Cu,Zn,I-Doped Carbon Dots with Boosted Triple Antioxidant Nanozyme Activity for Treatment of DSS-Induced Colitis.

Nanozyme-mediated antioxidative therapy is a promising star for treating a myriad of important diseases through eliminating excessive reactive oxygen species (ROS) such as O2·- and H2O2, a critical mechanism for inflammatory bowel disease (IBD). This work provides a high biocompatibility iodine-copper-zinc covalent doped carbon dots (Cu,Zn,I-CDs) with the catalase (CAT)-, superoxide dismutase (SOD)- and glutathione peroxidase (GPx)-like catalytic activities for treating ulcerative colitis (UC) by scavenging overproduced ROS. We found that I dopant aids in counteracting the positive charge at Cu,Zn dopants brought on by low pH, enabling Cu,Zn,I-CDs to process strong triple antioxidant nanozyme activities rather than Cu,Zn-CDs. Vitro experiments displayed that the Cu,Zn,I-CDs could scavenge the excessive ROS to protect cellular against oxidative stress and reduce the expression of proinflammatory cytokines, such as TNF-α, IL-1ß, and IL-6. In sodium dextran sulfate (DSS)-induced colitis mice models, Cu,Zn,I-CDs with excellent biocompatibility could effectively relieve the inflammation of the colon, containing the reduction of the colon length, the damaged epithelium, the infiltration of inflammatory cells, and upregulation of antioxidant genes. Therefore, the therapy of Cu,Zn,I-CD antioxidant nanozymes is an effective approach and provides a novel strategy for UC treatment.

Colorimetric-SERS dual-mode aptasensor for Staphylococcus aureus based on MnO2@AuNPs oxidase-like activity.

The nanozyme-linked aptamer-sorbent assay (NLASA) is a rapid way to screen and characterize aptamer binding to targets. In this paper, a MnO2@AuNPs@aptamer (Apt) based NLASA coupled with colorimetric-SERS dual-mode for Staphylococcus aureus (S. aureus) detection is presented. Cu,Fe-CDs were used as the reducing agent to synthesize MnO2 and gold nanoparticles (AuNPs). Then, they were fabricated to obtain MnO2@AuNPs with oxidase (OXD)-like and SERS activities. The S. aureus aptamer was conjugated to MnO2@AuNPs and enhanced the OXD-like activity, which realized the specific capture of S. aureus in food matrices. In addition, S. aureus improves the oxidation of 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid (ABTS) but inhibits 3,3',5,5'-tetramethylbenzidine (TMB) to generate Raman-active oxTMB with MnO2@AuNPs@Apt. This sensor was used for detections of S. aureus in a concentration ranged from 101 to 107 CFU/mL with a detection limit of 0.926 CFU/mL (colorimetric) and 1.561 CFU/mL (SERS), and the recovery is 85%-105% in real samples.

Aptamer-functionalized Fe3O4/MWCNTs@Mo-CDs nanozyme for rapid colorimetric detection toward Escherichia coli.

The pathogenic bacteria induced foodborne disease has been detrimental to public health worldwide. Herein, the peroxidase (POD)-like Fe3O4/MWCNTs@Mo-CDs (FMMC) nanozyme was applied for the detection of Escherichia coli (E. coli). The E. coli aptamer was conjugated with the surface of the FMMC, which effectively enhanced the POD-like activity attributing to the higher affinity to the substrate, and then specific capture of E. coli in food matrices, leading to the reduction of POD-like activity. Therefore, a robust and facile colorimetric aptasensor was developed for detecting E. coli with a wide linear range of 101-106 CFU/mL, low LOQ of 101 CFU/mL and LOD of 0.978 CFU/mL. The aptasensor demonstrated the satisfied selectivity for E. coli compared to the other strains. This method possessed the potential application for fast in situ screening of foodborne pathogens in food products.

Gelatinase-responsive biodegradable targeted microneedle patch for abscess wound treatment of S. aureus infection.

