1,720,963 research outputs found
Exploring digital light processing 3D printing to produce villi-crypt scaffold-on-chip mimicking the intestinal epithelium
No full textIn vitro models are crucial for studying the intricate interplay between the intestinal epithelium and microbiota in a controlled
environment. This work focuses on developing a 3D in vitro model using DLP-3D printing to mimic the complex intestinal
crypt-villi system within a perfusion microfluidic device.
A blend of home-produced gelatin methacrylate (GelMA) and low molecular weight polyethylene glycol diacrylate (PEGDA),
dissolved in DMEM, was employed. The production parameters such as GelMA methacrylation, pre-hydrogel solution
composition (polymers, photoinitiatior and photoabsorber concentrations), layer thickness and exposure time, and power
intensity were optimized. Different formulations were analyzed for mechanical properties using a rheometer, to find the
optimal balance between stiffness mimicry and printing fidelity, and were evaluated for cytocompatibility using Caco-2 cells.
The desired architectures were achieved, having parabolic villi (433 ± 15 μm height; 320 ± 20 μm base), and cylindrical crypts
(141 ± 6 μm height; 134 ± 10 μm diameter). GelMA with high degree of substitution was successfully produced, achieving
high printing fidelity, long-term stability and cytocompatibility. The chosen GelMA/PEGDA compositions 9.0/4.5 (w%/w%)
and 4.5/4.5 (w%/w%) displayed a shear elastic modulus of 21.9 ± 1.3 kPa and 7.0 ± 0.4 kPa, respectively. The closed devices
were finally produced with compliant squared channels of 500 μm side, and their perfusability was assessed over a 0 – 100
μL/min range of flow rates. Both the compositions revealed good cell attachment and metabolic activity of Caco2 cells. At 24
hours, the Resazurin reduction assay revealed consistent metabolic activity across the two compositions, whether in their
original form or when coated with gelatin.
Overall, we successfully developed a closed microfluidic device, comprising the desired internal villi-crypt like morphology,
with tunable mechanical properties and able to sustain the attachment and growth of the Caco-2 cell line
Piezoelectric Yield of Single Electrospun Poly(acrylonitrile) Ultrafine Fibers Studied by Piezoresponse Force Microscopy and Numerical Simulations
Full text linkQuantitative converse piezoelectric coefficient (d33) mapping of polymer ultrafine fibers of poly(acrylonitrile) (PAN), as well as of poly(vinylidene fluoride) (PVDF) as a reference material, obtained by rotating electrospinning, was carried out by piezoresponse force microscopy in the constant-excitation frequency-modulation mode (CE-FM-PFM). PFM mapping of single fibers reveals their piezoelectric activity and provides information on its distribution along the fiber length. Uniform behavior is typically observed on a length scale of a few micrometers. In some cases, variations with sinusoidal dependence along the fiber are reported, compatibly with a possible twisting around the fiber axis. The observed features of the piezoelectric yield have motivated numerical simulations of the surface displacement in a piezoelectric ultrafine fiber concerned by the electric field generated by biasing of the PFM probe. Uniform alignment of the piezoelectric axis along the fiber would comply with the uniform but strongly variable values observed, and sinusoidal variations were occasionally found on the fibers laying on the conductive substrate. Furthermore, in the latter case, numerical simulations show that the piezoelectric tensor’s shear terms should be carefully considered in estimations since they may provide a remarkably different contribution to the overall deformation profile
Innovative Approaches to Target the Intestinal Epithelium: Gellan Gum Microparticles for Probiotic Delivery and Development of 3D In Vitro Models
No full textIl progetto di dottorato si è concentrato su tre tematiche di ricerca nell’ambito di approcci innovativi per il targeting intestinale: lo sviluppo di un sistema di microincapsulamento di probiotici, da impiegare nella formulazione di nuovi alimenti funzionali, e lo studio di due modelli in vitro del tratto intestinale, finalizzati a fornire nuove tecnologie per lo studio dell’epitelio intestinale e delle sue interazioni con probiotici, nutraceutici e farmaci.
La prima parte ha riguardato lo sviluppo di un sistema di microincapsulamento di probiotici mediante microdripping elettroidrodinamico di soluzioni a base di gomma di gellano. È stato utilizzato Lactobacillus fermentum come probiotico modello per ottimizzare le condizioni di incapsulamento ed analizzarne l’efficienza, oltre alla vitalità e l’attività metabolica dei probiotici incapsulati. Le cellule incapsulate hanno mantenuto un’elevata vitalità e funzionalità metabolica, dimostrando anche un’attività antimicrobica diretta contro Escherichia coli e la capacità di stimolare la produzione di beta-defensina umana 2 nella linea cellulare intestinale Caco-2, in modo paragonabile alle cellule non incapsulate.
