Multifunctional aptamer-silver conjugates as theragnostic agents for specific cancer cell therapy and fluorescence-enhanced cell imaging

Metal Nanoparticle-Based Biosensors for the Early Diagnosis of Infectious Diseases Caused by ESKAPE Pathogens in the Fight against the Antimicrobial-Resistance Crisis

The species included in the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and the genus Enterobacter) have a high capacity to develop antimicrobial resistance (AMR), a health problem that is already among the leading causes of death and could kill 10 million people a year by 2050. The generation of new potentially therapeutic molecules has been insufficient to combat the AMR "crisis", and the World Health Organization (WHO) has stated that it will seek to promote the development of rapid diagnostic strategies. The physicochemical properties of metallic nanoparticles (MNPs) have made it possible to design biosensors capable of identifying low concentrations of ESKAPE bacteria in the short term; other systems identify antimicrobial susceptibility, and some have been designed with dual activity in situ (bacterial detection and antimicrobial activity), which suggests that, in the near future, multifunctional biosensors could exist based on MNPs capable of quickly identifying bacterial pathogens in clinical niches might become commercially available. This review focuses on the use of MNP-based systems for the rapid and accurate identification of clinically important bacterial pathogens, exhibiting the necessity for exhaustive research to achieve these objectives. This review focuses on the use of metal nanoparticle-based systems for the rapid and accurate identification of clinically important bacterial pathogens.

Improving synthesis and binding affinities of nucleic acid aptamers and their therapeutics and diagnostic applications

Nucleic acid aptamers have captivated the attention of analytical and medicinal scientists globally due to their several advantages as recognition molecules over conventional antibodies because of their small size, simple and inexpensive synthesis, broad target range, and high stability in varied environmental conditions. These recognition molecules can be chemically modified to make them resistant to nuclease action in blood serum, reduce rapid renel clearance, improve the target affinity and selectivity, and make them amenable to chemically conjugate with a support system that facilitates their selective applications. This review focuses on the development of efficient aptamer candidates and their application in clinical diagnosis and therapeutic applications. Significant advances have been made in aptamer-based diagnosis of infectious and non-infectious diseases. Collaterally, the progress made in therapeutic applications of aptamers is encouraging, as evident from their use in diagnosing cancer, neurodegenerative diseases, microbial infection, and in imaging. This review also updates the progress on clinical trials of many aptamer-based products of commercial interests. The key development and critical issues on the subject have been summarized in the concluding remarks.

Intracellular Glucose-Depriving Polymer Micelles for Antiglycolytic Cancer Treatment

A new anticancer strategy to exploit abnormal metabolism of cancer cells rather than to merely control the drug release or rearrange the tumor microenvironment is reported. An antiglycolytic amphiphilic polymer, designed considering the unique metabolism of cancer cells (Warburg effect) and aimed at the regulation of glucose metabolism, is synthesized through chemical conjugation between glycol chitosan (GC) and phenylboronic acid (PBA). GC-PBA derivatives form stable micellar structures under physiological conditions and respond to changes in glucose concentration. Once the micelles accumulate at the tumor site, intracellular glucose capture occurs, and the resultant energy deprivation through the inhibition of aerobic glycolysis remarkably suppresses tumor growth without significant side effects in vivo. This strategy highlights the need to develop safe and effective cancer treatment without the use of conventional anticancer drugs.

Vitamin D Inhibits the Early Aggregation of α-Synuclein and Modulates Exocytosis Revealed by Electrochemical Measurements

Alpha-synuclein (α-Syn) localizes at presynaptic terminal and modulates synaptic functions. Increasing evidence demonstrate that α-Syn oligomers, forming at the early of aggregation, are cytotoxic and is thus related to brain neurodegenerative diseases. Herein, we find that vitamin D (VD) can reduce neurocytotoxicity. The reduced neurocytotoxicity might be attributed to the less amount of large-sized α-Syn oligomers inhibited by VD, measured by electrochemical collision at single particle level, which are not observable with traditionally ensembled method. Single-cell amperometry (SCA) results show that VD can recover the amount of neurotransmitter release during exocytosis induced by α-Syn oligomers, further verifying the neuroprotection of VD. Our study reveals the neuroprotective role of VD through inhibiting α-Syn aggregation, which is envisioned to be of great importance in treatment and prevention of the neurodegenerative diseases.

