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We present the synthesis and characterization of a family of regioisomerically pure pH-sensitive rosamine fluorophores consisting of xanthene fluorophore cores, which determine the dyes’ photophysical properties such as excitation/emission wavelength, fluorescence quantum yield, and fluorescence lifetime, and differently substituted phenol moieties. The hydroxyl substituent of the phenol moiety introduces a pH sensitivity of the dyes’ fluorescence exploiting a photoinduced electron transfer (PET), that leads to a protonation-induced switching ON of the rosamine emission. Rational tuning of the pKa value of the rosamine fluorescence between 4 to 9 is achieved by altering the substitution pattern and degree of bromination of the phenolic subunits. Additionally, a temperature sensitivity of the fluorescence quantum yield is introduced or suppressed based upon the degree of rigidity of the xanthene scaffold.
Recent progress has shown that using wavelengths between 1,000 and 2,000 nm, referred to as the shortwave-infrared or near-infrared (NIR)-II range, can enable high-resolution in vivo imaging at depths not possible with conventional optical wavelengths.
However, few bioconjugatable probes of the type that have proven invaluable for multiplexed imaging in the visible and NIR range are available for imaging these wavelengths. Using rational design, we have generated persulfonated indocyanine dyes with absorbance maxima at 872 and 1,072 nm through catechol-ring and aryl-ring fusion, respectively, onto the nonamethine scaffold. Multiplexed two-color and three-color in vivo imaging using monoclonal antibody and dextran conjugates in several tumor models illustrate the benefits of concurrent labeling of the tumor and healthy surrounding tissue and lymphatics.
These efforts are enabled by complementary advances in a custom-built NIR/shortwave-infrared imaging setup and software package for multicolor real-time imaging.
Atomically precise gold nanoclusters are a fascinating class of nanomaterials that exhibit molecule-like properties and have outstanding photoluminescence (PL). Their ultrasmall size, molecular chemistry, and biocompatibility make them extremely appealing for selective biomolecule labeling in investigations of biological mechanisms at the cellular and anatomical levels. In this work, we report a simple route to incorporate a preformed Au25 nanocluster into a model bovine serum albumin (BSA) protein. A new approach combining small-angle X-ray scattering and molecular modeling provides a clear localization of a single Au25 within the protein to a cysteine residue on the gold nanocluster surface.
Attaching Au25 to BSA strikingly modifies the PL properties with enhancement and a redshift in the second near-infrared (NIR-II) window. This study paves the way to conrol the design of selective sensitive probes in biomolecules through a ligand-based strategy to enable the optical detection of biomolecules in a cellular environment by live imaging.
This paper discusses the feasibility of a novel strategy based on the combination of bioprinting nano-doping technology and laser ablation-inductively coupled plasma time-of-flight mass spectrometry analysis for the preparation and characterization of gelatin- based multi-element calibration standards suitable for quantitative imaging. To achieve this, lanthanide up-conversion nanoparticles were added to a gelatin matrix to produce the bioprinted calibration standards. The features of this bioprinting approach were com- pared with manual cryosectioning standard preparation, in terms of throughput, between batch repeatability and elemental signal homogeneity at 5 μm spatial resolution. By using bioprinting, the between batch variability for three independent standards of the same concentration of 89 Y (range 0–600 mg/kg) was reduced to 5% compared to up to 27% for cryosectioning. On this basis, the relative standard deviation ( RSD ) obtained between three independent calibration slopes measured within 1 day also reduced from 16% (using cryosectioning ) to 5% (using bioprinting), supporting the use of a single standard preparation replicate for each of the concentrations to achieve good calibration performance using bioprinting. This helped reduce the analysis time by approximately 3-fold. With cryosectioning each standard was prepared and sectioned individually, whereas using bio-printing it was possible to have up to six different standards printed simultaneously, reducing the preparation time from approximately 2 h to under 20 min (by approxi- mately 6-fold). The bio-printed calibration standards were found stable for a period of 2 months when stored at ambient temperature and in the dark.
