Oligonucleotide aptamers: Recent advances in their screening, molecular conformation and therapeutic applications

Nanomaterial-modified electrochemical aptasensors for tetracycline detection: a review

Excessive residues of tetracyclines in the livestock, food products and environment can lead to their accumulation in the human body through the food chain, unavoidably posing a threat to the human health. Therefore, it is essential to establish detection methods with high specificity, stability, and sensitivity. Among the numerous detecting techniques, electrochemical sensors with aptamers working as biorecognition elements have been increasingly applied to monitor tetracyclines. Notably, the synergy of a wide range of nanomaterials with aptamer-based sensors has improved the charge transfer efficiency and signal sensitivity. In this review, the advantages of aptamer-based recognition methods are discussed, and the measuring processes of electrochemical detection are introduced. Then, advances in electrochemical aptasensors used for detecting tetracyclines are summarized with an emphasis on the role of nanomaterials, such as carbon-based nanomaterials and gold-based nanomaterials, functioning as -transducing media and electrically conductive polymers. Finally, the current challenges and emerging trends in this field are also discussed, shedding light on the prospects for developing new aptasensors for tetracycline detection.

Nanostructured lipid carriers in cancer therapy: Advances in passive and active targeting strategies

Nanostructured lipid carriers (NLCs) have emerged as a promising drug delivery platform in cancer therapy, offering advantages such as enhanced drug solubility, stability, and controlled release. Recent efforts have focused on utilizing NLCs for passive and active tumor targeting to improve therapeutic outcomes. This review provides a comprehensive analysis of the role of NLCs in cancer therapy, with particular emphasis on their application in passive and active targeting strategies for precision oncology. Relevant studies were selected from recent literature, focusing on NLC formulation, targeting approaches, and therapeutic applications. NLCs enhance tumor-specific drug delivery through passive targeting via the enhanced permeability and retention (EPR) effect and active targeting via ligand-mediated mechanisms. Lymphatic-targeting NLCs enable improved drug delivery to metastatic niches, while stimuli-responsive NLCs facilitate site-specific release under tumor-associated conditions (e.g., pH, enzymatic activity, redox gradients). Advances in lipid composition, surfactant systems, and conjugation strategies significantly influence drug loading (DL), biodistribution, therapeutic efficacy, and clinical translation across various malignancies. NLCs represent a versatile and adaptable platform for precision cancer therapy. Continued optimization of formulation parameters, functionalization strategies, and clinical translation pathways is essential to fully realize their potential in targeted oncology applications.

Rapid, flexible fabrication of a microfluidic electrochemical chip nucleic acid target for selective, label-free detection of influenza virus DNA using catalytic redox-recycling

H5N1 flu is a highly virulent and variable subtype of influenza with significant epidemic and pandemic potential. In this study, we introduce a novel, maskless, and rapid manufacturing process for a microfluidic chip integrated with electrodes for the quantitative detection of H5N1-DNA sequences. This detection leverages a catalytic redox-recycling signal via a novel Fe₃O₄@TMU-8 nanocomposite, which facilitates the turnover of the oxidation state of [Ru(NH₃)₆]³⁺, thereby amplifying the electrochemical signal output. The positively charged [Ru(NH₃)₆]³⁺ molecule associates with the phosphate backbone of the nucleic acids in H5N1-DNA. Changes in the aptasensor's redox-recycling signal, due to the hybridization of DNA sequences with [Ru(NH₃)₆]³⁺, were used as the electrochemical sensing response. Under optimal conditions, the signal exhibited a linear relationship with H5N1-DNA concentration, ranging from 1 fM to 1 nM, with a detection limit of 0.16 fM. This report details the fabrication of the microfluidic device using Poly(methyl methacrylate) (PMMA) sheet substrates. A laser system was employed to generate microfluidic patterns directly on the PMMA sheet. This biosensing device demonstrated long-term stability and good reproducibility, making it suitable for the quantitative assay of H5N1-DNA sequences. The results from food sample analyses further confirmed the applicability and effectiveness of the resulting biosensor.

Aptamer based immunotherapy: a potential solid tumor therapeutic

Aptamer-based immunotherapy can be a new hope for treating solid tumors with personalized and specific approaches toward cancer therapies. Aptamers are small synthetic single-stranded nucleic acids that may bring in a paradigm shift in treating solid tumors. These are highly selective drugs applied in cellular immunotherapy, cytokine modulation, and immune checkpoint suppression. This review provides an overview of the recent advances in aptamer-based technologies with specific key clinical trials involving AON-D21 and AM003. Aptamers are potently active in immune regulation and tumor targeting. However, aptamer stability and bioavailability are seriously compromised by the issues relating to renal clearance and rapid degradation through nucleases. The latter are reviewed here along with novel improvements, some of which involve chemical modifications that greatly enhance stability and prolong the circulation time; exemplary such modifications are PEGylation, cholesterol conjugation, and the synthesis of circular nucleic acids. The regulatory aspect is also crucial. For example, in addition to specific strategies to prevent drug-drug interactions (DDIs) in cancer remediation medications, this paper underscores the need of risk assessment, particularly because of immunogenicity and organ failure. The use of aptamers is expanded by the development of SOMAmers, X-aptamers, and bioinformatics. To make aptamer-based drugs a major part of cancer treatment, future research should concentrate more on resolving existing issues and expanding their beneficial uses.

Advancing foodborne pathogen detection: a review of traditional and innovative optical and electrochemical biosensing approaches

Foodborne diseases are a significant cause of morbidity (600 million cases) and mortality (420,000 deaths) worldwide every year and are mainly associated with pathogens. Besides the direct effects on human health, they have relevant concerns related to financial, logistics, and infrastructure for the food and medical industries. The standard pathogen identification techniques usually require a sample enrichment step, plating, isolation, and biochemical tests. This process involves specific facilities, a long-time analysis procedures, and skilled personnel. Conversely, biosensors are an emerging innovative approach to detecting pathogens in real time due to their portability, specificity, sensitivity, and low fabrication costs. These advantages can be achieved from the synergistic work between nanotechnology, materials science, and biotechnology for coupling biomolecules in nano-matrices to enhance biosensing performance. This review highlights recent advancements in electrochemical and optical biosensing techniques for detecting bacteria and viruses. Key properties, such as detection limits, are examined, as they depend on factors like the design of the biorecognition molecule, the type of transducer, the target's characteristics, and matrix interferences. Sensitivity levels reported range from 1 to 1 × 10⁸ CFU/mL, with detection times spanning 10 min to 8 h. Additionally, the review explores innovative approaches, including biosensors capable of distinguishing between live and dead bacteria, multimodal sensing, and the simultaneous detection of multiple foodborne pathogens - emerging trends in biosensor development.