A novel method combining aptamer-Ag10NPs based microfluidic biochip with bright field imaging for detection of KPC-2-expressing bacteria

The β-lactam drugs resistance poses a serious threat to human health throughout the world. Klebsiella pneumoniae carbapenemase 2 (KPC-2) is a carbapenemase that produced in bacteria can hydrolyze carbapenems, which typically considered as the antibiotics of last resort. Therefore, there is an urgent need to quickly and accurately detect whether bacteria express KPC-2. In this paper, a PDMS/glass microfluidic biochip integrated with aptamer-modified Ag₁₀NPs nano-biosensors was developed for rapid, simple and specific pathogenic bacteria detection, more importantly, the biochip was combined with bright field imaging, then the captured bacteria could be observed and counted directly without using extra chemical labeling. KPC-2-expressing Escherichia coli (KPC-2 E.coli) was used as the target bacterium with a detected limit of 10² CFU and capture efficiency exceeded 90%. This method is remarkably specific towards KPC-2 E.coli over other non-resistant bacteria, and pathogen assay only takes ∼1 h to complete in a ready-to-use microfluidic biochip. Furthermore, the effective capture and fast counting of microfluidic biochip system demonstrates its potential for the rapid detection of antibiotic-resistant bacteria.

Aptamer-Modified Nanoparticles in Medical Applications

Since aptamers have been selected against a broad range of target structures of medical interest and nanoparticles are available with diverse properties, aptamer-modified nanoparticles can be used in various diagnostic and therapeutic applications. While the aptamer is responsible for specificity and affinity of the conjugate, the nanoparticles' function varies from signal generation in diagnostic approaches to drug loading in drug delivery systems. Within this chapter different medical applications of aptamer-modified nanoparticles will be summarized and underlying principles will be described.

Sulphur-doped carbon dots as a highly efficient nano-photodynamic agent against oral squamous cell carcinoma

OBJECTIVES

Photodynamic therapy (PDT) is a novel non-invasive therapeutic method, which has been widely applied for the treatment of human oral cancers. However, the problems of undesirable singlet oxygen (1 O2 ) quantum yields and long-term phototoxicity were inevitable during the application of traditional photosensitizers. Therefore, it is necessary to explore novel photosensitizers for the improvement of therapeutic effects. In our study, the sulphur-doped carbon dots (S-CDs) of high yield of singlet oxygen (1 O2 ) were synthesized as a nano-photosensitizer for OSCC to improve the PDT efficacy in clinical practice.

MATERIALS AND METHODS

After synthesis of the novel S-CDs, the size, morphologic characteristics, surface potential and yield of singlet oxygen (1 O2 ) were determined. In vitro study was performed to compare the therapeutic effect as well as the biocompatibility of the novel S-CDs to those of 5-ALA. Besides, possible mechanism of action was illustrated.

RESULTS

After synthesis of the novel S-CDs, the size, morphologic characteristics, surface potential and yield of singlet oxygen (1 O2 ) were determined. In vitro study was performed to compare the therapeutic effect as well as the biocompatibility of the novel S-CDs to those of 5-ALA. Besides, possible mechanism of action was illustrated.

CONCLUSIONS

These data from the in vitro study demonstrated the promising safety profile of the low dose (nmol/L) S-CDs, which indicated the novel S-CDs could be used as a promising photodynamic agent for oral cancer therapy.

