1,721,330 research outputs found
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 loops-forming surface-grafted assemblies, enables a broad modulation of highly relevant, interfacial physicochemical 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 [1]. 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 [2].
Polymer topology 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
“Topological Control Over the Interfacial Physico-Chemical Properties of Polymer Assemblies”
No full textThe application of distinctive polymer topologies, beyond linearity, to yield cyclic and loops-forming 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 [1]. 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 [2].
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.
[1] G. Morgese, L. Trachsel, M. Romio, M. Divandari, S.N. Ramakrishna, E.M. Benetti
Angew. Chem. Int. Ed. 2016, 55, 15583.
[2] G. Morgese, B.S. Shaghasemi, V. Causin, M. Zenobi-Wong, S.N. Ramakrishna, E. Reimhult, E.M. Benetti
Angew. Chem. Int. Ed. 2017, 56, 4507
“God Made the Bulk, the Surface was Invented by the Devil”: Topological Control Over the Interfacial Physico-Chemical Properties of Polymer Assemblies
No full textThe application of polymer topologies, beyond chain linearity, to yield polymer brushes enables to surpass the unique physicochemical properties of their linear equivalents.
This is especially valid on flat surfaces (1), where the ultra-dense and highly compact character of cyclic brushes provide an enhanced steric stabilization of the interface and a superlubricious behavior. Alternatively, when cyclic brushes form shells on inorganic nanoparticles (NPs) (2), 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 that seem to confirm Wolfgang Pauli’s famous statement: “God made the bulk, the surface was invented by the devil.”
(1) Angew. Chem., Int. Ed. 2016, 55, 15583.
(2) Angew. Chem., Int. Ed. 2017, 56, 4507
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
Quasi-3D-Structured Interfaces by Polymer Brushes
No full textThe fabrication of polymer brushes via surface-initiated controlled radical polymerizations has progressively developed beyond a simple surface functionalization technique, enabling the design of complex polymer interfaces with a quasi-3D molecular organization. The modulation of polymer brush structure has led to an extremely broad tuning potential for technologically relevant interfacial, physicochemical properties, allowing one to precisely tune swelling, nanomechanical, and nanotribological characteristics of polymer films. In addition, the synthesis of multilayer brush interfaces with hierarchical architecture has been exploited to control biological phenomena on modified platforms, such as cell adhesion and settlement, or to fully prevent biological contamination from bacteria. In this feature article, the most recent developments in the synthesis and application of quasi-3D structured polymer brushes are summarized, placing particular attention on how the tuning of grafted-polymer architecture could translate into a variation of interfacial characteristics
Screening for diabetic retinopathy: 1 and 3 nonmydriatic 45-degree digital fundus photographs vs 7 standard early treatment diabetic retinopathy study fields.
No full textAm J Ophthalmol. 2009 Jul;148(1):111-8. Epub 2009 May 5.
Screening for diabetic retinopathy: 1 and 3 nonmydriatic 45-degree digital fundus photographs vs 7 standard early treatment diabetic retinopathy study fields.
Vujosevic S, Benetti E, Massignan F, Pilotto E, Varano M, Cavarzeran F, Avogaro A, Midena E.
Source
Fondazione G.B. Bietti per l'Oftalmologia, IRCCS (Istituto di Ricovero e Cura a Carattere Scientificio), Roma, Italy.
Abstract
PURPOSE:
To evaluate if simple- or multiple-field digital color nonmydriatic (NM) retinal images can replace 7 standard stereoscopic fundus photographs in the screening of diabetic retinopathy (DR).
DESIGN:
Prospective, masked, comparative case series.
METHODS:
One hundred and eight eyes of 55 diabetics were studied to determine single lesions and to grade clinical levels of DR and diabetic macular edema (DME) using both 1 and 3 NM digital color retinal images compared with the Early Treatment Diabetic Retinopathy Study (ETDRS) 7 standard 35-mm stereoscopic color fundus photographs (7F-ETDRS). All eyes underwent NM 45-degree field images of 1 central field (1F-NM), NM 45-degree field images of 3 fields (3F-NM), and, after pupil dilatation, 30-degree 7F-ETDRS photography. Images were analyzed by 2 independent, masked retinal specialists (S.V. and E.B.), lesion-by-lesion according to the ETDRS protocol and for clinical severity level of DR and DME according to the international classification of DR.
RESULTS:
Using 7F-ETDRS as the gold standard, agreement was substantial for grading clinical levels of DR and DME (kappa = 0.69 and kappa = 0.75) vs 3F-NM; moderate for DR level (kappa = 0.56) and substantial for DME (kappa = 0.66) vs 1F-NM; almost perfect for detecting presence or absence of DR (kappa = 0.88) vs both 1F-NM and 3F-NM; and almost perfect for presence or absence of DME (kappa = 0.97) vs 3F-NM and substantial (kappa = 0.75) vs 1F-NM. Sensitivity and specificity for detecting referable levels of DR were 82% and 92%, respectively, for 3F-NM and 71% and 96%, respectively, for 1F-NM.
CONCLUSIONS:
Three color 45-degree NM fundus fields may be an effective tool in a screening setting to determine critical levels of DR and DME for prompt specialist referral. One central 45-degree image is sufficient to determine absence or presence of DR and DME, but not for grading it
Surface-Initiated Cu(0)-Mediated CRP for the Rapid and Controlled Synthesis of Quasi-3D Structured Polymer Brushes
No full textSurface-initiated controlled radical polymerization mediated by Cu(0) plate (SI-Cu(0) plate -CRP) is an extremely effective and versatile technique for the synthesis of functional polymer brushes from vinyl monomers on planar substrates. The advantages of SI-Cu(0) plate -CRP in comparison to "classical" SI-CRP methods not only rely on the easy accessibility, handling, and recycling of the catalyst source, but also on the faster brush growth rates, and exceptionally high reinitiation efficiencies and grafting densities for the obtained brushes. The confined geometry of the SI-Cu(0) plate -CRP reaction setup, with a Cu(0) plate placed in close proximity to the initiator bearing substrate, considerably simplifies the preparation of polymer brushes over large areas, and the fabrication of gradient, patterned and arrayed polymer brushes. In this viewpoint we summarize the recent developments and applications of SI-Cu(0) plate -CRP, emphasizing its mechanism, advantages, and standing challenges
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
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