A highly sensitive and specific fluorescent probe for thrombin detection and high-throughput screening of thrombin inhibitors in complex matrices

Thrombin plays a critical role in hemostasis and hemolysis, and is a significant biomarker for blood-related diseases. Detection and inhibitors screening of thrombin are essential in medical research. In this study, we developed a fluorescent sensor based on the interaction between quantum dots (QDs) and fibrinogen (Fib) for thrombin detection and its inhibitors screening. Upon the presence of thrombin, the fibrinogen of soluble QDs-Fib were converted into insoluble fibrin precipitate, causing a change of fluorescence intensity in the supernatant. Under optimized conditions, our method exhibited an excellent linearity (R2 ≥0.99) over the range of 2∼100 U/L with a limit of detection (LOD) as low as 0.29 U/L. Moreover, we employed this method to screen for thrombin inhibitors using dabigatran as an exemplary direct thrombin inhibitor (DTI), even at concentrations as low as 1 nM. Finally, the established method was successfully used to screen thrombin inhibitors in 23 different extracts from Eupolyphaga sinensis walker. The method provided not only a sensitive, specific and high throughput assay for the detection of thrombin activity in biological samples, but also a reliable strategy for the screening of thrombin inhibitors in complex matrices.

Thermal stability, antioxidant activity and bioavailability of pea protein-naringin Pickering emulsion for enhanced delivery applications

After successfully addressing to mitigate bitterness of naringin through construction Pickering emulsion using pea protein (PP) and naringin (NG) in our previous study, we now probed thermal stability, antioxidant efficacy, and bioavailability. FTIR analysis and UV-vis spectroscopy indicated predominant interactions between PP and NG were hydrogen and hydrophobic bonds. TGA and DSC analyses demonstrated that PP-NG complexes exhibited superior heat-resistance compared to pure PP and NG. Thermal stability assessments indicated a significant retention of NG in the PP-NG Pickering emulsion than the control NG across varied temperatures (4 °C, 25 °C, 37 °C, and 65 °C). Moreover, the antioxidant activity of PP-NG emulsion was dependent on the concentration of NG, as evidenced by DPPH and ABTS free radicals scavenging abilities, ferric reducing power, and lipid peroxidation resistance. Additionally, PP-NG Pickering emulsion exhibited substantially high bioavailability (92.01 ± 3.91%). These results suggest a promising avenue for the application of NG with improved characteristics.

Different functional groups of carbon dots influence the formation of protein crowns and pepsin characteristic in vitro digestion

Application of nanomaterials (NMs) in agriculture poses an ingestion risk to humans and may affect the digestive process. Different fates of NMs with differential charges in the gastrointestinal tract should be considered. In this study, the interaction between three carbon dots (CDs) carried with different functional groups (-NH2, -OH, and -COOH) and pepsin was analyzed through an in vitro digestion model. The results showed that CDs significantly reduced pepsin activity. Among them, CDs-NH2 had the greatest effect, following by CDs-OH, and CDs-COOH. Besides, molecular docking demonstrated the specific binding site of CDs to pepsin, while the most stable binding energy (-8.10 kcal/mol) was formed between CDs-NH2 and pepsin. Further, CDs formed a nanomaterial-protein crown structure with pepsin. The present study enriches the functional group properties of CDs in the digestion and provides new ideas for the potential human health of NMs.

Molecular interactions between gelatin-derived carbon quantum dots and Apo-myoglobin: Implications for carbon nanomaterial frameworks

Carbon nanomaterials (CNMs), including carbon quantum dots (CQDs), have found widespread use in biomedical research due to their low toxicity, chemical tunability, and tailored applications. Yet, there exists a gap in our understanding of the molecular interactions between biomacromolecules and these novel carbon-centered platforms. Using gelatin-derived CQDs as a model CNM, we have examined the impact of this exemplar nanomaterial on apo-myoglobin (apo-Mb), an oxygen-storage protein. Intrinsic fluorescence measurements revealed that the CQDs induced conformational changes in the tertiary structure of native, partially unfolded, and unfolded states of apo-Mb. Titration with CQDs also resulted in significant changes in the secondary structural elements in both native (holo) and apo-Mb, as evidenced by the circular dichroism (CD) analyses. These changes suggested a transition from isolated helices to coiled-coils during the loss of the helical structure of the apo-protein. Infra-red spectroscopic data further underscored the interactions between the CQDs and the amide backbone of apo-myoglobin. Importantly, the CQDs-driven structural perturbations resulted in compromised heme binding to apo-myoglobin and, therefore, potentially can attenuate oxygen storage and diffusion. However, a cytotoxicity assay demonstrated the continued viability of neuroblastoma cells exposed to these carbon nanomaterials. These results, for the first time, provide a molecular roadmap of the interplay between carbon-based nanomaterial frameworks and biomacromolecules.

