Nanoscaled aptasensors for multi-analyte sensing

A sensitive sandwich-type electrochemical aptasensing platform based on Ti3C2Tx/MoS2/MWCNT@rGONR composites for simultaneous detection of kanamycin and chloramphenicol in food samples

A Ti3C2Tx/MoS2/MWCNT@rGONR nanocomposite was prepared for the first time for building a sensitive electrochemical aptasening platform to simultaneously detect kanamycin (Kana) and chloramphenicol (Cap). Owing to their accordion-like structure, rich surface groups, and high charge mobility, Ti3C2Tx/MoS2/MWCNT@rGONR composites provided a spacious covalent immobilization surface and a better electrochemical aptasensing platform. The aptamers of Kana and Cap used in sensors enhance the selectivity. Furthermore, TiP, an ion exchanger, was used for loading more different metal ions functioning as labels to form a sandwich-type sensor together with Ti3C2Tx/MoS2/MWCNT@rGONR, improving the electrochemical sensitivity and obtaining a highly distinguishable signal readout. Under the optimized conditions, the sensor has good detection limits of 0.135 nmol L-1 and 0.173 nmol L-1 for Kana and Cap, respectively, at the same linearity concentration of 0.5-2500 nmol L-1. Finally, it was successfully applied for detection in milk and fish meat, and the results were compared with the standard method HPLC, indicating its great potential for food safety monitoring.

Octahedral Cu2O nanomaterials as electrochemical aptasensor for sensitive detection of tetracycline in milk

In this work, A novel label-free electrochemical biosensor based on octahedral Cu2O @ Au nanocomposites was developed for the detection of tetracycline. The gold nanoparticles (AuNPs) on the surface of Cu2O nanomaterials not only improve the electrochemical performance, but also can be used as a binding site for thiol-modified tetracycline aptamers, which can specifically bind to tetracycline. Cu2O @ Au nanocomposites provide a synergistic effect of electrochemical signal amplification and tetracycline recognition strategy. Under the optimal conditions, the proposed biosensor exhibited different electrochemical reactions for different concentrations of tetracycline, with a linear range of 1 nM-1000 μM and a detection limit of 0.16 nM. This work provides a new idea for rapid and sensitive detection of tetracycline by using a simple and economical tetracycline aptamer combined with Cu2O @ Au biosensor platform.

Aptamer Technology and Its Applications in Bone Diseases

Aptamers are single-stranded nucleic acids (DNA, short RNA, or other artificial molecules) produced by the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology, which can be tightly and specifically combined with desired targets. As a comparable alternative to antibodies, aptamers have many advantages over traditional antibodies such as a strong chemical stability and rapid bulk production. In addition, aptamers can bind targets in various ways, and are not limited like the antigen-antibody combination. Studies have shown that aptamers have tremendous potential to diagnose and treat clinical diseases. However, only a few aptamer-based drugs have been used because of limitations of the aptamers and SELEX technology. To promote the development and applications of aptamers, we present a review of the methods optimizing the SELEX technology and modifying aptamers to boost the selection success rate and improve aptamer characteristics. In addition, we review the application of aptamers to treat bone diseases.

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.

Diagnosis of acute myocardial infarction: highlighting cardiac troponins as vital biomarkers

The molecular marker, cardiac troponin (cTn) is a complex protein that is attached to tropomyosin on the actin filament. It is an essential biomolecule in terms of the calcium-mediated regulation of the contractile apparatus in myofibrils, the release of which is an indication of the dysfunction of cardiomyocytes and hence the initiation of ischemic phenomena in the heart tissue. Fast and accurate analysis of cTn may help the diagnosis and management of acute myocardial infarction (AMI), for which electrochemical biosensors and microfluidics devices can be of great benefit. This editorial aims to highlight the importance of cTn as vital biomarkers in AMI diagnosis.

Label-free electrochemical microfluidic biosensors: futuristic point-of-care analytical devices for monitoring diseases

The integration of microfluidics with electrochemical analysis has resulted in the development of single miniaturized detection systems, which allows the precise control of sample volume with multianalyte detection capability in a cost- and time-effective manner. Microfluidic electrochemical sensing devices (MESDs) can potentially serve as precise sensing and monitoring systems for the detection of molecular markers in various detrimental diseases. MESDs offer several advantages, including (i) automated sample preparation and detection, (ii) low sample and reagent requirement, (iii) detection of multianalyte in a single run, (iv) multiplex analysis in a single integrated device, and (v) portability with simplicity in application and disposability. Label-free MESDs can serve an affordable real-time detection with a simple analysis in a short processing time, providing point-of-care diagnosis/detection possibilities in precision medicine, and environmental analysis. In the current review, we elaborate on label-free microfluidic biosensors, provide comprehensive insights into electrochemical detection techniques, and discuss the principles of label-free microfluidic-based sensing approaches.

