Francesca Scalera

Potential of Cellulose-Based Superabsorbent Hydrogels as Water Reservoir in Agriculture

The present work deals with the development of a biodegradable superabsorbent hydrogel, based on cellulose derivatives, for the optimization of water resources in agriculture, horticulture and, more in general, for instilling a wiser and savvier approach to water consumption. The sorption capability of the proposed hydrogel was firstly assessed, with specific regard to two variables that might play a key role in the soil environment, that is, ionic strength and pH. Moreover, a preliminary evaluation of the hydrogel potential as water reservoir in agriculture was performed by using the hydrogel in experimental greenhouses, for the cultivation of tomatoes. The soil-water retention curve, in the presence of different hydrogel amounts, was also analysed. The preliminary results showed that the material allowed an efficient storage and sustained release of water to the soil and the plant roots. Although further investigations should be performed to completely characterize the interaction between the hydrogel and the soil, such findings suggest that the envisaged use of the hydrogel on a large scale might have a revolutionary impact on the optimization of water resources management in agriculture.

Bio-Hybrid Scaffolds for Bone Tissue Engineering: Nano-Hydroxyapatite/Chitosan Composites

Natural bone ECM is a hierarchical nanocomposite made of an inorganic phase deposited within an organic matrix. In order to mimic the bone highly organized hybrid structure and functionality, strategies that allow assembling ceramic and polymer phase can be applied. To this aim, we investigated an insitu growth method able to nucleate a nanoHydroxyapatite (nHAp) phase into and around the interconnected porous structure of chitosan sponges. By increasing the calcium and phosphate concentration in the meta-stable solution used for the nHAp nucleation, the inorganic phase raised proportionally, in the range 10%-30% wt. In order to be compared with nHAp loaded scaffolds, pure chitosan samples have been produced by cross-linking biopolymer with arginine. Moreover, nHAp loaded samples, containing the 20 % wt of inorganic phase have been prepared by simply mixing low crystalline nHAp powders with the chitosan gel. The in situ nucleation method highlighted evident advantages in terms of nanophase distribution and mechanical performances with respect to a merely mixing procedure.

3D printing of hydroxyapatite polymer-based composites for bone tissue engineering

Abstract Skeletal defects reconstruction, using custom-made substitutes, represents a valid solution to replacing lost and damaged anatomical bone structures, renew their original function, and at the same time, restore the original aesthetic aspect. Rapid prototyping (RP) techniques allow the construction of complex physical models based on 3D clinical images. However, RP machines usually work with synthetic polymers; therefore, producing custom-made scaffolds using a biocompatible material directly by RP is an exciting challenge. The aim of the present work is to investigate the potentiality of 3D printing as a manufacturing method to produce an osteogenic hydroxyapatite-polylactic acid bone graft substitute.

Development of a Novel Hybrid Porous Scaffold for Bone Tissue Engineering: Forsterite Nanopowder Reinforced Chitosan

In order to induce bone regeneration several natural and synthetic materials have been proposed. However, single-phase scaffolds present some insurmountable disadvantages such as poor mechanical strength or brittleness and too low or too high degradation rate. In order to overcome these drawbacks, composite systems can be an interesting and promising option. In the present work a novel hybrid porous scaffold for bone tissue engineering is proposed. Chitosan/Forsterite (Ch/FS) composite scaffolds were prepared by freeze-drying method using a chitosan/forsterite ratio of 90/10. The FS nanopowder (Mg2SiO4) is synthesized using a simple solgel based method. The FS composition was checked by XRD analysis. The macrostructure of the Ch/FS scaffolds were analyzed by SEM, the FS distribution within the chitosan matrix observed by EDS, the mechanical strength measured by compression test in PBS and the biocompatibility of the composite on human osteosarcoma cell line (MG-63) verified by MTT assay after 48 hours. The porosity appears interconnected and with a pore size ranging from 1 to 100 μm. The FS is overall distributed within the chitosan matrix. The compression strength of composite scaffolds increased with respect to the pure chitosan scaffolds of more than two times (from 0.8 to 1.9 KPa) and the composites did not show any toxicity effect on human osteosarcoma cells.

Development and Mechanical Characterization of a Collagen/Hydroxyapatite Bilayered Scaffold for Ostechondral Defect Replacement

In this work a novel three-dimensional ostechondral substitute is proposed that is made of an inorganic/organic hybrid material, namely collagen/hydroxyapatite. The two components of the substitute have been characterized separately. The inorganic part, a hydroxyapatite scaffold, was fabricated by a polymer sponge templating method using a reactive sub-micron powder synthesized in our laboratory by hydroxide precipitation sol-gel route. The organic part, a collagen scaffold, was fabricated by a freeze-dying technique varying design parameters. Both the parts were analysed by scanning electron microscopy and their mechanical properties assessed by compression tests. The hydroxyapatite scaffold showed a high and highly interconnected porosity and a mechanical strength equal to 0.55 MPa, higher than those reported in literature. The collagen scaffolds were seeded by chondrocytes, processed for histology analysis and tested in compression. The biological tests proved the ability of the scaffolds to be positively populated by chondrocytes and the mechanical analysis showed that the mechanical strength of the scaffolds significantly increased after 3 weeks of culture.

