Selective Separation Of Typical Adenosine Molecules By Interface Induced Surface Imprinted Adsorbents

Adenosine is a specific endogenous purine nucleoside derivative that is widely found in natural biological systems.Adenosine is involved in biological genetic information transfer,affects protein synthesis and polysaccharide metabolism,and has a very important regulatory role in the growth,proliferation,differentiation and other physiological behaviors of cells in living organisms.Adenosine can be used as an important monitoring indicator of organisms,serving for monitoring the growth status of agricultural crops,breeding optimization of livestock and human disease detection.Adenosine dips and root sprays on agricultural crops can significantly increase crop yields.In addition,adenosine,as an important branch of nucleoside,is recognized as an important intermediate and raw material for the synthesis of novel agricultural pesticides,herbicides,agricultural antibiotics and novel antiviral drugs.However,the low purity and many structural analogues of adenosine synthesis products make the precise adsorption separation of adenosine,detection of trace adenosine and adenosine recovery difficult.Therefore,exploring new methods for the precise isolation and purification of adenosine is of great scientific,economic and social importance for fields such as agricultural engineering and disease control.Molecularly imprinted polymers（MIPs）are synthetic substances resembling natural antibody-antigen systems that bind selectively to targets through a"lock-and-key"mechanism and can be used as a precise identification tool for adenosine molecules.The surface molecularly imprinted polymers（SMIPs）,built based on surface imprinting methods of nanomaterials,have a very high specific surface area and short diffusion paths,which can significantly improve the adsorption capacity and mass transfer efficiency of adsorbents.In this work,Pickering emulsion,paramagnetic iron tetroxide nanoparticles（Fe₃O₄ NPs）and polydopamine nanotubes（PDA NTs）were used as nanocarrier materials;specific pyrimidine base functional monomers 1-（vinylbenzyl）thymidine（VBT）and 5-（2-methoxyvinyl）-2′-deoxyuridine（Acr U）were designed and synthesized;then interfacial The nanoimprinted adsorbents for adenosine 5′-monophosphate（AMP）and 2′-deoxyadenosine（d A）were fabricated by grafting MIPs onto nanocarrier materials.Furthermore,the secondary functionalization of nanoimprinted adsorbents was also preliminarily attempted with antifouling and antibacterial properties.The properties of nanoimprinted adsorbents such as morphology,structure and chemical composition were analyzed by various physicochemical characterizations;the selective adsorption separation performance of nanoimprinted adsorbents on AMP or d A was evaluated by static adsorption experiments to elucidate the recognition mechanism.The main studies are as follows:（1）Interface-induced domain-limited polymerization of imprinted adsorbents by Pickering emulsion for the selective separation of adenosine 5′-monophosphate.Firstly,GMA nanoparticles were synthesized by soap-free emulsion polymerization and carboxyl functional groups were modified on the surface of GMA NPs to chelate trivalent iron Fe（III）ions,and the nanoparticles were used as Pickering particles for oil-in-water（O/W）Pickering emulsions.Secondly,the water-soluble target molecule AMP was assembled with the oil-soluble functional monomer VBT at the oil-water interface,and the VBT was photoinitiated polymerized on the surface of Pickering particles to form a MIPs layer.Finally,the adsorption equilibrium,kinetics,selectivity and regeneration performance of the adsorbents were evaluated by static adsorption experiments.The results showed that the adsorption of GMA-IDA-Fe³⁺@MIPs on AMP followed a quasi-secondary kinetic equation,indicating that the adsorption process was dominated by chemisorption;the Langmuir equation better described the adsorption equilibrium process,and the equilibrium adsorption capacity at 25℃was 98.24μmol/g;the selectivity experiments showed an imprinting factor IF=1.74;After four cycles of adsorption-desorption tests,85.19%of the initial adsorption capacity value was maintained;the adsorption experiments on actual samples showed that GMA-IDA-Fe³⁺@MIPs had a significant specific adsorption capacity for AMP in human urine.（2）Surface-induced layer-by-layer assembly of magnetic adsorbents for selective separation of adenosine 5′-monophosphate.Firstly,paramagnetic ferric tetroxide nanoparticles（Fe₃O₄ NPs）were prepared by a hydrothermal method,MIPs were then grafted onto the surface of Fe₃O₄ NPs by thermal initiation and precipitation polymerization using Acr U and Acrylamide（AM）as functional monomers and AMP as template molecules.Secondly,the layer-by-layer assembly of MIPs was mediated through the Schiff base reaction through aldehydes on glutaraldehyde（GA）and amino groups on AM.Finally,the adsorption effect of different imprinted layers was examined with static adsorption experiments.The experimental results showed that the Fe₃O₄NPs@MIPs-LBL2 covered with two MIP layers showed the best imprinting effect（IF=2.50）,and the adsorption of AMP by Fe₃O₄ NPs@MIPs-LBL2 was consistent with quasi-secondary kinetics and Langmuir model with a saturation adsorption capacity of 105.72μmol/g;a significant AMP selective recognition ability was still preserved in the human urine environment.In addition,Fe₃O₄ NPs@MIPs-LBL2 can be recovered with rapid magnetic response under an external magnetic field,further improving the problem of difficult recovery of nanoimprinted adsorbent and great difficulty of recovery loss.（3）Construction of Anti-Biofouling Imprinted Sorbents Based on Anisotropic Polydopamine Nanotubes for Fast and Selective Capture of 2′-Deoxyadenosine.The development of multifunctional sorbents with specific recognition,rapid separation and biofouling resistance is highly desired for nutrient-rich biological samples.Herein,anti-biofouling imprinted sorbents based on anisotropic polydopamine nanotubes（J-Ag@PDA NTs-MIPs）were synthesized for selective separation and enrichment of 2′-deoxyadenosine（d A）.Molecularly imprinted polymers（MIPs）as recognition units were grafted onto the exposed outer surface of as-prepared polydopamine nanotubes（PDA NTs）,and then Ag nanoparticles（around 40 nm）as antifouling units were independently loaded in their lumen by in situ growth.By batch mode experiments,J-Ag@PDA NTs-MIPs exhibited a fast adsorption equilibrium time（5.0 min）and an ultra-high adsorption capacity（223.30μmol/g）for d A.A high imprinting factor of about 4.80 was observed for d A when compared with the other structural analogues,resulting from the shape,group and size matching of imprinted sites to the template molecules.By evaluating the d A enrichment from spiked human serum solutions,the potential for capturing targeted d A in complex biological samples was confirmed.In addition,the loading of Ag NPs significantly enhanced the antibacterial performance of the imprinted sorbents,which was important for improving anti-biofouling properties under a complex eutrophic water environment.This work provided an approach for constructing plastic antibodies with enhanced adsorption and anti-biofouling performance.