Circular Bivalent Aptamers And AS1411 Polymeride Construction And Bioproperties Investigations

Aptamers play essential roles in many biomedical research fields such as biological analysis and targeted drug delivery.Tailoring of ingenious chemical moieties toward aptamers can enhance their biomedical properties and/or confer them with exogenic biological functions that,in turn,can considerably expand their biomedical applications,or even improve their clinical translations.The development and utilization of circular bivalent aptamers(CBApts)have improved the inherent limitations of aptamers,such as easy enzymatic degradation and limited recognition range.Therefore,CBApts has been widely used in drug delivery,tumor diagnosis and treatment and other fields.However,the current construction technology of CBApts faces several challenges,including the need of modifying additional nucleosides at the end of the aptemers and their limited applicability,which ultimately hinder their wider application.Therefore,the development of new methods to construct CBApts may provide new molecular probes and technical support for the accurate diagnosis and treatment of major diseases.In this paper,we constructed a variety of CBApts and multivalent aptamers by using strain-promoted azide-alkyne cycloaddition(SPAAC)reaction,and investigated their properties and biomedical applications.Specific research contents include:(1)Studies on CBApts construction by SPAAC reaction.Through the screening and optimization of reaction conditions such as reaction temperature,reaction time,reaction solvent,concentration and molar ratio of reactants,the best reaction conditions of SPAAC reaction applied to the construction of CBApts were determined.At the same time,the universality of this method was explored,and it was proved that this method could be applied to different aptamers and ss DNA with different lengths,thus providing a new method for the construction of circular bivalent aptamers.(2)Studies on biological properties and application of CBApts.Considering that specific recognition and biological stability are important characteristics for aptamers.We tested the binding ability,endocytosis ability and stability of CBApts,and they exhibited better binding ability and stability compared with monovalent aptamers.Based on these results,the application potential of CBApts in vivo was further explored,and revealed their better tumor recognition,as well as accumulation and retention ability in tumor tissues.In addition,we designed a CBApts-mediated “recognition-then-interaction” strategy for regulating and enhancing intercellular interaction,which provides new technique support for aptamers to regulate cell behaviors.(3)Studies on the construction of AS1411 polymeride by SPAAC reaction.AS1411polymeride(polymer AA)was constructed based on the advantages of SPAAC reaction and the specific recognition ability of AS1411 aptamer to a variety of tumors,and its broad-spectrum binding ability and significantly improved stability and sustained recognition of target cells were verified.Subsequent in vivo imaging also showed better tumor targeting.Based on the role of AS1411 aptamer in clinical treatment,the cytotoxicity of polymer AA and AS1411 aptamer was compared,providing important guidance for the development of subsequent application research.