Photoisomerization of Heptamethine Cyanine Dyes Results in Red-Emissive Species: Implications for Near-IR, Single-Molecule, and Super-Resolution Fluorescence Spectroscopy and Imaging.

Photoisomerization kinetics of the near-infrared (NIR) fluorophore Sulfo-Cyanine7 (SCy7) was studied by a combination of fluorescence correlation spectroscopy (FCS) and transient state (TRAST) excitation modulation spectroscopy. A photoisomerized state with redshifted emission was identified, with kinetics consistent with a three-state photoisomerization model. Combining TRAST excitation modulation with spectrofluorimetry (spectral-TRAST) further confirmed an excitation-induced redshift in the emission spectrum of SCy7.

Excitation Pulse Duration Response of Upconversion Nanoparticles and Its Applications.

Lanthanide-doped upconversion nanoparticles (UCNPs) have rich photophysics exhibiting complex luminescence kinetics. In this work, we thoroughly investigated the luminescence response of UCNPs to excitation pulse durations. Analyzing this response opens new opportunities in optical encoding/decoding and the assignment of transitions to emission peaks and provides advantages in applications of UCNPs, e.

Rose Bengal-Modified Upconverting Nanoparticles: Synthesis, Characterization, and Biological Evaluation.

High-quality upconverting NaYF:Yb,Er nanoparticles (UCNPs; 26 nm in diameter) based on lanthanides were synthesized by a high-temperature coprecipitation method. The particles were modified by bisphosphonate-terminated poly(ethylene glycol) (PEG) and Rose Bengal (RB) photosensitizer. The particles were thoroughly characterized using transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, FTIR, and X-ray photoelectron and upconversion luminescence spectroscopy in terms of morphology, hydrodynamic size, composition, and energy transfer to the photosensitizer.

Achieving low-power single-wavelength-pair nanoscopy with NIR-II continuous-wave laser for multi-chromatic probes.

Stimulated emission depletion (STED) microscopy is a powerful diffraction-unlimited technique for fluorescence imaging. Despite its rapid evolution, STED fundamentally suffers from high-intensity light illumination, sophisticated probe-defined laser schemes, and limited photon budget of the probes. Here, we demonstrate a versatile strategy, stimulated-emission induced excitation depletion (STExD), to deplete the emission of multi-chromatic probes using a single pair of low-power, near-infrared (NIR), continuous-wave (CW) lasers with fixed wavelengths.

Bioconjugates of photon-upconversion nanoparticles for cancer biomarker detection and imaging.

The detection of cancer biomarkers in histological samples and blood is of paramount importance for clinical diagnosis. Current methods are limited in terms of sensitivity, hindering early detection of disease. We have overcome the shortcomings of currently available staining and fluorescence labeling methods by taking an integrative approach to establish photon-upconversion nanoparticles (UCNP) as a powerful platform for cancer detection.

NaYF-based upconverting nanoparticles with optimized phosphonate coatings for chemical stability and viability of human endothelial cells.

The increasing interest in upconverting nanoparticles (UCNPs) in biodiagnostics and therapy fuels the development of biocompatible UCNPs platforms. UCNPs are typically nanocrystallites of rare-earth fluorides codoped with Yband Eror Tm. The most studied UCNPs are based on NaYFbut are not chemically stable in water.

PEG-Neridronate-Modified NaYF:Gd,Yb,Tm/NaGdF Core-Shell Upconverting Nanoparticles for Bimodal Magnetic Resonance/Optical Luminescence Imaging.

Upconverting nanoparticles are attracting extensive interest as a multimodal imaging tool. In this work, we report on the synthesis and characterization of gadolinium-enriched upconverting nanoparticles for bimodal magnetic resonance and optical luminescence imaging. NaYF:Gd,Yb,Tm core upconverting nanoparticles were obtained by a thermal coprecipitation of lanthanide oleate precursors in the presence of oleic acid as a stabilizer.

Formation of phosphonate coatings for improved chemical stability of upconverting nanoparticles under physiological conditions.

Upconverting nanoparticles (UCNPs) are being extensively investigated for applications in bioimaging because of their ability to emit ultraviolet, visible, and near-infrared light. NaYF4 is one of the most suitable host matrices for producing high-intensity upconversion fluorescence; however, UCNPs based on NaYF4 are not chemically stable in aqueous media. To prevent dissolution, their surfaces should be modified.

