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Rapid progress in algal biotechnology has triggered a growing interest in hydrogel-encapsulated microalgal cultivation, especially for the engineering of functional photosynthetic materials and biomass production. An overlooked characteristic of gel-encapsulated cultures is the emergence of cell aggregates, which are the result of the mechanical confinement of the cells. Such aggregates have a dramatic effect on the light management of gel-encapsulated photobioreactors and hence strongly affect the photosynthetic outcome. To evaluate such an effect, we experimentally studied the optical response of hydrogels containing algal aggregates and developed optical simulations to study the resultant light intensity profiles. The simulations are validated experimentally via transmittance measurements using an integrating sphere and aggregate volume analysis with confocal microscopy. Specifically, the heterogeneous distribution of cell aggregates in a hydrogel matrix can increase light penetration while alleviating photoinhibition more effectively than in a flat biofilm. Finally, we demonstrate that light harvesting efficiency can be further enhanced with the introduction of scattering particles within the hydrogel matrix, leading to a fourfold increase in biomass growth. Our study, therefore, highlights a strategy for the design of spatially efficient photosynthetic living materials that have important implications for the engineering of future algal cultivation systems.
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Hidrogéis , Luz , Microalgas , Fotossíntese , Hidrogéis/química , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Biomassa , FotobiorreatoresRESUMO
Structural color is an optical phenomenon resulting from light interacting with nanostructured materials. Although structural color (SC) is widespread in the tree of life, the underlying genetics and genomics are not well understood. Here, we collected and sequenced a set of 87 structurally colored bacterial isolates and 30 related strains lacking SC. Optical analysis of colonies indicated that diverse bacteria from at least two different phyla (Bacteroidetes and Proteobacteria) can create two-dimensional packing of cells capable of producing SC. A pan-genome-wide association approach was used to identify genes associated with SC. The biosynthesis of uroporphyrin and pterins, as well as carbohydrate utilization and metabolism, was found to be involved. Using this information, we constructed a classifier to predict SC directly from bacterial genome sequences and validated it by cultivating and scoring 100 strains that were not part of the training set. We predicted that SCr is widely distributed within gram-negative bacteria. Analysis of over 13,000 assembled metagenomes suggested that SC is nearly absent from most habitats associated with multicellular organisms except macroalgae and is abundant in marine waters and surface/air interfaces. This work provides a large-scale ecogenomics view of SC in bacteria and identifies microbial pathways and evolutionary relationships that underlie this optical phenomenon.
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Genoma Bacteriano , Fenótipo , Cor , Bactérias/genética , Bactérias/metabolismo , Proteobactérias/genética , Proteobactérias/metabolismo , Filogenia , Metagenoma , Estudo de Associação Genômica Ampla , Bacteroidetes/genética , Bacteroidetes/metabolismoRESUMO
Endosymbioses have shaped the evolutionary trajectory of life and remain ecologically important. Investigating oceanic photosymbioses can illuminate how algal endosymbionts are energetically exploited by their heterotrophic hosts and inform on putative initial steps of plastid acquisition in eukaryotes. By combining three-dimensional subcellular imaging with photophysiology, carbon flux imaging, and transcriptomics, we show that cell division of endosymbionts (Phaeocystis) is blocked within hosts (Acantharia) and that their cellular architecture and bioenergetic machinery are radically altered. Transcriptional evidence indicates that a nutrient-independent mechanism prevents symbiont cell division and decouples nuclear and plastid division. As endosymbiont plastids proliferate, the volume of the photosynthetic machinery volume increases 100-fold in correlation with the expansion of a reticular mitochondrial network in close proximity to plastids. Photosynthetic efficiency tends to increase with cell size, and photon propagation modeling indicates that the networked mitochondrial architecture enhances light capture. This is accompanied by 150-fold higher carbon uptake and up-regulation of genes involved in photosynthesis and carbon fixation, which, in conjunction with a ca.15-fold size increase of pyrenoids demonstrates enhanced primary production in symbiosis. Mass spectrometry imaging revealed major carbon allocation to plastids and transfer to the host cell. As in most photosymbioses, microalgae are contained within a host phagosome (symbiosome), but here, the phagosome invaginates into enlarged microalgal cells, perhaps to optimize metabolic exchange. This observation adds evidence that the algal metamorphosis is irreversible. Hosts, therefore, trigger and benefit from major bioenergetic remodeling of symbiotic microalgae with potential consequences for the oceanic carbon cycle. Unlike other photosymbioses, this interaction represents a so-called cytoklepty, which is a putative initial step toward plastid acquisition.
