Showing papers in "Analyst in 2022"

A microscopic survey on microplastics in beverages: the case of beer, mineral water and tea.

Abstract: It has been reported that microplastics exist ubiquitously in aquatic and terrestrial environments. Microplastic surveys on diverse daily foods with high consumption possibly containing microplastics have essential implications in clarifying the contamination routes, health risk assessment, and thereby preventing food pollution. Given the dependence of microplastic pollution on the regional environment, production and transportation, it further remains an open question on the number, size distribution and type of microplastics in foods from different countries worldwide. Here, we show that daily drinks produced worldwide, including beer, mineral water and tea, are all polluted with microplastics without exception. The number of microplastics investigated in this work lies in the range of 20-80 mL-1 for the beers, 10 mL-1 for the bottled mineral water, and 200-500 g-1 for the tea leaves. Quasi-spherical particles and irregular fragments dominate the shape of microplastics in beer and mineral water, whereas tea leaves carry numerous microplastic fibers. By identification through Raman spectroscopy, we observed the presence of polystyrene (PS) and polypropylene (PP) microplastics in beers, PP in bottled mineral water, and polyethylene (PE) and polyethylene terephthalate (PET) in tea leaves. Possible contamination sources include raw materials, atmosphere, and tools and containers that release microplastics. Given the facile adsorption of heavy metals and antibiotics to microplastics in beverages, public concern may arise regarding the accumulation of microplastics through the food chain and their synergetic harmful effect. Thus, our results should inspire further efforts that may contribute to the elimination and removal of microplastics from foods.

Semiconductor-based surface enhanced Raman scattering (SERS): from active materials to performance improvement.

Abstract: Surface enhanced Raman scattering (SERS) is a powerful spectral analysis technique and has exhibited remarkable application prospects in various fields. The design and fabrication of high-performance SERS substrates is key to promoting the development of SERS technology. Apart from noble metal substrates, non-metal substrates based on semiconductor materials have received increasing attention in recent years owing to their unique physical, chemical, and optical properties. However, compared with noble metal substrates, most semiconductor substrates show weak Raman enhancement ability. Therefore, exploring effective strategies to improve the SERS sensitivity is an urgent task. Numerous reviews have outlined the research progress of semiconductor SERS substrates, which mainly focused on summarizing the material category of semiconductor substrates. However, reviews that systematically summarize the strategies for improving the SERS performance of semiconductor substrates are lacking. In this review, we comprehensively discuss the research on semiconductor SERS from the aspects of mechanism, materials, and modification. Firstly, the Raman enhancement mechanism of semiconductor substrates and the SERS-active materials are discussed. Then, we summarize several effective approaches to boost the SERS performance of semiconductor substrates. In conclusion, we propose some prospects for this field.

A highly flexible Ni-Co MOF nanosheet coated Au/PDMS film based wearable electrochemical sensor for continuous human sweat glucose monitoring.

Abstract: The development of flexible substrate materials and nanomaterials with high electrochemical performance is of great significance for constructing efficient wearable electrochemical sensors for real-time health monitoring. Herein, a wearable electrochemical sweat sensor based on a Ni-Co MOF nanosheet coated Au/polydimethylsiloxane (PDMS) film was prepared for continuous monitoring of the glucose level in sweat with high sensitivity. First, a stretchable Au/PDMS film based three-electrode system was prepared by chemical deposition of a gold layer on the hydrophilic treated PDMS. Then, Ni-Co MOF nanosheets with high electrocatalytic activity were synthesized by a facile solvothermal method and modified on the Au/PDMS electrode. The electrocatalytic activity of the Ni-Co MOF nanosheets synthesized under different Ni : Co ratios was investigated. The Ni-Co MOF/Au/PDMS (NCAP) film electrode showed excellent electrochemical performance for glucose detection with a wide linear range of 20 μM to 790 μM and a high sensitivity of 205.1 μA mM-1 cm-2. In addition, the flexible sensor shows high stability and a good electrochemical response to glucose when stretched and bent to different levels. Moreover, it maintained long-term stability and high selectivity for glucose monitoring. Lastly, a sweat-absorbent cloth was used to cover the working area of the sensor and was fixed with a needle and thread to form a wearable sweat glucose sensor. The sensor can be attached to the skin for stable, accurate and continuous monitoring of glucose levels in human sweat for one day. This work validates the potential of our high-performance wearable sensor for out-of-clinic health monitoring.

Single-cell droplet microfluidics for biomedical applications.

