The Application of Aptamer and Research Progress in Liver Disease

Abstract Aptamers, as a kind of small-molecule nucleic acid, have attracted much attention since their discovery. Compared with biological reagents such as antibodies, aptamers have the advantages of small molecular weight, low immunogenicity, low cost, and easy modification. At present, aptamers are mainly used in disease biomarker discovery, disease diagnosis, treatment, and targeted drug delivery vectors. In the process of screening and optimizing aptamers, it is found that there are still many problems need to be solved such as the design of the library, optimization of screening conditions, the truncation of screened aptamer, and the stability and toxicity of the aptamer. In recent years, the incidence of liver-related diseases is increasing year by year and the treatment measures are relatively lacking, which has attracted the people’s attention in the application of aptamers in liver diseases. This article mainly summarizes the research status of aptamers in disease diagnosis and treatment, especially focusing on the application of aptamers in liver diseases, showing the crucial significance of aptamers in the diagnosis and treatment of liver diseases, and the use of Discovery Studio software to find the binding target and sequence of aptamers, and explore their possible interaction sites. Graphical Abstract Supplementary Information The online version contains supplementary material available at 10.1007/s12033-023-01030-4.


Introduction
Nucleic acid aptamer also known as aptamer is a single-stranded DNA or RNA molecule, which is 20 to 100 nt in length.They were first isolated in the early 1990s by Tuerk and Gold using the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technique [1,2].Since its discovery, many aptamers have been screened [3,4], compared with antibodies, aptamers have the unique advantages of low molecular weight, low cost, easy chemical modification, non-toxic, low immunogenicity, easy to penetrate tissue barrier, and multi-target sites (amino acids, peptides, proteins [4][5][6][7][8][9][10][11][12][13][14], antibiotics [15], cells [16][17][18][19], viruses [20][21][22][23], bacteria [24,25], ions [26], etc.), so it has been paid more and more attention.Different diseases have different specific targets, even the same disease also has a number of different targets, such as in the progress of liver fibrosis, TLR4, inflammatory cytokines, and TGF-beta are associated with fibrosis process, and only specific monoclonal antibody against a target cannot satisfy all the targets [27], whereas aptamers could overcome this difficulty.Some diseases of liver, such as tumors and liver fibrosis, usually have no obvious clinical symptoms in the early stage, and need to rely on the gold standard of liver biopsy for diagnosis [28].However, due to its high cost and aggressiveness, few patients are willing to undergo liver tissue biopsy at an early stage.Therefore, it is necessary to find a diagnostic method with low invasiveness and high specificity.Previous experimental studies have demonstrated the multifaceted potential of aptamers in both liver disease diagnosis and targeted drug delivery [29], thereby offering a novel approach for the diagnosis and treatment of liver-related diseases [30].
However, aptamers have some limitations and uncertainties in the diagnosis and treatment of diseases.A series of partial potential biomarkers have been obtained through modern genomics, proteomics, single-cell sequencing analysis, and other technologies, but they are rarely applied in clinical diagnosis and treatment due to their low specificity.Though, screening through some biomarkers have obtained corresponding aptamers through screening, such as Sgc8 targeting PTK7 [31], Pegaptanib targeting VEGF [32], and AS1411 targeting nucleolin [33], additionally, a series of aptamers and corresponding target proteins have been identified so far.Due to the difference between protein purification and its original state, the mechanism of action of aptamers and target proteins has not been fully confirmed.At the same time, many aptamers are obtained by cell-SELEX technology screening, and the target is the whole cell.The specific molecular targets and binding methods are still unclear.However, if these limitations can be solved, the application of aptamers will make breakthrough progress.
So, the article summarizes the recent progress and current situation of aptamers in the diagnosis and treatment of diseases, especially in liver disease, to provide advice for screening and application of aptamers in the future.

