Ultrasensitive detection of thiram based on surface-enhanced Raman scattering via Au@Ag@Ag core/shell/shell bimetallic nanorods.

We developed a highly sensitive and stable SERS-active substrate of Au@Ag@Ag core/shell/shell nanorods, formed by encapsulating Au nanorods (Au NRs) into a bilayer silver shell with Raman reporter molecules (4-mercaptobenzoic acid (4-MBA) and thiram) in the shell-shell gap. The core/shell/shell nanostructures demonstrated a high SERS enhancement and easy assembly. The important role of the bilayer silver shell in boosting the SERS intensity and detection sensitivity was revealed by comparing the performances of the Au@Ag@4-MBA@Ag NRs, Au@Ag@4-MBA NRs, and Au@4-MBA NRs. The obtained Au@Ag@4-MBA@Ag NRs exhibited a significantly promoted SERS intensity, which could reach around 2.6 times and 240 times that of the Au@Ag@4-MBA NRs and Au@4-MBA NRs, where the enhancement factor was found to be strongly correlated with the shell thickness. The controllable plasma properties and SERS effect of the Au@Ag@4-MBA@Ag NRs could be optimized by adjusting the dose of silver nitrate. The SERS substrate comprising core/shell/shell nanorods was highly reproducible and stable (retaining 83% SERS intensity after one month). Moreover, the highly sensitive detection of the pesticide thiram with a detection limit as low as 1.74 × 10-9 M was achieved by taking advantage of the great SERS response of the core/shell/shell nanostructures, which was 1-2 orders of magnitude lower than for other SERS substrates. The developed SERS substrate could be readily extended to embed other target analytes into the core/shell/shell nanostructure for novel and sensitive detection. This study could enable fresh approaches toward next-generation ultrasensitive analyte detection.

A ratiometric SERS sensor with one signal probe for ultrasensitive and quantitative monitoring of serum xanthine.

Xanthine can be converted into uric acid, and a high concentration of xanthine in the human body can cause many diseases. Therefore, it is important to develop a sensitive, simple, and reliable approach for measuring xanthine in biological liquids. Hence, a ratiometric surface-enhanced Raman spectroscopy (SERS) sensing strategy with one signal probe was exploited for reliable, sensitive, and quantitative monitoring of serum xanthine. 3-Mercaptophenylboronic acid (3-MPBA) was used as a typical reference with a Raman peak at 996 cm-1. First, 3-MPBA was bound to gold nanoflowers@silica (GNFs@Si) through Au-S bonds. Xanthine oxidase (XOD) catalyzed the oxidation of xanthine into H2O2 on GNFs@Si. Afterward, the obtained H2O2 further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) accompanied by the emergence of a new Raman peak at 883 cm-1. Meanwhile, the Raman intensity at 996 cm-1 remained constant. Therefore, the ratio of I883/I996 increased with the increasing of xanthine concentration, thus realizing quantitative detection of xanthine. As a result, a ratiometric SERS sensor for the detection of xanthine was proposed with a detection limit of 5.7 nM for xanthine. The novel ratiometric SERS sensor provides a new direction for analyzing other biomolecules with high sensitivity and reliability.

The applications of carbon dots in oral health: A scoping review.

OBJECTIVES: This scoping review aims to provide an overview of the research and potential applications of carbon dots (CDs) for oral health purposes. DESIGN: Systematic literature searches were performed on PubMed and Web of Science databases (up to February 2023). Two co-authors selected the published works independently and extracted the data in accordance with the PRISMA statement. Studies with the application of CDs for oral health purposes were included. RESULTS: Among 152 articles, 19 articles were finally selected. Eight studies investigated the anti-microbial effects of CDs against, for example, oral pathogens, eight studies explored the applicability of CDs in relation to oral cancer, and three studies investigated CDs in relation to cell differentiation and tissue regeneration in oral health. The studies showed the promising potential of CDs in oral health, particularly for inducing bacterial killing by increasing reactive oxygen species, killing oral cancer cells via photodynamic therapeutic effects, and inducing dental pulp and periodontal bone regeneration. CONCLUSION: The findings show that CDs have the potential to be utilized in the future for various oral health purposes. Besides, these results underline the broad-spectrum applicability of CDs, crossing the borders of oral health.

