Converting water adsorption and capillary condensation in useable forces with simple porous inorganic thin films

This work reports an innovative humidity driven actuation concept based on Bangham effect using simple nanoporous sol-gel silica thin films as humidity responsive materials. Bilayer shaped actuators, consisting on a humidity-sensitive active nanostructured silica film deposited on a polymeric substrate (Kapton) were demonstrated as an original mean to convert water molecule adsorption and capillary condensation in useable mechanical work. Reversible silica surface energy modifications by water adsorption and the energy produced by the rigid silica film contraction, induced by water capillary condensation in mesopores, were finely controlled and used as the energy sources. The influence of the film nanostructure (microporosity, mesoporosity) and thickness, and of the polymeric support thickness, on the actuation force, on the movement speed, and on the amplitude of displacement are clearly evidenced and discussed. We show that the global mechanical response of such silica-based actuators can be easily adjusted to fabricate a humidity variation triggered tailor-made actuation systems. This first insight in hard ceramic stimulus responsive materials may open the door toward new generation of surface chemistry driven actuation systems.Comment: 17 pages, 7 figure

Recent advances in smart biotechnology: Hydrogels and nanocarriers for tailored bioactive molecules depot

Over the past ten years, the global biopharmaceutical market has remarkably grown, with ten over the top twenty worldwide high performance medical treatment sales being biologics. Thus, biotech R&D (research and development) sector is becoming a key leading branch, with expanding revenues. Biotechnology offers considerable advantages compared to traditional therapeutic approaches, such as reducing side effects, specific treatments, higher patient compliance and therefore more effective treatments leading to lower healthcare costs. Within this sector, smart nanotechnology and colloidal self-assembling systems represent pivotal tools able to modulate the delivery of therapeutics. A comprehensive understanding of the processes involved in the self assembly of the colloidal structures discussed therein is essential for the development of relevant biomedical applications. In this review we report the most promising and best performing platforms for specific classes of bioactive molecules and related target, spanning from siRNAs, gene/plasmids, proteins/growth factors, small synthetic therapeutics and bioimaging probes.Istituto Italiano di Tecnologia (IIT)COST Action [CA 15107]People Program (Marie Curie Actions) of the European Union's Seventh Framework Program under REA [606713 BIBAFOODS]Portuguese Foundation for Science and Technology (FCT) [PTDC/AGR-TEC/4814/2014, IF/01005/2014]Fundacao para a Ciencia e Tecnologia [SFRH/BPD/99982/2014]Danish National Research Foundation [DNRF 122]Villum Foundation [9301]Italian Ministry of Instruction, University and Research (MIUR), PRIN [20109PLMH2]"Fondazione Beneficentia Stiftung" VaduzFondo di Ateneo FRAFRAinfo:eu-repo/semantics/publishedVersio

Thermoresponsive smart copolymer coatings based on P(NIPAM co-HEMA) and P(OEGMA-co-HEMA) brushes for regenerative medicine

The fabrication of multifunctional, thermoresponsive platforms for regenerative medicine based on polymers that can be easily functionalized is one of the most important challenges in modern biomaterials science. In this study, we utilized atom transfer radical polymerization (ATRP) to produce two series of novel smart copolymer brush coatings. These coatings were based on copolymerizing 2-hydroxyethyl methacrylate (HEMA) with either oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or N-isopropylacrylamide (NIPAM). The chemical compositions of the resulting brush coatings, namely, poly(oligo(ethylene glycol) methyl ether methacrylate-co-2-hydroxyethyl methacrylate) (P(OEGMA-co-HEMA)) and poly(N-isopropylacrylamide-co-2- hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)), were predicted using reactive ratios of the monomers. These predictions were then verified using time-of-flight-secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The thermoresponsiveness of the coatings was examined through water contact angle (CA) measurements at different temperatures, revealing a transition driven by lower critical solution temperature (LCST) or upper critical solution temperature (UCST) or a vanishing transition. The type of transition observed depended on the chemical composition of the coatings. Furthermore, it was demonstrated that the transition temperature of the coatings could be easily adjusted by modifying their composition. The topography of the coatings was characterized using atomic force microscopy (AFM). To assess the biocompatibility of the coatings, dermal fibroblast cultures were employed, and the results indicated that none of the coatings exhibited cytotoxicity. However, the shape and arrangement of the cells were significantly influenced by the chemical structure of the coating. Additionally, the viability of the cells was correlated with the wettability and roughness of the coatings, which determined the initial adhesion of the cells. Lastly, the temperature-induced changes in the properties of the fabricated copolymer coatings effectively controlled cell morphology, adhesion, and spontaneous detachment in a noninvasive, enzyme-free manner that was confirmed using optical microscopy

