Aptamer-functionalised magnetic particles for highly selective detection of urinary albumin in clinical samples of diabetic nephropathy and other kidney tract disease

Cell Membrane-Anchored AND Logic Gate Aptasensor for Tumor Cell-Specific Imaging with Improved Accuracy

Accurate and rapid imaging of tumor cells is of vital importance for early cancer diagnosis and intervention. Aptamer-based fluorescence sensors have become a potent instrument for bioimaging, while false positives and on-target off-tumors linked to single-biomarker aptasensors compromise the specificity and sensitivity of cancer imaging. In this paper, we describe a sequential response aptasensor for precise cancer cell identification that is based on a DNA "AND" logic gate. Specifically, the sensor consists of three single-stranded DNA, including the P-strand that can sensitively respond to an acid environment, the L-strand containing the ATP aptamer sequence, and the R-strand for target cell anchoring. These DNA strands hybridize with one another to create a Y-shaped structure (named Y-ALGN). The aptamer in the R-strand is utilized to anchor the sensor to the target cell membrane primarily. Responding to the extracellular acidic environment of the tumor (input 1), the I-motif sequence forms a tetramer structure so that the P-strand is released from the Y-shaped structure and exposes the ATP binding sites in the L-strand. Extracellular ATP, as input 2, continuously operates the DNA aptasensor to complete the logic computation. Upon the sequential response of both protons and ATP molecules, the aptasensor is activated with restored fluorescence on a particular cancer cell membrane. Benefiting from the precise computation capacity of the "AND" logic gate, the Y-ALGN aptasensor can distinguish between MCF-7 cells and normal cells with high accuracy. As a simple and dual-stimuli-responsive strategy, this nanodevice would offer a fresh approach for accurately diagnosing tumor cells.

Simultaneous electrochemical detection of glycated and human serum albumin for diabetes management

Developing highly selective and sensitive biosensors for diabetes management blood glucose monitoring is essential to reduce the health risks associated with diabetes. Assessing the glycation (GA) of human serum albumin (HSA) serves as an indicator for medium-term glycemic control, making it suitable for assessing the efficacy of blood glucose management protocols. However, most biosensors are not capable of simultaneous detection of the relative fraction of GA to HSA in a clinically relevant range. Here, we report an effective miniaturised biosensor architecture for simultaneous electrochemical detection of HSA and GA across relevant concentration ranges. We immobilise DNA aptamers specific for the detection of HSA and GA on gold nanoislands (Au NIs) decorated screen-printed carbon electrodes (SPCEs), and effectively passivate the residual surface sites. We achieve a dynamic detection range between 20 and 60 mg/mL for HSA and 1-40 mg/mL for GA in buffer solutions. The analytical utility of our HSA and GA biosensor architectures are validated in mice serum indicating immediate potential for clinical applications. Since HSA and GA have similar structures, we extensively assess our sensor specificity, observing high selectivity of the HSA and GA sensors against each other and other commonly present interfering molecules in blood such as glucose, glycine, ampicillin, and insulin. Additionally, we determine the glycation ratio, which is a crucial metric for assessing blood glucose management efficacy, in an extensive range representing healthy and poor blood glucose management profiles. These findings provide strong evidence for the clinical potential of our biosensor architecture for point-of-care and self-assessment of diabetes management protocols.

Nucleic Acid Aptamer-Based Biosensors: A Review

Aptamers, short strands of either DNA, RNA, or peptides, known for their exceptional specificity and high binding affinity to target molecules, are providing significant advancements in the field of health. When seamlessly integrated into biosensor platforms, aptamers give rise to aptasensors, unlocking a new dimension in point-of-care diagnostics with rapid response times and remarkable versatility. As such, this review aims to present an overview of the distinct advantages conferred by aptamers over traditional antibodies as the molecular recognition element in biosensors. Additionally, it delves into the realm of specific aptamers made for the detection of biomarkers associated with infectious diseases, cancer, cardiovascular diseases, and metabolomic and neurological disorders. The review further elucidates the varying binding assays and transducer techniques that support the development of aptasensors. Ultimately, this review discusses the current state of point-of-care diagnostics facilitated by aptasensors and underscores the immense potential of these technologies in advancing the landscape of healthcare delivery.