Recent Progress and Status of Aptamer
Aptamers have been widely concerned in various fields because of their high affinity, strong specificity, and strong stability in binding to targets [34].Since the first aptamer was discovered, a large number of aptamers have been screened and optimized, and aptamers have promoted the development of basic research on biosensors, drug delivery systems, and disease diagnosis systems [35].At present, the application of aptamers in medicine is mainly in the diagnosis and treatment of cancers.For example, the aptamer drug supported by the US FDA on the market at present is Macugen (Pegaptanib), an RNA aptamer targeting vascular endothelial growth factor (VEGF), which is applied to the treatment of eczema-related macular degeneration [36].In SELEX screening, the performance of aptamers such as those targeting proteins may not be better than those obtained by targeting cells because the target molecules in cell-SELEX are closer to the original state of the in vivo environment [37].
Due to the simplicity of aptamer screening procedures and principles, a significant number of aptamers have been screened and patented.However, there is a limited availability of aptamers for biosensors, diagnostic probes, and therapeutic reagents, possibly due to challenges in postscreening modification and optimization [38].By conducting searches on patent websites, one can gain insights into the quantity and development trends of aptamers in recent years.The results are depicted in Fig. 1, which indicates a gradual increase in the annual number of patent applications for liver disease-specific aptamers, highlighting their promising application prospects.Figure S1 of supply materials also presents an overview of the total number of aptamer patents since 2014.

The Aptamers are Currently in Clinical Trials
The aptamer can be optimized by truncating their sequences to reduce molecular weight and improve binding affinity, and can also be combined with high molecular weight fragments such as polyethylene glycol [39], cholesterol [40], protein [41], or nanomaterials [42] to prolong renal excretion.After sequence truncation and conjugation, modification at nucleotide ribose 2 position with -O-Me, -NH 2 , -F, etc., can prevent nuclease degradation [43].Aptamer research is not going well in ongoing clinical trials, for example, E10030 inhibits fibroblast proliferation by blocking platelet-derived growth factor B chain (PDGF-B), and was declared a failure in phase III in august 2017, because E10030 combined with Ranibizumab did not prove to be more effective than Ranibizumab alone.Another example is the use of aptamer REG1 for anticoagulation therapy which was terminated in the trial due to severe allergic reactions [33].Despite these difficulties, a number of aptamers are currently in clinical trials for the treatment of ocular diseases, thrombotic and vascular diseases, and cancers [44].In terms of drug delivery, aptamers can replace other transporters for targeted delivery of drugs.For example, an aptamer specific for transferrin receptor CD71 (TfR) can replace transferrin and play an alternative role in cellular imaging or targeted drug delivery [45].It can be used as a diagnostic reagent for biosensors by hybridization with DNA, RNA, peptides, or nanomaterials for specific targeting and imaging [46].Clinical trials of aptamers can be found on https:// clini caltr ials.gov/, a total of 44 aptamers and drug test the aptamerrelated projects, the apatamers which have entered clinical trials included 12. Table 1 summarizes all aptamers that have entered clinical trials, including the diseases they have treated, the targets of action, and the clinical stages of investigation.

