Inertial and Deterministic Lateral Displacement Integrated Microfluidic Chips for Epithelial-Mesenchymal Transition Analysis.

With the aim of efficiently sorting rare circulating tumor cells (CTCs) from blood and minimizing damage to CTCs during isolation, we constructed an inertia-assisted single-cell focusing generator (I-SCF) and a water droplet deterministic lateral displacement cell sorting (D-DLD) microfluidic system (IDIC) based on different sizes, the device is initially sorted by a continuous fluid swing and Dean flow-assisted helical micromixers, then flows through a droplet shaped DLD region, enabling single-cell focused sequencing and precise separation, improving cell separation efficiency (>95%) and purity, while ensuring a high single cells survival rate of more than 98.6%. Subsequently, breast cancer cell lines were run through our chip, and then the downstream epithelial-mesenchymal transition (EMT) process induced by TGF-ß was detected, and the levels of three proteins, EpCAM, PD-L1, and N-cadherin, were analyzed to establish the relationship between PD-L1 and the EMT process. Compared with other analytical techniques such as the filtration method, the enrichment method and immunoaffinity capture methods, this method not only ensures the separation efficiency and purity, but also ensures the cell activity, and avoids missing the different results caused by the heterogeneity of CTCs due to the isolation of high purity (84.01%). The device has a high throughput processing capacity (5 mL of diluted whole blood/∼2.8 h). By using the chip, we can more easily and conveniently predict tumor stage and carry out cancer prevention and treatment in advance, and it is expected to be further developed into a clinical liquid biopsy technology in the future.

Comparative efficacy of tezepelumab to mepolizumab, benralizumab, and dupilumab in eosinophilic asthma: A Bayesian network meta-analysis.

BACKGROUND: It is unclear how the efficacy of tezepelumab, approved for the treatment of type 2 high and low asthma, compares to the efficacy of other biologics for type 2-high asthma. OBJECTIVES: We sought to conduct an indirect comparison of tezepelumab to dupilumab, benralizumab, and mepolizumab in the treatment of eosinophilic asthma. METHODS: The investigators conducted a systematic review and Bayesian network meta-analyses. They identified randomized controlled trials indexed in PubMed, Embase, or Cochrane Central Register of Controlled Trials (CENTRAL) between January 1, 2000, and August 12, 2022. Outcomes included exacerbation rates, prebronchodilator FEV1, and the Asthma Control Questionnaire. RESULTS: Ten randomized controlled trials (n = 9201) met eligibility. Tezepelumab (relative risk: 0.63; 95% credible interval [CI]: 0.46-0.86) was associated with significantly lower exacerbation rates than benralizumab and larger improvements in FEV1 compared to mepolizumab (mean difference [MD]: 66; 95% CI: -33 to 170) and benralizumab (MD: 62; 95% CI: -22 to 150), though the 95% CI crossed the null value of 0. Mepolizumab improved the Asthma Control Questionnaire score the most, but this improvement was not significantly different from that of tezepelumab (tezepelumab vs mepolizumab; MD: 0.14; 95% CI: -0.10 to 0.38). For efficacy by clinically important thresholds, tezepelumab, mepolizumab, and dupilumab achieved a >99% probability of reducing exacerbation rates by ≥50% compared to placebo, but benralizumab had only a 66% probability of doing so. Tezepelumab and dupilumab had a probability of 1.00 of improving prebronchodilator FEV1 by ≥100 mL above placebo. Compared to mepolizumab, dupilumab had >90% chance for improving FEV1 by ≥50 mL, but none of the differences between biologics exceeded 100 mL. CONCLUSIONS: In individuals with eosinophilic asthma, tezepelumab and dupilumab were associated with greater improvements (although below clinical thresholds) in exacerbation rates and lung function than benralizumab or mepolizumab.

Single Cell Phenotypic Analysis for Cancer Stem Cell Identification by Dual-Isotope ICP-QMS.

