1,721,004 research outputs found
Biological performance of a novel biodegradable polyamidoamine hydrogel as a guide for peripheral nerve regeneration
No full textTissue engineering is a rapidly evolving discipline that seeks to repair, replace, or regenerate specific tissues or organs by translating fundamental knowledge in physics, chemistry and biology into practical and effective materials, devices, systems, and clinical strategies. Different polymeric biomaterials have been proposed as scaffold for tissue engineering applications. In recent years, special attention has been given to hydrogels. Hydrogels are insoluble and swellable materials that are widely used in the biomaterial field due to their biocompatibility, which derives from their high water absorption and surface properties.
Several Agma1-based hydrogels obtained using ethylenediamine as cross-linker have been previously studied as scaffold for tissue engineering applications. They exhibited good results in term of biocompatibility and adhesion properties toward different cell lines. Unfortunately, their mechanical properties were not satisfactory in that their strength was still very low and they were very soft and breakable on handling. To overcome these problem, in this work a new synthetic method has been developed leading to hydrogels with similar composition and exhibiting the same biological properties but with improved mechanical strength . In particular a different two-step pathway has been followed.
In the first step an acryloyl end-capped linear AGMA1 oligomer was synthesised using a controlled excess of the selected bisacrylamide; in the second step the oligomer was photopolymerized by UV irradiation producing hydrogels with the required mechanical properties. Using this new synthetic procedure, Agma1-UV made hydrogels with different form and shape were prepared. In particular, tubular scaffolds with 1 mm inner diameter were tested in vivo as conduit for nerve regeneration in a rat sciatic nerve cut model. The implant were analyzed at 30, 90 and 180 days post-surgery and resulted particularly promising in many important respects, such as biodegradability, biocompatibility, lack of inflammatory reaction upon degradation and capability of promoting optimum morphological and functional nerve regeneration. The regenerated nerves showed several interesting signs of morphological improvements even at 30 days post-surgery. At 180 day the scaffold was almost completely reabsorbed and the regenerated nerve morphologically comparable to the control animals
Biological performance of a novel biodegradable polyamidoamine hydrogel as guide for pheripheral nerve regeneration
No full textIn this work a library of PAA hydrogels were prepared by conventional polyaddition of different bis-acrylamides and bis-amines using different amounts of 1,2-diaminoethane as cross-linking agent. These hydrogels were obtained in different shapes and dimensions and were characterized in terms of swelling degree in aqueous media at different pHs, degradation kinetics and rheological properties according to the shear stress mode analysis. The hydrogel cyto-biocompatibility and ability to induce adhesion and proliferation of Schwann cells, playing a fundamental role in peripheral nerve growth was also assessed. The results obtained pointed to the conclusion that all hydrogels were biocompatible and fully degradable at physiological pH, with a degradation rate depending on the cross-linking degree. They also exhibited mechanical properties much depending on the cross-linking degree
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
The use of novel PLGA-g-PVP amphiphilic copolymers for fabrication of nanostructured materials
No full textThe aim of this work is to present a one-pot synthetic process leading to poly(lactide-co-glycolide)-g-poly(vinylpyrrolidone) (PLGA-g-PVP)copolymers consisting of high molecular weight PLGA carryingoligomericPVPside chains.
The title copolymers were prepared by chain transfer radical polymerization of N-vinylpyrrolidone in the presence of 50:50 PLGA, acting as polymeric chain transfer agent in the absence of solvents.
All copolymers were characterized by1H-NMR (400 MHz), FT-IR, SEC, MALDI-TOF, DSC, TGAand DLS techniques.
PLGA is a lipophilic biodegradable polymer, whereas PVP is hydrophilic, biocompatible and also bioeliminablefor molecular weights< 40.000.1,2Both polymers have beenapproved for human use by the U.S. Food and Drug Administration, therefore thePLGA-g-PVPcopolymers are eligible for medical applications.The water-soluble PVPportionimpartsamphiphilicity tothe otherwise hydrophobic PLGA, thus modifying its behavior in aqueous systems. In particular, PLGA-g-PVP samples spontaneously form nanoparticles when dispersed in water. These nanoparticles, besides dissolving hydrophobic drugs,for instance antimalarial drugs, in the inner core, are expected to show higher compatibility than native PLGA towards many drugsknown
Materiali polimerici innovativi e biocompatibili per l’assorbimento di contaminanti organici alogenati dalle acque
No full textLa contaminazione delle risorse idriche come fiumi, laghi, oceani e falde acquifere è uno dei problemi ambientali più gravi e di urgente risoluzione. Gli inquinanti sono sia specie inorganiche, come ioni di metalli pesanti, sia specie organiche. I metodi finora usati per rimuoverli risultano spesso costosi o poco efficaci; si cercano perciò metodi sostitutivi più efficaci e/o economici, basati ad esempio sul recupero di materiali di scarto o su materiali polimerici sintetizzabili a basso costo, con processi a rese elevate e a basso o nullo impatto ambientale.
