Aptamer-free upconversion nanoparticle/silk biosensor system for low-cost and highly sensitive detection of antibiotic residues.

The detection of antibiotics is crucial for safeguarding the environment, ensuring food safety, and promoting human health. However, developing a rapid, convenient, low-cost, and sensitive method for antibiotic detection presents significant challenges. Herein, an aptamer-free biosensor was successfully constructed using upconversion nanoparticles (UCNPs) coated with silk fibroin (SF), based on Förster resonance energy transfer (FRET) and the charge-transfer effect, for detecting roxithromycin (RXM). A synergistic FRET efficiency was achieved by utilizing alizarin red and RXM complexes as energy acceptors, with UCNP as the energy donor, and immobilizing an ultrathin SF protein corona within 10 nm. The biosensor detects RXM in deionized water with high sensitivity primarily through monolayer adsorption, with a detection range of 1.0 nM-141.6 nM and a detection limit as low as 0.68 nM. The performance of this biosensor was compared with the ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for detecting antibiotics in river water separately and a strong correlation between the two methods was observed. The biosensor exhibited long-term stability in aqueous solutions (up to 60 d) with no attenuation of fluorescence intensity. Furthermore, the biosensor's applicability extended to the highly sensitive detection of other antibiotics, such as azithromycin. This study introduces a low-cost, eco-friendly, and highly sensitive method for antibiotic detection, with broad potential for future applications in environmental, healthcare, and food-related fields.

Green, Low-carbon Silk-based Materials in Water Treatment: Current State and Future Trends.

The improper and inadequate treatment of industrial, agricultural, and household wastewater exerts substantial pressure on the existing ecosystem and poses a serious threat to the health of both humans and animals. To address these issues, different types of materials have been employed to eradicate detrimental pollutants from wastewater and facilitate the reuse of water resources. Nevertheless, owing to the challenges associated with the degradation of these traditional materials post-use and their incompatibility with the environment, natural biopolymers have garnered considerable interest. Silk protein, as a biomacromolecule, exhibits advantageous characteristics including environmental friendliness, low carbon emissions, biodegradability, sustainability, and biocompatibility. Considering recent research findings, this comprehensive review outlines the structure and properties of silk proteins and offers a detailed overview of the manufacturing techniques employed in the production of silk-based materials (SBMs) spanning different forms. Furthermore, it conducts an in-depth analysis of the state-of-the-art SBMs for water treatment purposes, encompassing adsorption, catalysis, water disinfection, desalination, and biosensing. The review highlights the potential of SBMs in addressing the challenges of wastewater treatment and provides valuable insights into prospective avenues for further research.

Upconversion nanoparticle-based aptasensor for rapid and ultrasensitive detection of Staphylococcus aureus by low-speed centrifugation.

Opportunistic foodborne pathogens such as Staphylococcus aureus (S. aureus) can cause a wide variety of threats to public health. There is an urgent clinical need for a fast, simple, low-cost, and sensitive method. Here, we designed a fluorescence-based aptamer biosensor (aptasensor) for S. aureus detection using core-shell structured upconversion nanoparticles (CS-UCNPs) as a beacon. A S. aureus-specific aptamer was modified on the surface of CS-UCNPs for binding pathogens. The S. aureus bound to CS-UCNPs can then be isolated from the detection system by simple low-speed centrifugation. Thus, an aptasensor was successfully established for the detection of S. aureus. The fluorescence intensity of CS-UCNPs correlated with the concentration of S. aureus within the range of 6.36 × 102 to 6.36 × 108 CFU mL-1, resulting in the detected limit of S. aureus being 60 CFU mL-1. The aptasensor performed well in real food samples (milk) with a detection limit of 146 CFU mL-1 for S. aureus. Furthermore, we applied our aptasensor in chicken muscles for S. aureus detection, and compared it with the plate count gold standard method. There was no significant difference between our aptasensor and the plate count method within the detected limit, while the time for the aptasensor (0.58 h) was shorter than that of the plate count method (3-4 d). Therefore, we succeeded in the design of a simple, sensitive and fast CS-UCNPs aptasensor for S. aureus detection. This aptasensor system would have the potential for the detection of a wide range of bacterial species by switching the corresponding aptamer.

Aptamer-modified sensitive nanobiosensors for the specific detection of antibiotics.

The overuse or abuse of quinolone antibiotics such as enrofloxacin (ENR) in veterinary medicine results in the presence of their residues in food and environment. Thus, a sensitive method is needed to detect them. Herein, we demonstrate a fluorescence resonance energy transfer (FRET) based aptasensor for ENR detection, using core-shell upconversion nanoparticles (CSUNPs) as an energy donor and graphene oxide (GO) as an energy acceptor. The core-shell structure and Gd3+ doping significantly increased the fluorescence intensity of CSUNPs and the FRET efficiency. The ENR aptamer was conjugated to CSUNPs through ligand exchange, and the π-π stacking between the aptamer and GO brought the aptamer-modified CSUNPs to the surface of the GO sheets, resulting in the formation of a CSUNP-GO complex and the subsequent quenching of CSUNP fluorescence. As a result, an aptasensor was established with the fluorescence of CSUNPs correlated with the ENR concentration within the range of 0.976 ng mL-1 to 62.5 ng mL-1, allowing ENR to be detected at a limit of 0.47 ng mL-1. This method reduced the detection limit by approximately 13-fold in 2 h compared to the commercial enzyme-linked immunosorbent assay (ELISA) kit. The aptasensor could also be applied to detect ENR from commercial milk powder samples with a detection limit of 1.59 ng mL-1, which was far below the regulated maximum residue limit of ENR in milk. The aptasensor could not detect other antibiotics, suggesting its good specificity towards ENR. Our work demonstrates a highly selective, sensitive and cost-effective method for detecting antibiotic residues in veterinary medicine. Since the aptamer can be switched to one recognizing another antibiotic, the aptasensors are used as a plug-and-play platform that can detect a variety of antibiotics.