Single cell phenotypic analysis is significant for clinical diagnosis, treatment, and prognosis of cancer. Accurate differentiation of cancer stem cell (CSC) subpopulations from a large number of cancer cells may become a cancer surveillance tool and provide important implications for the development of new CSC-targeted therapy strategies. Herein, we report a new approach based on dual-isotope inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for single cell phenotypic analysis. High-throughput single cell sampling was achieved by a spiral channel microfluidic chip for cell focusing and alignment, and single cell analysis was performed with time-resolved ICP-QMS by identifying the highly specific probes. This enables the monitoring of two surface protein markers (EpCAM and MUC1) of three cell types, i.e., HeLa, MCF-7, and HepG2, at single cell level. The analysis of breast cancer stem cells further confirmed its capability in distinguishing rare cell phenotypes. The present study provides promising possibilities for adopting ICP-QMS in biomedical investigations in terms of cell typing, stemness identification of tumor cells, and cell heterogeneity analysis.

Dean-Flow-Coupled Elasto-Inertial Focusing Accelerates Exosome Purification to Facilitate Single Vesicle Profiling.

Exosomes are recognized as noteworthy biomarkers playing unprecedented roles in intercellular communication and disease diagnosis and treatment. It is a prerequisite to obtain high-purity exosomes for the comprehension of exosome biochemistry and further illustration of their functionality/mechanisms. However, the isolation of nanoscale exosomes from endogenous proteins is particularly challenging for small-volume biological samples. Herein, a Dean-flow-coupled elasto-inertial microfluidic chip (DEIC) was developed. It consists of a spiral microchannel with dimensional confined concave structures and facilitates elasto-inertial separation of exosomes with lower protein contaminants from cell culture medium and human serum. The presence of 0.15% (w/v) poly-(oxyethylene) controls the elastic lift force acting on suspended nanoscale particles and makes it feasible for field-free purification of integrity exosomes with a 70.6% recovery and a 91.4% removal rate for proteins. As a proof of concept, the technique demonstrated the individual-vesicle-level biomarker (EpCAM and PD-L1) profiling in combination with simultaneous aptamer-mediated analysis to disclose the sensibility for immune response. Overall, DEIC enables the collection of high-purity exosomes and exhibits potential in integration with downstream analyses of exosomes.

Two-Dimensional Multi-parameter Cytometry Platform for Single-Cell Analysis.

A 2D flow cytometry platform, known as CytoLM Plus, was developed for multi-parameter single-cell analysis. Single particles or cells after hydrodynamic alignment in a microfluidic unit undergo first-dimension fluorescence and side scattering dual-channel optical detection. They were thereafter immediately directed to ICP-MS by connecting the microfluidic unit with a high-efficiency nebulizer to facilitate the second-dimension ICP-MS detection. Flow cytometry measurements of fluorescent microspheres evaluated the performance of CytoLM Plus for optical detection. 6434 fluorescence bursts were observed with a valid signal proportion as high as 99.7%. After signal unification and gating analysis, 6067 sets of single-particle signals were obtained with 6.6 and 6.2% deviations for fluorescence burst area and height, respectively. This is fairly comparable with that achieved by a commercial flow cytometer. Afterward, CytoLM Plus was evaluated by 2D flow cytometry measurement of Ag+-incubated and AO-stained MCF-7 cells. A program for 2D single-cell signal unification was developed based on the algorithm of screening in lag time window. In the present case, a lag time window of -4.2 ± 0.09 s was determined by cross-correlation analysis and two-parameter optimization, which efficiently unified the concurrent single-cell signals from fluorescence, side scattering, and ICP-MS. A total of 495 sets of concurrent 2D signals were screened out, and the statistical analysis of these single-cell signals ensured 2D multi-parameter single-cell analysis and data elucidation.

Interaction of Cellular Uptake of Nanosilver and Metallothionein Stress Expression Elucidated by 2D Single-Cell Analyses Based on LIF and ICP-MS.

