Two-Photon Dual-Emissive Carbon Dot-Based Probe: Deep-Tissue Imaging and Ultrasensitive Sensing of Intracellular Ferric Ions

Abstract

Carbon dots (CDs)-based nanoparticles have been extensively explored for biological applications in sensing and bioimaging. However, the major translational barriers to CDs for imaging and sensing applications include synthetic strategies to obtain monodisperse CDs with tunable structural, electronic, and optical properties in order to achieve high-resolution deep-tissue imaging, intracellular detection, and sensing of metal ions with high sensitivity down to nanomolar levels. Herein, we report a novel strategy to synthesize and develop a multifunctional nitrogen-doped CDs probe of different sizes using a new combination of carbon and nitrogen sources. Our results show that the structural characteristics (i.e., the surface density of emissive traps and bandgaps levels) depend on the size of the CDs, which ultimately influences their optical properties. This work also demonstrates the development of a two-photon dual-emissive fluorescent multifunctional probes (3-FCDs) by conjugating fluorescein isothiocyanate on the surface of nitrogen-doped CDs. 3-FCDs show excellent near-infrared two-photon excitation ability, single-wavelength excitation, high photostability, biocompatibility, low cytotoxicity, and good cell permeability. Using two-photon fluorescence imaging, our multifunctional probe shows excellent deep-tissue high-resolution imaging capabilities with penetration depth up to 3000 and 280 μm in hydrogel scaffold and pigskin tissue, respectively. The designed probe exhibits ultrasensitivity and specificity toward Fe3+ ions with a remarkable detection limit of 2.21 nM using two-photon excitation. In addition, we also demonstrate the use of multifunctional CDs probe for ultrasensitive exogenous and real-time endogenous sensing of Fe3+ ions and imaging in live fibroblasts with rapid response times for intracellular ferric ion detection.

High yield synthesis of graphene quantum dots from biomass waste as a highly selective probe for Fe3+ sensing

“…Owing to the presence of these functional groups and strong emission, these GQDs are expected to be an ideal candidate for fluorescence sensing. Among the various heavy metal ions, the detection and removal of Fe 3+ ions has always attracted extensive attention 53,92,93 . Generally, iron plays a key role in human life and its deficiency requires considerable attention among the global micronutrient deficiencies.…”

“…Moreover, the iron percentage has to be monitored and balanced in biological and environmental systems 94 . To achieve this, numerous researchers employed the quenching phenomenon of carbon QDs by the addition of Fe 3+4, 53,95 . The quenching percentage is related to the concentration of Fe 3+ .…”

Nonconjugated Biocompatible Macromolecular Luminogens for Sensing and Removals of Fe(III) and Cu(II): DFT Studies on Selective Coordination(s) and On‐Off Sensing

“…[ 36 ] To date, although few numbers of on‐off fluorescent polymeric luminogens have been reported as sensors of Cu(II) and Fe(III), such materials suffering from several drawbacks are not effective for multipurpose applications. [ 37,38 ]…”

The analytical and biomedical applications of carbon dots and their future theranostic potential: A review

“…In addition to the conventional down-conversion fluorescence emissions, certain C-dots are also found to display two and multi-photon fluorescence emission [110][111][112][113], with up-conversion fluorescence reported [114] (anti-Stokes shift PL), which is orders of magnitude higher in efficiency than conventional fluorophores [115,116].…”