successful polyelectrolyte deposition was verified by static contact angle and SPR analyses, while surface composition was characterized by XPS analysis. In vitro cell tests were performed to analyse the antithrombogenic propertie s of LbL-modified stainless steel substrates.