Prospectively Isolated Tetraspanin+ Neoblasts Are Adult Pluripotent Stem Cells Underlying Planaria Regeneration.

Proliferating cells known as neoblasts include pluripotent stem cells (PSCs) that sustain tissue homeostasis and regeneration of lost body parts in planarians. However, the lack of markers to prospectively identify and isolate these adult PSCs has significantly hampered their characterization. We used single-cell RNA sequencing (scRNA-seq) and single-cell transplantation to address this long-standing issue. Large-scale scRNA-seq of sorted neoblasts unveiled a novel subtype of neoblast (Nb2) characterized by high levels of PIWI-1 mRNA and protein and marked by a conserved cell-surface protein-coding gene, tetraspanin 1 (tspan-1). tspan-1-positive cells survived sub-lethal irradiation, underwent clonal expansion to repopulate whole animals, and when purified with an anti-TSPAN-1 antibody, rescued the viability of lethally irradiated animals after single-cell transplantation. The first prospective isolation of an adult PSC bridges a conceptual dichotomy between functionally and molecularly defined neoblasts, shedding light on mechanisms governing in vivo pluripotency and a source of regeneration in animals. VIDEO ABSTRACT.

Island-specific evolution of a sex-primed autosome in a sexual planarian.

The sexual strain of the planarian Schmidtea mediterranea, indigenous to Tunisia and several Mediterranean islands, is a hermaphrodite1,2. Here we isolate individual chromosomes and use sequencing, Hi-C3,4 and linkage mapping to assemble a chromosome-scale genome reference. The linkage map reveals an extremely low rate of recombination on chromosome 1. We confirm suppression of recombination on chromosome 1 by genotyping individual sperm cells and oocytes. We show that previously identified genomic regions that maintain heterozygosity even after prolonged inbreeding make up essentially all of chromosome 1. Genome sequencing of individuals isolated in the wild indicates that this phenomenon has evolved specifically in populations from Sardinia and Corsica. We find that most known master regulators5-13 of the reproductive system are located on chromosome 1. We used RNA interference14,15 to knock down a gene with haplotype-biased expression, which led to the formation of a more pronounced female mating organ. On the basis of these observations, we propose that chromosome 1 is a sex-primed autosome primed for evolution into a sex chromosome.

SERS-Temperature Dual-Mode T-type Lateral Flow Strip for Accurate Detection of Free and Total Prostate-Specific Antigens in Blood.

Accurate point-of-care (POC) analysis of cancer markers is the essence in the comprehensive early screening and treatment of cancer. Dual-mode synchronous detection is one of the effective approaches to reduce the probability of false negatives or false positives. As a result, this can greatly improve the accuracy of diagnosis. In this work, a surface-enhanced Raman scattering (SERS)-temperature dual-mode T-type lateral flow strip was fabricated to direct and simultaneous POC detection of total and free prostate-specific antigens (t-PSA and f-PSA) in blood. With the advantage of high stability of T-type lateral flow strip and simultaneous acquirement of assay results for t-PSA and f:t PSA ratio, the proposed method has high accuracy in the diagnosis of prostate cancer, especially in the diagnostic gray zone between 4.0 and 10.0 ng/mL. The SERS-temperature dual-signal has a good linear correlation with either f-PSA or t-PSA. To evaluate the clinical diagnostic performance of the proposed method, spiked human serum samples and the whole blood sample were analyzed. The assay results showed good recovery, and compared with traditional electrochemiluminescence immunoassay (ECLIA) method (t-PSA: 43.151; f/t ratio: 0.08), the results obtained by the proposed method were similar (t-PSA: 40.15 (SERS), 36.21 (temperature); f/t ratio: 0.08 (SERS), 0.08 (temperature), but the detection time (15 min) and cost ($0.05) had been greatly reduced. Therefore, the proposed SERS-temperature synchronous dual-mode T-type lateral flow strip has a strong application potential in the field of accurate large-scale diagnostics of prostate cancer on-site by simultaneous POC detection of t-PSA and f-PSA in blood.

