## 4 Conductive Polymers
### Other Strategies for Enzyme Immobilization by Electrochemistry  
Non-conductive polymers are an emerging matrix for immobilizing biomolecules [152]. Studies have indicated that non-conductive polymers can also be prepared for enzyme immobilization through a one-step electrodeposition strategy. Films formed by non-conductive polymers are typically thinner than CP layers, resulting in faster substrate and product diffusion rates. Additionally, non-conductive polymers can prevent interference from electroactive substances in samples, offering advantages such as high sensitivity, rapid response time, and good reproducibility [153].  
The biopolymer composite material composed of enzymes, Nafion, and CPs exhibits excellent stability. Nafion, acting as a binder, ensures that enzymes adsorb extensively in a manner conducive to bioelectrocatalysis and prevents enzymes from detaching from the electrode surface. [PERSON] and her colleagues have reported a novel one-step synthesis method that relies on the co-deposition of oxidases (such as glucose oxidase or alcohol oxidase), Nafion(r)117, and palladium nanoparticles (Pd-NPs) through the electrochemical deposition of a phosphate multi-electrolyte. Biosensors prepared through this method exhibit significantly enhanced mechanical stability with virtually no loss of enzyme activity [154].  
Silicon dioxide (SiO\({}_{2}\)) films have attracted widespread interest as a material for enzyme immobilization due to their optical transparency and ease of preparation. [PERSON] et al. introduced a one-step electrochemical method on a platinum electrode to fabricate a glucose oxidase (GOD) biomaterial encapsulated within a porous sol-gel silicon dioxide matrix. The GOD encapsulated by this method exhibited superior bioactivity and stability compared to electrodes produced through the physical adsorption of GOD. The enzyme activity remained virtually unchanged after storage for 20 h and retained 60% activity after 120 h of storage [155].  
Figure 7: The formation of composite conducting polymer nanoparticles with embedded GOx by enzymatic polymerization and the schematic presentation of PANI (A), PPy (B), and PTH (C) polymerization mechanisms [150].  
Ruthenium-modified complexes can also serve as matrices for immobilized enzymes. [PERSON] and colleagues employed an electrochemical method to one-step immobilize di-aphorase and ruthenium-based polymers on a nanoporous gold electrode (NPG), creating an electrochemical sensor for NADH. Even after storage at 4 \({}^{\circ}\)C for 24 h, the catalytic reaction rate remained at 63% (156).  
One-step in situ enzyme immobilization in polymer electropolymerization strategies has found wide application in the fabrication of biosensors for detecting glucose, ethanol, cholesterol, and xanthine. Due to its simple and rapidly controllable preparation steps, as well as the uniform distribution of enzymes, this strategy exhibits unique advantages in the field of biosensors. However, challenges such as the limited variety of CPs and the high cost of non-conductive polymers still constrain the application of one-step in situ enzyme immobilization in polymer electropolymerization. Future research directions should focus on expanding the types of CPs or incorporating other nanomaterials to address these limitations.