Cell-adhesion Activities Responding to Nano-Dynamic Substrate

Focal adhesions are the large molecular complexes that anchor cells to the ECM, which is involved in cell spreading, migration, and proliferation. In our previous work, the study of cardiomyocyte morphological changes and myofibril remodeling, responding to the dynamic nano-topographic substrate, have been accomplished. The results showed focal adhesion experienced disassembly and reassembly in the first 12 hours. In this study, the hiPSC-CMs were seeded on the SMP substrates with the flat-to-wrinkle dynamic surface. Paxillin, vinculin, and zyxin from different layers of focal adhesive architectures were co-stained with F-actin. The fluorescent images were analyzed to investigate the details of focal adhesions remodeling and the dynamics of costameres in the first stage post triggering the substrate wrinkle formation

Bioengineered Textiles and Nonwovens – the convergence of bio-miniaturisation and electroactive conductive polymers for assistive healthcare, portable power and design-led wearable technology

Today, there is an opportunity to bring together creative design activities to exploit the responsive and adaptive ‘smart’ materials that are a result of rapid development in electro, photo active polymers or OFEDs (organic thin film electronic devices), bio-responsive hydrogels, integrated into MEMS/NEMS devices and systems respectively. Some of these integrated systems are summarised in this paper, highlighting their use to create enhanced functionality in textiles, fabrics and non-woven large area thin films. By understanding the characteristics and properties of OFEDs and bio polymers and how they can be transformed into implementable physical forms, innovative products and services can be developed, with wide implications. The paper outlines some of these opportunities and applications, in particular, an ambient living platform, dealing with human centred needs, of people at work, people at home and people at play. The innovative design affords the accelerated development of intelligent materials (interactive, responsive and adaptive) for a new product & service design landscape, encompassing assistive healthcare (smart bandages and digital theranostics), ambient living, renewable energy (organic PV and solar textiles), interactive consumer products, interactive personal & beauty care (e-Scent) and a more intelligent built environment

Glycidyl Ether-Based Coatings on Polystyrene Culture Substrates for Temperature-Triggered Cell Sheet Fabrication

Within this work, thermoresponsive coatings based on poly(glycidyl ether)s (PGEs) were developed for applied polystyrene (PS) tissue culture substrates. Following the “grafting to“ approach, block copolymers comprising a random, high molecular weight, thermoresponsive block and a short, hydrophobic benzophenone (BP) block were synthesized via the sequential, monomer-activated, oxy-anionic ring-opening polymerization (ROP). Ultrathin layers in the sub-nanometer range were immobilized on PS by physical adsorption and UV-induced C, H-insertion of PGE block copolymers via their photo-reactive BP anchor block. The coatings mediated the adhesion of human dermal fibroblasts (HDFs) and allowed the temperature triggered detachment of confluent cell sheets. HDF sheet detachment was found to be induced by the cooperative effects between the partial rehydration of the PGE chains and the cell repellant PS substrate background. In order to improve the performance of PGE monolayers, block copolymers were subsequently self-assembled on PS substrates from dilute aqueous solution under selective solvent conditions. UV immobilization yielded thermoresponsive polymer brushes, which undergo a “pancake-to-brush” transition upon temperature reduction. The improved structure and thermal response of the brush-like PGE coatings as well as the optimization of cell culture parameters facilitated the fabrication of confluent HDF, human aortic smooth muscle cell (HAoSMC) and human umbilical vein endothelial cell (HUVEC) sheets, which constitute the main building blocks of blood vessels. To functionalize PS culture substrates via the “grafting from” approach, a solvent-free, microwave-assisted synthesis of well-defined oligo(glycidyl ether)s (OGEs) was developed. Fast reaction rates could be solely attributed to the high reaction temperatures reached during microwave heating and the obtained oligomers exhibited highly molecular weight- and concentration-dependent CPTs in water. Further, end-functional oligo(glycidyl ether) acrylate (OGEA) macromonomers were synthesized by in situ quenching of the oxy-anionic ROP. Subsequently, a photopolymerization process was developed to graft OGEA macromonomers from PS culture substrates. Surfaceinitiated photografting from bulk macromonomer films yielded porous, rigid, gel-like OGEA coatings with unique bottlebrush properties. Bottlebrushes with optimized structure proved to be functional coatings for the fabrication of HDF sheets. The controlled detachment of cell sheets was found to be triggered by the rehydration of OGEA bottlebrush side chains rather than a macroscopic swelling of the gel-like coatings upon temperature reduction. In summary, this work introduces facile methods for the functionalization of applied PS tissue culture surfaces with thermoresponsive, PGE-based coatings and demonstrates their high potential as functional substrates for cell sheet fabrication