The exploration of cytology mechanisms of nanosilver uptake, toxicity, and detoxification has become an important issue due to its widespread applications. Previous studies have shown differences in the toxic response of mammalian cells to nanosilver. However, the analysis results based on cell populations ignore the impact of cell uptake heterogeneity on the expression of associated stress proteins and cellular physiological activities. In this respect, this work investigated the interaction between silver uptake and metallothionein (MT) expression in individual cells. In addition, we have also preliminarily elucidated the sensitivity variation to AgNPs by using five cell lines, e.g., LX-2, HepG-2, SK-HEP-1, Huh-7, and MDA-MB-231, by adopting a two-dimensional (2D) high-throughput single-cell analysis platform coupling laser-induced fluorescence (LIF) and inductively coupled plasma mass spectrometry (ICP-MS). We developed a 2D data analysis method for one-to-one unification of fluorescence-mass spectrometry signals corresponding to a specific single cell. It indicated that there is no obvious correlation between cellular silver uptake and cell size, and the low MT expression of cells is more sensitive to silver nanoparticles. For each cell line, significant heterogeneity in MT expression was observed. This provides important information for understanding the potential heterogeneous effects of nanosilver on mammalian biological systems. Overall, detoxified cells are more tolerant to nanosilver and normal cells are more tolerant than cancer cells.

Lumi-HOF@Tb as Probes for Multiple Ratiometric Fluorescence and Chemiluminescence Sensing of α-Glucosidase.

The innovative assembly of luminescent hydrogen-bonded organic frameworks (HOFs) into multifunctional optical sensors is of great significance for developing advanced materials. Herein, we report a facile room-temperature synthesis strategy for the luminol HOF modified by Tb3+ (Lumi-HOF@Tb) and featuring sensitive chemiluminescence and fluorescence characteristics. Lumi-HOF@Tb is further pioneered as a dual-signal sensor for selective detection of α-glucosidase, a type of enzyme that plays a crucial role in the digestion of carbohydrates, and screening of its inhibitors. The sensor is constructed by combining the dual optical characteristics of luminol from the HOF and lanthanide ion assistance. From the hydrolysis of α-glucosidase and the 4-nitrophenyl-α-d-glucopyranoside (pNGP) substrate emerges the fluorescent luminol-p-nitrophenol (pNP) complex at 466 nm and changes the inner filter absorption to recover Tb3+ characteristic fluorescence at 546 nm; luminol also produces a chemiluminescence signal driven by H2O2 from additional glucose oxidase-catalyzed hydrolysis of α-d-glucose. Fluorescence and chemiluminescence assays for α-glucosidase activity have therefore been established and exhibit detection limits as low as 0.04 and 0.005 U L-1, respectively. This study not only presents the possibility of Ln3+-HOF-based sensors as intelligent optical materials by integration of fluorescence and chemiluminescence techniques but also demonstrates great potential for future applications in biosensing.

Insights into Surface Charge of Single Particles at the Orifice of a Nanopipette.

The dynamic behaviors of particles in various physical fields are related to the physicochemical properties of particles. Herein, we focus on the relationship between surface charge and dynamic behaviors of particles at the orifice of a nanopipette. We interestingly find that angle θ, a parameter related to the asymmetric degree of current spike, exhibits a strong relationship with surface charge of the particles. Both theoretical derivation and finite element simulation validate this relationship and thus could be used for quantifying the surface charge of single particles. Moreover, the gold and silica nanoparticles with the same size but different surface charges could be well distinguished and identified based on this relationship. This study not only gives a comprehensive understanding on the dynamic behaviors of particles outside the nanopipette but also opens a new way for investigating the surface charge of single particles.

Cryogenic Laser Ablation in a Rapid Cooling Chamber Ensures Excellent Elemental Imaging in Fresh Biological Tissues.

Laser ablation inductively coupled plasma mass spectrometry imaging of biologically significant targets largely relies on maintaining the original structures of samples. The temperature regulation capability of the ablation cell is crucial. Herein, a rapid cooling cryogenic sample cell (RCCSC) was developed. In the RCCSC chamber, the temperature reduces to -20 °C in 4 min with a minimum 10 h variation of ±0.1 °C at -26 °C. Improvements on the precision were achieved for the elements of interest in NIST 612 and spiked agarose gel under cryogenic conditions. The limits of detection improved by up to 1.57, 1.70, 3.26, and 1.33 fold for 63Cu, 66Zn, 57Fe, and 140Ce in agarose gel, respectively, were obtained under cryogenic conditions compared with those at room temperature. In a time period of testing (10 h), the cryogenic ablation maintains the native state of biological tissues with a high water content to ensure better elemental imaging by reducing thermal effects in ablation and suppressing evaporation of water. The rapid cooling cryogenic ablation significantly improves elemental imaging, as demonstrated by the imaging of various elements in coriander leaves. The present study may provide further insights into elemental distributions in fresh biological samples.

