Browsing by Subject "POLYMER"

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  • Nahm, Daniel; Weigl, Franziska; Schaefer, Natascha; Sancho, Ana; Frank, Andreas; Groll, Jürgen; Villmann, Carmen; Schmidt, Hans-Werner; Dalton, Paul D.; Luxenhofer, Robert (2020)
    In this study, we designed a novel biomaterial ink platform based on hydrophilic poly(2-ethyl-2-oxazine) (PEtOzi) specifically for melt electrowriting (MEW). This material crosslinks spontaneously after processing via dynamic Diels–Alder click chemistry. These direct-written microperiodic structures rapidly swell in water to yield thermoreversible hydrogels. These hydrogels are robust enough for repeated aspiration and ejection through a cannula without structural damage, despite their high water content of 84%. Moreover, the scaffolds retain functional groups for modification using click chemistry and therefore can be readily functionalized as demonstrated using fluorophores and peptides to facilitate visualization and cell attachment. The PEtOzi hydrogel developed here is compatible with confocal imaging and staining protocols for cells. In summary, an advanced material platform based on PEtOzi is reported that is compatible with MEW and results in functionalizable chemically crosslinked microperiodic hydrogels.
  • Liu, Dongfei; Chen, Jian; Jiang, Tao; Li, Wei; Huang, Yao; Lu, Xiyi; Liu, Zehua; Zhang, Weixia; Zhou, Zheng; Ding, Qirui; Almeida Santos, Helder; Yin, Guoyong; Fan, Jin (2018)
    New treatment strategies for spinal cord injury with good therapeutic efficacy are actively pursued. Here, acetalated dextran (AcDX), a biodegradable polymer obtained by modifying vicinal diols of dextran, is demonstrated to protect the traumatically injured spinal cord. To facilitate its administration, AcDX is formulated into microspheres (approximate to 7.2 mu m in diameter) by the droplet microfluidic technique. Intrathecally injected AcDX microspheres effectively reduce the traumatic lesion volume and inflammatory response in the injured spinal cord, protect the spinal cord neurons from apoptosis, and ultimately, recover the locomotor function of injured rats. The neuroprotective feature of AcDX microspheres is achieved by sequestering glutamate and calcium ions in cerebrospinal fluid. The scavenging of glutamate and calcium ion reduces the influx of calcium ions into neurons and inhibits the formation of reactive oxygen species. Consequently, AcDX microspheres attenuate the expression of proapoptotic proteins, Calpain, and Bax, and enhance the expression of antiapoptotic protein Bcl-2. Overall, AcDX microspheres protect traumatically injured spinal cord by alleviating the glutamate-induced excitotoxicity. This study opens an exciting perspective toward the application of neuroprotective AcDX for the treatment of severe neurological diseases.
  • Golda-Cepa, Monika; Riedlova, Kamila; Kulig, Waldemar; Cwiklik, Lukasz; Kotarba, Andrzej (2020)
    Interactions at the solid-body fluid interfaces play a vital role in bone tissue formation at the implant surface. In this study, fully atomistic molecular dynamics (MD) simulations were performed to investigate interactions between the physiological components of body fluids (Ca2+, HPO42-, H2PO4-, Na+, Cl-, and H2O) and functionalized parylene C surface. In comparison to the native parylene C (-Cl surface groups), the introduction of -OH, -CHO, and -COOH surface groups significantly enhances the interactions between body fluid ions and the polymeric surface. The experimentally observed formation of calcium phosphate nanocrystals is discussed in terms of MD simulations of the calcium phosphate clustering. Surface functional groups promote the clustering of calcium and phosphate ions in the following order: -OH > -CHO > -Cl (parent parylene C) approximate to -COO-. This promoting role of surface functional groups is explained as stimulating the number of Ca2+ and HPO42- surface contacts as well as ion chemisorption. The molecular mechanism of calcium phosphate cluster formation at the functionalized parylene C surface is proposed.
