A dual-mode method for detection of miRNA based on the photoluminescence and resonance light scattering.

MicroRNAs (miRNAs) hold potential as useful biomarkers for early diagnosis and evaluation of diverse cancers, but their low abundance and short length make the detection of miRNAs face low sensitivity and accuracy. Herein, a photoluminescence (PL)-resonance light scattering (RLS) dual-mode method was developed for the sensitive and accurate detection of miRNA-141 using CdTe quantum dots (QDs) and Au nanoparticles. The presence of miRNA-141 induced PL quenching and RLS increasing. The limit of detection (LOD) was as low as 3.7 fM, and the miRNA-141 was detected linearly in a range from 10 fM to 10 nM. The dual signals generated no mutual interference and were detected using the same spectrophotometer, allowing for mutual validation to ensure the accuracy and reliability of the detection results. This study proposes valuable references for constructing dual-mode detection methods.

Photoluminescent and multi-phonon resonance Raman scattering dual-mode immunoassays based on CdS nanoparticles for HIgG detection.

A dual-mode immunoassay strategy based on CdS nanoparticles as signal probes with both of photoluminescent (PL) and multi-phonon resonance Raman scattering (MRRS) properties was developed. Simplified structural design and preparation were achieved due to the intrinsic integration of PL and MRRS dual signals in the single-unit CdS nanoprobes. Human immunoglobulin G (HIgG) was sensitively and specifically detected using the proposed PL-MRRS dual-mode strategy. The linear relationship between the HIgG concentration and the intensity of 707 nm PL peaks/300 cm-1 MRRS peaks under the excitation of 488 nm laser was established. The limit of detection was 0.93 fg mL-1 for PL and 1.10 fg mL-1 for MRRS. In comparison with previous IgG detection methods, the proposed method exhibited prominent advantages in detection sensitivity and working range with good stability and repeatability. An internal self-calibration was realized which ensured the accuracy and reliability of detection results. Both results of specificity experiments and serum sample analysis further confirmed the feasibility of the designed immunoassay strategy in practical serological detection.

A dual-mode immunosensing strategy for prostate specific antigen detection: Integration of resonance Raman scattering and photoluminescence properties of ZnS:Mn2+ nanoprobes.

Luminescence-based methods are widely used for the detection of prostate specific antigen (PSA), for example during the diagnosis of prostate cancer. However, the accuracy of these methods is sub-optimal. The aim of this study was to develop an accurate and sensitive dual-mode immunosensing technique using a combination of resonance Raman scattering (RRS) and photoluminescence (PL) signals for the detection of PSA. A ZnS:Mn2+ nanoprobe was used as the signal reporter, which exhibits both multi-phonon RRS and PL properties. The RRS signal intensity at 348 cm-1 and the PL signal intensity at 590 nm were used for the quantitative assay of PSA. The reproducibility, selectivity and specificity of this dual-mode immunosensing strategy demonstrated an improvement compared with commercial PSA ELISA kits in the analysis of serum samples. Therefore, the RRS-PL immunosensing technique developed in this study shows potential as a reliable technique to be used in the clinical diagnosis of prostate cancer.

ALA_PDT Promotes Ferroptosis-Like Death of Mycobacterium abscessus and Antibiotic Sterilization via Oxidative Stress.