Discussion on the Use of Aptamers as Therapeutic Drugs
When applied to biological agents, aptamers are often used as therapeutic agents to regulate biological pathways and intervene in a variety of diseases [60].The treatment of neovascular-related macular degeneration by intravitreal injection of aptamer E10030 in combination with Ranibizumab has proven successful in safety and efficacy despite failure in phase III clinical trials [47,48].The aptamer Pegaptanib, as an anti-VEGF antagonist, has been approved by the US FDA for intravitreal injection to block VEGF and thus treat AMD [61,62], the first successful treatment for wet AMD.Although its use and results are not perfect, its benefits in treating AMD far outweighs its risks [63].EYE001, a VEGF-targeting aptamers, has been shown in preclinical and clinical studies to improve vascular permeability and ocular neovascularization, with no significant side effects in a single-dose intravitreal injection in phase Ia clinical trials [64].ARC1905, an aptamer that inhibits complement factor C5 to prevent terminal fragment structure by screening, is mainly used in the treatment of age-related macular degeneration, and a phase I study is currently under way to evaluate its safety and efficacy in combination with Lucentis [65,66].
NOX-H94 is a structural mirror aptamer, which specifically binds hepcidin (Hep) and regulates chronic inflammatory anemia by blocking the biological function of Hep.As a non-natural mirror aptamer, it is not recognized by nuclease and immune system, and has certain safety [67].NOX-E36 has a length of 40 nucleotides and can specifically bind to the proinflammatory chemokine C-C motif ligand 2 (CCL2).NOX-E36 is mainly used in the treatment of type 2 diabetes and has performed well in phase I clinical trials.It has an inhibitory effect on CCL2 without activating the innate immune system, which can be used as a new targeted therapy for diabetic kidney injury [51].NOX-A12 is a novel pegylated oligonucleotide that specifically binds to the chemokine SDF-1 and is mainly used in the treatment of chronic lymphocytic leukemia.At present, its phase II clinical results show good safety Fig. 1 The number of patent aptamers for liver diseases since 2014.keywords included: "aptamers," "liver disease" and efficacy, and it can be used in combination with other targeted drugs to enhance efficacy and reduce drug side effects [68].BAX499, formerly known as ARC19499, is an anti-tissue factor pathway inhibitor (TFPI) inhibitor.It mainly combines with TFPI to inhibit TFPI-mediated tissue factor pathway and shorten whole blood coagulation time.Furthermore, the bleeding of hemophilia patients is inhibited, so as to achieve the purpose of treatment [69].AS1411 is an aptamer composed of 26 G-rich nucleotides, which can form a G-quadruplex structure.It is mainly used in cancer-targeted drug delivery, and has also been developed as a targeted drug or probe with high safety.At present, it is mainly connected with nanoparticles for targeted therapy or imaging of cancer [70].As an anticoagulant, aptamer REG1 performs well against platelet thromboembolism, especially in cardiovascular disease.However, as an anticoagulant, its pharmacodynamics and immunogenicity are unpredictable, and it was eventually discontinued in clinical trials due to severe allergic reactions.Aptamer ARC1779 primarily inhibits von Willebrand factor (VWF), which causes thrombocytopenia in thrombosis.The current experimental results show that ARC1779 is well tolerated and safe, and has a good recovery effect on organ failure caused by thrombocytopenic purpura [71].In the future, aptamers and their derived sensors and probes will provide multiple options for the diagnosis and treatment of diseases [44].
Cost-effectiveness analysis should also be considered in the application of aptamers.Using Pegaptanib as an exemplar, the FDA approved aptamer drug for AMD.AMD refers to age-related structural changes in the macular area of the eye, predominantly affecting individuals over 50 years old and representing a significant cause of blindness among older adults.Pegaptanib is a 28-base RNA aptamer employed as a vascular endothelial growth factor antagonist in AMD treatment.Current therapeutic options for AMD encompass ranibizumab, Pegaptanib, bevacizumab, and PDT with verteporfin.Studies have demonstrated that ranibizumab is considered the most cost-effective among approved regimens for treating AMD [72].However, UK-based analysis revealed that Pegaptanib exhibited similar cost-effectiveness compared to best supportive care over a decade-long timeframe [73].Nevertheless, it should be noted that the cost-effectiveness of Pegaptanib varied considerably depending on disease stage and time horizon [72,74,75].

Discussion on the Use of Aptamers as Drug Delivery Systems
Aptamer can be used not only as a drug directly but also as a drug carrier to deliver drugs directly to cells by coupling drugs such as siRNA, decoy ODN, and micro-RNA [76].
Existing RNA, DNA aptamers, and siRNAs are covalently or non-covalently combined to form chimeras, and modified, such as polyethylene glycol (PEG), to prolong degradation time and improve their bioavailability in vivo [77], while its side effects are significantly lower than those of chemotherapy and radiotherapy drugs [60,65].The aptamer Sgc8, which is currently in clinical trials, can target PTK7 as a potential drug for the treatment of malignant hematological diseases, solid tumors, and other diseases [78].However, the development of aptamers has been questioned due to many setbacks in clinical trials [79].One of the important issues is the synthesis and modification of aptamers.The synthesis of long sequence aptamers, especially RNA, is very difficult, and some special modifications can also increase the cost, limiting the clinical application of aptamers [76].With the development of computer technology, molecular simulation technology can realize the prediction of chemical synthesis, modification, and structure.It is believed that the application of aptamers will make greater progress in the near future.