Aptamer-Conjugated Multi-Quantum Dot-Embedded Silica Nanoparticles for Lateral Flow Immunoassay

Lateral flow immunoassays (LFIAs) are widely used for their low cost, simplicity, and rapid results; however, enhancing their reliability requires the meticulous selection of ligands and nanoparticles (NPs). SiO2@QD@SiO2 (QD2) nanoparticles, which consist of quantum dots (QDs) embedded in a silica (SiO2) core and surrounded by an outer SiO2 shell, exhibit significantly higher fluorescence intensity (FI) compared to single QDs. In this study, we prepared QD2@PEG@Aptamer, an aptamer conjugated with QD2 using succinimidyl-[(N-maleimidopropionamido)-hexaethyleneglycol]ester, which is 130 times brighter than single QDs, for detecting carbohydrate antigen (CA) 19-9 through LFIA. For LFIA optimization, we determined the optimal conditions as a 1.0:2.0 × 10-2 ratio of polyethylene glycol (PEG) to aptamer by adjusting the amounts of PEG and aptamer, phosphate-buffered saline containing 0.5% Tween® 20 as a developing solution, and 0.15 μg NPs by setting the NP weight during development. Under these conditions, QD2@PEG@Aptamer selectively detected CA19-9, achieving a detection limit of 1.74 × 10-2 mg·mL-1. Moreover, FI remained stable for 10 days after detection. These results highlight the potential of QD2 and aptamer conjugation technology as a reliable and versatile sensing platform for various diagnostic applications.

Efficiency of electrochemical immuno- vs. apta(geno)sensors for multiple cancer biomarkers detection

The interest in biosensors technology has been constantly growing over the last few years. It is still the biggest challenge to design biosensors able to detect two or more analytes in a single measurement. Electrochemical methods are frequently used for this purpose, mainly due to the possibility of applying two or more different redox labels characterized by independent and distinguished electrochemical signals. In addition to antibodies, nucleic acids (aptamers) have been increasingly used as bioreceptors in the construction of such sensors. Within this review paper, we have collected the examples of electrochemical immuno- and geno(apta)sensors for simultaneous detection of multiple analytes. Based on many published literature examples, we have emphasized the recent application of multiplexed platforms for detection of cancer biomarkers. It has allowed us to compare the progress in design strategies, including novel nanomaterials and amplification of signals, to get as low as possible limits of detection. We have focused on multi-electrode and multi-label strategies based on redox-active labels, such as ferrocene, anthraquinone, methylene blue, thionine, hemin and quantum dots, or metal ions such as Ag+, Pb2+, Cd2+, Zn2+, Cu2+ and others. We have finally discussed the possible way of development, challenges and prospects in the area of multianalyte electrochemical immuno- and geno(apta)sensors.

Novel DNA Aptamers to Dickkopf-1 Protein and Their Application in Colorimetric Sandwich Assays for Target Detection in Patients with Axial Spondyloarthritis

Chronic immunoinflammatory rheumatic diseases, such as axial spondyloarthritis (AxSpA), are accompanied by a dysregulation of bone remodeling. Among potential biomarkers of bone metabolism, the Wnt pathway antagonist, Dickkopf-1 (DKK-1), is of particular interest because of its potential to reflect a shift towards joint ossification or osteoporosis, but its diagnostic value needs validation. There is still a lack of stable and efficient methods of measuring serum DKK-1 levels suitable for longitude studies. The use of aptamer-based diagnostic assays could be very promising for this purpose. We generated novel anti-DKK-1 DNA aptamers from a combinatorial library with a pre-defined sequence pattern in the randomized region. This approach showed high efficacy, as only four SELEX rounds of selection produced high-affinity aptamers with dissociation constants ranging from 1.3 to 3.7 nM. A family of their truncated versions was also developed by rational design. Novel DNA aptamers functioned as capture components in a microplate ELISA-like assay with HRP-conjugated anti-DKK-1 antibody as a reporter component. We succeeded in revealing the aptamer/aptamer sandwich pairs that provided an aptamer-only sandwich colorimetric assay. The aptamer/antibody colorimetric test systems were also examined in the analyses of blood serum from AxSpA patients and shown sufficient workability. However, in a number of cases we registered significant differences between assays based on TD10 and DK4 aptamers and made some suggestions about the origin of this effect.

Colorimetric-SERS dual-mode aptasensor for Staphylococcus aureus based on MnO2@AuNPs oxidase-like activity

The nanozyme-linked aptamer-sorbent assay (NLASA) is a rapid way to screen and characterize aptamer binding to targets. In this paper, a MnO2@AuNPs@aptamer (Apt) based NLASA coupled with colorimetric-SERS dual-mode for Staphylococcus aureus (S. aureus) detection is presented. Cu,Fe-CDs were used as the reducing agent to synthesize MnO2 and gold nanoparticles (AuNPs). Then, they were fabricated to obtain MnO2@AuNPs with oxidase (OXD)-like and SERS activities. The S. aureus aptamer was conjugated to MnO2@AuNPs and enhanced the OXD-like activity, which realized the specific capture of S. aureus in food matrices. In addition, S. aureus improves the oxidation of 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid (ABTS) but inhibits 3,3',5,5'-tetramethylbenzidine (TMB) to generate Raman-active oxTMB with MnO2@AuNPs@Apt. This sensor was used for detections of S. aureus in a concentration ranged from 101 to 107 CFU/mL with a detection limit of 0.926 CFU/mL (colorimetric) and 1.561 CFU/mL (SERS), and the recovery is 85%-105% in real samples.

Harnessing the potential of aptamers in cell-derived vesicles for targeting colorectal cancers at Pan-Dukes' stages

Colorectal cancer (CRC) remains one of the most formidable challenges in the global health arena. To address this challenge, extensive research has been directed toward developing targeted drug delivery systems (DDS). Cell-derived vesicles (CDV), which mirror the lipid bilayer structure of cell membranes, have garnered tremendous attention as ideal materials for DDS owing to their scalability in production and high biocompatibility. In this study, a novel method, termed colorectal cancer overall Dukes' staging Systematic Evolution of Ligands by Exponential enrichment (CROSS), was developed to identify Toggle Cell 1 (TC1) aptamers with high binding affinity to CRC cells at various Dukes' stages (A-D). Furthermore, a novel DDS was developed by incorporating a cholesterol-modified TC1 aptamer into CDV, which exhibited improved targeting ability and cellular uptake efficiency toward CRC cells compared to CDV alone. The results of this study highlight the potential efficacy of CDV in constructing a targeted DDS while overcoming the current challenges associated with other lipid-based DDS.

Selection of DNA aptamers that prevent the fibrillization of α-synuclein protein in cellular and mouse models

A neuropathological hallmark of Parkinson's disease (PD) is the aggregation and spreading of misfolded α-synuclein (αSyn) protein. In this study, a selection method was developed to identify aptamers that showed affinity for monomeric αSyn and inhibition of αSyn aggregation. Aptamer a-syn-1 exhibited strong inhibition of αSyn aggregation in vitro by transmission electron microscopy and Thioflavin T fluorescence. A-syn-1-treated SH-SY5Y cells incubated with pre-formed fibrils (PFFs) showed less intracellular aggregation of αSyn in comparison with a scrambled oligonucleotide control, as observed with fluorescent microscopy. Systemic delivery of a-syn-1 to the brain was achieved using a liposome vehicle and confirmed with fluorescence microscopy and qPCR. Transgenic mice overexpressing the human A53T variant of αSyn protein were injected with a-syn-1 loaded liposomes at 5 months of age both acutely (single intraperitoneal [i.p.] injection) and repeatedly (5 i.p. injections over 5 days). Western blot protein quantification revealed that both acute and repeated injections of a-syn-1 decreased levels of the aggregated form of αSyn in the transgenic mice in the prefrontal cortex, caudate, and substania nigra (SNc). These results provide in vitro and in vivo evidence that a-syn-1 can inhibit pathological αSyn aggregation and may have implications in treatment strategies to target dysregulation in PD.