Abscess wound caused by bacterial infection is usually difficult to heal, thus greatly affect people's quality of life. In this study, a biodegradable drug-loaded microneedle patch (MN) is designed for targeted eradication of S. aureus infection and repair of abscess wound. Firstly, the bacterial responsive composite nanoparticle (Ce6@GNP-Van) with a size of about 182.6 nm is constructed by loading the photosensitizer Ce6 into gelatin nanoparticle (GNP) and coupling vancomycin (Van), which can specifically target S. aureus and effectively shield the phototoxicity of photosensitizer during delivery. When Ce6@GNP-Van is targeted and enriched in the infected regions, the gelatinase secreted by the bacteria can degrade GNP in situ and release Ce6, which can kill the bacteria by generating ROS under laser irradiation. In vivo experiments show that the microneedle is basically degraded in 10 min after inserting into skin, and the abscess wound is completely healed within 13 d after applying Ce6@GNP-Van-loaded MN patch to the abscess wound of the bacterial infected mice with laser irradiation, which can simultaneously achieve the eradication of biofilm and subsequent wound healing cascade activation, showing excellent synergistic antibacterial effect. In conclusion, this work establishes a synergistic treatment strategy to facilitate the repair of chronic abscess wound.

Carbon quantum dot fluorescent probe for labeling and imaging of stellate cell on liver frozen section below freezing point.

The targeted labeling imaging of stellate cells on liver frozen section by immunofluorescence is a very promising visualization technique to study the distribution of stellate cells in the liver. In this study, water soluble carbon quantum dots that can emit blue, green and yellow fluorescence are synthesized by the hydrothermal method, and their sizes are 3.2, 3.7, and 4.3 nm, respectively. The three carbon quantum dots have good fluorescence stability, and the quantum yields are 36.1%, 26.3% and 21%, respectively. When the mass fraction of KCl in the blue carbon quantum dot dispersion system is 13%, it still maintains the liquid state at -30 °C. The final fluorescent probe is obtained after the carbon quantum dots are coupled with the secondary antibody, spectral characterizations confirm that the conjugate probe still maintains protein immunoactivity and has good stability. Cell experiments prove that the probe has good biocompatibility, the rabbit anti-mouse Desmin antibody is used as the primary antibody, the results of cellular immunofluorescence imaging and flow cytometry show that the probe can specifically label hepatic stellate cell at -20 °C. The results of liver frozen section experiments show that hepatic stellate cell can be specifically targeted and labeled by the fluorescent probe. This labeling technology provides an important technical means for elucidating the structure and function of the liver at the cellular level, exploring the liver pathological change, and designing and developing drug.

Simultaneous labeling and multicolor fluorescence imaging of multiple immune cells on liver frozen section by polychromatic quantum dots below freezing points.

A method for simultaneous labeling and multicolor fluorescence imaging of different hepatic immune cells below freezing point is established based on quantum dots. In the experiment, carbon quantum dots with emission wavelength of 435 nm, CdTe@CdS quantum dots at 542 nm and CdSe@ZnS quantum dots at 604 nm are synthesized respectively, it is found that when the mass fractions of KCl (as antifreeze) are 12 %, 14 %, and 12 %, respectively, the three quantum dot dispersion systems remain liquid state at -20 °C. After they are conjugated with the corresponding secondary antibodies, agarose gel electrophoresis, circular dichroism and capillary electrophoresis confirm the effectiveness of conjugation. By indirect immunofluorescence method, the above three quantum dot fluorescent probes are used to simultaneously and specifically target a variety of liver immune cells, and the multi-color simultaneous imaging of different liver immune cells is realized under the same excitation wavelength, it is found that hepatic macrophages are arranged radially in the liver, hepatic stellate cells present punctate distribution, and hepatic sinusoidal endothelial cells present circular distribution, which is consistent with the results of H&E staining and ultrathin section TEM. This study provides an important technical means for elucidating the structure and function of the liver.

State-of-the-Art Fluorescent Probes: Duplex-Specific Nuclease-Based Strategies for Early Disease Diagnostics.