Abstract: Single-cell manipulation and analysis is critical to the study of many fundamental biological processes and uncovering cellular heterogeneity, and presents the potential for extremely valuable applications in biomedical fields, including neuroscience, regenerative therapy, early diagnosis, and drug screening. The use of microfluidic technologies in single-cell manipulation and analysis is one of the most promising approaches and enables the creation of innovative conditions that are impractical or impossible to achieve using conventional methods. Herein, an overview of the technological development of single-cell droplet microfluidics is presented. The significant advantages of microfluidic droplet technology, the dynamic parameters affecting droplet production, and the geometric structures of microfluidic devices are emphasized. Furthermore, the progress to date in passive and active droplet generation methods based on microfluidics and various microfluidic tools for the production of single-cell droplets and hydrogel microspheres are summarized. Their key features, achievements, and limitations associated with single-cell droplet and hydrogel formation are discussed. The recent popularized applications of single-cell droplet microfluidics in biomedicine involving small-molecule detection, protein analysis, and drug screening and genetic analysis of single cells are explored too. Finally, the challenges that must be overcome to enable future applications in single-cell droplet microfluidics are highlighted.

Recent progress in the development of porous carbon-based electrodes for sensing applications.

Abstract: Electrochemical (bio)sensors are considered clean and powerful analytical tools capable of converting an electrochemical reaction between analytes and electrodes into a quantitative signal. They are an important part of our daily lives integrated in various fields such as healthcare, food and environmental monitoring. Several strategies including the incorporation of porous carbon materials in its configuration have been applied to improve their sensitivity and selectivity in the last decade. The porosity, surface area, graphitic structure as well as chemical composition of materials greatly influence the electrochemical performance of the sensors. In this review, activated carbons, ordered mesoporous carbons, graphene-based materials, and MOF-derived carbons, which are used to date as crucial elements of electrochemical devices, are described, starting from their textural and chemical compositions to their role in the outcome of electrochemical sensors. Several relevant and meaningful examples about material synthesis, sensor fabrication and applications are illustrated and described. The closer perspectives of these fascinating materials forecast a promising future for the electrochemical sensing field.

Swellable PVA/PVP hydrogel microneedle patches for the extraction of interstitial skin fluid toward minimally invasive monitoring of blood glucose level.

Abstract: Interstitial skin fluid (ISF) is an emerging alternative source of blood samples that has attracted great interest from researchers. It is a very promising way to use microneedle patches for extracting ISF. However, the recovery of ISF still faces great challenges, such as long extraction time and low extraction volume, which may affect the analysis of biomarkers. Traditional centrifugation methods cannot completely recover ISF, which leads to inaccuracy in ISF detection. In this paper, the prepared polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) microneedle patches had the ability to insert into the skin in a dry state; at the same time, the microneedle patches had good swelling properties and could extract ISF in a short time without any additional devices. Due to the thermal degradation of PVA, the way of gentle heating was used to recover ISF, which could greatly improve the accuracy of detection. By comparing the D-glucose content assay kit with the blood glucose concentration of rats detected using a commercial glucometer, the detection accuracy of the microneedle patches was verified. The microneedle patches can be used to sample ISF and analyze the level of biomarkers in ISF, and are expected to provide a basis for the prevention and diagnosis of clinical diseases in the future.

A peroxidase-like activity-based colorimetric sensor array of noble metal nanozymes to discriminate heavy metal ions.

Abstract: Heavy metal ions (HMIs), including Cu2+, Ag+, Cd2+, Hg2+, and Pb2+ from the environment pose a threat to human beings and can cause a series of life-threatening diseases. Therefore, colorimetric sensors with convenience and flexibility for HMI discrimination are still required. To provide a solution, a peroxidase-like activity-based colorimetric sensor array of citrate-capped noble metal nanozymes (osmium, platinum, and gold) has been fabricated. Some studies reported that some HMIs could interact with the noble metal nanozymes leading to a change in their peroxidase-like activity. This phenomenon was confirmed in our work. Based on this principle, different concentrations of HMIs (Cu2+, Ag+, Cd2+, Hg2+, and Pb2+) were discriminated. Moreover, their practical application has been tested by discriminating HMIs in tap water and SiYu lake water. What is more, as an example of the validity of our method to quantify HMIs at nanomolar concentrations, the LOD of Hg2+ was presented. To sum up, our study not only demonstrates the differentiation ability of this nanozyme sensor array but also gives hints for using nanozyme sensor arrays for further applications.

