The potential of aptamers for cancer research

Functionalized liposomes for targeted breast cancer drug delivery

Despite the exceptional progress in breast cancer pathogenesis, prognosis, diagnosis, and treatment strategies, it remains a prominent cause of female mortality worldwide. Additionally, although chemotherapies are effective, they are associated with critical limitations, most notably their lack of specificity resulting in systemic toxicity and the eventual development of multi-drug resistance (MDR) cancer cells. Liposomes have proven to be an invaluable drug delivery system but of the multitudes of liposomal systems developed every year only a few have been approved for clinical use, none of which employ active targeting. In this review, we summarize the most recent strategies in development for actively targeted liposomal drug delivery systems for surface, transmembrane and internal cell receptors, enzymes, direct cell targeting and dual-targeting of breast cancer and breast cancer-associated cells, e.g., cancer stem cells, cells associated with the tumor microenvironment, etc.

Single-Cell Analysis in Immuno-Oncology

The complexity of the cellular and non-cellular milieu surrounding human tumors plays a decisive role in the course and outcome of disease. The high variability in the distribution of the immune and non-immune compartments within the tumor microenvironments (TME) among different patients governs the mode of their response or resistance to current immunotherapeutic approaches. Through deciphering this diversity, one can tailor patients' management to meet an individual's needs. Single-cell (sc) omics technologies have given a great boost towards this direction. This review gathers recent data about how multi-omics profiling, including the utilization of single-cell RNA sequencing (scRNA-seq), assay for transposase-accessible chromatin with sequencing (scATAC-seq), T-cell receptor sequencing (scTCR-seq), mass, tissue-based, or microfluidics cytometry, and related bioinformatics tools, contributes to the high-throughput assessment of a large number of analytes at single-cell resolution. Unravelling the exact TCR clonotype of the infiltrating T cells or pinpointing the classical or novel immune checkpoints across various cell subsets of the TME provide a boost to our comprehension of adaptive immune responses, their antigen specificity and dynamics, and grant suggestions for possible therapeutic targets. Future steps are expected to merge high-dimensional data with tissue localization data, which can serve the investigation of novel multi-modal biomarkers for the selection and/or monitoring of the optimal treatment from the current anti-cancer immunotherapeutic armamentarium.

Aptamer-based NanoBioSensors for seafood safety

Chemical and biological contaminants are of primary concern in ensuring seafood safety. Rapid detection of such contaminants is needed to keep us safe from being affected. For over three decades, immunoassay (IA) technology has been used for the detection of contaminants in seafood products. However, limitations inherent to antibody generation against small molecular targets that cannot elicit an immune response, along with the instability of antibodies under ambient conditions greatly limit their wider application for developing robust detection and monitoring tools, particularly for non-biomedical applications. As an alternative, aptamer-based biosensors (aptasensors) have emerged as a powerful yet robust analytical tool for the detection of a wide range of analytes. Due to the high specificity of aptamers in recognising targets ranging from small molecules to large proteins and even whole cells, these have been suggested to be viable molecular recognition elements (MREs) in the development of new diagnostic and biosensing tools for detecting a wide range of contaminants including heavy metals, antibiotics, pesticides, pathogens and biotoxins. In this review, we discuss the recent progress made in the field of aptasensors for detection of contaminants in seafood products with a view of effectively managing their potential human health hazards. A critical outlook is also provided to facilitate translation of aptasensors from academic laboratories to the mainstream seafood industry and consumer applications.

Aptasensor for Impedimetric Detection of Lysozyme

The impedimetric detection of a protein, lysozyme (LYS), was carried out herein by aptamer-immobilized single-use pencil graphite electrodes (PGEs). The aptamer was immobilized onto electrochemically activated surface of electrode without using any chemical agents, or any types of nanomaterials. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were applied to analyze the electrochemical behavior of unmodified PGE and aptamer immobilized PGE. The interaction of aptamer with its target protein, LYS, was then investigated by EIS. The limit of detection for LYS was found to be 1.44 μg/mL (equals to 100.65 nM). The developed aptasensor specific to LYS presented high selectivity against to bovine serum albumin and thrombin.