The Impact of Human Papillomavirus Infection on Skin Cancer: A Population-Based Cohort Study.

BACKGROUND: This study investigated the correlation between a history of human papillomavirus (HPV) infection and skin cancer risk. MATERIALS AND METHODS: The study cohort comprised 26,919 patients with newly diagnosed HPV infection between 2000 and 2012; with the use of computer-generated numbers, patients without previous HPV infection were randomly selected as the comparison cohort. The patients in the HPV infection cohort were matched to comparison individuals at a 1:4 ratio by demographic characteristics and comorbidities. All study individuals were followed up until they developed skin cancer, withdrew from the National Health Insurance program, were lost to follow-up, or until the end of 2013. The primary outcome was subsequent skin cancer development. Cox proportional hazards regression analysis was used to analyze the risk of skin cancer with hazard ratios (HRs) and 95% confidence intervals (CIs) between the HPV and control cohort. RESULTS: The adjusted HR of skin cancer for patients with HPV relative to controls was 2.45 after adjusting sex, age and comorbidities. (95% CI, 1.44-4.18, p < .01). The subgroup analysis indicated that a patient with HPV infection had a significantly greater risk of skin cancer if they were aged >40 years. Notably, a risk of skin cancer was found in the group diagnosed with HPV within the first 5 years after the index date (adjusted HR, 3.12; with 95% CI, 1.58-5.54). Sensitivity analysis by propensity score, matching with balanced sex, age, and comorbidities, showed consistent results. CONCLUSION: A history of HPV infection is associated with the development of subsequent skin cancer in Taiwanese subjects, and the risk wanes 5 years later. IMPLICATIONS FOR PRACTICE: In this Taiwan nationwide cohort study, there was a 2.45-fold increased risk of developing new-onset skin cancers for patients with incident human papillomavirus (HPV) infection, compared with the matched controls. Furthermore, the risk was noticeably significant among patients aged >40 years. A prominent risk of skin cancers was found in the group diagnosed with HPV within the first 5 years after the index date in this study. The results of this analysis may raise consensus on the effect of HPV infection on the risk of skin cancers. Clinicians are encouraged to implement prudently on the differential diagnosis of skin cancers and HPV prevention and treatment, especially in older patients.

Two-Dimensional Cytometry Platform for Single-Particle/Cell Analysis with Laser-Induced Fluorescence and ICP-MS.

A two-dimensional cytometry platform (CytoLM) with high sensitivity and high temporal resolution is developed for single-particle and single-cell sampling and analysis. First, a Dean flow-assisted vortex capillary cell sampling (VCCS) unit confines the sample stream in curved flow and drives to focus and align the particles or cells in a small probe volume. By coupling VCCS to a laser-induced fluorescence (LIF) detector with data acquisition and processing capability, a high-throughput single-particle/cell analysis system (VCCS-LIF) was established. The particle analysis throughput of 119.42/s and a detection recovery of 78.20 ± 1.75% were achieved at a density of 9.16 × 104/mL for fluorescent particles, and the cell analysis throughput is 48.20/s at a density of 1.5 × 105/mL. Second, the CytoLM platform is constructed by hyphenating VCCS-LIF with inductively coupled plasma mass spectrometry (ICP-MS). In the analysis of HepG2 cells by Ag+ incubation and AO staining, 10,760 fluorescence bursts and 3068 MS events were observed in 240 s. Invalid signals due to undispersed cells were controlled at 3.80% for LIF and 1.01% for MS, with a proportion of effective signal of >96.20%. After peak identification and integral processing of the original data, the statistical results including peak area, height, width, and spacing are obtained concurrently and the information on concentration and elemental quantification of single cells is evaluated. CytoLM facilitates high-throughput, multi-dimensional, and multi-parameter characterization of particles and cells, and it may provide vast potential in life science analysis.