The Challenges of Developing Biosensors for Clinical Assessment: A Review

Emerging research in biosensors has attracted much attention worldwide, particularly in response to the recent pandemic outbreak of coronavirus disease 2019 (COVID-19). Nevertheless, initiating research in biosensing applied to the diagnosis of diseases is still challenging for researchers, be it in the preferences of biosensor platforms, selection of biomarkers, detection strategies, or other aspects (e.g., cutoff values) to fulfill the clinical purpose. There are two sides to the development of a diagnostic tool: the biosensor development side and the clinical side. From the development side, the research engineers seek the typical characteristics of a biosensor: sensitivity, selectivity, linearity, stability, and reproducibility. On the other side are the physicians that expect a diagnostic tool that provides fast acquisition of patient information to obtain an early diagnosis or an efficient patient stratification, which consequently allows for making assertive and efficient clinical decisions. The development of diagnostic devices always involves assay developer researchers working as pivots to bridge both sides whose role is to find detection strategies suitable to the clinical needs by understanding (1) the intended use of the technology and its basic principle and (2) the preferable type of test: qualitative or quantitative, sample matrix challenges, biomarker(s) threshold (cutoff value), and if the system requires a mono- or multiplex assay format. This review highlights the challenges for the development of biosensors for clinical assessment and its broad application in multidisciplinary fields. This review paper highlights the following biosensor technologies: magnetoresistive (MR)-based, transistor-based, quartz crystal microbalance (QCM), and optical-based biosensors. Its working mechanisms are discussed with their pros and cons. The article also gives an overview of the most critical parameters that are optimized by developing a diagnostic tool.

PD-L1 aptamer isolation via Modular-SELEX and its applications in cancer cell detection and tumor tissue section imaging

PD-1/PD-L1 is an important pathway in immunotherapy and a high PD-L1 expression level in tumor tissues is an essential prerequisite for PD-1/PD-L1 blocking-based therapy. The PD-L1 expression level in tumor tissue sections is currently detected via immunohistochemistry (IHC) using anti-PD-L1 antibodies from various resources, which has the disadvantage of inconsistent results. As synthetic affinity ligands, aptamers have good batch-to-batch consistency and have been demonstrated to have great potential for use in biomedical applications. In this study, we isolated PD-L1 aptamers using a combination method, named Modular-SELEX (systematic evolution of ligands by exponential enrichment), which includes three sequentially performed modules: the affinity module, the specificity module, and the compatibility module. Three rounds of magnetic crosslinking precipitation (MCP)-SELEX, three rounds of Capture-SELEX, and two rounds of Tissue-SELEX were respectively performed in the corresponding three modules to significantly and efficiently improve the native affinity, specificity, and compatibility of the enriched library. The isolated aptamer Clon-3 had nanomolar binding affinity, as determined via both homogeneous and PD-L1 immobilized affinity assays. Clon-3 could be used to recognize various cancer cells with distinct PD-L1 expression levels using flow cytometry. The PD-L1 expression levels in normal human tonsils (the gold standard for anti-PD-L1 antibody) and non-small cell lung cancer tissue sections stained using Cy5.5-labeled Clon-3 were also successfully imaged using a confocal microscope. The fluorescence intensities of the tissue sections were in good agreement with their actual PD-L1 expression levels as confirmed via IHC.

