Quantification of insulin is essential for diabetes research in general, and for the study of pancreatic β‐cell function in particular. Herein, fluorescent single‐walled carbon nanotubes (SWCNT) are used for the recognition and real‐time quantification of insulin. Two approaches for rendering the SWCNT sensors for insulin are compared, using surface functionalization with either a natural insulin aptamer with known affinity to insulin, or a synthetic lipid‐poly(ethylene glycol) (PEG) (C16‐PEG(2000Da)‐Ceramide), both of which show a modulation of the emitted fluorescence in response to insulin. Although the PEGylated‐lipid has no prior affinity to insulin, the response of C16‐PEG(2000Da)‐Ceramide‐SWCNTs to insulin is more stable and reproducible compared to the insulin aptamer‐SWCNTs. The SWCNT sensors successfully detect insulin secreted by β‐cells within the complex environment of the conditioned media. The insulin is quantified by comparing the SWCNTs fluorescence response to a standard calibration curve, and the results are found to be in agreement with an enzyme‐linked immunosorbent assay. This novel analytical tool for real time quantification of insulin secreted by β‐cells provides new opportunities for rapid assessment of β‐cell function, with the ability to push forward many aspects of diabetes research.

These local changes in the levels of involved metabolites or products can indicate an ongoing process of a cancerous transformation, and even further contribute to its escalation, rendering them oncometabolites. [1][2][3][4][5][6][7][8][9] D-2-hydroxyglutarate (D2HG) is a product of the gain-of-function-mutated enzymes isocitrate dehydrogenase (IDH1/ IDH2), whereas the normal mitochondrial form plays a role in the tricarboxylic acid (TCA) cycle by producing α-ketoglutarate. [1,2,[4][5][6][7][8][9] Hence, an accumulation of D2HG in the mitochondria indicates a mutagenesis of isocitrate dehydrogenase (IDH) and interruption of the TCA cycle, implying that the cell is in a state of pseudo-hypoxia (resembling a state of low oxygen levels), and mainly relying on glycolysis for energy production (Scheme 1). [4] Normally, as a minor metabolic byproduct, D2HG levels are kept low as D-2-hydroxyglutarate dehydrogenase (D2HGDH) converts it to α-ketoglutarate. [1,10] However, D2HGDH does not prevent D2HG accumulation in the case of overproduction. [10] Moreover, a congenital loss of D2HGDH causes D2HG accumulation, which can lead to a severe brain damage in a rare condition called D-2-hydroxyglutarate aciduria. [1,10] The accumulation of D2HG was shown to inhibit a group of enzymes named a-ketoglutarate-dependent dioxygenases (aKGdd), resulting in the promotion of mutagenesis by epigenetic modification of DNA and histone hypermethylation. [1,4,5,7] Notably, IDH1-mutated tumors were shown to exhibit DNA hypermethylation in gliomas and leukemia, and also histone hypermethylation. [1,[5][6][7]9,11] Accumulation of 2-hydroxyglutarate (both D and L optical isomers) was found to suppress cell-proliferation regulation. [1,9] As a demonstration of D2HG cellular potency, it was shown that incubating hematopoietic stem cells with D2HG alters differentiation patterns and promotes immune resistance. [1,6] IDH mutations and D2HG accumulation were found in gliomas and glioblastomas, and D2HG accumulation is suspected to be sufficient for promoting the development of acute myeloid leukemia (AML). [1,6] Another possible oncogenic mechanism linked to D2HG abundance, is its ability to shift cellular redox equilibrium toward overproduction of reactive oxygen species (ROS), which are well-known oncogenic agents. [4] The same mechanism was also found to impair immune antitumor activity. [1,8] The production of oncometabolites is the direct result of mutagenesis in key cellular metabolic enzymes, appearing typically in cancers such as glioma, leukemia, and glioblastoma. Once accumulated, oncometabolites promote cancerous transformations by interfering with important cellular functions. Hence, the ability to sense and quantify oncometabolites is essential for cancer research and clinical diagnosis. Here, the authors present a near-infrared optical nanosensor for a known oncometabolite, D-2-hydroxyglutarate (D2HG), discovered in a screening of a library of fluorescent single-walled carbon nanotubes (SWCNTs) functionalized with ssDNA. The screening r...

Super resolution microscopy methods have been designed to overcome the physical barrier of the diffraction limit and push the resolution to nanometric scales. A recently developed super resolution technique, super-resolution radial fluctuations (SRRF) [Nature communications, 7, 12471 (2016)10.1038/ncomms12471], has been shown to super resolve images taken with standard microscope setups without fluorophore localization. Herein, we implement SRRF on emitters in the near-infrared (nIR) range, single walled carbon nanotubes (SWCNTs), whose fluorescence emission overlaps with the biological transparency window. Our results open the path for super-resolving SWCNTs for biomedical imaging and sensing applications.

Single‐walled carbon nanotubes (SWCNTs) have unique optical and physical properties, with numerous biomedical imaging and sensing applications, owing to their near‐infrared (nIR) fluorescence which overlaps with the biological transparency window. However, their longer emission wavelengths compared to emitters in the visible range result in a lower resolution due to the diffraction limit. Moreover, the elongated high‐aspect‐ratio structure of SWCNTs poses an additional challenge on super‐resolution techniques that assume point emitters. Utilizing the advantages of deep learning and convolutional neural networks, along with the super‐resolution radial fluctuation (SRRF) algorithm for network training, a fast, parameter‐free, computational method is offered for enhancing the spatial resolution of nIR fluorescence images of SWCNTs. An average improvement of 22% in the resolution and 47% in signal‐to‐noise ratio (SNR) compared to the original images is shown, whereas SRRF leads to only 24% SNR improvement. The approach is demonstrated for a variety of SWCNT densities and length distributions, and a wide range of imaging conditions with challenging SNRs, including real‐time videos, without compromising the temporal resolution. The results open the path for accelerated and accessible super‐resolution of nIR fluorescent SWCNTs images, further advancing their applicability as nanoscale optical probes.

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