Fe-Doped polydopamine nanoparticles with peroxidase-mimicking activity for the detection of hypoxanthine related to meat freshness.

Abstract: Rapid and accurate monitoring of food freshness to provide consumers with high-quality meat continues to be of tremendous importance to the food industry. In this report, an efficient Fe-doped polydopamine (Fe-PDA) nanozyme with peroxidase-mimicking activity was synthesized by a high-temperature hydrothermal method, and was applied to a spectrophotometric sensing system, which successfully reports the concentration of hypoxanthine (Hx) related to meat freshness. The Fe-PDA nanozyme showed excellent peroxidase simulation activity, which was primarily verified by steady-state kinetics experiments. In the presence of xanthine oxidase (XOD), Hx can react quantitatively with dissolved O2 to generate H2O2, which can be further catalyzed and produce hydroxyl radicals (•OH) under acidic conditions via the Fe-PDA nanozyme and oxidize colorless TMB to blue oxTMB with absorbance at 653 nm. The absorbance at 653 nm expressed a clear linear relationship with hypoxanthine concentration in the range of 5.13-200 μM, and the detection limit was 1.54 μM. This method was further assessed by measuring the recovery of Hx added to meat samples, which showed promising accuracy. Overall, the developed Fe-PDA nanozyme with excellent peroxidase-mimicking activity is cost-effective, high-performance and easy to produce, offering an efficient and low-cost sensing system based on spectrophotometry for meat freshness determination as an alternative to conventional methods.

An impedimetric approach for COVID-19 detection

Abstract: In this study, an electrochemical approach for the determination of coronavirus disease (COVID-19) was developed. The biosensor system relied on the spike protein (S-protein) based infection mechanism of the virus and included separate interactions of receptors like angiotensin-converting enzyme 2 (ACE2) and CD147. After the optimization of experimental parameters, the analytical characteristics of both receptors ACE2 and CD147 were investigated. For ACE2 receptor, the linear detection ranges of the S-protein were found in the range of 700 ng mL-1 to 1500 ng mL-1 and from 1500 ng mL-1 to 7000 ng mL-1 with a limit of detection (LOD) value of 299.30 ng mL-1. Meanwhile, for CD147 receptor the linear range was in the range of 500 ng mL-1 to 5000 ng mL-1 with a LOD value of 38.99 ng mL-1. After the examination of analytical characteristics, the developed electrochemical approach was applied for severe acute respiratory syndrome coronavirus 2 samples and the obtained results were validated with real time polymerase chain reaction method.

Recent advances and applications to cultural heritage using ATR-FTIR spectroscopy and ATR-FTIR spectroscopic imaging.

Abstract: Scientific investigation of cultural heritage objects plays a vital role in a responsible modern approach to conservation and archaeology. Recent advances in spectroscopy, such as the development of Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and ATR-FTIR spectroscopic imaging, have opened up a window of opportunities for characterisation of materials in artefacts and collections from museums. This review summarises some of the recent advances and applications of these ATR-FTIR spectroscopic analytical techniques in the area of cultural heritage studies, including examples of cross-sections of oil paintings, paper, textiles, plastic objects, potteries, glasses and mineral artefacts. Two of the major advantages of ATR mode measurements are minimal or no requirements for sample preparation and its provision for high lateral spatial resolution. In addition to conventional single point detection, two-dimensional mapping and imaging is especially beneficial for chemical visualisation of multi-layered structure cultural objects. This review also explores the implications of these advantages as well as some limitations and provides a brief outlook for the possible future developments in this area.

A peroxidase-like activity-based colorimetric sensor array of noble metal nanozymes to discriminate heavy metal ions

Abstract: Heavy metal ions (HMIs), including Cu2+, Ag+, Cd2+, Hg2+, and Pb2+ from the environment pose a threat to human beings and can cause a series of life-threatening diseases. Therefore, colorimetric sensors with convenience and flexibility for HMI discrimination are still required. To provide a solution, a peroxidase-like activity-based colorimetric sensor array of citrate-capped noble metal nanozymes (osmium, platinum, and gold) has been fabricated. Some studies reported that some HMIs could interact with the noble metal nanozymes leading to a change in their peroxidase-like activity. This phenomenon was confirmed in our work. Based on this principle, different concentrations of HMIs (Cu2+, Ag+, Cd2+, Hg2+, and Pb2+) were discriminated. Moreover, their practical application has been tested by discriminating HMIs in tap water and SiYu lake water. What is more, as an example of the validity of our method to quantify HMIs at nanomolar concentrations, the LOD of Hg2+ was presented. To sum up, our study not only demonstrates the differentiation ability of this nanozyme sensor array but also gives hints for using nanozyme sensor arrays for further applications.

