A multicolor immunosensor for the visual detection of six sulfonamides based on manganese dioxide nanosheet-mediated etching of gold nanobipyramids.

In reality, various sulfonamides (SAs) were alternately used in animal husbandry to avoid generating drug resistance. Thus, it is crucial to develop simple and high-throughput methods for detecting multiple or groups of SAs to realize rapid screening of total SAs residues in foods. We herein developed a sensitive and efficient MnO2 nanosheets-mediated etching of gold nanobipyramids (AuNBPs), which can generate more vivid color changes, and further fabricated a high-throughput multicolor immunosensor for the visual screening/semi-quantitative detection of 6 different SAs including sulfamethazine (SMZ), sulfamethoxydiazine (SMD), sulfisomidine (SIM), sulfamerazine (SMR), sulfamonomethoxine (SMM) and sulfaquinoxaline (SQ) by using AuNBPs as signal and broad-specificity anti-SAs antibody as a bio-receptor. The immunosensor displays more vivid color changes, and has a lower visual detection limit and excellent specificity. It can be applied to detect as little as 1.0 ng/mL of SMZ, SMD, SMR and 2.0 ng/mL of SIM, SMM, SQ by bare eye observation, and 0.2 ng/mL of above 6 SAs by UV-visible spectrophotometry. The visual detection limit of the immunosensor is much lower than the maximum residue limit of total SAs (100 µg/kg) in edible tissues. The immunosensor was successfully applied to detect SMZ, SMD, SIM, SMR, SMM and SQ in milk with a recovery of 84%-106% and a RSD (n = 5) < 8%. The success of this study provided a promising assay for the on-site rapid screening of SMZ, SMD, SIM, SMR, SMM and SQ in food by bare eye observation. Importantly, the immunosensor may be expended as a general method for the visual screening/semi-quantitative detection of the group of other antibiotics by using the corresponding broad-specificity antibody as a bio-receptor.

Dual-Loading of Fe3O4 and Pd Nanoparticles on g-C3N4 Nanosheets Toward a Magnetic Nanoplatform with Enhanced Peroxidase-like Activity for Loading Various Enzymes for Visual Detection of Small Molecules.

Enzyme mimics now play a significant role in biochemistry. Especially, peroxidase mimics have been widely used for developing colorimetric sensors of blood glucose. The peroxidase mimics previously reported could not be recycled for reusing and may generate scattering to cause unwanted optical interference when it was used for fabricating colorimetric sensors. We herein prepared a broad-applicable and reusable magnetic enzyme-loading nanoplatform with enhanced peroxidase-like activity by simultaneously loading Fe3O4 nanoparticles (Fe3O4NPs) and palladium nanoparticles (PdNPs) on graphitic carbon nitride (g-C3N4) nanosheets (Fe3O4NPs/PdNPs/g-C3N4). The prepared Fe3O4NPs/PdNPs/g-C3N4 possesses stable and enhanced peroxidase-like activity and good enzyme-loading capacity and can be used to load various natural enzymes to form highly-efficient and stable double-active nanozyme for fabricating colorimetric sensors for the visual detection of small molecules. Especially, the magnetic feature facilitates the magnetic separation of Fe3O4NPs/PdNPs/g-C3N4 from sample solution, which is in favor of recycling and eliminating the optical interference caused by nanozyme in colorimetric sensors. The prepared Fe3O4NPs/PdNPs/g-C3N4 has been successfully used to load glucose oxidase (GOx) and cholesterol oxidase (Chox) to form magnetic peroxidase-GOx and peroxidase-Chox double-active nanozymes, which can be used to fabricate colorimetric methods for the detection of glucose and cholesterol, respectively, with a visual detection limit of 15 µM and a spectrometry detection limit of 1.0 µM. With the developed glucose and cholesterol detection methods, we have successfully detected glucose and cholesterol in serum with a recovery of 98-104% and a RSD (n = 5) < 5%. With high peroxidase-like activity, good stability, reusable features, and broad applicability of loading enzyme, the developed magnetic Fe3O4NPs/PdNPs/g-C3N4 provided a promising approach for fabricating cost-effective, sensitive, and simple colorimetric sensors for the visual detection of various small molecules.

A broad-applicability method for mercury speciation in various seafoods using microwave-assisted extraction and ion chromatography-inductively coupled plasma mass spectrometry.

Almost all marine organisms contain both inorganic and organic mercury, and thus it is extremely important to determine mercury species in seafood to objectively and scientifically assess the health risk posed by mercury. We herein developed a broad-applicability microwave-assisted extraction method and a robust ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) method for the speciation analysis of mercury in various seafood samples including seaweeds, fishes and shellfishes. The extraction method has broad adaptability, it can be used to simultaneously extract mercury species from various seafood samples including seaweeds, fishes and shellfishes without altering the chemical species of mercury, with an extraction efficiency >90%. Especially, the seafood extract obtained with the extraction method can be directly used for the following IC-ICP-MS determination of mercury species without additional pretreatment. The IC-ICP-MS method used low-cost cation guard columns as the separation column, and has an instrument detection limit of 0.02-0.05 ng mL-1 for Hg2+, CH3Hg+ and C2H5Hg+. The developed extraction and IC-ICP-MS methods have been successfully used to determine Hg2+, CH3Hg+ and C2H5Hg+ in various seaweeds, fishes and shellfishes without the matrix effect, with a method detection limit of 2.4-6.0 ng g-1 dried weight, a recovery of 92-105%, and a relative standard deviation (RSD, n = 5) of less than or equal to 6%. The success of this study offers a reliable and universal approach for the speciation analysis of mercury in seafood, which may provide the database for objectively assessing the health risks of mercury in seafood and ensuring the safety of consumption of seafood.

Interferon-inducible protein 205 (p205) plays a role in adipogenic differentiation of mouse adipose-derived stem cells.

The role of p205 in the regulation of cell growth and differentiation remains poorly understood. This study aimed to determine whether p205 is involved in adipogenesis of mouse adipose-derived stem cells (mASCs). p205 was largely induced in mASCs under adipogenesis in vitro. The mRNA and protein levels of p205 reached a maximum at day 4, and decreased at days 6 and 8. p205 localized almost exclusively in the nucleus of undifferentiated cells, but also translocated to the cytoplasm in intermediately and terminally differentiated cells. Although p205 suppression impaired mASC adipogenesis, its overexpression did not enhance the differentiation process. p205 co-localized with, and bound directly to, C/EBPß and C/EBPα at day 4. Knockdown of p205 lowered the amount of p205 interacting with C/EBPß or C/EBPα, further downregulating the transcription activities of C/EBPα and PPARγ. This suggests the importance of these transcription factors in the role of p205 in mASC adipogenesis.