Combination of Capture-SELEX and Post-SELEX for procymidone-specific aptamer selection and broad-specificity aptamer discovery, and development of aptamer-based lateral flow assay

BACKGROUND

Due to its wide application, procymidone has become one of the pesticides with high detection rates in supervision and sampling. Therefore, it is necessary to establish a rapid and efficient method for the detection of procymidone. However, an important bottleneck restricting the development of rapid detection methods of procymidone is that its specific recognition elements are rarely reported. In this work, Capture-SELEX and post-SELEX were used in aptamer screening, and the obtained aptamers were used to construct an aptamer-based lateral flow assay (LFA).

RESULTS

Firstly, a specific aptamer Seq15 was obtained for procymidone by Capture-SELEX, and its dissociation constant (Kd) was 24.22 nM. Secondly, post-SELEX was used to analyze and modify Seq15 to improve its performance, and the Kd of the truncated sequence Seq15-2 was 21.28 nM. In addition to this, the broad-specificity aptamer Seq17-1 was obtained via post-SELEX. Seq17-1 could broadly recognize dicarboximide fungicides (procymidone, iprodione, chlozolinate, dimethachlon and vinclozolin) and their metabolic derivative (3,5-dichloroaniline). Finally, the specific aptamer-based LFA of procymidone was constructed, and the limit of detection (LOD) was 0.79 ng/mL. Meanwhile, the LODs of dicarboximide fungicides and their metabolic derivative were 0.62, 0.64, 0.71, 0.69, 0.64 and 0.66 ng/mL, respectively. The above LFAs were highly specific and stable, and had been successfully used for the detection of vegetable samples.

SIGNIFICANCE

Under the combination of Capture-SELEX and Post-SELEX, this study not only provides specific recognition elements for rapid detection of procymidone, but also provides new ideas for the discovery of broad-specificity aptamers. Combining broad-specificity primary detection and single-specificity quantification, a composite aptamer-based LFA detection platform has been developed, which significantly improves detection efficiency.

Aptamer Screening: Current Methods and Future Trend towards Non-SELEX Approach

Aptamers are nucleic acid sequences that specifically bind with target molecules and are vital to applications such as biosensing, drug development, disease diagnostics, etc. The traditional selection procedure of aptamers is based on the Systematic Evolution of Ligands by an Exponential Enrichment (SELEX) process, which relies on repeating cycles of screening and amplification. With the rapid development of aptamer applications, RNA and XNA aptamers draw more attention than before. But their selection is troublesome due to the necessary reverse transcription and transcription process (RNA) or low efficiency and accuracy of enzymes for amplification (XNA). In light of this, we review the recent advances in aptamer selection methods and give an outlook on future development in a non-SELEX approach, which simplifies the procedure and reduces the experimental costs. We first provide an overview of the traditional SELEX methods mostly designed for screening DNA aptamers to introduce the common tools and methods. Then a section on the current screening methods for RNA and XNA is prepared to demonstrate the efforts put into screening these aptamers and the current difficulties. We further predict that the future trend of aptamer selection lies in non-SELEX methods that do not require nucleic acid amplification. We divide non-SELEX methods into an immobilized format and non-immobilized format and discuss how high-resolution partitioning methods could facilitate the further improvement of selection efficiency and accuracy.

Blood cellular membrane-coated Au/polydopamine nanoparticle-targeted NIR-II antibacterial therapy

Bacterial infections are the primary causes of infectious diseases in humans. In recent years, the abuse of antibiotics has led to the widespread enhancement of bacterial resistance. Concerns have been raised about the identification of a common treatment platform for bacterial infections. In this study, a composite nanomaterial was used for near-infrared II (NIR-II) photothermal antibacterial treatment. Red blood cell membrane was peeled and coated onto the surface of the Au/polydopamine nanoparticle-containing aptamer. The composite nanomaterials based on Au/polydopamine exhibit highest photothermal conversion capability. Moreover, these assembled nanoparticles can quickly enter the body's circular system with a specific capability to recognise bacteria. In vivo experiments demonstrated that the composites could kill bacteria from infected blood while significantly reducing the level of bacteria in various organs. Such assemblies offer a paradigm for the treatment of bacterial infections caused by the side effects of antibiotics.

A microfluidic ratiometric electrochemical aptasensor for highly sensitive and selective detection of 3,3',4,4'-tetrachlorobiphenyl

This study proposes a strategy using a microfluidic ratiometric electrochemical aptasensor to detect PCB77 with excellent sensitivity and specificity. This sensing platform combines a microfluidic chip, a wireless integrated circuit system for aptamer-based electrochemical detection, and a mobile phone control terminal for parameter configuration, identification, observation, and wireless data transfer. The sensing method utilizes a cDNA (MB-COOH-cDNA-SH) that is labelled with the redox probe Methylene Blue (MB) at the 5' end and has a thiol group at the 3' end. Additionally, it utilizes a single strand PCB aptamer that has been modified with ferrocenes at the 3' end (aptamer-Fc). Through gold-thiol binding, the labelled probe of MB-COOH-cDNA-SH was self-assembled onto the surface of an Au/Nb2CTx/GO modified electrode. On exposure to aptamer-Fc, it will hybridize with MB-COOH-cDNA-SH to form a stable double-stranded structure on the electrode surface. When PCB77 is present, aptamer-Fc binds specifically to the target, enabling the double-stranded DNA to unwind. Such variation caused changes in the differential pulse voltammetry (DPV) peak currents of both MB and Fc. A substantial improvement is observed in the ratio between the two DPV peaks. Under the optimum experimental conditions, this assay has a response that covers the 0.0001 to 1000 ng mL-1 PCB77 concentration range, and the detection limit is 1.56 × 10-5 ng mL-1. The integration of a ratiometric electrochemical aptasensor with designed microfluidic and integrated devices in this work is an innovative and promising approach that offers an efficient platform for on-site applications.