The community-driven initiative Quality Assessment and Reproducibility for Instruments & Images in Light Microscopy (QUAREP-LiMi) wants to improve reproducibility for light microscopy image data through Quality control (QC) management of instruments and images. It aims for a common set of QC guidelines for Hardware calibration and image acquisition, management and analysis.
The development of new fluorescent organic probes effective in the NIR-II region is currently a fast-growing field and represents a challenge in the domain of medical imaging. In this study, we have designed and synthesized an innovative series of aza-boron dipyrromethenes emitting in the NIR-II region. We have investigated the effect of different water-solubilizing groups not only on the photophysical properties of the compounds but also on their in vitro and in vivo performance after bioconjugation to the antibody trastuzumab. Remarkably, we discovered that the most lipophilic compound unexpectedly displayed the most favorable in vivo properties after bioconjugation. This underlines the profound influence that the fluorophore functionalization approach can have on the efficiency of the resulting imaging agent.
DNA origami nanostructures provide a platform where dye molecules can be arranged with nanoscale accuracy allowing to assemble multiple fluorophores without dye−dye aggregation. Aiming to develop a bright and sensitive ratiometric sensor system, we systematically studied the optical properties of nanoarrays of dyes built on DNA Origami platforms using a DNA template that provides a high versatility of label choice at minimum cost. The dyes are arranged at distances, at which they efficiently interact by Förster resonance energy transfer (FRET). To optimize array brightness, the FRET efficiencies between the donor fluorescein (FAM) and the acceptor cyanine 3 were determined for different sizes of the array and for different arrangements of the dye molecules within the array. By utilizing nanoarrays providing optimum FRET efficiency and brightness, we subsequently designed a ratiometric pH nanosensor using coumarin 343 as a pH-inert FRET donor and FAM as a pHresponsive acceptor. Our results indicate that the sensitivity of a ratiometric sensor can be improved simply by arranging the dyes into a well-defined array. The dyes used here can be easily replaced by other analyte-responsive dyes, demonstrating the huge potential of DNA nanotechnology for light harvesting, signal enhancement, and sensing schemes in life sciences.
Invited for this month’s cover picture is the group of Dr. Knut Rurack at the Department of Analytical Chemistry; Reference Materials at the Bundesanstalt fuer Materialforschung und -pruefung (BAM) in Berlin (Germany). The cover picture shows how differences in color and fluorescence on a test strip can be easily read out with a mobile device. Two reference spots Frame the sensitive spot that indicates the presence of trace amounts of HgII below the threshold in a natural water sample. This dipstick contains a hybrid material that combines boron-dipyrromethene (BODIPY) probes sterically loaded into specifically tailored mesoporous silica particles, allowing for ultrasensitive HgII detection through enhanced fluorescence in a few seconds. The applicability in real water samples and fish extracts are also studied.
The synthesis, characterization, and application of mesoporous materials containing boron–dipyrromethene (BODIPY) moieties that allow the sensitive and selective detection of HgII in aqueous environments by fluorescence enhancement is reported. For this purpose, BODIPY dye I containing a thia‐aza crown ether receptor as the fluorescent probe for the detection of HgII in aqueous environments is encapsulated into mesoporous materials to avoid self‐quenching or aggregation in water. Determination of HgII is accomplished within a few seconds with high selectivity and sensitivity, reaching a limit of detection of 12 ppt. The determination of trace amounts of HgII in natural waters and in fish extracts is demonstrated by using our sensing material. The incorporation of the material into several μ‐PAD strips yields a portable, cheap, quick, and easy‐to‐handle tool for trace HgII analysis in water.
The employment of type-I pyrethroids for airplane disinfection in recent years underlines the necessity to develop sensing schemes for the rapid detection of these pesticides directly at the point-of-use. Antibody-gated indicator-releasing materials were thus developed and implemented with test strips for lateral-flow assay-based analysis employing a smartphone for readout. Besides a proper matching of pore sizes and gating macromolecules, the functionalization of both the material's outer surface as well as the strips with PEG chains enhanced system performance. This simple assay allowed for the detection of permethrin as a target molecule at concentrations down to the lower ppb level in less than 5 minutes.