La seconda parte del lavoro ha previsto lo studio di un modello in vitro 3D del tratto intestinale, coltivando cellule della linea Caco-2 su scaffold tubolari realizzati tramite elettrofilatura, composti da policaprolattone e poliacrilonitrile. Tali scaffold hanno riprodotto le caratteristiche strutturali e meccaniche del lume intestinale. In particolare, gli scaffold in PAN hanno offerto prestazioni superiori grazie alla maggiore porosità, resistenza meccanica e piezoelettricità. Sono stati inoltre sviluppati un sistema di semina per garantire una distribuzione cellulare omogenea e un bioreattore per applicare uno stress meccanico alle cellule cresciute sugli scaffold. I saggi biologici hanno confermato una buona adesione, crescita e vitalità cellulare.
La terza linea di ricerca ha riguardato lo sviluppo di uno scaffold-on-chip, utilizzando idrogeli come GelMA e PEGDA per replicare l’architettura complessa delle cripte e dei villi intestinali all’interno di un dispositivo microfluidico. I parametri di stampa sono stati ottimizzati al fine di produrre scaffold citocompatibili con proprietà meccaniche modulabili. Le cellule della linea Caco-2 hanno mostrato buona adesione, elevata attività metabolica e la formazione di uno strato epiteliale differenziato che segue la topografia dello scaffold come confermato da analisi molecolari e proteiche. Il dispositivo permette inoltre una perfusione continua, per futuri studi in regimi dinamici.
Nel complesso, il progetto ha fornito nuovi strumenti per la somministrazione di probiotici e piattaforme in vitro avanzate per lo studio dell’epitelio intestinale.The doctoral project focused on three research topics in the framework of novel approaches for intestine targeting: the development of a microencapsulation system for probiotics to be used in the formulation of new functional foods, and the study of two in vitro models of the intestinal tract, aimed at providing new technologies for investigating the intestinal epithelium and its interactions with probiotics (both encapsulated and non-encapsulated), nutraceuticals, and drugs.
The first focused on developing a microencapsulation system for probiotics using
electrohydrodynamic microdripping of gellan gum solutions. Lactobacillus fermentum was used as a model probiotic to optimize encapsulation conditions, assess particle formation, and evaluate encapsulation efficiency, probiotic viability, and metabolic activity. The encapsulated cells retained high viability and metabolic function and were shown to exert direct antimicrobial activity against Escherichia coli and stimulate the production of human beta defensin 2 on the Caco-2 intestinal cell line in a comparable manner to unencapsulated cells.
The second part involved creating an in vitro 3D model of the intestinal tract by growing Caco-2 cells on electrospun tubular scaffolds made of polycaprolactone and polyacrylonitrile. These materials mimicked the structural and mechanical features of the intestinal lumen. PAN scaffolds, in particular, offered better performance due to their higher porosity, mechanical strength, and piezoelectric properties. A custom seeding system was developed to enable uniform cell distribution, and a bioreactor was designed and tested to apply mechanical stress to the cultured cells. Biological assays confirmed good cell adhesion, growth, and viability.
The third research focus was the creation of a 3D-printed scaffold-on-chip device, using
hydrogels such as gelatin methacryloyl (GelMA) and poly(ethylene glycol) diacrylate
(PEGDA), to replicate the complex architecture of intestinal crypts and villi within a
microfluidic device. Parameters like polymer concentration, light exposure, and printing
fidelity were optimized to produce cytocompatible scaffolds with tunable mechanical
properties. Caco-2 cells adhered well, showed high metabolic activity, and formed a
differentiated epithelial layer aligned with the scaffold’s topography, as confirmed by
molecular and protein analyses. The device also sustained a continuous perfusion at different flow rates, which will be exploited for future studies in dynamic conditions.
Overall, the project provided new tools for probiotic delivery and advanced in vitro platforms for studying gut epithelium interactions with probiotics, nutraceuticals, and pharmaceuticals
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Electrospun biomimetic scaffold for eardrum regeneration.
No full textTympanic membrane (TM) perforations represent a widespread clinical problem, with different surgical procedures involved for the treatments of chronic perforations. Graft materials and scaffolds are used as patches but, at present time, none of them include the reproduction of the unique arrangement of the eardrum collagen fibres, consisting of a radial layer and a circular one. The aim of this work is to design and produce a scaffold able to reproduce, at a sub-micrometric scale, this fibrous arrangement. The desired structures were reached via electrospinning of Poly(ethylene oxide terephthalate)-co-poly(butylene terephthalate) multi-block copolymer solution on a new type of collector, developed for our necessities with the aid of finite element analysis of the electric field. The main anatomical features of the human eardrum, such as shape, size and thickness, were achieved in the produced scaffolds. The radial fibre layer was accurately reproduced and the effect of the main processing parameters on the fibre diameters and arrangement were studied. Regarding the circular layer, a partial alignment was obtained and some strategies to improve the deposition precision were identified, which will be tested in the next future. The results of this study pave the way to design a final version of the collector, able to produce both layers in the scaffold in a precise and scalable manner
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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