Mycobacterium abscessus is one of the common clinical non-tuberculous mycobacteria (NTM) that can cause severe skin infection. 5-Aminolevulinic acid photodynamic therapy (ALA_PDT) is an emerging effective antimicrobial treatment. To explore whether ALA_PDT can be used to treat M. abscessus infections, we conducted a series of experiments in vitro. We found that ALA_PDT can kill M. abscesses. Mechanistically, we found that ALA_PDT promoted ferroptosis-like death of M. abscesses, and the ROS scavenger N-Acetyl-L-cysteine (NAC) and ferroptosis inhibitor Ferrostatin-1 (Fer-1) can mitigate the ALA_PDT-mediated sterilization. Furthermore, ALA_PDT significantly up-regulated the transcription of heme oxygenase MAB_4773, increased the intracellular Fe2+ concentration and altered the transcription of M. abscessus iron metabolism genes. ALA_PDT disrupted the integrity of the cell membrane and enhanced the permeability of the cell membrane, as evidenced by the boosted sterilization effect of antibiotics. In summary, ALA_PDT can kill M. abscesses via promoting the ferroptosis-like death and antibiotic sterilization through oxidative stress by changing iron metabolism. The study provided new mechanistic insights into the clinical efficacy of ALA_PDT against M. abscessus.

Identification and Expression Analysis of WRKY Gene Family in Response to Abiotic Stress in Dendrobium catenatum.

Dendrobium catenatum has become a rare and endangered medicinal plant due to habitat loss in China. As one of the most important and largest transcription factors, WRKY plays a critical role in response to abiotic stresses in plants. However, little is known regarding the functions of the WRKY family in D. catenatum. In this study, a total of 62 WRKY genes were identified from the D. catenatum genome. Phylogenetic analysis revealed that DcWRKY proteins could be divided into three groups, a division supported by the conserved motif compositions and intron/exon structures. DcWRKY gene expression and specific responses under drought, heat, cold and salt stresses were analyzed through RNA-seq data and RT-qPCR assay. The results showed that these genes had tissue-specificity and displayed different expression patterns in response to abiotic stresses. The expression levels of DcWRKY22, DcWRKY36 and DcWRKY45 were up-regulated by drought stress. Meanwhile, DcWRKY22 was highly induced by heat in roots, and DcWRKY45 was significantly induced by cold stress in leaves. Furthermore, DcWRKY27 in roots and DcWRKY58 in leaves were extremely induced under salt treatment. Finally, we found that all the five genes may function in ABA- and SA-dependent manners. This study identified candidate WRKY genes with possible roles in abiotic stress and these findings not only contribute to our understanding of WRKY family genes, but also provide valuable information for stress resistance development in D. catenatum.

A self-floating electrospun nanofiber mat for continuously high-efficiency solar desalination.

Solar desalination is an environment-friendly and sustainable technology to address the shortage of freshwater resources. However, it still faces huge challenges to develop a salt-rejection solar desalination system with continuous high efficiency. Herein, an electrospun nanofiber mat was fabricated for continuously high-efficiency solar desalination with carbon nanotube as a photothermal material, polyvinylidene fluoride as a floating support material and polyvinylpyrrolidone as a pore-forming agent. The porous structure and superhydrophilic surface provide significant water transport channels and thus avoid salt deposition, even in the high-salinity brine (20 wt% NaCl). The integration of strong broadband absorption property, excellent photothermal performance, floatability, durability and stability endows the solar desalination system with continuously high evaporation efficiency. The evaporation rate and solar conversion efficiency reached up to 1.372 kg m-2 h-1 and 86.1%, respectively, in simulated seawater under one sun irradiation and lasted for 11 h with little fluctuation. This work opens a new avenue for the rational design and fabrication of solar desalination systems to promote practical application.

Fluorescence-infrared absorption dual-mode nanoprobes based on carbon dots@SiO2 nanorods for ultrasensitive and reliable detection of carcinoembryonic antigen.

The level of carcinoembryonic antigen (CEA) in serum has the significant reference value for early diagnosis and treatment of various cancers. However, the CEA detection still suffers from the issue of limited sensitivity and reliability. Herein, a fluorescence (FL)-infrared absorption (IRA) dual-mode nanoprobe was fabricated based on carbon dots (CDs)@SiO2 nanorod for CEA detection. The FL and IRA signals display no mutual interference and can verify each other, ensuring the reliability of assay results. The highly sensitive FL signal originating from the CDs is enhanced by the surface passivation of SiO2 and improves the overall sensitivity of the detection. The detection range spans 9 orders of magnitude and the limit of detection reaches 794.6 ag mL-1, which are great superior to the commercial kits and most of the previous reports. Satisfactory recovery over the commercial kits was achieved in real serum samples. The ultrasensitive and reliable FL-IRA detection strategy sheds light on a new avenue toward promoting the practicability of the nanoprobes in clinical cancer diagnosis.

