Effectively synthesized functional Si-doped carbon dots with the applications in tyrosinase detection and lysosomal imaging

An integrated and multifunctional homemade cell sensor platform based on Si-d-CQDs and CRISPR-Cas12a for CD31 detection during endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT) plays a crucial role in the initiation and progression of atherosclerosis and various disease processes. Cluster of differentiation 31 (CD31) is a significant marker in EndMT. Detecting CD31 is essential for early-stage monitoring of EndMT and diagnosing atherosclerosis. Herein, we propose a homemade electrochemical array sensor comprising four electrodes, applied for cell cultivation, electrical stimulation, and simultaneous electrochemical detection, offering a three-in-one approach for CD31 detection during EndMT. To enhance the analytical performance of the cell sensor, indium tin oxide/chitosan-MXene/polyaniline (ITO/CS-MXene/PANI) composites were synthesized. The synthesis process involved the polymerization of PANI on the surface of the CS-MXene-modified ITO electrode, resulting in the creation of highly biocompatible active sites for cell immobilization. Si-d-CQDs@acDNA-AptCD31-Fc, with exceptional photophysical and chemical properties, was integrated into the array sensor setup, which enabled the dual-mode detection of fluorescent and electrochemical signals in cultured cells. A CRISPR-Cas12a system was employed to cleave Si-d-CQDs@acDNA-AptCD31-Fc. Subsequently, the fragmented Fc molecules were enriched via electrochemistry to further amplify the electrochemical signals. Through the unique combination of programmable Si-d-CQDs@acDNA-AptCD31-Fc, the CRISPR-Cas12a system, and voltage enrichment, a novel "signal-on-off-super on" signal amplification strategy was developed. The cell sensor exhibited a wide linear range from 1 × 101 particles mL-1 to 1 × 106 particles mL-1 (R2 = 0.9912) and a detection limit of 4 particles mL-1. The proposed strategy presents a promising approach for developing CRISPR-Cas12a-based tools for detecting various stages of EndMT and opens a new window for dual-mode analysis applications.

Rational Synthesis of Highly Fluorescent N, S Co-Doped Carbon Dots Using Biogenic Creatinine for Cu2+ Analysis in Drinking Water

Herein, highly fluorescent sulfur and nitrogen co-doped carbon dots (N, S-CDs) had been employed as a fluorescent probe to analyze Cu2+ in drinking water. The biogenic creatinine is known to form a stable complex with Cu2+; hence, it was rationally selected as a bioinspired nitrogen substrate for the first time to enhance N, S-CDs selectivity towards Cu2+. Moreover, the literature was surveyed to guide the selection of sulfur and carbon sources to optimize N, S-CDs quantum yield (QY), so thiourea and disodium edetate are co-carbonized with biogenic creatinine at 270°C for 40 min and characterized using different techniques. The resulting N, S-CDs have a homogeneous particle size distribution and high QY (60.5% ± 2.09%, n = 5). The produced N, S-CDs fluorescence intensity (FI) had been quantitatively quenched by Cu2+, achieving a detection limit reached of 0.07 μM. The developed environmentally friendly and sustainable platform, according to the results of three widely greenness assessment tools and the innovative RGB 12 model, had been successfully employed to detect Cu2+ in drinking water with excellent recovery. Finally, as this sensing platform is rapid and selective, it can be successfully employed to determine the Cu2+ in real-life applications.

MnO4--triggered wavelength-changeable and rapid-response fluorescence sensor for paper-based on-site sensing of tyrosinase activity in potato

Rapid-response in situ fluorogenic reactions in aqueous solution are important for designing sensitive and stable sensing platforms. Herein, a wavelength-changeable and rapid-response (within 5 s) fluorescence sensing platform for monitoring tyrosinase (TYR) activity is constructed. The developed assay is based on TYR catalyzing the hydroxylation of mono-phenol to o-diphenol and MnO4--triggered fluorogenic between dopamine (DA) and phenol derivatives in aqueous solution. The fluorescence wavelength can be changeable from 470 to 550 nm with strong fluorescence according to different phenol derivatives. Our proposed sensor not only exhibits a good recovery for TYR in high serum concentration (20 %), but also has been successfully applied to the screening of TYR inhibitors modeled on kojic acid. Furthermore, a paper-based wavelength-changeable fluorescence sensor was developed for on-site detection of TYR activity in potatoes with high recovery, which is consistent with our previously reported method. Consequently, the proposed sensing system has broad prospects in the practical application of TYR-associated food monitoring and clinical diagnosis.