Liver Disease-Related Biomarkers
Liver is the main metabolic organ of human body.Liver diseases are usually triggered by the death of hepatocytes and progresses to hepatitis, fibrosis, cirrhosis, and liver cancer.At present, liver diseases mainly include acute liver diseases caused by food poisoning and infection, and chronic liver diseases caused by viral infection, fatty liver, alcoholic hepatitis, etc. [80].In different liver injuries, there may appear many different biomarkers.Some of these specific markers play an important role in the diagnosis and targeted therapy of liver disease.ALT and AST are the most common biomarkers with significantly increased expression after liver injury, but lack specificity [81].Other common biomarkers, such as K18, HMGB1, and micro-RNAs, also sensitively reflect liver injury.Moreover, combined with complementary markers, it can be used as a commonly used diagnostic index to effectively diagnose liver diseases caused by various factors [80].Table S1 (shown in supply materials) summarizes the current biomarkers in the liver diseases process and Table 2 concludes the aptamers of known biomarkers obtained by screening which is used in liver diseases.But at present, maybe there are many studies on specific markers of liver cancer, so the current research on the applications of aptamers in the diagnosis and treatment of liver diseases is mainly aimed at liver cancers, such as develop a label-free microcantilever array aptasensor to detect HepG2 cells and to provide a simple method for the detection of liver cancer cells [82], use an aptamer-nanotrain to deliver doxorubicin selectively to liver cancer cells [83].As for other kinds of liver diseases, TNF-α-targeting aptamer can attenuate the degree of hepatocyte damage and potentiate early regeneration of the liver tissues in TNF-α-mediated acute liver failure [30], and aptamer-functionalized ultrasound nanobubbles with resveratrol and ultra-small copper-based nanoparticles can treat non-alcoholic fatty liver diseases [84].

Aptamers are Used in the Diagnosis and Therapy of Liver Cancer
Cancer may not show symptoms in its early stages, which prevents timely diagnosis and treatment of cancer at an early stage.If in the early stages of cancer, biomarkers have emerged, then it is of great significance to screen aptamers targeting biomarkers as early tumor-specific diagnostic and therapeutic reagents.As probes, aptamers have better specificity and sensitivity than AFP, CEA, and other biomarkers for diagnosis [116].Liver cancer is one of the five most common cancers in the world, among which HCC is the most common [117].The traditional treatment strategy for HCC is surgery, but the recurrence rate is as high as 70%.Liver cancer stem cells (LCSC) have been found to have a great relationship with the growth, transformation, and metastasis of liver cancer [118].Therefore, the main treatment direction is to find specific markers of LCSC as therapeutic targets for targeted drugs.Table 2 presents a comprehensive compilation of 22 aptamers, which have been identified as valuable diagnostic, therapeutic, and targeted delivery tools for liver cancer.Among them, the aptamer CL-4RNV616 specifically targets the epidermal growth factor receptor (EGFR), which is highly expressed in many cancers and is considered a prognostic indicator of cancer [119].The specific recognition of EGFR protein in tumor cells can be used as a targeted probe for early cancer detection, but the binding ability of MDA-MB-231 breast cancer cells, hum-7 liver cancer cells, and U87MG glioma cells suggests non-specific cell recognition [107].

Aptamers are Used in Early Diagnosis of Liver Fibrosis
Liver fibrosis is an intermediate process of liver injury and inflammation caused by hepatitis virus infection, alcohol abuse, immune response, drug and chemical damage, and then develops into chronic progressive liver disease.During liver injury, inflammation, and repair, hepatic stellate cells (HSCs) located in the perisinusoidal space are activated Inhibits tumor angiogenesis and inhibits melanoma growth and liver metastasis Therapy [115] and transformed into myofibroblasts (MFCS).MFCS produce large amounts of collagen, mainly extracellular matrix (ECM), resulting in liver fibrosis [120,121].Various cytokines and related signaling pathways in the development of liver fibrosis, as well as the pathways of stellate cell clearance (apoptosis, senescence, recovery to inactivation), have been clearly elucidated.Liver fibrosis eventually develops into cirrhosis and liver cancer.Liver fibrosis has been shown to be reversible, so treatment of liver fibrosis can effectively prevent cirrhosis and liver cancer [122].At present, RNA interference (RNAi) has been studied for the treatment of liver fibrosis, but its targeting and effectiveness into the body are poor, so it is necessary to find different vectors for siRNA delivery [123].At present, the diagnosis of liver fibrosis mainly depends on pathology and imaging examination.Although molecular markers of liver fibrosis are abundant [124], there are very few aptamers related to liver fibrosis.This is mainly because the progress of liver fibrosis is affected by many factors comprehensive, so it is used for the screening of aptamers of liver fibrosis and the application may be limited by a lot of restrictions, in Table 2, we only found two relevant aptamers, which is primarily on liver fibrosis in the process of increased protein expression on HSCs, and the treatment of siRNA has yet to achieve good results.The aptamer 20 obtained by insulin-like growth factor II receptor (IGFIIR) targeting performed well at the cellular level after carrying PCBP2 siRNA.Although IGFIIR is a non-specific marker of HSCs, it is overexpressed in activated HSCs and therefore was selected as the target.Aptamer-20 carrying siRNA into HSC-T6 can trigger the silencing effect and restore the activated HSC-T6 to the quiescent state [111].For the screening of HSCs aptamer, in addition to HSC-T6, human LX-2 cell line or primary stellate cells isolated directly from mice can also be selected as positive screening cells, and better results will be obtained.

