Immunosorbent assay based on upconversion nanoparticles controllable assembly for simultaneous detection of three antibiotics

Bioconjugates of photon-upconversion nanoparticles with antibodies for the detection of prostate-specific antigen and p53 in heterogeneous and homogeneous immunoassays

Sensitive immunoassays for the detection of tumor biomarkers play an important role in the early diagnosis and therapy of cancer. Using luminescent nanomaterials as labels can significantly improve immunoassay performance, especially in terms of sensitivity. Lanthanide-doped photon-upconversion nanoparticles (UCNPs) are nanocrystals capable of converting near-infrared radiation into visible light, and their emission spectra can be tuned by altering the dopant ions. In this study, the bioconjugation between UCNPs and biomolecules was optimized, and different conjugates of Er- and Tm-doped UCNPs (NaYF4:Yb3+,Er3+ and NaYF4:Yb3+,Tm3+) were prepared for detecting prostate-specific antigen (PSA) and tumor protein p53, comparing heterogeneous and homogeneous assay formats. The heterogeneous sandwich immunoassay achieved detection limits of 1.3 pg mL-1 for PSA and 330 pg mL-1 for p53. The homogeneous immunoassays were based on massively parallel spectroscopy (MPS), a novel artificial intelligence-aided single-molecule approach, utilizing conjugates of two different monoclonal antibodies with Er- and Tm-doped UCNPs, respectively. The conjugates provide distinct emission spectra, with only sandwich immunocomplexes of analytes and both types of labels showing signals at the same location. MPS was suitable for observing the immunocomplexes in an aqueous dispersion using only a small sample volume. This innovative method achieved detection limits of 8.2 ng mL-1 and 390 pg mL-1 for PSA and p53, respectively. MPS eliminates the need for time-consuming washing steps required in heterogeneous immunoassays and is amenable to high-throughput applications.

Integration of ratiometric, ultrafast, sensitive detection as well as rapid and efficient removal of tetracycline based on a novel Zn (II) functionalized magnetic covalent organic framework

BACKGROUND

Based on the low volatility and refractory nature of Tetracycline (TC), excessive use leads to its continuous accumulation in water environments, posing serious risks to the ecological environment and human health. Although a very limited number of nanomaterials capable of simultaneously detecting and removing TC have been fabricated, they generally exist issues associated with a single detection signal ("on" or "off") or low adsorption rates with low adsorption capacities. As a result, it is crucial to develop a reliable technique to achieve ratiometric detection as well as rapid and efficient removal of TC.

RESULTS

Herein, a novel Zn (II) Functionalized magnetic covalent organic framework (Fe3O4@COF@Zn) was created. As the role of a fluorescent probe, it had excellent characteristics of ratiometric (F529/F436), ultrafast response (1 min), and ultra-low detection limit (16 nM). As the role of an adsorbent, it demonstrated a high capacity of adsorption (414.94 mg/g) in the pH-neutral range, fast kinetics (10 min), desirable regeneration capability, and convenient magnetic separation. By theoretical and experimental analysis, the detection and adsorption mechanism for TC was systematically revealed. Moreover, as an attempt, Fe3O4@COF@Zn showed it potential for crop remediation by adsorbing TC-contaminated water.

SIGNIFICANCE

This work demonstrates the exceptional performance of Zn-functionalized fluorescent COF for ratiometric, ultrafast, sensitive detection as well as rapid and efficient removal of TC, thereby illustrating its significant potential for the rapid monitoring and treatment of TC contamination.

