@article{AkarsuGrobeNowaczyketal.2021, author = {Akarsu, Pinar and Grobe, Richard and Nowaczyk, Julius and Hartlieb, Matthias and Reinicke, Stefan and B{\"o}ker, Alexander and Sperling, Marcel and Reifarth, Martin}, title = {Solid-phase microcontact printing for precise patterning of rough surfaces}, series = {ACS applied polymer materials}, volume = {3}, journal = {ACS applied polymer materials}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {2637-6105}, doi = {10.1021/acsapm.1c00024}, pages = {2420 -- 2431}, year = {2021}, abstract = {We present a microcontact printing (mu CP) routine suitable to introduce defined (sub-) microscale patterns on surface substrates exhibiting a high capillary activity and receptive to a silane-based chemistry. This is achieved by transferring functional trivalent alkoxysilanes, such as (3-aminopropyl)-triethoxysilane (APTES) as a low-molecular weight ink via reversible covalent attachment to polymer brushes grafted from elastomeric polydimethylsiloxane (PDMS) stamps. The brushes consist of poly{N-[tris(hydroxymethyl)-methyl]acrylamide} (PTrisAAm) synthesized by reversible addition-fragmentation chain-transfer (RAFT)-polymerization and used for immobilization of the alkoxysilane-based ink by substituting the alkoxy moieties with polymer-bound hydroxyl groups. Upon physical contact of the silane-carrying polymers with surfaces, the conjugated silane transfers to the substrate, thus completely suppressing ink-flow and, in turn, maximizing printing accuracy even for otherwise not addressable substrate topographies. We provide a concisely conducted investigation on polymer brush formation using atomic force microscopy (AFM) and ellipsometry as well as ink immobilization utilizing two-dimensional proton nuclear Overhauser enhancement spectroscopy (H-1-H-1-NOESY-NMR). We analyze the mu CP process by printing onto Si-wafers and show how even distinctively rough surfaces can be addressed, which otherwise represent particularly challenging substrates.}, language = {en} } @inproceedings{Boeker2019, author = {B{\"o}ker, Alexander}, title = {Programmable soft matter: From active membranes to self-replication}, series = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, volume = {257}, booktitle = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, publisher = {American Chemical Society}, address = {Washington}, issn = {0065-7727}, pages = {1}, year = {2019}, language = {en} } @article{CharanGlebeAnandetal.2017, author = {Charan, Himanshu and Glebe, Ulrich and Anand, Deepak and Kinzel, Julia and Zhu, Leilei and Bocola, Marco and Garakani, Tayebeh Mirzaei and Schwaneberg, Ulrich and B{\"o}ker, Alexander}, title = {Nano-thin walled micro-compartments from transmembrane protein-polymer conjugates}, series = {Soft matter}, volume = {13}, journal = {Soft matter}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c6sm02520j}, pages = {2866 -- 2875}, year = {2017}, abstract = {The high interfacial activity of protein-polymer conjugates has inspired their use as stabilizers for Pickering emulsions, resulting in many interesting applications such as synthesis of templated micro-compartments and protocells or vehicles for drug and gene delivery. In this study we report, for the first time, the stabilization of Pickering emulsions with conjugates of a genetically modified transmembrane protein, ferric hydroxamate uptake protein component A (FhuA). The lysine residues of FhuA with open pore (FhuA Delta CVFtev) were modified to attach an initiator and consequently controlled radical polymerization (CRP) carried out via the grafting-from technique. The resulting conjugates of FhuA Delta CVFtev with poly(N-isopropylacrylamide) (PNIPAAm) and poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA), the so-called building blocks based on transmembrane proteins (BBTP), have been shown to engender larger structures. The properties such as pH-responsivity, temperature-responsivity and interfacial activity of the BBTP were analyzed using UV-Vis spectrophotometry and pendant drop tensiometry. The BBTP were then utilized for the synthesis of highly stable Pickering emulsions, which could remain non-coalesced for well over a month. A new UV-crosslinkable monomer was synthesized and copolymerized with NIPAAm from the protein. The emulsion droplets, upon crosslinking of polymer chains, yielded micro-compartments. Fluorescence microscopy proved that these compartments are of micrometer scale, while cryo-scanning electron microscopy and scanning force microscopy analysis yielded a thickness in the range of 11.1 +/- 0.6 to 38.0 +/- 18.2 nm for the stabilizing layer of the conjugates. Such micro-compartments would prove to be beneficial in drug delivery applications, owing to the possibility of using the channel of the transmembrane protein as a gate and the smart polymer chains as trigger switches to tune the behavior of the capsules.