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- ItemOptimizing the Geometry of Photoacoustically Active Gold Nanoparticles for Biomedical Imaging(Washington, DC : ACS, 2020) García-Álvarez, Rafaela; Chen, Lisa; Nedilko, Alexander; Sánchez-Iglesias, Ana; Rix, Anne; Lederle, Wiltrud; Pathak, Vertika; Lammers, Twan; von Plessen, Gero; Kostarelos, Kostas; Liz-Marzán, Luis M.; Kuehne, Alexander J.C.; Chigrin, Dmitry N.Photoacoustics is an upcoming modality for biomedical imaging, which promises minimal invasiveness at high penetration depths of several centimeters. For superior photoacoustic contrast, imaging probes with high photothermal conversion efficiency are required. Gold nanoparticles are among the best performing photoacoustic imaging probes. However, the geometry and size of the nanoparticles determine their photothermal efficiency. We present a systematic theoretical analysis to determine the optimum nanoparticle geometry with respect to photoacoustic efficiency in the near-infrared spectral range, for superior photoacoustic contrast. Theoretical predictions are illustrated by experimental results for two of the most promising nanoparticle geometries, namely, high aspect ratio gold nanorods and gold nanostars. Copyright © 2020 American Chemical Society.
- ItemAnti-Stokes Stress Sensing: Mechanochemical Activation of Triplet-Triplet Annihilation Photon Upconversion(Weinheim : Wiley-VCH, 2019) Yildiz, Deniz; Baumann, Christoph; Mikosch, Annabel; Kuehne, Alexander J.C.; Herrmann, Andreas; Göstl, RobertThe development of methods to detect damage in macromolecular materials is of paramount importance to understand their mechanical failure and the structure–property relationships of polymers. Mechanofluorophores are useful and sensitive molecular motifs for this purpose. However, to date, tailoring of their optical properties remains challenging and correlating emission intensity to force induced material damage and the respective events on the molecular level is complicated by intrinsic limitations of fluorescence and its detection techniques. Now, this is tackled by developing the first stress-sensing motif that relies on photon upconversion. By combining the Diels–Alder adduct of a π-extended anthracene with the porphyrin-based triplet sensitizer PtOEP in polymers, triplet–triplet annihilation photon upconversion of green to blue light is mechanochemically activated in solution as well as in the solid state. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemNarrow Stimulated Resonance Raman Scattering and WGM Lasing in Small Conjugated Polymer Particles for Live Cell Tagging and Tracking(Weinheim : Wiley-VCH, 2020) Haehnle, Bastian; Lamla, Markus; Sparrer, Konstantin M.J.; Gather, Malte C.; Kuehne, Alexander J.C.Conjugated polymer particles are brightly fluorescing and stable materials for live cell imaging. Combination of conjugated polymers with a whispering gallery mode (WGM) resonator allows laser emission from microscale particles. Once internalized by cells, the mode pattern of the laser emission can be used for tagging and tracking, as each laser spectrum represents a bar code to identify individual cells. However, currently these particle systems are limited by their large size, which might interfere with cellular functions. Here, stimulated resonance Raman scattering (SRRS) in small conjugated polymer microparticles is presented as a new method for generating narrow emission as an alternative to WGM-based laser emission. This opens up spectral range for multiplexing optical readout and multicolor imaging of live cells. The synthesis of monodisperse micrometer-sized poly(fluorene-co-divinylbenzene) particles is discussed and their WGM and SRRS emission are characterized. Finally, how these particles and their emission can be employed in live cell imaging and tagging is showcased. © 2020 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
- ItemCroconaine-Based Polymer Particles as Contrast Agents for Photoacoustic Imaging(Weinheim : Wiley-VCH, 2020) Jansen, Felicitas; Lamla, Markus; Mauthe, Diana; Fischer, Stephan; Barth, Holger; Kuehne, Alexander J.C.In the development and optimization of imaging methods, photoacoustic imaging (PAI) has become a powerful tool for preclinical biomedical diagnosis and detection of cancer. PAI probes can improve contrast and help identify pathogenic tissue. Such contrast agents must meet several requirements: they need to be biocompatible, and absorb strongly in the near-infrared (NIR) range, while relaxing the photoexcited state thermally and not radiatively. In this work, polymer nanoparticles are produced with croconaine as a monomer unit. Small molecular croconaine dyes are known to act as efficient pigments, which do not show photoluminescence. Here, for the first time croconaine copolymer nanoparticles are produced from croconic acid and a range of aromatic diamines. Following a dispersion polymerization protocol, this approach yields monodisperse particles of adjustable size. All synthesized polymers exhibit broad absorption within the NIR spectrum and therefore represent suitable candidates as contrast agents for PAI. The optical properties of these polymer particles are discussed with respect to the relation between particle size and outstanding photoacoustic performance. Biocompatibility of the polymer particles is demonstrated in cell viability experiments. © The Authors. Published by Wiley-VCH GmbH