Upconversion luminescence-infrared absorption nanoprobes for the detection of prostate-specific antigen.

Aiming to the ongoing challenge of accurate and sensitive detection for cancer biomarkers, antibody-functionalized NaYF4:Yb3+, Er3+@SiO2 nanorods were developed as upconversion luminescence (UCL)-infrared absorption (IRA) nanoprobes. Benefiting from the shielding effect of the SiO2 shell, an enhanced UCL was achieved. Additionally, an IRA detection signal was introduced by the Si-O-Si bonds of SiO2. Its mutual verification with UCL signal was favorable for ensuring the accuracy of the assay. A UCL-IRA sandwich detection method was established for the detection of the prostate-specific antigen. The UCL intensity at 542 nm and IRA at 1095 cm-1 were chosen for quantitative assay. The method has high sensitivity (0.05 pg mL-1) and selectivity. The range of detection (200 fg mL-1-200 ng mL-1) was singnificantly broadened compared with that of single-readout UCL or IRA detection. The assay performance of human serum samples demonstrated the practicability of the method in clinical cancer diagnosis. Graphical abstract.

Resonance Raman scattering-infrared absorption dual-mode immunosensing for carcinoembryonic antigen based on ZnO@SiO2 nanocomposites.

Detection of cancer biomarkers is crucial for the diagnosis and monitoring of malignant tumors. However, the accuracy and sensitivity still require sufficient improvement for practically clinical application. In this work, a reliable and sensitive dual-mode immunosensing method is described for carcinoembryonic antigen (CEA) detection using a biofunctional ZnO@SiO2 nanocomposite as a resonance Raman scattering (RRS)-infrared (IR) absorption nanoprobe. The multiphonon RRS signal originating from the ZnO and the characteristic IR fingerprint signal of the transverse optical and longitudinal optical phonon modes of the asymmetric stretching of Si-O-Si bonds showed no interference with each other. A CEA antibodies-immobilized substrate was fabricated to capture the analyte/nanoprobe complexes. The RRS intensity at 569 cm‒1 and the IR absorption at 1061 cm‒1 were used for quantitative analysis. Accurate CEA detection was performed as a result of the strong resistance of the dual-mode nanoprobe to surrounding interference. The limit of detection was 98.0 fg mL‒1. The detection range was 500 ng mL‒1 - 50 fg mL‒1, which is wider than those of single-mode RRS or IR absorption immunosensings. High reproducibility, selectivity and specificity were achieved. The assay performance of human serum samples demonstrated the practicability of the method in clinical cancer diagnosis.

Colorimetric determination of copper(II) by using branched-polyethylenimine droplet evaporation on a superhydrophilic-superhydrophobic micropatterned surface.

A colorimetric method is described for the determination of Cu(II). It is based on branched polyethylenimine (BPEI) droplet evaporation on a superhydrophilic-superhydrophobic polystyrene micropatterned surface. Exposure to Cu(II) leads to a color change from colorless to light blue and dark blue. The micropatterned surface was fabricated via combining electrospinning with oxygen plasma and served as a detection substrate. Analysis requires only a single drop of blood. The method has a linear response in the 5.0 µM to 2.5 mM Cu(II) concentration range which is within the physiological range (15.7 ∼ 23.6 µM). Compared to an assay in solution, the detection limit is decreased from 386 nM to 89 nM. Excellent selectivity over other metal ions and anions was achieved. Graphical abstract A rapid and sensitive colorimetric detection platform for Cu(II) was fabricated by using branched-polyethylenimine droplet evaporation on a superhydrophilic-superhydrophobic micropatterned surface. Only a single drop of blood was needed for the analysis. The sensitivity was improved about 4.3 times.