A review of spatial profiling technologies for characterizing the tumor microenvironment in immuno-oncology

Interpreting the mechanisms and principles that govern gene activity and how these genes work according to -their cellular distribution in organisms has profound implications for cancer research. The latest technological advancements, such as imaging-based approaches and next-generation single-cell sequencing technologies, have established a platform for spatial transcriptomics to systematically quantify the expression of all or most genes in the entire tumor microenvironment and explore an array of disease milieus, particularly in tumors. Spatial profiling technologies permit the study of transcriptional activity at the spatial or single-cell level. This multidimensional classification of the transcriptomic and proteomic signatures of tumors, especially the associated immune and stromal cells, facilitates evaluation of tumor heterogeneity, details of the evolutionary trajectory of each tumor, and multifaceted interactions between each tumor cell and its microenvironment. Therefore, spatial profiling technologies may provide abundant and high-resolution information required for the description of clinical-related features in immuno-oncology. From this perspective, the present review will highlight the importance of spatial transcriptomic and spatial proteomics analysis along with the joint use of other sequencing technologies and their implications in cancers and immune-oncology. In the near future, advances in spatial profiling technologies will undoubtedly expand our understanding of tumor biology and highlight possible precision therapeutic targets for cancer patients.

Determination of Drugs in Clinical Trials: Current Status and Outlook

All pharmaceutical drugs, vaccines, cosmetic products, and many medical breakthroughs must first be approved through clinical research and trials before advancing to standard practice or entering the marketplace. Clinical trials are sets of tests that are required to determine the safety and efficacy of pharmaceutical compounds, drugs, and treatments. There is one pre-phase and four main clinical phase requirements that every drug must pass to obtain final approval. Analytical techniques play a unique role in clinical trials for measuring the concentrations of pharmaceutical compounds in biological matrices and monitoring the conditions of patients (or volunteers) during various clinical phases. This review focuses on recent analytical methods that are employed to determine the concentrations of drugs and medications in biological matrices, including whole blood, plasma, urine, and breast milk. Four primary analytical techniques (extraction, spectroscopy, chromatography, and electrochemical) are discussed, and their advantages and limitations are assessed. Subsequent to a survey of evidence and results, it is clear that microelectromechanical system (MEMS) based electrochemical sensor and biosensor technologies exhibit several notable advantages over other analytical methods, and their future prospects are discussed.

Multifunctional nanoparticles as optical biosensing probe for breast cancer detection: A review

Optical biosensors show attractive performance in medical sensing in the event of using different nanoparticles in their design. Owing to their unique optical characteristics and biological compatibility, gold nanoparticles (GNPs), silver nanoparticles (AgNPs), bimetallic nanoparticles and magnetic nanoparticles have been broadly implemented in making sensing tools. The functionalization of these nanoparticles with different components provides an excellent opportunity to assemble selective and sensitive sensing materials to detect various biological molecules related to breast cancer. This review summarizes the recent application of optical biosensing devices based on nanomaterials and discusses their pros and cons to improve breast cancer detection in real samples. In particular, the main constituent elements of these optical biosensors including recognition and transducer elements, types of applied nanostructures, analytical sensing procedures, sensor detection ranges and limit of detection (LOD), are expressed in detail.

Inhibition of cell migration and invasion by ICAM-1 binding DNA aptamers

Cancer is the second leading cause of death worldwide and most of the cancer-related deaths result from metastasis. As expressed on the surface of various cancer cell types, intercellular adhesion molecule-1 (ICAM-1) has been shown to play a role in the attachment, invasion and migration of tumor cells. In this study, DNA aptamers were generated against ICAM-1 by cell-SELEX and protein SELEX method using ICAM-1⁽⁺⁾ CHO-ICAM-1 cells and ICAM-1 protein, respectively. The pools obtained at the end of the 10th round of both SELEX were sequenced and the most enriched sequences were characterized for their binding behaviors and affinities to ICAM-1⁽⁺⁾ CHO-ICAM-1 and ICAM-1^(-) MIA PaCa-2 cells. Moreover, the inhibition abilities of sequences on migration and invasion were measured. The seven aptamer sequences were obtained selectively binding to CHO-ICAM-1 cells with K_d values in the ranging from 13.8 to 47.1 nM. Four of these aptamers showed inhibition in both migration and invasion of CHO-ICAM-1 cells at least 61%. All these results suggested that these aptamers have potential to detect specifically ICAM-1 expressing tumor cells and inhibit migration and invasion by blocking ICAM-1 related interactions of circulating tumor cells.

