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

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.

Optimizing the Design of Diatom Biosilica-Targeted Fusion Proteins in Biosensor Construction for 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 with constructs containing a single domain antibody (sdAb) raised against the 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 .

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.

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.

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.

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.

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.

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.

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 (10-10) 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Metabolic insertion of nanostructured TiO2 into the patterned biosilica of the diatom Pinnularia sp. by a two-stage bioreactor cultivation process.

Diatoms are single-celled algae that make silica shells or frustules with intricate nanoscale features imbedded within periodic two-dimensional pore arrays. A two-stage photobioreactor cultivation process was used to metabolically insert titanium into the patterned biosilica of the diatom Pinnularia sp. In Stage I, diatom cells were grown up on dissolved silicon until silicon starvation was achieved.

Biological fabrication of photoluminescent nanocomb structures by metabolic incorporation of germanium into the biosilica of the diatom Nitzschia frustulum.

Diatoms are single-celled algae that make microscale silica shells or "frustules" with intricate nanoscale features such as two-dimensional pore arrays. In this study, the metabolic insertion of low levels of germanium into the frustule biosilica of the pennate diatom Nitzschia frustulum by a two-stage cultivation process induced the formation of frustules which strongly resembled double-sided nanocomb structures. The final product from the two-stage cultivation process contained 0.

Photoluminescence of silica nanostructures from bioreactor culture of marine diatom Nitzschia frustulum.

The marine diatom Nitzschia frustulum is a single-celled photosynthetic organism that uses soluble silicon as the substrate to fabricate intricately patterned silica shells called frustules consisting of 200 nm diameter pores in a rectangular array. Controlled photobioreactor cultivation of the N. frustulum cell suspension to silicon starvation induced changes in the nanostructure of the diatom frustule, which in turn imparted blue photoluminescence (PL) to the frustule biosilica.

Comparison of TNT removal from seawater by three marine macroalgae.

Axenic plantlets derived from three species of marine macroalgae, the temperate green alga Acrosiphonia coalita, the temperate red alga Porphyra yezoensis, and the tropical red alga Portieria hornemannii, all possessed a similar metabolic route to remove the explosive compound 2,4,6-trinitrotolune (TNT) from seawater. At a biomass density of 1.2 g l(-1) and initial TNT concentrations of 10 mg l(-1) or less, TNT removal from seawater was 100% within 72 h for P.

Uptake and biotransformation of 2,4,6-trinitrotoluene (TNT) by microplantlet suspension culture of the marine red macroalga Portieria hornemannii.

Microplantlets of the marine red macroalga Portieria hornemannii efficiently removed the explosive compound 2,4,6-trinitrotoluene (TNT) from seawater. Photosynthetic, axenic microplantlets (1.2 g FW/L) were challenged with enriched seawater medium containing dissolved TNT at concentrations of 1.