In Vivo Evaluation of 68Ga-Labeled NOTA-EGFRvIII Aptamer in EGFRvIII-Positive Glioblastoma Xenografted Model

EGFRvIII is expressed only in tumor cells and strongly in glioblastoma and is considered a promising target in cancer diagnosis and therapy. Aptamers are synthetic single-stranded oligonucleotides that bind to biochemical target molecules with high binding affinity and specificity. This study examined the potential of the 68Ga-NOTA-EGFRvIII aptamer as a nuclear imaging probe for visualizing EGFRvIII-expressing glioblastoma by positron emission tomography (PET). EGFRvIII aptamer was selected using the SELEX technology, and flow cytometry and fluorescence microscopy verified the high binding affinity to EGFRvIII positive U87MG vIII 4.12 glioma cells but not to EGFRvIII negative U87MG cells. The EGFRvIII aptamer was conjugated with a chelator (1,4,7-triazanonane-1,4,7-triyl)triacetic acid (NOTA) for 68Ga-labeling. The 68Ga-NOTA-EGFRvIII aptamer was prepared using the preconcentration-based labeling method with a high radiolabeling yield at room temperature. Ex vivo biodistribution analyses confirmed the significantly higher tumor uptake of the 68Ga-NOTA-EGFRvIII aptamer in EGFRvIII-expressing xenograft tumors than that in EGFRvIII negative tumors, confirming the specific tumor uptake of the 68Ga-NOTA-EGFRvIII aptamer in vivo. PET imaging studies revealed a high retention rate of the 68Ga-NOTA-EGFRvIII aptamer in U87MG vIII 4.12 tumors but only low uptake levels in U87-MG tumors, suggesting that the 68Ga-NOTA-EGFRvIII aptamer may be used as a PET imaging agent for EGFRvIII-expressing glioblastoma.

A enzyme-free fluorescence quenching sensor for amplified detection of kanamycin in milk based on competitive triggering strategies

In this work, we constructed a FAM fluorescence quenching biosensor based on an aptamer competition recognition and enzyme-free amplification strategy. We design a competing unit consisting of an aptamer chain and a complementary chain, and a catalytic hairpin self-assembly (CHA) unit consisting of two hairpins in which the complementary chain can trigger the catalytic hairpin self-assembly. In the initial state, the aptamer chain is combined with the complementary chain, the catalytic hairpin self-assembly unit is inhibited, the FAM fluorescence group was far away from the BHQ1 quenching group, and the fluorescence is turn-on. In the presence of kanamycin, the aptamer chain recognizes kanamycin and doesn't form double chains, resulting in the free complementary chain triggering hairpin 1 (H1), and then H1 triggering hairpin 2 (H2), FAM fluorophore is close to the BHQ1 quenching group, and the fluorescence is off-on. When H1 and H2 form a cyclic reaction, enzyme-free amplification is achieved and there is significant output of the fluorescence signal. Therefore, the biosensor has good performance in detecting kanamycin, the detection line is 54 nM, the linear range is 54 nM-0.9 μM, and it can achieve highly selective detection of kanamycin. Kanamycin residue may cause serious harm to human health. The high sensitivity detection of kanamycin is urgent, so this project has a great application potential for food detection.

An overview of aptamer: Design strategy, prominent applications, and potential challenge in plants

Aptamers, serving as highly efficient molecular recognition and biotechnology tools, have garnered increasing interest in the realm of plant science in recent years. Aptamers are synthetic single-stranded short nucleotides or peptides, that bind targets with high specificity and affinity, triggering precise biological responses. As an alternative to antibodies, aptamers present promising avenues for advancement in biological researches. Aptamers function in a range of fields, encompassing cell signaling, drug development, biosensor technology, as well as botany, agricultural and forestry sciences. In this review, we introduce classifications and screening methods of aptamers, as well as aptamer-based technologies, highlighting their significant contributions to recent advancements. With their powerful functionality and ability to bind targets with high specificity and affinity, aptamers offer promising opportunities for breakthroughs in plant research.

Non-immobilized GO-SELEX screening of aptamers against cyclosporine A and its application in a AuNPs colorimetric aptasensor

Cyclosporine A (CsA) is an immunosuppressive drug that is widely used in clinical practice. Due to its narrow therapeutic window and the significant differences between individuals, the therapeutic drug monitoring (TDM) of CsA is required to ensure patient safety. In this study, we screened a novel aptamer, named CsA7, which could specifically recognize CsA, and developed a AuNPs colorimetric aptasensor for the rapid detection of CsA. In the SELEX process, after eight rounds of screening, four aptamer candidate sequences were obtained and subjected to binding affinity and specificity tests. Finally, the CsA7 aptamer (Kd = 41.21 ng mL-1) showed the highest affinity for CsA. Based on CsA7, we also developed a AuNPs colorimetric aptasensor, which had a detection limit of 0.1 ng mL-1 and a quantitative range of 0.1-500 ng mL-1 and showed good selectivity among CsA and its analogs. According to the results, the CsA7 aptamer provides an alternative recognition molecule to the antibody in biosensor applications and shows great potential for the rapid and convenient detection of CsA.

Clinical Translation of Aptamers for COVID-19

The COVID-19 etiologic agent, SARS-CoV-2, continues to be one of the leading causes of death on a global scale. Although efficient methods for diagnosis and treatment of COVID-19 have been developed, new methods of battling SARS-CoV-2 variants and long COVID are still urgently needed. A number of aptamers have demonstrated tremendous potential to be developed into diagnostic and therapeutic agents for COVID-19. The translation of the aptamers for clinical uses, however, has been extremely slow. Overcoming the difficulties faced by aptamers would advance this technology toward clinical use for COVID-19 and other serious disorders.

Towards better antivenoms: navigating the road to new types of snakebite envenoming therapies

Snakebite envenoming is a significant global health challenge, and for over a century, traditional plasma-derived antivenoms from hyperimmunized animals have been the primary treatment against this infliction. However, these antivenoms have several inherent limitations, including the risk of causing adverse reactions when administered to patients, batch-to-batch variation, and high production costs. To address these issues and improve treatment outcomes, the development of new types of antivenoms is crucial. During this development, key aspects such as improved clinical efficacy, enhanced safety profiles, and greater affordability should be in focus. To achieve these goals, modern biotechnological methods can be applied to the discovery and development of therapeutic agents that can neutralize medically important toxins from multiple snake species. This review highlights some of these agents, including monoclonal antibodies, nanobodies, and selected small molecules, that can achieve broad toxin neutralization, have favorable safety profiles, and can be produced on a large scale with standardized manufacturing processes. Considering the inherent strengths and limitations related to the pharmacokinetics of these different agents, a combination of them might be beneficial in the development of new types of antivenom products with improved therapeutic properties. While the implementation of new therapies requires time, it is foreseeable that the application of biotechnological advancements represents a promising trajectory toward the development of improved therapies for snakebite envenoming. As research and development continue to advance, these new products could emerge as the mainstay treatment in the future.

Recent Advances in Design and Application of Nanomaterials-Based Colorimetric Biosensors for Agri-food Safety Analysis

A colorimetric sensor detects an analyte by utilizing the optical properties of the sensor unit, such as absorption or reflection, to generate a structural color that serves as the output signal to detect an analyte. Detecting the refractive index of an analyte by recording the color change of the sensor structure on its surface has several advantages, including simple operation, low cost, suitability for onsite analysis, and real-time detection. Colorimetric sensors have drawn much attention owing to their rapidity, simplicity, high sensitivity and selectivity. This Review discusses the use of colorimetric sensors in the food industry, including their applications for detecting food contaminants. The Review also provides insight into the scope of future research in this area.

