Computational modeling of poly(alkylthiophene) conductive polymer insertion into phospholipid bilayers

Area of Science:

• Materials Science
• Biophysics
• Computational Chemistry

Background:

• Poly(alkylthiophenes) (PATs) have shown potential to increase the electrical conductance of phospholipid bilayers.
• This conductivity enhancement is hypothesized to stem from the ability of PAT side chains to insert into bilayers.
• The development of intracellular electrodes based on this phenomenon has been proposed.

Purpose of the Study:

• To investigate the insertion of two model PATs into a lipid bilayer using molecular dynamics.
• To determine the free-energy changes associated with PAT insertion.
• To evaluate the feasibility of using PATs for intracellular electrode applications.

Main Methods:

• Utilized steered molecular dynamics to simulate PAT insertion trajectories.
• Employed umbrella sampling to calculate the free-energy change upon insertion.
• Studied the behavior of branched-side-chain poly(3-(2-ethylhexyl)thiophene) (EHPT) and straight-side-chain poly(3-hexylthiophene) (HPT).

Main Results:

• Both EHPT and HPT penetrated the lipid bilayer.
• Only EHPT successfully crossed the membrane's center to form an electrical bridge.
• HPT penetrated the head groups but not the alkyl tail phase.

Conclusions:

• Branched-side-chain EHPT's ability to bridge the lipid bilayer supports the concept of long-term intracellular electrodes.
• The findings suggest branched side chains enhance PAT solubility within lipid bilayers.
• This study establishes a novel framework for similar systems and highlights EHPT's promise for biosensing and neural interfacing.