Filter-Assisted Separation of Multiple Nanomaterials: Mechanism and Application in Atomic/Mass Spectrometry/Fluorescence Label-Free Multimode Bioassays.

Atomic spectrometry (AS) has been widely used in bioassay, but it requires steps to immobilize or separate the signal molecules. In this work, based on the phenomenon that the filter membrane can selectively separate multiple nanomaterials (nanoparticles (NPs) and quantum dots (QDs)) and its related ions, including poly(thymine)-templated Cu NPs and free Cu2+, Ag NPs and free Ag+, CdTe QDs and Cd2+, we constructed multimode and label-free biosensors by chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS), inductively coupled plasma mass spectrometry (ICP-MS), and fluorescence. In this strategy, terminal deoxynucleotidyl transferase (TdT) and polynucleotide kinase (PNK), H2O2, and mucin 1 can be sensitively detected using Cu2+, Ag+, and Cd2+ as the signal probe, respectively. As a result, TdT and T4 PNK in single cells level can be accurately quantified. In addition, the possible separation mechanism of filter membrane was proposed, both Donnan repulsion by charged functional layer and entrapment effect by nanomaterials size contributed to the outstanding separation performance. Subsequently, on the basis that CdTe QDs can selectively identify Cu NPs/Cu2+, Ag NPs/Ag+, and C-Ag+-C/Ag+, cation-exchange reaction (CER) was introduced in this platform due to its unique advantages, including improving the sensitivity of the above system (an order of magnitude), converting the non-CVG metal elements into CVG elements, and using low-cost AFS to substitute the high-cost ICP-MS. In addition, we performed theoretical calculations of the selective CER using density functional theory (DFT). Therefore, this label-free and simple separation AS/ICP-MS sensing platform shows great potential for biomarker analysis.

Visual/CVG-AFS/ICP-MS multi-mode and label-free detection of target nucleic acids based on a selective cation exchange reaction and enzyme-free strand displacement amplification.

Conventional atomic spectrometry biosensors usually require labeling and separation of signaling molecules. Visual assays have direct and effective characteristics; however, they have poor accuracy. We intended to improve the analytical performance of our previous work and simplify the experimental operation while maintaining the advantages of simple operation and low cost. Herein, we describe the development of a visual, chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS) and inductively coupled plasma-mass spectrometry (ICP-MS) three-mode method for the analysis of nucleic acids via CdTe quantum dot (QD)-assisted selective cation exchange reaction and enzyme-free strand displacement amplification. This work mainly utilized the ability of CdTe QDs to selectively differentiate free Hg2+ from the T-Hg2+-T complex in addition to the simple selective membrane filtration separation of Cd2+ from CdTe QDs to improve the performance of label-free bioassay methods. Due to the superior optical features of CdTe QDs, they can not only be used as a signal molecule for atomic spectroscopy, but also for direct use in visual readings. Under optimal experimental conditions, the developed strategy displayed a wide linear range along with limits of detection (LODs) of 10 fM and 3 fM (2 fM) in the linear concentration ranges of 10 fM-100 pM and 10 fM-1 nM with the naked eye and CVG-AFS (ICP-MS) assays, respectively. This method also exhibited excellent DNA sequence specificity. This assay had advantageous characteristics such as an easy operation, simple design, high sensitivity, and diversified signal readout manner, which demonstrate its great potential in medical diagnosis applications.

Periodontopathogens Porphyromonas gingivalis and Fusobacterium nucleatum and Their Roles in the Progression of Respiratory Diseases.