An efficient extraction method for short single-stranded DNA from agarose gels in aptamer screening

With the rapid advancements in aptamer screening, the efficient extraction of short single-stranded DNA (ssDNA) from agarose gel has become a new requirement. However, the currently available products are primarily designed for double-stranded DNA (dsDNA) and exhibit limited efficacy when applied to the extraction of short ssDNA. In this study, we successfully developed a novel method based on amino-modified silica-coated magnetic particles (ASMPs) for the extraction of short ssDNA from agarose gel. The gel slices containing short ssDNA were subjected to centrifugation in a spin column/centrifugation tube assembly with silica wool, followed by the adsorption using ASMPs. Subsequently, reagents containing phosphate groups were employed to desorb ssDNA from the surface of ASMPs. Through optimization of each step, we realized remarkable efficiency in the extraction of short ssDNA. To assess the efficacy of our method, we utilized it in aptamer screening. The results demonstrated that our method outperformed three commercially available DNA gel extraction products (Q-kit, S-kit, and V-kit). The relative recovery rates of all methods were as follows: M-dNTP (100.00 %) > M-BB (63.38 %) > Q-kit (46.64 %) > S-kit (15.98 %) > V-kit (0.38 %). The results strongly suggest that the developed method holds promise for short ssDNA extraction from agarose gel.

An electrostatically conjugated-functional MNK1 aptamer reverts the intrinsic antitumor effect of polyethyleneimine-coated iron oxide nanoparticles in vivo in a human triple-negative cancer xenograft

Background

Triple-negative breast cancer (TNBC) remains a difficult breast cancer subtype to treat as it exhibits a particularly aggressive behavior. The dysregulation of distinct signaling pathways underlies this aggressive behavior, with an overactivation of MAP kinase interacting kinases (MNKs) promoting tumor cell behavior, and driving proliferation and migration. Therefore, MNK1 is an excellent target to impair the progression of TNBC and indeed, an MNK1-specific aptamer has proved to be efficient in inhibiting TBNC cell proliferation in vitro. Although polyethyleneimine-coated iron oxide nanoparticles (PEI–IONPs) have been used as transfection and immunomodulating agents, no study has yet addressed the benefits of using these nanoparticles as a magnetic carrier for the delivery of a functional aptamer.

Results

Here, we tested the antitumor effect of a PEI–IONP complexed to the functional MNK1b-specific aptamer in vitro and in vivo. We demonstrated that these apMNKQ2@PEI–IONP nanoconjugates delivered three times more apMNKQ2 to MDA-MB-231 cells than the aptamer alone, and that this enhanced intracellular delivery of the aptamer had consequences for MNK1 signaling, reducing the amount of MNK1 and its target the phospho(Ser209)-eukaryotic initiation factor 4E (eIF4E). As a result, a synergistic effect of the apMNKQ2 and PEI–IONPs was observed that inhibited MDA-MB-231 cell migration, probably in association with an increase in the serum and glucocorticoid-regulated kinase-1 (SGK1) and the phospho(Thr346)-N-myc down-regulated gene 1 (NDRG1). However, intravenous administration of the apMNKQ2 alone did not significantly impair tumor growth in vivo, whereas the PEI–IONP alone did significantly inhibit tumor growth. Significantly, tumor growth was not inhibited when the apMNKQ2@PEI–IONP nanocomplex was administered, possibly due to fewer IONPs accumulating in the tumor. This apMNKQ2-induced reversion of the intrinsic antitumor effect of the PEI–IONPs was abolished when an external magnetic field was applied at the tumor site, promoting IONP accumulation.

Conclusions

Electrostatic conjugation of the apMNKQ2 aptamer with PEI–IONPs impedes the accumulation of the latter in tumors, which appears to be necessary for PEI–IONPs to exert their antitumor activity.

Graphical Abstract

Modified nucleic acid aptamers: development, characterization, and biological applications

Aptamers are single-stranded oligonucleotides that bind to their targets via specific structural interactions. To improve the properties and performance of aptamers, modified nucleotides are incorporated during or after a selection process such as systematic evolution of ligands by exponential enrichment (SELEX). We summarize the latest modified nucleotides and strategies used in modified (mod)-SELEX and post-SELEX to develop modified aptamers, highlight the methods used to characterize aptamer-target interactions, and present recent progress in modified aptamers that recognize different targets. We discuss the challenges and perspectives in further advancing the methodologies and toolsets to accelerate the discovery of modified aptamers, improve the throughput of aptamer-target characterization, and expand the functional diversity and complexity of modified aptamers.

Composition and Anticoagulant Potential of Chondroitin Sulfate and Dermatan Sulfate from Inedible Parts of Garfish (Belone belone)

Glycosaminoglycans (GAGs) play a crucial role due to their significant biomedical functions. Chondroitin sulfate (CS) and dermatan sulfate (DS), the main representative family of GAGs, were extracted and purified from garfish (Belone belone) by-products, i.e., skin (GSB), bones (GCB), and heads (GHB), and their composition and anticoagulant activity were investigated. CS/DS were purified by ion-exchange chromatography with yields of 8.1% for heads, 3.7% for skin, and 1.4% for bones. Cellulose acetate electrophoresis was also explored for analyzing the extracted CS/DS. Interestingly, GHB, GSB, and GCB possessed sulfate contents of 21 ± 2%, 20 ± 1%, and 20 ± 1.5%, respectively. Physico-chemical analysis showed that there were no significant differences (p > 0.05) between the variances for sulfate, uronic acid, and total sugars in the GAGs extracted from the different parts of fish. Disaccharide analysis by SAX-HPLC showed that the GSB and GCB were predominately composed of ΔDi-4S [ΔUA-GalNAc 6S] (74.78% and 69.22%, respectively) and ΔDi-2,4S [ΔUA2S-GalNAc 4S] (10.92% and 6.55%, respectively). However, the GHB consisted of 25.55% ΔDi-6S [ΔUA-GalNAc 6S] and 6.28% ΔDi-2,6S [ΔUA2S-GalNAc 4S]. Moreover, classical anticoagulation tests were also used to measure their anticoagulant properties in vitro, which included the activated partial thromboplastin time, prothrombin time, and thrombin time. The CS/DS isolated from garfish by-products exhibited potent anticoagulant effects. The purified CS/DS showed exceptional anticoagulant properties according to this research and can be considered as a new agent with anticoagulant properties.