Targeted delivery and controlled release of doxorubicin to cancer cells by smart ATP-responsive Y-shaped DNA structure-capped mesoporous silica nanoparticles

In this study, a dual-receptor doxorubicin-targeted delivery system based on mesoporous silica nanoparticles (MSNs) modified with mucine-1 and ATP aptamers (DOX@MSNs-Apts) was developed. An amine-modified mucine-1 (MUC1) aptamer was covalently anchored on the surface of carboxyl-functionalized MSNs. Then, ATP aptamers (ATP1 and ATP2 aptamers) were immobilized on the surface of MSNs through partial hybridization with the MUC1 aptamer by forming a Y-shaped DNA structure on the MSNs surface (DOX@MSNs-Apts) as a gatekeeper. The developed DOX@MSNs-Apts exhibited high DOX loading capacity. In addition, it indicated an ATP-responsive feature, leading to the release of DOX in the environment with high ATP concentration (10 mM), similar to the intracellular environment of tumor cells. This property demonstrated that anticancer drug (DOX) could be entrapped inside the nanocarrier with nearly no leakage in blood and a very low concentration of ATP (1 μM). It was found that after the internalization of DOX@MSNs-MUC1 by cancer cells via the MUC1 receptor-mediated endocytosis, the ATP aptamers left the surface of the nanocarrier, allowing for rapid DOX release. DOX@MSNs-Apts indicated higher cellular uptake in MCF-7 and C26 cancer cells (MUC1+), rather than CHO cells (MUC1-). The in vitro cytotoxicity and the in vivo antitumor efficacy of DOX@MSNs-Apts showed greater cytotoxicity than the nanoparticles decorated with scrambled ATP aptamers (DOX@MSNs-Apts scrambled) in C26 and MCF-7 cell lines (MUC1+). The biodistribution and in vivo anticancer efficacy on the C26 tumor bearing mice indicated that the DOX@MSNs-Apts had a higher tumor accumulation and superior tumor growth inhibitory effect compared to free DOX and their scrambled aptamers, DOX@MSNs-Apts scrambled. Overall, the obtained results indicated that the prepared smart platform could reveal new insights into the treatment of cancer.

Applying high-dimensional single-cell technologies to the analysis of cancer immunotherapy

Advances in molecular biology, microfluidics and bioinformatics have empowered the study of thousands or even millions of individual cells from malignant tumours at the single-cell level of resolution. This high-dimensional, multi-faceted characterization of the genomic, transcriptomic, epigenomic and proteomic features of the tumour and/or the associated immune and stromal cells enables the dissection of tumour heterogeneity, the complex interactions between tumour cells and their microenvironment, and the details of the evolutionary trajectory of each tumour. Single-cell transcriptomics, the ability to track individual T cell clones through paired sequencing of the T cell receptor genes and high-dimensional single-cell spatial analysis are all areas of particular relevance to immuno-oncology. Multidimensional biomarker signatures will increasingly be crucial to guiding clinical decision-making in each patient with cancer. High-dimensional single-cell technologies are likely to provide the resolution and richness of data required to generate such clinically relevant signatures in immuno-oncology. In this Perspective, we describe advances made using transformative single-cell analysis technologies, especially in relation to clinical response and resistance to immunotherapy, and discuss the growing utility of single-cell approaches for answering important research questions.

Target-triggered "signal-off" electrochemical aptasensor assisted by Au nanoparticle-modified sensing platform for high-sensitivity determination of circulating tumor cells

In this study, we fabricated a high-sensitivity "signal-off" electrochemical aptasensing platform for quantifying circulating tumor cells (CTCs) based on target-triggered signal readout of methylene blue (MB). Au nanoparticles (AuNPs) were introduced to enlarge the specific surface area of the gold electrode (GE), which would immobilize homogeneous and more MB-aptamers. MB-modified and stem-loop-like aptamers were assigned as a recognition element with K562 cells. Thiolated complementary strands hybridized with MB-aptamers to form double-stranded DNA (dsDNA) conformation which were further self-assembled on the surface of AuNP-modified GE, leading to a marked current peak of MB signal. In the presence of K562 cells, the MB-aptamers preferred to recognize and bind with the cells, causing the disassembly of MB-aptamers from the GE surface. Therefore, the reduced value of MB signal was related to the number of K562 cells. With the proposed aptasensor, a dynamic linear range from 1 × 10² to 1 × 10⁶ cells mL^-1 was obtained with a detection limit of 23 cells mL^-1. Moreover, the aptasensor showed good selectivity, stability, and reproducibility as well as potential use in the clinical setting. Meanwhile, characterization techniques such as field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were performed to analyze the evolution of the morphology and each fabricated step of the constructed aptasensor. Our proposed aptasensor could be designed as a universal platform for CTC determination by replacing tumor cell-specific aptamers, which is a promising strategy for basic research and clinical applications. Graphical abstract.