Dynamically Monitoring the Clonal Evolution of Lung Cancer Based on the Molecular Characterization of Circulating Tumor Cells Using Aptamer Cocktail-Modified Nanosubstrates

Dynamically monitoring the clonal evolution of lung cancer and performing molecular analyses on tumor cells are challenging but necessary tasks to adjust therapeutic interventions and evaluate treatment efficacy. Circulating tumor cells (CTCs), as a "liquid biopsy", may offer an auxiliary tool to identify phenotypic transformation of solid tumors at primary or metastatic sites and uncover their corresponding molecular variation. Herein, we developed an aptamer-modified PEG-PLGA-nanofiber (PPN) microfluidic system optimized for recognizing rare CTC subtypes in lung cancer patients. This unique purification system can be adopted to monitor the clonal evolution of solid tumors by following the intrinsic immunophenotypes of CTCs, while significantly enhancing capture efficiency for polyclonal-derived tumor cells, further facilitating therapeutic evaluation via dynamic CTC enumeration. Combining with downstream single-cell sequencing, the aptamer-modified-PPN microfluidic system was able to provide early insight into tumor heterogeneity and predict histologic transformation in advance, broadening its clinical applications in lung cancer patients.

Nucleic Acid Aptamer: A Novel Potential Diagnostic and Therapeutic Tool for Leukemia

Leukemia immunotherapy has been dominant via using synthetic antibodies to target cluster of differentiation (CD) molecules, nevertheless inevitable cytotoxicity and immunogenicity would limit its development. Recently, increasing reports have focused on nucleic acid aptamers, a class of high-affinity nucleic acid ligands. Aptamers purportedly serve as “chemical antibodies”, have negligible cytotoxicity and low immunogenicity, and would be widely applied for the therapy and diagnosis of various diseases, especially leukemia. In the preclinical applications, nucleic acid aptamers have displayed the augmented specificity and selectivity via recognizing targets on leukemia cells based on unique three-dimensional conformations. As small molecules with nucleic acid characteristics, aptamers need to be chemically modified to resist nuclease degradation, renal clearance and improve binding affinities. Moreover, aptamers can be linked with neoteric detection techniques to enhance sensitivity and selectivity of diagnosis and therapy. In this review, we summarized aptamers’ preparation, chemical modification and conjugation, and discussed the application of aptamers in diagnosis and treatment of leukemia through highly specifically recognizing target molecules. Significantly, the application prospect of aptamers in fusion genes would be introduced.

Unraveling Determinants of Affinity Enhancement in Dimeric Aptamers for a Dimeric Protein

High-affinity aptamers can be derived de novo by using stringent conditions in SELEX (Systematic Evolution of Ligands by EXponential enrichment) experiments or can be engineered post SELEX via dimerization of selected aptamers. Using electrophoretic mobility shift assays, we studied a series of heterodimeric and homodimeric aptamers, constructed from two DNA aptamers with distinct primary sequences and secondary structures, previously isolated for VEGF-165, a homodimeric protein. We investigated four factors envisaged to impact the affinity of a dimeric aptamer to a dimeric protein: (1) length of the linker between two aptamer domains, (2) linking orientation, (3) binding-site compatibility of two component aptamers in a heterodimeric aptamer, and (4) steric acceptability of the two identical aptamers in a homodimeric aptamer. All heterodimeric aptamers for VEGF-165 were found to exhibit monomeric aptamer-like affinity and the lack of affinity enhancement was attributed to binding-site overlap by the constituent aptamers. The best homodimeric aptamer showed 2.8-fold better affinity than its monomeric unit (K_d = 13.6 ± 2.7 nM compared to 37.9 ± 14 nM), however the barrier to further affinity enhancement was ascribed to steric interference of the constituent aptamers. Our findings point to the need to consider the issues of binding-site compatibility and spatial requirement of aptamers for the development of dimeric aptamers capable of bivalent recognition. Thus, determinants highlighted herein should be assessed in future multimerization efforts.

High-density micro-well array with aptamer-silver conjugates for cell sorting and imaging at single cells

Characterizing cell behavior is important to modern medical diagnoses as the changes of cell behavior are often indicators of huge diseases. In order to gain enough information about cells, developing novel methods of cell sorting and imaging is an important task. With development of micro-fabrication technologies, more advanced miniaturized devices are applied to cell research. Here, a portable and easy-to-use chip with high-density periodic micro-well array is designed and fabricated to capture target cells specifically. Combining with aptamer-silver conjugates and FAM functioned report probes, the sandwich assay was successfully applied for imaging cells. Any well of the chip is carefully designed to provide abundant information on single cells. Since there are 19,200 microwells in a single chip, more information is available. Compared to other cells, such as HEK-293, MCF-7, U₂OS and Ramos cells, the sandwich assay shows high specificity towards target cell CCRF-CEM. What's more, the applications of the chip can be further expanded to other cells imaging if suitable aptamers were selected. This high-density micro-well array of aptamer-silver conjugates is hopeful to play an important role in medical diagnosis in the future.