Genetics of white color and iridophoroma in "Lemon Frost" leopard geckos.

The squamates (lizards and snakes) are close relatives of birds and mammals, with more than 10,000 described species that display extensive variation in a number of important biological traits, including coloration, venom production, and regeneration. Due to a lack of genomic tools, few genetic studies in squamates have been carried out. The leopard gecko, Eublepharis macularius, is a popular companion animal, and displays a variety of coloration patterns. We took advantage of a large breeding colony and used linkage analysis, synteny, and homozygosity mapping to investigate a spontaneous semi-dominant mutation, "Lemon Frost", that produces white coloration and causes skin tumors (iridophoroma). We localized the mutation to a single locus which contains a strong candidate gene, SPINT1, a tumor suppressor implicated in human skin cutaneous melanoma (SKCM) and over-proliferation of epithelial cells in mice and zebrafish. Our work establishes the leopard gecko as a tractable genetic system and suggests that a tumor suppressor in melanocytes in humans can also suppress tumor development in iridophores in lizards.

On-site preparation of sandwich plasmonic coupled SERS tape toward pesticide residue determination on food surface.

A sandwich plasmonic coupled surface enhanced Raman spectroscopy (SERS) tape is proposed prepared by peeling the chemical printed silver nanocorals (AgNCs) from Cu sheet with adhesive tape, which can sample targets from food surface and sandwich them between substrates and Cu sheet for SERS detection. The solid-to-solid transformation method for fabricating SERS tapes can effectively avoid the weakening of tape stickiness during the preparation process. The sandwich plasmonic coupled structure of AgNC substrate, targets, and Cu sheet display excellent SERS activity (EF = 1.62 × 107) for sensitive determination of analytes. In addition, due to the high heat conductivity of Cu sheet, the thermal effect of laser irradiation during SERS detection cannot damage the AgNC tapes, which ensures the reproducibility of subsequent quantification. The sandwich plasmonic coupled SERS tape is demonstrated to quantify malachite green (MG) and methyl parathion (MP) with good linear coefficients (> 0.98) by two typical calibration plots under different concentration ranges. The limit of detection (LOD) of the method is 0.17 ng/cm2 and 0.48 µg/cm2 (S/N = 3) for MG and MP. This method can realize the quantitative determination of MP and MG on the surface of fruits and fish scale with recoveries of 93-113%. The satisfactory detection results demonstrate the proposed sandwich plasmonic coupled AgNC tape can be successfully applied to SERS-based point-of-care testing (POCT) for pesticide residue determination, which will provide a new path for designing and constructing SERS tapes.

NIR-II Fluorescence Sensor Based on Steric Hindrance Regulated Molecular Packing for In Vivo Epilepsy Visualization.

Fluorescence sensing is crucial to studying biological processes and diagnosing diseases, especially in the second near-infrared (NIR-II) window with reduced background signals. However, it's still a great challenge to construct "off-on" sensors when the sensing wavelength extends into the NIR-II region to obtain higher imaging contrast, mainly due to the difficult synthesis of spectral overlapped quencher. Here, we present a new fluorescence quenching strategy, which utilizes steric hindrance quencher (SHQ) to tune the molecular packing state of fluorophores and suppress the emission signal. Density functional theory (DFT) calculations further reveal that large SHQs can competitively pack with fluorophores and prevent their self-aggregation. Based on this quenching mechanism, a novel activatable "off-on" sensing method is achieved via bio-analyte responsive invalidation of SHQ, namely the Steric Hindrance Invalidation geNerated Emission (SHINE) strategy. As a proof of concept, the ClO--sensitive SHQ lead to the bright NIR-II signal release in epileptic mouse hippocampus under the skull and high photon scattering brain tissue, providing the real-time visualization of ClO- generation process in living epileptic mice.

