Inflammatory monocyte-derived effector cells play an important role in the pathogenesis of numerous inflammatory diseases. However, no treatment option exists that is capable of modulating these cells specifically. We show that infused negatively charged, immune-modifying microparticles (IMPs), derived from polystyrene, microdiamonds, or biodegradable poly(lactic-co-glycolic) acid, were taken up by inflammatory monocytes, in an opsonin-independent fashion, via the macrophage receptor with collagenous structure (MARCO). Subsequently, these monocytes no longer trafficked to sites of inflammation; rather, IMP infusion caused their sequestration in the spleen through apoptotic cell clearance mechanisms and, ultimately, caspase-3–mediated apoptosis. Administration of IMPs in mouse models of myocardial infarction, experimental autoimmune encephalomyelitis, dextran sodium sulfate–induced colitis, thioglycollate-induced peritonitis, and lethal flavivirus encephalitis markedly reduced monocyte accumulation at inflammatory foci, reduced disease symptoms, and promoted tissue repair. Together, these data highlight the intricate interplay between scavenger receptors, the spleen, and inflammatory monocyte function and support the translation of IMPs for therapeutic use in diseases caused or potentiated by inflammatory monocytes.

Nitrogen vacancy (NV) centres in diamond are promising elemental blocks for quantum optics, spin-based quantum information processing and high-resolution sensing. However, fully exploiting the capabilities of these NV centres requires suitable strategies to accurately manipulate them. Here, we use optical tweezers as a tool to achieve deterministic trapping and three-dimensional spatial manipulation of individual nanodiamonds hosting a single NV spin. Remarkably, we find that the NV axis is nearly fixed inside the trap and can be controlled in situ by adjusting the polarization of the trapping light. By combining this unique spatial and angular control with coherent manipulation of the NV spin and fluorescence lifetime measurements near an integrated photonic system, we demonstrate individual optically trapped NV centres as a novel route for both three-dimensional vectorial magnetometry and sensing of the local density of optical states.

Control over the quantum states of individual luminescent nitrogen-vacancy (NV) centres in nanodiamonds (NDs) is demonstrated by careful design of the crystal host: its size, surface functional groups, and interfacing substrate. By progressive etching of the ND host, the NV centres are induced to switch from latent, through continuous, to intermittent or "blinking" emission states. The blinking mechanism of the NV centre in NDs is elucidated and a qualitative model proposed to explain this phenomenon in terms of the centre electron(s) tunnelling to acceptor site(s). These measurements suggest that the substrate material and its proximity to the NV are responsible for the fluorescence intermittency.

The nitrogen vacancy (NV) center is the most widely studied single optical defect in diamond with great potential for applications in quantum technologies. Development of practical single-photon devices requires an understanding of the emission under a range of conditions and environments. In this work, we study the properties of a single NV center in nanodiamonds embedded in an air-like silica aerogel environment which provides a new domain for probing the emission behavior of NV centers in nanoscale environments. In this arrangement, the emission rate is governed primarily by the diamond crystal lattice with negligible contribution from the surrounding environment. This is in contrast to the conventional approach of studying nanodiamonds on a glass coverslip. We observe an increase in the mean lifetime due to the absence of a dielectric interface near the emitting dipoles and a distribution arising from the irregularities in the nanodiamond geometry. Our approach results in the estimation of the mean quantum efficiency (~0.7) of the nanodiamond NV emitters.