User-friendly and ultra-stable all-inclusive gold tablets for cysteamine detection

Preparation of graphene based composites using silane and Pyracantha fortuneana and their application in Metformin adsorption from aqueous solution

Metformin, a typical pharmaceutical and personal care product (PPCPs), has a significant role in protecting brain cognitive function and delaying multiple organs aging, as well as causes seriously endocrine and reproductive interference to aquatic organisms due to drug abuse. Graphene that is of stable structure, flexible connection between carbon atoms, and the conjugated large pi bonds has been used to wastewater treatment, while Graphene-based materials used to remove PPCPs are rarely reported. Therefore, two graphene oxide (GO) based materials, including silane coupling agent modified product (CTOS-mGO) and Pyracantha fortuneana proanthocyanidin extract reduced product (PFPA-rGO), were used for metformin removal from aqueous solution as well as revealed the mechanism in this adsorption process. The results showed that metformin could be quickly and effectively removed by GO, CTOS-mGO and PFPA-rGO, of which the best material of adsorption effects was CTOS-mGO. The pseudo-second-order kinetic could effectively describe their adsorption process, and they achieved more than 80% removal rate within 15 to 20 min. Metformin adsorption by GO, CTOS-mGO and PFPA-rGO were all spontaneous and exothermic. CTOS-mGO was of the largest adsorption capacity and recycling utilization for metformin removal in comparison with GO and PFPA-rGO. The optimal adsorption temperature and pH for the GO and CTOS-mGO, PFPA-rGO adsorbents were 293 K and pH 6.0, 293 K and pH 7.0, 303 K and pH 6.0, respectively. Our results suggested that the aromatic rings and the abundant oxygen-containing functional groups distributed on the surface of the sheets endowed them with the characteristics of π-electron acceptors or donors, and metformin with dissociative properties could serve as a stabilizer for this π-π interaction. In addition, the electrostatic interaction between the positively charged metformin and the negatively charged GO and CTOS-mGO were also important contributors to the adsorption reaction. Our results emphasized that the GO based materials might be an effective method for alleviating metformin and other PPCPs pollution, which also provided a reference for environmental remediation of similar pollutants.

A dual-functional nanogold tablet as a plasmonic and nanozyme sensor for point-of-care applications

Point-of-care (POC) devices provide on-site disease diagnosis, particularly in resource-limited settings. Despite considerable progress in POC testing, the availability of commercial devices remains limited, primarily due to challenges in detection sensitivity and portability. Furthermore, advancements in existing POC devices are essential to better meet the needs of end-users. Herein, we present a colorimetric dual-functional tablet sensor using dextran-gold nanoparticles (dAuNPs) to detect and quantify uric acid and glucose levels in urine. Our tablet sensor combines the plasmonic and nanozyme properties of dAuNPs, resulting in highly sensitive detection of both biomarkers. Interestingly, we fabricated the nanogold tablet directly from the dAuNP solution without the addition of any external stabilizer or tablet-forming reagent, thus naming it a direct tablet. An enzyme-free approach was employed for uric acid detection, providing a wide detection range of 0.00187-7.8 mM and a low detection limit of 0.0037 mM, attributed to the hydrogen bonding between dextran and uric acid. On the other hand, the unique nanozyme properties of dAuNPs exhibited exclusive POx-mimetic activity for glucose detection (K m = 0.106 mM and V max = 369.72 mM min-1), with a lower detection limit of 0.625 mM. Our dual-functional tablet offers exceptional substrate selectivity for the colorimetric-chromogenic assay of both uric acid and glucose. This dual-functionality not only provides a highly sensitive, selective, and cost-effective detection strategy for resource-limited settings but also introduces a new avenue for designing customizable plasmonic-nanozyme nanogold tablet sensors as a powerful tool for rapid diagnosis.

