A self-calibrating logic system and oxidase-based biosensor using Tb³⁺-doped carbon dots/DNA conjugates

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Developing novel fluorescent sensors is crucial for sensitive and selective detection of analytes.
• Carbon dots (CDs) and lanthanide ions offer unique photoluminescent properties for sensing applications.
• Ratiometric sensing provides enhanced stability and accuracy by using an internal reference signal.

Purpose of the Study:

• To develop a facile and cost-effective ratiometric fluorescent probe for detecting hydrogen peroxide (H₂O₂) and oxidase-related reactions.
• To create a self-calibrating logic system based on reversible fluorescence changes.
• To demonstrate the probe's applicability in biological samples like rat serum.

Main Methods:

• Synthesis of Tb³⁺-doped carbon dots (Tb³⁺@CDs) via a hydrothermal method.
• Conjugation of Tb³⁺@CDs with single-strand DNA (ssDNA) to form Tb³⁺@CDs/ssDNA.
• Utilizing the antenna effect for dual fluorescence emission from CDs and Tb³⁺.
• Investigating the reversible fluorescence response to Ag⁺ and Cys for logic system design.
• Applying the probe for ratiometric fluorescence detection of H₂O₂ and glucose via glucose oxidase (GOx).

Main Results:

• A Tb³⁺@CDs/ssDNA conjugate was successfully synthesized, exhibiting dual fluorescence at 444 nm (CDs) and 546 nm (Tb³⁺).
• The ratiometric fluorescence signal was reversibly modulated by Ag⁺ and Cys, enabling a logic system.
• The probe achieved sensitive detection of H₂O₂ and glucose (LOD: 0.06 μM for glucose).
• The sensing strategy was successfully applied to detect glucose in rat serum, showing good agreement with commercial kits.

Conclusions:

• A novel, cost-effective, and easy-to-prepare ratiometric fluorescent probe (Tb³⁺@CDs/ssDNA) was developed.
• The probe enables sensitive and selective detection of H₂O₂ and glucose, with potential for oxidase-related enzyme activity monitoring.
• The developed sensing strategy is robust, self-calibrating, and applicable in complex biological matrices.