Integrating Metal-Organic Framework Hybrid into Nucleic Acid-Based Hydrogel for Highly Selective Recognition and Sensitive Detection of Sarafloxacin

Metal-organic framework-based hybrids (MOFzyme) have promising applications in colorimetric aptasensors due to their highly efficient and stable catalytic activity. However, their efficient application in biosensors remains a challenging issue due to the limited reaction site and amorphous structure. Herein, we encapsulated catalase inside MOF cavities to prepare an MOFzyme with many functional groups on its surface, and the functional groups were utilized for the subsequent integration of MOFzyme into the hyaluronic acid-DNA hydrogel. Moreover, the accurate and flexible synthesis unit of the hydrogel enabled the prepared DNA hydrogel to adjust the shape to suit and encapsulate MOFzyme. Subsequently, a novel colorimetric sensing strategy for detecting Sarafloxacin (Sar) was developed based on the excellent catalytic ability mediated by MOFzyme and the stimulus responsiveness of the DNA hydrogel. In addition, an evolved aptamer with a higher affinity for Sar was obtained via a semirational design strategy and elaborately designed into a synthetic unit of DNA hydrogel, significantly improving the response sensitivity and specificity of the aptasensor. The constructed aptasensor exhibited a wide linear detection range of 0.003 and 200 ng/mL with a low detection limit of 2.06 pg/mL. Above all, this work provides a novel and sensitive way to determine hazardous substances in food and environments.

Magnetic nanoparticle modified moss Biochar: A novel solution for effective removal of enrofloxacin from aquaculture water

The presence of residual antibiotics in water constitutes a potential threat to aquatic environments. Therefore, designing environmentally friendly and efficient biochar adsorbents is crucial. Aquaculture by-product moss (bryophyte) was transformed into biochar, which can eliminate antibiotics from wastewater through adsorption. This study successfully fabricated moss biochar (BC) and magnetically modified moss biochar (MBC), and explored their adsorption performance for enrofloxacin (ENR). Characterization analyses revealed that the specific surface area, total pore volume, and the quantity of functional groups of the MBC were significantly larger than those of the BC. The Langmuir isotherm model suggests that the maximum adsorption capacities of BC and MBC for ENR are 7.24 mg g⁻1 and 11.62 mg g⁻1. The adsorption process conforms to a pseudo-second-order kinetic model. Studies carried out at different temperatures disclose the spontaneous and endothermic thermodynamic characteristics of the system. Under neutral conditions, the adsorption efficiency attains its peak. The existence of various coexisting ions in water exerts a negligible influence on the adsorption process; furthermore, when the concentration of humic acid (HA) ranges from 0 to 20 mg/L, the removal rate remains above 90%. In actual water samples, the antibiotic removal rate can be as high as 96.84%. After three cycles of reuse, the structure of MBC remains unchanged while maintaining a high removal efficiency. The primary mechanisms for antibiotic adsorption by MBC involve electrostatic interactions, hydrophobic interactions, pore-filling effects, hydrogen bonding, and π-π interactions. This reusable magnetic moss biochar provides a promising research direction for effectively eliminating antibiotics from water sources.

Detection methods for antibiotics in wastewater: a review

Antibiotics are widely used as fungicides because of their antibacterial and bactericidal effects. However, it is necessary to control their dosage. If the amount of antbiotics is too much, it cannot be completely metabolized and absorbed, will pollute the environment, and have a great impact on human health. Many antibiotics usually left in factory or aquaculture wastewater pollute the environment, so it is vital to detect the content of antibiotics in wastewater. This article summarizes several common methods of antibiotic detection and pretreatment steps. The detection methods of antibiotics in wastewater mainly include immunoassay, instrumental analysis method, and sensor. Studies have shown that immunoassay can detect deficient concentrations of antibiotics, but it is affected by external factors leading to errors. The detection speed of the instrumental analysis method is fast, but the repeatability is poor, the price is high, and the operation is complicated. The sensor is a method that is currently increasingly studied, including electrochemical sensors, optical sensors, biosensors, photoelectrochemical sensors, and surface plasmon resonance sensors. It has the advantages of fast detection speed, high accuracy, and strong sensitivity. However, the reproducibility and stability of the sensor are poor. At present, there is no method that can comprehensively integrate the advantages. This paper aims to review the enrichment and detection methods of antibiotics in wastewater from 2020 to the present. It also aims to provide some ideas for future research directions in this field.