β-Cyclodextrin Functionalized Au@Ag Core-Shell Nanoparticles: Plasmonic Sensors for Cysteamine and Efficient Nanocatalysts for Nitrobenzene-to-Aniline Conversion

We reported the gold/silver core-shell nanoparticles (Aucore@Agshell NPs) functionalized with β-cyclodextrin (β-CD) as versatile nano-agents demonstrated for human urine-based biosensing of cysteamine and catalytic conversion from nitrobenzene (NB) to aniline. First, the hybrid bimetallic nanoparticles, i.e., β-CD-Aucore@Agshell NPs, constituted a colorimetric sensing platform based on localized surface plasmons, enabling cysteamine (Cyst) to be detected in a remarkably rapid manner, i.e., within 2 min, which was greatly shortened in comparison with that of our previous report. This was due largely to use of β-CD being effectively replaceable by Cyst. The detection of Cyst was demonstrated using human urine specimens in the linear range of 25-750 nM with a limit of detection of 1.83 nM. Excellent specificity in detecting Cyst was also demonstrated against potential interfering molecules. Meanwhile, the β-CD-Aucore@Agshell NPs were demonstrated as nanocatalysts for converting NB to aniline with efficiency enhanced by more than three-fold over the pure gold nanoparticles previously reported, due to the dual functions of the structural core-shell. The demonstrated versatile features of the hybrid nanoparticles can find applications in human urine-based biosensors for Cyst detection, and in the screening of Cyst-containing drugs, while detoxicating NB for ecological protection in aqueous media.

A New and Rapid LC-MS/MS Method for the Determination of Cysteamine Plasma Levels in Cystinosis Patients

Cystinosis is a rare lysosomal storage disorder caused by autosomal recessive mutations in the CTNS gene that encodes for the cystine transporter cystinosin, which is expressed on the lysosomal membrane mediating the efflux of cystine. Cysteamine bitartrate is a cystine-depleting aminothiol agent approved for the treatment of cystinosis in children and adults. In this study, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of cysteamine levels in plasma samples. This LC-MS/MS method was validated according to the European Medicines Agency (EMA)'s guidelines for bioanalytical method validation. An ultra-performance liquid chromatograph (UPLC) coupled with a 6470 mass spectrometry system was used for cysteamine determination. Our validated method was applied to plasma samples from n = 8 cystinosis patients (median, interquartile range (IQR) = 20.5, 8.5-26.0 years). The samples were collected before cysteamine oral administration (pre-dose) and 1 h after (post-dose). Our bioanalytical method fulfilled the regulatory guidelines for method validation. The cysteamine plasma levels in pre-dose samples were 2.57 and 1.50-3.31 μM (median and IQR, respectively), whereas the post-dose samples reported a cysteamine median concentration of 28.00 μM (IQR: 17.60-36.61). Our method allows the rapid determination of cysteamine plasma levels. This method was successfully used in cystinosis patients and, therefore, could be a useful tool for the evaluation of therapy adherence and for future pharmacokinetic (PK) studies involving a higher number of subjects.

Tailoring plasmonic sensing strategies for the rapid and sensitive detection of hypochlorite in swimming water samples

A tunable plasmonic sensor has been developed by varying the dextran content in the initially synthesized dextran-gold nanoparticle (dAuNPs) solution. A colloidal nanogold solution (dAuNPs-Sol) was initially prepared using dextran and gold salt in alkaline media by a one-pot green synthetic route. The dAuNPs-Sol was combined with varying amounts of dextran (ranging from 0.01 to 30.01%) to create a tunable probe, along with different solid formats, including tablet (dAuNPs-Tab), powder (dAuNPs-Powder), and composite (dAuNPs-Comp). Both the liquid and solid phase plasmonic probes were characterized using UV-vis spectroscopy, transmission electron microscopy (TEM) dynamic light scattering (DLS), and zeta potential analysis. The impact of dextran content in the dAuNP solution is studied in terms of surface charge and hydrodynamic size. The influence of operational treatments used to achieve solid dAuNPs probes is also explored. All plasmonic probes were employed to detect a broad range of OCl¯ concentrations (ranging from µM to mM) in water through aggregation followed by calculating a lower and upper limit of detection (LLoD, ULoD) of the proposed colorimetric sensors. Results indicate that the most sensitive detection is achieved with a lower dextran content (0.01%), which exhibits an LLoD of 50 µM. The dAuNPs-Sol sensor is selective and demonstrates real-world applicability, as confirmed by interference analysis and successful testing with various water samples. Additionally, it is found that a 20 × concentration of dextran-coated gold nanoparticles could be attained without any changes in the particle morphology. This concentration is achieved through a straightforward process that does not require the use of a centrifuge machine. This finding highlights the practicality and simplicity of the method, indicating its potential for scalable and cost-effective production of concentrated dAuNPs without compromising their structural integrity.