ABSTRACT
Tumor has become the second most serious disease that threatens human health and life. Treating with chemical drugs (referred to as chemotherapy) is the most basic treatment, but most chemotherapeutic drugs cause damage to normal tissues. It is a difficult problem in the field of biomedical research that how to deliver anti-tumor drugs more efficiently, increase the concentration of drugs in tumor tissues, enhance the anti-tumor effect, and decrease the drug distribution in normal tissues to weaken the damage to normal tissues. In order to achieve the goals of accurate delivery of anti-tumor drugs and synergism and attenuation, the researchers used systematic evolution of ligands by exponential enrichment technology (SELEX technology) to screen aptamers that can specifically target tumor markers or tumor cells, and designed the novel liposome targeting drug delivery system with aptamers as targeting molecules (ligands). This paper briefly introduced nucleic acid aptamer technology and common tumor markers, and reviewed the research advances on the antitumor effect of aptamer-liposome drug delivery system. It will provide references for the selection of appropriate tumor markers as targets and the application of aptamer technology in the research and development of high-efficiency and low-toxicity liposome targeting agents of anti-tumor traditional Chinese medicine. Meanwhile, it is of great significance for promoting the application of aptamer technology in targeted drug delivery systems.
ABSTRACT
Nucleic acid aptamer is an oligonucleotide sequence screened by the exponential enrichment ligand system evolution technology (SELEX). Previous studies have shown that nucleic acid aptamer has a good application prospect in tumor diagnosis and treatment. Therefore, we reviewed the selection and identification of nucleic acid aptamer of lung cancer cells in recent years, and discussed the effect of aptamer as targeting drugs and targeting vectors on the diagnosis of tumors, which provide a new idea for early diagnosis and treatment of tumor.
ABSTRACT
An in vitro synthesized random ssDNA library was subjected to 12 rounds of selection against anti-screening cells and sieving cells by SELEX. Normal and inflammatory cervical exfoliation cells were selected as anti-screening cells, and the cervical exfoliation cells of low-grade squamous intraepithelial lesion (CIN1), high-grade squamous intraepithelial lesion (CIN2, CIN3) and cervical carcinoma were selected as sieving cells during the screening process. Then, the highly specific aptamer CIN-Ap4 was established by the analysis of the specificity, affinity and cell immunofluorescence, which can be used as biomarker for Cervical Intraepithelial Neoplasia. Prime Premier 5.0 was applied to design a random ssDNA library. According to the fixed sequence at both ends of the library, a pair of primers were designed and synthesized. At the same time, the optimal annealing temperature, cycle times and primer concentration ratio of PCR procedure were selected. The results under the optimal condition are shown as follows. In the 50 μL reaction system, the optimum reaction conditions of symmetry PCR are as follows: annealing temperature is 49.5 ℃, number of cycles is 15. The optimal reaction conditions of indirect asymmetric PCR are as follows: the primer concentration ratio is 80:1, and the number of cycles is 35. The experiment proves that the oligonucleotide library is constructed successfully, and the highly specific dsDNA and ssDNA can be obtained under optimal PCR conditions with good repeatability, which establishes the foundation for the further exploration and experimentation.
ABSTRACT
Screening aptamers using nano-materials ( such as graphene oxide, gold nanoparticle, carbon nano-tube, etc. ) that can quench fluorescence and absorb single stranded DNA using hydrogen bond, π-πbond, charge transfer, and other non-covalent ways to combine with ssDNA, but without other conformational DNA, can excellently separate specific aptamers from non-specific ones. In this case, we can shorten the cycle numbers, enhance the success rate, and reduce the labour intensity of systematic evolution of ligands by exponential enrichment ( SELEX) . Especially for small molecular target, due to its difficulty in immobilization and small size, it is difficult to use traditional methods such as SPR-SELEX or affinity-SELEX for screening. In this experiment, polydopamine nanospheres ( MNPs@PDAs) were used to screen the Lomefloxacin. Also, we used magnetic separation technique to screen small molecular target rapidly. The interaction between aptamer candidates and the target could be monitored by recovery ratio of ssDNA and the whole MNPs@PDAs-SELEX process was performed through seven-round selection. As a result, we successfully obtained the aptamer named AF-3 which could recognize the lomefloxacin with high affinity (KD=(17. 57±0. 5) nmol/L). This screening method based on MNPs@PDAs makes it a promising reagent in the efficient aptamers selection of other targets.
ABSTRACT
Aptamers are oligonucleotides which can combine targets with high affinity and specificity.Graphene oxide is a kind of new material with many unique physical and chemical properties.Recently, graphene oxide is gradually applied to the field of aptamers and has made a series of progress.This review focused on the application progress of graphene oxide and aptamers in the detection of different targets including small molecules and metal ion, biomacromolecules and cells in order to provide references for the mass application of graphene oxide and aptamers in the field of detection .