Highly colloidally stable trimodal I-radiolabeled PEG-neridronate-coated upconversion/magnetic bioimaging nanoprobes.

"All-in-one" multifunctional nanomaterials, which can be visualized simultaneously by several imaging techniques, are required for the efficient diagnosis and treatment of many serious diseases. This report addresses the design and synthesis of upconversion magnetic NaGdF:Yb/Er(Tm) nanoparticles by an oleic acid-stabilized high-temperature coprecipitation of lanthanide precursors in octadec-1-ene. The nanoparticles, which emit visible or UV light under near-infrared (NIR) irradiation, were modified by in-house synthesized PEG-neridronate to facilitate their dispersibility and colloidal stability in water and bioanalytically relevant phosphate buffered saline (PBS).

Single-Nanocrystal Studies on the Homogeneity of the Optical Properties of NaYF:Yb,Er.

Development of upconverting nanomaterials which are able to emit visible light upon near-infrared excitation opens a wide range of potential applications. Because of their remarkable photostability, they are widely used in bioimaging, optogenetics, and optoelectronics. In this work, we demonstrate the influence of several experimental conditions as well as a dopant concentration on the luminescence properties of upconverting nanocrystals (UPNCs) that need to be taken into account for their efficient use in the practical applications.

Monodisperse Core-Shell NaYF:Yb/Er@NaYF:Nd-PEG-GGGRGDSGGGY-NH Nanoparticles Excitable at 808 and 980 nm: Design, Surface Engineering, and Application in Life Sciences.

Lanthanide-doped upconversion nanoparticles (UCNPs) have a unique capability of upconverting near-infrared (NIR) excitation into ultraviolet, visible, and NIR emission. Conventional UCNPs composed of NaYF:Yb/Er(Tm) are excited by NIR light at 980 nm, where undesirable absorption by water can cause overheating or damage of living tissues and reduce nanoparticle luminescence. Incorporation of Nd ions into the UCNP lattice shifts the excitation wavelength to 808 nm, where absorption of water is minimal.

Versatile Bioconjugation Strategies of PEG-Modified Upconversion Nanoparticles for Bioanalytical Applications.

Lanthanide-doped upconversion nanoparticles (UCNPs) display highly beneficial photophysical features for background-free bioimaging and bioanalysis; however, they are instable in high ionic strength buffers, have no functional groups, and are nonspecifically interacting. Here, we have prepared NIR-excitable UCNPs that are long-term colloidally stable in buffered media and possess functional groups. Heterobifunctional poly(ethylene glycol) (PEG) linkers bearing neridronate and alkyne or maleimide were attached to UCNPs via a ligand exchange.

Chitin Nanofiber Paper toward Optical (Bio)sensing Applications.

Because of numerous inherent and unrivaled features of nanofibers made of chitin, the second most plentiful natural-based polymer (after cellulose), including affordability, abundant nature, biodegradability, biocompatibility, commercial availability, flexibility, transparency, and extraordinary mechanical and physicochemical properties, chitin nanofibers (ChNFs) are being applied as one of the most appealing bionanomaterials in a myriad of fields. Herein, we exploited the beneficial properties offered by the ChNF paper to fabricate transparent, efficient, biocompatible, flexible, and miniaturized optical sensing bioplatforms via embedding/immobilizing various plasmonic nanoparticles (silver and gold nanoparticles), photoluminescent nanoparticles (CdTe quantum dots, carbon dots, and NaYF:Yb@Er&SiO upconversion nanoparticles) along with colorimetric reagents (curcumin, dithizone, etc.) in the 3D nanonetwork scaffold of the ChNF paper.

Measurement of Sub-femtomolar Concentrations of Prostate-Specific Antigen through Single-Molecule Counting with an Upconversion-Linked Immunosorbent Assay.

Single-molecule (digital) immunoassays provide the ability to detect much lower protein concentrations than conventional immunoassays. As photon-upconversion nanoparticles (UCNPs) can be detected without optical background interference, they are excellent labels for so-called single-molecule upconversion-linked immunosorbent assays (ULISAs). We have introduced a UCNP label design based on streptavidin-PEG-neridronate and a two-step detection scheme involving a biotinylated antibody that efficiently reduces nonspecific binding on microtiter plates.