Precision healthcare aims to improve patient health by integrating prevention measures with early disease detection for prompt treatments. For the delivery of preventive healthcare, cutting-edge diagnostics that enable early disease detection must be clinically adopted. Duplex-specific nuclease (DSN) is a useful tool for bioanalysis since it can precisely digest DNA contained in duplexes. DSN is commonly used in biomedical and life science applications, including the construction of cDNA libraries, detection of microRNA, and single-nucleotide polymorphism (SNP) recognition. Herein, following the comprehensive introduction to the field, we highlight the clinical applicability, multi-analyte miRNA, and SNP clinical assays for disease diagnosis through large-cohort studies using DSN-based fluorescent methods. In fluorescent platforms, the signal is produced based on the probe (dyes, TaqMan, or molecular beacon) properties in proportion to the target concentration. We outline the reported fluorescent biosensors for SNP detection in the next section. This review aims to capture current knowledge of the overlapping miRNAs and SNPs' detection that have been widely associated with the pathophysiology of cancer, cardiovascular, neural, and viral diseases. We further highlight the proficiency of DSN-based approaches in complex biological matrices or those constructed on novel nano-architectures. The outlooks on the progress in this field are discussed.

The Roadmap of Graphene-Based Sensors: Electrochemical Methods for Bioanalytical Applications.

Graphene (GR) has engrossed immense research attention as an emerging carbon material owing to its enthralling electrochemical (EC) and physical properties. Herein, we debate the role of GR-based nanomaterials (NMs) in refining EC sensing performance toward bioanalytes detection. Following the introduction, we briefly discuss the GR fabrication, properties, application as electrode materials, the principle of EC sensing system, and the importance of bioanalytes detection in early disease diagnosis. Along with the brief description of GR-derivatives, simulation, and doping, classification of GR-based EC sensors such as cancer biomarkers, neurotransmitters, DNA sensors, immunosensors, and various other bioanalytes detection is provided. The working mechanism of topical GR-based EC sensors, advantages, and real-time analysis of these along with details of analytical merit of figures for EC sensors are discussed. Last, we have concluded the review by providing some suggestions to overcome the existing downsides of GR-based sensors and future outlook. The advancement of electrochemistry, nanotechnology, and point-of-care (POC) devices could offer the next generation of precise, sensitive, and reliable EC sensors.

Detection of Matrix Metalloproteinase-1 in Human Saliva Based on a Pregnancy Test Strip Platform.

Matrix metalloproteinase (MMP) is closely correlated with tumorigenesis and progression. Establishing a low-cost, simple, rapid, and sensitive method for its detection is highly desired for the broad-spectrum screening of oral cancer. Herein, we combine the MMP-specific cleavage ability with magnetic separation technology and a commercial test strip to construct a sensitive biosensor to detect MMP-1 conveniently for the first time. The method involves two DNA probes, peptide-DNA1 and hCG-DNA2, where DNA1 and DNA2 are complementary sequences, and the peptide labeled with biotin can bind streptavidin-modified magnetic nanoparticles stably. The human chorionic gonadotropin (hCG) is the target of the pregnancy test strip. The cleavage reaction mediated by MMP-1 releases peptide-DNA1 and the hybridized hCG-DNA2 into the solution, and the hCG probe in the solution can develop color on the test strip for the determination of MMP-1 after magnetic separation. This method utilizes the high specificity of MMP-1's proteolytic cleavage and the high sensitivity of the test strip to the target probe, achieving a sensitive detection of MMP-1 with a visual detection limit of 65.5 pg/mL. The method shows better anti-interference and sensitivity than the enzyme-linked immunosorbent assay in the application of a biological sample matrix, suggesting its great potential for clinical diagnosis, especially for broad-spectrum oral cancer screening.

Terminal deoxynucleotidyl transferase associated with split G-quadruplex/hemin deoxyribozyme amplification detection for various contaminants in milk based on pregnancy test strip platform.

Contaminant residue analysis in milk can provide essential assistance for safety quality and contamination level management of milk production, which is critical for safeguarding public health. In this study, the pregnancy test strip is employed to achieve multiple analytes detection based on the specific recognition of aptamer and terminal deoxynucleotidyl transferase associated with split G-quadruplex/hemin deoxyribozyme system. Through the subsequent enzyme catalyzed reaction, the detection signal can be further amplified to improve the sensitivity. The method does not need to assemble test strip, prepare and purify antibodies/haptens, nor design complex probe sequences. By coupling human chorionic gonadotrophin with DNA probes and combining magnetic separation technology, the targets can be determined via the test strip. Under the optimized conditions, the visual detection limits for mercury ion, bisphenol A, and penicillin are 1, 0.1 and 0.05 nM, respectively. The detection results show that the method displays good accuracy and practicability in spiked milk sample. The method presents a simple scheme, low cost as well as good design versatility, which demonstrates great application prospect for the sensitive, low-cost, and convenient detection of food matrices.