ABSTRACT
In this research, Casuarina eguisetifolia Linn was used to verify the broadly suitability of DNA bar-codes in identification of Li-medicine plants and systematic development of species. The genomic DNA of 22 samples collected C. eguisetifolia and its adulterants were amplified by 4 pairs of primers respectively (ITS (inter-nal transcribed spacer), ITS2 (internal transcribed spacer 2), trnH-psbA , rbcL) and sequenced bi-directionally. Obtained sequences were assembled using CodonCode Aligner. The dates were analysised using MEGA5.1 in ac-cordance with the kimura 2-parameter (K2P) model. The neighbor-joining (NJ) phylogenetic trees were construct-ed. Our study demonstrated the efficacy of ITS/ITS2 to distinguish between C. eguisetifolia and other adulterants species at the molecular level. Comparative to the primer of trnH-psbA and rbcL, there was a obviously DNA gap. The NJ trees showed that the several species of Casuarina can be classified to same types to show a obvi-ously monophyly, which the nearest family was Guttiferae. Therefore, ITS/ITS2 regions can accurately distinguish the original plant of Li-medicine. The systematic evolution of Casuarina can be verified in the molecular level.
ABSTRACT
Hepatitis B virus surface antigen(HBsAg),a specific antigen on the membrane of Hepatitis B virus (HBV)-infected cells,provides a perfect target for therapeutic drugs.The development of reagents with high affinity and specificity to the HBsAg is of great significance to the early-stage diagnosis and treatment of HBV infection.Herein,we report the selection of RNA aptamers that can specifically bind to HBsAg protein and HBsAg-positive hepatocytes.One high affinity aptamer,HBs-A22,was isolated from an initial 115 mer library of ～1.1×1015 random-sequence RNA molecules using the SELEX procedure.The selected aptamer HBs-A22 bound specifically to hepatoma cell line HepG2.2.15 that expresses HBsAg but did not bind to HBsAg-devoid HepG2 cells.This is the first reported RNA aptamer which could bind to a HBV specific antigen.This newly isolated aptamer could be modified to deliver imaging,diagnostic,and therapeutic agents targeted at HBV-infected cells.
ABSTRACT
Aptamers are small single-stranded nucleic acid molecules that bind a target protein with high affinity and specificity. Due to their stability, low toxicity and immunogenicity, as well as improved safety, aptamers are attractive alternatives to antibody and are therefore suitable for in vivo applications. Aptamers are typically isolated, through a process termed SELEX (systematic evolution of ligands by exponential enrichment), from combinatorial libraries with desired proteins. In the present review, the recent non-conventional aptamer selection process will be discussed together with an overview on the aptamer application in cancer diagnosis and therapy.
ABSTRACT
Objective To select the aptamer to an extracellular soluble fragment of recombinant human TGF-? receptor Ⅱ (TGF-? RⅡ) in order to antagonize TGF-? effectively by using systematic evolution of ligants by exponential enrichment (SELEX). Methods Initial random RNA library was transcripted in vitro from ssDNA 5′-TAATACGACTCACTATAGGGAGGACGATGCGG-N60-CAGACGACTCCCCGA-3′; rhTGF-? RⅡ was used as target protein. Totally,selection of 8 times was carried out in SELEX experiment. Membrane binding assay was performed to detect the evolution of enriched RNA library; Electrophoretic mobility shift assay (EMSA) was done to determine the affinity between the selected nucleic acid sequence and TGF-? RⅡ. Results Evolution of the enriched RNA library along the increased affinity to TGF-? RⅡ was observed with the development of selection. Two types of dominant sequences were isolated and named as sequence A and sequence B. In membrane binding assay,both sequences A and B showed obvious affinity to TGF-? RⅡ. However,no retarded bands were seen in EMSA. Conclusion The affinity of sequences A and B to TGF-? RⅡ is beyond satisfaction. However,possible sequences with improved affinity to TGF-? RⅡ can be selected by post-SELEX on the basis of candidate sequences A and B.
ABSTRACT
Objective To compare the effect of different partition of nucleic acid protein complex on the affinity of enriched library in systematic evolution of ligands by exponential enrichment (SELEX). Methods Two protocols were adopted to select the enriched library to transforming growth factor ? receptor Ⅱ(TGF ? RⅡ). Protocol 1: protein was absorbed on the surface of 96 well plate; then, selection was carried out; the binding nucleotide acids were eluted from the supporter directly. Protocol 2: selection was done in solution; nucleotide acid protein complex was captured in nitrocellulose membrane; the binding nucleotide acids were obtained from membrane. Filter biding assay and gel shift assay were performed to detect the affinity of the enriched ssDNA library from different protocols. Results After 4 rounds of selection, the affinity to TGF ? RⅡ was obviously improved in the enriched library from protocol 2 compared with the initial library, while no such improvement was found in the enriched library from protocol 1. Conclusion In the SELEX experiment, the way of selection in solution, then partition of the binding nucleotide acids in filter is easier to enrich the binding fragment from initial ssDNA random library, compared with the way of fixation of target protein to solid supporter, then selection between the solid phase and liquid phase and elution of the binding nucleotide acids from supporter.