SYNTHESIS AND CHARACTERIZATION OF THERMALLY RESPONSIVE POLYMER LAYERS

Future devices such as biomedical and microfluidic devices, to a large extent, will depend on the interactions between the device surfaces and the contacting liquid. Further, biological liquids containing proteins call for controllable interactions between devices and such proteins, however the bulk material must retain the inherent mechanical properties from which the device was fabricated from. It is well known that surface modification is a suitable technique to tune the surface properties without sacrificing the bulk properties of the substrate. In the present study, surface properties were modified through temperature responsive polymer layers. After the modification, the surfaces gained switchability toward protein interaction as well as surface wettability properties. Poly(N-isopropylacrylamide) (PNIPAM), a well studied thermo-responsive polymer was utilized in the subsequent work. Firstly, thermally responsive brushes made from well defined block copolymers incorporating NIPAM and the surface reactive monomer, glycidyl methacrylate (GMA) were fabricated in a single step process. Reaction of the PGMA block with surface hydroxyl groups anchors the polymers to the surface yet allows PNIPAM to assemble at the interface at high enough concentration to exhibit thermally responsive properties in aqueous solutions. Surface properties of the resulting brushes prepared the 1-step process are compared to characteristics of PNIPAM brushes synthesized by already established methods. The thickness, swelling, and protein adsorption of the PNIPAM films were studied by ellipsometry. Chemical composition of the layer was studied by angle-resolved x-ray photoelectron spectroscopy. Film morphologies and forces of adhesion to fibrinogen were examined using atomic force microscopy (AFM) tapping mode and colloidal probe technique. Block copolymer (BCP) and conventional brush films were abraded and subsequently examined for changes in thermally responsive behavior. The results show that deposition of PNIPAM-b-PGMA provides an effective route to create thermally responsive brushes via a 1-step process, with properties equaling and surpassing that of traditional brushes obtained in multiple steps. Further, the 1-step deposition of reactive BCPs can be extended to fabricate mixed block copolymer films. Well defined BCP containing ethylene glycol and GMA were deposited from a joint solution with PNIPAM-b-PGMA. Mixed brush films were also fabricated via a 2-step process for comparison of the resulting properties. PNIPAM BCP layers were utilized as the grafted primary layer with which end-functionalized PEG was grafted in a second step. Protein adhesion and adsorption of the resulting mixed brush films were studied by AFM colloidal probe technique and ellipsometry. In the next part of the work reported, monolayers of PNIPAM containing nanogels were anchored to the surface of silicon wafers, glass slides, polyvinylidene fluoride (PVDF) fibers, and tungsten wires using a \u27grafting to\u27 approach. The particles of were synthesized with different diameters by free radical precipitation polymerization and reversible addition chain transfer polymerization (RAFT) techniques. The behavior of the synthesized grafted layers with the behavior of PNIPAM brushes (densely end-grafted) is compared. Indeed, the grafted monolayer swells and collapses reversibly at temperatures below and above the transition temperature of PNIPAM. AFM in aqueous environment was utilized to study the actuation behavior of the nanogel films. Wettability studies of the grafted layers were performed using various contact angle measurement methods to determine the contact angle changes on different substrates. New methods for the development of thermally responsive polymer films are described. The methods enable the grafting of films with tunable film thickness, temperature response, and well defined biological interaction. The complete grafting of the responsive polymer films require no organic rinsing after grafting step

Temperature-responsive polymer brush coatings for advanced biomedical applications

Modern biomedical technologies predict the application of materials and devices that not only can comply effectively with specific requirements, but also enable remote control of their functions. One of the most prospective materials for these advanced biomedical applications are materials based on temperature-responsive polymer brush coatings (TRPBCs). In this review, methods for the fabrication and characterization of TRPBCs are summarized, and possibilities for their application, as well as the advantages and disadvantages of the TRPBCs, are presented in detail. Special attention is paid to the mechanisms of thermo-responsibility of the TRPBCs. Applications of TRPBCs for temperature-switchable bacteria killing, temperature-controlled protein adsorption, cell culture, and temperature-controlled adhesion/detachment of cells and tissues are considered. The specific criteria required for the desired biomedical applications of TRPBCs are presented and discussed