Mechanical Performance and In Vitro Studies of Hydroxyapatite/Wollastonite Scaffold for Bone Tissue Engineering

A highly porous (~90%) interconnected hydroxyapatite/wollastonite (HA/WS) scaffolds were prepared by polymeric sponge replica method using a slurry containing HA:Calcium silicate in the weight ratio of 50:50 and sintered at 1300 °C. The phase purity of the scaffolds were analyzed by using XRD. The pore size, pore structure, microstructure and elemental analysis of the scaffolds before and after SBF soaking were analyzed using SEM and EDS. In-vitro bioactivity and bioresorbability confirmed the feasibility of the developed scaffolds. The HA/WS scaffold shows two fold increase in the compressive strength compared to pure HA scaffold.

Strategies to Improve Bioactivity of Hydroxyapatite Bone Scaffolds

Two different approaches are proposed in this study to enhance the bioactivity of hydroxyapatite-based scaffolds for bone tissue regeneration. The first method consists in a structural modification of Hydroxyapatite (HA) through doping it with Magnesium (1,3% wt) while the second one in using HA in combination with a calcium silicate, i.e. Wollastonite (WS), to form a composite bioceramic. Scaffolds with high and strongly interconnected porosity (pores ranging from 300 to 800 µm) were produced throughout both procedures. Higher mechanical properties in compression were obtained when the composite Ws/HA bioceramic was adopted. That one showed a weight loss after 6 months in physiological solution seven times higher than doped HA. Preliminary in vitro tests highlighted that both kinds of scaffold allowed the adhesion of MG63, without significant differences in terms of vitality, indicating a good biocompatibility of both used biomaterials.

Synthesis of Chitosan-Based Sub-Micrometric Particles by Simple Coacervation

Due to its intrinsic biocompatibility, degradability, and antibacterial properties, chitosan is widely explored for biomedical and pharmaceutical applications, especially for the development of tissue engineering scaffolds and controlled drug delivery systems. In this work, physically crosslinked chitosan-based particles with submicrometric size were synthesized by means of a modified coacervation process, starting from aqueous solutions differing for the chitosan molecular weight and concentration. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyse the particle morphology and the mean diameter yielded by the different synthesis parameters. Daily DLS measurements were also performed to monitor the expected swelling of the particles in a buffer solution, up to four days of storage. The experimental findings showed that submicrometric chitosan particles, with an average diameter in the range 150-400 nm, could be successfully produced, with both chitosan molecular weight and concentration affecting the particle size. Moreover, the smallest particles, among those synthesized, were found to be stable in water solutions up to three days. This seems to suggest the potential of the investigated particles for short-term biomedical applications, e.g., controlled drug delivery over time windows ranging from hours to days.

Influence of the Precipitation Temperature on Properties of Nanohydroxyapatite Powder for the Fabrication of Highly Porous Bone Scaffolds

The aim of the present work is to study the influence of the precipitation temperature in the synthesis of nanohydroxyapatite (n-HAp) on the properties of the resulting n-HAp powder for the fabrication of highly porous scaffolds for bone tissue engineering. The n-HAp powder was obtained by a wet precipitation technique starting from calcium nitrate tetrahydrate (Ca (NO3)2*4H2O) and phosphoric acid (H3PO4) at different temperatures: 10°C, 37°C and 50°C. Highly porous scaffolds were fabricated using the three different powders by the sponge replica method and sintering at 1300°C. Combined X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses on powders indicated that on increasing the precipitation temperature the formation of pure n-HAp is accelerated, without significant changes in particles morphology and size. Scaffolds characterized by high porosity (89%) and good compressive strength (0.53 MPa for n-HAp prepared at 37°C) were obtained. XRD analyses on sintered n-HAp confirmed the thermal stability of the material. Therefore, the as-synthesized n-HAp powder can be successfully used for the fabrication of highly porous scaffolds as bone substitutes.