Molecular Engineering of Functional Nucleic Acid Nanomaterials toward In Vivo Applications

Recent advances in nanotechnology and engineering have generated many nanomaterials with unique physical and chemical properties. Over the past decade, numerous nanomaterials are introduced into many research areas, such as sensors for environmental monitoring, food safety, point-of-care diagnostics, and as transducers for solar energy transfer. Meanwhile, functional nucleic acids (FNAs), including nucleic acid enzymes, aptamers, and aptazymes, have attracted major attention from the biomedical community due to their unique target recognition and catalytic properties. Benefiting from the recent progress of molecular engineering strategies, the physicochemical properties of nanomaterials are endowed by the target recognition and catalytic activity of FNAs in the presence of a target analyte, resulting in numerous smart nanoprobes for diverse applications including intracellular imaging, drug delivery, in vivo imaging, and tumor therapy. This progress report focuses on the recent advances in designing and engineering FNA-based nanomaterials, highlighting the functional outcomes toward in vivo applications. The challenges and opportunities for the future translation of FNA-based nanomaterials into clinical applications are also discussed.

Using N-doped Carbon Dots Prepared Rapidly by Microwave Digestion as Nanoprobes and Nanocatalysts for Fluorescence Determination of Ultratrace Isocarbophos with Label-Free Aptamers

The strongly fluorescent and highly catalytic N-doped carbon dots (CDN) were rapidly prepared by a microwave irradiation procedure and were characterized by electron microscopy (EM), laser scattering, infrared spectroscopy (IR), and by their fluorescence spectrum. It was found that the CDN had a strong catalytic effect on the fluorescence reaction of 3,3',5,5'-tetramethylbenzidine hydroxide ((TMB)⁻H₂O₂) which produced the oxidation product of TMB (TMBOX) with strong fluorescence at 406 nm. The aptamer (Apt) was adsorbed on the CDN surfaces which weakened the fluorescence intensity due to the inhibition of catalytic activity. When the target molecule isocarbophos (IPS) was added, it reacted with the Apt to form a stable conjugate and free CDN which restored the catalytic activity to enhance the fluorescence. Using TMBOX as a fluorescent probe, a highly sensitive nanocatalytic method for determination of 0.025⁻1.5 μg/L IPS was established with a detection limit of 0.015 μg/L. Coupling the CDN fluorescent probe with the Apt⁻IPS reaction, a new CD fluorescence method was established for the simple and rapid determination of 0.25⁻1.5 μg/L IPS with a detection limit of 0.11 μg/L.

Surface Modification of Macrophages with Nucleic Acid Aptamers for Enhancing the Immune Response against Tumor Cells

Antigen-presenting cells play a dominant role in cancer immunotherapy. Tumor cells, however, can still resort to several mechanisms of immune evasion that ultimately lead to the development of tumor tissues. In the current study, we performed surface modification of live macrophages with nucleic acid aptamers with the aim to enhance their affinity for tumor cells. Intercellular adhesion of tumor cells to surface-modified macrophages and the functions of the macrophages when in contact with tumor cells were investigated. To immobilize thiol-terminated nucleic acid aptamers that showed high affinity for the membrane protein of the tumor cells, methacryloyl groups were delivered into the sialic acids of the macrophages via metabolic glycoengineering (MGE). The proposed surface modification was cytocompatible and did not induce any undesirable activation of macrophages. According to the cell proliferation assay, the density of aptamers immobilized on a macrophage was found to decrease over time. However, the presence of aptamers on the cell surface was observed for more than 24 h after the immobilization. The number of adherent tumor cells on aptamer-immobilized macrophages was significantly larger than that of non-immobilized macrophages. Although the number of adherent tumor cells on aptamer-immobilized macrophages was not influenced by the pretreatment of doxorubicin to induce apoptosis in tumor cells, the apoptosis-induced tumor cells were highly phagocytosed by the aptamer-immobilized macrophages. The secretion amount of proinflammatory cytokines (TNF-α and IL-12) from the macrophages was coincident with the phagocytic index, which increased with the phagocytic uptake of tumor cells by the macrophages. In addition, the expression level of the major histocompatibility complex (MHC) class I and II molecules, required for antigen presentation, increased in nucleic acid aptamer-immobilized macrophages. Overall, the surface modification of macrophages with nucleic acid aptamers improved the tumor cell recognition of macrophages, indicating that the combination of cell surface engineering and anticancer drug treatment could constitute a promising strategy for tumor cell elimination.

