Cell Imaging Using Two-Photon Excited CdS Fluorescent Quantum Dots Working within the Biological Window

Abstract

In recent years, two-photon excited semiconductor quantum dots (QDs) have been the subject of intense investigation due to their long excitation wavelength which helps to achieve deeper penetration and higher image resolution in optical bioimaging. In this paper, water-soluble CdS QDs were synthesized using a hydrothermal method and applied to human liver hepatocellular carcinoma (HepG2) cells. The first-principles calculation suggested that the S-rich defected structure contributes to a narrower band gap compared to the pristine structure. The resulting fluorescence wavelength was significantly red shifted, which was attributed to the deep defect states emission. The large Stokes shifts (> 200 nm) of the QDs can eliminate the possible cross-talk between the excitation light and the emission light. Two-photon induced red fluorescence emission can avoid overlapping with the autofluorescence emission of biological samples. The uptake and cell viability measurements of the HepG2 cells showed a good biocompatibility and a low toxicity of CdS QDs. Two-photon excited scanning microscopy images revealed that the HepG2 cells incubated with CdS QDs emitted bright red upconversion fluorescence and the fluorescence brightness was 38.2 times of that of the control group. These results support CdS QDs as a good candidate for application in cellular imaging.

Visible/Near-Infrared Emitting, Garnet-Based Paramagnetic-Persistent Luminescent Nanocrystals for Two-Photon Bioimaging

“…This limits the sensitivity of the nanoprobe as the visible photons are prone to scatter in the tissue. Therefore, efforts are made to develop nanoprobe and dyes capable of two-photon excited NIR emission in the region of 650–900 nm. ,, GAGG:CeCr-FA shows the ability of NIR to NIR two-photon excitation together with magneto persistence. Thus, the GAGG:CeCr nanoparticle has excellent potential as a multimodal platform for high contrast and high penetrating in vivo bioimaging.…”

Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods

“…Simultaneous absorption of two photons is of significant interest for a range of applications, particularly imaging, where higher spatial resolution and penetration depth can be achieved through the nonlinear photon-flux dependence of two-photon absorption (2PA) processes. − 2PA is particularly useful in biological imaging due to increased transmissivity of biological tissue in the near-IR spectral window, so 2PA improves imaging resolution and penetration depth. 2PA cross sections are measured in units of GM where 1 GM = 1 Göppert Mayer = 10 –50 cm 4 s photon –1 .…”

Induction of autophagy and endoplasmic reticulum autophagy caused by cadmium telluride quantum dots are protective mechanisms of yeast cell

“…The narrow emission spectrum of QDs make it possible to detect the different sizes of QDs under the same excitation (Kairdolf et al, 2013; Zhang et al, 2003). Therefore, QDs are applied in various application ranging from light‐emitting devices to imaging (Byers & Hitchman, 2011; Jaiswal & Simon, 2004; Onoshima et al, 2015; Zhang et al, 2019; Zvaigzne et al, 2020) and are considered to be potential chemical probes in biological applications. Numerous studies have reported the use of QDs for in vivo imaging of cell membrane, organelles, and receptors (Awasthi et al, 2020; Chan et al, 2002; Le et al, 2020) and for tumor detection (Diagaradjane et al, 2008; Gao et al, 2004; Salama et al, 2020).…”