1,721,078 research outputs found
Biodegradable Polymers for Biomedical Additive Manufacturing
Full text linkThe tremendous interest received by additive manufacturing (AM) within the biomedical community is a consequence of the great versatility offered in terms of processing approach, materials selection, and customization of the resulting device. In particular the unparalleled control over structural and compositional features at the macro- and microscale, as a result of the large design freedom and high reproducibility, is making AM the technology of election for the fabrication of biodegradable medical devices. This article is aimed at providing an update overview of scientific literature on biodegradable polymers for AM application in the biomedical field. The main AM techniques applied so far to biodegradable polymers are outlined by presenting relevant materials processing requirements. The different classes of biodegradable polymers investigated for AM (i.e., proteins, polysaccharides, aliphatic polyesters of either natural or synthetic origin, polyurethanes, as well as other synthetic polymers under AM implementation) are described by highlighting their source of extraction, chemical modification, or synthesis route, and their physical-chemical and processing properties in relationship to AM. Relevant literature on their AM processing for medical and pharmaceutical applications is accordingly reviewed
Biomedical processing of polyhydroxyalkanoates
Full text linkThe rapidly growing interest on polyhydroxyalkanoates (PHA) processing for biomedical purposes is justified by the unique combinations of characteristics of this class of polymers in terms of biocompatibility, biodegradability, processing properties, and mechanical behavior, as well as by their great potential for sustainable production. This article aims at overviewing the most exploited processing approaches employed in the biomedical area to fabricate devices and other medical products based on PHA for experimental and commercial applications. For this purpose, physical and processing properties of PHA are discussed in relationship to the requirements of conventionally-employed processing techniques (e.g., solvent casting and melt-spinning), as well as more advanced fabrication approaches (i.e., electrospinning and additive manufacturing). Key scientific investigations published in literature regarding different aspects involved in the processing of PHA homo-and copolymers, such as poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), are critically reviewed
Computer-Aided Wet-Spinning
No full textComputer-aided wet-spinning (CAWS) has emerged in the past few years as a hybrid fabrication technique coupling the advantages of additive manufacturing in controlling the external shape and macroporous structure of biomedical polymeric scaffold with those of wet-spinning in endowing the polymeric matrix with a spread microporosity. This book chapter is aimed at providing a detailed description of the experimental methods developed to fabricate by CAWS polymeric scaffolds with a predefined external shape and size as well as a controlled internal porous structure. The protocol for the preparation of poly(ε-caprolactone)-based scaffolds with a predefined pore size and geometry will be reported in detail as a reference example that can be followed and simply adapted to fabricate other kinds of scaffold, with a different porous structure or based on different biodegradable polymers, by applying the processing parameters reported in relevant tables included in the text
Polymeric Hydrogels for In Vitro 3D Ovarian Cancer Modeling
No full textOvarian cancer (OC) grows and interacts constantly with a complex microenvironment, in which immune cells, fibroblasts, blood vessels, signal molecules and the extracellular matrix (ECM) coexist. This heterogeneous environment provides structural and biochemical support to the surrounding cells and undergoes constant and dynamic remodeling that actively promotes tumor initiation, progression, and metastasis. Despite the fact that traditional 2D cell culture systems have led to relevant medical advances in cancer research, 3D cell culture models could open new possibilities for the development of an in vitro tumor microenvironment more closely reproducing that observed in vivo. The implementation of materials science and technology into cancer research has enabled significant progress in the study of cancer progression and drug screening, through the development of polymeric scaffold-based 3D models closely recapitulating the physiopathological features of native tumor tissue. This article provides an overview of state-of-the-art in vitro tumor models with a particular focus on 3D OC cell culture in pre-clinical studies. The most representative OC models described in the literature are presented with a focus on hydrogel-based scaffolds, which guarantee soft tissue-like physical properties as well as a suitable 3D microenvironment for cell growth. Hydrogel-forming polymers of either natural or synthetic origin investigated in this context are described by highlighting their source of extraction, physical-chemical properties, and application for 3D ovarian cancer cell culture
Poly(3-hydroxybutyrate-co-3-hydroxyexanoate) scaffolds with tunable macro- and microstructural features by additive manufacturing
Full text linkPolymer microstructural engineering by additive manufacturing (AM) represents a powerful tool to functionalize tissue engineering scaffolds. This article reports on the processing of polymer/solvent/non-solvent ternary mixtures through their extrusion in a non-solvent bath as an innovative phase inversion-based AM approach to engineer poly(3-hydroxybutyrate-co-3-hydroxyexanoate) (PHBHHx) scaffolds porosity. The processing of PHBHHx mixtures with different chloroform/ethanol ratio into scaffolds characterized by a dual-scale porosity is described by highlighting how an interconnected network of macropores can be endowed with a tunable microporosity, formed a result of the phase inversion process governing polymer solidification. In particular, the study demonstrates that varying the non-solvent percentage in the ternary mixture represents an effective means to tailor the macropores size along scaffold vertical cross-section and the local micropores concentration in the polymer matrix. These structural changes are demonstrated to significantly affect scaffold overall porosity and tensile modulus, as well as its ability to support in vitro the proliferation of preosteoblast cells. The developed manufacturing strategy combines an advanced material engineering method effective on dual-scale size levels, with a modern approach to the sustainable processing of naturally-derived polyesters that minimizes the employment of halogenated solvents