A direct assay of carboxyl-containing small molecules by SALDI-MS on a AgNP/rGO-based nanoporous hybrid film

Silver nanoparticles (AgNPs) and reduced graphene oxide (rGO) hybrid nanoporous structures fabricated by the layer-by-layer (LBL) electrostatic self-assembly have been applied as a simple platform for the rapid analysis of carboxyl-containing small molecules by surface-assisted laser desorption/ionization (D/I) mass spectrometry (SALDI-MS). By the simple one-step deposition of analytes onto the (AgNP/rGO)9 multilayer film, the MS measurements of various carboxyl-containing small molecules (including amino acids, fatty acids and organic dicarboxylic acids) can be done. In contrast to other energy transfer materials relative to AgNPs, the signal interferences of a Ag cluster (Agn(+) or Agn(-)) and a C cluster (Cn(+) or Cn(-)) have been effectively reduced or eliminated. The effects of various factors, such as the pore structure and composition of the substrates, on the efficiency of D/I have been investigated by comparing with the (AgNP)9 LBL nanoporous structure, (AgNP/rGO)9/(SiO2NP)6 LBL multilayer film and AgNP/prGO nanocomposites.

Specific detection of cancer cells through aggregation-induced emission of a light-up bioprobe

A cancer cell specific aptamer was labeled with an aggregation-induced emission (AIE) probe for the first time. Using it as a light-up bioprobe, a specific cancer cell detection method is developed.

Fabrication of multifunctional monometallic nanohybrids for reactive oxygen species-mediated cell apoptosis and enhanced fluorescence cell imaging

Novel fluorescent monometallic Ag nanohybrids (Ag NHs) have been synthesized via polycytosine-mediated biomineralization on Ag nanoparticles (Ag NPs). Thiolated polycytosine dC₁₂ was anchored on the Ag NPs, followed by dC₁₂-templated synthesis of the Ag nanoclusters (Ag NCs). The Ag NHs exhibited strong fluorescence emission and improved resistance to dissolved oxygen in solution as compared to the Ag NCs. As an efficient therapeutic agent, the delivery of aptamer-functionalized Ag NHs into target cells induced reactive oxygen species (ROS) generation and cell apoptosis. The ROS-mediated apoptotic effect of the Ag NHs was stronger than that of the Ag NCs. For cell imaging, the target cells treated with aptamer-functionalized Ag NHs exhibited a higher fluorescence brightness than those treated with Ag NCs. Due to the fluorescence quenching of Ag NHs by the intracellularly generated ROS, the Ag NHs served as a fluorescent indicator for real-time monitoring of ROS-mediated cell apoptosis. The In vivo antitumor efficacy of the Ag NHs was also evaluated.

Bivalent Aptasensor Based on Silver-Enhanced Fluorescence Polarization for Rapid Detection of Lactoferrin in Milk

Here we report a novel type of bivalent aptasensor based on silver-enhanced fluorescence polarization (FP) for detection of lactoferrin (Lac) in milk powder with high sensitivity and specificity. The novel two split aptamers were obtained from the aptamer reported in our previous SELEX (systematic evolution of ligands by exponential enrichment) selection, and their minimal structural units were optimized on the basis of their affinity and specificity. Also, dual binding sites of split aptamers were verified. The bivalent aptamers were modified to be linked with signal-molecule fluorescein isothiocyanate (FITC) and enhancer silver decahedral nanoparticles (Ag₁₀NPs). The split aptamers could bind to different sites of Lac and assemble into a split-aptamers-target complex, narrowing the distance between Ag₁₀NPs and FITC dye. As a result, Ag₁₀NPs could produce a mass-augmented and metal-enhanced fluorescence (MEF) effect. In general, ternary amplification based on Ag₁₀NPs, split aptamers, and the MEF effect all contributed to the significant increase of FP values. It was proved that the sensitivity of this assay was about 3 orders of magnitude over traditional aptamer-based homogeneous assays with a detection limit of 1.25 pM. Furthermore, this design was examined by actual milk powder with rapid and high-throughout detection.