Human papillomavirus symptomatic infection associated with increased risk of new-onset alopecia areata: A nationwide population-based cohort study.

BACKGROUND: We investigated the correlation between a history of human papillomavirus (HPV) infection and alopecia areata risk. METHODS: The study cohort comprised 30,001 patients with newly diagnosed HPV infection between 2000 and 2012; and with use of computer-generated randomly numbers, patients not had HPV infection were randomly selected as the comparison cohort. HPV infection cohort were matched to comparison individuals at a 1:1 ratio by age, gender and index year. All study individuals were followed up until they developed alopecia areata, withdraw from the insurance program, lost to follow-up, or until the end of 2013. Cox proportional hazards regression analysis was used to analyze the risk of alopecia areata with hazard ratios (HRs) and 95% confidence intervals (CIs) between the HPV and control cohort. RESULTS: The adjusted hazard ratio (aHR) of alopecia areata for HPV patients relative to controls was 2.55 (95% C.I. = 1.88-3.47) after adjusting sex, age and comorbidities. Subgroup analysis indicated that patients with HPV infections had a significantly greater risk of alopecia areata for both genders, all age subgroups, and those with mental disorder diseases. CONCLUSIONS: A history of HPV infection is associated with the development of subsequent alopecia areata in Taiwanese subjects.

Tonsillectomy and the subsequent risk of psoriasis: A nationwide population-based cohort study.

BACKGROUND: Tonsillectomy has been suggested as an intervention to resolve psoriasis. OBJECTIVE: This study aimed to investigate the subsequent risk of psoriasis in patients who received tonsillectomy. METHODS: We used data from the Taiwan National Health Insurance Research Database. The tonsillectomy group (case group) and the tonsillectomy-free group (comparison group) were matched at a ratio of 1:4 by demographic data, comorbidities, medical confounders, and the index date. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: We identified 2021 patients as the case group and matched 8084 individuals as the comparison group. The adjusted HR (aHR) of psoriasis was 0.43 (95% CI, 0.22-0.87; P < .05). The study population is composed of a mainly male (65%) and young population (mostly younger than 50 years). Notably, patients with rheumatoid arthritis increased the risk of psoriasis (aHR, 3.97; 95% CI, 1.17-13.48; P < .05). In our stratification analysis, the risk of psoriasis decreased in almost all subgroups. LIMITATION: Our database did not include information on genome and the subtypes of psoriasis. CONCLUSION: Our study showed a decreased risk of psoriasis in the tonsillectomy group after adjustment for baseline characteristics, comorbidities, and medical confounders compared with the reference group.

Dual-mode imaging of copper transporter 1 in HepG2 cells by hyphenating confocal laser scanning microscopy with laser ablation ICPMS.

Copper transporter 1 (CTR1) is a transport protein involved in copper and cisplatin uptake. The visualization of cellular CTR1 migration and its redistribution is highly important in copper/cisplatin exposure/transport. However, to the best of our knowledge, this is a highly challenging task. Herein, a dual-mode imaging strategy for CTR1 is developed by hyphenating confocal laser scanning microscopy (CLSM) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) with a fluorescent/elemental bifunctional tag conjugated with anti-CTR1 antibody. The tag consists of rhodamine B and zirconium metal-organic frameworks (Zr-MOF) for CLSM fluorescence imaging and LA-ICPMS element imaging for a same group of HepG2 cells in a designated visual zone. This dual-mode imaging strategy facilitates visualization of CTR1 migration and meanwhile provides information of CTR1 redistribution in HepG2 cells by uptake of divalent copper or cisplatin. The present dual-mode imaging strategy provides in-depth information for the elucidation of CTR1 involved biological processes. Graphical abstract.

Titanium dioxide-functionalized dendritic mesoporous silica nanoparticles for highly selective isolation of phosphoproteins.