Isolation of aptamers with excellent cross-reactivity and specificity to sulfonamides towards a ratiometric fluorescent aptasensor for the detection of nine sulfonamides in seafood

Sulfonamides (SAs) is a class of antibiotics that extensively used for treating infectious diseases in livestock industries and aquaculture. Thus, it is urgent need to obtain the bio-receptor, which has excellent cross-reactivity and specificity to SAs, for developing high-throughput methods for the determination of multiple SAs even all commonly-used SAs, to realize the quick screening/detection of total SAs in animal-derived foods. We herein isolated several SAs-specific cross-reactive aptamers by using a library-immobilized SELEX with multi-SAs parallel selection strategy. Two of the isolated aptamers (Sul-01 and Sul-04) can specifically recognize and bind seven SAs respectively with higher binding affinity and no interference of non-sulfonamide antibiotics, and thus can be applied as bio-receptors for developing high-throughput aptasensors for the quick screening/detection of multiple SAs. By using the mixture of Sul-01 and Sul-04 as bio-receptor, a ratiometric fluorescent aptasensor was created for the quick detection of nine SAs including sulfamethoxydiazine (SMD), sulfapyridine (SPD), sulfaquinoxaline (SQ), sulfathiazole (ST), sulfamonomethoxine (SMM), sulfamerazine (SMR), sulfaguanidine (SG), sulfamethazine (SMZ) and sulfadiazine (SD) with a detection limit (LOD) of 0.10-0.50 μM, or total of above nine SAs with a LOD of 0.20 μM. The fluorescent aptasensor was successfully applied to detect each or total of SMD, SPD, SQ, ST, SMM, SMR, SG, SMZ and SD in fish samples with a recovery of 83 %-92 % and a relative standard deviation (RSD, n = 5) < 5 %. This study not only provided several promising bio-receptors for the development of diverse high-throughput aptasensors to achieve the quick screening of multiple SAs residues, but also provided a simple, stable and sensitive method for the quick screening of SMD, SPD, SQ, ST, SMM, SMR, SG, SMZ and SD in seafood.

Dual-Track Multifunctional Bimetallic Metal-Organic Frameworks for Antibiotic Enrichment and Detection

The improper use and overuse of antibiotics have led to significant burdens and detrimental effects on the environment, food supply, and human health. Herein, a magnetic solid-phase extraction program and an optical immunosensor based on bimetallic Ce/Zr-UiO 66 for the detection of antibiotics are developed. A magnetic Fe3O4@SiO2@Ce/Zr-UiO 66 metal-organic framework (MOF) is prepared to extract and enrich chloramphenicol from fish, wastewater, and urine samples, and a horseradish peroxidase (HRP)-Ce/Zr-UiO 66@bovine serum protein-chloramphenicol probe is used for the sensitive detection of chloramphenicol based on the dual-effect catalysis of Ce and HRP. In this manner, the application of Ce/Zr-UiO 66 in integrating sample pretreatment and antibiotic detection is systematically investigated and the associated mechanisms are explored. It is concluded that Ce/Zr-UiO 66 is a versatile dual-track material exhibiting high enrichment efficiency (6.37 mg g-1) and high sensitivity (limit of detection of 51.3 pg mL-1) for chloramphenicol detection and serving as a multifunctional MOF for safeguarding public health and hygiene.

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Fluorescence switch based on NIR-emitting carbon dots revealing high selectivity in the rapid response and bioimaging of oxytetracycline

The abuse of antibiotics has led to serious environmental pollution and the emergence of drug-resistant bacteria surpassing the replacement rate of antibiotics. Herein, near-infrared fluorescent carbon dots (NIR-CDs) were developed to meet the requirements for oxytetracycline (OTC) detection in food and water samples (milk, honey, and lake water) with a detection limit of 0.112 μM. These NIR-CDs, possessing excellent water-solubility, deep tissue penetration ability, and tunable optical properties, exhibit maximum emission at 790 nm (NIR-I window). Unlike traditional CDs, this novel NIR-CDs nanoprobe provides a dual response in the presence of OTC (quenching and bathochromic shifting), without obvious interference from other existing biomolecules and metal ions. Additionally, these NIR-CDs exhibit excellent photostability and multi-resistance under UV irradiation, exceptional pH stability (pH 6-12), reliable long-time exposure, and durability in ionic (NaCl) environments. Moreover, NIR-CDs and NIR-CDs@OTC are nontoxic and were successfully utilized for cell-imaging applications in normal (NIH3T3) and cancer cells (HeLa).