Carbon quantum dots as immune modulatory therapy in a Sjögren's syndrome mouse model.

OBJECTIVES: The objective of the study was to evaluate the therapeutic effects of carbon quantum dots (CQDs) in immunomodulation on non-obese diabetic (NOD) mice, as the model for Sjögren's syndrome (SS). METHODS: Carbon quantum dots were generated from Setaria viridis via a hydrothermal process. Their toxic effects were tested by cell viability and blood chemistry analysis, meanwhile therapeutic effects were investigated in NOD mice in the aspects of saliva flow, histology, and immune cell distribution. RESULTS: Carbon quantum dots, with rich surface chemistry and unique optical properties, showed non-cytotoxicity in vitro or no damage in vivo. Intravenously applied CQDs alleviated inflammation in the submandibular glands in NOD mice after 6-week treatments. The inflammatory area index and focus score were significantly decreased in CQD-treated mice. Besides, the levels of anti-SSA and anti-SSB were decreased in the presence of CQDs. The stimulated saliva flow rates and weight of submandibular glands were significantly increased in CQD-treated mice by reducing the apoptosis of cells. The CD3+ and CD4+ T cells distributed around the ducts of submandibular glands were significantly decreased, while the percentage of Foxp3+ cells was higher in CQD-treated mice than that in the control group. CONCLUSIONS: Our findings suggest that CQDs may ameliorate the dysregulated immune processes in NOD mice.

Signal amplification surface-enhanced Raman scattering immunosorbent assay of human chorionic gonadotrophin based on repeated enzyme biocatalytic precipitation.

A novel surface-enhanced Raman scattering (SERS) immunoassay method based on tyramine signal amplification (TSA) technology triggering the formation of enzyme repeats on an enzyme-linked immunosorbent assay (ELISA) was designed for highly sensitive detection of human chorionic gonadotropin (hCG) using enzymatic biocatalytic precipitation toward o-phenylenediamine (OPD). Initially, a horseradish peroxidase (HRP)-labeled hCG antibody was fixed by the double antibody sandwich method, and then a tyramine-HRP conjugate was used to form HRP repeats by triggering the immobilized HRP on ELISA with the aid of H2O2. In the presence of the target hCG, the HRP repeats carried by the sandwich immune complex catalyzed the oxidation of OPD to produce product molecules with different structures, resulting in changes in the SERS fingerprint spectrum. The analytical performance of the SERS immunoassay was studied in detail using SERS spectral characterization. Under the optimum conditions, the immunosensor displayed a working range from 1 IU L-1 to 16 IU L-1 with a detection limit (LOD) of 0.17 IU L-1 relative to the target hCG. Compared to the traditional SERS immunosensor, a higher detection sensitivity can be obtained. Therefore, this work provides a new strategy for hCG detection and inspiration for the construction of sensitive and efficient immunosensors.

Horseradish peroxidase-repeat assay based on tyramine signal amplification for highly sensitive H2O2 detection by surface-enhanced Raman scattering.

A new and simple surface-enhanced Raman scattering (SERS) biosensor based on the tyramine signal amplification (TSA)-triggered formation of horseradish peroxidase (HRP) repeats on a gold sensing chip was designed for the highly sensitive detection of hydrogen peroxide (H2O2). Initially, gold wafers were functionalized with HRP as sensing chips. Then, the HRP immobilized on the chips triggers the TSA reaction to transform the tyramine-HRP conjugate into a tyramine-HRP repeat array. With the aid of the target H2O2, the HRP repeats catalyze the oxidation of o-phenylenediamine (OPD) and produce an enzyme catalytic product with a different chemical structure, thus altering the fingerprint of the SERS spectra from that of OPD. H2O2 can be quantitatively analyzed according to the change in SERS signal intensity. On the basis of the TSA strategy, the proposed method allows the detection of H2O2 with a limit of detection (LOD) of 0.8 × 10-8 M. The as-prepared SERS sensor can achieve high-sensitivity H2O2 detection with a small amount of sample for each analysis. Therefore, this sensor exhibits significant potential for application in bioanalysis.

