Enhanced Photoluminescence Detection of Immunocomplex Formation by Antibody-Functionalized, Ge-Doped Biosilica from the Diatom Cyclotella sp.

Diatoms are single-celled algae that biosynthesize cell walls of biogenic silica called "frustules" that are intricately patterned at the submicron- and nanoscale. In this study, we amplified the intrinsic luminescent properties of antibody-functionalized diatom biosilica frustules for enhanced, label-free, photoluminescence (PL) detection of immunocomplex formation. It was hypothesized that metabolically doped GeO centers in antibody-functionalized diatom biosilica would enhance PL emission associated with nucleophilic immunocomplex formation. Germanium (Ge) was metabolically inserted into the frustule biosilica by two-stage cell cultivation of the centric diatom Cyclotella sp. The biosilica frustules were isolated by hydrogen peroxide treatment and thermally annealed to convert Ge oxides in the biosilica (0.4 wt% Ge) to luminescent GeO centers. The Ge-doped biosilica frustules were then functionalized with Rabbit Immunoglobulin G (IgG). Upon immunocomplex formation with its complimentary antigen goat anti-Rabbit IgG, the Ge-oxide doped, antibody-functionalized frustule biosilica increased the intensity of PL emission by a factor of 2.6 relative to immunocomplex formation by antibody-functionalized frustule biosilica without Ge. It is proposed that the luminescent GeO centers in the Ge-oxide doped frustule biosilica were more sensitive to radiative recombination than luminescent silanol groups in frustule biosilica without Ge, resulting in a higher PL emission upon immunocomplex formation.

Optimizing the Design of Diatom Biosilica-Targeted Fusion Proteins in Biosensor Construction for Bacillus anthracis Detection.

In vivo functionalization of diatom biosilica frustules by genetic manipulation requires careful consideration of the overall structure and function of complex fusion proteins. Although we previously had transformed Thalassiosira pseudonana with constructs containing a single domain antibody (sdAb) raised against the Bacillus anthracis Sterne strain, which detected an epitope of the surface layer protein EA1 accessible in lysed spores, we initially were unsuccessful with constructs encoding a similar sdAb that detected an epitope of EA1 accessible in intact spores and vegetative cells. This discrepancy limited the usefulness of the system as an environmental biosensor for B. anthracis. We surmised that to create functional biosilica-localized biosensors with certain constructs, the biosilica targeting and protein trafficking functions of the biosilica-targeting peptide Sil3T8 had to be uncoupled. We found that retaining the ER trafficking sequence at the N-terminus and relocating the Sil3T8 targeting peptide to the C-terminus of the fusion protein resulted in successful detection of EA1 with both sdAbs. Homology modeling of antigen binding by the two sdAbs supported the hypothesis that the rescue of antigen binding in the previously dysfunctional sdAb was due to removal of steric hindrances between the antigen binding loops and the diatom biosilica for that particular sdAb.

Photonic Crystal-Enhanced Fluorescence Imaging Immunoassay for Cardiovascular Disease Biomarker Screening with Machine Learning Analysis.

When myocardial walls experience stress due to cardiovascular diseases, like heart failure, hormone N-terminal pro-B-type natriuretic peptide (NT-proBNP) is secreted into the blood. Early detection of NT-proBNP can assist diagnosis of heart failure and enable early medical intervention. A simple, cost-effective detection technique such as the widely used fluorescence imaging immunoassay is yet to be developed to detect clinically relevant levels of NT-proBNP. In this work, we demonstrate photonic crystal-enhanced fluorescence imaging immunoassay using diatom biosilica, which is capable of detecting low levels of NT-proBNP in solution with the concentration range of 0~100 pg/mL. By analyzing the fluorescence images in the spatial and spatial frequency domain with principle component analysis (PCA) and partial least squares regression (PLSR) algorithms, we create a predictive model that achieves great linearity with a validation R2 value of 0.86 and a predictive root mean square error of 14.47, allowing for good analyte quantification. To demonstrate the potential of the fluorescence immunoassay biosensor for clinical usage, we conducted qualitative screening of high and low concentrations of NT-proBNP in human plasma. A more advanced machine learning algorithm, the support vector machine classification, was paired with the PCA and trained by 160 fluorescence images. In the 40 testing images, we achieved excellent specificity of 93%, as well as decent accuracy and sensitivity of 78% and 65% respectively. Therefore, the photonic crystal-enhanced fluorescence imaging immunoassay reported in this article is feasible to screen clinically relevant levels of NT-proBNP in body fluid and evaluate the risk of heart failure.