Recent Advances in Magnetic Upconversion Nanocomposites for Bioapplications.

The combination of magnetism and upconversion luminescent property into one single nanostructure is fascinating for biological fields, such as multimodal bioimaging, targeted drug delivery, and imaging-guided therapy. In this review, we will provide the state-of-the-art advances on magnetic upconversion nanocomposites towards their bioapplications. Their structure design, synthesis methods, surface engineering and applications in bioimaging, drug delivery, therapy as well as biodetection will be covered.

Multifunctional NaYF4:Yb,Er@PE3@Fe3O4 nanocomposites for magnetic-field-assisted upconversion imaging guided photothermal therapy of cancer cells.

Even though various theranostic agents have been exploited for effective cancer therapy over the years, appropriate design and fabrication of theranostic agents with simple composition, convenient preparation, high theranostic efficiency and minimal side effects on non-cancer cells are still urgently needed. Herein, multifunctional NaYF4:Yb,Er@polyelectrolyte (PE3)@Fe3O4 nanocomposites, with upconversion luminescence, superparamagnetism and photothermal performance, are prepared by a layer-by-layer self-assembly technique. Compared with Fe3O4 nanoparticles (NPs), the nanocomposites exhibited nearly 2-fold strong absorption at 808 nm, and thus resulted in an enhanced near-infrared photothermal effect. With the assistance of an external magnetic field, a high sensitivity of upconversion fluorescence imaging and a low cancer cell viability of 13.9% were achieved under 808 nm laser irradiation. It is expected that multifunctional NaYF4:Yb,Er@PE3@Fe3O4 nanocomposites would pave the way toward promoting the clinical applications of theranostic nanomaterials.

An infrared IgG immunoassay based on the use of a nanocomposite consisting of silica coated Fe3O4 superparticles.

A reliable, rapid and ultrasensitive immunoassay is described for determination of immunoglobulin G (IgG). It is making use of biofunctional magnetite (Fe3O4) superparticles coated with SiO2 and serving as an infrared (IR) probe. The unique IR fingerprint signals originating from the transverse and longitudinal phonon modes, respectively, of the asymmetric stretching of the Si-O-Si bridges display a satisfactory resistance to optical interference from the environment. The adoption of Fe3O4 superparticles instead of Fe3O4 nanoparticles as the magnetic core warrants a controllable structure and a strong magnetic response. This facilitates the efficient purification of the probes and the alleviation of the interfacial resistance between the liquid-solid interfaces by using a magnet. The gold-coated substrate was used to immobilize goat-anti-human IgG. The analyte (human IgG) was incubated with the IR probes, and then captured by the substrate immobilized antibody with the assistance of an external magnetic field. The integral area of the IR absorption band between 1250 cm-1 - 900 cm-1 was chosen for quantitative assay. The limit of detection is 95 fM, which is two orders of magnitude better than that without the magnetic field. The assay time was shortened from 2 h to 1 min. High selectivity, specificity, and long-term stability of the immunoassay were achieved. The performance of the assay when analyzing blood samples confirmed the practicability of the method. Graphical abstract Schematic presentation of the infrared (IR) immunoassay based on Fe3O4 superparticle@SiO2 nanocomposites. The assistance of an external magnetic field reduces the incubation time and improves the detection sensitivity.

An "off-on" colorimetric and fluorometric assay for Cu(II) based on the use of NaYF4:Yb(III),Er(III) upconversion nanoparticles functionalized with branched polyethylenimine.