Nanotechnology approaches in the current therapy of skin cancer

Skin cancer is a high burden disease with a high impact on global health. Conventional therapies have several drawbacks; thus, the development of effective therapies is required. In this context, nanotechnology approaches are an attractive strategy for cancer therapy because they enable the efficient delivery of drugs and other bioactive molecules to target tissues with low toxic effects. In this review, nanotechnological tools for skin cancer will be summarized and discussed. First, pathology and conventional therapies will be presented, followed by the challenges of skin cancer therapy. Then, the main features of developing efficient nanosystems will be discussed, and next, the most commonly used nanoparticles (NPs) described in the literature for skin cancer therapy will be presented. Subsequently, the use of NPs to deliver chemotherapeutics, immune and vaccine molecules and nucleic acids will be reviewed and discussed as will the combination of physical methods and NPs. Finally, multifunctional delivery systems to codeliver anticancer therapeutic agents containing or not surface functionalization will be summarized.

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.

Live and Let Dye: Visualizing the Cellular Compartments of the Malaria Parasite Plasmodium falciparum

Malaria remains one of the deadliest diseases worldwide and it is caused by the protozoan parasite Plasmodium spp. Parasite visualization is an important tool for the correct detection of malarial cases but also to understand its biology. Advances in visualization techniques promote new insights into the complex life cycle and biology of Plasmodium parasites. Live cell imaging by fluorescence microscopy or flow cytometry are the foundation of the visualization technique for malaria research. In this review, we present an overview of possibilities in live cell imaging of the malaria parasite. We discuss some of the state-of-the-art techniques to visualize organelles and processes of the parasite and discuss limitation and advantages of each technique. © 2019 International Society for Advancement of Cytometry.

Redox-Sensitive Gelatin/Silica-Aptamer Nanogels for Targeted siRNA Delivery

RNA interference (RNAi) has potential advantages over other gene therapy approaches due to its high specificity and the ability to inhibit target gene expression. However, the stability and tissue-specific delivery of siRNA remain as the biggest obstacles for RNAi therapeutics. Here, we developed such a system by conjugating gelatin-based nanogels with the nucleolin-targeted AS1411 aptamer and deoxynucleotide-substituted siRNA together (Apt-GS/siRNA) via a disulfide linker to achieve transient docking of siRNA. These Apt-GS/siRNA nanogels demonstrated favorable release of siRNA under reducing conditions owing to disulfide cleavage. Furthermore, this smart system could electively release siRNA into the cytosol in nucleolin-positive cells (A549) by a glutathione-triggered disassembly and subsequently efficient RNAi for luciferase. Besides, disulfide-equipped Apt-GS nanogels showed good biocompatibility in vitro. Taken together, this redox-responsive, tumor-targeting smart nanogels display great potential in exploiting functionalized siRNA delivery and tumor therapy.

