Maria Oliviero

Design of porous polymeric scaffolds by gas foaming of heterogeneous blends

One of the challenges in tissue engineering scaffold design is the realization of structures with a pre-defined multi-scaled porous network. Along this line, this study aimed at the design of porous scaffolds with controlled porosity and pore size distribution from blends of poly(ε-caprolactone) (PCL) and thermoplastic gelatin (TG), a thermoplastic natural material obtained by de novo thermoplasticization of gelatin. PCL/TG blends with composition in the range from 40/60 to 60/40 (w/w) were prepared by melt mixing process. The multi-phase microstructures of these blends were analyzed by scanning electron microscopy and dynamic mechanical analysis. Furthermore, in order to prepare open porous scaffolds for cell culture and tissue replacement, the TG and PCL were selectively extracted from the blends by the appropriate combination of solvent and extraction parameters. Finally, with the proposed combination of gas foaming and selective polymer extraction technologies, PCL and TG porous materials with multi-scaled and highly interconnected porosities were designed as novel scaffolds for new-tissue regeneration.

Thermoplastic Foams from Zein and Gelatin

Abstract The aim of this study was to characterize the foaming of natural proteins as thermoplastic polymers. In particular, two proteins, one of vegetal origin, zein, and one of animal origin, gelatin, were processed to achieve thermoplastic polymers, and subsequently foamed by a gas foaming batch process. The effects of suitable plasticizing additives and melt-mixing process on the thermal and mechanical properties of the thermoplasticized proteins were evaluated to assess the thermoplastic characteristics of these materials. Furthermore, selected protein/plasticizers systems were foamed with mixtures of CO2 and N2 as blowing agents, in a batch foaming apparatus, at different temperatures, pressures and pressure drop rates, to evaluate the processing window and the final properties of the foams. Foams with densities of 0.1 g/cm3 and morphologies characterized by uniform distributions of cells with 10 μm diameters were obtained. Results indicated the suitability of zein and gelatin for being processed with classical thermoplastic processing technologies including melt mixing and foaming and their potentials as biodegradable polymers.

Design of novel three-phase PCL/TZ-HA biomaterials for use in bone regeneration applications

The design of bioactive scaffold materials able to guide cellular processes involved in new-tissue genesis is key determinant in bone tissue engineering. The aim of this study was the design and characterization of novel multi-phase biomaterials to be processed for the fabrication of 3D porous scaffolds able to provide a temporary biocompatible substrate for mesenchymal stem cells (MSCs) adhesion, proliferation and osteogenic differentiation. The biomaterials were prepared by blending poly(ε-caprolactone) (PCL) with thermoplastic zein (TZ), a thermoplastic material obtained by de novo thermoplasticization of zein. Furthermore, to bioactivate the scaffolds, microparticles of osteoconductive hydroxyapatite (HA) were dispersed within the organic phases. Results demonstrated that materials and formulations strongly affected the micro-structural properties and hydrophilicity of the scaffolds and, therefore, had a pivotal role in guiding cell/scaffold interaction. In particular, if compared to neat PCL, PCL–HA composite and PCL/TZ blend, the three-phase PCL/TZ–HA showed improved MSCs adhesion, proliferation and osteogenic differentiation capability, thus demonstrating potential for bone regeneration.

Effect of supramolecular structures on thermoplastic zein-lignin bionanocomposites.

The effect of alkaline lignin (AL) and sodium lignosulfonate (LSS) on the structure of thermoplastic zein (TPZ) was studied. Protein structural changes and the nature of the physical interaction between lignin and zein were investigated by means of X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy and correlated with physical properties. Most relevant protein structural changes were observed at low AL concentration, where strong H-bondings between the functional groups of AL and the amino acids in zein induced a destructuring of inter- and intramolecular interactions in α-helix, β-sheet, and β-turn secondary structures. This destructuring allowed for an extensive protein conformational modification which, in turn, resulted in a strong improvement of the physical properties of the bionanocomposite.

Microstructure, degradation and in vitro MG63 cells interactions of a new poly(ε-caprolactone), zein, and hydroxyapatite composite for bone tissue engineering

Novel biodegradable biomaterials were investigated for potential application in bone tissue engineering. The biomaterials were prepared by blending poly(ε-caprolactone) and thermoplastic zein, a corn protein, with or without the incorporation of hydroxyapatite particles. The biomaterials were characterized in vitro to assess the degradation in phosphate buffer saline for 56 days by monitoring weight change, morphology, wettability, and tensile properties. The interaction between the biomaterials and MG63 was evaluated by proliferation, morphological characterization, and osteogenic differentiation assays up to 28 days in in vitro cultures. The incorporation of thermoplastic zein within poly(ε-caprolactone) enhanced the hydrophilicity and degradability, while minor effects were observed after the inclusion of the hydroxyapatite particles. Compared to the neat poly(ε-caprolactone), the multiphase poly(ε-caprolactone)/thermoplastic zein–hydroxyapatite composite improved the osteogenic differentiation of MG63 cells and is being considered a candidate material for bone tissue engineering applications.

