Morphological and Mechanical Characterization of P-Scaffolds with Different Porosity

The aim of this paper is to model and to compare the results of the mechanical characterization, carried out on numerical models and real specimens, of uniform P-scaffolds with different porosity values. The analysis includes the morphological characterization of 3D printed specimens and the implementation of a FEM shell model to reproduce a compressive test suitable for mechanical properties evaluation of PLA scaffolds. Young modulus and yield strength were also obtained, in order to verify the numerical model accuracy, by experimental tests on 3D printed PLA scaffolds. Numerical results showed that the shell model was able to reproduce, more efficiently compared to a solid model proposed in a previous work, both elastic and plastic behavior of the scaffolds, providing elastic modulus values very close to the experimental ones. On the other hand, the not very high quality of the 3D printing, detected by MicroCT analysis, caused a significant dispersion in the yield strength numerical values respect to the real data. Anyway, an inverse correlation between mechanical properties and porosity was found as expected. The elastic modulus values were similar to the typical values of the trabecular bone for whose regeneration this kind of scaffolds is usually employed

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

Cellulose Acetate and Cardanol Based Seed Coating for Intraspecific Weeding Coupled with Natural Herbicide Spraying

Abstract: Agricultural pesticides can become persistent environmental pollutants and their use is destined to be reduced. Consequently, weed control is shifting to green products and strategies. A combined approach, made of pelargonic acid based herbicide spraying and interspecific competition (i.e. seeding of plants species competing for growth against weeds) could boost the weeding effect. In case of the contemporary seeding and spraying, needed to reduce costs, seed coating is necessary as barrier to herbicide toxic effects but, at the same time, the coating has to be endowed with the right features to allow germination. This work aims to verify the feasibility of using cellulose acetate/cardanol (CA/Card) as seed coating polymer–plasticizer blend and to identify possible relationship between material features and germination rate. For these purposes, untreated and pelargonic acid herbicide treated coated seeds coated through solvent evaporation methods (CA/Card ratios from 0/0 to 100/0) were subjected to germination test. Coatings were characterized through SEM, EDX, media uptake, DSC and mechanical analysis with and without conditioning in seeding conditions. Germination test showed that 70/30 seeds, treated and untreated with herbicide, presented the best germination rate. Germination assays showed that coating presence reduced and slowed (without stopping) seeds germination equally with and without herbicide treatment. Consequently, was possible to conclude that CA/Card coatings allowed germination and presented a barrier effect against herbicide. Thus coating resulted suitable for seed coating in herbicide spraying/interspecific combined applications. No strong correlations were found between material features and germination, but it is plausible to hypothesize that both water absorption and mechanical properties of the coating play an important role and have to be optimized to improve germination rate avoiding difficulty in sprouting. Finally, the study opened a new perspective in the use of cellulose acetate for seed coating from waste sources such as cigarette filters. Graphic Abstract: [Figure not available: see fulltext.]

Investigations of processing–induced structural changes in horse type-i collagen at sub and supramolecular levels

The aim of this work is to evaluate the effects of different extraction and material processing protocols on the collagen structure and hierarchical organization of equine tendons. Wide and Small Angle X-ray Scattering investigations on raw powders and thin films revealed that not only the extraction and purification treatments, but also the processing conditions may affect the extent of the protein crystalline domain and induce a nanoscale “shield effect.” This is due to the supramolecular fiber organization, which protects the atomic scale structure from the modifications that occur during fabrication protocols. Moreover, X-ray analyses and Fourier Transform Infrared spectroscopy performed on the biomaterial sheds light on the relationship between processing conditions, triple helical content and the organization in atomic and nanoscale domains. It was found that the mechanical homogenization of the slurry in acidic solution is a treatment that ensures a high content of super-organization of collagen into triple helices and a lower crystalline domain in the material. Finally, mechanical tensile tests were carried out, proving that the acidic solution is the condition which most enhances both mechanical stiffness and supramolecular fiber organization of the films

A multi-element psychosocial intervention for early psychosis (GET UP PIANO TRIAL) conducted in a catchment area of 10 million inhabitants: study protocol for a pragmatic cluster randomized controlled trial

