Fluorescence bioimaging utilizing the near infrared-II (NIR-II; 1000 – 1700 nm) window, also named shortwave infrared (SWIR) imaging, exhibits superior penetration depth and signal-to-noise ratio compared to NIR-I imaging. We synthesized and characterized multiple lead sulfide/cadmium sulfide (PbS/CdS) core/shell quantum dots (QDs) with distinct, monodisperse size distributions, narrow emission, high quantum yield, and photostability for use in multiplexed NIR-II imaging. Following micelle encapsulation, the QDs are water-soluble, stably dispersed, and functionalized for easy click chemistry conjugation with targeting moieties. In vivo mice imaging with IV injected QDs showed very strong and distinctive signals for multiplexed imaging.

We detail the design and optimization of a set of multicoordinating ligands that combine the benefits of mixed coordination (thiol and imidazole) with molecular-scale zwitterion motifs, yielding sterically stabilized and compact nanocrystals. Conjugating the resulting QDs to anti-tropomyosin receptor kinase B antibody (α-TrkB), or to the brain-derived neurotrophic factor (BDNF), has allowed successful labeling of the tropomyosin receptor kinase B (TrkB) in pyramidal neurons within cortical tissue. It has also allowed visual monitoring of BDNF-induced activation of TrkB signaling in live neuronal cells.

Antibiotic-resistant infections (ARIs) are a growing public health threat, and nanomaterial-based medicines present a solution due to their unique method of action that is unlikely to develop an evolutionary defense. We synthesize biodegradable, non-toxic bornite nanocrystals (NCs) that possess an LSPR peak at 1100nm. We coat these NCs with a generalized targeting peptide and demonstrate their lethality to multiple bacteria species. Finally, we show that these particles degrade in vitro and are non-toxic to mammalian cells at a high concentrations, showing the potential of these NCs as antibacterial agents.

Luciferase-quantum dot (QD) conjugates enable excitation-free in vitro and in vivo imaging, but their use as sensors has been limited due to the use of randomly oriented conjugation strategies. We have developed an N-terminal specific conjugation strategy to orient NanoLuc luciferase on zwitterionic polymer-coated infrared QDs using a recently demonstrated 6-(azidomethyl)-2-pyridinecarbaldehyde-mediated azide labeling reaction. Using this strategy, we insert enzyme substrate peptide sequences between the luciferase and QD enabling detection of cleavage enzyme activity through bioluminescence resonance energy transfer (BRET). We optimized and characterized these sensor constructs and demonstrate their ability to access enzyme activity.

The biodegradation and excretion of biocompatible semiconductor nanoparticles could avoid problematic bioaccumulation and enable translational applications that utilize their unique optoelectronic properties. Through our studies of ternary copper sulfide-based nanoparticles, we have identified compositions that exhibit useful optical properties while also degrading into benign, bioessential components. Comparison to toxic compositions provides insight into the structure-function relationship between composition, degradation rate, and toxicity. Considering biocompatibility even before the optical properties are optimized ensures that development favors compositions that are most appropriate for longitudinal in vivo studies.

LiYF₄ nanocrystals (NCs) doped with 1% and 10% of Yb³⁺ and capped with oleic-acid were synthesized via a previously reported and modified co-precipitation method. Size, morphology, composition, and colloidal stability of these NCs are reported with data obtained from TEM, XRD, TGA/DSC, XRF, and zeta potential techniques. TEM analysis shows a monodisperse size distribution, with the nanocrystal size of ~20 nm. Optical characterization is described using data collected from UV-Vis-NIR absorption spectrophotometry and photoluminescence spectroscopy. The excellent luminescence in the NIR-II spectral region makes these NCs potential candidate for bioimaging applications.