First Report of Anthracnose on Jerusalem Cherry Caused by Colletotrichum liaoningense in Shandong, China.

Jerusalem cherry (Solanum pseudocapsicum), which belongs to the genus Solanum and the family Solanaceae, possesses high ornamental value and is widely cultivated as an indoor ornament due to its bright red berries at maturity (Xu et al., 2018). In September 2019, leaf spot was detected on jerusalem cherry plants in Yuxiu Park, Shizhong district, Jinan, Shandong Province. Field surveys were done in a 1/15 ha park. Disease incidence was estimated at approximately 18% across the survey area. Foliar symptoms began as small white spots. As the disease progressed, lesions expanded and merged, and developed into large irregular white spots, with pale grey edge. At last, lesions were densely distributed throughout the leaves. To isolate the pathogen, twenty leaf tissues (5 × 5 mm) were cut from the border between diseased and healthy tissue, surface disinfected in 75% alcohol for 15 s, soaked in 0.1% mercuric chloride for 1 min, washed with sterile distilled water three times, and cultured on potato dextrose agar (PDA) at 25°C. Nineteen fungal isolates were obtained and were single-spored to obtain pure cultures. The colony of LCL7, a representative isolate, on PDA was initially white to orange, but turned black after 3 to 4 days incubation with black conidial masses. Conidia were single-celled, hyaline, straight, cylindrical, apex obtuse, and ranged from 13.4 to 18.3 × 3.2 to 4.9 µm (n = 50) （Diao et al., 2017）. To validate the species identification, rDNA internal transcribed spacer (ITS) region (White et al., 1990), and the partial sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), ß-tubulin (TUB2), and chitin synthase (CHS-1) (Damm et al., 2019; He et al., 2019), were amplified and sequenced. The ITS, GAPDH, ACT, TUB2, and CHS-1 sequences of isolate LCL7 were submitted to GenBank (MW221320, MW227217, MW227218, MW227219, and MW266988, respectively). ITS, ACT, TUB2, and CHS-1 BLAST showed 99-100% homology with sequences of Colletotrichum liaoningense (ITS, 100% to MH636504; ACT, 100% to MH622582; TUB2, 99.56% to MH622714, CHS-1, 99.33% to MH622446, respectively), although GAPDH showed 93.98% homology with sequence MH681383 (234/249bp). Neighbor-joining tree based on concatenated sequences of the five genes was constructed using MEGA7.0. The results showed the isolate was closely related to C. liaoningense. Based on morphological and molecular characteristics, the isolate LCL7 was identified as C. liaoningense. Pathogenicity tests were performed by spraying a conidial suspension (1 × 105 conidia/mL) on ten two-year-old healthy jerusalem cherry plants. Ten other plants with sterile water served as controls. All samples were incubated in a growth chamber at 25±2°C and transparent plastic bags to keep relative humidity high for 2 days. All inoculated plants showed symptoms similar to those observed in the field after 21 days, but no disease occurred on control plants. The same fungus was successfully reisolated from inoculated leaves and reidentified based on morphology and molecular characteristics, and the fungus was not isolated from the control plants, thus confirming Koch's postulates. Pathogenicity tests were repeated twice. C. liaoningense can cause anthracnose in chili and mango in China (Diao et al., 2017; Li et al., 2019).To our knowledge, this is the first report of anthracnose on jerusalem cherry caused by C. liaoningense in China, which influences ornamental value and reduces market value. Identification of the causes of the disease will help develop effective strategies for managing this disease.

A simple enzyme-free SERS sensor for the rapid and sensitive detection of hydrogen peroxide in food.

