Photocontrolled Liquid Crystal Droplets and Solution Tuning for Sub-nanomolar Protein Detection.

Area of Science:

• Biomolecular Interactions
• Materials Science
• Biosensing Technologies

Background:

• Liquid crystals (LCs) are crucial for biosensing, but their interaction with proteins is limited.
• The oleophilic nature of 4-cyano-4'-pentyl biphenyl (5CB) hinders direct interaction with hydrophilic proteins, impeding its sensing capabilities.

Purpose of the Study:

• To engineer the 5CB-aqueous interface for enhanced protein interaction and ultrasensitive detection.
• To understand the role of photoirradiation byproducts in modulating LC-aqueous interface properties.

Main Methods:

• Controlled UV-irradiation of 5CB to form amphiphilic byproducts like 4-cyano-4'-biphenyl carboxylate (CBA).
• Microfluidics used to create UV-5CB microemulsion droplets and observe defect configuration changes.
• Differential scanning calorimetry and small-angle X-ray scattering to analyze LC molecular packing.

Main Results:

• UV-irradiation of 5CB generates CBA, which adsorbs at the interface, imparting negative charge and altering droplet defect structures.
• Protein (myoglobin) binding induces a transition from radial to bipolar defect configuration via electrostatic interactions with CBA.
• Optimal UV-irradiation is critical; excessive exposure disrupts LC order and reduces sensitivity.
• Tuning buffer concentration and reducing droplet density achieved ultrasensitive protein detection (∼0.95 nM).

Conclusions:

• Controlled photoirradiation of 5CB can engineer LC-aqueous interfaces for ultrasensitive protein detection.
• The study provides fundamental insights into LC-protein interactions and interfacial modulation.
• This approach significantly advances LC-based biosensing platforms, paving the way for specific protein detection.