Temperature is an essential parameter in all biological systems, but information about the actual temperature in living cells is limited. Especially, in photothermal therapy, local intracellular temperature changes induce cell death but the local temperature gradients are not known. Highly sensitive nanothermometers would be required to measure and report local temperature changes independent of the intracellular environment, including pH or ions. Fluorescent nanodiamonds (ND) enable temperature sensing at the nanoscale independent of external conditions. Herein, we prepare ND nanothermometers coated with a nanogel shell and the photothermal agent indocyanine green serves as a heat generator and sensor. Upon irradiation, programmed cell death was induced in cancer cells with high spatial control. In parallel, the increase in local temperature was recorded by the ND nanothermometers. This approach represents a great step forward to record local temperature changes in different cellular environments inside cells and correlate these with thermal biology.

Measuring certain quantities at the nanoscale is often limited to strict conditions such as low temperature or vacuum. However, the recently developed nanodiamond (ND) quantum sensing technology shows great promise for ultrasensitive diagnosis and probing subcellular parameters at ambient conditions. Atom defects (i.e., N, Si) within the ND lattice provide stable emissions and sometimes spin-dependent photoluminescence. These unique properties endow ND quantum sensors with the capacity to detect local temperature, magnetic fields, electric fields, or strain. In this review, some of the recent, most exciting developments in the preparation and application of ND sensors to solve current challenges in biology and medicine including ultrasensitive detection of virions and local sensing of pH, radical species, magnetic fields, temperature, and rotational movements, are discussed.

Nanostructure-based functions are omnipresent in nature and essential for the diversity of life. Unlike small molecules, which are often inhibitors of enzymes or biomimetics with established methods of elucidation, we show that functions of nanoscale structures in cells are complex and can implicate systemlevel effects such as the regulation of energy and redox homeostasis. Herein, we design a platinum(II)-containing tripeptide that assembles into intracellular fibrillar nanostructures upon molecular rearrangement in the presence of endogenous H 2 O 2 . The formed nanostructures blocked metabolic functions, including aerobic glycolysis and oxidative phosphorylation, thereby shutting down ATP production. As a consequence, ATP-dependent actin formation and glucose metabolite-dependent histone deacetylase activity are downregulated. We demonstrate that assembly-driven nanomaterials offer a rich avenue to achieve broad-spectrum bioactivities that could provide new opportunities in drug discovery.

Fluorescent nanodiamonds (fNDs) are unique carbon-based nanomaterials due to their outstanding optical and magnetic properties. However, realization of the full potential of fNDs is often limited by their processability because fNDs aggregate strongly in both organic and aqueous solutions. Therefore, robust and potentially universal coating strategies are urgently needed to address these limitations. Derived from mussel foot proteins, the polymerization of l-3,4-dihydroxyphenylalanine (l-DOPA) provides important surface functional groups including amines, carboxylic acid, alcohols, and conjugated Michael acceptors. Herein, l-DOPA is polymerized on fNDs with a high control over the shell thickness. Photoluminescence and optically detected magnetic resonance studies reveal that the unique photophysical properties of fNDs are preserved after thin poly(l-DOPA) film coating. Subsequently, conjugation of transferrin, a heme protein that provides efficient receptor-specific cellular transport, improves the colloidal stability and cellular uptake of the poly(l-DOPA)-coated fNDs. The loading of FDA-approved indocyanine green as a photothermal agent yields an integrated biohybrid material exhibiting an amplified photothermal effect in cells at very low energy intake (≈90 mW cm −2 ).

Long-term tracking of nanoparticles to resolve intracellular structures and motions is essential to elucidate fundamental parameters as well as transport processes within living cells. Fluorescent nanodiamond (ND) emitters provide cell...