Recent progresses in biomedical applications of aptamer-functionalized systems

Aptamers, known as "chemical antibodies" are screened via a combinational technology of systematic evolution of ligands by exponential enrichment (SELEX). Due to their specific targeting ability, high binding affinity, low immunogenicity and easy modification, aptamer-functionalized systems have been extensively applied in various fields and exhibit favorable results. However, there is still a long way for them to be commercialized, and few aptamer-functionalized systems have yet successfully entered clinical and industrial use. Thus, it is necessary to overview the recent research progresses of aptamer-functionalized systems for the researchers to improve or design novel and better aptamer-functionalized systems. In this review, we first introduce the recent progresses of aptamer-functionalized systems' applications in biosensing, targeted drug delivery, gene therapy and cancer cell imaging, followed by a discussion of the challenges faced with extensive applications of aptamer-functionalized systems and speculation of the future prospects of them.

Characterization of the specific interaction between the DNA aptamer sgc8c and protein tyrosine kinase-7 receptors at the surface of T-cells by biosensing AFM

We studied the interaction of the specific DNA aptamer sgc8c immobilized at the AFM tip with its corresponding receptor, the protein tyrosine kinase-7 (PTK7) embedded in the membrane of acute lymphoblastic leukemia (ALL) cells (Jurkat T-cells). Performing single molecule force spectroscopy (SMFS) experiments, we showed that the aptamer sgc8c bound with high probability (38.3 ± 7.48%) and high specificity to PTK7, as demonstrated by receptor blocking experiments and through comparison with the binding behavior of a nonspecific aptamer. The determined kinetic off-rate (k_off = 5.16 s⁻¹) indicates low dissociation of the sgc8c–PTK7 complex. In addition to the pulling force experiments, simultaneous topography and recognition imaging (TREC) experiments using AFM tips functionalized with sgc8c aptamers were realized on the outer regions surface of surface-immobilized Jurkat cells for the first time. This allowed determination of the distribution of PTK7 without any labeling and at near physiological conditions. As a result, we could show a homogeneous distribution of PTK7 molecules on the outer regions of ALL cells with a surface density of 325 ± 12 PTK7 receptors (or small receptor clusters) per μm².

Graphical Abstract

Aptamer-functionalized nano/micro-materials for clinical diagnosis: isolation, release and bioanalysis of circulating tumor cells

Detection of rare circulating tumor cells (CTCs) in peripheral blood is a challenging, but necessary, task in order to diagnose early onset of metastatic cancer and to monitor treatment efficacy. Over the last decade, step-up produced aptamers have attracted great attention in clinical diagnosis. They have offered great promise for a broader range of cell-specific recognition and isolation. In particular, aptamer-functionalized magnetic particles for selective extraction of target CTCs have shown reduced damage to cells and relatively simple operation. Also, efforts to develop aptamer-functionalized microchannel/microstructures able to efficiently isolate target CTCs are continuing, and these efforts have brought more advanced geometrically designed substrates. Various aptamer-mediated cell release techniques are being developed to enable subsequent biological studies. This article reviews some of these advances in aptamer-functionalized nano/micro-materials for CTCs isolation and methods for releasing captured CTCs from aptamer-functionalized surfaces. Biological studies of CTCs after release are also discussed.

A multifunctional silver nanocomposite for the apoptosis of cancer cells and intracellular imaging

A multifunctional silver nanoparticle based nanocomposite for specific cancer cell therapy andin situimaging.