A simple enzyme-free method based on surface-enhanced Raman scattering (SERS) was developed for the first time to detect H2O2 in food by etching a self-assembled film of silver nanoparticles (Ag NPs) on a glass substrate. H2O2 is able to oxidize Ag NPs to yield Ag+ ions; this process reduces the size of the Ag NPs and ultimately leads to a decrease in the SERS signal of the Raman probe. The intensities of the SERS spectra were strongly correlated with H2O2 concentration, which indicated that the Ag NP self-assembled SERS sensor can be successfully used for the quantitative analysis of H2O2. The main advantage of this SERS sensor is that it can directly detect H2O2 without introducing complex enzymatic reactions. This easy-to-operate and fast-response detection technology has great potential for the sensitive detection of H2O2 in food.

Lengthening the aptamer to hybridize with a stem-loop DNA assistant probe for the electrochemical detection of kanamycin with improved sensitivity.

By adding 6 thymines to lengthen the parent aptamer combined with the change of "on" and "off" induced by the target for an assistant stem-loop DNA probe (ASP-SLP-MB), a new folding-type electrochemical kanamycin (Kana) aptamer-engineering dual-probe-based sensor (sensor d) was developed. By purposefully reducing the background current and increasing the electron transfer efficiency of methylene blue (MB), the sensor obtained significantly enhanced detection sensitivity compared with non-aptamer-engineering one-probe-based sensor (sensor a). Such efficacy was validated by a big decrease from 530.6 to 210.2 nA for the background current signal and from 360 to 0.3 nM for the detection limit. In addition to the improved sensitivity, the sensor also exhibited good selectivity, anti-fouling detection performance, and potential quantitative analysis ability, showing a feasible potential practical analytical application in real-life complicated samples, for example, milk and serum. The released results prove that the aptamer-engineering method is effective in improving the analytical performance of folding-type sensors and provides a methodological guidance for the design and fabrication of other high-performance folding-type aptasensors. Graphical abstract.

Catalyzed Deposition of Signal Reporter for Highly Sensitive Surface-Enhanced Raman Spectroscopy Immunoassay Based on Tyramine Signal Amplification Strategy.

A novel surface-enhanced Raman spectroscopy (SERS) sensor was proposed for an ultrasensitive detection immunoassay based on tyramine signal amplification (TSA) strategy. In this study, an immune sandwich was prepared with a capture antibody and a horseradish peroxidase (HRP)-conjugated antibody upon the addition of a target antigen. In the presence of H2O2, HRP can convert tyramine to a short-lived radical intermediate that forms covalent compounds with aromatic amino acids on the surfaces of proteins. By labeling the tyramine with SERS tags in the form of gold nanoparticles (AuNPs) functionalized with a Raman-active probe (4-mercaptobenzoic acid, 4-MBA), AuNPs@4-MBA was deposited and aggregated near the proteins, so the SERS signal of 4-MBA could be detected and amplified. On the basis of the TSA strategy, the developed SERS-based immunoassay can discriminate concentrations as low as 0.01 ng/mL of the target antigen and exhibited approximately 10 times stronger SERS signal intensity than traditional SERS-based immunoassays. These results demonstrated the application potential of this TSA-based SERS biosensor for the detection of important proteins in biomedical research.

A fast-responsive fluorescent probe for sensitive detection of graphene oxide based on MoS2 quantum dots.

Facile preparation of water soluble and fluorescent N-doped MoS2 quantum dots (N-MoS2 QDs) is described herein. N was introduced to reduce defects in the MoS2 surface. The obtained N-MoS2 QDs exhibited excellent fluorescence characteristics with good photostability and excellent stability even in 3 M NaCl solution and when stored in a refrigerator for one year. Additionally, the fluorescent N-MoS2 QDs were developed as a simple and practical nanosensor for the detection of GO through hydrophobic π-π interactions between N-MoS2 QDs and GO, where the excited state electron and energy transfer may occur from N-MoS2 QDs to GO along with fluorescence quenching of N-MoS2 QDs. These results reveal that the limit of detection (LOD) was as low as 4 ng mL-1, which was able to satisfy the needs of the determination of GO in environmental water samples. Importantly, the N-MoS2 QDs nanosensor exhibits excellent detection selectivity against other ions or molecules in the environment. In this study, the proposed sensor was successfully used for the determination of GO content in environmental water samples.

