Sigma-2 receptor-targeted functionalized carbon dots enable selective Fe³⁺ detection and cellular imaging

Area of Science:

• Nanomaterials Science
• Biomedical Engineering
• Analytical Chemistry

Background:

• Carbon dots (CDs) are emerging nanomaterials with unique optical and electronic properties.
• Nitrogen doping enhances the photoluminescence and functionality of carbon dots.
• Developing selective and sensitive probes for metal ion detection is crucial in environmental and biological monitoring.

Purpose of the Study:

• To synthesize and characterize photoluminescent nitrogen-doped carbon dots (N-CD_ISQ) functionalized with a sigma-2 receptor pharmacophore.
• To evaluate the in vitro biosensing performance of N-CD_ISQ for Fe³⁺ detection.
• To assess the biocompatibility and cellular imaging potential of N-CD_ISQ.

Main Methods:

• Synthesis of nitrogen-doped carbon dots (N-CD_ISQ) incorporating an isoquinoline moiety.
• Photoluminescence spectroscopy for optical characterization and Fe³⁺ sensing.
• Stern-Volmer kinetics analysis for quantitative Fe³⁺ determination.
• Biocompatibility assays including cell viability and haemolysis tests.
• Cellular imaging studies to visualize Fe³⁺ ions within cells.

Main Results:

• N-CD_ISQ exhibited intense blue photoluminescence (450 nm emission upon 350 nm excitation).
• Selective fluorescence quenching by Fe³⁺ was observed, following Stern-Volmer kinetics with a detection limit of 4.13 μM.
• N-CD_ISQ demonstrated good biocompatibility (cell viability >80%) and negligible haemolysis.
• Successful visualization of intracellular Fe³⁺ ions using N-CD_ISQ in cellular imaging experiments.

Conclusions:

• N-CD_ISQ represents a novel class of fluorescent probes for quantitative Fe³⁺ analysis.
• The synthesized N-CD_ISQ possesses dual functionality for sensing and cellular imaging.
• These nitrogen-doped carbon dots show promise for applications in biological sensing and diagnostics.