Selective isolation of phosphoproteins is of great significance in biological applications. Herein, titanium dioxide-functionalized dendritic mesoporous silica nanoparticles are prepared via a post-grafting method for selective capture of phosphoproteins. The fabricated nanoparticles possess a unique central-radial pore structure with a surface area of 666.66 m2 /g and a pore size of 22.2 nm. The high-binding affinity of TiO2 with the phosphate groups facilitates the selective adsorption of phosphoproteins. Moreover, the open central-radial pore structure endows the dendritic mesoporous nanoparticles with better adsorption performance toward phosphoproteins with respect to the commercial titanium dioxide nanoparticles and titanium dioxide-functionalized conventional mesoporous silica nanoparticles by providing more accessible affinity sites. At pH 2, an adsorption capacity of 157.2 mg/g is derived for ß-casein. The feasibility of the as-prepared dendritic material in real biological sample assay is demonstrated by the selective isolation of phosphoproteins from defatted milk, as illustrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis assay.

Three-Dimensional DNA Nanomachine Biosensor by Integrating DNA Walker and Rolling Machine Cascade Amplification for Ultrasensitive Detection of Cancer-Related Gene.

Stochastic DNA walkers capable of traversing on three-dimensional (3D) tracks have received great deal of attention. However, DNA walker-based biosensors exhibit limited amplification efficiency because of their slow walking kinetics and low processivity. Herein, by taking advantage of the high processivity of a DNA rolling machine, a sensitive ratiometric DNA nanomachine biosensor is designed. The biosensor is constructed with hairpin-loaded Au nanoparticles (NPs) (hpDNA@AuNPs) as a DNA walker and AgNCs-decorated magnetic NPs (AgNCs@MNPs) as a DNA rolling machine. In the presence of target DNA, exonuclease III (Exo III)-powered DNA walker is activated to accomplish first-stage amplification via a burnt-bridge mechanism, generating a great deal of toehold-loaded AuNPs (Toehold@AuNPs) to hybridize with magnetic nanoparticles loaded with silver-nanoclusters-labeled DNA (AgNCs@MNPs) with the assistance of Exo III. These trigger rapid rolling of AuNPs on the AgNCs@MNPs surface and release free AgNCs, converting the biological signal into a mass spectrometric signal ratio (107Ag/197Au) with detection by ICP-MS. A linear range of 0.5-500 fmol L-1 is achieved with a detection limit of 119 amol L-1 for the p53 gene. The practical applicability of the biosensor has been demonstrated in the accurate assay of the p53 gene in the human blood.

Inertial-Force-Assisted, High-Throughput, Droplet-Free, Single-Cell Sampling Coupled with ICP-MS for Real-Time Cell Analysis.

Single-cell analysis facilitates perception into the most essential processes in life's mysteries. While it is highly challenging to quantify them at the single-cell level, where precise single-cell sampling is the prerequisite. Herein, a real-time single-cell quantitative platform was established for high-throughput droplet-free single-cell sampling into time-resolved (TRA) ICP-MS and real-time quantification of intracellular target elements. The concentrated cells (2 × 106 cells mL-1) were spontaneously and orderly aligned in a spiral microchannel with 104 periodic dimensional confined micropillars. The quantification is conducted simultaneously by internal standard inducing from another branch channel in the chip. The flow-rate-independent feature of single-cell focusing into an aligned stream within a wide range of fluidic velocities (100-800 µL min-1) facilitates high-throughput, oil-free, single-cell introduction into TRA-ICP-MS. The system was used for real-time exploration of intracellular antagonism of Cu2+ against Cd2+. an obvious antagonistic effect was observed for the MCF-7 cell by culturing for 3, 6, 9, and 12 h with 100 µg L-1 Cd2+ and 100 µg L-1 Cu2+, and a rivalry rate of 12.8% was achieved at 12 h. At identical experimental conditions, however, limited antagonistic effect was encountered for a bEnd3 cell within the same incubation time period, with a rivalry rate of 4.81%. On the contrary, an antagonistic effect was not observed for the HepG2 cell by culturing for 6 h, while an obvious antagonistic effect was found by further culturing to 12 h, with a rivalry rate of 10.43%. For all three cell lines, significant heterogeneity was observed among individual cells.

Amplification Strategy of Silver Nanoclusters with a Satellite-Nanostructure for Substrate-Free Assay of Alkaline Phosphatase by ICP-MS.