Truncated Electrochemical Aptasensor with Enhanced Antifouling Capability for Highly Sensitive Serotonin Detection

Accurate determination of serotonin (ST) provides insight into neurological processes and enables applications in clinical diagnostics of brain diseases. Herein, we present an electrochemical aptasensor based on truncated DNA aptamers and a polyethylene glycol (PEG) molecule-functionalized sensing interface for highly sensitive and selective ST detection. The truncated aptamers have a small size and adopt a stable stem-loop configuration, which improves the accessibility of the aptamer for the analyte and enhances the sensitivity of the aptasensor. Upon target binding, these aptamers perform a conformational change, leading to a variation in the Faraday current of the redox tag, which was recorded by square wave voltammetry (SWV). Using PEG as blocking molecules minimizes nonspecific adsorption of other interfering molecules and thus endows an enhanced antifouling ability. The proposed electrochemical aptamer sensor showed a wide range of detection lasting from 0.1 nM to 1000 nM with a low limit of detection of 0.14 nM. Owing to the unique properties of aptamer receptors, the aptasensor also exhibits high selectivity and stability. Furthermore, with the reduced unspecific adsorption, assaying of ST in human serum and artificial cerebrospinal fluid (aCSF) showed excellent performance. The reported strategy of utilizing antifouling PEG describes a novel approach to building antifouling aptasensors and holds great potential for neurochemical investigations and clinical diagnosis.

Electrochemical Wearable Biosensors and Bioelectronic Devices Based on Hydrogels: Mechanical Properties and Electrochemical Behavior

Hydrogel-based wearable electrochemical biosensors (HWEBs) are emerging biomedical devices that have recently received immense interest. The exceptional properties of HWEBs include excellent biocompatibility with hydrophilic nature, high porosity, tailorable permeability, the capability of reliable and accurate detection of disease biomarkers, suitable device-human interface, facile adjustability, and stimuli responsive to the nanofiller materials. Although the biomimetic three-dimensional hydrogels can immobilize bioreceptors, such as enzymes and aptamers, without any loss in their activities. However, most HWEBs suffer from low mechanical strength and electrical conductivity. Many studies have been performed on emerging electroactive nanofillers, including biomacromolecules, carbon-based materials, and inorganic and organic nanomaterials, to tackle these issues. Non-conductive hydrogels and even conductive hydrogels may be modified by nanofillers, as well as redox species. All these modifications have led to the design and development of efficient nanocomposites as electrochemical biosensors. In this review, both conductive-based and non-conductive-based hydrogels derived from natural and synthetic polymers are systematically reviewed. The main synthesis methods and characterization techniques are addressed. The mechanical properties and electrochemical behavior of HWEBs are discussed in detail. Finally, the prospects and potential applications of HWEBs in biosensing, healthcare monitoring, and clinical diagnostics are highlighted.

Few Layer Ti3C2 MXene-Based Label-Free Aptasensor for Ultrasensitive Determination of Chloramphenicol in Milk

Quantitative detection of veterinary drug residues in animal-derived food is of great significance. In this work, a simple and label-free electrochemical aptasensor for the highly sensitive detection of chloramphenicol (CAP) in milk was successfully developed based on a new biosensing method, where the single- or few-layer Ti3C2 MXene nanosheets functionalized via the specific aptamer by self-assembly were used as electrode modifiers for a glassy carbon electrode (aptamer/Ti3C2 MXene/GCE). Differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM), atomic force microscope (AFM), and so on were utilized for electrochemical and morphological characterization. Under the optimized conditions, the constructed aptasensor exhibited excellent performance with a wider linearity to CAP in the range from 10 fM to 1 μM and a low detection limit of 1 fM. Aptamer/Ti3C2 MXene/GCE demonstrated remarkable selectivity over other potentially interfering antibiotics, as well as exceptional reproducibility and stability. In addition, the aptasensor was successfully applied to determine CAP in milk with acceptable recovery values of 96.13% to 108.15% and relative standard deviations below 9%. Therefore, the proposed electrochemical aptasensor is an excellent alternative for determining CAP in food samples.

Aptamer-Based Strategies to Boost Immunotherapy in TNBC

The immune system (IS) may play a crucial role in preventing tumor development and progression, leading, over the last years, to the development of effective cancer immunotherapies. Nevertheless, immune evasion, the capability of tumors to circumvent destructive host immunity, remains one of the main obstacles to overcome for maximizing treatment success. In this context, promising strategies aimed at reshaping the tumor immune microenvironment and promoting antitumor immunity are rapidly emerging. Triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with poor outcomes, is highly immunogenic, suggesting immunotherapy is a viable strategy. As evidence of this, already, two immunotherapies have recently become the standard of care for patients with PD-L1 expressing tumors, which, however, represent a low percentage of patients, making more active immunotherapeutic approaches necessary. Aptamers are short, highly structured, single-stranded oligonucleotides that bind to their protein targets at high affinity and specificity. They are used for therapeutic purposes in the same way as monoclonal antibodies; thus, various aptamer-based strategies are being actively explored to stimulate the IS’s response against cancer cells. The aim of this review is to discuss the potential of the recently reported aptamer-based approaches to boost the IS to fight TNBC.

bioTCIs: Middle-to-Macro Biomolecular Targeted Covalent Inhibitors Possessing Both Semi-Permanent Drug Action and Stringent Target Specificity as Potential Antibody Replacements

Monoclonal antibody therapies targeting immuno-modulatory targets such as checkpoint proteins, chemokines, and cytokines have made significant impact in several areas, including cancer, inflammatory disease, and infection. However, antibodies are complex biologics with well-known limitations, including high cost for development and production, immunogenicity, a limited shelf-life because of aggregation, denaturation, and fragmentation of the large protein. Drug modalities such as peptides and nucleic acid aptamers showing high-affinity and highly selective interaction with the target protein have been proposed alternatives to therapeutic antibodies. The fundamental limitation of short in vivo half-life has prevented the wide acceptance of these alternatives. Covalent drugs, also known as targeted covalent inhibitors (TCIs), form permanent bonds to target proteins and, in theory, eternally exert the drug action, circumventing the pharmacokinetic limitation of other antibody alternatives. The TCI drug platform, too, has been slow in gaining acceptance because of its potential prolonged side-effect from off-target covalent binding. To avoid the potential risks of irreversible adverse drug effects from off-target conjugation, the TCI modality is broadening from the conventional small molecules to larger biomolecules possessing desirable properties (e.g., hydrolysis resistance, drug-action reversal, unique pharmacokinetics, stringent target specificity, and inhibition of protein-protein interactions). Here, we review the historical development of the TCI made of bio-oligomers/polymers (i.e., peptide-, protein-, or nucleic-acid-type) obtained by rational design and combinatorial screening. The structural optimization of the reactive warheads and incorporation into the targeted biomolecules enabling a highly selective covalent interaction between the TCI and the target protein is discussed. Through this review, we hope to highlight the middle to macro-molecular TCI platform as a realistic replacement for the antibody.

Potential Therapeutic Use of Aptamers against HAT1 in Lung Cancer

Lung cancer is one of the leading causes of death worldwide and the most common of all cancer types. Histone acetyltransferase 1 (HAT1) has attracted increasing interest as a potential therapeutic target due to its involvement in multiple pathologies, including cancer. Aptamers are single-stranded RNA or DNA molecules whose three-dimensional structure allows them to bind to a target molecule with high specificity and affinity, thus making them exceptional candidates for use as diagnostic or therapeutic tools. In this work, aptamers against HAT1 were obtained, subsequently characterized, and optimized, showing high affinity and specificity for HAT1 and the ability to inhibit acetyltransferase activity in vitro. Of those tested, the apHAT610 aptamer reduced cell viability, induced apoptosis and cell cycle arrest, and inhibited colony formation in lung cancer cell lines. All these results indicate that the apHAT610 aptamer is a potential drug for the treatment of lung cancer.

