Engineered Glucose Oxidase-Carbon Nanotube Conjugates for Tissue-Translatable Glucose Nanosensors

Continuous and non-invasive glucose monitoring and imaging is important for disease diagnosis, treatment, and management. However, glucose monitoring remains a technical challenge owing to the dearth of tissue-transparent glucose sensors. In this study, we present the development of near-infrared fluorescent single-walled carbon nanotube (SWCNT) based nanosensors directly functionalized with glucose oxidase (GOx) capable of immediate and reversible glucose imaging in biological fluids and tissues. We prepared GOx-SWCNT nanosensors by facile sonication of SWCNT with GOx in a manner that-surprisingly-does not compromise the ability of GOx to detect glucose. Importantly, we find by using denatured GOx that the fluorescence modulation of GOx-SWCNT is not associated with the catalytic oxidation of glucose but rather triggered by glucose-GOx binding. Leveraging the unique response mechanism of GOx-SWCNT nanosensors, we developed catalytically inactive apo-GOx-SWCNT that enables both sensitive and reversible glucose imaging, exhibiting a ΔF/F0 of up to 40 % within 1 s of exposure to glucose without consuming the glucose analyte. We finally demonstrate the potential applicability of apo-GOx-SWCNT in biomedical applications by glucose quantification in human plasma and glucose imaging in mouse brain slices.

Development of Dissolution Dynamic Nuclear Polarization of [15 N3 ]Metronidazole: A Clinically Approved Antibiotic

We report dissolution Dynamic Nuclear Polarization (d-DNP) of [15 N3 ]metronidazole ([15 N3 ]MNZ) for the first time. Metronidazole is a clinically approved antibiotic, which can be potentially employed as a hypoxia-sensing molecular probe using 15 N hyperpolarized (HP) nucleus. The DNP process is very efficient for [15 N3 ]MNZ with an exponential build-up constant of 13.8 min using trityl radical. After dissolution and sample transfer to a nearby 4.7 T Magnetic Resonance Imaging scanner, HP [15 N3 ]MNZ lasted remarkably long with T1 values up to 343 s and 15 N polarizations up to 6.4 %. A time series of HP [15 N3 ]MNZ images was acquired in vitro using a steady state free precession sequence on the 15 NO2 peak. The signal lasted over 13 min with notably long T2 of 20.5 s. HP [15 N3 ]MNZ was injected in the tail vein of a healthy rat, and dynamic spectroscopy was performed over the rat brain. The in vivo HP 15 N signals persisted over 70 s, demonstrating an unprecedented opportunity for in vivo studies.

Branched Multimeric Peptides as Affinity Reagents for the Detection of α-Klotho Protein

α-Klotho, an aging-related protein found in the kidney, parathyroid gland, and choroid plexus, acts as an essential co-receptor with the fibroblast growth factor 23 receptor complex to regulate serum phosphate and vitamin D levels. Decreased levels of α-Klotho are a hallmark of age-associated diseases. Detecting or labeling α-Klotho in biological milieu has long been a challenge, however, hampering the understanding of its role. Here, we developed branched peptides by single-shot parallel automated fast-flow synthesis that recognize α-Klotho with improved affinity relative to their monomeric versions. These peptides were further shown to selectively label Klotho for live imaging in kidney cells. Our results demonstrate that automated flow technology enables rapid synthesis of complex peptide architectures, showing promise for future detection of α-Klotho in physiological settings.

A SLC35C2 Transporter-Targeting Fluorescent Probe for the Selective Detection of B Lymphocytes Identified by SLC-CRISPRi and Unbiased Fluorescence Library Screening

T and B lymphocytes are two major adaptive immune cells in the human defense system. To real-time monitor their diverse functions, a live-cell-selective probe for only one cell type is need to investigate the complex interaction of the immune cells. Herein, a small-molecule probe CDyB for live B cells is developed by an unbiased fluorescence library screening. The cell selectivity was confirmed by multiparametric single-cell analysis using CyTOF. Through a systematic SLC-CRISPRi library screening, the molecular target of CDyB was identified as SLC35C2 transporter based on a gating-oriented live-cell distinction (GOLD) mechanism. The gene expression analysis and knock-out experiments validated that the SLC35C2 transporter was the target for CDyB distinction. Interestingly, when CDyB was applied to study B cell development, the CDyB fluorescence and SLC35C2 expression were positively correlated with the B cell maturation process, and not involved in the T cell development.