An overview on animal/human biomass-derived carbon dots for optical sensing and bioimaging applications

Over the past decade, carbon dots (CDs) have emerged as some of the extremely popular carbon nanostructures for diverse applications. The advantages of sustainable CDs, characterized by their exceptional photoluminescence (PL), high water solubility/dispersibility, non-toxicity, and biocompatibility, substantiate their potential for a wide range of applications in sensing and biology. Moreover, nature offers plant- and animal-derived precursors for the sustainable synthesis of CDs and their doped variants. These sources are not only readily accessible, inexpensive, and renewable but are also environmentally benign green biomass. This review article presents in detail the production of sustainable CDs from various animal and human biomass through bottom-up synthetic methods, including hydrothermal, microwave, microwave-hydrothermal, and pyrolysis methods. The resulting CDs exhibit a uniform size distribution, possibility of heteroatom doping, surface passivation, and remarkable excitation wavelength-dependent/independent emission and up-conversion PL characteristics. Consequently, these CDs have been successfully utilized in multiple applications, such as bioimaging and the detection of various analytes, including heavy metal ions. Finally, a comprehensive assessment is presented, highlighting the prospects and challenges associated with animal/human biomass-derived CDs for multifaceted applications.

Carbon Quantum Dots from Roasted Coffee Beans: Their Degree and Mechanism of Cytotoxicity and Their Rapid Removal Using a Pulsed Electric Field

Carbon quantum dots (CQDs) from heat-treated foods show toxicity, but the mechanisms of toxicity and removal of CQDs have not been elucidated. In this study, CQDs were purified from roasted coffee beans through a process of concentration, dialysis and lyophilization. The physical properties of CQDs, the degree and mechanism of toxicity and the removal method were studied. Our results showed that the size of CQDs roasted for 5 min, 10 min and 20 min were about 5.69 ± 1.10 nm, 2.44 ± 1.08 nm and 1.58 ± 0.48 nm, respectively. The rate of apoptosis increased with increasing roasting time and concentration of CQDs. The longer the roasting time of coffee beans, the greater the toxicity of CQDs. However, the caspase inhibitor Z-VAD-FMK was not able to inhibit CQDs-induced apoptosis. Moreover, CQDs affected the pH value of lysosomes, causing the accumulation of RIPK1 and RIPK3 in lysosomes. Treatment of coffee beans with a pulsed electric field (PEF) significantly reduced the yield of CQDs. This indicates that CQDs induced lysosomal-dependent cell death and increased the rate of cell death through necroptosis. PEF is an effective way to remove CQDs from roasted coffee beans.

Enhanced Activity of Enzyme Immobilized on Hydrophobic ZIF-8 Modified by Ni2+ Ions

The development of efficient enzyme immobilization to promote their recyclability and activity is highly desirable. Zeolitic imidazolate framework-8 (ZIF-8) has been proved to be an effective platform for enzyme immobilization due to its easy preparation and biocompatibility. However, the intrinsic hydrophobic characteristic hinders its further development in this filed. Herein, a facile synthesis approach was developed to immobilize pepsin (PEP) on the ZIF-8 carrier by using Ni²⁺ ions as anchor (ZIF-8@PEP-Ni). By contrast, the direct coating of PEP on the surface of ZIF-8 (ZIF-8@PEP) generated significant conformational changes. Electrochemical oxygen evolution reaction (OER) was employed to study the catalytic activity of immobilized PEP. The ZIF-8@PEP-Ni composite attains remarkable OER performance with an ultralow overpotential of only 127 mV at 10 mA cm^-2 , which is much lower than the 690 and 919 mV overpotential values of ZIF-8@PEP and PEP, respectively.