  • Salomäki, Mikko; Jaakkola, Oskari; Hirvonen, Sami-Pekka; Tenhu, Heikki; Kvarnström, Carita (2018)
    Thin films of water dispersible poly(ethylene oxide) (PEO) functionalized poly(benzimidazobenzophenanthroline) (BBL) polymers have been prepared by a pulse spray technique on a spinning substrate in ambient atmosphere. The deposition method is advantageous for generating ultra-thin films of nanometer thicknesses. A single spray pulse was found in a reproducible manner to generate a layer of ca. 2 nm thickness. The PEO-chain length in the BBL functionalization had an essential influence on the building mechanism of the films. The polymers functionalized by short PEO chains induced the formation of very smooth films while longer PEO chains induced rough films and notable nanostructuration. The BBL-PEO film deposited using spray pulse deposition was found to be electro- and photoactive. The electron transfer processes observed are slightly different from earlier reported results for similar polymers, which is probably due to the very thin film. The films exhibited photocurrent generation when transformed into conducting form.
  • Akmal, Jan Sher; Salmi, Mika; Mäkitie, Antti; Björkstrand, Roy; Partanen, Jouni (2018)
    The purpose of this study is to demonstrate the ability of additive manufacturing, also known as 3D printing, to produce effective drug delivery devices and implants that are both identifiable, as well as traceable. Drug delivery devices can potentially be used for drug release in the direct vicinity of target tissues or the selected medication route in a patient-specific manner as required. The identification and traceability of additively manufactured implants can be administered through radiofrequency identification systems. The focus of this study is to explore how embedded medication and sensors can be added in different additive manufacturing processes. The concept is extended to biomaterials with the help of the literature. As a result of this study, a patient-specific drug delivery device can be custom-designed and additively manufactured in the form of an implant that can identify, trace, and dispense a drug to the vicinity of a selected target tissue as a patient-specific function of time for bodily treatment and restoration.
  • Oleyaei, Seyed Amir; Razavi, Seyed Mohammad Ali; Mikkonen, Kirsi Susanna (2018)
    In this study, the physico-chemical and rheo-mechanical properties of sage seed gum hydrogel, reinforced by various ratios (0-25 wt.%) of Laponite, were investigated. Particles size measurements indicated the formation of large SSG-Laponite microstructures upon nanoparticle adding, due to the interactions generated between the anionic SSG and the charged surfaces of clay platelets. Laponite affected the surface tension and density of the SSG-based systems significantly, but only influenced the-potential above 20 wt.%. The dynamic rheological behavior of SSG-based nanocomposites reflected the reinforcing effect of secondary structures and percolated three-dimensional network, suggested a structural modification of the hydrogels with the Laponite loading. An improvement in texture profile analysis parameters was observed in Laponite content 5 wt.%, whereas for nanoparticles > 5 wt.%, a significant decrease was obtained. In conclusion, Laponite improved the rheological and physico-chemical properties of SSG-based hydrogel and extended its potential as promising future bio-products for industrial applications.
  • Pooch, Fabian; Sliepen, Marjolein; Knudsen, Kenneth D.; Nyström, Bo; Tenhu, Heikki; Winnik, Francoise M. (2019)
    Poly(2-isopropyl-2-oxazoline)-b-poly(lactide) (PiPOx-b-PLA) diblock copolymers comprise two miscible blocks: the hydrophilic and thermosensitive PiPOx and the hydrophobic PLA, a biocompatible and biodegradable polyester. They self-assemble in water, forming stable dispersions of nanoparticles with hydrodynamic radii (R-h) ranging from similar to 18 to 60 nm, depending on their molar mass, the relative size of the two blocks, and the configuration of the lactide unit. Evidence from H-1 nuclear magnetic resonance spectroscopy, light scattering, small-angle neutron scattering, and cryo-transmission electron microscopy indicates that the nanoparticles do not adopt the typical core-shell morphology. Aqueous nanoparticle dispersions heated from 20 to 80 degrees C were monitored by turbidimetry and microcalorimetry. Nanoparticles of copolymers containing a poly(DL-lactide) block coagulated irreversibly upon heating to 50 degrees C, forming particles' of various shapes (R-h similar to 200-500 nm). Dispersions of PiPOx-b-poly(L-lactide) coagulated to a lesser extent or remained stable upon heating. From the entire experimental evidence, we conclude that PiPOx-b-PLA nanoparticles consist of a core of PLA/PiPOx chains associated via dipole-dipole interactions of the PLA and PiPOx carbonyl groups. The core is surrounded by tethered PiPOx loops and tails responsible for the colloidal stability of the nanoparticles in water. While the core of all nanoparticles studied contains associated PiPOx and PLA blocks, fine details of the nanoparticles morphology vary predictably with the size and composition of the copolymers, yielding particles of distinctive thermosensitivity in aqueous dispersions.