In vitro selection of aptamer S1 against MCF-7 human breast cancer cells

Breast cancer is the most common female cancer. However, the known effective specific biomarkers for breast cancer are still scarce. Abnormal membrane proteins serve as ideal biomarkers for disease diagnoses, therapeutics and prognosis. Thus aptamers (single-stranded oligonucleotide molecules) with molecular recognition properties can be used as efficient tools to sort cells based on differences in cell surface architecture between normal and tumor cells. In this study, we aimed to screen specific aptamer against MCF-7 human breast cancer cells. Cell-SELEX process was performed to isolate aptamers from a combinatorial single-stranded nucleic acid library that selectively targeting surface proteins of MCF-7 cells in contrast with MCF-10A human mammary epithelial cells. The process was repeated until the pool was enriched for sequences that specifically recognizing MCF-7 cells in monitoring by flow cytometry. Subsequently, the enriched pool was cloned into bacteria, and positive clones were sequenced to obtain individual sequences. Representative sequences were chemically synthesized and evaluated their binding affinities to MCF-7 cells. As a result, an aptamer S1 was finally identified to have high binding affinity with equilibrium dissociation constant (K_d) value of 29.9 ± 6.0 nM. FAM-labeled aptamer S1 induced fluorescence shift in MCF-7 cells but not in MCF-10A human mammary epithelial cells, or MDA-MB-453 and MDA-MB-231 human breast cancer cells. Furthermore, result of cell imaging observed from laser confocal fluorescence microscope showed that MCF-7 cells exhibited stronger fluorescence signal resulted from Cy5-labeled aptamer S1 than MCF-10A cells. The above findings suggested that S1 may be a specificity and selectivity aptamer for MCF-7 cells and useful for the breast cancer detection and diagnosis.

Recognition of Helicobacter pylori by protein-targeting aptamers

BACKGROUND

Helicobacter pylori (H pylori) is a disease-causing pathogen capable of surviving under acidic conditions of the human stomach. Almost half of the world's population is infected with H pylori, with gastric cancer being the most unsatisfactory prognosis. Although H pylori has been discovered 30 years ago, the effective treatment and elimination of H pylori continue to be problematic.

MATERIALS AND METHODS

In our study, we screened nucleic acid aptamers using H pylori surface recombinant antigens as targets. Trypsin was used for separating aptamers that were bound to proteins. Following nine rounds of screening, we performed sequence similarity analyses to assess whether the aptamers can recognize the target protein. Two sequences with desirable recognition ability were selected for affinity detection. Aptamer Hp4 with the strongest binding ability to the H pylori surface recombinant antigen was chosen. After optimization of the binding conditions, we conducted specificity tests for Hp4 using Escherichia coli, Staphylococcus aureus, Vibrioanguillarum, and H pylori.

RESULTS

The data indicated that the aptamer Hp4 had an equilibrium dissociation constant (K_d ) of 26.48 ± 5.72 nmol/L to the target protein. This aptamer was capable of exclusively detecting H pylori cells, without displaying any specificity for other bacteria.

CONCLUSIONS

We obtained a high-affinity aptamer for H pylori, which is expected to serve as a new molecular probe for detection of H pylori.

A dual-functional HER2 aptamer-conjugated, pH-activated mesoporous silica nanocarrier-based drug delivery system provides in vitro synergistic cytotoxicity in HER2-positive breast cancer cells

Purpose: As well as functioning as a ligand that is selectively internalized by cells overexpressing human epidermal growth factor receptor-2 (HER2), HApt can exert cytotoxic effects by inducing cross-linking and subsequent translocation of HER2 to cytoplasmic vesicles, such downregulation of HER2 inhibits cell proliferation and induces apoptosis. We aimed to exploit the potential of HApt as both a targeting agent and antagonist to maximize the efficacy of mesoporous silica nanoparticle (MSN)-based drug release systems for HER2-positive breast cancer. Materials and methods: We fabricated novel HApt aptamer-functionalized pH-sensitive β-cyclodextrin (β-CD)-capped doxorubicin (DOX)-loaded mesoporous silica nanoparticles (termed MSN-BM/CD-HApt@DOX) for targeted delivery and selective targeting of HER2-positive cells. MSN-functionalized benzimidazole (MSN-BM) was used to load and achieve pH stimuli-responsive release of the chemotherapeutic agent doxorubicin (DOX). β-cyclodextrin was introduced as a gatekeeper for encapsulated DOX and HApt as a selective HER2-targeting moiety and biotherapeutic agent. Results: Physical and chemical characterizations (FT-IR, XRD, TEM and BET) confirmed successful construction of MSN-BM/CD-HApt@DOX nanoparticles. In vitro release assays verified pH-sensitive DOX release. MSN-BM/CD-HApt@DOX (relative DOX concentration, 3.6 μg/mL) underwent HER2-mediated endocytosis and was more cytotoxic to HER2-positive SKBR3 cells than HER2-negative MCF7 cells. MSN-BM/CD-HApt@DOX also exhibited better uptake and stronger growth inhibition in SKBR3 cells than the control MSN-BM/CD-NCApt@DOX functionalized with a scrambled nucleotide sequence on CD. Overall, intracellular delivery of DOX and the biotherapeutic agent HApt resulted in synergistic cytotoxic effects in HER2-positive cancer cells in comparison to either DOX or HApt alone. Conclusion: MSN-BM/CD-HApt@DOX enables HER2-mediated targeting and biotherapeutic effects as well as pH-responsive DOX drug release, resulting in synergistic cytotoxic effects in HER2-overexpressing cells in vitro. This novel nanocarrier could potentially enable specific targeting to improve the efficacy of chemotherapy for HER2-positive cancer.