A simple aptamer-based colorimetric assay for rapid detection of C-reactive protein using gold nanoparticles

C-reactive protein (CRP) is a clinical biomarker for inflammatory diseases. In this work, we present a simple and fast colorimetric method for CRP detection that employs citrate-capped gold nanoparticles (AuNPs) and a CRP-binding aptamer as sensing elements. The aptamer consisted in a guanine rich single-stranded DNA (ssDNA) that adsorbs onto the surface of the AuNPs. In the presence of the CRP, the ssDNA releases from the AuNPs surface to interact preferentially with the protein to form guanine-quadruplexes. The exposure of the unprotected AuNPs to buffer salts leads to aggregation and subsequent color change from red-wine to blue-purple that was readily seen by the naked eye. The AuNPs aggregation was monitored using UV-Vis spectroscopy and the CRP concentration in the samples could be correlated with the aggregation ratio (A_670nm/A_520nm). A linear sensing range of 0.889-20.7 μg/mL was found. The detection limit (LOD) was 1.2 μg/mL which is comparable to the typical clinical cutoff concentration in high-sensitivity CRP assays (1 μg/mL) and lower than the detection limit of nephelometric methods used in clinical practice. This method can provide a fast (5 min analysis time), simple, and sensitive way for CRP detection, with negligible interference of bovine serum albumin (BSA) up to concentrations of 100 nM.

A highly sensitive and reliable detection of CA15-3 in patient plasma with electrochemical biosensor labeled with magnetic beads

An early on-time detection of breast cancer can effectively affect the outcome of the treatment. Here, we developed an ultrasensitive, simple and reliable immunosensor to detect the lowest alteration of CA 15-3, the standard biomarker of breast cancer patients. The proposed immunosensor was achieved by modification of gold electrode by streptavidin to immobilize the biotinylated anti-CA 15-3 monoclonal antibody (mAb). Bovine serum albumin was used to prevent nonspecific binding. To improve the sensitivity of modified immunosensor, the sandwich signal enhancer consisting of streptavidin-coated magnetic beads conjugated with biotinylated horseradish peroxidase (HRP) and anti-CA 15-3 biotinylated mAb was applied. The electrochemical measurements were obtained in the presence of hydroquinone as a redox agent and H₂O₂ as the activating agent of HRP. Under optimized condition and using square wave voltammetry, the lower limit of quantification was obtained as 15 × 10^-6 U/mL and the linear CA 15-3 concentration range was 50-15 × 10^-6 U/mL. While showing significant stability, the immunosensor displayed an excellent sensitivity and specificity for the detection of CA 15-3 even in the human serum as compared to the enzyme-linked immunosorbent assay (ELISA) as a gold standard method. Based on our findings, the engineered immunosensor is proposed as a robust diagnostic tool for the clinical determination of CA 15-3 and other cancer biomarkers.

Microfluidic paper-based analytical devices (µPADs) for fast and ultrasensitive sensing of biomarkers and monitoring of diseases

Through the development of analytical techniques, microscaled devices have displayed attractive advantages, including ultrasensitive detection and analysis, cost-effectiveness, portability, process integrity, multi-process functionality, and in-situ analysis. In the last decade, a new generation of analytical devices has emerged based on the cellulose materials – so-called microfluidic paper-based analytical devices (µPADs) – a field that will change the face of the diagnosis of different diseases and sensing of a wide range of biological/chemical/biochemical phenomena. The main aim of the current editorial is to highlight the importance of the µPADs in the research and development of diagnostic devices and pharmaceuticals.

Nucleic acid aptamer application in diagnosis and therapy of colorectal cancer based on cell-SELEX technology

Nucleic acid aptamers are a class of high-affinity nucleic acid ligands. They serve as “chemical antibodies” since their high affinity and specificity. Nucleic acid aptamers are generated from nucleic acid random-sequence using a systematic evolution of ligands by exponential enrichment (SELEX) technology. SELEX is a process of effectively selecting aptamers from different targets. A newly developed cell-based SELEX technique has been widely used in biomarker discovery, early diagnosis and targeted cancer therapy, particular at colorectal cancer (CRC). Combined with nanostructures, nano-aptamer-drug delivery system was constructed for drug delivery. Various nanostructures functionalized with aptamers are highly efficient and has been used in CRC therapeutic applications. In the present, we introduce a cell- SELEX technique, and summarize the potential application of aptamers as biomarkers in CRC diagnosis and therapy. And some characteristics of aptamer-targeted nanocarriers in CRC have been expatiated. The challenges and perspectives for cell-SELEX are also discussed.

