Table 4.

Examples of OR immobilization methods for OR-based biosensors.

Methods	Advantages	Disadvantages
Physical adsorption	Regent-free/low cost, simple to perform, non-destructive toward ORs	Insufficient binding strength, nonspecific adsorption, low stability
Self-assembly with specific antibodies	Higher specificity/affinity, higher stability, minimizing additional purification processes	unsuitability for sandwich assays, additional process for antibody immobilization
Covalent binding	Strong/irreversible binding force, high uniformity, controlled immobilization	Longer incubation time, conformational changes, loss of ligand specificity