Alkaline phosphatase (ALP) plays critical roles in signal transmission and cell growth/apoptosis. Its abnormal level in serum/cell is tightly related to diseases, thus, serum and cellular ALP detection is of great significance for disease diagnosis. Herein, a novel approach for ALP assay based on a satellite-nanostructure is developed by conjugating lanthanide upconversion nanoparticles (UCNPs) with silver nanoclusters (AgNCs) through DNA bridging. UCNPs serve as the cores to conjugate with DNA fragments, followed by assembly of AgNCs as the satellites on UCNPs surface through the AgNCs-cytosine affinity, to produce the satellite-nanostructure of UCNPs@DNA-AgNCs. The presence of ALP converts phosphate groups into hydroxyl groups at DNA helix, weakening the coordination of DNA with UCNPs. As a result, the satellite AgNC labeling on DNA fragments strips off the UCNP surface. Silver is quantified by measuring isotope 107Ag with ICP-MS, which further derives the content of ALP by correlation to the number of AgNCs. A linear calibration range is obtained in 0.005-120 U/L with a detection limit of 1.8 mU/L. The distinct advantage of this strategy, on one hand, is the substrate-free feature that eliminates the intermediate process of substrate reaction, where the substrate activity decrease and its instability may significantly deteriorate the sensitivity. On the other hand, ALP triggers the production of a large number of AgNCs resulting in substantial amplification on ICP-MS signal to give a favorable sensitivity. This is the first attempt for ALP detection by inductively coupled plasma mass spectrometry.

Ensuring high selectivity for preconcentration and detection of ultra-trace cadmium using a phage-functionalized metal-organic framework.

Metal-organic frameworks functionalized with Cd(ii) binding phages were for the first time fabricated for the isolation and preconcentration of ultra-trace cadmium. Highly specific Cd(ii) binding phages were screened through biological panning from a phage display peptide library. Thereafter, chloroauric acid (HAuCl4) was reduced by the phages to provide phage-stabilized gold nanoparticles (AuNPs). The phage-AuNP networks were then assembled onto the metal-organic framework UiO66-NH2 to serve as an affinity probe for the selective recognition and isolation of ultra-trace cadmium. 2.0 µg L-1 Cd2+ was selectively captured by the derived UiO66-NH2@phage composite with an adsorption efficiency of 100%. UiO66-NH2@phage exhibits favorable anti-interference capability against the coexisting species. It ensures highly selective and sensitive quantification of ultra-trace cadmium with detection by graphite furnace atomic absorption spectrometry (GFAAS). An enrichment factor of 17.4 was obtained along with a limit of detection (LOD) of 3.9 ng L-1 within a linear range of 0.01-0.35 µg L-1. The procedure was further validated by analyzing cadmium content in a certified reference material (CRM, simulated water, GBW08608) and a series of environmental water samples. In general, the present study provides a new protocol for the development of novel adsorbents toward the target by biopanning to regulate the selectivity.

Mercury speciation based on mercury-stimulated peroxidase mimetic activity of gold nanoparticles.

Mercury speciation is of significant importance in environmental and biological analysis because its toxicity and metabolic behavior in the human body differ among species. Nanomaterial-assisted optical sensors are widely used for mercury ion detection but rarely applied in mercury speciation analysis. In this work, we develop a novel colorimetric sensing strategy for mercury speciation based on mercury-stimulated peroxidase mimetic activity of gold nanoparticles with the assistance of different reductants. In the presence of a weak reductant, only inorganic mercury can be reduced to Hg0, whereas both inorganic mercury and organic mercury can be reduced to Hg0 in the presence of a strong reductant. Due to the high affinity between Hg and Au, Hg0 deposits on the AuNP surface in the form of a Au-Hg amalgam, leading to a remarkable enhancement of peroxidase mimetic activity of gold nanoparticles. On the basis of this effect, inorganic mercury and total mercury can be detected by using 3,3',5,5'-tetramethylbenzidine (TMB) as the substrate. The limits of detection for inorganic mercury and total mercury are 1.9 and 0.9 nM within 5-100 nM, respectively. The selectivity of this sensing system is high due to the specificity of Au-Hg interaction. Its practical applications are further demonstrated by organic mercury analysis in a fish sample and mercury speciation in a human hair sample.