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Metabolismo Energético , Haptófitas/metabolismo , Plâncton/citologia , Simbiose , Ciclo do Carbono , Divisão Celular , Núcleo Celular/metabolismo , Microalgas/citologia , Mitocôndrias/metabolismo , Fotossíntese , Plastídeos/metabolismoRESUMO
The rewiring of photosynthetic biomachineries to electrodes is a forward-looking semi-artificial route for sustainable bio-electricity and fuel generation. Currently, it is unclear how the electrode and biomaterial interface can be designed to meet the complex requirements for high biophotoelectrochemical performance. Here we developed an aerosol jet printing method for generating hierarchical electrode structures using indium tin oxide nanoparticles. We printed libraries of micropillar array electrodes varying in height and submicrometre surface features, and studied the energy/electron transfer processes across the bio-electrode interfaces. When wired to the cyanobacterium Synechocystis sp. PCC 6803, micropillar array electrodes with microbranches exhibited favourable biocatalyst loading, light utilization and electron flux output, ultimately almost doubling the photocurrent of state-of-the-art porous structures of the same height. When the micropillars' heights were increased to 600 µm, milestone mediated photocurrent densities of 245 µA cm-2 (the closest thus far to theoretical predictions) and external quantum efficiencies of up to 29% could be reached. This study demonstrates how bio-energy from photosynthesis could be more efficiently harnessed in the future and provide new tools for three-dimensional electrode design.
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Fotossíntese , Synechocystis , Eletricidade , Eletrodos , Impressão TridimensionalRESUMO
Living organisms have developed a wide range of appearances from iridescent to matte textures. Interestingly, angular-independent structural colors, where isotropy in the scattering structure is present, only produce coloration in the blue wavelength region of the visible spectrum. One might, therefore, wonder if such observation is a limitation of the architecture of the palette of materials available in nature. Here, by exploiting numerical modeling, we discuss the origin of isotropic structural colors without restriction to a specific light scattering regime. We show that high color purity and color saturation cannot be reached in isotropic short-range order structures for red hues. This conclusion holds even in the case of advanced scatterer morphologies, such as core-shell particles or inverse photonic glasses-explaining recent experimental findings reporting very poor performances of visual appearance for such systems.
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Living organisms frequently use structural color for coloration as an alternative mechanism to chemical pigmentation. Recently there has been a growing interest to translate structural color into synthetic materials as a more durable and less hazardous alternative to conventional pigments. Efforts to fabricate structurally colored materials take place in different fronts, from 3D printing to spray-coating and roll-to-roll casting. Stability, performance, and quality of the color, the environmental impact of the materials or their manufacturing methods are some of the heavily researched topics we discuss. First, we highlight recent examples of large-scale manufacturing technologies to fabricate structurally colored objects. Second, we discuss the current challenges to be tackled to create perfect appearances which aim at the full color gamut while caring for environmental concerns. Finally, we discuss possible scenarios that could be followed in order to involve other manufacturing methods for creating structurally colored objects.
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To unlock the widespread use of block copolymers as photonic pigments, there is an urgent need to consider their environmental impact (cf. microplastic pollution). Here we show how an inverse photonic glass architecture can enable the use of biocompatible bottlebrush block copolymers (BBCPs), which otherwise lack the refractive index contrast needed for a strong photonic response. A library of photonic pigments is produced from poly(norbornene-graft-polycaprolactone)-block-poly(norbornene-graft-polyethylene glycol), with the color tuned via either the BBCP molecular weight or the processing temperature upon microparticle fabrication. The structure-optic relationship between the 3D porous morphology of the microparticles and their complex optical response is revealed by both an analytical scattering model and 3D finite-difference time domain (FDTD) simulations. Combined, this allows for strategies to enhance the color purity to be proposed and realized with our biocompatible BBCP system.
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Fótons , Plásticos , Norbornanos , Polietilenoglicóis , PolímerosRESUMO
Plants have various strategies to protect themselves from harmful light. An example of such a protective mechanism is the growth of epicuticular nanostructures, such as a layer of hair or wax crystals. Most nanostructures are optimised to screen UV radiation, as UV light is particularly damaging for cellular tissue. We find that, contrary to the commonly found UV reflectance, the epicuticular wax crystals on Tradescantia leaves reflect strongly in the higher visible wavelength regime. Thus, they give the leaves a golden shine. We characterize the optical appearance of Tradescantia pallida 'purpurea' leaves by angularly resolved spectroscopy and compare the results to finite difference time domain simulations. We find that it is the disordered assembly of the wax platelets that is the crucial parameter to obtain the observed reflected intensity increase for higher wavelengths.
