Aptamer-Based Detection of Ampicillin in Urine Samples

Nitrogen and Sulfur co-doped Carbon dots as an "on-off-on" Fluorescent Sensor for the Detection of Hg2+ and Ampicillin

Herein, a fluorescent "on-off-on" nanosensor based on N,S-CDs was developed for highly precise and sensitive recognition of Hg2+ and ampicillin (AMP). Nitrogen and sulfur co-doped carbon dots with blue fluorescence were synthesized by one-pot hydrothermal method using ammonium citrate and DL-methionine as precursors. N,S-CDs exhibited a surface abundant in -OH, -COOH, and -NH2 groups, aiding in creating non-fluorescent ground state complexes when combined with Hg2+, leading to the suppression of N,S-CDs' fluorescence. Subsequent to additional AMP application, the mixed system's fluorescence was restored. Based on this N,S-CDs sensing system, the thresholds for detection for AMP and Hg2+ were discovered to be 0.121 µM and 0.493 µM, respectively. Furthermore, this methodology proved effective in identifying AMP in real samples of tap and lake water, yielding satisfactory results. Consequently, in the area of bioanalysis in intricate environmental sample work, the sensing system showed tremendous promise.

Aptasensors: employing molecular probes for precise medical diagnostics and drug monitoring

Accurate detection and monitoring of therapeutic drug levels are vital for effective patient care and treatment management. Aptamers, composed of single-stranded DNA or RNA molecules, are integral components of biosensors designed for both qualitative and quantitative detection of biological samples. Aptasensors play crucial roles in target identification, validation, detection of drug-target interactions and screening potential of drug candidates. This review focuses on the pivotal role of aptasensors in early disease detection, particularly in identifying biomarkers associated with various diseases such as cancer, infectious diseases and cardiovascular disorders. Aptasensors have demonstrated exceptional potential in enhancing disease diagnostics and monitoring therapeutic drug levels. Aptamer-based biosensors represent a transformative technology in the field of healthcare, enabling precise diagnostics, drug monitoring and disease detection.

A CRISPR/Cas12a-based fluorescence aptasensor for the rapid and sensitive detection of ampicillin

This study introduces CRISPR/Cas-based aptasensor for the highly sensitive and specific detection of the antibiotic, ampicillin. Ampicillin (AMPI) is a commonly used antibiotic for treating pathogenic bacteria and is additionally added to livestock feed in agriculture. This study can enable early detection of antibiotic residues, prevent their accumulation in the environment, and ensure compliance with food safety regulations. Herein, the aptasensor was developed with the CRISPR/Cas system by utilizing three different ampicillin-specific aptamers, each conjugated with a biotin at the 5'-end. The ssDNA activator was bound to the aptamers through complementary base pairings. The attraction of the aptamers to the ampicillin target released the bound ssDNA, causing the activation of the CRISPR/Cas system. The DNA reporter probe, labelled with Cy3 and a quencher, turns on the fluorescence signal when cleaved by the activated Cas12a through trans-cleavage measured using a fluorescence spectrophotometer at 590 nm. The fluorescence signal was linearly proportional to the ampicillin target concentration with a 0.01 nM limit of detection and a read-out time of 30 min. This aptasensor showed high sensitivity towards ampicillin even in the presence of other antibiotics. The method was also successfully implemented for ampicillin detection in spiked food samples.

