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Melamine (Mel) is widespread in food and the environment. The effects of Mel on calcium oxalate (CaOx) crystallization and phase transformation were studied in aqueous solution and synthetic urine ...

The outbreak of infant milk powder poisoning in China attracted worldwide attention. The investigations found that the real culprit of this incident was melamine (Mel), which induced the formation of kidney stones. However, little is known about the formation mechanism of infant stones, not to mention the preventive and therapeutic drugs. Here, through thermodynamic and kinetic tests, simulation in vitro and animal experiments, and multidisciplinary analysis and verification, we found that the formation of this kidney stone is a rate-controlled nano-scale supramolecular layered assembly process: Mel, uric acid (UA) and a small amount of H2O combine through hydrogen bonds to form a planar network supramolecular structure; the planar structures self-assemble layer-by-layer to form ellipsoidal nanocrystals through π–π stacking interactions, van der Waals force, hydrophilic/hydrophobic interaction, etc.; the small nanocrystals gradually grow and aggregate concentrically to form ellipsoidal Mel–UA stones under the control of the matrix. Based on the above process, we screen out an effective inhibitor and eliminator for stones, potassium citrate (K3Cit), which works through both hydrogen bonding and alkalinity. This work solves the most challenging conundrum left by the Mel incident and blazes a trail for the prevention and treatment of kidney stone disease.

Ag+, extensively used in our daily life, has caused serious harm to human health and ecological environment, so highly selective detection and accurate quantification of Ag+ are critical. Herein, we report a novel water-soluble dual-element composite doped carbon quantum dots, N,S-CDs, then constructed them into fluorescent probes for Ag+ detection. Carbon source ammonium citrate (AC) could achieve nitrogen doping without additional nitrogen source, inorganic sulfur source sodium thiosulfate was used for rapid sulfur doping, the N,S-CDs emitting dazzling blue fluorescence were obtained through a rapid hydrothermal process. The synthesized N,S-CDs had an average particle size of 3.25 nm, with high quantum yield (QY = 36.8%) and excitation-independent fluorescence properties. Under optimized conditions, the fluorescent probe constructed by N,S-CDs could detect Ag+ with high sensitivity and fast response, showing a good piecewise linear relationship (0.1–700 μM). In addition, the fluorescent probe exhibited remarkable anti-interference ability and reusability, which is practical and feasible, and has broad application prospects in biological and environmental sample detection.

We herein report the first attempt to engineer an innovative bio-tissue network signal amplifier transduced by a novel natural N-doped carbon material. In order to prevent kidney uric acid (UA) stone disease in advance, based on the excretion of most UA through the kidney, as well as the high nitrogen content in animal tissues, and considering the biocompatibility, a high-N-doped carbon was firstly prepared by in situ carbonization and chemical activation method with the mouse kidney as precursor. The activated mouse kidney transformed carbon (AMKC) had a large specific surface area and network hierarchical pore structure, and played the biological transduction for signal enrichment to vastly increase sensitivity to detect UA, which may be due to the multi-circuitry performance of bio-tissue. Under the optimized conditions, AMKC as a network signal amplifier expressed a linear relationship to UA concentrations from 0.5 to 300 μM, with a high sensitivity of 0.1195 μA μM−1 and a low detection limit of 0.15 μM (3σ). Furthermore, the bio-tissue multi-circuitry signal amplifier exhibited a high selectivity for UA even with interference of other biological inorganic salts and small organic molecules, which has broad application prospects in clinical diagnosis and detection.