Multifunctional nanocarrier with self-catalytic production of nitric oxide for photothermal and gas-combined therapy of tumor.

Single treatment often faces the problem that it cannot completely eradicate tumor and inhibit the tumor metastasis. In order to overcome this shortcoming, multi-modal tumor treatment has attracted widespread attention. In the present article, based on ascorbyl palmitate (PA) and l-arginine (l-Arg), a multifunctional nanocarrier is designed for synergetic treatment of tumor with photothermal and nitric oxide (NO) gas therapy. Firstly, PA and l-Arg were self-assembled to form novel functional micelles, PL, with high biosafety using electrostatic interaction and hydrogen bonding. The functional micelles could self-catalyze to produce NO at the tumor site. Then, Ag2S quantum dots having fluorescence imaging and photothermal properties were encapsulated to obtain the nanocarrier, A@PL. The results show that A@PL had a hydrated size of around 78 nm and presented good stability within 30 d. Moreover, in vitro studies indicate that it was efficient with regards to NO self-generating capacity, whereas the photothermal conversion efficiency was as high as 34% under near-infrared light irradiation. The cytotoxicity results show that, when the concentration of A@PL was as high as 2 mM, the survival rate of 3 T3 cells was still 78.23%, proving that the probe has good safety characteristics. Fluorescence imaging results show that its maximum enrichment can be achieved at the tumor site after tail vein injection for 3 h, and out of the body after 24 h, indicating good internal circulation. The in vivo studies show that the rate of inhibition of tumor using the nanocarrier was as high as 98%, and almost overcame the problem of tumor recurrence caused by single treatment, thus presenting a significant tumor treatment effect. This new multifunctional nanocarrier with self-catalytic production of NO provides a new idea for the efficient treatment of tumors.

CdTe@CdS quantum dots for labeling and imaging macrophages in liver frozen sections below the freezing point.

CdTe@CdS core-shell quantum dots with different particle sizes are synthesized by an aqueous method, and coating them with a CdS shell layer improves the quantum yield (36% → 59%) and fluorescence stability (37% → 77%) of CdTe@CdS quantum dots. When the KCl concentration (mass fraction) in the system is 15%, the CdTe@CdS quantum dot dispersion system remains in the liquid state at -20 °C, and the low temperature increases the fluorescence intensity. A QD-Ab probe is obtained after CdTe@CdS quantum dots are coupled with IgG; the circular dichroism shows that the IgG protein structure is not destroyed, while capillary electrophoresis, agarose gel electrophoresis and flow cytometry verify the conjugation efficiency. With rabbit anti-mouse EMR1 antibody as the primary antibody and QD-Ab as the secondary antibody, the hepatic macrophages in liver frozen sections are fluorescently labeled at -20 °C, and it is found that they are radially distributed in hepatic sinusoids with specific and highly efficient labeling; these results are verified by H&E staining and TEM. This technology can provide important technical support for in-depth understanding of the distribution of liver immune cells in the liver, and it can further provide a scientific basis to understand the relationship between the liver structure and function and pathological changes.

Extension of duplex specific nuclease sensing application with RNA aptamer.

Duplex specific nuclease (DSN) that can precisely cleave DNA portion in double-stranded DNA or DNA-RNA hybrid has engrossed immense attention owing to its great potential in emerging bioanalytical applications. Here, we present a novel approach to extend DSN sensing application by coupling RNA aptamer. Specially designed RNA ligand sequences are used to capture the target and simultaneously provide complementary sequences of DNA for DSN aided fluorescent signal enhancement. A clotting enzyme, thrombin, has been used as a model analyte. One RNA aptamer combined with the target molecule can generate fluorescent signals through cleavage of hybridized TaqMan DNA probe (P2) by DSN. The proposed assay has achieved the lowest detection limit of 0.039 pM. The assay has been applied for real-time detection of thrombin release from live cells and other biotic media for early disease diagnosis. The developed method is versatile and can detect various other targets by choosing the relevant aptamer and probe sequences. This method is promising to be applied to medical diagnosis, biosensing, food safety, environmental monitoring, and other fields.