Highly-selective and sensitive plasmon-enhanced fluorescence sensor of aflatoxins.

Abstract: We demonstrate a novel sensor platform with enhanced sensitivity and selectivity for detecting aflatoxin B1 - a common food toxin in cereals. The approach is based on a molecularly imprinted polymer film that provides selective binding of the aflatoxin B1 and fluorescence signal from the analyte molecule enhanced by the local electric field induced in close proximity to the surface of a silver nanoparticle excited at the localized surface plasmon resonance (LSPR) wavelength. Molecularly imprinted polymers (MIPs) with supramolecular aflatoxin-selective receptor sites and embedded spherical silver nanoparticles (with diameters 30-70 nm, the LSPR band 407 nm) were prepared in the form of a thin polymer film on the surface of a glass slide using in situ polymerization. The detection limit of the sensor for aflatoxin B1 is 0.3 ng mL-1, which is significantly lower than for a fluorescent sensor without silver nanoparticles. The plasmon-enhanced fluorescence factor is 33, and the linear dynamic range of the sensor is 0.3-25 ng mL-1.

Highly sensitive and selective surface plasmon resonance biosensor for the detection of SARS-CoV-2 spike S1 protein.

Abstract: The reality that the coronavirus disease 2019 (COVID-19) is still raging around the world and making a comeback with a strong presence has highlighted the need for rapid and sensitive quantitative detection methods of viral RNA, antibody and antigen for widespread tracking and screening applications. Surface plasmon resonance (SPR) detection technology has achieved rapid development and become a standard measurement method in the fields of biosensing, biomedicine, biochemistry and biopharmaceuticals due to its advantages of high sensitivity, fast response and no need for labelling. Here, we report a sandwiched structure-based SPR biosensor for detecting a specific viral antigen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike S1 protein. The sensor combines a Ti3C2-MXene nanosheet modified sensing platform and polydopamine (PDA)-Ag nanoparticle (AgNP)/anti-SARS-CoV-2 spike S1 protein nanoconjugate signal enhancers, exhibiting a wide linear range of 0.0001 to 1000 ng mL-1 with a low detection limit of 12 fg mL-1 (S/N = 3). In the analysis of artificial saliva and human serum samples, the proposed SPR biosensor exhibits good reproducibility and high specificity, which indicates its potential for application in complex bodily fluids. The exploitation of the MXene-based SPR biochip for recognizing the SARS-CoV-2 antigen provides an accessible and rapid way for COVID-19 diagnosis, and promotes the application of 2D nanomaterial-based sensing chips in clinical diagnosis and disease screening. Significantly, the proposed method possesses general applicability that can be reprogrammed to detect any protein antigen if a corresponding specific nanobody is available.

A smartphone-adaptable fluorescent sensing tag for non-contact and visual monitoring of the freshness of fish.

Abstract: Fish-based food products play important roles in our daily diet. The related food safety is vitally essential for human health, thus it is very necessary to screen the freshness of fish-based foods. In this work, we presented a ratiometric fluorescent probe PTCN for the determination of cadaverine, a metabolic biomarker of the spoilage of fish. PTCN displayed a ratiometric fluorescence response towards cadaverine with good specificity, high sensitivity (LOD = 46 nM) and ultra-fast response (<15 s), and thus has been successfully utilized to determine cadaverine from the spoilage of fish. PTCN was fabricated into cheap and portable sensing tags, which can visually detect gaseous cadaverine with obvious fluorescence color transformation from red to green and a low detection limit (8.65 ppm). Moreover, the PTCN tags were used as smart fluorescent tags for non-contact and visual monitoring of cadaverine in fish. Furthermore, the ratiometric fluorescence signals were utilized to create a smartphone-adaptable digital sensing profile for indicating cadaverine in fish products.

Recent advances in small molecular near-infrared fluorescence probes for a targeted diagnosis of the Alzheimer disease.