Effect of two kinds of lignins, alkaline lignin and sodium lignosulfonate, on the foamability of thermoplastic zein-based bionanocomposites

The aim of this study was to utilize zein, a protein from corn, to develop bioplastic formulations in combination with reactive additives based on ligninic compounds and to investigate the effects of these highly interactive additives on the foamability of zein. In particular, different amounts of alkaline lignin and sodium lignosulfonate were added to zein powder and poly(ethylene glycol) through melt mixing to achieve thermoplastic bio-polymers, which were subsequently foamed in a batch process, with a mixture of CO2 and N2 as blowing agent, in the temperature range 50–60°C. The materials before foaming were characterized by X-ray and Fourier transform infrared analysis to highlight the physico-chemical interactions and the eventual destructuration of the protein secondary structure. After foaming, density measurements, scanning electron microscopy and image analysis have been used in order to evaluate the porosity and the pore size distribution of the microstructure of the foams and to determine the effect of the ligninic compounds on the foamability of the bioplastic.

Bio-hybrid foams by silsesquioxanes cross-linked thermoplastic zein films

Hybrid materials, a new class of materials obtained by sol-gel approach and based on the nanoscale interaction between inorganic and organic phases, have recently gained large scientific and industrial attention. In this work, the material designing of zein hybrid materials with tailored properties is addressed to the production of zein hybrid foams by both gas foaming and supercritical carbon dioxide, CO2 drying. Hybrid materials have been produced from thermoplastic zein and 3-glycidoxypropyltrimethoxysilane by a two-step procedure including reactive melt mixing and a simultaneous sol-gel approach. Protein structural changes have been investigated by infrared spectroscopy and correlated with thermomechanical properties. The hybrid foams have been analyzed by scanning electron microscopy in order to evaluate the effect of silsesquioxanes domains on the porous structure. Hybrid microcellular foams with homogeneous cellular structures have been obtained by both foaming approaches. A bimodal structure with bubbles characterized by micrometric and nanometric sizes was obtained in hybrid foams obtained with CO2 drying.

Bio-based polyurethane foams from renewable resources

In the last decades, bio-derived natural materials, such as vegetable oils, polysaccharides and biomass represent a rich source of hydroxyl precursors for the synthesis of polyols which can be potentially used to synthesize “greener” polyurethane foams. Herein a bio-based precursor (obtained from succinic acid) was used as a partial replacement of conventional polyol to synthesize PU foams. A mixture of conventional and bio-based polyol in presence of catalysts, silicone surfactant and diphenylmethane di-isocyanate (MDI) was expanded in a mold and cured for two hours at room temperature. Experimental results highlighted the suitability of this bio-precursor to be used in the production of flexible PU foams. Furthermore the chemo-physical characterization of the resulting foams show an interesting improvement in thermal stability and elastic modulus with respect to the PU foams produced with conventional polyol.

Effect of compatibilization on the properties of in situ microfibrillar composites based on polylactic acid and polypropylene

The aim of this work was to explore the feasibility of using polypropylene (PP) as an reinforcing material for polylactide acid (PLA) based on the concept of in situ microfibrillar composites (iMFCs). Microfibers of PP were successfully generated by melt mixing, slit die extrusion and cold stretching. However, due to their immiscibility feature, the interfacial interaction between PP microfibers and PLA matrix is poor. In order to reduce the interfacial tension of the blend, PP-grafted with maleic anhydride was used as an interfacial compatibilizer. The effect of filler content on morphological appearance, mechanical and water vapor barrier properties were investigated. Results show the effect of the compatibilizer to stabilize the morphology developed during compounding and to enhance adhesion between the phases thus improving the properties of the obtained iMFCs.

Characterization of sustainable polyhydroxyls, produced from bio-based feedstock, and polyurethane and copolymer urethane-amide foams

This manuscript presents data related to the research article entitled “Synthesis and characterization of sustainable polyurethane foams based on polyhydroxyls with different terminal groups” (DOI: 10.1016/j.polymer.2018.06.077) [1]. We provide Supplementary data on the chemical properties, in terms of FTIR characterization, of polyhydroxyls produced starting from bio-based feedstock (biosuccinic acid and 1,4 butandiol) and thermal properties (glass transition temperature-Tg and thermal degradation behavior) of polyurethane and copolymer urethane-amide foams manufactured from the aforementioned polyhydroxyls. The FTIR characterization elucidates the chemical structure of polyhydroxyls and allows to make some hypothesis on their reaction routes with the isocyanate molecules. The thermal characterization revealed that the addition of bio-based polyhydroxyls to the sample formulations improves both the glass transition and degradation temperature of the foams. These foamed products exhibit potential performances to be applied as a substitute for conventional polyurethane foams.