Green Design and Response Surface Optimization of Cationic Fiber-Based Enzyme Activity Test Paper

The development of sustainable and high-performance paper-based biosensing materials remains challenging, mainly due to insufficient surface charge density and weak wet strength. In this study, a green strategy that combines PFI pretreatment with cationization using 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) was proposed. The cationization process was optimized using response surface methodology to produce cationic cellulose fibers with high charge density. The optimized fiber exhibits a zeta potential of +45.6 mV and a degree of substitution of 0.1421, enabling the preparation of an enzyme activity test paper (EATPS) with excellent wet strength and charge stability. To demonstrate feasibility, the EATPS was applied to DNA polymerase activity assays, showing a strong linear correlation between ΔCPM and DNA polymerase activity ( R 2 = 0.983), demonstrating its excellent sensitivity and stability. This work not only holds great potential for the development of high-quality, all-cellulose-based enzyme activity test papers but also offers a new approach for constructing green and biodegradable detection platforms.