Graft-then-Shrink Polymer Coatings for Localized Surface Plasmon Resonance Active Interfaces

Area of Science:

• Materials Science
• Biotechnology
• Nanotechnology

Background:

• Increasing polymer content on biosensors enhances surface properties and analyte capture site density.
• Traditional grafting-to methods may suffer from limited polymer immobilization.
• Local Surface Plasmon Resonance (LSPR) biosensors offer sensitive detection but require optimized surface functionalization.

Purpose of the Study:

• To develop a novel method, Graft-then-Shrink (GtS), for simultaneously increasing polymer content and fabricating LSPR Au biosensors.
• To utilize these biosensors for tracking the translocation of molecules across biological barriers.
• To demonstrate the efficacy of GtS in producing functional biosensors for screening and kinetic studies.

Main Methods:

• Utilized Graft-then-Shrink (GtS) technique on stretched polystyrene (PS) substrates coated with thiol-terminated polymers.
• Fabricated LSPR active wrinkled Au layers by heating, increasing polymer content and reducing water contact angles (WCA).
• Incorporated GtS biosensors into 3D printed microwell plates with phospholipid bilayers to demonstrate translocation detection via visible light absorbance shifts.

Main Results:

• GtS coatings exhibited approximately 78% greater polymer content compared to Shrink-then-Graft (StG) controls.
• GtS biosensors showed significantly lower water contact angles (WCA ≈ 15°) than StG controls (WCA ≈ 55°).
• Successfully screened cell-penetrating peptides (CPPs) for phospholipid bilayer translocation and measured rate kinetics using LSPR peak shifts.

Conclusions:

• GtS is a simple and effective method for significantly increasing polymer content in biosensor coatings.
• The GtS fabrication platform enables low-cost, localized LSPR biosensors for tracking biomolecule translocation.
• This approach provides a versatile tool for studying molecular transport across biological barriers.