Abstract: Nowadays, it is still quite challenging to achieve an early diagnosis of the Alzheimer disease (AD) in clinics. The burgeoning near-infrared fluorescence (NIRF) imaging fulfills the requirements for a precise diagnosis with good sensitivity and a high signal-to-background ratio and offers opportunities for the efficient AD diagnosis. As the pathogenesis of AD is quite complex, there is an ongoing exploration of advanced probes to specifically target AD biomarkers (e.g., amyloid-β (Aβ) plaques, neurofibrillary tangles, viscosity, peroxynitrite (ONOO-), reactive oxygen species, and methylglyoxal). To this end, a great number of small molecular fluorescent probes with good water solubility, blood-brain barrier crossing capability, and ease in tuning photophysical and biological properties have been studied for the AD diagnosis. Herein, we systematically update the progress of NIRF AD probes in the last three years. The special focus is on the mechanisms for the targeted diagnosis and the relationship between the structure and properties of the probes. Importantly, NIRF probes with complementary functions such as dual-responsiveness and multimodal imaging and even therapeutics are discussed. Moreover, the challenges and perspectives of the AD probes are briefly elucidated. We hope that this review provides guidance for researchers and expedites the preclinical and clinical study of the NIRF AD probes.

Detection of small-sized DNA fragments in a glassy nanopore by utilization of CRISPR-Cas12a as a converter system.

Abstract: The fabrication of nanopores with a matched pore size, and the existence of multiple interferents make the reproducible detection of small-sized molecules by means of solid-state nanopores still challenging. A useful method to solve these problems is based on the detection of large DNA nanostructures related to the existence of small-sized targets. In particular, a DNA tetrahedron with a well-defined 3D nanostructure is the ideal candidate for use as a signal transducer. Here, we demonstrate the detection of an L1-encoding gene of HPV18 as a test DNA target sequence in a reaction buffer solution, where long single-stranded DNA linking DNA tetrahedra onto the surface of the magnetic beads is cleaved by a target DNA-activated CRISPR-cas12 system. The DNA tetrahedra are subsequently released and can be detected by the current pulse in a glassy nanopore. This approach has several advantages: (1) one signal transducer can be used to detect different targets; (2) a glassy nanopore with a pore size much larger than the target DNA fragment can boost the tolerance of the contaminants and interferents which often degrade the performance of a nanopore sensor.

Identification of N-glycan positional isomers by combining IMS and vibrational fingerprinting of structurally determinant CID fragments

Abstract: While glycans are present on the surface of cells in all living organisms and play key roles in most biological processes, their isomeric complexity makes their structural characterization challenging. Of particular importance are positional isomers, for which analytical standards are difficult to obtain. We combine ultrahigh-resolution ion-mobility spectrometry with collision-induced dissociation and cryogenic infrared spectroscopy to determine the structure of N-glycan positional isomers. This approach is based on first separating the parent molecules by SLIM-based IMS, producing diagnostic fragments specific to each positional isomer, separating the fragments by IMS, and identifying them by comparing their IR fingerprints to a previously recorded spectral database. We demonstrate this strategy using a bottom-up scheme to identify the positional isomers of the N-linked glycan G0-N, in which a terminal N-acetylglucosamine (GlcNAc) is attached to either the α-3 or α-6 branch of the common N-glycan pentasaccharide core. We then use IR fingerprints of these newly identified isomers to identify the positional isomers of G1 and G1F, which are biantennary complex-type N-glycans with a terminal galactose attached to either the α-3 or α-6 branch, and in the case of G1F a fucose attached to the reducing-end GlcNAc. Starting with just a few analytical standards, this fragment-based spectroscopy method allows us to develop a database which we can use to identify positional isomers. The generalization of this approach would greatly facilitate glycan analysis.

Immunoaffinity monoliths for multiplexed extraction of preterm birth biomarkers from human blood serum in 3D printed microfluidic devices.

Abstract: In an effort to develop biomarker-based diagnostics for preterm birth (PTB) risk, we created 3D printed microfluidic devices with multiplexed immunoaffinity monoliths to selectively extract multiple PTB biomarkers. The equilibrium dissociation constant for each monoclonal antibody toward its target PTB biomarker was determined. We confirmed the covalent attachment of three different individual antibodies to affinity monoliths using fluorescence imaging. Three different PTB biomarkers were successfully extracted from human blood serum using their respective single-antibody columns. Selective binding of each antibody toward its target biomarker was observed. Finally, we extracted and eluted three PTB biomarkers from depleted human blood serum in multiplexed immunoaffinity columns in 3D printed microfluidic devices. This is the first demonstration of multiplexed immunoaffinity extraction of PTB biomarkers in 3D printed microfluidic devices.

