###### Abstract  
Anion exchange affinity-based controllable surface imprinting is an effective approach to overcome low imprinting efficiency and high non-specific binding capacity. The template proteins were first immobilized on the anchored tetraalkylammonium groups of the nanoparticles via anion exchange affinity-based interactions, enabling monolayer sorption using a low template concentration. The combined use of surface-initiated photoiniferter-mediated polymerization to precisely control the imprinted film thickness, allowing the formation of homogeneous binding cavities, and the construction of effective binding sites resulted in a low non-specific binding capacity and high imprinting efficiency. The obtained imprinted films benefited from the anion exchange mechanism, exhibiting a higher imprinting factor and faster binding rate than the reference material. Binding tests revealed that the binding strength and selective recognition properties could be tuned to a certain extent by adjusting the NaCl concentration. Additionally, in contrast to the harsh template elution conditions of the covalent immobilization approach, over 80% of the template molecules were readily removed from the imprinted films using supersonic elution with an aqueous mixture of NaCl and HAc. Introducing template immobilization by anion exchange interactions to the synthesis of imprinted materials may provide a new approach for effective biomacromolecular imprinting. ao 20221420111 11 April 202212 May 2  
proteins. A variety of strategies have been developed to overcome the mass transfer limitation, such as epitope imprinting [13] with a fragment of the original protein molecule as a template, the use of moderately cross-linked hydrogels [14], and surface imprinting [15]. Thus, imprinting materials with sites situated at or close to the surface of the polymeric matrix, enabling easy access to target protein molecules, is considered the most promising approach for protein templates [16]. Nevertheless, random rotation of the template proteins spontaneously occurs during the imprinting process, resulting in the formation of various complex imprinting cavities at random positions in the polymers. Consequently, the obtained imprinted materials exhibit a lower binding affinity and selectivity toward the template proteins [17]. The immobilization of proteins has recently been widely studied, motivated by the prospect of using polymeric or inorganic particles as new types of substrate materials [18; 19]. In this strategy, proteins are immobilized on surfaces using both covalent and non-covalent approaches. Coval immobilization has been achieved by forming covalent bonds between the template proteins and substrate particles [20; 21; 22]. [PERSON] et al. [21] pioneered a strategy based on covalent template protein immobilization using aldehyde-group-modified silica particles as substrates. This protocol was further developed by [PERSON] et al. [22] to fabricate silica-based imprinted particles using APBA instead of modified silica particles. However, this approach has a considerable drawback with respect to the harsh conditions required for removing the template, which could affect the stability unless the template is stripped after sacrificing the substrate. The noncovalent immobilization method mainly relies on reversible physical adsorption and ionic linkages via stable ionic bonds [23]. The physical adsorption method was developed by [PERSON] et al. [24] to immobilize template proteins on the surfaces of carboxylic acid-modified silica nanoparticles. An ultrathin imprinted film was then synthesized through surface polymerization at a low monomer concentration. The resulting imprinted particles demonstrated a high imprinting factor and specific rebinding capacity for the template. However, template leakage from the substrate may occur when the interactions are relatively weak in the imprinting process, leading to the decimation of the template and low imprinting efficiencies.