Facile detection of glucose in human serum employing silver-ion-guided surface-enhanced Raman spectroscopy signal amplification.

A facile surface-enhanced Raman scattering (SERS) sensor based on a silver-ion-mediated amplification effect was designed for the determination of glucose concentration. In this approach, 4-aminothiophenol (4-ATP) molecules assembled on the surface of a gold wafer (Au wafer@4-ATP) act not only as Raman tags but also as linkage agents. Silver nanoparticles marked with cysteamine (AgNP@cys) were used as the SERS enhancement components because they could be bound to the Au wafer@4-ATP in the presence of silver ions through the formation of N → Ag+ ← N coordination compounds. Here, the Ag+ ions were obtained by using glucose oxidase to catalyze the oxidation of glucose, producing hydrogen peroxide (H2O2) to etch the AgNPs. Therefore, we recorded the SERS intensity of 4-ATP to determine the concentration of glucose in a phosphate buffer as low as 0.1 mM and further achieved a lowest detection of 0.5 mM glucose in human serum. These results show that the proposed approach has strong potential for practical applications.

Aptamer-based surface-enhanced Raman scattering (SERS) sensor for thrombin based on supramolecular recognition, oriented assembly, and local field coupling.

A supramolecular recognition and oriented assembly system was developed on chip for the highly selective surface-enhanced Raman scattering (SERS) detection of thrombin by means of the aptamer-based SERS tag method. A 15-base thrombin-binding aptamer (TBA15) with a thiol end was first immobilized on an Ag nanoprism array by the S-Ag bond. This aptamer has high binding affinity with thrombin when it folds into a G-quadruplex structure. After the recognition between the aptamer and thrombin, a bridge is built between the SERS tag (4-mercaptobenzoic acid marked Ag nanoparticle) and the fixed thrombin based on the activation of the carboxylic group of 4-mercaptobenzoic acid. Thus, the quantitative detection of thrombin can be achieved based on the SERS intensity of the immobilized SERS tags. The obvious advantages of this sensing method are as follows: (1) remarkable SERS enhancement due to the high electric field coupling effect via the gap structure formation, which improves the sensitivity of the SERS detection and the limit of detection of this method arrives in 1.6 × 10-11 M, (2) high selectivity based on the specific aptamer recognition toward thrombin, which can be extended to other enzymes easily by changing a proper sequence, (3) high repeatability of SERS signals according to a highly ordered structure, and (4) highly efficient oriented assembly of a sandwich structure over an Ag nanoprism array. The proposed method is expected to be a practical implement in medical diagnosis. Graphical Abstract Illustration of the aptamer-based SERS sensor for thrombin detection.

Glucose oxidase probe as a surface-enhanced Raman scattering sensor for glucose.

Glucose oxidase (GOx) possessing a Raman-active chromophore (flavin adenine dinucleotide) is used as a signal reporter for constructing a highly specific "turn off" surface-enhanced Raman scattering (SERS) sensor for glucose. This sensing chip is made by the electrostatic assembly of GOx over silver nanoparticle (Ag NP)-functionalized SERS substrate through a positively charged polyelectrolyte linker under the pH of 6.86. To trace glucose in blood serum, owing to the reduced pH value caused by the production of gluconic acid in the GOx-catalyzed oxidation reaction, the bonding force between GOx and polyelectrolyte weakens, making GOx drop off from the sensing chip. As a result, the SERS intensity of GOx on the chip decreases along with the concentration of glucose. This glucose SERS sensor exhibits excellent selectivity based on the specific GOx/glucose catalysis reaction and high sensitivity to 1.0 µM. The linear sensing range is 2.0-14.0 mM, which also meets the requirement on the working range of the human blood glucose detection. Using GOx as a probe shows superiority over other organic probes because GOx almost has no toxicity to the biological system. This sensing mechanism can be applied for intracellular in vivo SERS monitoring of glucose in the future. Graphical abstract Glucose oxidase is used as a Raman signal reporter for constructing a highly specific glucose surface-enhanced Raman scattering (SERS) sensor.