Additive Manufacturing of Poly(3-hydroxybutyrate-co-3-hy-droxyvalerate)/Poly(D,L-lactide-co-glycolide) Biphasic Scaffolds for Bone Tissue Regeneration
No full textPolyhydroxyalkanoates are biopolyesters whose biocompatibility, biodegradability, environmental sustainability, processing versatility, and mechanical properties make them unique scaffolding polymer candidates for tissue engineering. The development of innovative biomaterials suitable for advanced Additive Manufacturing (AM) offers new opportunities for the fabrication of customizable tissue engineering scaffolds. In particular, the blending of polymers represents a useful strategy to develop AM scaffolding materials tailored to bone tissue engineering. In this study, scaffolds from polymeric blends consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(D,L-lactide-co-glycolide) (PLGA) were fabricated employing a solution-extrusion AM technique, referred to as Computer-Aided Wet-Spinning (CAWS). The scaffold fibers were constituted by a biphasic system composed of a continuous PHBV matrix and a dispersed PLGA phase which established a microfibrillar morphology. The influence of the blend composition on the scaffold morphological, physicochemical, and biological properties was demonstrated by means of different characterization techniques. In particular, increasing the content of PLGA in the starting solution resulted in an increase in the pore size, the wettability, and the thermal stability of the scaffolds. Overall, in vitro biological experiments indicated the suitability of the scaffolds to support murine preosteoblast cell colonization and differentiation towards an osteoblastic phenotype, highlighting higher proliferation for scaffolds richer in PLGA
PLA-BASED FOAMS AS SCAFFOLDS FOR TISSUE ENGINEERING APPLICATIONS
No full textIntroduction: The need for alternative solutions to meet the demand for replacement organs and tissue parts continues to drive advances in tissue engineering because no material meets all the design parameters in all applications, but a wide range of materials finds uses in different tissue engineering applications. In this research work, starting from biocomposites based on crosslinked particles of poly(acrylic acid) (SAP) and poly-L-lactic acid (PLLA), new open-pore PLLA-based foams with good physico-mechanical properties are produced in absence of organic solvents and chemical foaming agents.
Materials and methods: Biocomposites based on a binary system containing crosslinked particles of (SAP), commonly used as superabsorbent polymer, and PLLA have been prepared by melt-blending in a discontinuous mixer. Components were melt-mixed in different ratios in the presence of plasticizers and fibers or blended with different biopolymers such as poly (ethylene glycol) (PEG), poly (e-caprolactone) (PCL) and polyhydroxybutyrate (PHB). All samples were recovered from the mixing chamber and hot pressed using a laboratory compression molding machine to realize 0.2 mm thick sheets from which the specimens for mechanical tests were obtained.
Results: A fairly homogeneous dispersion of particles was obtained, as revealed by SEM micrographs, showed a biphasic system with a regular distribution of particles, with diameter ranging from 5 to 10 mm, within the PLLA polymeric matrix. This biphasic system also showed excellent swelling properties, demonstrating that cross-linked particles retain their superabsorbent ability even if distributed in a thermoplastic polymeric matrix. Furthermore, in aqueous environments the particles swell and are leached from PLLA matrix generating very high porosity with random and irregular open pore structure. Density and porosity were measured using liquid substitution method. As expected, reduced density and increased porosity were observed on the samples as a result of the increased amount of leached particles. The biocompatibility of all samples and the influence of the surface on cell behavior were assessed in a preliminary investigation which evidenced optimal cell viability, adhesion and proliferation.
Discussion: These new open-pore PLLA-based foams, produced in absence of organic solvents and chemical foaming agents, with good physico-mechanical properties appear very promising for scaffold production technology. In fact, open porosity is a crucial point because scaffold must possess a highly porous structure with a fully interconnected geometry to provide cell ingrowth and survival and uniform cell distribution. This new methodology allows to obtain a polymeric scaffold, with a porosity that can be easily tuned by a proper choice of superabsorbent particles. Another key point are surface properties, which include both chemical and topographical characteristics and can control and affect cellular adhesion and proliferation. The scaffold surface is the initial and primary site of interaction with surrounding cells and tissue. Surface properties can be selectively modified to enhance the performance of the biomaterials. For instance, by blending PLA matrix with PCL, PHB or PEG, optimal surface, chemical, and physical properties promoting cell viability were attaine
Reduced graphene oxide/iron nanoparticles used for the removal of Pb (II) by one step green synthesis
No full textWhile nanomaterials are increasingly being proposed for contaminant remediation, a major challenge is how to develop high removal functionality while maintaining low cost and environmental friendliness. In this study, a hybrid reduced graphene oxide/iron nanoparticle (rGO/Fe NPs) was prepared via the in situ reduction of GO and FeCl3 by eucalyptus leaf extract in one-pot. The obtained rGO/Fe NPs could rapidly remove 72.7% of Pb(II) from aqueous solution in 10 mins and remove up to the maximum removal efficiency of 82.4%. Electron microscopy, XPS and BET showed that the irregular Fe3O4 nanoparticles, sized between 20 and 40 nm, were disorderly dispersed on rGO sheets, which constituted a mesoporous material. FTIR and XRD indicated that the surface of rGO/Fe NPs was capped by many active organic constituents from the eucalyptus leaf extract. rGO/Fe NPs also showed a high selectivity for Pb(II) with minimal interference from either calcium or magnesium ions in the solution. Finally, GC–MS separated 13 significant active organic constituents from the eucalyptus leaf extract that possibly contributed to the reduction of rGO/Fe NPs. Overall, eucalyptus leaf extracts, acted efficiently as green reducing agents and impacted reactivity of the final material by determining the components and surface properties of rGO/Fe NPs
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