99 research outputs found
Enhanced Embedding of Cations into Titanium Surfaces by AC Plasma Electrolytic Oxidation for Osteointegrated Implants
No full textTitanium and its alloys represent the gold standard for osteointegrated implants, but their characteristic bioinertness still hinders their optimal integration within the host tissues. This limitation can be overcome by introducing osteoinductive functionalities on their surface. Plasma electrolytic oxidation (PEO) has emerged as a cost-effective and rapid electrochemical method for generating bioactive titanium dioxide (TiO2) coatings, but the incorporation of pro-osteogenic cations with this technique is typically passive and, in turn, characterized by a low efficiency. Here, alternate current (AC) PEO is investigated as a flexible solution to incorporate zinc into TiO2 coatings by exploiting the active transport of cations during the cathodic phase of the process. The resulting microporous surfaces show a greater zinc incorporation and an increased presence of rutile domains compared to conventional direct current (DC) PEO coatings, without, however, yielding significant morphological differences. In vitro assays with human mesenchymal stem cells (hMSCs) reveal an increased metabolic activity of cells adhering onto AC PEO surfaces. In addition, the increased expression of osteogenic differentiation markers (RUNX2 and osteocalcin) indicates significant surface-driven osteoinductive effects, particularly for coatings grown by applying a short cathodic spike. Taken together, these aspects make Zn-doped AC PEO surfaces a promising solution for osteoinductive orthopedic and dental applications
Compounded topographical and physicochemical cueing by micro-engineered chitosan substrates on rat dorsal root ganglion neurons and human mesenchymal stem cells
No full textGiven the intertwined physicochemical effects exerted in vivo by both natural and synthetic (e.g., biomaterial) interfaces on adhering cells, the evaluation of structure-function relationships governing cellular response to micro-engineered surfaces for applications in neuronal tissue engineering requires the use of in vitro testing platforms which consist of a clinically translatable material with tunable physiochemical properties. In this work, we micro-engineered chitosan substrates with arrays of parallel channels with variable width (20 and 60 mu m). A citric acid (CA)-based crosslinking approach was used to provide an additional level of synergistic cueing on adhering cells by regulating the chitosan substrate's stiffness. Morphological and physicochemical characterization was conducted to unveil the structure-function relationships which govern the activity of rat dorsal root ganglion neurons (DRGs) and human mesenchymal stem cells (hMSCs), ultimately singling out the key role of microtopography, roughness and substrate's stiffness. While substrate's stiffness predominantly affected hMSC spreading, the modulation of the channels' design affected the neuronal architecture's complexity and guided the morphological transition of hMSCs. Finally, the combined analysis of tubulin expression and cell morphology allowed us to cast new light on the predominant role of the microtopography over substrate's stiffness in the process of hMSCs neurogenic differentiation
Physicochemical and nanomechanical investigation of electrodeposited chitosan:PEO blends
No full textCathodic electrodeposition is a bottom up process that is emerging as a simple yet efficient strategy to engineer thin polymeric films with well-defined physicochemical properties. In particular, this technique offers the distinctive advantage of an easy control over composition, thickness, and morphology of the films by simply adjusting treatment parameters. In this work, cathodic electrodeposition was exploited to engender blends composed by chitosan (CH) and poly-ethylene-oxide (PEO) with different weight ratios. The physicochemical and nanomechanical properties of the resulting films were successively characterized by integrating Raman and Fourier-transform infrared (FT-IR) spectroscopy with Atomic Force Microscopy (AFM). Our findings demonstrate that electro-deposition is an effective technique for the co-deposition of CH:PEO blends. Moreover, spectroscopic and AFM analyses correlated the physicochemical (i.e. structural organization, bond formation and cross-linking) and nanomechanical properties of the blends to the PEO content, ultimately unveiling the molecular interactions and mechanisms involved in the cathodic deposition of CH:PEO film
Particle anisotropy and crystalline phase transition in one-pot synthesis of nano-zirconia: A causal relationship
No full textCrystalline phase evolution and morphological changes are strictly correlated phenomena during the growth of zirconia nanoparticles. In this work, the effects of synthetic variables, reaction time (up to 24 hours) and precursor concentration (0.16 and 0.5 M), of a one-step non-hydrolytic sol-gel route to zirconia are investigated. Zirconium tetrachloride (ZrCl4) is chosen as a zirconium oxide precursor to react in benzyl alcohol. At a low precursor concentration and a short reaction time, pseudo-spherical particles of size 2 nm with a narrow size distribution are observed by transmission electron microscopy (TEM). At this stage, mainly the tetragonal phase is detected. By increasing both the zirconium precursor concentration and reaction time, a broadening of size distribution is observed resulting from the growth of anisotropic particles. Concurrently, an increasing amount of the monoclinic is detected by X-ray diffraction and Raman spectroscopy. As a novelty, Rietveld investigations on electron diffraction ring patterns obtained by transmission electron microscopy are performed. This procedure allows the collection of comprehensive information about nanostructured particles in one-step analysis. The results derived from this analysis, together with the high resolution transmission electron microscopy (HR-TEM) data, consistently support the structural transition from pseudo-spherical tetragonal particles to rice-shaped monoclinic particles