Target amplification-free detection of urinary microRNA for diabetic nephropathy diagnosis with electrocatalytic reaction

Diabetic nephropathy (DN) is a serious diabetic complication, usually developed from type II diabetes mellitus (T2DM) and known as type II DN (T2DN). New emerging biomarkers for T2DN are microRNAs (miRNAs) which have been studied for the noninvasive early-stage detection of the disease. In this work, a nucleic acid amplification-free miRNA-124 sensor based on target-induced strand displacement on magnetic beads, and by using methylene blue-loaded silica particles as a label was developed. Measurement methods can be either visual observation, spectrophotometry, or electrochemistry. After incubation and separation of the magnetic particles, a blue-violet solution (564 nm) appeared, depending on the concentration of miRNA displaced. For electrochemical detection, methylene blue on the silica served as a redox mediator for the coupled reaction with ferricyanide in the solution phase. At the electrode surface, ferricyanide was re-reduced to ferrocyanide, and was thus available for further reaction with methylene blue, forming an amplification cycle. After optimization, the total assay time was 60 min, and limits of detection were 1 pM, 6 fM, and 0.65 fM, by the naked eye, spectrophotometry and electrochemistry, respectively. The miRNAs in 42 suspected urine samples from patients suffering from either diabetic nephropathy, diabetes mellitus, or chronic kidney disease were validated by comparing with the droplet digital polymerase chain reaction (ddPCR).

Voltammetric biosensor for coronavirus spike protein using magnetic bead and screen-printed electrode for point-of-care diagnostics

The rapid spread of the novel human coronavirus 2019 (COVID-19) and its morbidity have created an urgent need for rapid and sensitive diagnostics. The real-time polymerase chain reaction is the gold standard for detecting the coronavirus in various types of biological specimens. However, this technique is time consuming, labor intensive, and expensive. Screen-printed electrodes (SPEs) can be used as point-of-care devices because of their low cost, sensitivity, selectivity, and ability to be miniaturized. The ability to detect the spike protein of COVID-19 in serum, urine, and saliva was developed using SPE aided by magnetic beads (MBs) and a portable potentiostat. The antibody-peroxidase-loaded MBs were the captured and catalytic units for the electrochemical assays. The MBs enable simple washing and homogenous deposition on the working electrode using a magnet. The assembly of the immunological MBs and the electrochemical system increases the measuring sensitivity and speed. The physical and electrochemical properties of the layer-by-layer modified MBs were systematically characterized. The performance of these immunosensors was evaluated using spike protein in the range 3.12-200 ng mL-1. We achieved a limit of detection of 0.20, 0.31, and 0.54 ng mL-1 in human saliva, urine, and serum, respectively. A facile electrochemical method to detect COVID-19 spike protein was developed for quick point-of-care testing.

Nucleic Acid Nanotechnology for Diagnostics and Therapeutics in Acute Kidney Injury

Acute kidney injury (AKI) has impacted a heavy burden on global healthcare system with a high morbidity and mortality in both hospitalized and critically ill patients. However, there are still some shortcomings in clinical approaches for the disease to date, appealing for an earlier recognition and specific intervention to improve long-term outcomes. In the past decades, owing to the predictable base-pairing rule and highly modifiable characteristics, nucleic acids have already become significant biomaterials for nanostructure and nanodevice fabrication, which is known as nucleic acid nanotechnology. In particular, its excellent programmability and biocompatibility have further promoted its intersection with medical challenges. Lately, there have been an influx of research connecting nucleic acid nanotechnology with the clinical needs for renal diseases, especially AKI. In this review, we begin with the diagnostics of AKI based on nucleic acid nanotechnology with a highlight on aptamer- and probe-functionalized detection. Then, recently developed nanoscale nucleic acid therapeutics towards AKI will be fully elucidated. Furthermore, the strengths and limitations will be summarized, envisioning a wiser and wider application of nucleic acid nanotechnology in the future of AKI.