Percolation limited emission intensity from upconverting NaYF:Yb,Er nanocrystals - a single nanocrystal optical study.

Upconverting nanocrystals (UCNC) have recently been subjected to intensive investigation due to their interesting optical properties and high potential for practical applications. Despite the level of attention paid to these materials, very low quantum yield is still an important issue. In order to break through this limitation, understanding of the emission intensity limitation is crucial.

Phthalocyanine-Conjugated Upconversion NaYF :Yb /Er @SiO Nanospheres for NIR-Triggered Photodynamic Therapy in a Tumor Mouse Model.

Photodynamic therapy (PDT) has garnered immense attention as a minimally invasive clinical treatment modality for malignant cancers. However, its low penetration depth and photodamage of living tissues by UV and visible light, which activate a photosensitizer, limit the application of PDT. In this study, monodisperse NaYF :Yb /Er nanospheres 20 nm in diameter, that serve as near-infrared (NIR)-to-visible light converters and activators of a photosensitizer, were synthesized by high-temperature co-precipitation of lanthanide chlorides in a high-boiling organic solvent (octadec-1-ene).

A simple neridronate-based surface coating strategy for upconversion nanoparticles: highly colloidally stable I-radiolabeled NaYF:Yb/Er@PEG nanoparticles for multimodal in vivo tissue imaging.

In this report, monodisperse upconversion NaYF:Yb/Er nanoparticles with superior optical properties were synthesized by the oleic acid-stabilized high-temperature co-precipitation of lanthanide chlorides in octadec-1-ene as a high-boiling organic solvent. To render the particles with biocompatibility and colloidal stability in bioanalytically relevant phosphate buffered saline (PBS), they were modified by using in-house synthesized poly(ethylene glycol)-neridronate (PEG-Ner), a bisphosponate. The NaYF:Yb/Er@PEG nanoparticles showed excellent long-term stability in PBS and/or albumin without any aggregation or morphology transformation.

RGDS- and TAT-Conjugated Upconversion of NaYF4:Yb(3+)/Er(3+)&SiO2 Nanoparticles: In Vitro Human Epithelioid Cervix Carcinoma Cellular Uptake, Imaging, and Targeting.

Starting NaYF4:Yb(3+)/Er(3+) nanoparticles with size tuned from 24 to 33 nm were prepared by high-temperature coprecipitation of lanthanide chlorides in high-boiling organic solvents. To enhance colloidal stability in aqueous medium, an aminosilica shell was introduced on the surface by hydrolysis and condensation of tetramethyl orthosilicate and (3-aminopropyl)trimethoxysilane using a reverse microemulsion technique; to form alkyne groups, reaction with 4-pentynoic acid followed. Finally, the cell adhesive and cell penetrating azidopentanoyl-GGGRGDSGGGY-NH2 (RGDS) and azidopentanoyl-GGGRKKRRQRRR-NH2 (TAT) peptides were conjugated to the upconversion particles via Cu(I)-catalyzed alkyne-azide cycloaddition.

Silica-coated upconversion lanthanide nanoparticles: The effect of crystal design on morphology, structure and optical properties.

NaYF4:Yb(3+)/Er(3+) nanoparticles were synthesized by thermal decomposition of lanthanide trifluoroacetates using oleylamine (OM) as both solvent and surface binding ligand. The effect of reaction temperature and time on the properties of the particles was investigated. The nanoparticles were characterized by transmission electron microscopy (TEM), electron diffraction (ED), energy dispersive spectroscopy (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), elemental analysis and X-ray diffraction (XRD) to determine morphology, size, polydispersity, crystal structure and elemental composition of the nanocrystals.

Silica-modified monodisperse hexagonal lanthanide nanocrystals: synthesis and biological properties.

Oleic acid-stabilized hexagonal NaYF4:Yb(3+)/Er(3+) nanocrystals, emitting green and red luminescence, were prepared by the high-temperature co-precipitation of lanthanide chlorides. By varying the reaction time and the Ln(3+)/Na(+) ratio, the nanocrystal size can be controlled within the range 16-270 nm. The maximum upconversion quantum yield is achieved under 970 nm excitation.

Nanopaper as an Optical Sensing Platform.

Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC.