Surfaceimmobilized

Surface immobilized refers to the attachment and retention of molecules, enzymes, cells, or particles on a solid support so they remain fixed on or near a surface. This approach is widely used to create reusable catalysts, diagnostic assays, and sensing platforms. The immobilized species can include proteins, DNA, antibodies, or microorganisms, and the choice of surface ranges from inorganic substrates (glass, silica, gold) to organic polymers and composite coatings.

Common immobilization methods include physical adsorption, where molecules adhere by van der Waals, electrostatic, or hydrophobic interactions; covalent binding, which links functional groups (amines, carboxyls, thiols) through cross-linkers or surface chemistries such as NHS/EDC, glutaraldehyde, or silanization; and affinity-based approaches, which exploit specific interactions like biotin-streptavidin or His-tag/Ni-NTA. Entrapment in hydrogels or sol-gel matrices and the use of self-assembled monolayers to present reactive groups are also employed. Orientation control can be pursued to enhance activity, using site-specific coupling or engineered linkers.

Surfaces and characterization are important considerations. Common substrates include glass, silica, gold, and polymer films. Analytical techniques such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry, surface plasmon resonance (SPR), and quartz crystal microbalance (QCM) help quantify immobilization, activity, and stability.

Applications span biosensors, immunoassays, DNA microarrays, and biocatalysis, as well as coatings for medical devices and bioseparations. Advantages of surface immobilization include enhanced stability, reusability, and ease of separation, while challenges include potential activity loss, diffusion limitations, non-specific binding, and cost considerations.