The development of a fluorescence/colorimetric biosensor based on the cleavage activity of CRISPR-Cas12a for the detection of non-nucleic acid targets

Nano-biosensors are of great significance for the analysis and detection of important biological targets. Surprisingly, the CRISPR-Cas12a system not only provides us with excellent gene editing capabilities, it also plays an important role in biosensing due to its high base resolution and high levels of sensitivity. However, most CRISPR-Cas12a-based sensors are limited by their recognition and output modes, are therefore only utilized for the detection of nucleic acids using fluorescence as an output signal. In the present study, we further explored the potential application of CRISPR-Cas12a and developed a CRISPR-Cas12a-based fluorescence/colorimetric biosensor (UCNPs-Cas12a/hydrogel-MOF-Cas12a) that provides an efficient targeting system for small molecules and protein targets. These two sensors yield multiple types of signal outputs by converting the target molecule into a deoxyribonucleic acid (DNA) signal input system using aptamers, amplifying the DNA signal by catalyzed hairpin assembly (CHA), and then combining CRISPR-Cas12a with various nanomaterials. UCNPs-Cas12a/hydrogel-MOF-Cas12a exhibited prominent sensitivity and stability for the detection of estradiol (E2) and prostate-specific antigen (PSA), and was successfully applied for the detection of these targets in milk and serum samples. A major advantage of the hydrogel-MOF-Cas12a system is that the signal output can be observed directly. When combined with aptamers and nanomaterials, CRISPR-Cas12a can be used to target multiple targets, with a diverse array of signal outputs. Our findings create a foundation for the development of CRISPR-Cas12a-based technologies for application in the fields of food safety, environmental monitoring, and clinical diagnosis.

CRISPR-Cas systems mediated biosensing and applications in food safety detection

Food safety, closely related to economic development of food industry and public health, has become a global concern and gained increasing attention worldwide. Effective detection technology is of great importance to guarantee food safety. Although several classical detection methods have been developed, they have some limitations in portability, selectivity, and sensitivity. The emerging CRISPR-Cas systems, uniquely integrating target recognition specificity, signal transduction, and efficient signal amplification abilities, possess superior specificity and sensitivity, showing huge potential to address aforementioned challenges and develop next-generation techniques for food safety detection. In this review, we focus on recent progress of CRISPR-Cas mediated biosensing and their applications in food safety monitoring. The properties and principles of commonly used CRISPR-Cas systems are highlighted. Notably, the frequently coupled nucleic acid amplification strategies to enhance their selectivity and sensitivity, especially isothermal amplification methods, as well as various signal output modes are also systematically summarized. Meanwhile, the application of CRISPR-Cas systems-based biosensors in food safety detection including foodborne virus, foodborne bacteria, food fraud, genetically modified organisms (GMOs), toxins, heavy metal ions, antibiotic residues, and pesticide residues is comprehensively described. Furthermore, the current challenges and future prospects in this field are tentatively discussed.

