Preparation Of AS1411 Aptamer Targeted Anti-tumor Chinese Medicine Complex And Conformation Study Of G Base Rich Aptamer

Due to the targeting and anti-tumor properties of AS1411 aptamer,various AS1411complex systems have been developed in recent years.According to the development status in recent years,AS1411-anti tumor Chinese herbal extract complex system has broad development potential and application prospect.In this paper,we mainly study the preparation of AS1411-anti tumor Chinese herbal extract complex system and analyze the binding mechanism by multispectral method,as well as the effect of the addition order of multiple monovalent ions on the conformation of G-base-rich aptamers（such as AS1411,etc.）.The main content and innovation of this work include the following parts.（1）In this work,CPT-AS1411 complex system was prepared,and the non-embedding binding mechanism of anticancer drug Camptothecin（CPT）and AS1411was explored by multispectral method.Fluorescence and ultraviolet spectra were used to detect the structural changes of AS1411 with different concentrations,which may be caused byπ-π*transition/n-π*transition,or the presence of polar solvents.The variation trend of binding strength between CPT and AS1411 was revealed,and the quenching was inferred to be static.The ion selectivity parameters show that there is little relationship between the complex system of CPT-AS1411 and electrostatic interaction.In addition,Et Br substitution studies and CD spectra also confirm the non-embedding binding mode of CPT and AS1411.According to the stability analysis,CPT-AS1411 composite system is easier to be stored at-4℃.（2）In this work,anti-tumor drug PTX was coated with polyethylene glycol grafted manganese oxide（PEG-Mn O）to prepare novel nano-sized particles.After further modification with AS1411 aptamer,the binding interaction between PTX and AS1411 was verified by multispectral method,and the formation of Mn O-PTX-AS1411 complex was confirmed.Mn O-PTX complex system should be reacted and preserved at-4℃.The prepared Mn O-PTX complex and Mn O-PTX-AS1411 complex were compared and analyzed by multispectral method.It can be clearly seen that after the introduction of AS1411 sequence,The prepared Mn O-PTX-AS1411 complex is a nano-sized particle.Compared with Mn O-PTX,Mn O-PTX-AS1411 shows obvious quenching effect,and there are main peaks（positive peaks at 233nm and 255nm and negative peaks at 242nm）in the CD diagram,which is speculated to be a parallel quadrupole structure.The resulting spectral changes confirm the generation of Mn O-PTX-AS1411 complex system.The absorption peak of stretching vibration of C-O-C between ethers originally existed in Mn O-PTX complex system was not only detected by infrared spectroscopy and XPS spectroscopy,but also the Mn 2p_1/2 state of manganese element was observed to disappear,which further confirmed the existence of Mn O-PTX-AS1411 complex system.（3）In this work,based on the conformational changes of different sequences and univalent ions K⁺,Na⁺,NH₄⁺,High+Low,Low+High and triploid ions with different addition sequences,the optimal stable ion combination order of quaternary structure of 12different DNA sequences was obtained.From the perspective of fluorescence spectra,except sequences HT-V15 and PW17,AS1411 and HT-V18,the stability of G-quadrupole structure basically follows a certain rule（hybrid structure>Parallel quadrupole Structure>Antiparallel quadrupole Structure>Parallel/antiparallel mixed quadrupole structure）,in which the addition of three heavy ions will make the stability of the G-quadrupole structure of AS1411 aptamer in the strongest state,and the hybrid structure usually appears in the AS1411 sequence with low G base content.Furthermore,the optimal logic scheme of 12kinds of DNA ions was obtained by circular dichroism analysis.The conclusion was that the antiparallel quadrupole structure occupied the largest proportion in the quadrupole structure.As for AS1411 aptamers,although the G-quadrupole structure has different stability under different conditions,the anti-parallel quadrupole structure is still dominant,which further confirms the repeatability of the anti-parallel quadrupole structure in this experiment.It is worth mentioning that the innovation point of this work is to screen out that the best addition scheme of sequences AS1411 and HT-V18 is triploid ion K⁺+NH₄⁺+Na⁺and K⁺+Na⁺+NH₄⁺.