Trace Detection of Tetrahydrocannabinol in Body Fluid via Surface-Enhanced Raman Scattering and Principal Component Analysis.

Tetrahydrocannabinol (THC) is the main active component in marijuana and the rapid detection of THC in human body fluid plays a critical role in forensic analysis and public health. Surface-enhanced Raman scattering (SERS) sensing has been increasingly used to detect illicit drugs; however, only limited SERS sensing results of THC in methanol solution have been reported, while its presence in body fluids, such as saliva or plasma, has yet to be investigated. In this article, we demonstrate the trace detection of THC in human plasma and saliva solution using a SERS-active substrate formed by in situ growth of silver nanoparticles (Ag NPs) on diatom frustules. THC at extremely low concentration of 1 pM in plasma and purified saliva solutions were adequately distinguished with good reproducibility. The SERS peak at 1603 cm-1 with standard deviation of 3.4 cm-1 was used for the evaluation of THC concentration in a methanol solution. Our SERS measurement also shows that this signature peak experiences a noticeable wavenumber shift and a slightly wider variation in the plasma and saliva solution. Additionally, we observed that THC in plasma or saliva samples produces a strong SERS peak at 1621 cm-1 due to the stretching mode of O-C═O, which is related to the metabolic change of THC structures in body fluid. To conduct a quantitative analysis, principal component analysis (PCA) was applied to analyze the SERS spectra of 1 pM THC in methanol solution, plasma, and purified saliva samples. The maximum variability of the first three principal components was achieved at 71%, which clearly denotes the impact of different biological background signals. Similarly, the SERS spectra of THC in raw saliva solution under various metabolic times were studied using PCA and 98% of the variability is accounted for in the first three principal components. The clear separation of samples measured at different THC resident times can provide time-dependent information on the THC metabolic process in body fluids. A linear regression model was used to estimate the metabolic rate of THC in raw saliva and the predicted metabolic time in the testing data set matched well with the training data set. In summary, the hybrid plasmonic-biosilica SERS substrate can achieve ultrasensitive, near-quantitative detection of trace levels of THC in complex body fluids, which can potentially transform forensic sensing techniques to detect marijuana abuse.

Highly-porous diatom biosilica stationary phase for thin-layer chromatography.

This study showed that a nanostructured, highly-porous stationary phase composed of randomly-deposited biosilica frustules isolated from living cells of diatom Pinnularia sp. significantly improved the conventional thin-layer chromatography (TLC) based separation of the triphenylmethane dyes malachite green and fast green relative to silica gel by two mobile phases (9:1:1 v/v 1-butanol:ethanol:water, 5:1:2 v/v 1-butanol:acetic acid:water). Although both stationary phases were composed of amorphous silica rich in silanol groups with particle size of 10-12 µm, diatom biosilica frustules were highly porous, hollow shells with surface structure dominated by 200 nm pore arrays. Diatom biosilica significantly improved the mobility of both malachite green and fast green, enabling the resolution of these analytes. The diatom biosilica layer had a high void fraction of 96% but reduced the flow velocity and permeability constant by a factor of two relative to silica gel. TLC performance was enhanced, as evidenced by ten-fold reduction in theoretical plate height for both analytes using the 1-butanol:acetic acid:water mobile phase, and an increased difference in retention time between malachite green and fast green (ΔRf = 0.26) using the 1-butanol:ethanol:water mobile phase. Analysis of plate height vs. solvent front position by the modified van Deemter equation suggested that dispersive mass transfer was reduced, leading to improved analyte resolution, and that surface of the frustule decreased boundary layer resistance, leading to increased analyte flux. Overall, the basis for improved chromatographic performance is believed to be the unique nano- and microstructure of the diatom biosilica frustule.

Biological Photonic Crystal-Enhanced Plasmonic Mesocapsules: Approaching Single-Molecule Optofluidic-SERS Sensing.