The authors describe an "off-on" colorimetric and fluorometric assay for the determination of Cu(II). It is based on the use of upconversion nanoparticles (UCNPs) of type NaYF4:Yb(III),Er(III) that were functionalized with branched polyethylenimine (BPEI). A color change from colorless to blue occurs within 2 s after addition of Cu(II) to a solution of the modified UCNPs. The color change can be visually detected at Cu(II) concentrations down to 80 µM. The upconversion fluorescence of the modified UCNPs, measured at excitation wavelength of 980 nm, is reduced due to the predominant inner filter effect caused by the formation of the BPEI-Cu(II) complex. Normalized fluorescence intensity drops linearly in the 50 nM to 10 µM Cu(II) concentration range, and the fluorometric detection limit is 45 nM. Both the color and the fluorescence are recovered on addition of EDTA. Excellent selectivity over other metal ions and anions is achieved. Graphical abstract Upconversion nanoparticles of type NaYF4:Yb,Er were functionalized with branched polyethylenimine (UCNP/BPEI) and used in an "off-on" colorimetric and fluorometric assay for Cu(II). The upconversion fluorescence is selectively quenched on addition of Cu(II), and this is accompanied by a rapid colorless-to-blue color switch. The colorimetric changes and quenched fluorescence can be reversed by adding EDTA.

Ultra-facile and rapid colorimetric detection of Cu2+ with branched polyethylenimine in 100% aqueous solution.

The detection of copper ion (Cu2+) has become a long-term and arduous task in the field of environmental monitoring and human health. Current methods based on branched polyethylenimine (BPEI) for the detection of Cu2+ more or less suffer from being time-consuming and having a high cost or complex surface modifications. Herein, an ultra-facile and rapid colorimetric method was explored to detect Cu2+ in 100% aqueous solution by a direct format using only BPEI. Cu2+ could be captured by BPEI and form BPEI-Cu2+ complexes, which resulted in a color change from colorless to blue within 5 s, associated with the strong absorption peak at 278 nm. The lower the molecular weight and the concentration of BPEI are, the lower the detection limit is. When the molecular weight and the concentration of BPEI were 600 and 21.5 mg L-1, respectively, the detection limit was calculated to be 1.21 µM, and the linear range was 2 µM to 50 µM. Besides, BPEI also had an excellent selectivity toward Cu2+. This ultra-facile, rapid and inexpensive method offers great potential for various applications in biomedicine, environmental protection, food safety and so on.

Dual-mode immunoassay based on shape code and infrared absorption fingerprint signals of silica nanorods.

Silica nanorods were synthesized through a simple one-pot emulsion-droplet-based growth method, in which tetraethylorthosilicate (TEOS) was used as the silica source, ammonia as the catalyst, and polyvinylpyrrolidone (PVP) as the structure-directing agent and stabilizer. By controlling hydrolysis and condensation in the reaction process, we regulated the aspect ratios and the infrared (IR) absorption fingerprint signals (the transverse optical and the longitudinal optical phonon modes) of the silica nanorods. Based on this, a dual-mode immunoassay was performed for detecting model target analyte, human IgG. The shape code of the silica nanorods was used for simple, rapid qualitative, and sensitive semi-quantitative immunoassay by using a conventional optical microscope. The characteristic IR absorption fingerprint signals of the silica nanorods allowed for reliable quantitative immunoassay with good selectivity and high specificity. The detection limit and the linear range were found out to be 0.5 pM and 1 pM-10 nM, respectively. We expect that such dual-mode immunoassay could be applied for the detection of other analytes, such as protein, nucleic acids, bacteria, viruses, explosives, toxins, and so on. Graphical abstract A simple dual-mode immunoassay was performed using the shape code and infrared absorption fingerprint signals of silica nanorods as detection signals.

Solvent-Induced Luminescence Variation of Upconversion Nanoparticles.