Multivalent Aptamers: Versatile Tools for Diagnostic and Therapeutic Applications

Nucleic acid aptamers generated through an in vitro selection are currently extensively applied as very valuable biomolecular tools thanks to their prominent advantages. Diversity of spatial structures, ease of production through chemical synthesis and a large variety of chemical modifications make aptamers convenient building blocks for the generation of multifunctional constructs. An opportunity to combine different aptamer functionalities with other molecules of interest such as reporter groups, nanoparticles, chemotherapeutic agents, siRNA or antisense oligonucleotides provides a widest range of applications of multivalent aptamers. The present review summarizes approaches to the design of multivalent aptamers, various examples of multifunctional constructs and the prospects of employing them as components of biosensors, probes for affinity capture, tools for cell research and potential therapeutic candidates.

Highly sensitive detection of leukemia cells based on aptamer and quantum dots

Detection of leukemia at the early stage with high sensitivity is a significant clinical challenge for clinicians. In the present study, we developed a sensitive detector consisting of the product of oligonucleotides hybridized with semiconductor quantum dots (QDs) to generate a stronger fluorescent signal so that leukemic cells can be captured. In the present study, a biotin-modified Sgc8 aptamer was used to identify CCRF-CEM cells, and then biotin-appended QDs were labeled with the aptamer via streptavidin and biotin amplification interactions. We described the complex as QDs-bsb-apt. CEM and Ramos cells were used to assess the specificity and sensitivity of the novel complex. These results revealed that the complex could be more effective in diagnosing leukemia at the early stage. In conclusion, an innovative structure based on aptamer and QDs for leukemia diagnosis was provided. It has the potential to image tumor cells in vitro or in vivo and to realize the early diagnosis of disease. Furthermore, it may be used to provide guidance for clinicians to implement individualized patient therapy.

A multifunctional core–shell nanoplatform for enhanced cancer cell apoptosis and targeted chemotherapy

A novel multifunctional nanoplatform was designed based on the combination of silver nanoparticles (AgNPs) with nucleolin-targeted and doxorubicin (Dox)-loaded manganese dioxide (MnO₂) nanosheets to induce enhanced cancer cell apoptosis and targeted chemotherapy.

Microfluidic chip-based silver nanoparticles aptasensor for colorimetric detection of thrombin

In this paper, a colorimetric silver nanoparticles aptasensor (aptamer-AgNPs) was developed for simple and straightforward detection of protein in microfluidic chip. Surface-functionalized microfluidic channels were employed as the capture platform. Then the mixture of target protein and aptamer-AgNPs were injected into the microfluidic channels for colorimetric detection. To demonstrate the performance of this detection platform, thrombin was chosen as a model target protein. Introduction of thrombin could form a sandwich-type complex involving immobilized AgNPs. The amount of aptamer-AgNPs on the complex augmented along with the increase of the thrombin concentration causing different color change that can be analyzed both by naked eyes and a flatbed scanner. This method is featured with low sample consumption, simple processes of microfluidic platform and straightforward colorimetric detection with aptamer-AgNPs. Thrombin at concentrations as low as 20pM can be detected using this aptasensor without signal amplification. This work demonstrated that it had good selectivity over other proteins and it could be a useful strategy to detect other targets with two affinity binding sites for ligands as well.

A Highlight of Recent Advances in Aptamer Technology and Its Application

Aptamers and SELEX (systematic evolution of ligands by exponential enrichment) technology have gained increasing attention over the past 25 years. Despite their functional similarity to protein antibodies, oligonucleotide aptamers have many unique properties that are suitable for clinical applications and industrialization. Aptamers may be superior to antibodies in fields such as biomarker discovery, in vitro and in vivo diagnosis, precisely controlled drug release, and targeted therapy. However, aptamer commercialization has not occurred as quickly as expected, and few aptamer-based products have yet successfully entered clinical and industrial use. Thus, it is important to critically review some technical barriers of aptamer and SELEX technology per se that may impede aptamer development and application. To date, how to rapidly obtain aptamers with superior bioavailability over antibodies remains the key issue. In this review, we discuss different chemical and structural modification strategies aimed to enhance aptamer bioavailability. We also discuss improvements to SELEX process steps to shorten the selection period and improve the SELEX process success rate. Applications in which aptamers are particularly suited and perform differently or superior to antibodies are briefly introduced.