Electrochemical aptasensor for multi-antibiotics detection based on endonuclease and exonuclease assisted dual recycling amplification strategy

An ultrasensitive electrochemical aptasensor for multiplex antibiotics detection based on endonuclease and exonuclease assisted dual recycling amplification strategy was proposed. Kanamycin and chloramphenicol were selected as candidates. Firstly, aptamers of the antibiotics were immobilized on bar A and then binding with their endonuclease labeled complementary DNA strands to construct enzyme-cleavage probes. Secondly, The nano zirconium-metal organic framework (NMOF) particles with 1,4-benzene-dicarboxylate (BDC) as linker was defined as UiO-66. And its updated version, hierarchically porous UiO-66 (HP-UIO-66) decorated with different electroactive materials as signal tags were synthesized. Then they were immobilized on bar B linked by two duplex DNA strands which can be specifically cleaved by corresponding enzyme-cleavage probes in bar A. Once targets were introduced into system, aptamers can capture them and then release enzyme-cleavage probes. In the presence of exonuclease-I, exonuclease assisted target recycling amplification was triggered and more enzyme-cleavage probes were released into solution. The probes can trigger endonuclease assisted recycles and repeatedly cleave their corresponding duplex DNA strands on bar B then released numerous signal tags into supernatant. Thus two recycling amplification was performed in the system. Finally, MB and Fc in the signal tags were detected by square wave voltammetry after removing bar A/B and the current intensities were correspondent with the concentration of KANA and CAP respectively. Under the optimum condition, the limits of detection for the KANA and CAP were 35fM and 21fM respectively with a wide linear range from 1 × 10^-4 to 50nM. This dual recycling amplification detection system exhibited high sensitivities and specificity. It can be easily extended to detect other targets if changing the corresponding aptamers and has potential application values for screening of multiplex antibiotics residues in food safety.

Library-based display technologies: where do we stand?

Over the past two decades, library-based display technologies have been staggeringly optimized since their appearance in order to mimic the process of natural molecular evolution. Display technologies are essential for the isolation of specific high-affinity binding molecules (proteins, polypeptides, nucleic acids and others) for diagnostic and therapeutic applications in cancer, infectious diseases, autoimmune, neurodegenerative, inflammatory pathologies etc. Applications extend to other fields such as antibody and enzyme engineering, cell-free protein synthesis and the discovery of protein-protein interactions. Phage display technology is the most established of these methods but more recent fully in vitro alternatives, such as ribosome display, mRNA display, cis-activity based (CIS) display and covalent antibody display (CAD), as well as aptamer display and in vitro compartmentalization, offer advantages over phage in library size, speed and the display of unnatural amino acids and nucleotides. Altogether, they have produced several molecules currently approved or in diverse stages of clinical or preclinical testing and have provided researchers with tools to address some of the disadvantages of peptides and nucleotides such as their low affinity, low stability, high immunogenicity and difficulty to cross membranes. In this review we assess the fundamental technological features and point out some recent advances and applications of display technologies.

High throughput sequencing analysis of RNA libraries reveals the influences of initial library and PCR methods on SELEX efficiency

The systemic evolution of ligands by exponential enrichment (SELEX) technique is a powerful and effective aptamer-selection procedure. However, modifications to the process can dramatically improve selection efficiency and aptamer performance. For example, droplet digital PCR (ddPCR) has been recently incorporated into SELEX selection protocols to putatively reduce the propagation of byproducts and avoid selection bias that result from differences in PCR efficiency of sequences within the random library. However, a detailed, parallel comparison of the efficacy of conventional solution PCR versus the ddPCR modification in the RNA aptamer-selection process is needed to understand effects on overall SELEX performance. In the present study, we took advantage of powerful high throughput sequencing technology and bioinformatics analysis coupled with SELEX (HT-SELEX) to thoroughly investigate the effects of initial library and PCR methods in the RNA aptamer identification. Our analysis revealed that distinct “biased sequences” and nucleotide composition existed in the initial, unselected libraries purchased from two different manufacturers and that the fate of the “biased sequences” was target-dependent during selection. Our comparison of solution PCR- and ddPCR-driven HT-SELEX demonstrated that PCR method affected not only the nucleotide composition of the enriched sequences, but also the overall SELEX efficiency and aptamer efficacy.

Aptamers in hematological malignancies and their potential therapeutic implications

Aptamers are short DNA/RNA oligonucleotides selected by the process called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Due to their functional similarity to monoclonal antibodies with some superior characters, such as high specificity and affinity, flexible modification and stability, and lack of toxicity and immunogenicity, they are promising alternative and complementary targeted therapy for hematologic malignancies. The trends in aptamer technology including production, selection, modifications are briefly discussed in this review. The key aspect is to illustrate aptamers against cancer cells in hematologic malignancies especially those that have entered clinical trials. We also discuss some challenges remain in the application of aptamers.

