Two-photon Dye-Based Fluorogenic Organic Nanoparticles as Intracellular Thiols Sensors.

Optical bioimaging is an ever-growing field that benefits both from the fast progress of optical instrumentation and modalities, and from the development of light-emitting probes. The efficacy of molecular fluorescent dyes is crucial, yet hindered by limited brightness and hydrophilicity. Addressing these challenges, self-stabilized fluorogenic organic nanoparticles only made of pure dyes (dFONs) are introduced in this work.

Polypeptide- and Protein-Based Conjugate Nanoparticles via Aqueous Ring-Opening Polymerization-Induced Self-Assembly (ROPISA).

Protein-polymer conjugates and polymeric nanomaterials hold great promise in many applications including biomaterials, medicine, or nanoelectronics. In this work, the first polymerization-induced self-assembly (PISA) approach performed in aqueous medium enabling protein-polymer conjugates and nanoparticles entirely composed of amino acids is presented by using ring-opening polymerization (ROP). It is indeed shown that aqueous ring-opening polymerization-induced self-assembly (ROPISA) can be used with protein or peptidic macroinitiators without prior chemical modification and afford the simple preparation of nanomaterials with protein-like property, for example, to implement biomimetic thermoresponsivity in drug delivery.

Tuning the Aggregates of Thiophene-based Trimers by Methyl Side-chain Engineering for Photocatalytic Hydrogen Evolution.

Organic π-conjugated semiconductors (OCSs) have recently emerged as a promising alternative to traditional inorganic materials for photocatalysis. However, the aggregation of OCSs in photocatalytic aqueous solution caused by self-assembly, which closely relates to the photocatalytic activity, has not yet been studied. Here, the relationship between the aggregation of 4,7-Bis(thiophen-2-yl) benzothiadiazole (TBT) and the photocatalytic activity was systematically investigated by introducing and varying the position of methyl side chains on the two peripheral thiophene units.

The quantum dot organic dye conundrum for ratiometric FRET-based biosensors: which one would you chose?

Förster resonance energy transfer (FRET) is a widely used and ideal transduction modality for fluorescent based biosensors as it offers high signal to noise with a visibly detectable signal. While intense efforts are ongoing to improve the limit of detection and dynamic range of biosensors based on biomolecule optimization, the selection of and relative location of the dye remains understudied. Herein, we describe a combined experimental and computational study to systematically compare the nature of the dye, , organic fluorophore (Cy5 or Texas Red) inorganic nanoparticle (QD), and the position of the FRET donor or acceptor on the biomolecular components.

FRET-mediated quenching of BODIPY fluorescent nanoparticles by methylene blue and its application to bacterial imaging.

High resolution and a good signal to noise ratio are a requirement in cell imaging. However, after labelling with fluorescent entities, and after several washing steps, there is often an unwanted fluorescent background that reduces the images resolution. For this purpose, we developed an approach to remove the signal from extra-cellular fluorescent nanoparticles (FNPs) during bacteria imaging, without the need for any washing steps.

An Allosteric Transcription Factor DNA-Binding Electrochemical Biosensor for Progesterone.

We describe an electrochemical strategy to transduce allosteric transcription factor (aTF) binding affinity to sense steroid hormones. Our approach utilizes square wave voltammetry to monitor changes in current output as a progesterone (PRG)-specific aTF (SRTF1) unbinds from the cognate DNA sequence in the presence of PRG. The sensor detects PRG in artificial urine samples with sufficient sensitivity suitable for clinical applications.

Hydrogel-Embedded Quantum Dot-Transcription Factor Sensors for Quantitative Progesterone Detection.

Immobilization of biosensors in or on a functional material is critical for subsequent device development and translation to wearable technology. Here, we present the development and assessment of an immobilized quantum dot-transcription factor-nucleic acid complex for progesterone detection as a first step toward such device integration. The sensor, composed of a polyhistidine-tagged transcription factor linked to a quantum dot and a fluorophore-modified cognate DNA, is embedded within a hydrogel as an immobilization matrix.

Fluorescent Copolymers for Bacterial Bioimaging and Viability Detection.

Novel fluorescent labels with high photostability and high biocompatibility are required for microbiological imaging and detection. Here, we present a green fluorescent polymer chain (GFPC), designed to be nontoxic and water-soluble, for multicolor bioimaging and real-time bacterial viability determination. The copolymer is synthesized using a straightforward one-pot reversible addition-fragmentation chain-transfer (RAFT) polymerization technique.

Surface Immobilized Nucleic Acid-Transcription Factor Quantum Dots for Biosensing.

Immobilization of biosensors on surfaces is a key step toward development of devices for real-world applications. Here the preparation, characterization, and evaluation of a surface-bound transcription factor-nucleic acid complex for analyte detection as an alternative to conventional systems employing aptamers or antibodies are described. The sensor consists of a gold surface modified with thiolated Cy5 fluorophore-labeled DNA and an allosteric transcription factor (TetR) linked to a quantum dot (QD).

Phase Transfer and DNA Functionalization of Quantum Dots Using an Easy-to-Prepare, Low-Cost Zwitterionic Polymer.

