Context:

Scientists from the Institute of Advanced Study in Science and Technology (IASST) in Guwahati have successfully fabricated lysozyme bilayers on hydrophilic and hydrophobic silicon surfaces at room temperature.

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This breakthrough mimics the natural protein adsorption process found in living organisms, providing valuable insights into ion-mediated protein interactions on implants and biomaterials.

• Protein adsorption refers to the process where proteins accumulate and adhere to a surface without penetrating it.

The IASST research team focused on fabricating lysozyme bilayers in the presence of monovalent (Na+), divalent (Ca2+), and trivalent (Y3+) ions.

• This resulted in ion-mediated lysozyme adsorption, which closely resembles the biological adsorption of protein in living organisms.

Role of Ions in Adsorption: Ions, which regulate various biological processes such as electrochemical potential and fluid balance, are central to protein-surface interactions when implants are introduced into a living body. 

Lysozyme Bilayer Structure: The researchers successfully formed bilayers comprising a bottom layer with side-on orientation and an upper layer with side-on or tilted orientations. 

• The stabilization mechanism relied on modified hydrogen bonding, hydrophobic interactions, and electrostatic forces in an ionic environment.

The study revealed that lysozyme-lysozyme interactions compete with lysozyme-surface interactions, leading to protein adsorption in its native globular form on the hydrophilic surface and a slightly elongated structure on the hydrophobic surface.

The researchers observed that a higher contact angle (a measure of surface interaction) was seen with a greater number of lysozyme molecules in the bilayer film.

Implications for Biomaterials and Implants

• The ability to replicate ion-mediated protein adsorption on implant surfaces offers promising applications in biomaterial design. 
• The study provides a model for understanding how proteins behave in ionic environments, critical for improving the biocompatibility and functionality of medical implants.

Lysozyme

• Lysozyme is an enzyme that plays a crucial role in the body's immune system. 
• It is found in various secretions such as tears, saliva, mucus, and egg whites.
• Function: Lysozyme helps protect the body by breaking down the cell walls of bacteria. It does this by hydrolyzing (breaking down) the glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, which is a major component of bacterial cell walls. This process weakens the bacterial cell walls, leading to the bacteria's destruction.
• It features four disulfide bonds and is widely studied for its structural stability and biological relevance.

Hydrophilic Surfaces

• Water Loving: Hydrophilic means "water-loving." These surfaces attract water molecules.
• Examples: Glass, clean metal surfaces, and materials treated with hydrophilic coatings.

Hydrophobic Surfaces

• Water Repelling: Hydrophobic means "water-fearing." These surfaces repel water molecules.
• Examples: Teflon, wax-coated surfaces, and lotus leaves.