A Photoacoustic-Fluorescent Imaging Probe for Proteolytic Gingipains Expressed by Porphyromonas gingivalis

Porphyromonas gingivalis is a keystone pathogen in periodontal disease. We herein report a dual-modal fluorescent and photoacoustic imaging probe for the detection of gingipain proteases secreted by P. gingivalis. Upon proteolytic cleavage by Arg-specific gingipain (RgpB), five-fold photoacoustic enhancement and >100-fold fluorescence activation was measured with detection limits of 1.1 nM RgpB and 5.0E4 CFU mL-1 bacteria in vitro. RgpB activity was imaged in porcine jaws with low-nanomolar sensitivity. Diagnostic efficacy was evaluated in gingival crevicular fluid samples from subjects with and without periodontal disease, wherein activation was correlated to qPCR-based detection of P. gingivalis (Pearson's r=0.71). Finally, photoacoustic imaging of RgpB-cleaved probe was achieved in murine brains ex vivo, with relevance and potential utility for disease models of general infection by P. gingivalis, motivated by the recent biological link between gingipain and Alzheimer's disease.

Enhanced Blue Afterglow through Molecular Fusion for Bio-applications

Afterglow materials have drawn considerable attention due to their attractive luminescent properties. However, their low-efficiency luminescence in aqueous environment limits their applications in life sciences. Here, we developed a molecular fusion strategy to improve the afterglow efficiency of photochemical afterglow materials. By fusing a cache unit with an emitter, we obtained a blue afterglow system with a quantum yield up to 2.59 %. This is 162 times higher than that achieved with the traditional physical mixing system and more than an order of magnitude larger than that of the covalent coupling system. High-efficiency afterglow nanoparticles were obtained and utilized for bio-imaging with a high signal-to-noise ratio (SNR) of 131, and for the lateral flow immunoassay (LFIA) of β-hCG with a low limit of detection (LOD) of 0.34 mIU mL^-1 . This paves a new way for the construction of high-efficiency afterglow materials and expands the number of luminescence reporter candidates for disease diagnosis and bio-imaging.

Reversibly Photoswitching Upconversion Nanoparticles for Super-Sensitive Photoacoustic Molecular Imaging

Photoacoustic (PA) imaging uses light excitation to generate the acoustic signal for detection and improves tissue penetration depth and spatial resolution in the clinically relevant depth of living subjects. However, strong background signals from blood and pigments have significantly compromised the sensitivity of PA imaging with exogenous contrast agents. Here we report a nanoparticle-based probe design that uses light to reversibly modulate the PA emission to enable photoacoustic photoswitching imaging (PAPSI) in living mice. Such a nanoprobe is built with upconverting nanocrystals and photoswitchable small molecules and can be switched on by NIR light through upconversion to UV energy. Reversibly photoswitching of the nanoprobe reliably removed strong tissue background, increased the contrast-to-noise ratio, and thus improved imaging sensitivity. We have shown that PAPSI can image 0.05 nM of the nanoprobe in hemoglobin solutions and 10⁴ labeled cancer cells after implantation in living mice using a commercial PA imager.

