Inhibition and disaggregation effect of flavonoid-derived carbonized polymer dots on protein amyloid aggregation

In this research, four water-insoluble flavonoid compounds were utilized and reacted with arginine to prepare four carbonized polymer dots with good water-solubility in a hydrothermal reactor. Structural characterization demonstrated that the prepared carbonized polymer dots were classic core-shell structure. Effect of the prepared carbonized polymer dots on protein amyloid aggregation was further investigated using hen egg white lysozyme and human lysozyme as model protein in aqueous solution. All of the prepared carbonized polymer dots could retard the amyloid aggregation of hen egg white lysozyme and human lysozyme in a dose-depended manner. All measurements displayed that the inhibition ratio of luteolin-derived carbonized polymer dots (CPDs-1) was higher than that of the other three carbonized polymer dots under the same dosage. This result may be interpreted by the highest content of phenolic hydroxyl groups on the periphery. The inhibition ratio of CPDs-1 on hen egg white lysozyme and human lysozyme reached 88 % and 83 % at the concentration of 0.5 mg/mL, respectively. CPDs-1 also could disaggregate the formed mature amyloid fibrils into short aggregates.

Facile and green synthesis of chlorophyll-derived multi-color fluorescent carbonized polymer dots and their use for sensitive detection of hemin

Due to the very important role in physiological process, a simple and sensitive hemin detection method is necessarily required. Biomass-based carbonized polymer dots (CPDs) have been widely studied especially as fluorescence probe owing to the advantages of low toxicity and the variety of fluorescence color, yet there are still challenges in developing their multi-color emission property from the same raw materials. In this work, red, white and blue emissive CPDs derived from chlorophyll have been synthesized via hydrothermal method. Then white-emitted CPDs (white-CPDs) with the Commission International d'Eclairage (CIE) coordinates at (0.34, 0.32) were used to develop a fluorescence quenched sensing system for hemin determination. There is a good linear relationship between (F0-F)/F0 and concentration of hemin in the range of 0.1-0.95 μM with a detection limit of 0.043 μM, and the quenching mechanism was considered to be caused by inner filter effect (IFE). Moreover, it has been successfully used for hemin detection in serum and also for visual determination, which indicating great potential in applications of disease diagnoses and trace identification.

Emission enhanced fluorometric biosensor by functionalized carbon polymer dots for glutathione detection in human real samples and molecular logic gate operation

Glutathione (GSH), an active peptide, plays pivotal roles in many physiological processes and detection of GSH inside of human body is of great importance for the playing of its biological effects. Here silver-phosphorus co-doped carbonized polymer dots (Ag@PCPDs) were prepared via solvothermal treatment of citric acid and phytic acid in the presence of Ag+ for GSH determination. The physicochemical and optical performance of the Ag@PCPDs were characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR), X-ray powder diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy and ultraviolet-visible (UV-Vis) spectroscopy analyses. The prepared Ag@PCPDs have outstanding water solubility with high monodispersity (7.81 ± 0.31 nm) and exhibited excellent optical properties with excitation-dependent emission, high photostability, pH, and ionic strength tolerance. An optimized excitation at 358 nm, the Ag@PCPDs showed strong photoluminescent (PL) emission at 456 nm with a PL quantum yield (QYs) of 15.6%. Furthermore, the Ag@PCPDs were used as a PL sensing platform for detection GSH in a linear range of 0-200 μM with a low limit of detection at 0.68 μM. In addition, the proposed system can construct molecular logic gates with GSH and Fe3+ ions as the chemical inputs and PL emissions as the output. And the Ag@PCPDs were successfully used for GSH determination in real samples resulting in high sensitivity and satisfactory recoveries (92.81--107.45%). More importantly, the Ag@PCPDs showed low cytotoxicity at 500 μg/mL and superior cell imaging capability in HeLa cells, which offer a new path for detection and categorization of GSH in biomedical applications.

