RESUMO
Poly(2-oxazoline)s (POx) bottle-brush brushes have excellent biocompatible and lubricious properties, which are promising for the functionalization of surfaces for biomedical devices. Herein, a facile synthesis of POx is reported which is based bottle-brush brushes (BBBs) on solid substrates. Initially, backbone brushes of poly(2-isopropenyl-2-oxazoline) (PIPOx) were fabricated via surface initiated Cu0 plate-mediated controlled radical polymerization (SI-Cu0 CRP). Poly(2-methyl-2-oxazoline) (PMeOx) side chains were subsequently grafted from the PIPOx backbone via living cationic ring opening polymerization (LCROP), which result in ≈100 % increase in brush thickness (from 58 to 110â nm). The resultant BBBs shows tunable thickness up to 300â nm and high grafting density (σ) with 0.42â chains nm-2 . The synthetic procedure of POx BBBs can be further simplified by using SI-Cu0 CRP with POx molecular brush as macromonomer (Mn =536â g mol-1 , PDI=1.10), which results in BBBs surface up to 60â nm with well-defined molecular structure. Both procedures are significantly superior to the state-of-art approaches for the synthesis of POx BBBs, which are promising to design bio-functional surfaces.
Assuntos
Materiais Biocompatíveis/síntese química , Oxazóis/síntese química , Cobre/química , Estrutura Molecular , Oxazóis/química , Poliaminas/química , Polimerização , Polipropilenos/químicaRESUMO
The shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (Tg ) or melting (Tm )], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m-1 , material-water interfacial tension <6 mN m-1 ), especially if the nanoparticles are soft (<1 GPa), rough (Rrms > 10 nm), porous (>1 m2 g-1 ), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale.
Assuntos
Sistemas de Liberação de Medicamentos , Nanopartículas/química , Módulo de Elasticidade , Hidrodinâmica , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas/ultraestrutura , Porosidade , Dióxido de Silício/química , Eletricidade Estática , Propriedades de SuperfícieRESUMO
2D mussel-inspired polydopamine (PDA) nanosheets are prepared and exploited as a functional surface for grafting various polymer brushes. The PDA nanosheet and its polymer-brush derivatives show lateral integrity and are robust; therefore, they can be detached from their substrates. Cell-adhesion tests show that the PDA nanosheet promotes cell growth and attachment, while a PDA-based poly(3-sulfopropyl methacrylate) carpet exhibits nonfouling behavior.
Assuntos
Materiais Biomiméticos/química , Materiais Biomiméticos/farmacologia , Bivalves , Indóis/química , Indóis/farmacologia , Nanoestruturas/química , Processos Fotoquímicos , Polímeros/química , Polímeros/farmacologia , Animais , Adesão Celular/efeitos dos fármacos , Linhagem Celular , Metacrilatos/química , Camundongos , Nylons/química , Poliestirenos/químicaRESUMO
We present a method to measure the absolute surface resistance of conductive samples at a set of GHz frequencies with superconducting lead stripline resonators at temperatures 1-6 K. The stripline structure can easily be applied for bulk samples and allows direct calculation of the surface resistance without the requirement of additional calibration measurements or sample reference points. We further describe a correction method to reduce experimental background on high-Q resonance modes by exploiting TEM-properties of the external cabling. We then show applications of this method to the reference materials gold, tantalum, and tin, which include the anomalous skin effect and conventional superconductivity. Furthermore, we extract the complex optical conductivity for an all-lead stripline resonator to find a coherence peak and the superconducting gap of lead.