1,721,014 research outputs found
Precision nanoengineering for functional self-assemblies across length scales
No full textAs nanotechnology continues to push the boundaries across disciplines, there is an increasing need for engineering nanomaterials with atomic-level precision for self-assembly across length scales, i.e., from the nanoscale to the macroscale. Although molecular self-assembly allows atomic precision, extending it beyond certain length scales presents a challenge. Therefore, the attention has turned to size and shape-controlled metal nanoparticles as building blocks for multifunctional colloidal self-assemblies. However, traditionally, metal nanoparticles suffer from polydispersity, uncontrolled aggregation, and inhomogeneous ligand distribution, resulting in heterogeneous end products. In this feature article, I will discuss how virus capsids provide clues for designing subunit-based, precise, efficient, and error-free self-assembly of colloidal molecules. The atomically precise nanoscale proteinic subunits of capsids display rigidity (conformational and structural) and patchy distribution of interacting sites. Recent experimental evidence suggests that atomically precise noble metal nanoclusters display an anisotropic distribution of ligands and patchy ligand bundles. This enables symmetry breaking, consequently offering a facile route for two-dimensional colloidal crystals, bilayers, and elastic monolayer membranes. Furthermore, inter-nanocluster interactions mediated via the ligand functional groups are versatile, offering routes for discrete supracolloidal capsids, composite cages, toroids, and macroscopic hierarchically porous frameworks. Therefore, engineered nanoparticles with atomically precise structures have the potential to overcome the limitations of molecular self-assembly and large colloidal particles. Self-assembly allows the emergence of new optical properties, mechanical strength, photothermal stability, catalytic efficiency, quantum yield, and biological properties. The self-assembled structures allow reproducible optoelectronic properties, mechanical performance, and accurate sensing. More importantly, the intrinsic properties of individual nanoclusters are retained across length scales. The atomically precise nanoparticles offer enormous potential for next-generation functional materials, optoelectronics, precision sensors, and photonic devices.Peer reviewe
Seeing the Supracolloidal Assemblies in 3D: Unraveling High-Resolution Structures Using Electron Tomography
No full textTransmission electron microscopy (TEM) imaging has revolutionized modern materials science, nanotechnology, and structural biology. Its ability to provide information about materials’ structure, composition, and properties at atomic-level resolution has enabled groundbreaking discoveries and the development of innovative materials with precision and accuracy. Electron tomography, single particle reconstruction, and microcrystal electron diffraction techniques have paved the way for the three-dimensional (3D) reconstruction of biological samples, synthetic materials, and hybrid nanostructures at near atomic-level resolution. TEM tomography using a series of two-dimensional (2D) projections has been used extensively in biological science, but in recent years it has become an important method in synthetic nanomaterials and soft matter research. TEM tomography offers unprecedented morphological details of 3D objects, internal structures, packing patterns, growth mechanisms, and self-assembly pathways of self-assembled colloidal systems. It complements other analytical tools, including small-angle X-ray scattering, and provides valuable data for computational simulations for predictive design and reverse engineering of nanomaterials with the desired structure and properties. In this perspective, I will discuss the importance of TEM tomography in the structural understanding and engineering of self-assembled nanostructures with specific emphasis on colloidal capsids, composite cages, biohybrid superlattices with complex geometries, polymer assemblies, and self-assembled protein-based superstructures.Peer reviewe
Luminescent gold nanoclusters for bioimaging applications
No full textLuminescent nanomaterials have emerged as attractive candidates for sensing, catalysis and bioimaging applications in recent years. For practical use in bioimaging, nanomaterials with high photoluminescence, quantum yield, photostability and large Stokes shifts are needed. While offering high photoluminescence and quantum yield, semiconductor quantum dots suffer from toxicity and are susceptible to oxidation. In this context, atomically precise gold nanoclusters protected by thiol monolayers have emerged as a new class of luminescent nanomaterials. Low toxicity, bioavailability, photostability as well as tunable size, composition, and optoelectronic properties make them suitable for bioimaging and biosensing applications. In this review, an overview of the sensing of pathogens, and of in vitro and in vivo bioimaging using luminescent gold nanoclusters along with the limitations with selected examples are discussed.Peer reviewe
ChemInform Abstract: Unlocking the Potential of Bile Acids in Synthesis, Supramolecular/Materials Chemistry and Nanoscience
No full textSolid state NMR studies of gels derived from low molecular mass gelators
No full textSince its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples.Peer reviewe
Electron Tomography of Whole Mounts
No full textRapid progress in the instrumentation, sample preparation methods, and computational power have triggered a revolution in electron tomography methods. Herein, we adapted a straightforward freeze-drying method using tert-butanol for electron tomography of whole mount colloids. This approach will overcome some of the common artifacts in electron microscopy specimen preparation.Peer reviewe
Fabrication of biopolymer-based optical fibers for short-distance applications
No full textThe extraordinary ability of optical fibers to control and propagate light has sparked a revolution in modern high-capacity communication networks. Beyond data networks, the state-of-the-art glass and plastic optical fibers have also been studied for numerous biomedical applications, including laser surgery, optogenetics, phototherapy and biosensing. However, commercial optical fibers have several disadvantages due to their brittle nature, non-biocompatibility and non-degradability necessary for biomedical applications. Therefore, there is a need to develop optical fibers from biopolymers that are biocompatible and biodegradable. Because of their biocompatible nature, biopolymer optical fibers can remain in the human body for a long time without iliciting an immune response. Because of their biodegradable nature, surgical removal after their use is not necessary.
This thesis aimed to identify critical parameters to fabricate and characterize biopolymer optical fibers using environmentally benign fiber spinning methods. Three types of biopolymers, viz., alginate, carboxymethylcellulose and methylcellulose, were used for fiber preparation. The hydrogels prepared from the biopolymers were used for fiber extrusion using either wet-spinning or dry-jet wet spinning. The fibers were ionically cross-linked using metal ions under ambient conditions. The resulting fibers were then optically characterized for their waveguiding properties using the cutback method. The optical characterization suggests that the alginates-based fibers are not suitable for waveguiding due to very little light propagation. Interestingly, carboxymethylcellulose fibers displayed very low optical loss. This is on par or better than biopolymer optical fibers reported in the literature. The results encourage to explore further the potential of naturally abundant and renewable biomaterials for short-distance optical fibers
Hydrogen Bonding Directed Colloidal Self-Assembly of Nanoparticles into 2D Crystals, Capsids, and Supracolloidal Assemblies
No full text| openaire: EC/FP7/291364/EU//MIMEFUNSelf-assembly of colloidal building blocks, like metal nanoparticles, is a rapidly progressing research area toward new functional materials. However, in-depth control of the colloidal self-assembly and especially hierarchical self-assembly is difficult due to challenges in controlling the size dispersities, shape/morphology, directionalities, and aggregation tendencies. Using either polydispersed or narrow-size dispersed nanoparticles, considerable progress has been achieved over the past few years. However, absolutely monodisperse nanoparticles could allow new options for rational designs of self-assemblies. Therein, atomically precise monolayer protected nanoclusters (d < 3 nm) have recently been synthesized with well-defined metal cores and surface ligands. Their dispersion behavior is commonly tuned by surfactant-like ligands. Beyond that, this study deals with approaches based on ligand-driven supramolecular interactions and colloidal monodispersity until atomic precision to tune the colloidal self-assembly and hierarchy from nanoscale to mesoscopic scale. Therein colloidal packing to self-assembled 2D crystals and closed virus capsid-inspired shells provide relevant research goals due to ever increasing potential of 2D materials and encapsulation. This study addresses the hydrogen bonding (H-bonding) directed self-assembly of atomically precise gold and silver nanoparticles and narrow size dispersed cobalt nanoparticles to free-standing 2D colloidal nanosheets, nanowire assemblies, capsid-like colloidal closed shells, as well as higher order structures.Peer reviewe
Ferritiini fuusioproteiinien in vivo itsejärjestymismekanismit
No full textFerritins are spherical iron storage proteins and widely studied protein building blocks for many biomaterial applications. These protein particles are known to assemble into two-dimensional sheets into hexagonal plane. However, a ferritin fusion protein GFP-resilin-ferritin produced at VTT Ltd formed unprecedented spear-like supramolecularly self-assembled structures. The aim of this thesis was to gain molecular level insights into its self-assembly mechanisms.