Surface-enhanced Raman scattering (SERS) sensing in microfluidic devices, namely optofluidic-SERS, suffers an intrinsic trade-off between mass transport and hot spot density, both of which are required for ultra-sensitive detection. To overcome this compromise, photonic crystal-enhanced plasmonic mesocapsules are synthesized, utilizing diatom biosilica decorated with in-situ growth silver nanoparticles (Ag NPs). In our optofluidic-SERS testing, 100× higher enhancement factors and greater than 1,000× better detection limit were achieved compared with traditional colloidal Ag NPs, the improvement of which is attributed to unique properties of the mesocapsules. First, the porous diatom biosilica frustules serve as carrier capsules for high density Ag NPs that form high density plasmonic hot-spots. Second, the submicron-pores embedded in the frustule walls not only create a large surface-to-volume ratio allowing for effective analyte capture, but also enhance the local optical field through the photonic crystal effect. Last, the mesocapsules provide effective mixing with analytes as they are flowing inside the microfluidic channel. The reported mesocapsules achieved single molecule detection of Rhodamine 6G in microfluidic devices and were further utilized to detect 1 nM of benzene and chlorobenzene compounds in tap water with near real-time response, which successfully overcomes the constraint of traditional optofluidic sensing.

Photonic crystal enhanced fluorescence immunoassay on diatom biosilica.

Fluorescence biosensing is one of the most established biosensing methods, particularly fluorescence spectroscopy and microscopy. These are two highly sensitive techniques but require high-grade electronics and optics to achieve the desired sensitivity. Efforts have been made to implement these methods using consumer grade electronics and simple optical setups for applications such as point-of-care diagnostics, but the sensitivity inherently suffers. Sensing substrates, capable of enhancing fluorescence are thus needed to achieve high sensitivity for such applications. In this paper, we demonstrate a photonic crystal-enhanced fluorescence immunoassay biosensor using diatom biosilica, which consists of silica frustules with sub-100 nm periodic pores. Utilizing the enhanced local optical field, the Purcell effect and increased surface area from the diatom photonic crystals, we create ultrasensitive immunoassay biosensors that can significantly enhance fluorescence spectroscopy as well as fluorescence imaging. Using standard antibody-antigen-labeled antibody immunoassay protocol, we experimentally achieved 100× and 10× better detection limit with fluorescence spectroscopy and fluorescence imaging respectively. The limit of detection of the mouse IgG goes down to 10-16 M (14 fg/mL) and 10-15 M (140 fg/mL) for the two respective detection modalities, virtually sensing a single mouse IgG molecule on each diatom frustule. The effectively enhanced fluorescence imaging in conjunction with the simple hot-spot counting analysis method used in this paper proves the great potential of diatom fluorescence immunoassay for point-of-care biosensing.

Control of chitin nanofiber production by the lipid-producing diatom Cyclotella Sp. through fed-batch addition of dissolved silicon and nitrate in a bubble-column photobioreactor.

Diatoms are single-celled algae that make cell walls of nanopatterned biogenic silica called frustules through metabolic uptake of dissolved silicon and its templated condensation into biosilica. The centric marine diatom Cyclotella sp. also produces intracellular lipids and the valued coproduct chitin, an N-acetyl glucosamine biopolymer that is extruded from selected frustule pores as pure nanofibers. The goal of this study was to develop a nutrient feeding strategy to control the production of chitin nanofibers from Cyclotella with the coproduction of biofuel lipids. A two-stage phototrophic cultivation process was developed where Stage I set the cell suspension to a silicon-starved state under batch operation, and Stage II continuously added silicon and nitrate to the silicon-starved cells to enable one more cell doubling to 4 × 106 cells mL-1 . The silicon delivery rate was set to enable a silicon-limited cell division rate under cumulative delivery of 0.8 mM Si and 1.2 mM nitrate (1.5:1 mol N/mol Si) over a 4- to 14-day addition period. In Stage II, both cell number and chitin production were linear with time. Cell number and the specific chitin production rate increased linearly with increasing silicon delivery rate to achieve cumulative product yields of 13 ± 1 mg chitin/109 cells and 33 ± 3 mg lipid/109 cells. Therefore, chitin production is controlled through cell division, which is externally controlled through silicon delivery. Lipid production was not linearly correlated to silicon delivery and occurred primarily during Stage I, just after the complete co-consumption of both dissolved silicon and nitrate. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:407-415, 2017.

Detecting explosive molecules from nanoliter solution: A new paradigm of SERS sensing on hydrophilic photonic crystal biosilica.

