Single-Nanocrystal Studies on the Homogeneity of the Optical Properties of NaYF4:Yb3+,Er3

Bioimaging with Upconversion Nanoparticles

Bioimaging enables the spatiotemporal visualization of biological processes at various scales empowered by a range of different imaging modalities and contrast agents. Upconversion nanoparticles (UCNPs) represent a distinct type of such contrast agents with the potential to transform bioimaging due to their unique optical properties and functional design flexibilities. This review explores and discusses the opportunities, challenges, and limitations that UCNPs exhibit as bioimaging probes and highlights applications with spatial dimensions ranging from the single nanoparticle level to cellular, tissue, and whole animal imaging. We further summarized recent advancements in bioimaging applications enabled by UCNPs, including super-resolution techniques and multimodal imaging methods, and provide a perspective on the future potential of UCNP-based technologies in bioimaging research and clinical translation. This review may provide a valuable resource for researchers interested in exploring and applying UCNP-based bioimaging technologies.

Red Light Optogenetics in Neuroscience

Optogenetics, a field concentrating on controlling cellular functions by means of light-activated proteins, has shown tremendous potential in neuroscience. It possesses superior spatiotemporal resolution compared to the surgical, electrical, and pharmacological methods traditionally used in studying brain function. A multitude of optogenetic tools for neuroscience have been created that, for example, enable the control of action potential generation via light-activated ion channels. Other optogenetic proteins have been used in the brain, for example, to control long-term potentiation or to ablate specific subtypes of neurons. In in vivo applications, however, the majority of optogenetic tools are operated with blue, green, or yellow light, which all have limited penetration in biological tissues compared to red light and especially infrared light. This difference is significant, especially considering the size of the rodent brain, a major research model in neuroscience. Our review will focus on the utilization of red light-operated optogenetic tools in neuroscience. We first outline the advantages of red light for in vivo studies. Then we provide a brief overview of the red light-activated optogenetic proteins and systems with a focus on new developments in the field. Finally, we will highlight different tools and applications, which further facilitate the use of red light optogenetics in neuroscience.

Safety and efficacy of citric acid-upconverting nanoparticles for multimodal biological imaging in BALB/c mice

There has been significant progress with rare-earth coated upconversion nanoparticles (UCNPs) representing a promising new generation of contrast agents for biomedical applications. However, in vivo biological safety remains poorly investigated. This work examined citric acid-UCNP (NaYF4:Yb³⁺/Gd³⁺, ∼ 5 nm, Cit-UCNP) generated as contrast agents for multimodal imaging with concurrent magnetic resonance (MRI) and X-ray computed tomography (CT). We first examined the in vitro cytotoxicity and efficacy of Cit-UCNPs as a contrast agent. We then performed a systematic investigation of their in vivo biodistribution and biocompatibility. Our results noted that Cit-UCNPs have minimal toxicity and demonstrated significant potential as contrast agents for multimodal biomedical imaging. This study indicates Cit-UCNPs could be a valuable addition to enhance long-term targeted diagnostic and prognostic multimodal clinical imaging approaches.