In this thesis, five fusion protein constructs were produced and their in vivo supramolecular assemblies were examined. Trichoderma reesei strain producing GFP-resilin-ferritin was cultivated and visualized with confocal microscopy for studying in vivo self-assembly mechanisms. Purification procedures including sonication and homogenization by mixer mill were attempted. New constructs expressing ferritin and HFBI-ferritin were designed, cloned and agroinfiltrated to Nicotiana benthamiana tobacco plants. Also, resilin fusion proteins ZERA-resilin and GFP-resilin-HFBI were expressed N. benthamiana. These four fusion proteins were purified from ground leaves by sucrose gradient ultracentrifugation. The in vivo self-assembly mechanisms of the fusion proteins were studied by confocal microscopy, whereas purified fusion proteins were investigated also by conventional and cryogenic transmission electron microscopy (Cryo-TEM) imaging.
The new ferritin construct self-assembled into long thin spears similar to those of GFP-resilin-ferritin, thus indicating that ferritin would drive the spear-like self-assembly. Resilin fusion proteins ZERA-resilin and GFP-resilin-HFBI formed only spherical PBs, so it is suggested that resilin does not have an impact to spear-like assembly of GFP-resilin-ferritin. HFBI-ferritin formed spherical PB-like structures, which is likely due to PB-inducing fusion protein partner HFBI. Purified ferritin fusion proteins did not show similar self-assembled structures when observed with TEM. These observations provide insights for recombinant protein self-assembly research.Ferritiinit ovat raudan varastoproteiineja ja laajalti tutkittuja proteiinirakennuspaloja useita biomateriaalisovelluksia varten. Näiden proteiinipartikkelien tiedetään järjestyvän kaksiulotteisiksi kerroksiksi kuusisivuiseen tasoon. VTT Ltd:llä tuotetun ferritiini fuusioproteiinin GFP-resiliini-ferritiinin havaittiin kuitenkin muodostavan ennennäkemättömiä supramolekulaarisesti itsejärjestyneitä tikkumaisia rakenteita. Tämän diplomityön tavoitteena oli saada syvempi molekyylitason käsitys tämän fuusioproteiinin itsejärjestymismekanismeista.
Tässä työssä tuotettiin viisi fuusioproteiinikonstruktia ja niiden in vivo supramolekulaarisia järjestymisiä tutkittiin. In vivo itsejärjestymismekanismien tutkimista varten GFP-resiliini-ferritiiniä tuotettiin Trichoderma reesei sienessä ja tutkittiin konfokaalimikroskoopilla. Fuusioproteiinien puhdistusta yritettiin sonikaatiolla ja homogenoimalla niitä sekoitusmyllyssä. Uudet konstruktit, ferritiini ja HFBI-ferritiini, kloonattiin ja agroinfiltroitiin Nicotiana benthamiana tupakkakasveihin. Resiliini fuusioproteiinit ZERA-resiliini ja GFP-resiliini-HFBI tuotettiin N. benthamianassa. Nämä fuusioproteiinit puhdistettiin jauhetuista tupakan lehdistä sakkaroosigradientti ultrasentrifugaatiolla. Näiden in vivo itsejärjestymismekanismeja tutkittiin konfokaalimikroskoopilla, kun taas puhdistettuja fuusioproteiineja tutkittiin myös konventionaalisella ja kryogeenisellä läpivalaisuelektronimikroskoopeilla.
Uusi ferritiini konstrukti itsejärjestyi samankaltaisiksi pitkiksi ja ohuiksi tikuiksi kuin GFP-resiliini-ferritiinin tapauksessa havaittiin. Tämä osoittaa, että ferritiini voisi olla ajava tekijä tässä itsejärjestymisessä. Resiliini fuusioproteiinit ZERA-resiliini ja GFP-resiliini-HFBI itsejärjestyivät pallomaisiksi proteiinijyväsiksi, joten voidaan todeta, että resiliinillä ei ole vaikutusta GFP-resiliini-ferritiinin tikkumaiseen rakenteeseen. HFBI-ferritiini muodosti pallomaisia proteiinijyväsrakenteita, minkä oletetaan johtuvan proteiinijyväseksi indusoivasta HFBI fuusioproteiinipartnerista. Puhdistetut ferritiini fuusioproteiinit eivät itsejärjestyneet samalla tavalla, kun niitä tutkittiin läpivalaisuelektronimikroskoopilla. Nämä havainnot tarjoavat syvemmän käsityksen rekombinanttiproteiinien itsejärjestymismekanismeihin
- …
