Cu-NC single-atom nanozymes with peroxidase-like activity for colorimetric detection of d-penicillamine

Most conventional nanozymes have poor specificity and low activity, and designing high-performance nanozymes remains a challenge. In contrast, single-atom nanozymes have high atom utilization and high reactivity. Here, we prepared Cu single-atom nanozymes (Cu-NC) with excellent peroxidase-like activity by high-temperature pyrolysis using Cu as a transition metal source. The introduction of Cu formed the Cu-Nx active site, which accelerated charge transfer between the reactants and the active site and was the key for improving the activity. With Cu-NC as a catalyst, H2O2 rapidly oxidized 3,3',5,5'-tetramethylbenzidine (TMB) to oxTMB, and the solution turned blue with strong absorption at 652 nm. Because d-penicillamine (D-PA) can reduce oxTMB or react with reactive oxygen species radicals to inhibit the color reaction, we built a colorimetric sensing platform around Cu-NC for the determination of D-PA and successfully used it for the determination of D-PA in urine samples. This work provides new ideas for the design of high-performance nanozymes and the detection of D-PA in real environments.

Plasmonic nanosensors for pharmaceutical and biomedical analysis

The detection and identification of clinical biomarkers with related sensitivity have become a source of considerable concern for biomedical analysis. There have been increasing efforts toward the development of single-molecule analytical platforms to overcome this concern. The latest developments in plasmonic nanomaterials include fascinating advances in energy, catalyst chemistry, optics, biotechnology, and medicine. Nanomaterials can be successfully applied to biomolecule and drug detection in plasmonic nanosensors for pharmaceutical and biomedical analysis. Plasmonic-based sensing technology exhibits high sensitivity and selectivity depending on surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) phenomena. In this critical paper, we offer an overview of the methodology of the SPR, LSPR, surface-enhanced Raman scattering (SERS), surface-enhanced infrared absorption (SEIRA), surface-enhanced fluorescence (SEF), and plasmonic nanoplatforms advanced for pharmaceutical and biomedical applications. First of all, we present here a brief discussion of the above trends. We have devoted the last section to the explanation of SPR, LSPR, SERS, SEIRA, and SEF platforms, which have found a wide range of applications, and reviewed recent advances for biomedical and pharmaceutical analysis.

Biodistribution and toxicity of antimicrobial ionic silver (Ag+) and silver nanoparticle (AgNP+) species after oral exposure, in Sprague-Dawley rats

Although antimicrobial nanosilver finds numerous applications in the health and food industries, the in vivo toxicity of positively charged silver nanoparticles (AgNPs⁺) and relevant controls are largely unexplored. This study investigates the relationship between the biodistribution and toxicity of the well-known cetyltrimethylammonium bromide (CTAB)-capped AgNPs⁺ in 6-weeks old female Sprague-Dawley rats, at sublethal doses. Amounts comparative to those leaked from food products or considered for animal feed were administered through daily water intake, for an 18-day period: AgNPs⁺ (40 μg mL^-1), Ag⁺ (40 μg mL^-1), antimicrobial CTAB⁺ (24 μg mL^-1) and tap water. All exposures except for the water control had adverse effects on the health and systemic functions of rats (e.g., lethargy, hepatomegaly, splenomegaly, impediment of bone development, and/or heightened immune response). Although the total Ag accumulation in tissues (1.4-1.6 μg of Ag/g of liver, spleen, jejunum, and brain) was comparable for the two Ag species, AgNPs⁺ were generally more toxic than Ag⁺, particularly in spleen (0.8 μg Ag/g). Significantly reduced euthanasia time, alopecia, inflammatory responses in spleen, fragile veins, and enhanced lymphocytosis were observed only for AgNPs⁺. Overall, this study raises health concerns about the ingestion of capped-AgNPs⁺ or Ag⁺ by first-hand consumers and industry workers.

A graphene quantum dots-Pb2+ based fluorescent switch for selective and sensitive determination of D-penicillamine

Taking consideration of metal-induced fluorescence quenching and excellent coordination effect of D-penicillamine (D-PA), a graphene quantum dots (GQDs)-based fluorescent switch for D-PA detection was designed and established firstly with the help of lead ions. GQDs obtained from citric acids made them rich in carboxyl and hydroxyl groups, giving GQDs the ability to combine with lead ions. As anticipated, the fluorescence intensity was quenched by Pb²⁺ through electron transfer process. Further, the addition of D-PA effectively recovered the fluorescence due to the departure of Pb²⁺ from GQDs aroused by the strong coordination between D-PA and Pb²⁺. Thus, a fluorescent switch was activated for D-PA detection. The fluorescence recovery efficiencies were found to be proportional to the concentration of D-PA in the range of 0.6-50 μmol L^-1 and the detection limit was 0.47 μmol L^-1. The real sample detection was performed in human urea sample and satisfactory recoveries of 96.84%-102.13% were obtained. The GQDs-Pb²⁺ based fluorescent switch sensing method was firstly established with low detection limit and wide linear range, making it a supplement and improvement for D-PA detection.

Modulating the mixed micellization of CTAB and an ionic liquid 1-hexadecyl-3-methylimidazollium bromide via varying physical states of ionic liquid

The physical nature of [C₁₆mim][Br] as monomers/micelles led to different IL–CTAB mixed self-assembled structures.