CD20 is a surface marker protein of B-cell lymphoma, and its extracellular region is the target of specific antibodies and drugs. To obtain a cheap and easily modified specific preparation targeting CD20, we optimized the gene of CD20 extracellular region according to codon degeneracy to facilitate its expression in Escherichia coli. The optimized gene was cloned into pGEX-4T-1 vector, and the recombinant vector was transformed into E. coli BL21(DE3) for expression. The purified protein was identified by SDS-PAGE and Western blotting. Systematic evolution of ligands by exponential enrichment (SELEX) was employed to screen the ssDNA aptamer that specifically binds to the fusion protein, and the affinity of the aptamer to CD20 was detected by flow cytometry. Then, the cytotoxicity test was carried out to examine the inhibitory effect of the aptamer on B lymphoma cells. In this study, we established the prokaryotic expression method of CD20 and obtained the aptamer specifically binding to the extracellular region of CD20, which laid a foundation for the development of therapeutic drugs targeting CD20.
Humans ; Escherichia coli/metabolism* ; SELEX Aptamer Technique/methods* ; Aptamers, Nucleotide/genetics* ; Antigens, CD20/metabolism* ; Ligands

Cancer ranks as the second leading cause of death globally and has surpassed cardiovascular diseases to become the primary cause of mortality in developed countries. Cancer stem cells (CSCs), which play crucial roles in cancer recurrence, metastasis, and drug resistance, have attracted significant attention in targeted therapeutic strategies. Aptamers, with unique three-dimensional structures capable of specifically recognizing the surface markers of CSCs, show promising potential in targeted drug delivery systems. Compared with conventional antibodies, aptamers are praised for small molecular weights, low production costs, and easy chemical modification. This review systematically summarizes recent advances in aptamer research targeting the surface markers of CSCs, with particular emphasis on aptamer-drug conjugate systems targeting the markers including EpCAM, CD133, CD44, and ABCG2. Both in vitro cellular studies and in vivo animal models have demonstrated the definite anti-cancer efficacy of aptamer-based drug delivery systems, which are of great significance to develop novel therapeutic strategies and improving the therapeutic effects of CSC-targeted treatment. Thus, aptamer-based drug delivery system has broad application prospects in the field of precise cancer treatment.
Humans ; Neoplastic Stem Cells/metabolism* ; Aptamers, Nucleotide/therapeutic use* ; Drug Delivery Systems/methods* ; Neoplasms/drug therapy* ; Biomarkers, Tumor/metabolism* ; Animals ; Epithelial Cell Adhesion Molecule ; AC133 Antigen ; Hyaluronan Receptors

OBJECTIVE: To select specific DNA aptamer for determining ketamine by FluMag-SELEX. METHODS: Based on magnetic beads with tosyl surface modification as solid carrier and ketamine as target, a random ssDNA library with total length of 78 bp in vitro was compounded. After 13 rounds screening, DNA cloning and sequencing were done. Primary and secondary, structures were analyzed. The affinity, specificity and Kd values of selected aptamer were measured by monitoring the fluorescence intensity. RESULTS: Two ssDNA aptamers (Apt#4 and Apt#8) were successfully selected with high and specific abilities to bind ketamine as target with Kd value of 0.59 and 0.66 μmol/L. The prediction of secondary structure was main stem-loop and G-tetramer. The stem was the basis of stability of aptamer's structure. And loop and G-tetramer was the key of specific binding of ketamine. CONCLUSION FluMag-SELEX can greatly improve the selection efficiency of the aptamer, obtain the ketamine-binding DNA aptamer, and develop a new method for rapid detection of ketamine.
Aptamers, Nucleotide/metabolism* ; DNA ; DNA, Single-Stranded/genetics* ; In Vitro Techniques ; Ketamine/metabolism* ; Oligonucleotides ; SELEX Aptamer Technique/methods*

A15, a DNA aptamer with binding specificity for U87 glioma cells stably overexpressing the epidermal growth factor receptor variant III (U87-EGFRvIII), was generated by cell systematic evolution of ligands by exponential enrichment (cell-SELEX) using a random nucleotide library. Subsequently, we established a cell enzyme-linked assay (cell-ELA) to detect the affinity of A15 compared to an EGFR antibody. We used A15 as a detection probe and cultured U87-EGFRvIII cells as targets. Our data indicate that the equilibrium dissociation constants (K(d)) for A15 were below 100 nmol/L and had similar affinity compared to an EGFR antibody for U87-EGFRvIII. We demonstrated that the cell-ELA was a useful method to determine the equilibrium dissociation constants (K(d)) of aptamers generated by cell-SELEX.
Aptamers, Nucleotide ; metabolism ; Brain Neoplasms ; metabolism ; Cell Line, Tumor ; Glioma ; metabolism ; pathology ; Humans ; Mutation ; Protein Binding ; Receptor, Epidermal Growth Factor ; genetics ; metabolism ; SELEX Aptamer Technique ; methods