Un esempio è costituito dalla promettente famiglia delle poliammidoammine (PAA), polimeri biocompatibili e di struttura modulabile con estrema facilità e flessibilità in funzione dell’applicazione, che da alcuni anni stiamo sviluppando e caratterizzando dal punto di vista delle proprietà chimico fisiche per applicazioni in campo biologico e farmaceutico (carrier di farmaci a rilascio controllabile con pH, scaffold polimerici per la coltivazione dei tessuti) e ambientale (per la rilevazione e/o la rimozione di inquinanti dalle acque). Esse presentano gruppi amminici e ammidici ai quali possono essere aggiunti altri gruppi funzionali a seconda dell’applicazione desiderata, e possono essere di tipo lineare, ramificato oppure sotto forma di resine. Si ottengono mediante poliaddizione di Michael di ammine primarie alifatiche o diammine secondarie a bisacrilammidi; tale sintesi è a basso costo, a basso impatto ambientale e procede in solventi environmental friendly come l’acqua, senza l’uso di catalizzatori.
Nel caso innovativo che presenteremo abbiamo pensato di funzionalizzare tali resine con cavità ciclodestriniche, potenzialmente in grado di assorbire molti inquinanti organici, rilasciandoli poi ad esempio mediante trattamento termico. Come molecole modello per verificare le prestazioni di questi nuovi materiali abbiamo scelto quattro molecole organiche clorurate di diversa struttura (arilica, alchilica, benzilica): CHCl3, CF3CClBrH (alotano, un anestetico), ClACN, FCH2Cl. Inizialmente abbiamo studiato l’interazione di queste molecole con le ciclodestrine α e β tal quali, passando successivamente alla caratterizzazione delle resine con esse funzionalizzate, partendo per ragioni economiche da resine β ciclodestriniche (sia omo- sia copolimeri). Le cinetiche di assorbimento sono state ottenute monitorando in diretta e in situ la concentrazione dell’alogeno mediante tecniche voltammetriche (CV e SWV), utilizzando come elettrodo di lavoro Ag, di cui il nostro gruppo studia da anni le proprietà catalitiche per la riduzione degli alogenuri organici. Abbiamo verificato che la α-ciclodestrina è la più indicata per assorbire composti organici clorurati di piccole dimensioni come CHCl3 e ClACN, mentre FCH2Cl, col suo anello aromatico, è assorbito esclusivamente dalla β. Le resine funzionalizzate con le ciclodestrine hanno dimostrato di non solo conservare, ma in molti casi migliorare la capacità assorbente della ciclodestrina originaria, con interessanti tempi di dimezzamento dell’inquinante
The use of novel PLGA-g-PVP amphiphilic copolymers for fabrication of nanostructured materials
No full textThe aim of this work is to present a one-pot synthetic process leading to poly(lactide-co-glycolide)-g-poly(vinylpyrrolidone) (PLGA-g-PVP)copolymers consisting of high molecular weight PLGA carryingoligomericPVPside chains.
The title copolymers were prepared by chain transfer radical polymerization of N-vinylpyrrolidone in the presence of 50:50 PLGA, acting as polymeric chain transfer agent in the absence of solvents.
All copolymers were characterized by1H-NMR (400 MHz), FT-IR, SEC, MALDI-TOF, DSC, TGAand DLS techniques.
PLGA is a lipophilic biodegradable polymer, whereas PVP is hydrophilic, biocompatible and also bioeliminablefor molecular weights< 40.000.1,2Both polymers have beenapproved for human use by the U.S. Food and Drug Administration, therefore thePLGA-g-PVPcopolymers are eligible for medical applications.The water-soluble PVPportionimpartsamphiphilicity tothe otherwise hydrophobic PLGA, thus modifying its behavior in aqueous systems. In particular, PLGA-g-PVP samples spontaneously form nanoparticles when dispersed in water. These nanoparticles, besides dissolving hydrophobic drugs,for instance antimalarial drugs, in the inner core, are expected to show higher compatibility than native PLGA towards many drugsknown to interact with PVP.In addition, PLGA-g-PVP samples,whenused as additives,dramatically improved wettability of hydrophobic materials, as forinstance polyesters, processed asnanofibers andintended forapplications involvingcontact with the body fluids
Acid-Base Properties of Poly(amidoamine)s
No full textPolyamidoamines (PAAs) represent a family of degradable polymers carrying
ter-amine groups in the polymer backbone, which behave as polyelectrolytes in
aqueous solutions. Many relevant properties of PAAs, including the ability to interact
with components of the biological environments, such as nucleic acids, proteins, and
living cells, are strongly dependent on their acid-base properties, hence on their ionization
state in different biological districts. In this article, the protonation constants
of a series of PAAs have been precisely determined by electrochemical techniques in
order to build up a homogeneous library containing both the protonation constants
and the average distribution of the charged species, hence the net average charge as
a function of pH. Moreover, correlations between chemical and cytotoxicity, have
been attempted
- …
