Integrated and compact fiber-coupled single-photon system based on nitrogen-vacancy centers and gradient-index lenses

A fiber-coupled single-photon system is presented. Gradient-index lenses are utilized for single-photon collection and fiber coupling of a nitrogen-vacancy defect center in a nanodiamond. Integrated filter technology separates excitation and laser light. Therefore, the system is ultracompact with 120 mm(3) in dimension as no bulky free beam optics are used. The commercial availability of all components and their simple assembly allows the implementation of a low-cost single-photon system, possibly approaching single-photon count rates of 500 kcts/s.     

Fluorogenic Granzyme A Substrates Enable Real-Time Imaging of Adaptive Immune Cell Activity

Cytotoxic immune cells, including T lymphocytes (CTLs) and natural killer (NK) cells, are essential components of the host response against tumors. CTLs and NK cells secrete granzyme A (GzmA) upon recognition of cancer cells; however, there are very few tools that can detect physiological levels of active GzmA with high spatiotemporal resolution. Herein, we report the rational design of the near-infrared fluorogenic substrates for human GzmA and mouse GzmA. These activity-based probes display very high catalytic efficiency and selectivity over other granzymes, as shown in tissue lysates from wild-type and GzmA knock-out mice. Furthermore, we demonstrate that the probes can image how adaptive immune cells respond to antigen-driven recognition of cancer cells in real time.