Aptamer-based surface-enhanced Raman scattering-microfluidic sensor for sensitive and selective polychlorinated biphenyls detection.

A surface-enhanced Raman scattering (SERS) measurement of 3,3',4,4'-tetrachlorobiphenyl (PCB77) with aptamer capturing in a microfluidic device was demonstrated. To construct the microfluidic chip, an ordered Ag nanocrown array was fabricated over a patterned polydimethylsiloxane (PDMS) that was achieved by replicating an anodic aluminum oxide (AAO) template. The patterned PDMS sheet was covered with another PDMS sheet having two input channel grooves to form a close chip. The Ag nanocrown array was used for the SERS enhancement area and the detection zone. PCB 77 aptamers were injected into one channel and the other allows for analytes (PCBs). The mercapto aptamers captured the targets in the mixed zone and were immobilized to the SERS detection zone via S-Ag bonds so as to further improve both the SERS sensitivity and selectivity of PCB77. Such an aptamer-based microfluidic chip realized a rapid SERS detection. The lowest detectable concentration of 1.0 × 10(-8) M was achieved for PCB77. This work demonstrates that the aptamer-modified SERS microfluidic sensor can be utilized for selective detections of organic pollutants in the environment.

DNAzyme-based plasmonic nanomachine for ultrasensitive selective surface-enhanced Raman scattering detection of lead ions via a particle-on-a-film hot spot construction.

We propose a highly sensitive and selective surface-enhanced Raman scattering (SERS) method for determining lead ions based on a DNAzyme-linked plasmonic nanomachine. A metallic nanoparticle-on-a-film structure was built through a rigid double-stranded bridge linker composed of a DNAzyme and its substrate. This DNAzyme could be activated by lead ions and catalyze a fracture action of the substrate. Thus, the double chain structure of DNA would turn into a flexible single strand, making the metal nanoparticles that connected to the terminal of DNAzyme fall to the surface of the metal film. Hereby, a narrow gap close to 2 nm generated between metal nanoparticles and the metal film, exhibiting a similar effect of a "hot spot" and remarkably enhancing the signal of randomly dispersed Raman-active molecules on the surface of metal film. By measuring the improvement of SERS intensity of the Raman-active molecules, we realized the lowest detection concentration of Pb(2+) ions to 1.0 nM. This SERS analytical method is highly selective and can be extended universally to other targets via the accurate programming of corresponding DNA sequences.

Carbon dots combined with phytosphingosine inhibit acid-induced demineralization of hydroxyapatite in vitro.

OBJECTIVES: To study the effects of carbon dots (CDs), in combination with phytosphingosine (PHS), against acid-induced demineralization of hydroxyapatite in vitro. METHODS: CDs were generated from citric acid and urea by microwave heating. Transmission electron microscope (TEM), FT-IR, and fluorescence intensity were used to characterize the CDs. A hydroxyapatite (HAp) model was used to investigate the protective effects of CDs, PHS, and their combinations with and without a salivary pellicle against acid-induced demineralization in vitro. Ca2+ release as a parameter to evaluate the inhibition of demineralization was measured by capillary electrophoresis. The interactions between CDs, PHS, and HAp discs were investigated using a fluorescence detector. RESULTS: Uniform-sized CDs were synthesized, showing typical optical characteristics. CDs exhibited no inhibition of acid-induced demineralization in vitro, in contrast to PHS. Notably, a pre-coating of CDs increased the protective effects of PHS against acid-induced demineralization, which was not disturbed by the presence of a salivary pellicle and Tween 20. Scanning electron microscope (SEM) confirmed the binding and layers formed of both CDs and PHS to the HAp surfaces. Based on fluorescence spectra CDs binding to HAp seemed to be dependent on Ca2+ and PO43- interactions. CONCLUSIONS: CDs combined with PHS showed protective effects against acid-induced demineralization of HAp discs in vitro.