}, language = {en} } @article{CharanKinzelGlebeetal.2016, author = {Charan, Himanshu and Kinzel, Julia and Glebe, Ulrich and Anand, Deepak and Garakani, Tayebeh Mirzaei and Zhu, Leilei and Bocola, Marco and Schwaneberg, Ulrich and B{\"o}ker, Alexander}, title = {Grafting PNIPAAm from beta-barrel shaped transmembrane nanopores}, series = {Biomaterials : biomaterials reviews online}, volume = {107}, journal = {Biomaterials : biomaterials reviews online}, publisher = {Elsevier}, address = {Oxford}, issn = {0142-9612}, doi = {10.1016/j.biomaterials.2016.08.033}, pages = {115 -- 123}, year = {2016}, abstract = {The research on protein-polymer conjugates by grafting from the surface of proteins has gained significant interest in the last decade. While there are many studies with globular proteins, membrane proteins have remained untouched to the best of our knowledge. In this study, we established the conjugate formation with a class of transmembrane proteins and grow polymer chains from the ferric hydroxamate uptake protein component A (FhuA; a beta-barrel transmembrane protein of Escherichia coli). As the lysine residues of naturally occurring FhuA are distributed over the whole protein, FhuA was reengineered to have up to 11 lysines, distributed symmetrically in a rim on the membrane exposed side (outside) of the protein channel and exclusively above the hydrophobic region. Reengineering of FhuA ensures a polymer growth only on the outside of the beta-barrel and prevents blockage of the channel as a result of the polymerization. A water-soluble initiator for controlled radical polymerization (CRP) was consecutively linked to the lysine residues of FhuA and N-isopropylacrylamide (NIPAAm) polymerized under copper mediated CRP conditions. The conjugate formation was analyzed by using MALDI-ToF mass spectrometry, SDS-PAGE, circular dichroism spectroscopy, analytical ultracentrifugation, dynamic light scattering, transmission electron microscopy and size exclusion chromatography. Such conjugates combine the specific functions of the transmembrane proteins, like maintaining membrane potential gradients or translocation of substrates with the unique properties of synthetic polymers such as temperature and pH stimuli handles. FhuA-PNIPAAm conjugates will serve as functional nanosized building blocks for applications in targeted drug delivery, self-assembly systems, functional membranes and transmembrane protein gated nanoreactors. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @article{DaiMateGlebeetal.2018, author = {Dai, Xiaolin and Mate, Diana M. and Glebe, Ulrich and Garakani, Tayebeh Mirzaei and K{\"o}rner, Andrea and Schwaneberg, Ulrich and B{\"o}ker, Alexander}, title = {Sortase-mediated ligation of purely artificial building blocks}, series = {Polymers}, volume = {10}, journal = {Polymers}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, doi = {10.3390/polym10020151}, pages = {13}, year = {2018}, abstract = {Sortase A (SrtA) from Staphylococcus aureus has been often used for ligating a protein with other natural or synthetic compounds in recent years. Here we show that SrtA-mediated ligation (SML) is universally applicable for the linkage of two purely artificial building blocks. Silica nanoparticles (NPs), poly(ethylene glycol) and poly(N-isopropyl acrylamide) are chosen as synthetic building blocks. As a proof of concept, NP-polymer, NP-NP, and polymer-polymer structures are formed by SrtA catalysis. Therefore, the building blocks are equipped with the recognition sequence needed for SrtA reaction-the conserved peptide LPETG-and a pentaglycine motif. The successful formation of the reaction products is shown by means of transmission electron microscopy (TEM), matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS), and dynamic light scattering (DLS). The sortase catalyzed linkage of artificial building blocks sets the stage for the development of a new approach to link synthetic structures in cases where their synthesis by established chemical methods is complicated.