Aptamers are capable of binding a wide range of biomolecular targets with high affinity and specificity. It has been widely developed for diagnostic and therapeutic purposes. Because of unique three dimensional structures and cell-membrane penetration, aptamers inhibit virus infection not only through binding specific target, such as the viral envelope, genomic site, enzyme, or other viral components, but also can be connected to each other or with siRNA jointly achieve antiviral activity. Taking human immunodeficiency virus and hepatitis C virus as examples, this paper reviewed the effects and mechanisms of aptamers on disturbing viral infection and replication steps. It may provide an insight to the development of aptamer-based new antiviral drugs.
Antiviral Agents ; pharmacology ; Aptamers, Nucleotide ; pharmacology ; therapeutic use ; Genome, Viral ; drug effects ; HIV ; drug effects ; HIV Reverse Transcriptase ; metabolism ; Hepacivirus ; drug effects ; genetics ; Humans ; Macular Degeneration ; drug therapy ; Neoplasms ; drug therapy ; Oligodeoxyribonucleotides ; therapeutic use ; RNA, Small Interfering ; pharmacology ; SELEX Aptamer Technique ; Viral Envelope Proteins ; metabolism ; Virus Replication ; drug effects

Aptamers are synthetic, relatively short (e.g., 20-80 bases) RNA or ssDNA oligonucleotides that can bind targets with high affinity and specificity, similar to antibodies, because they can fold into unique, three-dimensional shapes. For use in various assays and experiments, aptamers have been conjugated with biotin or digoxigenin to form complexes with avidin or anti-digoxigenin antibodies, respectively. In this study, we developed a method to label the 5' ends of aptamers with cotinine, which allows formation of a stable complex with anti-cotinine antibodies for the purpose of providing another affinity unit for the application in biological assays using aptamers. To demonstrate the functionality of this affinity unit in biological assays, we utilized two well-known aptamers: AS1411, which binds nucleolin, and pegaptanib, which binds vascular endothelial growth factor. Cotinine-conjugated AS1411/anti-cotinine antibody complexes were successfully applied to immunoblot, immunoprecipitation, and flow cytometric analyses, and cotinine-conjugated pegaptanib/anti-cotinine antibody complexes were used successfully in enzyme immunoassays. Our results show that cotinine-conjugated aptamer/anti-cotinine antibody complexes are an effective alternative and complementary technique for aptamer use in multiple assays and experiments.
Animals ; Antibodies, Anti-Idiotypic/immunology/metabolism ; *Aptamers, Nucleotide/chemistry/immunology ; Biological Assay ; *Cotinine/administration & dosage/chemistry ; Flow Cytometry ; Hep G2 Cells ; Humans ; Mice ; NIH 3T3 Cells ; Phosphoproteins/*chemistry/immunology ; Protein Binding ; RNA-Binding Proteins/*chemistry/immunology ; *Vascular Endothelial Growth Factor A/chemistry/immunology

RNA interference (RNAi), as a new technology of gene therapy, has been used in the studies of many diseases in vitro, however, targeting delivery of small interference RNA (siRNA) is still a bottleneck for clinical therapy of siRNA agents. Aptamer is a group of oligonucleotides with high affinity and targeting, and is becoming another important means of delivery for siRNA. In this review, we summarized siRNA delivery obstacles in vivo and recent attractive developments increatively using cell-internalizing aptamers to deliver siRNAs to target cells.
Aptamers, Nucleotide ; administration & dosage ; metabolism ; Drug Delivery Systems ; methods ; Humans ; Neoplasms ; therapy ; RNA Interference ; RNA, Small Interfering ; administration & dosage ; metabolism ; SELEX Aptamer Technique

Molecular imaging has greatly advanced basic biology and translational medicine through visualization and quantification of single/multiple molecular events temporally and spatially in a cellular context and in living organisms. Aptamers, short single-stranded nucleic acids selected in vitro to bind a broad range of target molecules avidly and specifically, are ideal molecular recognition elements for probe development in molecular imaging. This review summarizes the current state of aptamer-based biosensor development (probe design and imaging modalities) and their application in imaging small molecules, nucleic acids and proteins mostly in a cellular context with some animal studies. The article is concluded with a brief discussion on the perspective of aptamer-based molecular imaging.
Animals ; Aptamers, Nucleotide ; genetics ; metabolism ; Base Sequence ; Biosensing Techniques ; Humans ; Molecular Imaging ; methods