Synthesis and characterization of scratch-resistant hybrid coatings based on non-hydrolytic sol-gel ZrO2 nanoparticles
No full textHybrid transparent coatings based on zirconia nanoparticle fillers and epoxy resin were designed to increase scratch resistance of commodity polymers without impairing their optical properties. Suspensions of nano-crystalline ZrO2 in benzyl alcohol were synthesized via a versatile non-hydrolytic sol-gel process using ZrCl4 as precursor. The obtained ZrO2 nanoparticles showed a crystalline structure attributable to a tetragonal phase and an average particle size of 2 nm. ZrO2 nanoparticles, suspended in tert-butanol, were mixed with a commercial epoxy resin (5 and 10%wt.). The organic solvent was then evaporated and hybrid composites were deposited on polycarbonate and poly(methyl methacrylate). The obtained coatings showed a homogeneous adhesion and a negligible effect on the transparency of these polymers. An increased scratch-resistance was obtained by increasing the ZrO2 nanoparticles content. (C) 2016 Elsevier B.V. All rights reserved
Modelling and Optimization of Batch Manufacturing Systems under Environmental and Economic Considerations
No full textNowadays, minimization of the negative environmental impact of manufacturing processes is considered one of the most challenging problems in various industrial fields. Research communities and environmental legislators are continuously working to address these problems by placing significant efforts in devising new strategies to increase environmental sustainability. One of these problems is the lack of a comprehensive framework that can simultaneously improve economic aspects and lessen the impact on the environment. The need for a mathematical model that can assist firms in reaching suitable investment decisions has become of paramount importance. In this context, this study aims at optimizing the environmental and economic sustainability of batch production systems (i.e. a series of workstations where products are manufactured in batches). To this end, a profit maximization model was created by incorporating constraints such as budget, demand, greenhouse gas emissions and hazardous wastes within the manufacturing stage of product life cycle. Moreover, the model provides detailed guidelines on required improvements in a specific manufacturing system and calculates the investment associated with such implementations. This new approach was tested by using two different software packages and results were probed and discussed in different scenarios to investigate its validity. Sensitivity analysis and simulation results proved the consistency of the proposed mathematical model. In particular, in order to further assess the validity of the model, a pharmaceutical plant was selected as a case study, which also permitted discussion on additional aspects of the problem
Development and characterization of phase-separated PS/PMMA nanostructured substrates for cellular adhesion
No full textCellular Response to Semi-ordered and Biomimetic Nanotubular Surfaces
No full textUnderstanding cell behavior at the material-host tissue interface is a fundamental prerequisite for designing the next generation of biomaterials capable of directing cellular events towards a desired biological outcome (e.g. faster tissue integration). In addition, unraveling the relationship between cell activity and nanoscale surface features will further the present knowledge of the fundamental cellular mechanisms that control how cells sense and respond to natural (e.g. extracellular matrix) and synthetic (e.g. biomaterials) surfaces. It is now well-known that the nanoscale physicochemical features of surfaces dictate cell fate by affecting phenomena such as proliferation, differentiation, genetic transcription and protein translation. In particular, nanotopographical features play a pivotal role during cell-surface interactions by exerting a direct mechanotransductive effect on cells, which, in turn, dictate biochemical signaling. In this context, several studies have addressed different aspects of the relationships between nanofeatures and specific cellular functions, including morphological changes, the establishment of focal adhesions (FAs, clusters of adhesion molecules that regulate cell structure and activity, determining how cells sense and respond to natural and synthetic substrates) and differentiation. However, the precise interplay between the morphological characteristics of nontopographical features not only on the surface but also along a third dimension (height) and cellular response still needs to be fully elucidated. Once revealed, such knowledge will shed new light on how cells sense and respond to 2- and 3-dimensional nanoscale patterns. In this context, anodization, a simple yet effective electrochemical treatment, allows to engender on titanium, the gold standard in medicine, arrays of nanotubes with tailor-made diameters. Notably, although nanotubular surfaces on anodized titanium have been extensively studied in relation to their effect on cell response, none of the previous studies has precisely assessed the effects of the morphological features and geometrical