'Switch-off' biosensing for chymotrypsin-catalyzed reaction by SPR-SERS spectroscopy.

We describe a novel 'switch-off' biosensing strategy for the detection of chymotrypsin based on surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) spectroscopy. This approach analyzes the fingerprint spectrum of the chymotrypsin-catalyzed substrate. The lowest probed concentration is 0.4 nM for chymotrypsin.

Identification and Characterization of MUC5B Binding Peptides by Phage Display.

OBJECTIVES: MUC5B plays a multifactorial role in oral health. As a consequence, decreased MUC5B output leads to impaired salivary functions and xerostomia. Synthetic combinatorial technologies have been used to develop functional peptide libraries by phage display e.g. for therapeutic purposes. In this light, our primary aim was to identify peptide sequences with specific selectivity for salivary MUC5B in vitro using phage display. Our secondary aims were to analyze their effect on salivary spinnbarkeit in situ and their effect on acid-induced demineralization in vitro. METHODS: MUC5B binding phages were selected by phage display. Peptide affinity to MUC5B was evaluated using MUC5B coated hydroxyapatite (HA) granules. The MUC5B binding peptides (MBPs) were then examined for their effects on salivary spinnbarkeit and protective effect on acid-induced demineralization in vitro. A competitive ELISA was performed to identify the binding epitope on MUC5B using F2, a MUC5B specific antibody. RESULTS: MBP-12 and MBP-14 displayed the highest affinity to MUC5B. MBP-12 mildly stabilized the spinnbarkeit of serous saliva after overnight incubation and of mucous saliva at all timepoints tested. The addition of MBP-12 to a pellicle of unstimulated saliva on HA discs showed no additive protective effect against acid-induced demineralization. Epitope characterization suggested sulfo-Lewisa SO3-3Gal_1-3GlcNAc (galactose residue) as MBP-12 binding site on MUC5B. CONCLUSIONS: The use of phage display in generating MBPs was successful. Characterization of the MBPs revealed a mild effect on spinnbarkeit in case of mucous saliva. Possibly, combinatorial peptide libraries might contribute to the development of novel formulations to treat xerostomia.

In vitro and in vivo toxicological evaluation of carbon quantum dots originating from Spinacia oleracea.

Food-derived carbon quantum dots (CQDs) can relatively easily be synthesized and chemically manipulated for a broad spectrum of biomedical applications. However, their toxicity may hinder their actual use. Here, Spinacia oleracea-derived CQDs i.e., CQD-1 and CQD-2, were synthesized by means of different shredding methods and followed by a microwave-assisted hydrothermal approach. Subsequently, these CQDs were analyzed in vitro and in an in vivo mice model to test their biocompatibility and potential use as bioimaging agents and for activation of osteogenic differentiation. When comparing CQD-1 and CQD-2, it was found that CQD-1 exhibited 7.6 times higher photoluminescent (PL) emission intensity around 411 nm compared to CQD-2. Besides, it was found that the size distribution of CQD-1 was 2.05 ± 0.08 nm, compared with 2.14 ± 0.04 nm for CQD-2. Upon exposure to human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro, CQD-1 was endocytosed into the cytoplasm and significantly increased the differentiation of hBMSCs up to 10 µg mL-1 after 7 and 14 days. Apparently, the presence of relatively low doses of CQD-1 showed virtually no toxic or histological effects in the major organs in vivo. In contrast, high doses of CQD-1 (1 mg mL-1) caused cell death in vitro ranging from 35% on day 1 to 80% on day 3 post-exposure, and activated the apoptotic machinery and increased lymphocyte aggregates in the liver tissue. In conclusion, S. oleracea-derived CQDs have the potential for biomedical applications in bioimaging and activation of stem cells osteogenic differentiation. Therefore, it is postulated that CQD-1 from S. oleracea remains potential prospective material at appropriate doses and specifications.