Target-driven assembly of DNAzyme probes for simultaneous electrochemical detection of multiplex microRNAs

Abstract: In this work, we employed target-driven assembly of a Mg2+-dependent DNAzyme to develop an ultrasensitive electrochemical biosensor for the simultaneous detection of miRNA-21 and miRNA-141. The target miRNAs could hybridize with two partial DNAzymes, facilitating the formation of a stable and active Mg2+-dependent DNAzyme. With the help of the Mg2+ cofactor, the DNAzyme could circularly cleave the ferrocene (Fc) or methylene blue (MB) labelled hairpin probes and release Fc and MB labels from the electrode surface, which could significantly amplify the current suppression to achieve multiple detection of small amounts of miRNA-21 and miRNA-141. This electrochemical biosensor showed high sensitivity and selectivity for the simultaneous detection of miRNA-21 and miRNA-141. Furthermore, the proposed method was also successfully applied for the determination of miRNA-21 and miRNA-141 from diluted serum samples. Overall, the proposed sensor showed several considerable advantages including simple preparation, high sensitivity, and enzyme-free signal amplification. Therefore, the proposed electrochemical biosensor could be used as a highly efficient amplification strategy for simultaneous detection of various miRNA biomarkers in bioanalysis and clinical diagnostics.

Rhodamine 6G-based efficient chemosensor for trivalent metal ions (Al3+, Cr3+ and Fe3+) upon single excitation with applications in combinational logic circuits and memory devices.

Abstract: A new rhodamine 6G-based chemosensor (L3) was synthesized and characterized by 1H, 13C, IR and mass spectroscopy studies. It exhibited an excellent selective and sensitive CHEF-based recognition of trivalent metal ions M3+ (M = Fe, Al and Cr) over mono and di-valent and other trivalent metal ions with prominent enhancement in the absorption and fluorescence intensity for Fe3+ (669-fold), Al3+ (653-fold) and Cr3+ (667-fold) upon the addition of 2.6 equivalent of these metal ions in the probe in H2O/CH3CN (7 : 3, v/v, pH 7.2). The corresponding Kd values were evaluated to be 1.94 × 10-5 (Fe3+), 3.15 × 10-5 (Al3+) and 2.26 × 10-5 M (Cr3+). The quantum yields of L3, [L3-Fe3+], [L3-Al3+] and [L3-Cr3+] complexes in H2O/CH3CN (7 : 3, v/v, pH 7.2) were found to be 0.0005, 0.335, 0.327 and 0.333, respectively, using rhodamine-6G as the standard. The LODs for Fe3+, Al3+ and Cr3+ were determined by 3σ methods and found to be 2.57, 0.78 and 0.47 μM, respectively. The cyanide ion snatched Fe3+ from the [Fe3+-L3] complex and quenched its fluorescence via its ring-closed spirolactam form. Advanced level molecular logic devices using different inputs (2 and 4 input) and a memory device were constructed.

Fluorescent sensor array based on aggregation-induced emission luminogens for pathogen discrimination.

Abstract: A high-throughput tetraphenylethylene (TPE)-based fluorescent sensor array was constructed for the identification and detection of microorganisms, which utilizes three TPE derivatives with different numbers of cationic side chains to detect and discriminate various microorganisms at concentrations down to 1 × 103 CFU mL-1.

Recent progress in small-molecule fluorescent probes for endoplasmic reticulum imaging in biological systems.

Abstract: Endoplasmic reticulum (ER) is an indispensable organelle in eukaryotic cells involved in protein synthesis and processing, as well as calcium storage and release. Therefore, maintaining the quality of ER is of great importance for cellular homeostasis. Aberrant fluctuations of bioactive species in the ER will result in homeostasis disequilibrium and further cause ER stress, which has evolved to contribute to the pathogenesis of various diseases. Therefore, the real-time monitoring of various bioactive species in the ER is of high priority to ascertain the mysterious roles of ER, which will contribute to unveiling the corresponding mechanism of organism disturbances. Recently, fluorescence imaging has emerged as a robust technique for the direct visualization of molecular events due to its outstanding sensitivity, high temporal-spatial resolution and noninvasive nature. In this review, we comprehensively summarize the recent progress in design strategies, bioimaging applications, potential directions and challenges of ER-targetable small-molecular fluorescent probes.