}, language = {en} } @article{DoeringGrigorievTapioetal.2022, author = {Doering, Ulrike and Grigoriev, Dmitry and Tapio, Kosti and Bald, Ilko and B{\"o}ker, Alexander}, title = {Synthesis of nanostructured protein-mineral-microcapsules by sonication}, series = {Soft matter}, volume = {18}, journal = {Soft matter}, number = {13}, publisher = {Royal Society of Chemistry}, address = {London}, issn = {1744-6848}, doi = {10.1039/d1sm01638e}, pages = {2558 -- 2568}, year = {2022}, abstract = {We propose a simple and eco-friendly method for the formation of composite protein-mineral-microcapsules induced by ultrasound treatment. Protein- and nanoparticle-stabilized oil-in-water (O/W) emulsions loaded with different oils are prepared using high-intensity ultrasound. The formation of thin composite mineral proteinaceous shells is realized with various types of nanoparticles, which are pre-modified with Bovine Serum Albumin (BSA) and subsequently characterized by EDX, TGA, zeta potential measurements and Raman spectroscopy. Cryo-SEM and EDX mapping visualizations show the homogeneous distribution of the densely packed nanoparticles in the capsule shell. In contrast to the results reported in our previous paper,(1) the shell of those nanostructured composite microcapsules is not cross-linked by the intermolecular disulfide bonds between BSA molecules. Instead, a Pickering-Emulsion formation takes place because of the amphiphilicity-driven spontaneous attachment of the BSA-modified nanoparticles at the oil/water interface. Using colloidal particles for the formation of the shell of the microcapsules, in our case silica, hydroxyapatite and calcium carbonate nanoparticles, is promising for the creation of new functional materials. The nanoparticulate building blocks of the composite shell with different chemical, physical or morphological properties can contribute to additional, sometimes even multiple, features of the resulting capsules. Microcapsules with shells of densely packed nanoparticles could find interesting applications in pharmaceutical science, cosmetics or in food technology.}, language = {en} } @article{DoeringGrigorievTapioetal.2021, author = {Doering, Ulrike and Grigoriev, Dmitry and Tapio, Kosti and Rosencrantz, Sophia and Rosencrantz, Ruben R. and Bald, Ilko and B{\"o}ker, Alexander}, title = {About the mechanism of ultrasonically induced protein capsule formation}, series = {RSC Advances : an international journal to further the chemical sciences / Royal Society of Chemistry}, volume = {11}, journal = {RSC Advances : an international journal to further the chemical sciences / Royal Society of Chemistry}, number = {27}, publisher = {RSC Publishing}, address = {London}, issn = {2046-2069}, doi = {10.1039/d0ra08100k}, pages = {16152 -- 16157}, year = {2021}, abstract = {In this paper, we propose a consistent mechanism of protein microcapsule formation upon ultrasound treatment. Aqueous suspensions of bovine serum albumin (BSA) microcapsules filled with toluene are prepared by use of high-intensity ultrasound following a reported method. Stabilization of the oil-in-water emulsion by the adsorption of the protein molecules at the interface of the emulsion droplets is accompanied by the creation of the cross-linked capsule shell due to formation of intermolecular disulfide bonds caused by highly reactive species like superoxide radicals generated sonochemically. The evidence for this mechanism, which until now remained elusive and was not proven properly, is presented based on experimental data from SDS-PAGE, Raman spectroscopy and dynamic light scattering.