Loop-Mediated Isothermal Amplification: From Theory to Practice

Increasing the accuracy of pathogen identification and reducing the duration of analysis remain relevant for modern molecular diagnostics up to this day. In laboratory and clinical practice, detection of pathogens mostly relies on methods of nucleic acid amplification, among which the polymerase chain reaction (PCR) is considered the "gold standard." Nevertheless, in some cases, isothermal amplification methods act as an alternative to PCR diagnostics. Upon more than thirty years of the development of isothermal DNA synthesis, the appearance of loop-mediated isothermal amplification (LAMP) has enabled new directions of in-field diagnostics of bacterial and viral infections. This review examines the key characteristics of the LAMP method and corresponding features in practice. We discuss the structure of LAMP amplicons with single-stranded loops, which have the sites for primer annealing under isothermal conditions. The latest achievements in the modification of the LAMP method are analyzed, which allow considering it as a unique platform for creating the next-generation diagnostic assays.

An optimized MNK1b aptamer, apMNKQ2, and its potential use as a therapeutic agent in breast cancer

Breast cancer is the most commonly diagnosed and leading cause of cancer death among women worldwide. Mitogen-activated protein kinase-interacting kinases (MNKs) promote the expression of several oncogenic proteins and are overexpressed in several types of cancer. In human cells, there are four isoforms of MNKs. The truncated isoform MNK1b, first described in our laboratory, has a higher basal activity and is constitutively active. Aptamers are emerging in recent years as potential therapeutic agents that show significant advantages over drugs of other nature. We have previously obtained and characterized a highly specific aptamer against MNK1b, named apMNK2F, with a dissociation constant in the nanomolar range, which produces significant inhibition of proliferation, migration, and colony formation in breast cancer cells. Furthermore, its sequence analysis predicted two G-quadruplex structures. In this work, we show the optimization process of the aptamer to reduce its size, improving its stability. The obtained aptamer, named apMNKQ2, is able to inhibit proliferation, colony formation, migration, and invasion in breast cancer cells. In murine models of breast cancer, apMNKQ2 has demonstrated its efficacy in reducing tumor volume and the number of metastases. In conclusion, apMNKQ2 could be used as an anti-tumor drug in the future.

Therapeutic Potential of Aptamer-Protein Interactions

Aptamers are single-stranded oligonucleotides (RNA or DNA) with a typical length between 25 and 100 nucleotides which fold into three-dimensional structures capable of binding to target molecules. Specific aptamers can be isolated against a large variety of targets through efficient and relatively cheap methods, and they demonstrate target-binding affinities that sometimes surpass those of antibodies. Consequently, interest in aptamers has surged over the past three decades, and their application has shown promise in advancing knowledge in target analysis, designing therapeutic interventions, and bioengineering. With emphasis on their therapeutic applications, aptamers are emerging as a new innovative class of therapeutic agents with promising biochemical and biological properties. Aptamers have the potential of providing a feasible alternative to antibody- and small-molecule-based therapeutics given their binding specificity, stability, low toxicity, and apparent non-immunogenicity. This Review examines the general properties of aptamers and aptamer-protein interactions that help to understand their binding characteristics and make them important therapeutic candidates.

Multi-target tyrosine kinase inhibitor nanoparticle delivery systems for cancer therapy

Multi-target Tyrosine Kinase Inhibitors (MTKIs) have drawn substantial attention in tumor therapy. MTKIs could inhibit tumor cell proliferation and induce apoptosis by blocking the activity of tyrosine kinase. However, the toxicity and drug resistance of MTKIs severely restrict their further clinical application. The nano pharmaceutical technology based on MTKIs has attracted ever-increasing attention in recent years. Researchers deliver MTKIs through various types of nanocarriers to overcome drug resistance and improve considerably therapeutic efficiency. This review intends to summarize comprehensive applications of MTKIs nanoparticles in malignant tumor treatment. Firstly, the mechanism and toxicity were introduced. Secondly, various nanocarriers for MTKIs delivery were outlined. Thirdly, the combination treatment schemes and drug resistance reversal strategies were emphasized to improve the outcomes of cancer therapy. Finally, conclusions and perspectives were summarized to guide future research.

Aptamers as Smart Ligands for Targeted Drug Delivery in Cancer Therapy

Undesirable side effects and multidrug tolerance are the main holdbacks to the treatment of cancer in conventional chemotherapy. Fortunately, targeted drug delivery can improve the enrichment of drugs at the target site and reduce toxicity to normal tissues and cells. A targeted drug delivery system is usually composed of a nanocarrier and a targeting component. The targeting component is called a "ligand". Aptamers have high target affinity and specificity, which are identified as attractive and promising ligands. Therefore, aptamers have potential application in the development of smart targeting systems. For instance, aptamers are able to efficiently recognize tumor markers such as nucleolin, mucin, and epidermal growth factor receptor (EGFR). Besides, aptamers can also identify glycoproteins on the surface of tumor cells. Thus, the aptamer-mediated targeted drug delivery system has received extensive attention in the application of cancer therapy. This article reviews the application of aptamers as smart ligands for targeted drug delivery in cancer therapy. Special interest is focused on aptamers as smart ligands, aptamer-conjugated nanocarriers, aptamer targeting strategy for tumor microenvironment (TME), and aptamers that are specified to crucial cancer biomarkers for targeted drug delivery.

An electrochemical aptasensor based on target triggered multiple-channel DNAzymes cycling amplification strategy with PtFe@Co-MOF as signal amplifier

A novel electrochemical aptasensor for the detection of Aflatoxin B1 (AFB1) was developed for the first time by using the target-triggered multiple-channel deoxyribozymes (DNAzymes) cycling amplified assay with Pt Fe doped NH₂-Co-MOF (PtFe@Co-MOF) as a signal amplifier. In the presence of AFB1, a self-assembling cross-over nucleic structure could be triggered by AFB1 via two aptamers' structure switching for strand displacement, resulting in four channels of Mg²⁺-dependent DNAzyme recycling simultaneously to multiply the detection signals. These DNAzymes cyclically split the substrate sequence to release the PtFe@Co-MOF labeled detection probe (DP), which is subsequently hybridized with the capture probes on the Au-deposited glassy carbon electrode. The fabrication procedure was characterized by differential pulse voltammetry, and the results of the morphological and element composition characteristics methods were analyzed to determine the successful preparation of PtFe@Co-MOF. The limit of detection (LOD) for AFB1 detection was 2 pg mL^-1 with a linear range from 5 pg mL^-1 to 80 ng mL^-1. By comparison, the enhanced detection sensitivity has been found to originate from the efficient shearing of DNAzymes, enhanced peroxidase-like capability, and multiple active sites of PtFe@Co-MOF. Besides, this aptasensor showed high specificity for AFB1 compared with similar mycotoxins and exhibited high accuracy with low experimental cost and easy operation. Furthermore, the unique design of electrochemical aptasensors could provide a promising platform for the onsite determination of AFB1, as well as other targets by replacing the aptamer and other core recognition sequences.