Smartphone clip-on instrument and microfluidic processor for rapid sample-to-answer detection of Zika virus in whole blood using spatial RT-LAMP

Abstract: Rapid, simple, inexpensive, accurate, and sensitive point-of-care (POC) detection of viral pathogens in bodily fluids is a vital component of controlling the spread of infectious diseases. The predominant laboratory-based methods for sample processing and nucleic acid detection face limitations that prevent them from gaining wide adoption for POC applications in low-resource settings and self-testing scenarios. Here, we report the design and characterization of an integrated system for rapid sample-to-answer detection of a viral pathogen in a droplet of whole blood comprised of a 2-stage microfluidic cartridge for sample processing and nucleic acid amplification, and a clip-on detection instrument that interfaces with the image sensor of a smartphone. The cartridge is designed to release viral RNA from Zika virus in whole blood using chemical lysis, followed by mixing with the assay buffer for performing reverse-transcriptase loop-mediated isothermal amplification (RT-LAMP) reactions in six parallel microfluidic compartments. The battery-powered handheld detection instrument uniformly heats the compartments from below, and an array of LEDs illuminates from above, while the generation of fluorescent reporters in the compartments is kinetically monitored by collecting a series of smartphone images. We characterize the assay time and detection limits for detecting Zika RNA and gamma ray-deactivated Zika virus spiked into buffer and whole blood and compare the performance of the same assay when conducted in conventional PCR tubes. Our approach for kinetic monitoring of the fluorescence-generating process in the microfluidic compartments enables spatial analysis of early fluorescent "bloom" events for positive samples, in an approach called "Spatial LAMP" (S-LAMP). We show that S-LAMP image analysis reduces the time required to designate an assay as a positive test, compared to conventional analysis of the average fluorescent intensity of the entire compartment. S-LAMP enables the RT-LAMP process to be as short as 22 minutes, resulting in a total sample-to-answer time in the range of 17-32 minutes to distinguish positive from negative samples, while demonstrating a viral RNA detection as low as 2.70 × 102 copies per μl, and a gamma-irradiated virus of 103 virus particles in a single 12.5 μl droplet blood sample.

Dual-channel detection of viscosity and pH with a near-infrared fluorescent probe for cancer visualization.

Abstract: Compared to ordinary cells, tumor cells have a unique microenvironment, characterized by high viscosity, low pH, high reactive oxygen species level and the overexpression of certain proteases. Therefore, viscosity and pH can be used as important parameters for visualizing cancer. We designed a spiro-oxazolidine compound (In-1) for the dual-channel detection of viscosity and pH, with the red channel for detecting viscosity and the blue channel for pH. Interestingly, In-1 can locate different organelles under different conditions. Under physiological conditions, In-1 efficiently targeted lysosomes and showed that the viscosity of lysosomes increases in cancer cells while the pH decreases, which can be used to distinguish and detect cancer cells and normal cells. When we treated HL-7702 cells with CCCP, the probe could effectively target the mitochondria, and the fluorescence intensity in the pH channel decreased. This indicates that In-1 can be used as a powerful tool to simultaneously monitor viscosity and pH in different organelles, and may have a guiding role in diseases caused by mitochondrial and lysosomal microenvironments.

Oxytocin detection at ppt level in human saliva by an extended-gate-type organic field-effect transistor.

Abstract: Herein, we report an extended-gate-type organic field-effect transistor (OFET) sensor for oxytocin. The fabricated OFET-based immunosensor has successfully detected oxytocin at a ppt level in human saliva with high recovery rates (96-102%). We believe our sensor would pave the way for the realization of portable sensors for healthcare monitoring.

Highly sensitive metal ion sensing by graphene oxide functionalized micro-tapered long-period fiber grating.

Abstract: An accurate as well as highly sensitive label-free chemical sensing platform for the detection of various metal ions was demonstrated. The chemical sensor was derived from the micro-tapered long-period fiber grating (MLPG) by depositing graphene oxide (GO) by chemical-bonding and optical-tweezer effects. The enhancement in refractive index (RI) sensitivity as well as reusability was obtained by evaluating the deposition thickness in the range of approximately 97.7 to 158.9 nm. Based on the analysis of adsorption principles, the enhanced RI sensitivity leads to a limit of detection as low as 3.2 ppb. The highest sensitivities for the cases studied using sodium and manganese ions in a wide concentration range of 1 ppb to 1 × 106 ppb are respectively 2.2 × 10-3 dB per ppb and 3.2 × 10-3 dB per ppb. Mixture samples were also studied to evaluate the properties of sensing the doped ions. This demonstration of GO modified MLPG is bound to find potential applications that require sensing of mixed samples and illustrates significant importance in developing cost-effective, label-free, reusable, and real-time chemical sensors.

Development of AIEE active fluorescent and colorimetric probe for the solid, solution, and vapor phase detection of cyanide: smartphone and food applications.