We demonstrate a photonic crystal biosilica surface-enhanced Raman scattering (SERS) substrate based on a diatom frustule with in-situ synthesized silver nanoparticles (Ag NPs) to detect explosive molecules from nanoliter (nL) solution. By integrating high density Ag NPs inside the nanopores of diatom biosilica, which is not achievable by traditional self-assembly techniques, we obtained ultra-high SERS sensitivity due to dual enhancement mechanisms. First, the hybrid plasmonic-photonic crystal biosilica with three dimensional morphologies was obtained by electroless-deposited Ag seeds at nanometer sized diatom frustule surface, which provides high density hot spots as well as strongly coupled optical resonances with the photonic crystal structure of diatom frustules. Second, we discovered that the evaporation-driven microscopic flow combined with the strong hydrophilic surface of diatom frustules is capable of concentrating the analyte molecules, which offers a simple yet effective mechanism to accelerate the mass transport into the SERS substrate. Using the inkjet printing technology, we are able to deliver multiple 100pico-liter (pL) volume droplets with pinpoint accuracy into a single diatom frustule with dimension around 30µm×7µm×5µm, which allows for label-free detection of explosive molecules such as trinitrotoluene (TNT) down to 10-10M in concentration and 2.7×10-15g in mass from 120nL solution. Our research illustrates a new paradigm of SERS sensing to detect trace level of chemical compounds from minimum volume of analyte using nature created photonic crystal biosilica materials.

Chemical and Biological Sensing Using Diatom Photonic Crystal Biosilica With In-Situ Growth Plasmonic Nanoparticles.

In this paper, we described a new type of bioenabled nano-plasmonic sensors based on diatom photonic crystal biosilica with in-situ growth silver nanoparticles and demonstrated label-free chemical and biological sensing based on surface-enhanced Raman scattering (SERs) from complex samples. Diatoms are photosynthetic marine micro-organisms that create their own skeletal shells of hydrated amorphous silica, called frustules, which possess photonic crystal-like hierarchical micro- & nanoscale periodic pores. Our research shows that such hybrid plasmonic-biosilica nanostructures formed by cost-effective and eco-friendly bottom-up processes can achieve ultra-high limit of detection for medical applications, food sensing, water/air quality monitoring and geological/space research. The enhanced sensitivity comes from the optical coupling of the guided-mode resonance of the diatom frustules and the localized surface plasmons of the silver nanoparticles. Additionally, the nanoporous, ultra-hydrophilic diatom biosilica with large surface-to-volume ratio can concentrate more analyte molecules to the surface of the SERS substrates, which can help to detect biomolecules that cannot be easily adsorbed by metallic nanoparticles.

Optofluidic sensing from inkjet-printed droplets: the enormous enhancement by evaporation-induced spontaneous flow on photonic crystal biosilica.

Novel transducers for detecting an ultra-small volume of an analyte solution play pivotal roles in many applications such as chemical analysis, environmental protection and biomedical diagnosis. Recent advances in optofluidics offer tremendous opportunities for analyzing miniature amounts of samples with high detection sensitivity. In this work, we demonstrate enormous enhancement factors (106-107) of the detection limit for optofluidic analysis from inkjet-printed droplets by evaporation-induced spontaneous flow on photonic crystal biosilica when compared with conventional surface-enhanced Raman scattering (SERS) sensing using the pipette dispensing technology. Our computational fluid dynamics simulation has shown a strong recirculation flow inside the 100 picoliter droplet during the evaporation process due to the thermal Marangoni effect. The combination of the evaporation-induced spontaneous flow in micron-sized droplets and the highly hydrophilic photonic crystal biosilica is capable of providing a strong convection flow to combat the reverse diffusion force, resulting in a higher concentration of the analyte molecules at the diatom surface. In the meanwhile, high density hot-spots provided by the strongly coupled plasmonic nanoparticles with photonic crystal biosilica under a 1.5 µm laser spot are verified by finite-difference time domain simulation, which is crucial for SERS sensing. Using a drop-on-demand inkjet device to dispense multiple 100 picoliter analyte droplets with pinpoint accuracy, we achieved the single molecule detection of Rhodamine 6G and label-free sensing of 4.5 × 10-17 g trinitrotoluene from only 200 nanoliter solution.

Micro-photoluminescence of single living diatom cells.