  • Dobryden, Illia; Ruiz, Maria Cortes; Zhang, Xuwei; Dedinaite, Andra; Wieland, D. C. Florian; Winnik, Francoise M.; Claesson, Per M. (2019)
    The adsorption of hydrophilic or amphiphilic multiblock copolymers provides a powerful means to produce well-defined "smart" surfaces, especially if one or several blocks are sensitive to external stimuli. We focus here on an A-B-A-B-A copolymer, where A is a cationic poly((3acrylamido-propyl)-trimethylammonium chloride) (PAMPTMA) block containing 15 (end blocks) or 30 (middle block) repeat units and B is a neutral thermosensitive water-soluble poly(2-isopropyl-2-oxazoline) (PIPOZ) block with 50 repeat units. X-ray reflectivity and quartz crystal microbalance with dissipation monitoring were employed to study the adsorption of PAMPTMA(15)-PAMPTMA(30)-PIPOZ(50)-PAMPTMA(15) on silica surfaces. The latter technique was employed at different temperatures up to 50 degrees C. Surface forces and friction between the two silica surfaces across aqueous pentablock copolymer solutions at different temperatures were determined with the atomic force microscopy colloidal probe force and friction measurements. The cationic pentablock copolymer was found to have a high affinity to the negatively charged silica surface, leading to a thin (2 nm) and rigid adsorbed layer. A steric force was encountered at a separation of around 3 nm from hard wall contact. A capillary condensation of a polymer-rich phase was observed at the cloud point of the solution. The friction forces were evaluated using Amontons' rule modified with an adhesion term.
  • Haider, Malik Salman; Ahmad, Taufiq; Yang, Mengshi; Hu, Chen; Hahn, Lukas; Stahlhut, Philipp; Groll, Jurgen; Luxenhofer, Robert (2021)
    As one kind of "smart" material, thermogelling polymers find applications in biofabrication, drug delivery and regenerative medicine. In this work, we report a thermosensitive poly(2-oxazoline)/poly(2-oxazine) based diblock copolymer comprising thermosensitive/moderately hydrophobic poly(2-N-propyl-2-oxazine) (pPrOzi) and thermosensitive/moderately hydrophilic poly(2-ethyl-2-oxazoline) (pEtOx). Hydrogels were only formed when block length exceeded certain length (approximate to 100 repeat units). The tube inversion and rheological tests showed that the material has then a reversible sol-gel transition above 25 wt.% concentration. Rheological tests further revealed a gel strength around 3 kPa, high shear thinning property and rapid shear recovery after stress, which are highly desirable properties for extrusion based three-dimensional (3D) (bio) printing. Attributed to the rheology profile, well resolved printability and high stackability (with added laponite) was also possible. (Cryo) scanning electron microscopy exhibited a highly porous, interconnected, 3D network. The sol-state at lower temperatures (in ice bath) facilitated the homogeneous distribution of (fluorescently labelled) human adipose derived stem cells (hADSCs) in the hydrogel matrix. Post-printing live/dead assays revealed that the hADSCs encapsulated within the hydrogel remained viable (approximate to 97%). This thermoreversible and (bio) printable hydrogel demonstrated promising properties for use in tissue engineering applications.