Abstract: Apart from environmental implications, the extreme toxicity of cyanide can lead to sudden human death upon prolonged exposure to it. Hence, rapid and low-level on-site detection of cyanide has earned paramount significance in the present era. Therefore, an AIEE active and piezofluorochromic Schiff base (probe 2) was synthesized which exhibited highly selective fluorescence enhancement based nanoscale (LOD; 6.17 nM) detection of CN-. The interaction mode was attributed to the deprotonation of the probe by the cyanide that was confirmed through 1H NMR titration, pH, theoretical studies, and switchable fluorescence response upon the addition of HCl. Advantageously, probe 2 displayed solid and vapor phase recognition of cyanide which is the first of its kind as far as we know. The excellent sensing potential of the probe was satisfactorily applied for the detection of cyanide in food, natural soil, and industrial wastewater. Additionally, probe 2 showed an immediate colorimetric response towards cyanide which was favorably integrated through a smartphone. Finally, the switchable fluorescence response of the probe was used to design an INHIBIT logic gate. Therefore, the multifunctional probe 2 displayed excellent practical potential for cyanide detection which was the ultimate goal of our work.

Fluorescence-based immunochromatographic test strip for the detection of hyoscyamine

Abstract: Hyoscyamine (HSM), which acts as an antagonist of the acetylcholine muscarinic receptor and can induce a variety of distinct toxic syndromes in mammals (anti-cholinergic poisoning), is hazardous to human health. Therefore, it is urgent to develop a rapid, sensitive, and cost-effective method to determine HSM. A fluorescent microsphere based immunochromatographic assay was developed for this analyte and gold nanoparticles (AuNPs) were used as a comparison. A monoclonal antibody against HSM was prepared with a 50% inhibition concentration (IC50) of 1.17 ng mL-1, with no cross-reactivity with five drugs. Under optimized conditions, the cut off limits using the fluorescence-labeled monoclonal antibody strips were 10 ng mL-1 in 0.01 M PBS and 20 ng mL-1 in pork, pig urine, and honey samples, and the assay could be completed within 10 min. In comparison with a AuNP immunochromatographic assay, the developed method offered a higher coupling rate and lower amounts of antibodies. This approach could be used for simple, sensitive and rapid screening, and is suitable for on-site screening applications.

A ZnFe2O4-catalyzed segment imprinted polymer on a three-dimensional origami paper-based microfluidic chip for the detection of microcystin.

Abstract: Microcystin has been causing serious environmental pollution; however, the recognition of such compounds is still challenging because of low abundance and coexisting interfering species. In this contribution, we develop a novel microfluidic paper-based colorimetric sensor by exploiting molecular imprinting technology and Fenton reaction for on-site microcystin-RR determination in complex water samples using a smartphone.

Isomeric separation of permethylated glycans by extra-long reversed-phase liquid chromatography (RPLC)-MS/MS.

Abstract: Glycosylation is known as a critical biological process that can largely affect the properties and the functions of proteins. Glycan isomers have been shown to be involved in a variety of disease progressions. However, the separation and identification of glycan isomers has been a challenge for years due to the microheterogeneity of glycan isomeric structures. Therefore, effective and stable techniques have been investigated over the last few decades to improve isomeric separations of glycans. RPLC has been widely used in biomolecule analysis because of its extraordinary reproducibility and reliability in retention time and separation resolution. However, so far, no studies have achieved high resolution of glycan isomers using this technique. In this study, we focused on further boosting the isomeric separation of permethylated glycans using a 500 mm reversed-phase LC column. To achieve better resolutions on permethylated glycans, different LC conditions were optimized using glycan standards, including core- and branch-fucosylated N-glycan isomers and sialic acid linked isomers, which were both successfully separated. Then, the optimal separation strategy was applied to achieve separations of N- and O-glycan isomers derived from model glycoproteins, including bovine fetuin, ribonuclease B and κ-casein. Baseline separations were observed on multiple sialylated linkage isomers. However, the separation performance of high-mannose isomers needs further improvement. The reproducibility and stability of this long C18 column was also tested by doing run-to-run, day-to-day and month-to-month comparisons of retention times on multiple glycans and the %RSD was found less than 0.92%. Finally, we applied this approach to separate glycan isomers derived from complex biological samples, including blood serum and cell lines, where baseline separations were attained on several isomeric structures. Compared to the separation efficiency of PGC and MGC columns, the RPLC C18 column provides lower resolution but more robust reproducibility, which makes it a good complementary alternative for isomeric separations of glycans.