Molecular characterization of a flatworm Girardia isolate from Guanajuato, Mexico.

Planarian flatworms are best known for their impressive regenerative capacity, yet this trait varies across species. In addition, planarians have other features that share morphology and function with the tissues of many other animals, including an outer mucociliary epithelium that drives planarian locomotion and is very similar to the epithelial linings of the human lung and oviduct. Planarians occupy a broad range of ecological habitats and are known to be sensitive to changes in their environment. Yet, despite their potential to provide valuable insight to many different fields, very few planarian species have been developed as laboratory models for mechanism-based research. Here we describe a previously undocumented planarian isolate, Girardia sp. (Guanajuato). After collecting this isolate from a freshwater habitat in central Mexico, we characterized it at the morphological, cellular, and molecular level. We show that Girardia sp. (Guanajuato) not only shares features with animals in the Girardia genus but also possesses traits that appear unique to this isolate. By thoroughly characterizing this new planarian isolate, our work facilitates future comparisons to other flatworms and further molecular dissection of the unique and physiologically-relevant traits observed in this Girardia sp. (Guanajuato) isolate.

Genetics and biology of coloration in reptiles: the curious case of the Lemon Frost geckos.

Although there are more than 10,000 reptile species, and reptiles have historically contributed to our understanding of biology, genetics research into class Reptilia has lagged compared with other animals. Here, we summarize recent progress in genetics of coloration in reptiles, with a focus on the leopard gecko, Eublepharis macularius. We highlight genetic approaches that have been used to examine variation in color and pattern formation in this species as well as to provide insights into mechanisms underlying skin cancer. We propose that their long breeding history in captivity makes leopard geckos one of the most promising emerging reptilian models for genetic studies. More broadly, technological advances in genetics, genomics, and gene editing may herald a golden era for studies of reptile biology.

One-Step, On-Site Chemical Printing of a 3D Plasmon-Coupled Silver Nanocoral Substrate toward SERS-Based POCT.

Surface-enhanced Raman scattering (SERS) with the advantages of high sensitivity, nondestructive analysis, and a unique fingerprint effect shows great potential in point-of-care testing (POCT). However, SERS faces challenges in rapidly constructing a substrate with high repeatability, homogeneity, and sensitivity, which are the key factors that restrict its practical applications. In this study, we propose a one-step chemical printing strategy for synthesizing a three-dimensional (3D) plasmon-coupled silver nanocoral (AgNC) substrate (only need about 5 min) without any pretreatments and complex instruments. The galvanic replacement between AgNO3 and Cu sheets will provide both Ag0 for the formation of silver nanostructures and Cu2+ for the polymerization of fish sperm DNA (FSDNA). The protection of AgNCs is facilitated by the crosslinked FSDNA, which can improve the stability of the substrate and promote the control of its coral-like morphology. The obtained substrate displays excellent capacity of signal enhancement due to the 3D plasmon coupling both between nanocoral tentacles and between nanocorals and Cu sheets as well. Therefore, the AgNC substrates display high activity (enhancement factor = 1.96 × 108) and uniformity (RSD < 6%). Food colorants have been widely used in various foods to improve their color, but the inevitable toxicity of colorants seriously threatens food safety. Therefore, the proposed AgNC substrates were used to directly quantify three kinds of weak-affinity food colorant molecules including Brilliant Blue, Allura Red, and Sunset Yellow assisted by the capture by cysteamine hydrochloride (CA), showing the detection limits (S/N = 3) of 0.053, 0.087, and 0.089 ppm, respectively. The SERS method has been further applied in the detection of the three kinds of food colorants in both complex food samples and urine with recoveries of 91-119%. The satisfactory detection results suggest that the facile preparation strategy of AgNC substrates will be widely used in SERS-based POCT to promote the development of food safety and on-site healthcare.

A photoelectrochemical aptasensor for tetracycline based on the self-assembly of 2D MoS2 on a 3D ZnO/Au/ITO electrode.