Carbonate-Based Fluorescent Chemical Tool for Uncovering Carboxylesterase 1 (CES1) Activity Variations in Live Cells

Carboxylesterase 1 (CES1) plays a key role in the metabolism of endogenous biomolecules and xenobiotics including a variety of pharmaceuticals. Despite the established importance of CES1 in drug metabolism, methods to study factors that can vary CES1 activity are limited with only a few suitable for use in live cells. Herein, we report the development of FCP1, a new CES1 specific fluorescent probe with a unique carbonate substrate constructed from commercially available reagents. We show that FCP-1 can specifically report on endogenous CES1 activity with a robust fluorescence response in live HepG2 cells through studies with inhibitors and genetic knockdowns. Subsequently, we deployed FCP-1 to develop a live cell fluorescence microscopy-based approach to identify activity differences between CES1 isoforms. To the best of our knowledge, this is the first application of a fluorescent probe to measure the activity of CES1 sequence variants in live cells.

Chemical synthesis of the fluorescent, cyclic dinucleotides cthGAMP

The cGAS‐STING pathway is known for its role in sensing cytosolic DNA introduced by a viral infection, bacterial invasion or tumorigenesis. Free DNA is recognized by the cyclic GMP‐AMP synthase (cGAS) catalyzing the production of 2’,3’‐cyclic guanosine monophosphate‐adenosine monophosphate (2’,3’‐cGAMP) in mammals. This cyclic dinucleotide acts as a second messenger, activating the stimulator of interferon genes (STING) that finally triggers the transcription of interferon genes and inflammatory cytokines. Due to the therapeutic potential of this pathway, both the production and the detection of cGAMP via fluorescent moieties for assay development is of great importance. Here, we introduce the paralleled synthetic access to the intrinsically fluorescent, cyclic dinucleotides 2’3’‐c^thGAMP and 3’3’‐c^thGAMP based on phosphoramidite and phosphate chemistry, adaptable for large scale synthesis. We examine their binding properties to murine and human STING and confirm biological activity including interferon induction by 2’3’‐c^thGAMP in THP‐1 monocytes. Two‐photon imaging revealed successful cellular uptake of 2’3’‐c^thGAMP in THP‐1 cells.

Targeting Sugar Uptake and Metabolism for Cancer Identification and Therapy: An Overview

Metabolic deregulations have emerged as a cancer characteristic, opening a broad avenue for strategies and tools to target cancer through sugar uptake and metabolism. High expression levels of sugar transporters in cancer cells offered glycoconjugation as an approach to achieve enhanced cellular accumulation of drugs and imaging agents, with the sugar moiety anchoring the bioactive cargo to cancer cells. On the other hand, high demand for sugar nutrients in cancers provided a new avenue to target cancer cells with metabolic or sugar uptake inhibitors to induce cancer cells starvation or death. This overview summarizes recent advances in targeting cancer cells through sugar transport for cancer detection and therapy.

An Investigation of the Usability of Solid Lipid Nanoparticles Radiolabelled with Tc-99m as Imaging Agents in Liver-Spleen Scintigraphy

In this work, solid lipid nanoparticles (SLNs) were prepared by microemulsion and ultrasonication methods in the first stage of the production process of 99mTc–SLNs, which is considered to be an alternative radiopharmaceutical for the liver-spleen scintigraphy within the nuclear medicine. The laser diffraction (LD) and X-ray diffraction (XRD) analysis showed that these particles were at nano scale and had β' polymorph structure, respectively. It was observed that there was no interaction between the solid lipid and the surfactant molecules by fourier transform infrared spectroscopy (FT-IR). The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were taken and seen that the SLNs were spherical and at nano scale. Thermogravimetric analysis (TGA) for stability confirmed that they were stable for temperature variations. In the second stage of the study, the SLNs were successfully labeled with 99mTc. The radiolabeling efficiency was found to be greater than %95 and in vivo studies were performed on experimental rabbits using scintigraphic methods. When the obtained images were examined, the uptake was observed in the heart, the lungs, the liver, and the spleen. It was concluded that SLNs labeled with 99mTc could be a selective imaging agent. It was asserted to be a new radiopharmaceutical, especially as an alternative to the 99mTc-labeled compounds used in the liver and spleen imaging in colloid scintigraphy.