Electrochemical aptamer-based microsensor for real-time monitoring of adenosine in vivo

In this work, an implantable and minimally invasive micro-aptasensor for adenosine monitoring in vivo, based on flexible integrated electrodes, was developed. Firstly the sensor was made by the modification of a needle-type electrode with reduced graphene oxide and gold nanoclusters (rGO-AuNCs) using two-step electrodeposition. Secondly Sulfhydryl-terminated capture probe (ssDNA1) was immobilized on rGO-AuNCs modified electrode surface by self-assembly, and then it was hybridized with adenosine aptamer (ssDNA2). Lastly methylene blue (MB) as an electrochemical indicator was adsorbed on the aptamer through specific interaction of MB with guanine base. The peak current of MB decreased linearly with increasing adenosine concentration due to the formation of aptamer-adenosine complex and displacement of the aptamer from the modified electrode surface. The sensor showed a low detection limit of 0.1 nM with signal-to-noise ratio equal to 3 as well as a wide linear response range (0.1 nM-1 mM) in vitro. Also, a high selectivity was demonstrated for adenosine in relation to uridine, guanosine, and cytidine. Experiments in vivo demonstrated fast responses for a range of adenosine concentrations. This work demonstrates a promising path for implantable devices for the determination of biomolecules in vivo, thus allowing for health tests, detection of infectious diseases, and other medical conditions.

Label free aptasensor for ultrasensitive detection of tobramycin residue in pasteurized cow's milk based on resonance scattering spectra and nanogold catalytic amplification

TOB aptamer can be adsorbed on the AuNPs surface to form AuNPs-aptamer complexation to prevent AuNPs aggregation in high salt solution. When TOB was added to the AuNPs solution, the aptamer would bind with TOB and depart from the AuNPs surface. The amount of the AuNPs-aptamer complexation depends on the TOB concentration. Different concentration of AuNPs-aptamer can catalyze the reduction reaction of CuSO₄ to produce different size Cu₂O particle. The resonance scattering peak intensities are correlated with the Cu₂O size. Large size Cu₂O particle as a resonance scattering spectroscopy probe can remarkable improve the TOB detection sensitivity. We have succeeded to detect the trace TOB in aqueous solutions. The linear range and limit of detection were 0.50-17 nM and 0.19 nM, respectively. This simple and inexpensive method exhibited high sensitivity and selectivity, which was successfully used to detect TOB in milk. The results indicated the accuracy and precision were satisfied.

Exosomes, new biomarkers in early cancer detection

Exosomes are endosomal-derived vesicles, playing a major role in cell-to-cell communication. Multiple cells secret these vesicles to induce and inhibit different cellular and molecular pathways. Cancer-derived exosomes have been shown to affect development of cancer in different stages and contribute to the recruitment and reprogramming of both proximal and distal tissues. The growing interest in defining the clinical relevance of these nano-sized particles in cancers, has led to the identification of either tissue- or disease-specific exosomal contents, such as nucleic acids, proteins and lipids as a source of new biomarkers which propose the diagnostic potentials of exosomes in early detection of cancers. In this review, we have discussed some aspects of exosomes including their contents, applications and isolation techniques in the field of early cancer detection. Although, exosomes are considered as ideal biomarkers in cancer diagnosis, due to their unique characteristics, there is still a long way in the development of exosome-based assays.