A novel terbium (III) and aptamer-based probe for label-free detection of three fluoroquinolones in honey and water samples

Fluoroquinolones, a family of synthetic broad-spectrum antibiotics, are widely used in clinical medicine, farm animals and aquaculture. Residues of fluoroquinolones in samples have attracted much attention because of growing food safety and public health concerns. Here, a novel Tb³⁺ ion-enrofloxacin aptamer coordination probe was prepared to develop a sensitive and rapid label-free fluorescence assay for specific detection three fluoroquinolones. In presence of the target, Tb³⁺ ion- enrofloxacin aptamer probe specifically bound with enrofloxacin, norfloxacin and ciprofloxacin, leading to a sharp increase in fluorescence emission of the probe. Under the optimized conditions, fluorescence increased linearly in the 1.0-100.0 ng/mL range for the three fluoroquinolones, with 0.053 ng/mL limit of detection for ciprofloxacin, 0.020 ng/mL limit of detection for norfloxacin and 0.061 ng/mL limit of detection for enrofloxacin. Satisfactory recovery (80.10-102.48%) in spiked honey and water samples were obtained for the three fluoroquinolones with relative standard deviations between 0.21% and 5.44% (n = 3).

Rapid detection of sulfonamide antibiotics residues in swine urine by surface-enhanced Raman spectroscopy

Surface enhanced Raman spectroscopy (SERS) combined with rapid pretreatment technique was used to determine sulfonamide antibiotics (sulfadiazine and sulfathiazole) residue in swine urine. Au nanoparticles (AuNPs) were synthesized as Raman enhance substrate and the extraction of swine urine was purified with primary secondary amine (PSA), octadecyl silane (C₁₈) and graphitized carbon (GCB) to eliminate the interference of the matrix and different dosages of adsorbents (PSA, C₁₈, GCB) were investigated. The results showed that the treatment with C₁₈ of 150 mg, GCB of 200 mg and PSA of 200 mg were an excellent approach for rapidly detecting sulfonamide antibiotics residue in swine urine. Combined with density functional theory calculation (DFT), Raman characteristic peaks of 819, 1102, 1173, 1588 cm^-1 and 825, 1127 cm^-1 were selected for qualitative and quantitative assessment of sulfadiazine and sulfathiazole in swine urine, respectively. Based on raman characteristic peak of 819 cm^-1, a good linear relationship between sulfadiazine concentration and Raman intensity was developed with R² = 0.9912, and based on raman characteristic peak of 825 cm^-1, a good linear relationship between sulfathiazole concentration and Raman intensity was developed with R² = 0.9941. And recoveries for five unknown concentration samples predicted were 98.47 ∼ 105.18% with relative standard deviation (RSD) of 1.53% ∼ 5.18%. This study demonstrated that SERS coupled with a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method could be employed to rapidly examine the sulfonamide antibiotics residue in swine urine towards its quality and safety monitoring.

Lateral flow immunoassay based on dual spectral-overlapped fluorescence quenching of polydopamine nanospheres for sensitive detection of sulfamethazine

Herein, we propose a lateral flow immunoassay (LFIA) based on the dual spectral-overlapped fluorescence quenching of polydopamine nanospheres (PDANs) caused by the inner filter effect to sensitively detect sulfamethazine (SMZ). The fluorescence quenching LFIA device consists of four parts: absorbent pad, polyvinyl chloride pad, sample pad, and nitrocellulose membrane. Compared with traditional quenchers such as gold nanoparticles (AuNPs) with single spectral-overlapped quenching ability, PDANs can quench the excitation light and emission light of three fluorescence donors (aggregation-induced emission fluorescent microsphere, AIEFM; fluorescent microsphere, FM; and quantum dot bead, QB). The fluorescence intensity changes (ΔF) are numerically larger for PDANs-LFIA (ΔF_AIEFM = 2315, ΔF_FM = 979, ΔF_QB = 910) than those for AuNPs-LFIA (ΔF_AIEFM = 1722, ΔF_FM = 833, ΔF_QB =;520). AIEFM-based PDANs-LFIA exhibits a large ΔF (2315) in response to the changes in the SMZ concentration, and produces a high signal-to-noise ratio. The limit of detection (LOD) and visual LOD of LFIA based on PDANs quenching AIEFM for the detection of SMZ in chicken are 0.043 and 0.5 ng/mL, respectively. The results confirm that the proposed method can be used for the detection of hazardous materials in practical applications.