OBJECTIVE: To screen aptamers binding CD33+/CD34- cells from patients with acute myeloblastic leukemia M2 subtype (AML-M2). METHODS: CD33+/CD34- cells from patients with AML-M2 were taken as targeted cells, CD33+/ CD34- cells from normal people were taken as anti-selecting cells, and aptamers in the single strand deoxyribonucleic acid (ssDNA) library were then selected repeatedly by cell-systematic evolution of ligands by exponential enrichment (C-SELEX) technology, and amplified by polymerase chain reaction (PCR) to generate sub-ssDNA library. During the experiment, PCR amplification with fluorescently labeled primer and flow cytometry were performed to analyze the aptamers'enrichment of sub-library, and the final round product of the sub-ssDNA library was cloned. After the sequencing, the primary and secondary structures of the aptamers were analyzed. RESULTS: Electrophoresis indicated that the product of PCR amplification for each round subssDNA library was able to see a clear DNA band in the agarose gel. After 13 rounds of screening, the fluorescence intensity of the sub-ssDNA library binding the cells ranged from 2.14% to 51.12%, reaching a steady state at the 13th round. A total of 30 clones were selected and sequenced, 22 of which contained 1 of the 4 conserved sequences of AAGTA, TATCT, AGATG and AAATT in their primary structure, but the remained eight aptamers contained none of the conserved sequence. Secondary structure analysis indicated that four stem-loops and loop simulation convex structures existed in the aptamers. CONCLUSION C-SELEX technology can be used to screen the aptamers binding primary cells from patients with leukemia. The aptamers selected from the CD33+/CD34- cells from the patients of AML-M2 subtype might be used for the diagnosis and treatment for leukemia.
Adolescent ; Adult ; Antigens, CD34 ; genetics ; immunology ; Antigens, Differentiation, Myelomonocytic ; genetics ; immunology ; Aptamers, Nucleotide ; genetics ; metabolism ; DNA, Single-Stranded ; genetics ; Female ; Humans ; Leukemia, Myeloid, Acute ; genetics ; immunology ; Male ; Middle Aged ; SELEX Aptamer Technique ; Sialic Acid Binding Ig-like Lectin 3 ; genetics ; immunology ; Young Adult

A little is known about the specific marker on the surface of acute leukemia cells, leading to the lack of the specific diagnosis method for acute leukemia. Therefore, in this study, cell-systematic evolution of ligands by exponential enrichment (cSELEX) was performed to screen the aptamers binding to CD33(+)/CD34(+) cells from the patients with acute myeloblastic leukemia (AML) of M(2) subtype (AML-M₂) so as to provide the basis for finding the specific marker on the surface of AML-M(2) CD33(+)/CD34(+) cells. Firstly, AML-M₂ CD33(+)/CD34(+) cells were sorted and used as targeted cells, and normal CD33(+)/CD34(+)cells were used as counter-targeted cells; the aptamers binding to CD33(+)/CD34(+) cells from patients with AML-M₂ were screened from the single strand deoxyribonucleic acid (ssDNA) library by cSELEX. Subsequently, each aptamer structure was analyzed after cloning and sequencing. The results indicated that after 13 round of screenings, the enrichment of aptamers in the ssDNA library was ranged from 0.7% to 52.9%, and reached steady state at 13th round screening. Sequence analysis for 30 aptamers showed that most of the aptamers born one of the three conserved sequences of CCCCT, CTCTC, and CTCAC. Secondary structure analysis indicated that three different secondary structures existed in these aptamers. It is concluded that the aptamers binding to the AML-M(2) CD33(+)/CD34(+) cells are successfully screened, which lay the basis for further looking for the specific marker on the surface of AML-M₂ CD33(+)/CD34(+) cells, and the molecular diagnosis of the AML-M₂ leukemia.
Antigens, CD ; genetics ; immunology ; Antigens, CD34 ; genetics ; immunology ; Antigens, Differentiation, Myelomonocytic ; genetics ; immunology ; Aptamers, Nucleotide ; metabolism ; Biomarkers ; Flow Cytometry ; Humans ; Immunophenotyping ; Leukemia, Myeloid, Acute ; genetics ; immunology ; Nucleic Acid Conformation ; SELEX Aptamer Technique ; Sialic Acid Binding Ig-like Lectin 3