Two-dimensional (2D) layered MoS2 has good dispersion and adsorption properties, but being a narrow bandgap semiconductor limits its application in photoelectric sensing. In this study, a homogeneous photoelectrochemical sensor based on three-dimensional (3D) ZnO/Au/2D MoS2 is proposed for the ultrasensitive detection of tetracycline (TET). MoS2 is uniformly embedded on the 3D ZnO/Au surface by ordered self-assembly. The physical method of π-π interaction of MoS2 replaces the conventional use of chemically modifying aptamers on the electrode material surface. Under optimal conditions, this method has been successfully applied to the detection of TET in milk, honey, pig kidney and pork samples with reliable results. We believe that this study presents a method for the preparation of sensing carriers and target detection with great potential for application.

A novel core-shell composite of PCN-222@MIPIL for ultrasensitive electrochemical sensing 4-nonylphenol.

A novel core-shell composite of PCN-222 and molecularly imprinted poly (ionic liquid) (PCN-222@MIPIL) with high conductivity and selectivity was prepared for electrochemical sensing 4-nonylphenol (4-NP). The electrical conductivities of some MOFs including PCN-222, ZIF-8, NH2-UIO-66, ZIF-67, and HKUST-1 were explored. The results indicated that PCN-222 had the highest conductivity and was then used as a novel imprinted support. PCN-222@MIPIL with core-shell and porous structure was synthesized using PCN-222 as support and 4-NP as template. The average pore volume of PCN-222@MIPIL was 0.085 m3 g-1. In addition, the average pore width of PCN-222@MIPIL was from 1.1 to 2.7 nm. The electrochemical response for PCN-222@MIPIL sensor for 4-NP was 2.54, 2.14, and 4.24 times that of non-molecularly imprinted poly (ionic liquid) (PCN-222@NIPIL), PCN-222, and MIPIL sensors, respectively, which result from superior conductivity and imprinted recognition sites of PCN-222@MIPIL. The current response of PCN-222@MIPIL sensor to 4-NP concentration from 1 × 10-4 to 10 µM presented an excellent linear relationship. The detection limit of 4-NP was 0.03 nM. The synergistic effect between the PCN-222 supporter with high conductivity, specific surface area and shell layer of surface MIPIL results in the outstanding performance of PCN-222@MIPIL. PCN-222@MIPIL sensor was adopted for detecting 4-NP in real samples and presented to be a reliable approach for determining 4-NP.

A novel fluorescence aptasensor based on PCN-223 as an efficient quencher for sensitive determination of prostate-specific antigen.

A novel fluorescence aptasensor based on PCN-223 as an efficient quencher was developed to sensitively detect prostate-specific antigen (PSA). The 5-carboxytetramethylrhodamine (TAMRA)-labeled PSA aptamer was adsorbed on PCN-223 by π-π stacking and hydrogen-bonding interactions, which contributed to fluorescence quenching because of the photoinduced electron transfer from TAMRA to PCN-223. In addition, the amount of quenched fluorescence of the PSA-binding aptamer complex-PCN-223 was lower than that of TAMRA aptamer-PCN-223 without PSA (at excitation/emission peaks of 545/582 nm), which can be explained by the fact that the PSA-binding aptamer complexes contributed to the separation of the aptamer from PCN-223. ∆F value of fluorescence intensities for TAMRA aptamer-PCN-223 with and without PSA showed a good linear relationship with PSA concentration over a range of 0.1 to 24 ng mL-1, with a detection limit of 0.05 ng mL-1. Compared with three metal-organic frameworks (MOFs) of UiO-66-NH2, ZIF-67, and Ni3(HITP)2 as quenchers, PCN-223 as a Zr-MOF exhibited the highest ∆F value for PSA detection. The advantage of PCN-223 could be attributed to its carboxyl, benzene, and porphyrin groups, the large specific surface area and good biocompatibility. This proposed aptasensor can be successfully used to detect PSA in sera of prostate cancer patients. The PSA detection results of this aptasensor were consistent with those which were obtained from hospital by Archtecti2000sr automatic chemiluminescence immunoanalyzer. The proposed aptasensor has potential clinical detection application.