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Folhas de Planta/química , Tradescantia/química , Nanoestruturas/química , Refratometria , Análise Espectral/métodos , Raios UltravioletaRESUMO
One efficient method to obtain disordered colloidal packing is to reduce the stability of colloidal particles by adding electrolytes to the colloidal dispersions. But the correct amount of additional electrolytes must be found empirically. Here, the effect of CaCl2 on polystyrene colloidal dispersions is studied, and a link between the amount of CaCl2 and the corresponding glassy colloidal structure is quantitatively built. A threshold concentration of CaCl2 is found by dynamic light scattering. When exceeding this threshold, different nanoparticle oligomers are observed in the dispersions by analytical ultracentrifugation. The second objective is to achieve free-standing samples, which is required for many optical measurements. A universal method is established, using a centrifugal field to produce robust samples by polymerizing coassembled hydrophilic monomers to form a network, which traps the glassy colloidal structures. Photon time of flight measurements shows that the CaCl2 concentration threshold should not be exceeded. Otherwise an optical shortcut may take place. Thus, the work provides a feasible universal route to prepare macroscopic free-standing photonic glasses from electrostatically stabilized nanoparticles, suitable for further optical investigation.
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Maximizing the scattering of visible light within disordered nano-structured materials is essential for commercial applications such as brighteners, while also testing our fundamental understanding of light-matter interactions. The progress in the research field has been hindered by the lack of understanding how different structural features contribute to the scattering properties. Here we undertake a systematic investigation of light scattering in correlated disordered structures. We demonstrate that the scattering efficiency of disordered systems is mainly determined by topologically invariant features, such as the filling fraction and correlation length, and residual variations are largely accounted by the surface-averaged mean curvature of the systems. Optimal scattering efficiency can thus be obtained from a broad range of disordered structures, especially when structural anisotropy is included as a parameter. These results suggest that any disordered system can be optimised for whiteness and give comparable performance, which has far-reaching consequences for the industrial use of low-index materials for optical scattering.
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Many oceanic prey animals use transparent bodies to avoid detection. However, conspicuous eye pigments, required for vision, compromise the organisms' ability to remain unseen. We report the discovery of a reflector overlying the eye pigments in larval decapod crustaceans and show how it is tuned to render the organisms inconspicuous against the background. The ultracompact reflector is constructed from a photonic glass of crystalline isoxanthopterin nanospheres. The nanospheres' size and ordering are modulated to tune the reflectance from deep blue to yellow, enabling concealment in different habitats. The reflector may also function to enhance the acuity or sensitivity of the minute eyes by acting as an optical screen between photoreceptors. This multifunctional reflector offers inspiration for constructing tunable artificial photonic materials from biocompatible organic molecules.
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Mimetismo Biológico , Crustáceos , Células Fotorreceptoras de Invertebrados , Visão Ocular , Animais , Crustáceos/fisiologia , Olho/ultraestrutura , Fótons , Mimetismo Biológico/fisiologia , Células Fotorreceptoras de Invertebrados/fisiologiaRESUMO
A fundamental question regarding light scattering is how whiteness, generated from multiple scattering, can be obtained from thin layers of materials. This challenge arises from the phenomenon of optical crowding, whereby, for scatterers packed with filling fractions higher than ~30%, reflectance is drastically reduced due to near-field coupling between the scatterers. Here we show that the extreme birefringence of isoxanthopterin nanospheres overcomes optical crowding effects, enabling multiple scattering and brilliant whiteness from ultra-thin chromatophore cells in shrimp. Strikingly, numerical simulations reveal that birefringence, originating from the spherulitic arrangement of isoxanthopterin molecules, enables intense broadband scattering almost up to the maximal packing for random spheres. This reduces the thickness of material required to produce brilliant whiteness, resulting in a photonic system that is more efficient than other biogenic or biomimetic white materials which operate in the lower refractive index medium of air. These results highlight the importance of birefringence as a structural variable to enhance the performance of such materials and could contribute to the design of biologically inspired replacements for artificial scatterers like titanium dioxide.
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To manipulate the light-matter interaction effectively, we often rely on high refractive index inorganic nanoparticles. Such materials are contained essentially in everything that looks colorful or white: from paints to coatings but also in processed food, toothpaste, and cosmetic products. As these nanoparticles can accumulate in the human body and environment, there is a strong need to replace them with more biocompatible counterparts. In this work, we introduce various types of cellulose-based microparticles (CMPs) of four sizes with optimized dimensions for efficient light scattering that can replace traditional inorganic particles. We demonstrate that the produced materials can be exploited as highly efficient scattering enhancers, with designed optical performance. Finally, exploiting these cellulose colloids, we fabricated scattering materials and high transmittance/haze films with record performances with respect to the state-of-the-art values. The renewable and biocompatible nature of our systems, combined with their excellent optical properties, allows for the use of our cellulose-based particles in paints, LEDs, and solar cell devices and especially in applications where the biocompatibility of the component is essential, such as in food and pharmaceutical coatings.