The intricate interplay between oral microbiota and the human host extends beyond the confines of the oral cavity, profoundly impacting the general health status. Both periodontal diseases and respiratory diseases show high prevalence worldwide and have a marked influence on the quality of life for the patients. Accumulating studies are establishing a compelling association between periodontal diseases and respiratory diseases. Here, in this review, we specifically focus on the key periodontal pathogenic bacteria Porphyromonas gingivalis and Fusobacterium nucleatum and dissect their roles in the onset and course of respiratory diseases, mainly pneumonia, chronic obstructive pulmonary disease, lung cancer, and asthma. The mechanistic underpinnings and molecular processes on how P. gingivalis and F. nucleatum contribute to the progression of related respiratory diseases are further summarized and analyzed, including: induction of mucus hypersecretion and chronic airway inflammation; cytotoxic effects to disrupt the morphology and function of respiratory epithelial cells; synergistic pathogenic effects with respiratory pathogens like Streptococcus pneumoniae and Pseudomonas aeruginosa. By delving into the complex relationship to periodontal diseases and periodontopathogens, this review helps unearth novel insights into the etiopathogenesis of respiratory diseases and inspires the development of potential therapeutic avenues and preventive strategies.

Constructing a defect-rich hydroxide nanoenzyme sensor based on dielectric barrier discharge microplasma etching for sensitive detection of thiamine hydrochloride and hydrogen peroxide.

In this work, a novel approach was designed to fabricate a defect-rich hydroxide nanoenzyme sensor based on transition metal cobalt derived from metal-organic framework (MOF). Facile preparation was realized by room-temperature reaction and chemical etching via dielectric barrier discharge (DBD) microplasma, which possesses great chemical reactivity to obtain defect-rich and ultrathin structures. The prepared cobalt hydroxide (Co(OH)2) emerges with superior catalytic activity for thiamine hydrochloride (TCL) and hydrogen peroxide (H2O2) assay. The linear ranges were 0.0006 mM to 2.75 mM for TCL detection and 0.001 mM to 5.5 mM for H2O2 detection with low limit of detections (LODs) of 14 nM and 93 nM, respectively. Meanwhile, the as-prepared sensor provides excellent long-term durability (>25 days), as well as high sensitivity (12730 µA mM-1cm-2 and 5199.3 µA mM-1 cm-2) for TCL and H2O2 assay. TCL in serum samples has been detected with satisfactory results by the proposed material, while the H2O2 in Hela cells was also successfully measured. The developed sensor provides several advantages including simplicity, high sensitivity, and efficient preparation.

The Impact of Smoking on Subgingival Plaque and the Development of Periodontitis: A Literature Review.

Smoking seriously affects oral health and causes a variety of oral diseases. Numerous clinical data show that smoking significantly increases the risk of periodontitis, and the duration and amount of smoking are positively correlated with the severity of periodontitis. In fact, smoking creates an environment conducive to the colonization of periodontopathogens, which affects the process of periodontitis. Since subgingival plaque which harbors periodontopathogens is the initiation factor of periodontitis, it is critical to study the impact of smoking on subgingival microbiota for understanding the relationship between smoking and periodontitis. Continuous advances have been made on the understanding of effects of smoking on subgingival plaque and the development of periodontitis. Smoking is observed to enhance the pathogenicity of periodontopathogens, especially the red complex microorganisms, via promoting their colonization and infection, and regulating the expression and function of multiple virulence factors. Furthermore, smoking has a negative impact on periodontal microecological homeostasis, which is reflected in the decrease of commensal bacteria and the increase of periodontopathogens, as well as the changes in the interaction between periodontopathogens and their commensal microbes in subgingival biofilm, thus influencing the pathogenicity of the subgingival plaque. In summary, the mechanism of smoking on subgingival plaque microorganisms represented by the red complex and its effect on the periodontal microecology still need to be further explored. The relevant research results are of great significance for guiding the periodontal clinical treatment of smoking population. This review summarizes the effects and relevant mechanisms of smoking on subgingival plaque and the development of periodontitis.

Thiol inhibition of Hg cold vapor generation in SnCl2/NaBH4 system: A homogeneous bioassay for H2O2/glucose and butyrylcholinesterase/pesticide sensing by atomic spectrometry.