Aptamers: an emerging class of bioaffinity ligands in bioactive peptide applications

The food and health applications of bioactive peptides have grown remarkably in the past few decades. Current elucidations have shown that bioactive peptides have unique structural arrangement of amino acids, conferring distinct functionalities, and molecular affinity characteristics. However, whereas interest in the biological potency of bioactive peptides has grown, cost-effective techniques for monitoring the structural changes in these peptides and how these changes affect the biological properties have not grown at the same rate. Due to the high binding affinity of aptamers for other biomolecules, they have a huge potential for use in tracking the structural, conformational, and compositional changes in bioactive peptides. This review provides an overview of bioactive peptides and their essential structure-activity relationship. The review further highlights on the types and methods of synthesis of aptamers before the discussion of the prospects, merits, and challenges in the use of aptamers for bioaffinity interactions with bioactive peptides.

Molecular Application of Aptamers in the Diagnosis and Treatment of Cancer and Communicable Diseases

Cancer and infectious diseases such as Ebola, HIV, tuberculosis, Zika, hepatitis, measles and human schistosomiasis are serious global health hazards. The increasing annual morbidities and mortalities of these diseases have been blamed on drug resistance and the inefficacy of available diagnostic tools, particularly those which are immunologically-based. Antibody-based tools rely solely on antibody production for diagnosis and for this reason they are the major cause of diagnostic delays. Unfortunately, the control of these diseases depends on early detection and administration of effective treatment therefore any diagnostic delay is a huge challenge to curbing these diseases. Hence, there is a need for alternative diagnostic tools, discovery and development of novel therapeutic agents. Studies have demonstrated that aptamers could potentially offer one of the best solutions to these problems. Aptamers are short sequences of either DNA or RNA molecules, which are identified in vitro through a SELEX process. They are sensitive and bind specifically to target molecules. Their promising features suggest they may serve as better diagnostic agents and can be used as drug carriers for therapeutic purposes. In this article, we review the applications of aptamers in the theranostics of cancer and some infectious diseases.

Trypsin enhances aptamer screening: A novel method for targeting proteins

A novel screening method for protein aptamer selection was developed in this study. Aptamers with high affinity and specificity to the surface recombinant antigen of Helicobacter pylori (HP-Ag) and to tumor markers carcinoembryonic antigen (CEA), cancer antigen 125 (CA125) and cancer antigen 19-9(CA19-9) were screened using trypsin enhanced screening method. Briefly, the target proteins above were immobilized onto 96-well polystyrene plates and incubated with a single-stranded DNA (ssDNA) library for aptamer selection. Then, trypsin was introduced to digest the proteins and obtain ssDNA that bound to the target proteins with high specificity. The concentration of ssDNA that shed from protein-ssDNA complexes was detected. After sequencing, the enrichment of target-specific aptamers was monitored and the affinity of each aptamer was analyzed. Urea, which has been reported in other article, was used to compare with trypsin. The results revealed that trypsin was more effective than urea for protein aptamer selection. The protocol used in this study provided a novel method for generating aptamers.

Ultrasensitive and label-free electrochemical aptasensor of kanamycin coupling with hybridization chain reaction and strand-displacement amplification

This work reports the proof-of-concept of an ultrasensitive label-free electrochemical aptasensor for Kanamycin (Kana) detection coupling strand-displacement amplification (SDA) with hybridization chain reaction (HCR). In the presence of target Kana, the analyte triggers conformational change of hairpin HP1 (HP1) and two-staged SDA to produce short single-stranded DNA (S1) with the aid of KF polymerase and nicking endonuclease. Meanwhile, the as-produced S1 hybridizes with the immobilized hairpin HP2 (HP2) on the electrode to open the hairpin, thereby resulting in the formation of DNA duplex. Thereafter, DNA duplex is selectively digested by Exo III accompanying S1 recycling. The residual single-stranded probe (S2) on the electrode opens another two hairpins in sequence and propagates a chain reaction of hybridization events between two alternating hairpins (H1 and H2) to form a long nicked double-helix. Upon addition of redox-active methylene blue (MB), numerous indicators are intercalated into the grooves of double-helix DNA polymers, each of which produces an electrochemical signal within the applied potentials. Under optimum conditions, the SDA/HCR-based electrochemical aptasensor exhibits a high sensitivity for detection of Kana down to 36 fM with a linear range from 0.05 to 200 pM. Additionally, the as-prepared aptasensor is successfully employed to determinate the Kana in animal derived food (milk). With the advantages of high sensitivity, label-free strategy and excellent selectivity, the developed aptasensor possesses great potential application value in food-safety analysis field.