Quantum Cascade Laser-Based Vibrational Circular Dichroism Imaging for Chiral Biosensing.

Area of Science:

• Chiroptical spectroscopy
• Molecular spectroscopy
• Biophysical chemistry

Background:

• Vibrational circular dichroism (VCD) probes molecular chirality using differential infrared light absorption.
• Quantum cascade lasers (QCLs) offer high-power, narrowband mid-infrared sources, significantly boosting VCD sensitivity and speed.
• Previous VCD techniques lacked the resolution and speed for advanced imaging applications.

Purpose of the Study:

• To review the instrumental design of QCL-based VCD imaging systems.
• To demonstrate the application of QCL-VCD imaging for spatially resolved chiral biosensing.
• To highlight the potential of QCL-VCD for analyzing biological and clinical samples.

Main Methods:

• Utilizing QCLs for high-power, narrowband mid-IR light generation.
• Implementing polarization-modulation strategies for enhanced VCD signal detection.
• Developing micrometer-resolution mapping techniques for VCD imaging.

Main Results:

• QCL-VCD imaging achieves unprecedented sensitivity and speed.
• Spatially resolved detection of protein secondary structures is demonstrated.
• Enantiomeric purity of pharmaceuticals and pathological tissue features can be visualized without labels.

Conclusions:

• QCL-VCD imaging is a powerful tool for chiral analysis in biological and clinical settings.
• Overcoming challenges like birefringence and data processing is key for robust imaging.
• Future integration with nonlinear chiroptical techniques promises further advancements.