Advancing interfacial properties of carbon cloth via anodic-induced self-assembly of MOFs film integrated with α-MnO2: A sustainable electrocatalyst sensing acetylcholine.

The metal organic frameworks (MOFs) with tunable composition, modified structure, and morphologically controlled nanoarchitectures are quite imperative to improve the electrochemical (EC) performances of sensing platforms. Herein, EC control over the fabrication of HKUST-1 (Cu-MOFs) nanocrystals is achieved via anodic-induced electrodeposition approach following the mixing of Cu2+ salt precursor in the vicinity of benzene-1,3,5-tricarboxylate (BTC3-) ligands. The problem of controlled mass transfer and slow dispersal of MOFs is resolved by EC deposition of pyramidal-octagonal MOFs on a highly conductive and flexible carbon substrate (activated carbon cloth, ACC) wrapped with rGO layers (ACC-rGO@Cu(BTC). Further, α-MnO2 is integrated on ACC-rGO@Cu(BTC) to achieve the synergistic effect of ternary structure interfaces. The novel ACC-rGO@Cu(BTC)@MnO2 based flexible electrode exhibits striking EC performance toward non-enzymatic sensing of acetylcholine (ACh) including wide linear range (0.1 µM - 3 mM), lowest detection limit (5 nM, S/N = 3), high selectivity, and long-term stability. Moreover, the developed sensing system has been applied for real-time detection of ACh efflux released from three different cell lines and biological matrices. Our work unlocks a new prospect of precisely structured MOFs with extensive functionalities and scaled-up fabrication methods via selection of nanoscale reaction centers to develop flexible sensing devices.

Controllable ion transport induced by pH gradient in a thermally crosslinked submicrochannel heterogeneous membrane.

Solid-state nanochannels have attracted considerable attention for their similar ion transport properties to biological ion channels. The construction of porous ion channels with good stability at the submicro/micrometer scale is very beneficial to develop large-area ion channel devices. In this manuscript, based on in-situ thermal crosslinking of a small organic molecule containing triphenylamine and styrene groups, we construct a heterogeneous membrane with asymmetrical charge and wettability on cylindrical anodic aluminum oxide (AAO) channels (D ≈ 319 nm). This heterogeneous membrane has typical ion current rectification characteristics with a high rectification ratio of 36.9 and good stability. This work provides an effective strategy for the construction of submicrochannel heterogeneous membranes and also broadens the application range of bionic ion channels.

Labeling of liver cells with CdSe/ZnS quantum dot-based fluorescence probe below freezing point.

In this paper, CdSe/ZnS quantum dots (QDs) with particle size of 5.5 ~ 9.3 nm were synthesized, and the fluorescence emission ranged from 545 ~ 616 nm. When the volume fraction of ethanol was 30%, the water-soluble QD dispersion system remained liquid under -20 °C freezing conditions, the fluorescence intensity increased with a decrease in temperature, and the quantum yield reached 79% at -20 °C. The endothelial cell adhesion molecule CD31 antibody (anti-CD31) was used as the primary antibody, QDs were coupled with IgG as the secondary antibody (QD-Ab), and effective labeling of hepatic sinusoid endothelial cells was achieved at -20 °C. Fluorescence imaging and flow cytometry analysis showed that the labeling efficiency was as high as 97%, indicating that QDs have an important application prospect in microscopic section tomography of the liver.

Quantitative analysis of various targets based on aptamer and functionalized Fe3O4@graphene oxide in dairy products using pregnancy test strip and smartphone.