Gold nanoparticle dimer-based immunochromatography for in situ ultrasensitive detection of porcine epidemic diarrhea virus.

The low detection sensitivity of lateral-flow immunochromatography assay (LFIA) based on spherical gold nanoparticle (AuNP) limits its wide applications. In the present study, AuNP dimers with strong plasma scattering and robust signal output were synthesized via the Ag ion soldering (AIS) strategy and used as labeled probes in LFIA to boost the sensitivity without any extra operation process and equipment. The established LFIA exhibited high sensitivity with a limit of detection (LOD) of 2.0 × 102 TCID50/mL for PEDV, which provides 50 times higher sensitivity than commercial LFIA based on spherical colloidal gold. In addition, the AuNP dimer-based LFIA showed strong specificity, good reproducibility, high stability, and good accordance to reverse transcription polymer chain reaction (RT-PCR) when detecting 109 clinical samples. Thus, the AuNP dimers is a promising probe for LFIA and the developed AuNP dimer-based LFIA is suitable for the rapid detection of PEDV in the field.

Bioinformatics Analysis and Screening of Potential Target Genes Related to the Lung Cancer Prognosis.

OBJECTIVE: Several genes have been validated as molecular targets for gene therapy in lung cancer. We screened target genes that affect survival of patients with lung cancer. METHODS: Data on gene expression in normal lung tissues/lung adenocarcinoma (LUAD) samples were acquired from Genotype-Tissue Expression (GTEx)/The Cancer Genome Atlas (TCGA) databases and merged to expand the sample size, followed by differential analysis of the merged expression data and acquisition of differentially expressed genes. Survival and simple Cox analyses were used to screen for genes affecting LUAD survival. Protein-protein interaction/multivariable Cox analyses were utilized, and a risk model was established. Candidate genes expression levels in cancer/paracancerous tissues of lung cancer patients, and BEAS-2B/A549/HCC95 cells were measured by RT-qPCR/Western blot. Survival analysis of candidate genes was conducted in LUAD samples collected from TCGA. RESULTS: Among 947 genes differentially expressed in LUAD, 151 were correlated with patient survival, and 116 might act as risk factors for LUAD. The 7 identified candidate genes (TOP2A, TK1, KIF4A, ANLN, KIF2C, ASF1B, CCNB1) were high-risk genes playing possible roles in LUAD. These genes were differentially expressed in lung cancer and were associated with TNM stages (III - IV)/differentiation grade/lymph node metastasis/distant metastasis, which affected lung cancer patient survival. CONCLUSION: P2A, TK1, KIF4A, ANLN, KIF2C, ASF1B and CCNB1 were highly-expressed in LUAD/lung squamous cell carcinoma (LUSC) and correlated with LUAD patient survival. This study contributes to better understanding of the prognostic regulation mechanism in LUAD and the screening of target genes for clinical treatment.

Retrospective Detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Symptomatic Patients Prior to Widespread Diagnostic Testing in Southern California.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused one of the worst pandemics in recent history. Few reports have revealed that SARS-CoV-2 was spreading in the United States as early as the end of January. In this study, we aimed to determine if SARS-CoV-2 had been circulating in the Los Angeles (LA) area at a time when access to diagnostic testing for coronavirus disease 2019 (COVID-19) was severely limited. METHODS: We used a pooling strategy to look for SARS-CoV-2 in remnant respiratory samples submitted for regular respiratory pathogen testing from symptomatic patients from November 2019 to early March 2020. We then performed sequencing on the positive samples. RESULTS: We detected SARS-CoV-2 in 7 specimens from 6 patients, dating back to mid-January. The earliest positive patient, with a sample collected on January 13, 2020 had no relevant travel history but did have a sibling with similar symptoms. Sequencing of these SARS-CoV-2 genomes revealed that the virus was introduced into the LA area from both domestic and international sources as early as January. CONCLUSIONS: We present strong evidence of community spread of SARS-CoV-2 in the LA area well before widespread diagnostic testing was being performed in early 2020. These genomic data demonstrate that SARS-CoV-2 was being introduced into Los Angeles County from both international and domestic sources in January 2020.