Aptamers are Used in Diagnosis and Therapeutic of Liver Injury
Liver injury mainly includes trauma, acute injury caused by drugs, and chronic injury caused by viral infection.The main treatment for liver injury is liver transplantation, or the prevention and treatment of complications such as liver failure, without other specific treatment [125].In the case of acute injury, hepatocyte necrosis leads to the secretion of TNF and the elevation of acute CRP.During liver failure, aptamer targets TNF and CRP mainly by inhibiting TNF and tracking the site of CRP secretion, thereby blocking the inflammatory process and reducing and eliminating inflammation [109,126].However, neither of these two targets is specific and can be increased by stress in other inflammatory states.Acute liver failure is rare, so it may still be misdiagnosed in diagnosis and treatment.Chronic liver injury is mainly caused by hepatitis B virus (HBV), hepatitis C virus (HCV), influenza, and other viruses [127].SARS-CoV-2 can also affect the liver, but the main reason may be druginduced liver injury caused by the use of antiviral drugs such as lopinavir/ritonavir, rather than the virus itself, and the exact mechanism has not been proved [128].At present, for HBV and other infections, long-term nucleotide surimi, which is well tolerated and has few side effects is used, and the main preventive measure is vaccination without infection [129].New treatments are still being developed, and aptamers are good candidates to carry antiviral drugs that can effectively treat HBV.

Aptamers for Other Liver-Related Diseases
Many diseases can cause indirect damage to the liver in other ways.For example, cancer cells can migrate to the liver through the blood circulation and cause liver damage.Liver metastasis of cancer cells is more common than primary liver tumors, and liver metabolism is very vigorous.In the early stage of the disease, there are often no symptoms, and it is easy to miss the best treatment time [130].At present, the main aim is to prevent the disease and reduce the involvement of the liver.Metron factor-1 (MF-1) has great potential to prevent some malignant diseases that are difficult to treat, including liver metastases, melanoma, gastrointestinal tumors, etc., because it inhibits angiogenesis and tumor metastasis [131].Cells in the liver, including sinusoidal endothelial cells, HSCs, and kupff cells, communicate with cancer cells through complex cytokines that are potential therapeutic targets [132].Schistosomiasis is a global health disease, and Schistosome infection can lead to complications such as liver fibrosis and portal hypertension [133].At present, the aptamer LC15 obtained from Schistosoma japonicum egg screening can be used as a specific tool for accurate diagnosis and targeted therapy.It can carry specific drugs to kill Schistosoma japonicum eggs and effectively improve the serious health problems caused by Schistosoma parasite infection [134].

Simulation of Aptamers and Targets
Aptamers enter cells by binding to protein targets on the cell surface and being internalized.Many targets have been identified, but how the target and aptamer interact is still not very clear, because the protein is difficult to isolate and purify, and even if isolated, it is difficult to maintain its original state [135].Therefore, at present, the interaction of aptamers with their targets can only be inferred by calculating molecular simulation docking.This is generally done by constructing the secondary and tertiary structure of the aptamer, performing homology modeling of the corresponding target protein, and performing simulation docking on the Discovery Studio software to find possible modes of action according to the ranking of ZRANK scores [136].Due to the secondary and tertiary structures of the aptamer fold, protein homology modeling differs from theory and is entirely computer simulated.Its authenticity has yet to be confirmed, but it can be used as a theoretical reference.