Synthesis of high quantum yield rhenium-doped carbonized polymer dots for dual sensing of Fe3+ and Mo6+ and anti-counterfeit ink applications

The bottom-up approach serves as an efficacious and noteworthy method for the synthesis of carbonized polymer dots (CPDs). In the present investigation, rhenium-doped CPDs (Re-CPDs) were successfully synthesized via a hydrothermal technique employing citric acid, urea, and NH4ReO4. Subsequent to a comprehensive series of characterizations, Re-CPDs demonstrated an average particle size of 2.67 nm, excitation/emission maxima of 377/461 nm, and an elevated quantum yield of 45.36% at 377 nm excitation. Through the selectivity analysis involving various metal ions, Re-CPDs displayed sensitivity towards Fe3+ and Mo6+ ions, with limits of detection (LODs) of 0.02 μM and 0.48 μM, respectively. Furthermore, Re-CPDs exhibited multi-chromatic fluorescence (450-550 nm) under excitation wavelengths (375-430 nm). As a result, by amalgamating Re-CPDs with sucrose, detection patterns capable of generating multi-chromatic fluorescence at excitation wavelengths of 375, 395, and 430 nm, respectively, were successfully devised. In summary, Re-CPDs hold considerable potential as a material for the detection of Fe3+ and Mo6+ ions, as well as for anti-counterfeiting ink applications.

A novel carbonized polymer dots-based molecularly imprinted polymer with superior affinity and selectivity for oxytetracycline removal

Molecularly imprinted polymers (MIPs) synthesized from chain functional monomers are restricted by spatial extension and exhibit relatively poor affinity and selectivity; this results in unsatisfactory applications in complex media. In this study, we prepared unique spherical carbonized polymer dots (CPDs-OH) via the incomplete carbonization of 1-allyl-3-vinylimidazolium bromide and ethylene glycol, and used it as a functional monomer to prepare a newly imprinted polymer (CPDs-OH@MIP) in aqueous media. As a result, the CPDs-OH@MIP exhibited effective recognition of oxytetracycline with an impressive imprinting factor of 6.17, surpassing MIPs prepared with chain functional monomers (1-3). Furthermore, CPDs-OH@MIP exhibited excellent adsorption for oxytetracycline (278.52 mg g-1) and achieved equilibrium in 30 min, with stronger resistance to coexisting cations, anions, and humic acid. Compared to other MIPs and adsorbents, the recognition performance of CPDs-OH@MIP improved 2-4 times; this polymer could remove >92.1% of oxytetracycline in real water samples with at least 10 cycle times. CPDs-OH@MIP prepared using the special spherical monomer forms a denser structure with fewer nonimprinted regions and precisely imprinted sites, remarkably improving the affinity and selectivity of MIPs combined via hydrogen bonds and electrostatic and π-π interactions. Our proposed strategy provides an effective basis for breakthroughs in the practical application of MIPs.

A promising tool for clinical diagnostics: Dual-emissive carbonized polymer dots based cross-linking enhanced emission for sensitive detection of alkaline phosphatase and butyrylcholinesterase

Compared with single signal readout, dual-signal readout commendably corrects the impact of systematic or background error, achieving more accurate results for the diagnosis of many diseases. This work aimed to design and prepare dual-emissive fluorescent probes for the construction of ratiometric fluorescence biosensors to detect liver disease biomarkers. Sodium alginate (SA) with numerous potential sub-fluorophores and active sites and 4,4',4'',4'''-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TCPP) with macrocyclic conjugated structures were introduced to prepare the carbonized polymer dots (CPDs) with red/blue dual emission based on the cross-linking enhanced emission (CEE) effect and the luminescence of macrocyclic conjugated structures. The ratiometric fluorescence sensing systems were constructed by integrating the specific response of CPDs to Cu2+ and the affinity difference of Cu2+ to substrates or products of enzymes. The sensing systems, CPDs/Cu2+/PPi and CPDs/Cu2+/BTCh, were designed to detect liver disease biomarkers, alkaline phosphatase (ALP) and butyrylcholinesterase (BChE), respectively. The limit of detection for ALP and BChE was 0.35 U/L and 0.19 U/L, respectively. The proposed sensors were successfully applied to human serum samples from different health stages with satisfactory recoveries. These results demonstrate the successful design of a novel dual-emissive fluorescent probe and provide a feasible strategy for clinical detection.