Genomic epidemiology of the Los Angeles COVID-19 outbreak and the early history of the B.1.43 strain in the USA.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused global disruption of human health and activity. Being able to trace the early outbreak of SARS-CoV-2 within a locality can inform public health measures and provide insights to contain or prevent viral transmission. Investigation of the transmission history requires efficient sequencing methods and analytic strategies, which can be generally useful in the study of viral outbreaks. METHODS: The County of Los Angeles (hereafter, LA County) sustained a large outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To learn about the transmission history, we carried out surveillance viral genome sequencing to determine 142 viral genomes from unique patients seeking care at the University of California, Los Angeles (UCLA) Health System. 86 of these genomes were from samples collected before April 19, 2020. RESULTS: We found that the early outbreak in LA County, as in other international air travel hubs, was seeded by multiple introductions of strains from Asia and Europe. We identified a USA-specific strain, B.1.43, which was found predominantly in California and Washington State. While samples from LA County carried the ancestral B.1.43 genome, viral genomes from neighboring counties in California and from counties in Washington State carried additional mutations, suggesting a potential origin of B.1.43 in Southern California. We quantified the transmission rate of SARS-CoV-2 over time, and found evidence that the public health measures put in place in LA County to control the virus were effective at preventing transmission, but might have been undermined by the many introductions of SARS-CoV-2 into the region. CONCLUSION: Our work demonstrates that genome sequencing can be a powerful tool for investigating outbreaks and informing the public health response. Our results reinforce the critical need for the USA to have coordinated inter-state responses to the pandemic.

Highly Sensitive Photoelectrochemical Biosensor for MicroRNA-21 Based on a Dumbbell-Shaped Heterostructure AuNRs@end-TiO2 Combined with Carbon Dots as Photosensitizers and Duplex-Specific Nuclease-Assisted Signal Amplification.

TiO2 was grown on both ends of gold nanorods (AuNRs) to form a dumbbell-shaped heterostructure (called AuNRs@end-TiO2) first, and then assembled on the fluorine tin oxide (FTO) electrode surface through hydrophobic interactions to construct a concise photoelectrochemical microRNA-21 (miRNA-21, model target) biosensor using carbon dots (CDs) as photosensitizers. Hairpin probes (HPs) were fixed on the AuNRs@end-TiO2-modified FTO electrode surface through the Au-S bond, and CDs-modified complementary DNA (CDs-cDNA) served as photosensitive probes. In the presence of the target, miRNA hybridized with the HP and triggered double-strand-specific nuclease to cleave the complementary part of the HP with miRNA, and miRNA was released, which can trigger another cycle to realize signal amplification. Many HPs were cleaved and the complementary sequence with cDNA was exposed, which can capture the photosensitive probes to the electrode surface and resulted in photocurrent enhancement. The photocurrent intensity system has a linear relationship with the logarithm of the miRNA concentration in the range of 0.1 fM to 100 pM with a low detection limit of 96 aM (S/N = 3). The biosensor has high sensitivity, good selectivity, and good reproducibility and shows satisfactory results in actual sample detection.

Surface-Enhanced Electrochemiluminescence Imaging for Multiplexed Immunoassays of Cancer Markers in Exhaled Breath Condensates.