Secondary and Tertiary Structure Construction of Aptamer
Mfold web server (http:// unafo ld.rna.albany.edu/?q= mfold) was used to predict and analyze the linear ssDNA aptamer secondary structure [137].The optimal operating parameters are as follows: the folding temperature was controlled at 37℃, the ion conditions were Na + 1.0 mM, Mg 2+ 0.0 mM, the second-best percentage was 50%, the window parameters were default, and the maximum distance between paired bases was unrestricted by default.The aptamer structure with the smallest free energy, the smallest G value, was obtained.Select secondary structure Vienna format as a template to build the tertiary structure, in RNAcomposer (http:// rnaco mposer.ibch.poznan.pl/) generated in the tertiary structure, download to generate the tertiary structure of PDB format [138].The nucleic acid sequence of the RNA tertiary structure was mutated using the biological software Discovery Studio to convert RNA into DNA sequence, and the structure was optimized [136,137].

Target Protein Homology Modeling
In order to obtain information of each species-related genes in NCBI (https:// www.ncbi.nlm.nih.gov/ gene/) and to find the corresponding protein gene, the aptamer corresponding target protein was found.We chose homo sapiens (human) to find the amino acid sequence of the desired protein by the relationship between the corresponding gene and the protein.Amino acid sequence imports SWISS-MODEL (https:// swiss model.expasy.org/ inter active) to carry on the homologous modeling, which can be directly chosen to establish a MODEL to get the corresponding protein template.To find out the optimal template search sequence, the most extensive coverage (generally more than 30%) and high matching degree should be used as a template.In Table 3, the GMQE, QMEAN, Seq identity, MolProbity Score, Ramachandran, Ramachandran Outliers, and solvation series parameters of the corresponding template are given, which are searched in the template to remove GP73 low credibility.Other validations were performed with high confidence, and the best homology template in PDB format was downloaded as the docking receptor.

Molecular Simulation Docking Between Ligand Receptors
Docking of nucleic acid aptamers and proteins was performed in Discovery Studio.The water molecules on the surface of the protein were first removed and re-hydrogenated and structurally optimized in chemistry as acceptors.Before docking with Dock Proteins (ZDOCK), you need to choose enough parameters, including selecting "Angular Step size" to be more extensive and detailed 6 instead of 15, selecting "Zrank" to be true, and selecting "Angular step size" to be more extensive and detailed 6 instead of 15.Select "Parallel Processing" to false, and ZDOCK runs.After completion of docking, the best docking result was selected according to the ZRANK scoring order [136].By changing different docking methods, ZRANK scores of corresponding      structural maps were obtained, and the interaction modes of aptamers and proteins were analyzed.Whether the motif of the aptamer binds to the target protein in a similar way to that of the contrast antibody is not known, nor is it clear that it is consistent with the results of computer simulations.In general, lower ZRANK scores indicate stronger receptor-ligand interactions [139].The parameters and images corresponding to the docking results are shown in Table 4 and Fig. 2, respectively.

Discussion
Aptamers bind cells in an antibody-like manner, recognize cell-specific targets, enter the cell by endocytosis to form vesicles, and after entering the cell, some of the aptamers escape from the vesicles.Some aptamers function in the cytoplasm, while others enter the nucleus [140].Since their discovery, aptamers have attracted much attention due to their non-toxicity, low immunogenicity, easy penetration of tissue barriers, and the advantages of multiple targets (amino acids, peptides, proteins [4,10,14], antibiotics [15], cells, viruses [20,23], bacteria [24,26]).At present, the defects of aptamer and SELEX technology hinder the utilization degree  of aptamer.Improving the screening process and optimizing aptamer may make new breakthroughs in aptamer research [141].Despite many setbacks in research, it has been used as a potential alternative to antibodies and diagnostic reagents in biomedical applications such as disease diagnosis, molecular imaging, drug delivery, biomarker discovery, and drug screening [142].By summarizing the aptamers that have been patented so far, we get a general idea of the current state of research.Although many aptamers have been discovered, they are mostly used in other industries.In medicine, it is still in the stage of basic research, and there is still a gap between it and clinical diagnosis and treatment.In the process of screening aptamers, the biological characteristics such as specificity, affinity, stability, truncation and modification, carrying decoy ODN, micro-RNA or siRNA, etc., still need to be determined, which increases the cost of research and leads to the bottleneck of research.At present, the emergence of a variety of bioanalysis software provides convenience and support for related research.In addition to comparing with the existing experimental results, it can also provide certain guidance for the experiment.

Conclusion
The high affinity, targeting specificity, and cell internalization ability exhibited by aptamers are key to their application in drug delivery and the treatment of liver diseases.They can search for different target proteins and be applied to the diagnosis and treatment of liver diseases through screening corresponding aptamers.