Ultrathin, freestanding, stimuli-responsive, porous membranes from polymer hydrogel-brushes

Responsive nanoporous polymeric membranes with tunable morphologies are fabricated by combining self-assembly of particles from liquid interfaces (SALI) and surface-initiated polymerization (SIP).</p

Chemical design of non-ionic polymer brushes as biointerfaces : poly(2-oxazine)s outperform both poly(2-oxazoline)s and PEG

The era of poly(ethylene glycol) (PEG) brushes as a universal panacea for preventing non-specific protein adsorption and providing lubrication to surfaces is coming to an end. In the functionalization of medical devices and implants, in addition to preventing non-specific protein adsorption and cell adhesion, polymer-brush formulations are often required to generate highly lubricious films. Poly(2-alkyl-2-oxazoline) (PAOXA) brushes meet these requirements, and depending on their side-group composition, they can form films that match, and in some cases surpass, the bioinert and lubricious properties of PEG analogues. Poly(2-methyl-2-oxazine) (PMOZI) provides an additional enhancement of brush hydration and main-chain flexibility, leading to complete bioinertness and a further reduction in friction. These data redefine the combination of structural parameters necessary to design polymer-brush-based biointerfaces, identifying a novel, superior polymer formulation

Thin Polymer Brush Decouples Biomaterial's Micro-/Nano-Topology and Stem Cell Adhesion

Surface morphology and chemistry of polymers used as biomaterials, such as tissue engineering scaffolds, have a strong influence on the adhesion and behavior of human mesenchymal stem cells. Here we studied semicrystalline poly(ε-caprolactone) (PCL) substrate scaffolds, which exhibited a variation of surface morphologies and roughness originating from different spherulitic superstructures. Different substrates were obtained by varying the parameters of the thermal processing, i.e. crystallization conditions. The cells attached to these polymer substrates adopted different morphologies responding to variations in spherulite density and size. In order to decouple substrate topology effects on the cells, sub-100 nm bio-adhesive polymer brush coatings of oligo(ethylene glycol) methacrylates were grafted from PCL and functionalized with fibronectin. On surfaces featuring different surface textures, dense and sub-100 nm thick brush coatings determined the response of cells, irrespective to the underlying topology. Thus, polymer brushes decouple substrate micro-/nano-topology and the adhesion of stem cells

Molecular engineering of designer surfaces by controlled radical polymerizations : brushes, hedges and hybrid grafts

The aim of the work described in this Thesis was to develop new\ud fabrication techniques based on surface-initiated controlled polymerization (SIP)\ud for the preparation of functional polymeric platforms across the lengthscales.\ud Several synthetic processes based on controlled radical SIP were employed for\ud the preparation of polymer brush platforms which presented tunable\ud characteristics and, in some instances, a stimulus-responsive behavior. The SIP\ud methods employed were furthermore coupled with atomic force microscopy\ud (AFM)-assisted nanolithographic approaches in order to accomplish the\ud preparation of polymer grafts constituted by a limited number of macromolecules\ud grown on pre-determined positions on surfaces

Using Polymers to Impart Lubricity and Biopassivity to Surfaces: Are These Properties Linked?

Polymer brushes have been widely applied for the reduction of both friction and non‐specific protein adsorption. In many (but not all) applications, such as contact lenses or medical devices, this combination of properties is highly desirable. Indeed, for many polymer‐brush systems, lubricity and resistance to biofouling appear to go hand in hand, with modifications of brush architecture, for example, leading to a similar degree of enhancement (or degradation) in both properties. In the case of poly(ethylene glycol) (PEG) brushes, this has been widely demonstrated. There are, however, examples where this behavior breaks down. In systems where linear brushes are covalently crosslinked during surface‐initiated polymerization (SIP), for example, the presence and the chemical nature of links between grafted chains might or might not influence biopassivity of the films, while it always causes an increment in friction. Furthermore, when the grafted‐chain topology is shifted from linear to cyclic, chemically identical brushes show a substantial improvement in lubrication, whereas their protein resistance remains unaltered. Architectural control of polymer brush films can provide another degree of freedom in the design of lubricious and biopassive coatings, leading to new combinations of surface properties and their independent modulation.ISSN:0018-019XISSN:1522-267

Lateral Deformability of Polymer Brushes by AFM-Based Method

none2mixedRamakrishna SN; Benetti ERamakrishna, Sn; Benetti,

Application of Polymer Brush-Shells on Nanoparticles for Controlling Interaction with Serum

The interaction of nanoparticles (NPs) with biological environments triggers the formation of a protein corona (PC), which significantly influences their behaviour in vivo. This review explores the evolving understanding of PC formation, focusing on the opportunity for decreasing or suppressing protein-NP interactions by macromolecular engineering of NP shells. The functionalization of NPs with a dense, hydrated polymer brush-shell is a powerful strategy to impart stealth properties in order to elude recognition by the immune system. While poly(ethylene glycol) (PEG) has been extensively used for this purpose, concerns regarding its stability and immunogenicity have prompted exploration of alternative polymers. The stealth properties of brush shells can be enhanced by tailoring functionalities and structural parameters, including molar mass, grafting density and polymer topology. Determining correlations between these parameters and biopassivity has enabled to obtain polymer-grafted NPs with high colloidal stability and prolonged circulation time in biological media

Tunable thermoresponsive polymeric platforms on gold by "photoiniferter" : based surface grafting

Thermoresponsive brushes with a tunable structure are grafted in a controlled way to gold substrates, exploiting an initiator-transfer-terminator agent (iniferter)-based photopolymerization. The chain length of the polymers is controlled by using UV light as a trigger and the end groups exposed are shown to be easily exchangeable following the grafting process. Reversible volume shrinkage/expansion, roughening, and variation of adhesion are observed

The role of poly(2-alkyl-2-oxazoline)s in hydrogels and biofabrication

Poly(2-alkyl-2-oxazoline)s (PAOXAs) have been rapidly emerging as starting materials in the design of tissue engineering supports and for the generation of platforms for cell cultures, especially in the form of hydrogels. Thanks to their biocompatibility, chemical versatility and robustness, PAOXAs now represent a valid alternative to poly(ethylene glycol)s (PEGs) and their derivatives in these applications, and in the formulation of bioinks for three-dimensional (3D) bioprinting. In this review, we summarize the recent literature where PAOXAs have been used as main components for hydrogels and biofabrication mixtures, especially highlighting how their easily tunable composition could be exploited to fabricate multifunctional biomaterials with an extremely broad spectrum of properties.ISSN:2047-4830ISSN:2047-484