Pregnancy test strips are one of the most mature and widely used commercial lateral flow devices used to determine pregnancy. Being a simple and rapid detection method, human chorionic gonadotropin (hCG) was used with different aptamers (hCG-apt) as probes for the detection of metal ions, small organic molecules, and proteins. Quantitative detection of target analytes was achieved using a smartphone app and a portable device developed in our laboratory. The results showed detection ranges of 1 nM-1 µM, 0.1 nM-10 µM and 32 nM-500 nM for Pb2+, chloramphenicol, and ß-lactoglobulin, respectively, and the corresponding visual detection limits in dairy products were 5 nM, 1 nM and 50 nM, respectively. Based on these results, rapid detection of multiple analytes can be realized through aptamer modification, thereby broadening the application range of commercial lateral flow devices for analysis of food chemistry.

Dual-aptamers labeled polydopamine-polyethyleneimine copolymer dots assisted engineering a fluorescence biosensor for sensitive detection of Pseudomonas aeruginosa in food samples.

To ensure the food security and protect public health, development of rapid and reliable approaches to detecting foodborne pathogens is of great significance. In this study, polydopamine-polyethyleneimine (PDA-PEI) copolymer dots are prepared via the self-polymerization of dopamine and cross-linking with branched PEI at room temperature. The PDA-PEI copolymer dots are very stable against photobleaching, extreme pH, as well as high ionic strength. They are used as a fluorescent probe to fabricate a biosensor for rapid and sensitive detection and quantification of Pseudomonas aeruginosa (P. aeruginosa). In the biosensor, dual-aptamers of P. aeruginosa are used to label PDA-PEI copolymer dots. Compared to single aptamer labeled PDA-PEI dots, the dual-aptamers labeled PDA-PEI dots endow the biosensor with enhanced sensitivity for target pathogen. The fluorescence biosensor demonstrates a wide linear response to P. aeruginosa in the concentration range of 101-107 cfu mL-1 with acceptable selectivity. The limit of detection is calculated to be 1 cfu mL-1. The whole detection process can be finished in 1.5 h. The feasibility of the fabricated biosensor is verified by successful determination of P. aeruginosa in skim milk, orange juice, and popsicle samples. The biosensor provides an alternative and attractive platform for rapid and sensitive detection of bacteria in food products.

Room temperature preparation of water-soluble polydopamine-polyethyleneimine copolymer dots for selective detection of copper ions.

Polydopamine-polyethyleneimine (PDA-PEI) copolymer dots were prepared under mild conditions via the self-polymerization of dopamine and cross-linking with branched PEI (BPEI). The molecular weight of BPEI, mass ratio of dopamine to BPEI, and pH of reaction medium had significant influences on the quantum yield of PDA-PEI copolymer dots. Under the optimized conditions, the synthesized PDA-PEI copolymer dots have an average size of 9.4 ±â€¯2.2 nm in diameter with good water dispersibility. The quantum yield is 12.5%. More importantly, they are very stable against extreme pH and high ionic strength. The PDA-PEI copolymer dots were employed as a fluorescent probe for sensitive and selective Cu2+ detection with a detection limit as low as 1.6 nM and a linear range from 0.0016 to 80 µM. The feasibility of the PDA-PEI copolymer dots-based method was verified by the successful determination of Cu2+ in water and oyster samples, demonstrating its potential for analysis of environmental water and food samples.

Graphene Oxide Quantum Dots Assisted Construction of Fluorescent Aptasensor for Rapid Detection of Pseudomonas aeruginosa in Food Samples.

We engineered an ingenious fluorescent aptasensor for detection of Pseudomonas aeruginosa ( P. aeruginosa) according to the DNA hybridization and fluorescence resonance energy transfer. In the absence of target bacteria, 5-carboxyfluorescein-labeled complementary DNA (FAM-cDNA) hybridizes with the partial sequences of aptamer and the fluorescence of FAM can be quenched by graphene oxide quantum dots (GOQDs). Upon the addition of target bacteria, the aptamer as a biorecognition element is bound with P. aeruginosa specifically. FAM-cDNA prefers to hybridize with the aptamer, resulting in the desorption of FAM-cDNA from GOQDs, thus recovering the fluorescence of FAM. The aptasensor shows a wide linear response to P. aeruginosa in the concentration range of 1.28 × 103-2.00 × 107 cfu/mL with acceptable selectivity. The detection limit is 100 cfu/mL. The whole process can be finished in 2 h. Moreover, the platform is successfully applied to detect P. aeruginosa in drinking water, orange juice, and popsicle samples.