Small, stable, and bright quantum dots (QDs) are of interest in many biosensing and biomedical imaging applications, but current methodologies for obtaining these characteristics can be highly specialized or expensive. We describe a straightforward, low-cost protocol for functionalizing poly(isobutylene-alt-maleic anhydride) (PIMA) with moieties that anchor to the QD surface (histamine), impart hydrophilicity [(2-aminoethyl)trimethylammonium chloride (MeN-NH)], and provide a platform for biofunctionalization via click chemistry (dibenzocyclooctyne (DBCO)). Guidelines to successfully use this polymer for QD ligand exchange are presented, and an example of biofunctionalization with DNA is shown.

A progesterone biosensor derived from microbial screening.

Bacteria are an enormous and largely untapped reservoir of biosensing proteins. We describe an approach to identify and isolate bacterial allosteric transcription factors (aTFs) that recognize a target analyte and to develop these TFs into biosensor devices. Our approach utilizes a combination of genomic screens and functional assays to identify and isolate biosensing TFs, and a quantum-dot Förster Resonance Energy Transfer (FRET) strategy for transducing analyte recognition into real-time quantitative measurements.

Aqueous Ring-Opening Polymerization-Induced Self-Assembly (ROPISA) of N-Carboxyanhydrides.

Reported here is the first aqueous ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs) using α-amino-poly(ethylene oxide) as a macroinitiator to protect the NCA monomers from hydrolysis through spontaneous in situ self-assembly (ISA). This ROPISA process affords well-defined amphiphilic diblock copolymers that simultaneously form original needle-like nanoparticles.

A versatile and accessible polymer coating for functionalizable zwitterionic quantum dots with high DNA grafting efficiency.

Efficient and versatile functionalization of poly(anhydride maleic-alt-isobutylene) (PIMA), with economical commercial reagents, results in the one-step/one-day production of a copper-free click chemistry-ready carboxybetaine-like coating for quantum dots (QDs). The QDs are bright and stable in aqueous media and easily grafted with DNA with >95% efficiency.

Core-shell polymeric nanoparticles comprising BODIPY and fluorescein as ultra-bright ratiometric fluorescent pH sensors.

A new ratiometric fluorescent pH nanosensor is presented. It is based on ultrabright nanoparticles containing two spatially separated fluorophores: BODIPY covalently linked to the polystyrene core and fluorescein grafted to the nanoparticle shell. The nanoparticles comprise a large number (≥2500) of both fluorescent moieties.

Semiconductor Nanoplatelets: A New Class of Ultrabright Fluorescent Probes for Cytometric and Imaging Applications.

Fluorescent semiconductor nanoplatelets (NPLs) are a new generation of fluorescent probes. NPLs are colloidal two-dimensional materials that exhibit several unique optical properties, including high brightness, photostability, and extinction coefficients, as well as broad excitation and narrow emission spectra from the visible to the near-infrared spectrum. All of these exceptional fluorescence properties make NPLs interesting nanomaterials for biological applications.

A novel type of quantum dot-transferrin conjugate using DNA hybridization mimics intracellular recycling of endogenous transferrin.

Colloidal nanoparticles such as Quantum Dots (QDs) are promising alternatives to organic fluorophores, especially for long duration bioimaging. For specific targeting applications, QDs frequently require functionalization with selected proteins. In this regard, conjugation of proteins to QDs such that the nanobioconjugates retain the endogenous behavior of the coupled protein remains challenging.

Quantum dot-loaded monofunctionalized DNA icosahedra for single-particle tracking of endocytic pathways.

Functionalization of quantum dots (QDs) with a single biomolecular tag using traditional approaches in bulk solution has met with limited success. DNA polyhedra consist of an internal void bounded by a well-defined three-dimensional structured surface. The void can house cargo and the surface can be functionalized with stoichiometric and spatial precision.

Rapid and accurate detection of Escherichia coli growth by fluorescent pH-sensitive organic nanoparticles for high-throughput screening applications.

Rapid detection of bacterial growth is an important issue in the food industry and for medical research. Here we present a novel kind of pH-sensitive fluorescent nanoparticles (FANPs) that can be used for the rapid and accurate real-time detection of Escherichia coli growth. These organic particles are designed to be non-toxic and highly water-soluble.

Fast, Efficient, and Stable Conjugation of Multiple DNA Strands on Colloidal Quantum Dots.

A novel method for covalent conjugation of DNA to polymer coated quantum dots (QDs) is investigated in detail. This method is fast and efficient: up to 12 DNA strands can be covalently conjugated per QD in optimized reaction conditions. The QD-DNA conjugates can be purified using size exclusion chromatography and the QDs retain high quantum yield and excellent stability after DNA coupling.

One-pot synthesis of pegylated fluorescent nanoparticles by RAFT miniemulsion polymerization using a phase inversion process.

Water-soluble and fluorescent core-shell nanoparticles (FNP) are synthesized in a miniemulsion reversible addition-fragmentation transfer (RAFT) polymerization and are shown to respond to pH. The particles are obtained from a hydrophilic PEO-b-PAA macromolecular RAFT agent which is block-extended with styrene and a fluorescent BODIPY monomer. A miniemulsion is then formed with the residual hydrophobic monomers.