Recently, the use of atomic spectrometry (AS) for biochemical analysis has attracted considerable attention due to its high sensitivity, selectivity and anti-interference ability. In this work, we conducted a detailed study on a phenomenon of thiol inhibition of mercury (Hg2+) cold vapor generation (CVG) and found L-cysteine (L-Cys), glutathione (GSH), dithiothreitol, N-Acetyl-L-cysteine, 3-mercaptopropionic acid, ß-mercaptoethanol, and NaI can inhibit the CVG of Hg2+, while EDTA has no inhibitory effect. Furthermore, changing the content of -SH can effectively adjust the CVG atomic fluorescence spectrometer (CVG-AFS) signal of Hg2+. As as a consequence, an AS-based homogeneous bioassay was constructed by adjusting the oxidation ratio and production quantity of -SH in the system. The quantitative analysis of the system was demonstrated by using AFS as a representative detector. Hydrogen peroxide (H2O2) and glucose were used as representative analytes for the validation of Hg2+ atomic fluorescence signal turn-off strategy, and butyrylcholinesterase (BChE) as well as parathion (organophosphorus pesticides, OPs) as utilized as representative targets for the signal turn-on strategy. Under optimal experimental conditions, the homogeneous CVG-AFS sensor can be successfully used to detect 3 µM H2O2, 30 µM glucose, 0.25 U/L BChE, and 0.4 µg/mL parathion. In addition, the detection results of glucose and BChE in human serum samples agreed well with those obtained by using glucometer and kit, showing the promising potential of this method for practical applications. Therefore, this work provides a perspective for the construction of AS-based homogeneous bioassays and shows great potential for the detection of biomarkers.

Selective recognition of CdTe QDs and strand displacement signal amplification-assisted label-free and homogeneous fluorescence assay of nucleic acid and protein.

Due to their simplicity of design and operation, homogeneous bioassays have been of great interest to researchers. Herein, a label-free and free separation fluorescence sensing platform was constructed for the determination of nucleic acid and prostate specific antigen (PSA) using CdTe QDs as the signal molecule. In our previous work, we surprisingly found that the CdTe QDs can selectively distinguish Ag+ and the C-Ag+-C complex, which was the basis of the sensor. On the basis of the selective cation exchange reaction (CER), combined with the signal amplification of the strand displacement reaction (SDR), this work was first applied for the sensitive analysis of DNA. There are two types of hairpin structures in this sensing system, including the recognition probe (HP) and Ag+, which formed the C-Ag+-C structure, and the hairpin structure formed by the helper DNA itself. In this work, target DNA can trigger the SDR that generates lots of HP-helper double-stranded DNA (dsDNA) and recycles the target DNA while releasing a large amount of Ag+, thus quenching the fluorescence signal of CdTe QDs to achieve the highly sensitive detection of DNA. In order to verify the versatility of this system using DNA as a bridge and aptamers as recognition probes, we extended the system to the detection of PSA. After examining its experimental performance, it was determined that this method displayed good analytical capability for DNA in the range of 10-13-10-10 M and PSA in the range of 10-13-10-10 g mL-1 with low 25 fM and 30 fg mL-1 limits of detection (LODs), respectively; high selectivity for both the target sequence and protein was shown. In addition, this platform was successfully used for the analysis of PSA in serum samples.

A Fluorescence Strategy for Silver Ion Assay via Cation Exchange Reaction and Formation of Poly(thymine)-templated Copper Nanoclusters.

The detection of Ag+ ions in the environment and biological systems is important to both environmental monitoring and modern medicine. Herein, a novel and label-free method was developed for Ag+ detection, which utilizes a florescence strategy combining DNA-templated copper nanoclusters (Cu NCs) with cation exchange reactions. The method is primarily based on the effective detection of an Ag+-triggered cation exchange reaction and the release of free Cu2+ from CuS nanoparticles (CuS NPs), while the probe T30 serves as an effective template for the formation of fluorescence-inducing Cu NCs. Under optimal conditions, this sensing system displays high sensitivity with a 50 nM limit of detection and a range from 0 - 100 µM. In addition, the proposed method exhibits high selectivity and, therefore, was successfully applied to the analysis of real samples. Overall, these results demonstrate that our established method has advantages of design and operation simplicity, as well as cost-effectiveness.