Tissue engineering for cartilage repair: in vitro development of an osteochondral scaffold. Abstracts of the 3rd TERMIS (Tissue Engineering & Regenerative Medicine International Society) World Congress 2012. September 5-8, 2012. Vienna, Austria

Adequate cellular in-growth into biomaterials is one of the fundamental requirements in regenerative medicine. Type-I-collagen is the most commonly used material for soft tissue engineering, because it is nonimmunogenic and a highly porous network for cellular support. However, adequate cell in-growth and cell seeding has been suboptimal. Different densities of collagen scaffolds (0.3% to 0.8% (w/v)) with/without polymer knitting (poly-caprolactone (PCL)) were prepared. The structure of collagen scaffolds was characterized using scanning electronic microscopy (SEM) and HE staining. The mechanical strength of hybrid scaffolds was determined using tensile strength analysis. Cellular penetration and interconnectivity were evaluated using fluorescent bead distribution and human bladder smooth muscle cells and urothelium seeding. SEM and HE analysis showed the honeycomb structure and the hybrid scaffolds were adequately connected. The hybrid scaffolds were much stronger than collagen alone. The distribution of the beads and cells were highly dependent on the collagen density: at lower densities the beads and cells were more evenly distributed and penetrated deeper into the scaffold. The lower density collagen scaffolds showed remarkably deeper cellular penetration and by combining it with PCL knitting the tensile strength was enhanced. This study indicated that a 0.4% hybrid scaffold strengthened with knitting achieved the best cellular distribution.Human adult heart harbors a population of resident progenitor cells that can be isolated by Sca-1 antibody and expanded in culture. These cells can differentiate into cardiomyocytes and vascular cells in vitro and contribute to cardiac regeneration in vivo. However, when directly injected as single cell suspension, the survival rate and retention is really poor, less than 1% of injected cells being detectable in the hosttissue within few weeks. The present study aimed at investigating the possibility to produce scaffoldless, thick cardiac progenitor cell-derived cardiac patches by thermo-responsive technology. Human cardiac progenitors obtained from the auricles of patients were cultured as scaffoldless engineered tissues fabricated using temperature-responsive surfaces obtained by poly-N-isopropylacrylamide (PNIPAAm) surface immobilization. In the engineered tissue, progenitor cells established proper three-dimensional intercellular relationships and produced abundant extracellular matrix, while preserving their phenotype and plasticity. Cell phenotype and viability within the 3D construct were followed for 1 week, showing that no significant differentiation or apoptotic events occurred within the construct. After engineered tissues were leant on visceral pericardium, a number of cells migrated into the myocardium and in the vascular walls, where they integrated in the respective textures. The study demonstrates the suitability of such approach to deliver stem cells.Spinal cord injury and repair is one of the important focus areas in tissue regeneration. Mechanical trauma caused due to factors such as contusion, compression or involuntary stretching induce post-traumatic secondary tissue damage in many Spinal Cord Injury (SCI) patients. Therefore, there is a need for scaffolds that provide a conducive threedimensionsal (3D) environment for injured cells to attach and grow. In this study we propose to synthesize 3D polymeric scaffolds in order to study the mechanical and adhesive properties & the nature of the interactions between hyaluronan-based (HY) biomaterials and cells and tissues both in vitroandin vivo. Here we have synthesized 3D HY-based hydrogels with robust mechanical and adhesive properties and demonstrate the use of this material for neuronal-related applications such as the treatment of SCI. Cell culture and survivability studies were done with NSC-34 cells. Live/Dead assay performed on the cells revealed significant differences in the staining of live cells and showed increased viability and proliferation. The number of live cells in the HY-based hydrogels with 0.1% collagen showed higher cell numbers compared with the other hydrogels. In this study we show that Injectable HYbased hydrogels with high elasticity, comparable to the mechanical properties of nervous tissue have been used in this study to study their biocompatibility and neuroprotective properties and they show better affinity for neuronal cells.Calcium phosphates (CaP) obtained by biomineralisation in Simulated Boby Fluid have been used for decades to assess the mineralisation capability of biomaterials. Recently, they have been envisioned as potential agents to promote bone formation. In this study, we have fabricated and coated with calcium phosphate melt electrospun scaffolds whereby macropores permit adequate cell migration and nutrient transfer. We have systematically investigated the effect of coating and osteoinduction onto the response of ovine osteoblasts and we observed that the coating up-regulated alkaline phosphatase activity regardless of the in vitro culture conditions. Micro Computed Tomography revealed that only scaffolds cultured in an osteoinductive cocktail were capable of depositing mineralised matrix, and that CaP coated scaffolds were more efficient at promoting mineralisation. Theses scaffolds were subcutaneously implanted in athymic rats and this demonstrated that the osteoinduction was a pre-requisite for bone formation in this ectopic model. It showed that although the bone formation was not significantly different after 8 weeks, the CaP coated scaffolds were superior at inducing bone formation as evidenced by higher levels of mineralisation at earlier time points. This work demonstrated that CaP coating is not sufficient to induce bone formation; however the combination of osteoinduction and CaP coating resulted in earlier bone formation in an ectopic model.Introduction: Bladder regeneration using minced bladder mucosa is an alternative to costly and time-consuming conventional in vitro culturing of urothelial cells. In this method, the uroepithelium ...