Diatoms are single-celled microalgae that possess a nanostructured, porous biosilica shell called a frustule. This study characterized the micro-photoluminescence (µ-PL) emission of single living cells of the photosynthetic marine diatom Thalassiosira pseudonana in response to UV laser irradiation at 325 nm using a confocal Raman microscope. The photoluminescence (PL) spectrum had two primary peaks, one centered at 500-510 nm, which was attributed to the frustule biosilica, and a second peak at 680 nm, which was attributed to auto-fluorescence of photosynthetic pigments. The portion of the µ-PL emission spectrum associated with biosilica frustule in the single living diatom cell was similar to that from single biosilica frustules isolated from these diatom cells. The PL emission by the biosilica frustule in the living cell emerged only after cells were cultivated to silicon depletion. The discovery of the discovery of PL emission by the frustule biosilica within a single living diatom itself, not just its isolated frustule, opens up future possibilities for living biosensor applications, where the interaction of diatom cells with other molecules can be probed by µ-PL spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.

Antigen Binding and Site-Directed Labeling of Biosilica-Immobilized Fusion Proteins Expressed in Diatoms.

The diatom Thalassiosira pseudonana was genetically modified to express biosilica-targeted fusion proteins comprising either enhanced green fluorescent protein (EGFP) or single chain antibodies engineered with a tetracysteine tagging sequence. Of interest were the site-specific binding of (1) the fluorescent biarsenical probe AsCy3 and AsCy3e to the tetracysteine tagged fusion proteins and (2) high and low molecular mass antigens, the Bacillus anthracis surface layer protein EA1 or small molecule explosive trinitrotoluene (TNT), to biosilica-immobilized single chain antibodies. Analysis of biarsenical probe binding using fluorescence and structured illumination microscopy indicated differential colocalization with EGFP in nascent and mature biosilica, supporting the use of either EGFP or bound AsCy3 and AsCy3e in studying biosilica maturation. Large increases in the lifetime of a fluorescent analogue of TNT upon binding single chain antibodies provided a robust signal capable of discriminating binding to immobilized antibodies in the transformed frustule from nonspecific binding to the biosilica matrix. In conclusion, our results demonstrate an ability to engineer diatoms to create antibody-functionalized mesoporous silica able to selectively bind chemical and biological agents for the development of sensing platforms.

Photoluminescence detection of 2,4,6-trinitrotoluene (TNT) binding on diatom frustule biosilica functionalized with an anti-TNT monoclonal antibody fragment.

A selective and label-free biosensor for detection of the explosive compound 2,4,6-trinitrotoluene (TNT) in aqueous solution was developed based on the principle of photoluminescence quenching of upon immunocomplex formation with antibody-functionalized diatom frustule biosilica. The diatom frustule is an intricately nanostructured, highly porous biogenic silica material derived from the shells of microscopic algae called diatoms. This material emits strong visible blue photoluminescence (PL) upon UV excitation. PL-active frustule biosilica was isolated from cultured cells of the marine diatom Pinnularia sp. and functionalized with a single chain variable fragment (scFv) derived from an anti-TNT monoclonal antibody. When TNT was bound to the anti-TNT scFv-functionalized diatom frustule biosilica, the PL emission from the biosilica was partially quenched due to the electrophilic nature of the nitro (-NO2) groups on the TNT molecule. The dose-response curve for immunocomplex formation of TNT on the scFv-functionalized diatom frustule biosilica had a half-saturation binding constant of 6.4 ± 2.4·10(-8)M and statistically-significant measured detection limit of 3.5·10(-8)M. The binding and detection were selective for TNT and TNB (trinitrobenzene) but not RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) or 2,6-DNT (2,6-dinitrotoluene).

Bioenabled SERS Substrates for Food Safety and Drinking Water Monitoring.

We present low-cost bioenabled surface-enhanced Raman scattering (SERS) substrates that can be massively produced in sustainable and eco-friendly methods with significant commercial potentials for the detection of food contamination and drinking water pollution. The sensors are based on diatom frustules with integrated plasmonic nanoparticles. The ultra-high sensitivity of the SERS substrates comes from the coupling between the diatom frustules and Ag nanoparticles to achieve dramatically increased local optical field to enhance the light-matter interactions for SERS sensing. We successfully applied the bioenabled SERS substrates to detect melamine in milk and aromatic compounds in water with sensitivity down to 1µg/L.

Ultra-sensitive immunoassay biosensors using hybrid plasmonic-biosilica nanostructured materials.

