1,721,233 research outputs found
Polyoxazoline biointerfaces by surface grafting
No full textFunctionalization of biomaterials by "grafting-to" of functional polymers represents a pivotal strategy to hinder unspecific biological adhesion, provide functions to the modified biomaterials and modulate their interfacial, physico-chemical properties. The increasing interest for poly-2-alkyl-2-oxazolines (PAOXAs) as starting material for the fabrication of biomedical devices has progressively triggered the attention of chemists and materials scientists seeking possible substitutes to poly(ethylene glycol)s (PEGs) for surface functionalization. The chemical versatility of PAOXAs coupled to their stability and outstanding bioinertness when immobilized on surfaces have allowed the fabrication of coatings that efficiently prevent the contamination by proteins and bacteria. In this review, a comprehensive summary of the surface modification methods involving the grafting of PAOXA species is provided. We especially concentrate on how the chemical tailoring of PAOXAs can be exploited to synthesize surface modifiers for the robust functionalization of different inorganic and organic materials. Additionally, a special focus is given to the performance of PAOXA coatings as biointerfaces and their comparison with PEG-based analogues. As the research efforts in finding suitable alternatives to PEGs are increasingly stimulated, among the possible solutions for meeting this demanding need PAOXAs represent one of the most promising. (C) 2016 Elsevier Ltd. All rights reserved
It's all about topology: The evolution of polymer brushes and their performance
No full textThe application of distinctive polymer topologies, beyond the simple linear chain, to yield cyclic and loopsforming
surface-grafted assemblies, enables a broad modulation of highly relevant, interfacial physico-chemical
properties. This is especially valid on flat surfaces, where the ultra-dense and highly compact character of cyclic
polymer “brushes” provide an enhanced steric stabilization of the interface and a superlubricious behavior.
Alternatively, when cyclic brushes form shells on inorganic nanoparticles (NPs), their extraordinary structural
properties make them impenetrable and long-lasting shields, which extend the stability of NP dispersions and hinder
any interaction with serum proteins.
Polymer topological effects, typically observed in bulk or in solution are amplified by adding an additional boundary
such as a grafting surface. Their precise tuning translates into materials with unprecedented properties and extremely
high applicability
Restoring the lubrication properties of degenerated cartilage with tissue-reactive graft-copolymers
No full textLubrication within articular joints is mediated by macromolecular complexes of glycoproteins and polysaccharides,
which act as boundary lubricants at the cartilage surface, providing very low coefficients of friction and ensuring no
wear over decades. The progressive depletion of these macromolecules, accompanied by extracellular matrix (ECM)
degradation, are phenomena associated with the occurrence of degenerative diseases of the joint, such as
osteoarthritis (OA). Due to the non-vascularized nature of cartilage and the consequent inhibition of self-healing
processes, OA progression results irreversible and a need for treatments to restore its original lubrication properties is
increasingly urged.
Inspired by the structure and properties of natural biolubricants, we developed an injectable, fully synthetic formulation
for both protecting the degraded tissue and restoring its lubrication properties. This relies on brush-forming graftcopolymers
featuring a tissue reactive, aldehyde-bearing polyglutamic acid (PGA) backbone, and poly-2-methyl-2-
oxazoline (PMOXA) side grafts. The designed graft-copolymers can readily bind on the degenerated cartilage tissue
through Schiff-base formation and generate a bioinert and highly lubricious polymer brush layer. A systematic tuning
of the molar mass, density and chain-topology of the PMOXA grafts allow to reproduce the low coefficient of friction
characteristic of the healthy cartilage, protect the degraded tissue from protein contamination and prevent further
damage. All these attractive properties, combined with their high biocompatibility, make these graft-copolymers
promising candidates for the development of treatments to halt or slow down cartilage degeneration
Tissue-reactive polymethyloxazoline-based graft-copolymers as promising biolubricants for articular cartilage
No full textOsteoarthritis is a chronic and degenerative condition that results in a structural and functional failure of synovial joints. In particular, a loss in the glycosaminoglycan (GAG) content takes place, together with a consequent reduction of wear-resistance in the cartilage tissue. To develop a treatment that could restore the lubrication properties of an injured joint, we took inspiration from the natural components of the synovial fluid. Among these, hyaluronic acid and glycoproteins, such as lubricin, were shown to play a major role. The latter shows a central brush-like region extensively modified by O-linked oligosaccharide side chains. Furthermore, it binds to the cartilage surface and protects it from adsorption of proteins and cells.
In orded to mimic the structure and activity of lubricin we developed new biomimetic graft-copolymers featuring a biodegradable polyglutamic acid (PGA) backbone with poly-2-(methyl-2-oxazoline) (PMOXA) and aldehyde-bearing side chains. In particular, PMOXA forms a biopassive and lubricating brush film at the interface. In addition, the aldehyde functions react with aminolized, degenerated cartilage tissues via Schiff-base formation.
A series of PGA-α-PMOXAx-β-aldehyde copolymers with different side-chain lengths (x) and PMOXA(α)/aldehyde(β) grafting densities were successfully synthesized and adsorbed on bovine cartilage tissues (Figure).
Depending on the adsorption conditions and on the graft-copolymer architecture enhanced antifouling properties resulted for the films featuring higher surface density of MOXA units. In addition, very low coefficients of friction were observed for the coatings with increased mass of copolymer for surface unit. The combination of selective anchoring to aminolized surfaces with high lubricating properties, biocompatibility and protein resistance makes PGA-α-PMOXAx-β-aldehyde graft-copolymers promising biolubricants for cartilage tissues
O Nascimento da Neuropsiquiatria infantil na Itália
No full textIl contributo si propone di presentare i fattori storico-culturali e scientifici che hanno portato alla nascita della Neuropsichiatria infantile in Italia. Nel capitolo si pone particolare attenzione al lavoro dello psicologo e psichiatra Sante de Sanctis al quale si riconosce un ruolo di primo piano nella costruzione della diagnosi di autismo
Sante de Sanctis e o nascimento da psicologia jurídica na Itália
No full textIl contributo presenta lo sviluppo della Psicologia giuridica in Italia con particolare riferimento al modello dello psicologo e psichiatra Sante de Sanctis promotore del metodo integrato
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