The surface modification of polyethylene glycol PEG can significantly affect the adsorption of protein molecules. PEG is a hydrophilic polymer that is widely used in various biomedical applications, including drug delivery systems and surface coatings for medical devices. One of the main reasons for using PEG in these applications is its ability to resist protein adsorption, which is crucial for preventing biofouling and maintaining the biocompatibility of the materials.The adsorption of protein molecules onto a surface is influenced by various factors, including surface chemistry, surface topography, and the properties of the protein itself. By modifying the surface of PEG, we can alter these factors and thus control the adsorption of protein molecules. Some common surface modifications of PEG include:1. Molecular weight: The molecular weight of PEG can affect its conformation and chain length, which in turn influences the protein adsorption. Generally, higher molecular weight PEGs have a more extended conformation and provide better steric hindrance, leading to reduced protein adsorption.2. Grafting density: The grafting density refers to the number of PEG chains attached to a surface per unit area. Higher grafting densities can lead to a more effective "brush-like" structure that provides better steric hindrance and reduces protein adsorption. However, if the grafting density is too high, it may cause the PEG chains to collapse onto the surface, reducing their effectiveness in preventing protein adsorption.3. End-group functionalization: The end groups of PEG chains can be functionalized with various chemical groups, such as carboxyl, amine, or thiol groups. These functional groups can interact with the protein molecules through electrostatic, hydrogen bonding, or covalent interactions, affecting the adsorption behavior. Depending on the type of functional group and its interaction with the protein, the adsorption can be either enhanced or reduced.4. Copolymerization: PEG can be copolymerized with other monomers to create block or random copolymers with different surface properties. The presence of additional monomers can alter the hydrophilicity, charge, and topography of the surface, which can affect protein adsorption. For example, incorporating hydrophobic monomers may increase protein adsorption, while adding charged monomers may create electrostatic repulsion, reducing adsorption.5. Surface patterning: Patterning the PEG surface with nano- or micro-scale features can also influence protein adsorption. The presence of patterns can create regions with varying surface properties, which can either promote or inhibit protein adsorption depending on the specific pattern and protein.In summary, the surface modification of polyethylene glycol can significantly affect the adsorption of protein molecules by altering the surface chemistry, topography, and conformation of the PEG chains. By carefully selecting the appropriate surface modifications, it is possible to control protein adsorption and optimize the performance of PEG-based materials in various biomedical applications.