Multi-element interventions for first-episode psychosis (FEP) are promising, but have mostly been conducted in non-epidemiologically representative samples, thereby raising the risk of underestimating the complexities involved in treating FEP in 'real-world' services

A possible method to avoid skin effect in polymeric scaffold produced through thermally induced phase separation

Scaffold's morphology and in particular pore architecture is a key parameter for cell viability and tissue regeneration. Usually, morphology is managed through Thermally Induced Phase Separation (TIPS) consisting of controlled quenching and freeze-drying to remove ice crystals to create porosity. Nevertheless, the so-called skin effect, a less-/non-porous layer, usually occurring at scaffold's air-liquid or material-mold interface. Skin effect reduces scaffold's performance then the layer have to cut out with consequent loss of material and damage risks. Here, it is presented a possible method to avoid skin effect at mold-polymer interface in biopolymer-based scaffolds. It is based on producing scaffolds not directly in a mold but on a previously frozen distilled water surface. SEM analysis showed the absence of skinned surfaces and a uniform pore pattern in shape and size

Tuning the Porosity of Collagen-based Scaffolds for Use as Nerve Regenerative Templates

Regenerative medicine aims at inducing the formation of physiological tissues, in cases where the spontaneous healing response following a severe injury or disease leads to wound closure via contraction and synthesis of scar or fibrotic tissue. The suppression of both wound contraction and scar synthesis, with the simultaneous synthesis of physiological tissues, might be achieved by implanting a porous macromolecular scaffold within the site of injury, able to host cells and guide their behavior toward regeneration. Tubular scaffolds, reconnecting the proximal and distal stumps of a transected peripheral nerve, demonstrated to be able to induce regeneration of the lost nerve trunk. Experimental evidence from independent investigations shows that protein-permeable porous tubes, of different types, perform better as regenerative templates when their pore size is also cell-permeable (>10 mu m). Moreover, the regenerative potential of the porous conduit may be further enhanced when inserting a substrate with longitudinally oriented pores within it, since such an oriented construct provides physical support and guide to the growth of neural structures across the site of injury. This study focused on the production of collagen-based conduits and matrices with a micropatterned porosity, suitable for use as nerve regenerative templates. The manufacturing techniques for the production of tubular and cylindrical scaffolds, with controlled pore size and orientation, were based on a freeze-drying process. Tubular scaffolds possessed a radially oriented porosity with a radial gradient of pore sizes, ranging from cell-permeable pores at the inner tube wall to cell-impermeable pores at the outer one. Cylindrical scaffolds exhibited nearly axially oriented pores, with a pore size depending on the freezing rate as well as on the collagen concentration. Due to their peculiar porous structures, such scaffolds are expected to enhance the regenerative capacity of transected peripheral nerves as well as to lead to a better understanding of the cellular mechanisms underlying peripheral nerve regeneration

Biocompatibility and other properties of hydrogels in regenerative medicine

The word ‘gel’ refers to a wide class of materials displaying a high capability of absorbing and retaining a liquid medium. Hydrogels are defined as a particular type of macromolecular gels, formed via chemical or physical stabilization of the polymer chains into a three- dimensional network, for which the absorbed liquid is water or a water solution. The hydrophilic nature of hydrogels gives them unique properties in terms of biocompatibility, rubbery mechanical properties similar to those of soft tissues, and mild-gelling conditions, that are suitable for drug delivery and cell transplantation strategies. Moreover, the strong sensitivity to certain environmental stimuli, displayed by some hydrogels in terms of reversible swelling/deswelling phase transitions, makes them particularly attractive as smart materials for use in a wide range of applications. In this chapter, we introduce the theory describing the sorption thermodynamics of chemical hydrogels, discussing the relationships between their microstructural parameters and the resulting macroscopic properties. Various approaches to evaluate the most relevant network parameters affecting the hydrogel swelling capability and mechanical stiffness will be discussed. It is worth noting that the same theory, traditionally formulated for chemical hydrogels, might be applied to describe the behaviour of physical hydrogels as well