Recently we have demonstrated that the surface plasmon of noble metal nanoparticles can effectively enhance the ECL intensity of Ru(bpy)32+, and we named this detection principle as surface-enhanced electrochemiluminescence (SEECL-I). However, SEECL based on photomultiplier tube (PMT) detection can only detect one target at a time, which is not suitable for multiple targets detection. In this work, we combined our previous developed SEECL with a bioimaging device to develop a novel multiplexed immunassay for simultaneous and fast analysis of cancer markers. A core-shell nanocomposite consisted of gold-silicon dioxide nanoparticles doped with Ru(bpy)32+(Au@SiO2-Ru) with strong ECL emission was employed as ECL label due to the localized surface plasmon resonance (LSPR) of AuNPs, which can significantly enhance the ECL emission of Ru(bpy)32+. The ECL signals from the 4 × 4 electrode arrays were collected using the constant potential method (current-time curve method) imaging with a sCOMS camera. As a proof-of-concept application, we demonstrated the use of the proposed SEECL-I for simultaneous detection of carcinoembryonic antigen (CEA), neuron specific enolase (NSE), and squamous cell carcinoma antigen (SCC) in exhaled breath condensates (EBCs) with low detection limit (LOD) of 0.17, 0.33, and 0.33 pg/mL (S/N = 3), respectively. The results demonstrated that the proposed SEECL-I strategy can provide a high sensitivity, fast analysis, and high-throughput platform for clinical diagnosis of cancer markers in EBCs.

An algorithm-assisted automated identification and enumeration system for sensitive hydrogen sulfide sensing under dark field microscopy.

Hydrogen sulfide (H2S) is an active physiological molecule, and its intracellular level has great significance to life functions. In this study, an effective and sensitive method was developed for H2S sensing with dark field microscopy (DFM). The proposed method employed AuNPs as the signal source, DFM as the readout system, and an intelligence algorithm as the image processing and output systems, respectively. The AuNP surface was modified with azido and alkynyl in advance, and then added into a tube cap. As the H2S evaporated from the solution and selectively reduced azido to amino, the click chemistry reaction was inhibited, which resulted in the AuNPs being well dispersed in the solution; otherwise, AuNP aggregation occurred. The scattering colour of single AuNPs could be easily distinguished from that of AuNP aggregations with DFM, and the number or ratio of single AuNPs could also be easily obtained by the custom algorithm. The results showed that the H2S content could be linearly analyzed in a range from 2-80 µM. Furthermore, the proposed sensing strategy has been applied for H2S detection in cell lysate. Compared with the traditional colorimetric method, the results showed no significant difference, indicating the good prospects of the algorithm and proposed H2S sensing method.

Highly Sensitive Homogeneous Electrochemiluminescence Biosensor for Alkaline Phosphatase Detection Based on Click Chemistry-Triggered Branched Hybridization Chain Reaction.

Alkaline phosphatase (ALP) has been used as a diagnostic index of clinical diseases since its expression level is closely related to many pathological processes. In this work, a highly sensitive electrochemiluminescence (ECL) method for the determination of ALP based on a click chemistry-induced branched hybridization chain reaction (BHCR) for signal amplification and ultrafiltration technology for the separation of homogeneous amplification products is introduced. ALP can release copper ions from a Cu2+/PPi complex by hydrolyzing pyrophosphoric acid, which initiates click chemistry in the system. A BHCR amplification is triggered afterward by the long single-stranded DNA (ssDNA) generated by click chemistry, resulting in a three-dimensional double-stranded DNA (dsDNA) with a large molecular weight. Based on the characteristic that Ru(phen)32+ can stably insert into the groove of dsDNA, a large amount of Ru(phen)32+ is retained together with the amplified product after ultrafiltration, and therefore a significantly enhanced ECL signal can be obtained. The test results show that this method can be used for the quantitative determination of ALP ranging from 0.002 to 50 U/L, with a detection limit of 0.7 mU/L. This method has also been confirmed to have good selectivity and anti-interference, and the results of the analysis of the ALP content in the diluted serum samples are satisfactory, showing great application potential in clinical diagnosis.