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  1. Autophagy is a cellular process with important functions that drive neurodegenerative diseases and cancers. Lysosomal hyperacidification is a hallmark of autophagy. Lysosomal pH is currently measured by fluorescent probes in cell culture, but existing methods do not allow for quantitative, transient or in vivo measurements. In the present study, we developed near-infrared optical nanosensors using organic color centers (covalent sp3 defects on carbon nanotubes) to measure autophagy-mediated endolysosomal hyperacidification in live cells and in vivo. The nanosensors localize to the lysosomes, where the emission band shifts in response to local pH, enabling spatial, dynamic and quantitative mapping of subtle changes in lysosomal pH. Using the sensor, we observed cellular and intratumoral hyperacidification on administration of mTORC1 and V-ATPase modulators, revealing that lysosomal acidification mirrors the dynamics of S6K dephosphorylation and LC3B lipidation while diverging from p62 degradation. This sensor enables the transient and in vivo monitoring of the autophagy–lysosomal pathway. 
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    Free, publicly-accessible full text available December 1, 2024
  2. Mid-infrared photonic integrated circuits (PICs) that combine on-chip light sources with other optical components constitute a key enabler for applications such as chemical sensing, light detection, ranging, and free-space communications. In this paper, we report the monolithic integration of interband cascade lasers emitting at 3.24 µm with passive, high-index-contrast waveguides made of chalcogenide glasses. Output from the chalcogenide waveguides exhibits pulsed peak power up to 150 mW (without roll-over), threshold current density 280 A/cm2, and slope efficiency 100 mW/A at 300 K, with a lower bound of 38% efficiency for coupling between the two waveguides. These results represent an important step toward the realization of fully integrated mid-infrared PICs.

     
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  3. Abstract

    Chemical defects that fluoresce in the shortwave infrared open exciting opportunities in deep-penetration bioimaging, chemically specific sensing, and quantum technologies. However, the atomic size of defects and the high noise of infrared detectors have posed significant challenges to the studies of these unique emitters. Here we demonstrate high throughput single-defect spectroscopy in the shortwave infrared capable of quantitatively and spectrally resolving chemical defects at the single defect level. By cooling an InGaAs detector array down to −190 °C and implementing a nondestructive readout scheme, we are able to capture low light fluorescent events in the shortwave infrared with a signal-to-noise ratio improved by more than three orders-of-magnitude. As a demonstration, we show it is possible to resolve individual chemical defects in carbon nanotube semiconductors, simultaneously collecting a full spectrum for each defect within the entire field of view at the single defect limit.

     
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