Solvent plays a vital role in the syntheses, purifications, and broad applications of upconversion nanoparticles (UCNPs). In this work, the effect of various dispersive solvents, including single solvents and mixed solvents, on the luminescence properties of NaYF4:Yb3+, Er3+ UCNPs was studied systematically. The differences in both upconversion luminescence (UCL) intensities and color outputs of the nanoparticles were observed when dispersing the UCNPs in deuterium oxide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, or water. The attenuation of the excitation and emission light of the UCNPs caused by absorption of the solvents, as well as the high-frequency vibrational groups of the solvents, such as -OH, -CH2, and -CH3 groups, are responsible for the decrease in UCL intensities and increase in the red to green emission intensity ratios (RGR). The changes in water or OH- ion contents of ethanol/water mixed solvent triggered similar changes in UCL properties. Interestingly, the quenching of the solvents for the UCL cannot be fully eliminated by changing the dispersive solvents once the UCNPs have touched the solvents containing high-frequency vibrational groups. Our work will facilitate the comprehension of the solvent induced luminescence variations of the nanoparticles and provide guidance for their applications.

Magnetic-bead-based sub-femtomolar immunoassay using resonant Raman scattering signals of ZnS nanoparticles.

Highly sensitive, specific, and selective immunoassays are of great significance for not only clinical diagnostics but also food safety, environmental monitoring, and so on. Enzyme-linked immunosorbent assays and fluorescence-based and electrochemical immunoassays are important intensively investigated immunoassay techniques. However, they might suffer from low sensitivity or false-positive results. In this work, a simple, reliable, and ultrasensitive magnetic-bead-based immunoassay was performed using biofunctionalized ZnS semiconductor nanocrystals as resonant Raman probes. The resonant Raman scattering of ZnS nanocrystals displays evenly spaced multi-phonon resonant Raman lines with narrow bandwidths and has strong resistance to environmental variation due to the nature of the electron-phonon interaction, thus rendering reliable signal readout in the immunoassays. The superparamagnetic Fe3O4 nanoparticles facilitated greatly the separation, purification, and concentration processes. It is beneficial for both reducing the labor intensity and amplifying the detection signals. The immobilization of antibodies on the surface of magnetic beads, the preparation of resonant Raman probes, and the immunological recognition between the antibody and analyte all occurred in the liquid phase, which minimized the diffusion barriers and boundary layer constraints. All these factors contributed to the ultralow detection limit of human IgG, which was determined to be about 0.5 fM (∼0.08 pg/ml). It is nearly the highest sensitivity obtained for IgG detection. This work shall facilitate the design of nanoplatforms for ultrasensitive detections of proteins, DNAs, bacteria, explosives, and so on. Graphical abstract An ultrasensitive magnetic-bead-based immunoassay was performed using multi-phonon resonant Raman lines of ZnS nanoparticles as detection signals.

Interplay between Static and Dynamic Energy Transfer in Biofunctional Upconversion Nanoplatforms.

Clarification of the energy-transfer (ET) mechanism is of vital importance for constructing efficient upconversion nanoplatforms for biological/biomedical applications. Yet, most strategies of optimizing these nanoplatforms were casually based on a dynamic ET assumption. In this work, we have modeled quantitatively the shell-thickness-dependent interplay between dynamic and static ET in nanosystems and validated the model in a typical biofunctional upconversion nanoplatform composed of NaYF4:Er, Yb/NaYF4 upconversion nanoparticles (UCNPs), and energy-acceptor photosensitizing molecule Rose Bengal (RB). It was determined that with a proper thickness shell, the energy transferred via dynamic ET as well as static ET in this case could be significantly improved by ∼4 and ∼9 fold, respectively, compared with the total energy transferred from bare core UCNPs. Our results shall form the bedrock in designing highly efficient ET-based biofunctional nanoplatforms.

Targeted labeling of an early-stage tumor spheroid in a chorioallantoic membrane model with upconversion nanoparticles.

In vivo detection of cancer at an early-stage, i.e. smaller than 2 mm, is a challenge in biomedicine. In this work target labeling of an early-stage tumor spheroid (∼500 µm) is realized for the first time in a chick embryo chorioallantoic membrane (CAM) model with monoclonal antibody functionalized upconversion nanoparticles (UCNPs-mAb).