Ratiometric visualization of lysosomal pH fluctuations during autophagy by two-photon carbonized polymer dots-based probe

Monitoring the pH variation in lysosomes is very conducive to studying the autophagy process, and fluorescent ratiometric pH nanoprobes with inherent lysosome targeting ability are highly desirable. Here, a carbonized polymer dots-based pH probe (oAB-CPDs) was developed by self-condensation of o-aminobenzaldehyde and further carbonization at low temperature. The obtained oAB-CPDs display improved performance in pH sensing, including robust photostability, intrinsic lysosome-targeting ability, self-referenced ratiometric response, desirable two-photon-sensitized fluorescence property, and high selectivity. With the suitable pKa value of 5.89, the as-prepared nanoprobe was successfully applied to monitor the variation of lysosomal pH in HeLa cells. Moreover, the occurrence that lysosomal pH decreased during both starvation-induced and rapamycin-induced autophagy was observed by using oAB-CPDs as fluorescence probe. We believe that nanoprobe oAB-CPDs can work as a useful tool for visualizing autophagy in living cells.

One-pot synthesis of nitrogen-doped carbonized polymer dots with tunable emission for multicolor light-emitting diodes

Carbonized polymer dots (CPDs) have highly potential application value in the field of optoelectronic devices due to their preferable stability, excellent optical properties and low cost. Here, the nitrogen-doped carbonized polymer dots (HNCDs) with self-quenching-resistant fluorescence were prepared via a simple solvothermal method with citric acid, urea and 2-hydroxyethyl methacrylate (HEMA) as raw materials. The structure and optical properties of the HNCDs have been explored in detail by various contrast experiments. The results show that HEMA form the poly(HEMA) to modify on the surface of carbonized core, which can overcome the quenching effect of carbonized core. The nitrogen doping is crucial for the red shift emission of solid-state HNCDs. Furthermore, the HNCDs exhibit concentration-dependent emission and excellent compatibility with silicone sol, which lead to their emission red shifted from blue to red with increasing concentration. The HNCDs were further applied to construct the light-emitting diodes (LEDs), and the multicolor LEDs ranging from blue to red can be prepared by simply varying the type of chips and adjusting the concentration of HNCDs in encapsulating material.

Wet-spinning fluorescent alginate fibres achieved by doping PEI modified CPDs for multiple anti-counterfeiting

Carbonized polymer dots (CPDs) with satisfactory excitation-dependent-emission and biocompatibility had great potential in anti-counterfeiting fibres field. However, it was difficult for CPDs to combined into the fibres due to the unstable interaction between CPDs and spinnable polymer matrix. Polyethyleneimine (PEI) was used to modify CPDs (namely PEI-CPDs) for achieving stable interactions with sodium alginate (SA) by a simple method, which including the physical interaction between the amino groups of PEI-CPDs and carboxyl groups of SA and the chain entanglement between two types of polymer chains. Then alginate fibres based on PEI-CPDs (PEI-CPDs/CaALG fibres) were successfully prepared by wet-spinning for the first time with less loss of PEI-CPDs. The high mechanical strength, excellent thermal stability and good biocompatibility achieved by PEI-CPDs/CaALG fibres. Furthermore, the fibres exhibited the excitation-dependent-emission property. Anti-counterfeiting of the fibres was conducted on both textile and papers, which showed higher security than the existing anti-counterfeiting fibres.

Construction of a Turn-off-on Fluorescent System Based On Aggregation Induced Emission of Acetaldehyde Using Carbonized Polymer dots and Tb3

It was the first time to report the aggregation induced emission (AIE) of acetaldehyde (AA) on the surface of carbonized polymer dots (CPDs) with the auxiliary of Tb³⁺. Based on the AIE of AA, a turn-off-on fluorescence method was established for AA detection using the porous CPDs-Tb³⁺ system. The one-pot hydrothermal method was used to obtain CPDs, using milk and polyethyleneimine (PEI) as precursors. In the presence of Tb³⁺, CPDs aggregated immediately and even forming precipitate, and the fluorescence intensity decreased obviously. AA can effectively embed on the surface of CPDs-Tb³⁺ due to the porous structure. AA displayed obviously blue fluorescence with excitation wavelength at 370 nm (emission peak at 460 nm), while there was no fluorescence peak when excited at 460 nm. In the CPDs-Tb³⁺ solution, AA exhibits obvious fluorescence enhancement effect (λ_ex 460 nm, λ_em 545 nm). And then, AA can be determined by the turn-off-on system based on the linear relationship between fluorescence enhancement and the concentration of AA ranging from 0.04 mM to 42.48 mM. The limit of detection (LOD) was 0.02 mM. The turn-off-on system was successfully applied to determine AA in wine samples. The strategy may be exploited to monitor AA in more drinking or foodstuff samples.