We experimentally demonstrate an ultra-sensitive immunoassay biosensor using diatom biosilica with self-assembled plasmonic nanoparticles. As the nature-created photonic crystal structures, diatoms have been adopted to enhance surface plasmon resonances of metal nanoparticles on the surfaces of diatom frustules and to increase the sensitivity of surface-enhanced Raman scattering (SERS). In this study, a sandwich SERS immunoassay is developed based on the hybrid plasmonic-biosilica nanostructured materials that are functionalized with goat anti-mouse IgG. Our experimental results show that diatom frustules improve the detection limit of mouse IgG to 10 pg/mL, which is ˜100× better than conventional colloidal SERS sensors on flat glass. Ultra-sensitive immunoassay biosensor using diatom biosilica with self-assembled plasmonic nanoparticles.

Surface-Enhanced Raman Spectroscopy Sensors From Nanobiosilica With Self-Assembled Plasmonic Nanoparticles.

We present an innovative surface-enhanced Raman spectroscopy (SERS) sensor based on a biological-plasmonic hybrid nanostructure by self-assembling silver (Ag) nanoparticles into diatom frustules. The photonic-crystal-like diatom frustules provide a spatially confined electric field with enhanced intensity that can form hybrid photonic-plasmonic modes through the optical coupling with Ag nanoparticles. The experimental results demonstrate 4-6× and 9-12× improvement of sensitivities to detect the Raman dye for resonance and nonresonance SERS sensing, respectively. Such low-cost and high-sensitivity SERS sensors have significant potentials for label-free biosensing.

Enhancing surface plasmon resonances of metallic nanoparticles by diatom biosilica.

Diatoms are single-celled algaes that make photonic-crystal-like silica shells or frustules with hierarchical micro- & nano-scale features consisting of two-dimensional periodic pores. This article reports the use of diatom frustules as an integration platform to enhance localized surface plasmon resonances of self-assembled silver nanoparticles (NPs) on the surface of diatom frustules. Theoretical and experimental results show enhanced localized surface plasmons due to the coupling with the guided-mode resonances of the frustules. We observed 2 × stronger optical extinction and over 4 × higher sensitivity of surface-enhanced Raman scattering of Rhodmine 6G from the NPs-on-diatom than the NPs-on-glass structure.

Equilibrium partitioning behavior of naphthalene and phenanthrene with axenic microplantlets of the temperate green seaweed Acrosiphonia coalita.

The partitioning behavior of the polycyclic aromatic hydrocarbon (PAH) compounds naphthalene and phenanthrene with the temperate green seaweed Acrosiphonia coalita was characterized. The uptake and partitioning experiments were designed to prevent PAH volatilization, and the PAH concentration was measured in both the seawater liquid medium and in the algal biomass. Axenic microplantlets of A. coalita were used in all experiments to eliminate the possibility of microbial PAH biotransformation. Gas chromatography/mass spectrometry analysis did not reveal any putative metabolites of phenanthrene oxidative biotransformation in either the seawater medium or the algal biomass, but did show that dissolved organic matter from algal biomass constituents were in the liquid medium. The algal biomass grew by 30% over the 114h duration of the partitioning experiments, suggesting PAH compounds did not harm the organism. Both living and heat-killed microplantlets partitioned PAH compounds into the biomass. Naphthalene and phenanthrene reversibly partitioned into the lipid fraction of the algal biomass with equilibrium partitioning constants of 0.130+/-0.007 and 1.58+/-0.03Lg(-1) dry cell mass, respectively, which scaled proportionally to their octanol-water partitioning constants. The PAH material balance for the partitioning process closed between 86% and 100% for naphthalene adsorption and phenanthrene desorption, but closed at 52% for phenanthrene adsorption. To account for the loss, it was proposed that phenanthrene interacted with dissolved organic matter released by the living algal biomass. This study has provided fundamental information needed to assess how seaweeds can play a role in the bioaccumulation and bioremediation of PAH compounds in the marine environment.

Self-assembly of nanostructured diatom microshells into patterned arrays assisted by polyelectrolyte multilayer deposition and inkjet printing.

Individual shells of the diatom Coscinodiscus were self-assembled into a rectangular array on a glass surface that possessed a polyelectrolyte multilayer patterned through inkjet printing. This patterned thin film possessed hierarchical order with nanostructure provided by the diatom biosilica. The process used two polyelectrolytes with opposite electric potentials to control the surface charge of the substrate. The fine features of the diatom frustules were perfectly preserved as a result of the mild conditions of the deposition process. This technique has the potential to enable large-scale device applications that harness the unique properties of functionalized diatom biosilica.