Sugar Cane (Saccharum officinarum L.) Waste Synthesized Si,N,S-Carbon Quantum Dots as High-Performance Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

This work reports the obtention of Si,N,S-CQDs from sugar cane bagasse and their inhibitory action on the mild steel corrosion in 1 mol L-1 HCl solution. The CQDs were successfully obtained and characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, Dynamic light scattering, Raman, and UV-vis techniques, also showing endogenous self-doping. The anti-corrosive activity of CQDs was investigated by gravimetric tests, potentiodynamic polarization curves, electrochemical impedance measurements, atomic force microscopy, and scanning electron microscopy. The electrochemical results show that the CQDs present a predominant inhibitory action on the cathodic process, presenting inhibition efficiency of 82, 89, 91, and 94% for 15, 25, 50, and 100 ppm, respectively. Gravimetric tests varying temperature demonstrate that the inhibitor functions through physical adsorption and remains effective for up to 72 h, exhibiting corrosion efficiency of 80.2, 93.2, 96.3, and 97.8% at 15, 25, 50, and 100 ppm concentrations, respectively, after 72 h of immersion. Dynamic light scattering and zeta potential measurements indicate that agglomerations of CQDs play a crucial role in inhibiting corrosion. These results show an excellent alternative for using sugar cane bagasse to produce CQDs and its application as a corrosion inhibitor, valuing agricultural waste and simultaneously solving industry problems.

Effective Determination of Diosmin Using Nitrogen Doped Carbon Dots as Probe Based on Internal Filtering Effect

The establishment of a convenient and efficient testing method is crucial and needed for the monitoring of diosmin. In this study, nitrogen doped carbon dots (N-CDs) with the particle size distribution of 2.5-5.7 nm and the average diameter of 4.1 nm were successfully synthesized using a simple strategy. N-CDs exhibited excellent and stable fluorescence performance with the quantum yield of 22.33%. Correspondingly, a fluorescence analytical method was developed for diosmin determination using N-CDs as probe. UV-vis absorbance spectroscopy and the evaluation of internal filtering parameters verified that the mechanism causing the quenching of N-CDs was an internal filtering effect (IFE). The concentration of diosmin can be directly evaluated based on the quenched fluorescence intensities. After optimizing experimental conditions, it was found that the fluorescence quenching efficiency ((F0-F)/F0) of N-CDs exhibited a good linear relationship with the concentration of diosmin (CDiosmin) in the range of 3.0-50 µg/mL. The limit of detection (LOD) was 0.86 µg/mL based on 3σ/slope (n = 13). This method was successfully applied to accurately determine the content of diosmin in diosmin tablets and human plasma samples with good reproducibility. It stands out for its simplicity, speed, and acceptable determination performance.

One-pot hydrothermal synthesis of silicon, nitrogen co-doped carbon dots for enhancing enzyme activity of acid phosphatase (ACP) to dopamine and for cell imaging

Developing water-soluble nanomaterials with high photoluminescence emission and high yield for biological analysis and imaging is urgently needed. Herein, water-soluble blue emitting silicon and nitrogen co-doped carbon dots (abbreviated as Si-CDs) of a high photoluminescence quantum yield of 80 % were effectively prepared with high yield rate (59.1 %) via one-step hydrothermal treatment of N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAMO) and trans-aconitic acid. Furthermore, the Si-CDs demonstrate environmental robustness, photo-stability and biocompatibility. Given the importance of the potentially abnormal levels of acid phosphatase (ACP) in cancer diagnosis, developing a reliable and sensitive ACP measurement method is of significance for clinical research. The Si-CDs unexpectedly promote the catalytic oxidation of ACP on dopamine (DA) to polydopamine under acidic conditions through the produced reactive oxygen species (ROS). Correspondingly, a fluorescence response strategy using Si-CDs as the dual functions of probes and promoting enzyme activity of ACP on catalyzing DA was constructed to sensitively determine ACP. The quantitative analysis of ACP displayed a linear range of 0.1-60 U/L with a detection limit of 0.056 U/L. The accurate detection of ACP was successfully achieved in human serum through recovery tests. As a satisfactory fluorescent probe, Si-CDs were successfully applied to fluorescent imaging of A549 cells in cytoplasmic with long-term and safe staining. The Si-CDs have the dual properties of outstanding fluorescent probes and auxiliary oxidase activity, indicating their great potential in multifunctional applications.

Ultrasensitive detection of tyrosinase with click reaction-combined dark-field imaging platform

Tyrosinase (TYR) is an essential oxidase that is responsible for the regulation of multiple physiological processes and diseases. Achieving the trace and reliable detection of TYR in complex biological samples is of great significance for the diagnosis of TYR-related diseases, but which faces a great challenge. In this study, we developed an ingenious and powerful method for the ultrasensitive detection of TYR by click reaction-combined dark-field microscopy. This method begins with the formation of cuprous ions (Cu+) based on the reduction of copper ions (Cu2+) by ascorbic acid (AA). Subsequently, the formed Cu+ can catalyze the crosslinking between azide- and alkyne-functionalized gold nanoparticles, causing a significant red-shift in the scattering spectrum. However, AA can chelate with TYR, which inhibits the generation of Cu+ and subsequent click reaction, thus achieving TYR-controlled scattering spectral shift. The proposed sensing platform shows a good linear detection range of 0.01-0.8 U/L with a low detection limit of 0.003 U/L, which is three orders of magnitude lower than the best performance of TYR sensing probes reported to date. Most importantly, the strategy has the ability to reliably and accurately detect TYR in serum sample, suggesting its potential clinical application in diagnosing TYR-related diseases. This visual sensing platform offers promising prospects for future research in enzymatic analysis and biomedical diagnostics.