Smartphone-assisted ratiometric fluorescence sensing platform and logical device based on polydopamine nanoparticles and carbonized polymer dots for visual and point-of-care testing of glutathione

As a crucial biothiol, glutathione (GSH) plays a key role in the organisms. Monitoring GSH level is of great significance for disease diagnosis and biomedical research. In this work, polydopamine (PDA) nanoparticles-red fluorescent carbonized polymer dots (r-CPDs) based ratiometric fluorescence sensing platform was constructed and employed for GSH assay. Dopamine (DA) could be oxidized by cobalt oxyhydroxide (CoOOH) nanosheets and further polymerized into PDA nanoparticles with green fluorescence. However, in the presence of GSH, CoOOH nanosheets were reduced and decomposed, which prevented the production of PDA nanoparticles. In the sensing system, green-emitting PDA nanoparticles were employed as a response unit and r-CPDs were used as an internal reference unit. With the addition of GSH, the green fluorescence of PDA nanoparticles decreased as well as the red fluorescence of system remained relatively stable. Importantly, a distinct fluorescence color evolution from green to red was presented with a serious of GSH concentrations. Based on this, a portable smartphone-assisted ratiometric chromaticity analytical method was developed to achieve the on-site visual detection of GSH. Both the established ratiometric fluorescence and ratiometric chromaticity sensing methods for GSH assay have the merits of wide linear range, high sensitivity and excellent accuracy, which are suitable for the determination of GSH in human serum and exhibit great application potential in rapid and accurate monitoring of the GSH levels in clinical. Moreover, an ingenious logical device reflecting GSH levels was designed based on the two different fluorescence signals, which provided a new strategy for the intelligent online detection of GSH in complex biological matrices.

Carbonized polymer dots activated hierarchical tungsten oxide for efficient and stable triethylamine sensor

Hierarchical metal oxide semiconductors present great potential in detecting toxic and hazardous gases with special emphasis on the regulation of their structures and compositions to advance sensor performance. Herein, marine polysaccharide derived carbonized polymer dots (CPDs) are presented to activate hierarchical tungsten oxide (WO₃) as efficient and stable triethylamine sensor. Owing to the promoted receptor and transducer function of the oxide/polymer/carbon heterostructure, the CPDs/WO₃ sensor exhibits extraordinary sensing characteristics for triethylamine detection, including higher response (4.3 times), faster response/recovery (4.3 times/2.1 times), lower operating temperature (30 °C) and lower detection limit (2.4 times) as compared with hierarchical WO₃ sensor, which are also superior to most of the previous reports related to triethylamine detection. Importantly, the adsorption-desorption kinetic of WO₃ is found to be enhanced by 67 times after introducing CPDs, mainly derived from abundant slit-like channels for gas diffuse, desirable defect feature as reactive sites, and favorable 0D-2D interface for charge transfer and transport. This work not only establishes an alternative strategy for promoting metal oxide semiconductor gas sensors but also provides a fundamental understanding of CPDs in gas-sensing field.

Sulfuric Acid Assisted Preparation of Red-Emitting Carbonized Polymer Dots and the Application of Bio-Imaging

Red-emitting carbonized polymer dots (CPDs) was prepared from p-phenylenediamine (p-PD) aqueous solution with the assistance of sulfuric acid (H₂SO₄), and the optical properties and bio-imaging application were studied in this paper. Compared with other strong acids-assisted systems, SA-CPDs (prepared from H₂SO₄-assisted system, average diameter is ~ 5 nm) is the brightest. The photoluminescence Quantum Yields (QYs) is 21.4% (in water), and the product yield is 16.5%. SA-CPDs aqueous solution emits at 600 nm when excited by the light from 300 to 580 nm. The emission wavelength is independent on the excitation wavelength. Formation energies of CPDs in two ways were calculated to show that longitudinal growth (forming polymers) is difficult, and the transverse growth (forming CPDs) is easy. In addition, the two-photon photoluminescence properties (emitting at 602 nm when excited by 850 nm femtosecond pulse laser) of SA-CPDs were also utilized in the experiments for HeLa cells staining and shown to have potential applications in bio-imaging.