Intranasal delivery: An attractive route for the administration of nucleic acid based therapeutics for CNS disorders

The etiologies of several cardiovascular, inflammatory, neurological, hereditary disorders, cancer, and infectious diseases have implicated changes in the genetic set up or genetic mutations as the root cause. Nucleic acid based therapeutics (NBTs) is a new class of biologics that are known to regulate gene expression at the transcriptional and post-transcriptional level. The NBTs include oligonucleotides, nucleosides, antisense RNA, small interfering RNAs, micro RNA etc. In recent times, this new category of biologics has found enormous potential in the management of cardiovascular, inflammatory, neurological disorders, cancer, infectious diseases and organ transplantation. However, the delivery of NBTs is highly challenging in terms of target specificity (intracellular delivery), mononuclear phagocyte system uptake, stability and biodistribution. Additionally, management of the above mentioned disorders require regular and intrusive therapy making non-invasive routes preferable in comparison to invasive routes like parenteral. The nasal route is garnering focus in delivery of NBTs to the brain in the management of several CNS disorders due to the associated merits such as non-invasiveness, possibility of chronic delivery, improved patient compliance, avoidance of hepatic and gastrointestinal metabolism as well as ability to bypass the BBB. Hence in recent times, this route has been sought by the reserachers as an alternative to parenteral therapy for the delivery of several NBTs. This review shall focus on an array of NBTs delivered through nasal route, their challenges, applications and opportunities. The novel delivery systems for incorporating NBTs; their targeting strategies shall be critically reviewed. The challenges towards regulatory approvals and commercialization shall also be discussed at large. Comparison of learnings derived from the success and barriers in nasal delivery of NBTs will help in identification of futuristic opportunities for their translation from bench to bedside.

Aptamers Targeting Hallmark Proteins of Neurodegeneration

Neurodegeneration is a progressive deterioration of neural structures leading to cognitive or motor impairment of the affected patient. There is still no effective therapy for any of the most common neurodegenerative diseases (NDs) such as Alzheimer's or Parkinson's disease. Although NDs exhibit distinct clinical characteristics, many are characterized by the accumulation of misfolded proteins or peptide fragments in the brain and/or spinal cord. The presence of similar inclusion bodies in patients with diverse NDs provides a rationale for developing therapies directed at overlapping disease mechanisms. A novel targeting strategy involves the use of aptamers for therapeutic development. Aptamers are short nucleic acid ligands able to recognize molecular targets with high specificity and high affinity. Despite the fact that several academic groups have shown that aptamers have the potential to be used in therapeutic and diagnostic applications, their clinical translation is still limited. In this study, we describe aptamers that have been developed against proteins relevant to NDs, including prion protein and amyloid beta (Aβ), cell surface receptors and other cytoplasmic proteins. This review also describes advances in the application of these aptamers in imaging, protein detection, and protein quantification, and it provides insights about their accelerated clinical use for disease diagnosis and therapy.

Rapid and Wash-Free Time-Gated FRET Histamine Assays Using Antibodies and Aptamers

Histamine (HA) is an indicator of food freshness and quality. However, high concentrations of HA can cause food poisoning. Simple, rapid, sensitive, and specific quantification can enable efficient screening of HA in food and beverages. However, conventional assays are complicated and time-consuming, as they require multiple incubation, washing, and separation steps. Here, we demonstrate that time-gated Förster resonance energy transfer (TG-FRET) between terbium (Tb) complexes and organic dyes can be implemented in both immunosensors and aptasensors for simple HA quantification using a rapid, single-step, mix-and-measure assay format. Both biosensors could quantify HA at concentrations relevant in food poisoning with limits of detection of 0.19 μg/mL and 0.03 μg/mL, respectively. Excellent specificity was documented against the structurally similar food components tryptamine and l-histidine. Direct applicability of the TG-FRET assays was demonstrated by quantifying HA in spiked fish and wine samples with both excellent concentration recovery and agreement with conventional multistep enzyme-linked immunosorbent assays (ELISAs). Our results show that the simplicity and rapidity of TG-FRET assays do not compromise sensitivity, specificity, and reliability, and both immunosensors and aptasensors have a strong potential for their implementation in advanced food safety screening.

Advancements in the characterisation of oligonucleotides by high performance liquid chromatography-mass spectrometry in 2021: A short review

The first oligonucleotide therapeutic was approved by the Food and Drug Administration in 1998, and since then, 12 nucleic acids have been commercialised as medicines. To be approved, the oligonucleotides need to be identified and characterised as well as its related impurities. Different methods exist, but the most commonly used is ion-pairing reversed-phase liquid chromatography with tandem mass spectrometry. The separation obtained depends on the mobile phase and column used. Other methods have been developed, notably by using hydrophilic interaction chromatography and two-dimensional high performance liquid chromatography. Furthermore, ion-pairing reversed-phase high performance liquid chromatography ultra-violet spectroscopy detection and mass spectrometry has been optimised for the analysis of methylated nucleobases due to the utilisation of this modification in the drugs. This review covers the recent advancements in the analysis and characterisation of oligonucleotides in 2021 by high performance liquid chromatography mass spectrometry, notably by hydrophilic interaction chromatography and two-dimensional liquid chromatography but also the different parameters that influence the analysis by ion-pairing reversed-phase high performance liquid chromatography, the characterisation of methylated nucleobases, and the recent software developed for oligonucleotides.

An Update of Nucleic Acids Aptamers Theranostic Integration with CRISPR/Cas Technology

The clustered regularly interspaced short palindromic repeat (CRISPR)/Cas system is best known for its role in genomic editing. It has also demonstrated great potential in nucleic acid biosensing. However, the specificity limitation in CRISPR/Cas has created a hurdle for its advancement. More recently, nucleic acid aptamers known for their high affinity and specificity properties for their targets have been integrated into CRISPR/Cas systems. This review article gives a brief overview of the aptamer and CRISPR/Cas technology and provides an updated summary and discussion on how the two distinctive nucleic acid technologies are being integrated into modern diagnostic and therapeutic applications

Aptamers Against COVID-19: An Untested Opportunity

Given the lack of success in the development of effective drugs to treat COVID-19, which show "game-changing" potential, it is necessary to explore drugs with different modes of action. Single mode-of-action drugs have not been succeeded in curing COVID-19, which is a highly complex disease. This is the case for direct antivirals and anti-inflammatory drugs, both of which treat different phases of the disease. Aptamers are molecules that deliver different modes of action, allowing their effects to be bundled, which, when combined, support their therapeutic efficacy. In this minireview, we summarise the current activities in the development of aptamers for the treatment of COVID-19 and long-COVID. A special emphasis is placed on the capability of their multiple modes of action, which is a promising approach for treating complex diseases such as COVID-19.