Publications Search Results

Now showing 1 - 10 of 21
  • Publication
    Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces
    ( 2018)
    Aguiar, Kelen R. de
    ;
    ; ;
    Noeske, Paul-Ludwig Michael
    ;
    ;
    Rodrigues-Filho, Ubirajara P.
    The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strong lyattach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane(CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobicPDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile PDMSUr-Dopamine modifier facilitates such functionalization for various substrates such as titanium alloy, steel and ceramic surfaces.
  • Publication
    Photoregulating antifouling and bioadhesion functional coating surface based on spiropyran
    ( 2018)
    Yu, Leixiao
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    Schlaich, Christoph
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    Hou, Yong
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    Zhang, Jianguang
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    Noeske, Paul-Ludwig Michael
    ;
    Haag, Rainer
    Dynamic regulation of the interactions between specific molecules on functional surfaces and biomolecules, for example, proteins or cells, is critical for biosensor and biomedical devices. Herein, we present a spiropyran (SP)‐based light‐responsive surface coating, hPG (hyperbranched polyglycerol)‐SP, to control the adsorption of proteins and adhesion of cells. In the normal state, the SP groups on the coating surface were in hydrophobic ring‐closed form, which promotes the nonspecific protein adsorption and cell adhesion. Under UV irradiation, the grafted SP groups were dynamically isomerized into hydrophilic/zwitterionic merocyanine. Both hydrophilicity and zwitterions support the formation of a hydrated layer and hence the resulting hPG‐MC coatings highly resist protein adsorption and cell adhesion. Moreover, the presented hPG also provided a robust bioinert background to suppress the nonspecific protein adsorption and cells adhesion. Therefore, this functionalized coating exhibited a good photoregulated antifouling behavior. Moreover, the detachment of adsorbed proteins and adhered cells from the coating surface was also realized.
  • Publication
    Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces
    ( 2018)
    Aguiar, Kelen R. de
    ;
    ; ;
    Noeske, Paul-Ludwig Michael
    ;
    ;
    Rodrigues-Filho, Ubirajara P.
    The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strong lyattach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane(CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobicPDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile PDMSUr-Dopamine modifier facilitates such functionalization for various substrates such as titanium alloy, steel and ceramic surfaces.
  • Publication
    Interfactant action of an amphiphilic polymer upon directing graphene oxide layer formation on sapphire substrates
    ( 2017)
    Corrales Ureña, Yendry Regina
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    Cavalcanti, Welchy Leite
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    Soltau, Marko
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    Vollalobos, Karolina
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    Noeske, Paul-Ludwig Michael
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    Quality assured surface pre-treatment may greatly enhance adhesive interactions and, thus, the performance and durability of material joints. This holds true as well for substrates used in coating processes as for adherents introduced into bonding processes. Wet table polymeric wetting agents-shortly called polymeric interfactants-contribute to modifying surfaces and governing the properties of interphases. This is demonstrated for amphiphilic polymers directing the adsorption of graphene oxide(GO) nano-sheets from aqueous dispersion on alumina surfaces. In this contribution, contact angle measurements as well as X-ray photoelectron spectroscopy and scanning force microscopy investigations are applied for the characterization of thin films. GO is adsorbed either from a buffered dispersion on pristine aluminum oxide surfaces or on alumina modified with a few nanometers thin layer of a polymeric interfactant. Laterally extended nanoparticles and GO nano-sheets are preferentially found on interfactant layers whereas on pristine aluminum oxide smaller adsorbates dominate. The driving forces directing the GO attachment are discussed using a phenomenological model based on polymer/substrate interactions governing the sticking probabilities of GO nano-sheets with different sizes.
  • Publication
    Bioinspired universal monolayer coatings by combining concepts from blood protein adsorption and mussel adhesion
    ( 2017)
    Yu, Leixiao
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    Cheng, Chong
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    Ran, Qidi
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    Schlaich, Christoph
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    Noeske, Paul-Ludwig Michael
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    Li, Wenzhong
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    Wai, Qiang
    ;
    Haag, Rainer
    Despite the increasing need for universal polymer coating strategies, only a few approaches have been successfully developed, and most of them are suffering from color, high thickness, or high roughness. In this paper, we present for the first time a universal monolayer coating that is only a few nanometers thick and independent of the composition, size, shape, and structure of the substrate. The coating is based on a bioinspired synthetic amphiphilic block copolymer that combines two concepts from blood protein adsorption and mussel adhesion. This polymer can be rapidly tethered on various substrates including both planar surfaces and nanosystems with high grafting density. The resulting monolayer coatings are, on the one hand, inert to the adsorption of multiple polymer layers and prevent biofouling. On the other hand, they are chemically active for secondary functionalization and provide a new platform for selective material surface modification.