Formation of protein corona on interaction of pepsin with chitin nanowhiskers in simulated gastric fluid

Protein corona (PC) usually changes the physicochemical properties of nanoparticles (NPs) and determines their ultimate fate in the physiological environment. As NPs are widely used in food, it is important to obtain a deep understanding of PC formation in the gastrointestinal fluid. Herein, we explored the adsorption of pepsin to chitin nanowhiskers (CNWs) and their interactions in simulated gastric fluid. Results suggest that the binding of pepsin reduced the surface potential of CNWs from 22.4 ± 0.15 to 12.9 ± 0.51 mV and caused their aggregation. CNWs quenched the fluorescence of pepsin and induced slightly changes in its secondary structure containing a reduction in the β-sheet content (∼ 3%) and an increase in the random coils (∼ 2%). The isothermal titration calorimetry (ITC) data suggested that the interaction forces between CNWs and pepsin were mainly hydrogen bonds and van der Waals forces.

Formation and biological effects of protein corona for food-related nanoparticles

The rapid development of nanoscience and nanoengineering provides new perspectives on the composition of food materials, and has great potential for food biology research and applications. The use of nanoparticle additives and the discovery of endogenous nanoparticles in food make it important to elucidate in vivo safety of nanomaterials. Nanoparticles will spontaneously adsorb proteins during transporting in blood and a protein corona can be formed on the nanoparticle surface inside the human body. Protein corona affects the physicochemical properties of nanoparticles and the structure and function of proteins, which in turn affects a series of biological reactions. This article reviewed basic information about protein corona of food-related nanoparticles, elucidated the influence of protein corona on nanoparticles properties and protein structure and function, and discussed the effect of protein corona on nanoparticles in vivo. The effects of protein corona on nanoparticles transport, cellular uptake, cytotoxicity, and immune response were reviewed, and the reasons for these effects were also discussed. Finally, future research perspectives for food protein corona were proposed. Protein corona gives food nanoparticles a new identity, which makes proteins bound to nanoparticles undergo structural transformations that affect their recognition by receptors in vivo. It can have positive or negative impacts on cellular uptake and toxicity of nanoparticles and even trigger immune responses. Understanding the effects of protein corona have potential in evaluating the fate of the food-related nanoparticles, providing physicochemical and biological information about the interaction between proteins and foodborne nanoparticles. The review article will help to evaluate the safety of protein coronas formed on nanoparticles in food, and may provide fundamental information for understanding and controlling nanotoxicity.

Protein corona formation of human serum albumin with carbon quantum dots from roast salmon

When food-borne nanoparticles enter biological systems, they can interact with various proteins to form protein coronas, which can affect their physicochemical properties and biological identity. In this study, the protein corona formation of carbon quantum dots (CQDs) from roast salmon with human serum albumin (HSA) was explored. Furthermore, the biological identity of the HSA-CQD coronas, in relation to cell apoptosis, energy, glucose and lipid metabolism and acute toxicity in mice, was also investigated. The HSA-CQD coronas were formed between HSA and CQDs via a static binding mechanism, and the binding site of CQDs on HSA was located at both Sudlow's site I and site II. After entering the cytoplasm, the HSA-CQD coronas became localized in the lysosomes and autolysosomes. Importantly, the HSA coronas reduced the cytotoxicity of the CQDs from 18.65% to 9.26%, and the energy metabolism was rectified by changing from glycolytic to aerobic metabolism. The glucose and lipid metabolite profile of cells exposed to the HSA-CQD coronas differed from that of those treated with CQDs, indicating that the HSA-CQD coronas rectified metabolic disturbances caused by CQDs. Histopathological and blood biochemical analysis revealed no statistically significant differences between the treated and control mice after a single CQDs dose of 2000 mg per kg body weight. Overall, the results confirmed the formation of protein coronas between HSA and food-borne fluorescent CQDs, and could be helpful for evaluating the safety of fluorescent CQDs in cooked food items.

Construction and evaluation of an iron delivery system by ultra-small nanoparticles from roast sturgeon (Acipenser schrenckiid)

A new type of ultra-small food-borne nanoparticles with multiple functional groups from roast sturgeon were prepared, which had potential as efficient nanocarriers for Fe(ii) delivery.