Interactions of Amino Group Functionalized Tetraphenylvinyl and DNA: A Label-Free "On-Off-On" Fluorescent Aptamer Sensor toward Ampicillin

As a type of aggregation-induced emission (AIE) fluorescent probe, tetraphenylvinyl (TPE) or its derivatives are widely used in chemical imaging, biosensing and medical diagnosis. However, most studies have focused on molecular modification and functionalization of AIE to enhance the fluorescence emission intensity. There are few studies on the interaction between aggregation-induced emission luminogens (AIEgens) and nucleic acids, which was investigated in this paper. Experimental results showed the formation of a complex of AIE/DNA, leading to the quenching of the fluorescence of AIE molecules. Fluorescent test experiments with different temperatures proved that the quenching type was static quenching. The quenching constants, binding constants and thermodynamic parameters demonstrated that electrostatic and hydrophobic interactions promoted the binding process. Then, a label-free "on-off-on" fluorescent aptamer sensor for the detection of ampicillin (AMP) was constructed based on the interaction between the AIE probe and the aptamer of AMP. Linear range of the sensor is 0.2-10 nM with a limit of detection 0.06 nM. This fluorescent sensor was applied to detect AMP in real samples.

A label-free and selective SERS-based sensor for determination of ampicillin contamination in water using a fabric gold–silver alloy substrate with a handheld Raman spectrometer

A plasmonic Au–Ag alloy fabric substrate is developed via in situ self-assembly of Au–Ag alloy NPs on muslin fabric. An appropriate molar ratio of Au and Ag and type of substrate are proved to be key factors for selective detection of ampicillin.

Selection and characterization of DNA aptamers for the rat major urinary protein 13 (MUP13) as selective biorecognition elements for sensitive detection of rat pests

Among invasive mammalian predators, rats represent a major threat, endangering ecosystem functioning worldwide. After rat-control operations, detecting their continued presence or reinvasion requires more sensitive and lower cost detection technologies. Here, we develop a new sensing paradigm by using a specific rat urine biomarker (MUP13) to unambiguously signal the presence of rats. As the first step towards a new remote surveillance technology, aptamers were selected to MUP13 using the Flu-Mag SELEX method. Six aptamer candidates were initially screened by dot blot and two of them (Apt-2.5 and Apt-1.4) exhibited high affinity and specificity. Both aptamers were further characterized by bead-based assay to confirm affinity and selectivity. The lead aptamer candidates were then applied to fluorescence anisotropy (FA) and surface plasmon resonance (SPR)-based biosensor platforms, showing dissociation constants in the nanomolar range and high specificity towards their target. The SPR biosensor had limits of detection of 13.8 and 7.5 nM for Apt-2.5 and Apt-1.4, respectively, which are more than three orders of magnitude lower than the physiological concentrations found in rat urine. Selectivity of the aptamers, when comparing with other major urinary proteins, was excellent, indicating strong efficacy in specific detection of rats. In order to validate the aptamer Apt-2.5 for use with real world samples a FA-based assay was performed on a rat urine sample. The assay showed that the aptamer could detect recombinant MUP13 spiked in filtered urine and the natural MUP13 in unfiltered urine, as a first step into translation to real world application. These are the first known assays to detect and quantify a MUP biomarker of rats.

Optical biosensors - Illuminating the path to personalized drug dosing

Optical biosensors are low-cost, sensitive and portable devices that are poised to revolutionize the medical industry. Healthcare monitoring has already been transformed by such devices, with notable recent applications including heart rate monitoring in smartwatches and COVID-19 lateral flow diagnostic test kits. The commercial success and impact of existing optical sensors has galvanized research in expanding its application in numerous disciplines. Drug detection and monitoring seeks to benefit from the fast-approaching wave of optical biosensors, with diverse applications ranging from illicit drug testing, clinical trials, monitoring in advanced drug delivery systems and personalized drug dosing. The latter has the potential to significantly improve patients' lives by minimizing toxicity and maximizing efficacy. To achieve this, the patient's serum drug levels must be frequently measured. Yet, the current method of obtaining such information, namely therapeutic drug monitoring (TDM), is not routinely practiced as it is invasive, expensive, time-consuming and skilled labor-intensive. Certainly, optical sensors possess the capabilities to challenge this convention. This review explores the current state of optical biosensors in personalized dosing with special emphasis on TDM, and provides an appraisal on recent strategies. The strengths and challenges of optical biosensors are critically evaluated, before concluding with perspectives on the future direction of these sensors.