An unexplored remarkable PNIPAM-osmolyte interaction study: An integrated experimental and simulation approach

Area of Science:

• Polymer Science
• Biophysical Chemistry
• Materials Science

Background:

• Poly(N-isopropylacrylamide) (PNIPAM) is a water-soluble polymer exhibiting a coil-to-globular transition.
• Understanding the factors influencing PNIPAM's phase transition is crucial for developing smart materials.
• Osmolytes are known to affect protein and polymer behavior in aqueous solutions.

Purpose of the Study:

• To investigate the effect of trehalose, sucrose, and sorbitol on the aggregation and collapse of PNIPAM.
• To determine how these osmolytes influence the lower critical solution temperature (LCST) of PNIPAM.
• To elucidate the molecular mechanisms behind osmolyte-induced changes in PNIPAM conformation and hydration.

Main Methods:

• Comprehensive biophysical techniques including UV-visible spectroscopy, fluorescence spectroscopy, dynamic light scattering, and FTIR spectroscopy.
• Molecular dynamics (MD) simulations to probe molecular interactions and conformational changes.
• Variable concentrations of osmolytes (trehalose, sucrose, sorbitol) in aqueous PNIPAM solutions.

Main Results:

• Osmolytes significantly decrease the LCST of PNIPAM, promoting its collapsed state at lower temperatures.
• Increased osmolyte concentration leads to a pronounced decrease in PNIPAM's LCST due to altered polymer-osmolyte-water interactions.
• MD simulations confirm reduced polymer hydration and significant conformational changes, supporting experimental observations.

Conclusions:

• Osmolytes destabilize the hydrated structure of PNIPAM through preferential interactions, leading to a lower LCST.
• The observed phase transition is driven by the rupture of hydrogen bonds and hydrophobic association of PNIPAM chains.
• This study offers a method to tune PNIPAM's LCST for applications in bioresponsive devices near body temperature.