Molecular interaction of fluorescent carbon dots from mature vinegar with human hemoglobin: Insights from spectroscopy, thermodynamics and AFM

Foodborne nanoparticles have attracted considerable interest due to their distinctive fluorescence and physicochemical properties. The discovery of vinegar carbon dots (VCDs) has drawn our attention to study their effect on human plasma protein. Herein, spectral, constructional, morphological, and enzymatic activity assessments were carried out to investigate the interaction of VCDs with human hemoglobin (HHb). The intrinsic fluorescence of HHb was quenched significantly by the VCDs through a static quenching process. Furthermore, binding constants and important thermodynamic parameters were calculated, the negative enthalpy and entropy changes were accompanied by a negative Gibbs energy, which proposed the binding between VCDs with HHb was spontaneous. Moreover, negative enthalpy and entropy change corroborated the involvement of van der Waals force and hydrogen bonds in the binding process. Results from FTIR, atomic force microscopy and circular dichroism revealed change of HHB after binding with VCDs although their essential morphological features were unaffected. The esterase activity of HHb decreased after VCDs treatment in a dose-dependent manner, which further confirmed the effect of VCDs on HHb. The results offered detailed information about the interaction between VCDs and HHb.

Toxicity Alleviation of Carbon Dots from Roast Beef after the Formation of Protein Coronas with Human Serum Albumin

The unique properties of nanoparticles produced during food thermal processing have attracted considerable attention. In this study, the formation of protein coronas of fluorescent carbon dots (CDs) in roast beef with human serum albumin (HSA) and the corona effect on toxicity were reported. The CDs were roughly spherical with a size in the range of 1-5 nm, which were mainly composed of carbon (68.68%), nitrogen (10.6%), and oxygen (15.98%). The CDs could readily pass through the intestine wall due to their small size and good water solubility. There was an obvious interaction between HSA and CDs, suggesting that the CDs could form protein coronas. Thermodynamic analysis results of ΔH < 0 (-13.17 ± 3.74 kJ/mol) and ΔS > 0 ( 28.04 J/mol/K) indicated that the binding of HSA-CDs was due to electrostatic interactions or hydrophobic forces. The HSA-CD coronas were distributed in the lysosomes of the cells, alleviated swelling caused by the CDs, and inhibited the decrease of mitochondrial membrane potential caused by CDs. Furthermore, the protein coronas reduced cellular reactive oxygen species production and alleviated the consumption of glutathione by the CDs, thus protecting the cells from damage. This finding provided valuable information about protein coronas in ameliorating cytotoxicity.

Endogenous Fluorescence Carbon Dots Derived from Food Items

Background

Fluorescent carbon dots (CDs) are a novel class of carbon-based nanomaterials that were discovered in 2004. However, nobody knew that CDs existed in food items naturally until 2012. Properties of nanosize materials are distinct from those of their bulk materials due to the particle size and accordingly alter their bioavailability and/or biocompatibility. Therefore, the potential health risk of nanoparticles in food has drawn massive attention. Currently, almost all studies regarding the biosafety of nanoparticles in food have mainly focused on engineered nanoparticles used as food additives and have excluded the endogenous nanoparticles in food. Therefore, investigation of the properties of food-borne fluorescent CDs and their potential health risk to humans is of great significance.

Scope and approach

This review summarizes the existing literature on fluorescent carbon dots (CDs) in food, with particular attention to their properties, formation process, and the potential health risks posed to consumers. The knowledge gap between food-borne nanoparticles and their potential risks is identified, and future research is proposed.

Key findings and conclusions

The presence of fluorescent CDs in food produced during food processing has been summarized. Fluorescent CDs less than 10 nm in size mainly contain carbon, oxygen, hydrogen, and/or nitrogen. The presence of CDs in food items was first demonstrated in 2012, and their formation was attributed to heating of the starting material. The properties of CDs in food are different from the engineered nanoparticles used as food as additives and represent a novel kind of nanostructure in food. Further studies should focus on the chronic effects of CDs, although their toxicity is low, because investigations both in vivo and in vitro are limited.

Food-borne nanocarriers from roast beef patties for iron delivery

Fluorescent nanoparticles (FNs) from roast beef patties were characterized and used as nanocarriers for ferrous ions.