Aptamer-mediated delivery of docetaxel to prostate cancer through polymeric nanoparticles for enhancement of antitumor efficacy

Treatment of aggressive prostate cancer remains a great challenge due to inadequate drug distribution into the cancerous lesions after administration. This study aimed to develop aptamer-anchored nanoparticles (apt-NPs) for systemic delivery of docetaxel (DTX) and to evaluate the tumoricidal activity against the prostate cancer in vitro and in vivo. DTX-loaded apt-NPs (DTX-apt-NPs) were prepared by a solvent diffusion technique using functional PLGA-b-PEG and sodium oleate. DTX-apt-NPs were characterized by in vitro release, antitumor activity, cellular uptake and cytotoxic mechanisms. Pharmacokinetics and tissue distribution studies were performed in rats to investigate the biofate of DTX-apt-NPs. Finally, the in vivo antitumor efficacy was examined on the LNCaP cells xenograft tumor model. The resulting DTX-apt-NPs were 93.6nm in particle size with narrow distribution and possessed a high entrapment efficiency (97.62%) and acceptable drug loading (8.91%). DTX-apt-NPs demonstrated an enhanced in vitro antitumor effect and marked cellular uptake compared with the solution formulation or conventional nanoparticles. The intracellular trafficking of DTX-apt-NPs was shown to be an active transport process involving the clathrin-dependent endocytosis. Anti-PSMA aptamer-mediated delivery was assumed mainly responsible for the enhanced antitumor efficacy. DTX-apt-NPs that can target to PSMA-overexpressed prostate cancer provide a feasible approach for systemic delivery of DTX to the cancerous prostate to achieve a fine prognosis.

New biorecognition molecules in biosensors for the detection of toxins

Biological and synthetic recognition elements are at the heart of the majority of modern bioreceptor assays. Traditionally, enzymes and antibodies have been integrated in the biosensor designs as a popular choice for the detection of toxin molecules. But since 1970s, alternative biological and synthetic binders have been emerged as a promising alternative to conventional biorecognition elements in detection systems for laboratory and field-based applications. Recent research has witnessed immense interest in the use of recombinant enzymatic methodologies and nanozymes to circumvent the drawbacks associated with natural enzymes. In the area of antibody production, technologies based on the modification of in vivo synthesized materials and in vitro approaches with development of "display "systems have been introduced in the recent years. Subsequently, molecularly-imprinted polymers and Peptide nucleic acid (PNAs) were developed as an attractive receptor with applications in the area of sample preparation and detection systems. In this article, we discuss all alternatives to conventional biomolecules employed in the detection of various toxin molecules We review recent developments in modified enzymes, nanozymes, nanobodies, aptamers, peptides, protein scaffolds and DNazymes. With the advent of nanostructures and new interface materials, these recognition elements will be major players in future biosensor development.

Computerized techniques pave the way for drug-drug interaction prediction and interpretation

INTRODUCTION

Health care industry also patients penalized by medical errors that are inevitable but highly preventable. Vast majority of medical errors are related to adverse drug reactions, while drug-drug interactions (DDIs) are the main cause of adverse drug reactions (ADRs). DDIs and ADRs have mainly been reported by haphazard case studies. Experimental in vivo and in vitro researches also reveals DDI pairs. Laboratory and experimental researches are valuable but also expensive and in some cases researchers may suffer from limitations.

METHODS

In the current investigation, the latest published works were studied to analyze the trend and pattern of the DDI modelling and the impacts of machine learning methods. Applications of computerized techniques were also investigated for the prediction and interpretation of DDIs.

RESULTS

Computerized data-mining in pharmaceutical sciences and related databases provide new key transformative paradigms that can revolutionize the treatment of diseases and hence medical care. Given that various aspects of drug discovery and pharmacotherapy are closely related to the clinical and molecular/biological information, the scientifically sound databases (e.g., DDIs, ADRs) can be of importance for the success of pharmacotherapy modalities.

CONCLUSION

A better understanding of DDIs not only provides a robust means for designing more effective medicines but also grantees patient safety.

A Highlight of Recent Advances in Aptamer Technology and Its Application

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