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Celulose , Nanopartículas , Humanos , RefratometriaRESUMO
Passive radiative cooling (RC) enables the cooling of objects below ambient temperature during daytime without consuming energy, promising to be a game changer in terms of energy savings and CO2 reduction. However, so far most RC surfaces are obtained by energy-intensive nanofabrication processes or make use of unsustainable materials. These limitations are overcome by developing cellulose films with unprecedentedly low absorption of solar irradiance and strong mid-infrared (mid-IR) emittance. In particular, a cellulose-derivative (cellulose acetate) is exploited to produce porous scattering films of two different thicknesses, L ≈ 30 µm (thin) and L ≈ 300 µm (thick), making them adaptable to above and below-ambient cooling applications. The thin and thick films absorb only ≈ 5 % ${\approx}5\%$ of the solar irradiance, which represents a net cooling power gain of at least 17 W m-2 , compared to state-of-the-art cellulose-based radiative-cooling materials. Field tests show that the films can reach up to ≈5 °C below ambient temperature, when solar absorption and conductive/convective losses are minimized. Under dryer conditions (water column = 1 mm), it is estimated that the films can reach average minimum temperatures of ≈7-8 °C below the ambient. The work presents an alternative cellulose-based material for efficient radiative cooling that is simple to fabricate, cost-efficient and avoids the use of polluting materials.
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The brightest colours in nature often originate from the interaction of light with materials structured at the nanoscale. Different organisms produce such coloration with a wide variety of materials and architectures. In the case of bacterial colonies, structural colours stem for the periodic organization of the cells within the colony, and while considerable efforts have been spent on elucidating the mechanisms responsible for such coloration, the biochemical processes determining the development of this effect have not been explored. Here, we study the influence of nutrients on the organization of cells from the structurally coloured bacteria Flavobacterium strain IR1. By analysing the optical properties of the colonies grown with and without specific polysaccharides, we found that the highly ordered organization of the cells can be altered by the presence of fucoidans. Additionally, by comparing the organization of the wild-type strain with mutants grown in different nutrient conditions, we deduced that this regulation of cell ordering is linked to a specific region of the IR1 chromosome. This region encodes a mechanism for the uptake and metabolism of polysaccharides, including a polysaccharide utilization locus (PUL operon) that appears specific to fucoidan, providing new insight into the biochemical pathways regulating structural colour in bacteria.
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Bactérias , Polissacarídeos , Bactérias/metabolismo , Cor , Polissacarídeos/metabolismoRESUMO
To unlock the widespread use of block copolymers as photonic pigments, there is an urgent need to consider their environmental impact (cf. microplastic pollution). Here we show how an inverse photonic glass architecture can enable the use of biocompatible bottlebrush block copolymers (BBCPs), which otherwise lack the refractive index contrast needed for a strong photonic response. A library of photonic pigments is produced from poly(norbornene-graft-polycaprolactone)-block-poly(norbornene-graft-polyethylene glycol), with the color tuned via either the BBCP molecular weight or the processing temperature upon microparticle fabrication. The structure-optic relationship between the 3D porous morphology of the microparticles and their complex optical response is revealed by both an analytical scattering model and 3D finite-difference time domain (FDTD) simulations. Combined, this allows for strategies to enhance the color purity to be proposed and realized with our biocompatible BBCP system.
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The possibility of structuring material at the nanoscale is essential to control light-matter interactions and therefore fabricate next-generation paints and coatings. In this context, nature can serve not only as a source of inspiration for the design of such novel optical structures, but also as a primary source of materials. Here, some of the strategies used in nature to optimize light-matter interaction are reviewed and some of the recent progress in the production of optical materials made solely of plant-derived building blocks is highlighted. In nature, nano- to micrometer-sized structured materials made from biopolymers are at the origin of most of the light-transport effects. How natural photonic systems manage light scattering and what can be learned from plants and animals to produce photonic materials from biopolymers are discussed. Tuning the light-scattering properties via structural variations allows a wide range of appearances to be obtained, from whiteness to transparency, using the same renewable and biodegradable building blocks. Here, various transparent and white cellulose-based materials produced so far are highlighted.