  • Publication
    High-antifouling polymer brush coatings on nonpolar surfaces via adsorption-cross-linking strategy
    ( 2017)
    Lu, Leixiao
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    Hou, Yong
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    Cheng, Chong
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    Schlaich, Christoph
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    Noeske, Paul-Ludwig Michael
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    Wei, Qiang
    ;
    Haag, Rainer
    A new ""adsorption-cross-linking"" technology is presented to generate a highly dense polymer brush coating on various nonpolar substrates, including the most inert and low-energy surfaces of poly(dimethyl siloxane)and poly(tetrafluoroethylene). This prospective surface modification strategy is based on a tailored bifunctional amphiphilic block copolymer with benzophenone units as the hydrophobic anchor/chemical cross-linker and terminal azide groups for in situ postmodification. The resulting polymer brushes exhibited long-term and ultralow protein adsorption and cell adhesion benefiting from the high density and high hydration ability of polyglycerol blocks. The presented antifouling brushes provided a highly stable and robust bioinert background for biospecific adsorption of desired proteins and bacteria after secondary modification with bioactive ligands, e.g., mannose for selective ConA and Escherichia coli binding.
  • Publication
    Investigations of biofilms formed on silica in contact with aqueous formulations containing laccase and maltodextrin
    ( 2016)
    Corrales Ureña, Yendry Regina
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    Vieira Nascimento, Matheus
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    Lisboa-Filho, Paulo Noronha
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    Noeske, Paul-Ludwig Michael
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    The formation of nano-scale biofilms on hydrophilic silica surfaces from aqueous polypeptide/polysaccharide mixtures containing laccase and maltodextrin was investigated in situ with quartz crystal microbalance with dissipation monitoring (QCM-D). Surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), optically stimulated electron emission (OSEE) and atomic force microscopy (AFM) were applied for characterizing the resulting layers obtained after periods varying from a few seconds to several hours of contact between the substrate and the biopolymers formulation. The biofilm formation in contact with the aqueous laccase/maltodextrin suspension was studied at pH level 4.75, under conditions close to the isoelectric point of the enzyme. The few nanometers rough biofilms obtained were composed of a laccase/maltodextrin mixture, and their thickness was observed to steadily increase during 4 h of contact with the aqueous mixture of biopolymers. Remarkably, the still adhesive films obtained after 1 h of contact with aqueous polypeptide/polysaccharide mixture resisted a 30 min rinsing with acetate buffer. The biofilms growing process was monitored using OSEE, due to the effected attenuation of the UV-induced electron emission from the SiO2/Si substrate, which was found to be more pronounced than the attenuation of the photoelectrons from the substrate which contribute to the XPS signals. Layers as thin as 1 nm were detected by the OSEE.
  • Publication
    Surface modification by physical treatments on biomedical grade metals to improve adhesion for bonding hybrid non-isocyanate urethanes
    ( 2016)
    Rossi de Aguiar, Kelen Menezes Flores
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    Maas, J.F.
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    Picon, Carlos Alberto
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    Noeske, Paul-Ludwig Michael
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    ; ;
    Rodrigues Filho, Ubirajara Pereira
    This work aims to improve the adhesion of a hybrid non-isocyanate polydimethylsiloxane urethane (PDMSUr) coating by producing active layers on titanium alloy (Ti6Al4V) and stainless steel (SS316L) applying pulsed Nd:YAG laser and oxygen plasma. The PDMSUr is a hybrid adhesive and, when functionalized with alkoxysilane groups, can bind onto the interfacial hydroxyl groups of a (hydr)oxide/carbonate layer by sol-gel reactions. These reactions are acid catalysed and the silanol groups can bind through Si-O-metal links. The pull-off-strength of such sustainable coatings raised more than 100% for both substrates after the physical treatments, compared with the substrates etched. X-ray Photoelectron Spectroscopy (XPS) of a freshly pre-treated substrate revealed the formation of thin oxide-based reactive layers on the surface of Ti6Al4V and SS316L after the surface treatments. Both physical procedures were efficient to create oxide layers on top of metallic substrates and contributed to the improvement of adhesion strength of PDMSUr on biomedical grade metals.