Multimode MicroRNA Sensing via Multiple Enzyme-Free Signal Amplification and Cation-Exchange Reaction.

The detection of biomarkers requires not only high sensitivity but also different signal reading methods depending on the actual situation. Herein, the luminescent properties of CdTe quantum dots (QDs) were exploited, where CdTe QDs were used as shared signal molecules. Combining multiple types of nucleic acid and chemical signal amplification techniques, and various signal detection techniques, a magnetic nanoparticle (NP) and filter-assisted separation multimode sensing strategy has been developed. In this work, miRNA-141 was selected as a representative target, which can trigger the catalyzed hairpin assembly and hybrid chain reaction enzyme-free nucleic acid signal amplification that generates long double-stranded DNA. Subsequently, the chemical amplification of silver NPs (Ag NPs) that release a large amount of Ag+ was introduced into the system. Finally, the cation-exchange reaction between CdTe QDs and Ag+ was utilized to quench the fluorescence (FL) of the CdTe QDs, releasing free Cd2+. The visual/FL/chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS)/inductively coupled plasma mass spectrometry (ICP-MS) method could then be performed for the analysis of miRNA. After investigating its experimental performance, it has been found that 10 fM can be differentiated from the blank solution with the naked eye. In addition, FL/CVG-AFS/ICP-MS methods all displayed good analytical capability for target detection, and the limits of detection (LODs) are as low as fM, which show high target sequence selectivity. This platform was applied to investigate miRNA-141 expression in various cancer cells, which can accurately detect in the range of 100-100 000 MDA-MB-231 cells (breast cancer cell lines), with an LOD of 15 cells. Therefore, the multimode sensing strategy based on a single signal molecule and multiple signal amplification strategies is an applicable and versatile detection method of biomarkers; it can even achieve point-of-care testing, improving the accuracy and efficiency of medical diagnosis.

Detection of nucleic acids via G-quadruplex-controlled l-cysteine oxidation and catalyzed hairpin assembly-assisted signal amplification.

The development of simple, sensitive and cost-effective methods for specific nucleic acid detection has attracted tremendous attention due to its importance to the early diagnosis of genetic diseases and to biodefense applications. In this work, we demonstrated a fluorescent turn-off mode DNA assay based on l-cysteine-modulated synthesis of CdTe quantum dots (CdTe QDs), horseradish peroxidase-mimicking G-quadruplex-hemin-K+ complex controlled oxidation of l-cysteine to cystine, and catalyzed hairpin assembly (CHA)-assisted signal amplification. After the addition of target DNA, the CHA signal amplification reaction was triggered and numerous H1-H2 double-stranded DNA were formed, initiating the release of G-quadruplex sequences in H2 simultaneously. Thus, the degree of inhibition of the synthesis of CdTe QDs is proportional to the concentration of the G-quadruplex sequence in this method. In contrast, when the target DNA was absent, the CHA could not be triggered, and the fluorescence signal was high due to the remaining intact l-cysteine. Under optimal experimental conditions, the homogeneous fluorescence method achieved the detection of HIV DNA with a linear range from 0.1 pM to 1 nM and a detection limit of 0.12 pM. This novel biosensor exhibits excellent specificity in differentiating DNA sequences with a single-base and two-base mismatch. To the best of our knowledge, this a label-free and highly sensitive bioassay utilizing CHA-assisted signal amplification and G-quadruplex control of in situ synthesis of CdTe QDs strategy was not reported in previous. Thus, this proposed strategy is anticipated to find use in basic biochemical research and clinical diagnosis.