A design of red emission CDs-based aptasensor for sensitive detection of insulin via fluorescence resonance energy transfer

Graphene oxide aptasensor droplet assay for detection of metabolites secreted by single cells applied to synthetic biology

Synthetic biology harnesses the power of natural microbes by re-engineering metabolic pathways to manufacture desired compounds. Droplet technology has emerged as a high-throughput tool to screen single cells for synthetic biology, while the challenges in sensitive flexible single-cell secretion assay for bioproduction of high-value chemicals remained. Here, a novel droplet modifiable graphene oxide (GO) aptasensor was developed, enabling sensitive flexible detection of different target compounds secreted from single cells. Fluorophore-labeled aptamers were stably anchored on GO through π-π stacking interactions to minimize the non-specific interactions for low-background detection of target compounds with high signal-to-noise ratios. The assay's versatility was exhibited by adapting aptamer sequences to measure metabolic secretions like ATP and naringenin. To show the case, engineered E. coli were constructed for the bioproduction of naringenin. The high signal-to-noise ratio assay (∼2.72) was approached to precisely measure the naringenins secreted from single E. coli in the droplets. Consequently, secretory cells (Gib) were clearly distinguished from wild-type (WT) cells, with a low overlap in cell populations (∼0%) for bioproduction.

Detection of Biomarker Using Aptasensors to Determine the Type of Diabetes

Diabetes mellitus (DM) is a metabolic disorder characterized by elevated blood glucose levels. This disease is so serious that many experts refer to it as the "silent killer". The early detection of diabetes mellitus, whether type 1, type 2 or mitochondrial, is crucial because it can improve the success of treatment and the quality of life for patients. Aptamer-based biosensor diagnosis methods have been widely developed because they have high sensitivity and selectivity in detecting biomarkers of various diseases. Aptamers are short sequences of oligonucleotides or proteins that recognize specific ligands and bind to various target molecules, ranging from small ions to large proteins. They are promising diagnostic molecules due to their high sensitivity and selectivity, ease of modification, low toxicity, and high stability. This article aims to summarize the progress of detection methods, including detection principles, sensitivity, selectivity, and the performance of detection devices, to distinguish between types of diabetes mellitus using electrochemical aptasensors with biomarkers such as glucose, insulin, HbA1c, GHSA, and ATP.

Screening of a High-Affinity Aptamer for Aflatoxin M1 and Development of Its Colorimetric Aptasensor

Aflatoxin M₁ (AFM₁), a secondary metabolite of Aspergillus spp., is highly toxic and widely present in food matrices. Therefore, the detection of AFM₁ is of great importance for the protection of food safety. In this study, a five-segment sequence was designed as the initial library. Graphene oxide-SELEX (GO-SELEX) was applied to screen AFM₁. After seven rounds of repeated screening, affinity and specificity assays showed that aptamer 9 was the best candidate for AFM₁. The dissociation constant (K_d) of aptamer 9 was 109.10 ± 6.02 nM. To verify the efficiency and sensitivity aptamer for the detection of AFM₁, a colorimetric sensor based on the aptamer was constructed. The biosensor showed good linearity in the range of AFM₁ concentration of 0.5-500.0 ng/mL with a detection limit of 0.50 ng/mL. This colorimetric method was successfully used for the detection of AFM₁ in milk powder samples. Its detection recovery was 92.8-105.2%. This study was conducted to provide a reference for the detection of AFM₁ in food.

Label-free Aptasensor for the Ultrasensitive Detection of Insulin Via a Synergistic Fluorescent Turn-on Strategy Based on G-quadruplex and AIEgens

Insulin, the only hormone regulating blood glucose level, is strongly associated with diabetes and its complications. Specific recognition and ultrasensitive detection of insulin are of clinical significance for the early diagnosis and treatment of diabetes. Inspired by aggregation-induced emission, we presented a turn-on label-free fluorescence aptasensor for insulin detection. Quaternized tetraphenylethene salt was synthesized as the fluorescence probe. Guanine-rich aptamer IGA3 was selected as recognition element. Graphene oxide was chosen as the quencher. Under optimized conditions, the fluorescence aptasensor displayed a wide linear range (1.0 pM-1.0 μM) with a low limit of detection (0.42 pM). Furthermore, the aptasensor was successfully applied to detect insulin in human serum. Spiked recoveries were obtained in the range of 96.06%-104.26%. All these results demonstrated that the proposed approach has potential application in the clinical diagnostics of diabetes.