Design of surfaces for liquid crystal-based bioanalytical assays

Area of Science:

• Biomolecular analysis
• Surface science
• Liquid crystal technology

Background:

• Surface-induced ordering of liquid crystals (LCs) provides a label-free method for detecting surface-bound biomolecules.
• The orientation-dependent anchoring energy of LCs is sensitive to surface-bound molecules and quantifiable.

Purpose of the Study:

• To analyze twisted nematic LC systems to identify optimal surface anchoring energies for LC-based analytical methods.
• To demonstrate precise fabrication of analytic surfaces with specific anchoring energies.
• To characterize the influence of surface anchoring energy on LC response to protein analytes.

Main Methods:

• Analysis of a simple model of twisted nematic LC systems.
• Fabrication of analytic surfaces using organothiols on gold films via physical vapor deposition at oblique angles.
• Characterization of LC response to surface-bound human epidermal growth factor receptor (EGFR) using (32)P-radiolabeling for quantification.

Main Results:

• Identified LC anchoring energies between 0.5 microJ/m(2) and 2.0 microJ/m(2) as optimal for LC-based analytical methods.
• Demonstrated precise fabrication of surfaces with anchoring energies within the optimal range (< 0.1 microJ/m(2)).
• Showed that LCs can report surface densities of EGFR from 30-40 pg/mm(2) on optimized surfaces.

Conclusions:

• Optimal surface anchoring energies for LC-based analytical systems were identified.
• Precise fabrication of these surfaces is achievable using organothiols on gold.
• This work guides the design of surfaces for sensitive, label-free detection of biomolecules.