- ItemConjugated Polymer Nanoparticles toward In Vivo Theranostics – Focus on Targeting, Imaging, Therapy, and the Importance of Clearance(Weinheim : Wiley-VCH, 2017) Kuehne, Alexander J.C.Conjugated polymer nanoparticles are highly fluorescent colloids with tunable emission colors ranging from the visible deep into the near infrared spectrum. Conjugated polymer nanoparticles are easy to prepare, tunable in their size, and virtually nonbleachable. Conjugated polymer particles can also be designed to give off heat upon irradiation. All these properties make conjugated polymer particles ideal materials for biomedical fluorescence and photoacoustic imaging as well as for theranostic applications. Here, different examples of surface functionalization to attach pathological homing devices, imaging modalities, as well as the emerging possibilities for therapeutic measures are discussed. Furthermore, clearance of the particles is considered, which is important to ultimately apply the materials for in vivo theranostics. Due to the conjugated backbone of the conjugated polymers, established degradation strategies, as known from hydrophilic nonconjugated polymer carriers, cannot be applied. Bioinspired strategies and potential pathways for degradation and clearance via structural changes upon triggers such as pH, oxidation, and temperature are also discussed in this progress report. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCompartmentalized Jet Polymerization as a High-Resolution Process to Continuously Produce Anisometric Microgel Rods with Adjustable Size and Stiffness(Weinheim : Wiley-VCH, 2019) Krüger, Andreas J.D.; Bakirman, Onur; Guerzoni, Luis P.B.; Jans, Alexander; Gehlen, David B.; Rommel, Dirk; Haraszti, Tamás; Kuehne, Alexander J.C.; De Laporte, LauraIn the past decade, anisometric rod-shaped microgels have attracted growing interest in the materials-design and tissue-engineering communities. Rod-shaped microgels exhibit outstanding potential as versatile building blocks for 3D hydrogels, where they introduce macroscopic anisometry, porosity, or functionality for structural guidance in biomaterials. Various fabrication methods have been established to produce such shape-controlled elements. However, continuous high-throughput production of rod-shaped microgels with simultaneous control over stiffness, size, and aspect ratio still presents a major challenge. A novel microfluidic setup is presented for the continuous production of rod-shaped microgels from microfluidic plug flow and jets. This system overcomes the current limitations of established production methods for rod-shaped microgels. Here, an on-chip gelation setup enables fabrication of soft microgel rods with high aspect ratios, tunable stiffness, and diameters significantly smaller than the channel diameter. This is realized by exposing jets of a microgel precursor to a high intensity light source, operated at specific pulse sequences and frequencies to induce ultra-fast photopolymerization, while a change in flow rates or pulse duration enables variation of the aspect ratio. The microgels can assemble into 3D structures and function as support for cell culture and tissue engineering. © 2019 DWI – Leibniz Institute for Interactive Materials. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemMultimodal and multiscale optical imaging of nanomedicine delivery across the blood-brain barrier upon sonopermeation(Wyoming, NSW : Ivyspring, 2020) May, Jan-Niklas; Golombek, Susanne K.; Baues, Maike; Dasgupta, Anshuman; Drude, Natascha; Rix, Anne; Rommel, Dirk; Stillfried, Saskia von; Appold, Lia; Pola, Robert; Pechar, Michal; van Bloois, Louis; Storm, Gert; Kuehne, Alexander J.C.; Gremse, Felix; Theek, Benjamin; Kiessling, Fabian; Lammers, TwanRationale: The blood-brain barrier (BBB) is a major obstacle for drug delivery to the brain. Sonopermeation, which relies on the combination of ultrasound and microbubbles, has emerged as a powerful tool to permeate the BBB, enabling the extravasation of drugs and drug delivery systems (DDS) to and into the central nervous system (CNS). When aiming to improve the treatment of high medical need brain disorders, it is important to systematically study nanomedicine translocation across the sonopermeated BBB. To this end, we here employed multimodal and multiscale optical imaging to investigate the impact of DDS size on brain accumulation, extravasation and penetration upon sonopermeation. Methods: Two prototypic DDS, i.e. 10 nm-sized pHPMA polymers and 100 nm-sized PEGylated liposomes, were labeled with fluorophores and intravenously injected in healthy CD-1 nude mice. Upon sonopermeation, computed tomography-fluorescence molecular tomography, fluorescence reflectance imaging, fluorescence microscopy, confocal microscopy and stimulated emission depletion nanoscopy were used to study the effect of DDS size on their translocation across the BBB. Results: Sonopermeation treatment enabled safe and efficient opening of the BBB, which was confirmed by staining extravasated endogenous IgG. No micro-hemorrhages, edema and necrosis were detected in H&E stainings. Multimodal and multiscale optical imaging showed that sonopermeation promoted the accumulation of nanocarriers in mouse brains, and that 10 nm-sized polymeric DDS accumulated more strongly and penetrated deeper into the brain than 100 nm-sized liposomes. Conclusions: BBB opening via sonopermeation enables safe and efficient delivery of nanomedicine formulations to and into the brain. When looking at accumulation and penetration (and when neglecting issues such as drug loading capacity and therapeutic efficacy) smaller-sized DDS are found to be more suitable for drug delivery across the BBB than larger-sized DDS. These findings are valuable for better understanding and further developing nanomedicine-based strategies for the treatment of CNS disorders. © The author(s).