arrangement of the nanotubes. This is an important aspect, since the morphological characteristics and the spatial placement of nanofeatures has been shown to control cell response. In addition, by employing the same technique (i.e. anodization), a 3-dimensional hierarchical surface that mimics the frustule (i.e. silicified cell wall) of diatoms (a type of microalgae) can be created. Aside from enabling, for the first time, cellular studies on such bioinspired surface, this hierarchical nanoscale substrate will also allow to probe the effects of a 2-tier nanotopographical gradient along the depth of the nanotubular layer
Investigation of the Human MG63 Osteoblastic Cell Response to Nanotubular Surfaces
No full textCells found within bone tissues, and in particular osteoblasts, are profoundly influenced by the nanotopographical features of their extracellular environment which play a critical role in orchestrating osteogenesis, cellular differentiation, and bone mineralization, via a wide range of mechanical and biochemical signals. Advances in materials science and nanotechnology have made possible to create substrates and interfaces with intricate nano-patterns that interact with cells at the molecular level, offering unprecedented opportunities to investigate the mechanisms that control cellular interactions with both natural and synthetic surfaces. The development of micro-and nano-engineered surfaces has been one of the main factors that has spurred the advances in bone tissue engineering. However, the development of more effective surfaces capable of predictively dictate a beneficial cellular response also requires a deep understanding of how to account for the complex and variable conditions of the native bone microenvironment. In this Thesis, nanotopographical and environmental variables were incorporated by investigating the role of cellular preconditioning in elevated glucose levels and the ability of optimized, single diameter titanium nanotubular surfaces to modify the preconditioned behavior via direct physicochemical cueing. In further pursuit of optimal parameters, the integration of high-throughput screening processes for evaluating these surfaces has aroused interest for the rapid identification of nanotopographical features that best support osteogenesis. Multivariable testing via nanotopographical gradients can help address this need, accelerating the development of effective surfaces and enhance our ability to rapidly tailor surface properties to specific real-world applications. As the field advances, the design and implementation of nanotopographical surfaces that can effectively direct osteoblast behavior will be pivotal in creating next-generation biomaterials. The future of bone tissue engineering lies in the ability to create specialized surface designs with a nuanced understanding of cellular dynamics to achieve superior outcomes in bone health and regeneration.
The overarching goal of my doctoral work was to engineer nanotopographical surfaces with tailored structural complexities to elicit specific osteoblastic responses. This approach aims to optimize surface properties for enhanced bone tissue engineering applications, including promoting osteogenic differentiation, reducing experimental variability from both environmental and surface features, and creating high-throughput platforms for rapid biomaterial screening.
In the first study (Chapter 2), I investigated the combined influence of nanotopographical cues and environmental factors on human MG63 osteoblastic cell behavior. Using a triphasic anodization protocol, I created highly ordered single nanotube surfaces with varying tube diameters and compared these with a complex honeycomb architecture. I also modulated the glucose content in the culture medium to simulate normal and hyperglycemic conditions, incorporating a preconditioning step to ensure cells adapted to the altered environment. I then systematically analyzed cellular responses, including proliferation, migration, viability, and differentiation, under these different conditions to uncover potential synergistic or antagonistic effects between the nanotopographical features and environmental factors.
In the second study (Chapter 3), I explored the influence of hierarchical nanotubular gradients on cell response, focusing on the complexity of the two-tiered, honeycomb architecture. I used a bipolar anodization process to create these surfaces, which featured a gradient of increasing disorder end-to-end, transitioning from single tubes into complex honeycomb topography. The study assessed the impact of these nanotopographical variations on cellular responses, including proliferation, differentiation, and migration. My findings highlighted the significant role of nanotopographical complexity, particularly in promoting osteogenic differentiation. I developed a high throughput testing process, aimed at shortening the time required to troubleshoot and optimize cell response, culminating in the extraction and synthesis of the most and least favorable surfaces, for further testing and validation of this process.
In the third study (Chapter 4), I investigated MG63 osteoblastic cell behavior on rationally selected titanium nanotubular surfaces that were extracted from the previously developed gradient anodization process. These surfaces validated the high-throughput approach by confirming cell responses across the two topographies and provided deeper insights into the interactions between cells and surfaces of different complexities. Lastly, I established a Raman confocal imaging protocol on opaque, light-sensitive titanium, identifying key biochemical features of single cells and bone-like mineral for future research, demonstrating the feasibility of this technique for further study
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