  • Publication
    Formation and composition of adsorbates on hydrophobic carbon surfaces from aqueous laccase-maltodextrin mixture suspension
    ( 2016)
    Corrales Ureña, Yendry Regina
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    Lisboa-Filhoa, Paulo Noronha
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    Szardenings, MIchael
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    Noeske, Paul-Ludwig Michael
    ;
    A robust procedure for the surface bio-functionalization of carbon surfaces was developed. It consists on the modification of carbon materials in contact with an aqueous suspension of the enzyme laccase from Trametes versicolor and the lyophilization agent maltodextrin, with the pH value adjusted close to the isoelectric point of the enzyme. We report in-situ investigations applying Quartz Crystal Microbalance with Dissipation (QCM-D) for carbon-coated sensor surfaces and, moreover, ex-situ measurements with static contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Scanning Force Microscopy (SFM) for smooth Highly Oriented Pyrolytic Graphite (HOPG) substrates, for contact times between the enzyme formulation and the carbon material surface ranging from 20 s to 24 h. QCM-D studies reveals the formation of rigid layer of biomaterial, a few nanometers thin, which shows a strongly improved wettability of the substrate surface upon contact angle measurements. Following spectroscopic characterization, these layers are composed of mixtures of laccase and maltodextrin. The formation of these adsorbates is attributed to attractive interactions between laccase, the maltodextrin-based lyophilization agent and the hydrophobic carbon surfaces; a short-term contact between the aqueous laccase mixture suspension and HOPG surfaces is shown to merely result in de-wetting patterns influencing the results of contact angle measurements. The new enzyme-based surface modification of carbon-based materials is suggested to be applicable for the improvement of not only the wettability of low energy substrate surfaces with fluid formulations like coatings or adhesives, but also their adhesion in contact with hardened polymers.
  • Publication
    Molecular simulation on carbon dioxide fixation routes towards synthesis of precursors for innovative urethanes
    ( 2015) ;
    Taveira Caleiro, Lucas
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    Rossi de Aguiar, Kelen
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    Joswig, Jan-Ole
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    Pereira Rodrigues Filho, Ubirajara
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    Noeske, Paul-Ludwig Michael
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    ;
    Classical molecular dynamics were carried out in order to obtain insights into proper conditions to perform chemical fixation of carbon dioxide (CO2) with epoxide molecules into cyclic carbonates. Two different molecules containing epoxide groups were investigated: 1,2-Epoxybutane (EB), called linear aliphatic epoxide molecule, and 3-Ethyl-7-oxabicyclo(4.1.0)heptane (EC), called cycloaliphatic epoxide molecule. The reaction systems involving carbon dioxide additionally were catalyzed by tetraethylammonium bromide (TEAB). The dynamics of the molecular groups were studied by taking into account known reaction mechanisms to investigate whether the optimal reaction conditions were observed. Radial distribution functions and self-diffusion coefficients were calculated and revealed that in case of the systems with cycloaliphatic epoxide groups as reagent the CO2 molecules were located far away from the agglomerate formed by the dispersed tetraethylammonium bromide catalyst and epoxide groups (EC), and they do not present enough mobility to overcome the long distances to react. Additionally, it was observed that, in the case of the linear aliphatic epoxide groups (EB), the dynamics of the groups tends to facilitate the reaction mechanisms by presenting a considerable amount of available CO2 molecules in the neighborhood of the epoxy rings. Thus, via the Molecular Dynamics insights, the systems containing linear aliphatic epoxide groups presented a much more accessible condition for the subsequent reaction steps of the carbon dioxide fixation to occur as compared to systems containing cycloaliphatic epoxide groups. The simulation results are in agreement with the experimental findings, which showed via infrared spectroscopy the successful conversion of epoxy rings from linear aliphatic epoxide molecules into five-membered cyclic carbonates after reacting with carbon dioxide.