}, language = {en} } @article{GarakaniLiuGlebeetal.2019, author = {Garakani, Tayebeh Mirzaei and Liu, Zhanzhi and Glebe, Ulrich and Gehrmann, Julia and Lazar, Jaroslav and Mertens, Marie Anna Stephanie and M{\"o}ller, Mieke and Hamzelui, Niloofar and Zhu, Leilei and Schnakenberg, Uwe and B{\"o}ker, Alexander and Schwaneberg, Ulrich}, title = {In Situ Monitoring of Membrane Protein Insertion into Block Copolymer Vesicle Membranes and Their Spreading via Potential-Assisted Approach}, series = {ACS applied materials \& interfaces}, volume = {11}, journal = {ACS applied materials \& interfaces}, number = {32}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.9b09302}, pages = {29276 -- 29289}, year = {2019}, abstract = {Synthosomes are polymer vesicles with trans membrane proteins incorporated into block copolymer membranes. They have been used for selective transport in or out of the vesicles as well as catalysis inside the compartments. However, both the insertion process of the membrane protein, forming nanopores, and the spreading of the vesicles on planar substrates to form solid-supported biomimetic membranes have been rarely studied yet. Herein, we address these two points and, first, shed light on the real-time monitoring of protein insertion via isothermal titration calorimetry. Second, the spreading process on different solid supports, namely, SiO2, glass, and gold, via different techniques like spin- and dip-coating as well as a completely new approach of potential-assisted spreading on gold surfaces was studied. While inhomogeneous layers occur via traditional methods, our proposed potential-assisted strategy to induce adsorption of positively charged vesicles by applying negative potential on the electrode leads to remarkable vesicle spreading and their further fusion to form more homogeneous planar copolymer films on gold. The polymer vesicles in our study are formed from amphiphilic copolymers poly(2-methyl oxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyl oxazoline) (PMOXA-b-PDMS-b-PMOXA). Engineered variants of the transmembrane protein ferric hydroxamate uptake protein component A (FhuA), one of the largest beta-barrel channel proteins, are used as model nanopores. The incorporation of FhuA Delta 1-160 is shown to facilitate the vesicle spreading process further. Moreover, high accessibility of cysteine inside the channel was proven by linkage of a fluorescent dye inside the engineered variant FhuA Delta CVFtev and hence preserved functionality of the channels after spreading. The porosity and functionality of the spread synthosomes on the gold plates have been examined by studying the passive ion transport response in the presence of Li+ and ClO4- ions and electrochemical impedance spectroscopy analysis. Our approach to form solid-supported biomimetic membranes via the potential-assisted strategy could be important for the development of new (bio-) sensors and membranes.}, language = {en} } @article{HiltlBoeker2016, author = {Hiltl, Stephanie and B{\"o}ker, Alexander}, title = {Wetting Phenomena on (Gradient) Wrinkle Substrates}, series = {Langmuir}, volume = {32}, journal = {Langmuir}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.6b02364}, pages = {8882 -- 8888}, year = {2016}, abstract = {We characterize the wetting behavior of nano structured wrinkle and gradient wrinkle substrates. Different contact angles on both sides of a water droplet after deposition on a gradient sample induce the self-propelled motion of the liquid toward smaller wrinkle dimensions. The droplet motion is self-limited by the contact angles balancing out. Because of the correlation between droplet motion and contact angles, we investigate the wetting behavior of wrinkle substrates with constant dimensions (wavelengths of 400-1200 nm). Contact angles of water droplets on those substrates increase with increasing dimensions of the underlying substrate. The results are independent of the two measurement directions, parallel and perpendicular to the longitudinal axis of the nanostructure. The presented findings may be considered for designing microfluidic or related devices and initiate ideas for the development of further wrinkle applications.}, language = {en} } @article{JohnZimmermannBoeker2018, author = {John, Daniela and Zimmermann, Marc and B{\"o}ker, Alexander}, title = {Generation of 3-dimensional multi-patches on silica particles via printing with wrinkled stamps}, series = {Soft matter}, volume = {14}, journal = {Soft matter}, number = {16}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c8sm00224j}, pages = {3057 -- 3062}, year = {2018}, abstract = {A simple route towards patchy particles with anisotropic patches with respect to a different functionality and directionality is presented. This method is based on microcontact printing of positively charged polyethylenimine (PEI) on silica particles using wrinkled stamps. Due to the wrinkled surface, the number of patches on the particles as well as the distance between two patches can be controlled.}, language = {en} }