Single-molecule porphyrin-metal ion interaction and sensing application

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Biophysics

Background:

• Studying metal ion-porphyrin interactions at the single-molecule level is challenging.
• Porphyrins, like 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (TPPS), are crucial in biological systems.
• Copper ions (Cu²⁺) play vital roles but their interactions with porphyrins require precise analytical methods.

Purpose of the Study:

• To develop a label-free, real-time nanopore-based sensing platform for analyzing Cu²⁺-TPPS interactions.
• To demonstrate the capability of the sensor for sensitive and selective Cu²⁺ detection.
• To validate the practical applicability of the sensing system.

Main Methods:

• Construction of a sensing system utilizing an α-hemolysin (α-HL) nanopore.
• Real-time monitoring of ionic current changes upon Cu²⁺ binding to TPPS within the nanopore.
• Analysis of distinct electronic signatures generated by the Cu²⁺-TPPS complex.

Main Results:

• Emergence of unique electronic signatures for the Cu²⁺-TPPS complex, differing from free TPPS.
• Highly sensitive detection of Cu²⁺ in aqueous media with a linear response from 0.03 µM to 1.0 µM.
• Achieved a detection limit of 16 nM (S/N = 3) with high selectivity against other metal ions.
• Successful determination of Cu²⁺ in running water samples.

Conclusions:

• The developed nanopore sensor provides a sensitive and selective method for real-time, label-free detection of Cu²⁺-TPPS interactions.
• The distinct electronic signatures observed are key to differentiating between free TPPS and its Cu²⁺ complex.
• This approach holds promise for practical applications in environmental monitoring and biological analysis.