Ultrasensitive Probe Research Articles

A Low-Dose, Ultra-Sensitive Probe for Sensing Esterase in Living Cells Based on Aggregation Induced Emission

A Low-Dose, Ultra-Sensitive Probe for Sensing Esterase in Living Cells Based on Aggregation Induced Emission

Magnetophotonics for sensing and magnetometry toward industrial applications

Magnetic nanostructures sustaining different types of optical modes have been used for magnetometry and label-free ultrasensitive refractive index probing, where the main challenge is the realization of compact devices that are able to transfer this technology from research laboratories to smart industry. This Perspective discusses the state-of-the-art and emerging trends in realizing innovative sensors containing new architectures and materials exploiting the unique ability to actively manipulate their optical properties using an externally applied magnetic field. In addition to the well-established use of propagating and localized plasmonic fields, in the so-called magnetoplasmonics, we identified a new potential of the all-dielectric platforms for sensing to overcome losses inherent to metallic components. In describing recent advances, emphasis is placed on several feasible industrial applications, trying to give our vision on the future of this promising field of research merging optics, magnetism, and nanotechnology.

Levitodynamics: Levitation and control of microscopic objects in vacuum.

The control of levitated nano- and micro-objects in vacuum—which capitalizes on scientific achievements in the fields of atomic physics, control theory, and optomechanics—is of considerable interest. The ability to couple the motion of levitated systems to internal degrees of freedom, as well as to external forces and systems, provides opportunities for science and technology. Attractive research directions, ranging from fundamental quantum physics to commercial sensors, have been unlocked by the many recent experimental achievements, including motional ground-state cooling of an optically levitated nanoparticle. Here we review the status, challenges, and prospects of levitodynamics, the multidisciplinary research area devoted to understanding, controlling, and using levitated nano- and micro-objects in vacuum.

Artificially engineered antiferromagnetic nanoprobes for ultra-sensitive histopathological level magnetic resonance imaging

Histopathological level imaging in a non-invasive manner is important for clinical diagnosis, which has been a tremendous challenge for current imaging modalities. Recent development of ultra-high-field (UHF) magnetic resonance imaging (MRI) represents a large step toward this goal. Nevertheless, there is a lack of proper contrast agents that can provide superior imaging sensitivity at UHF for disease detection, because conventional contrast agents generally induce T2 decaying effects that are too strong and thus limit the imaging performance. Herein, by rationally engineering the size, spin alignment, and magnetic moment of the nanoparticles, we develop an UHF MRI-tailored ultra-sensitive antiferromagnetic nanoparticle probe (AFNP), which possesses exceptionally small magnetisation to minimize T2 decaying effect. Under the applied magnetic field of 9 T with mice dedicated hardware, the nanoprobe exhibits the ultralow r2/r1 value (~1.93), enabling the sensitive detection of microscopic primary tumours (<0.60 mm) and micrometastases (down to 0.20 mm) in mice. The sensitivity and accuracy of AFNP-enhanced UHF MRI are comparable to those of the histopathological examination, enabling the development of non-invasive visualization of previously undetectable biological entities critical to medical diagnosis and therapy.

A H2 S-Specific Ultrasensitive Fluorogenic Probe Reveals TMV-Induced H2 S Production to Limit Virus Replication.

Understanding the role of H2 S in host defense mechanisms against RNA viruses may provide opportunities for the development of antivirals to combat viral infections. Here, we have developed a green-emitting fluorogenic probe, which exhibits a large fluorescence response at 520 nm (>560-fold) when treated with 100 μM H2 S for 1 h. It is highly selective for H2 S over biothiols (>400-fold F/F0 ) and has a detection limit of 12.9 nM. We demonstrate the application of the probe for endogenous H2 S detection in vivo for the understanding of its roles in antiviral host defense. Such virus-induced H2 S inhibits viral replication by reducing gene expression of RNA-dependent RNA polymerase (RdRp) and coat protein (CP). Additionally, a H2 S donor GYY4137 showed significantly antiviral activity as ribavirin, a broad-spectrum drug against RNA viruses. Furtherly, we propose a possible molecular mechanism for the TMV-induced H2 S biogenesis. This work provides a proof-of-principle in support of further studies identifying endogenous H2 S and its donors as potential antivirals toward RNA viruses.

Intrinsic hydroquinone-functionalized aggregation-induced emission core shows redox and pH sensitivity

Aggregation-induced emission (AIE) fluorophores exhibit strong fluorescence in an aggregated state but emit no or weak fluorescence in dilute solutions. This emerging class of AIE optical materials comprise a variety of functionalities. Here an AIE luminescence core, 1-hydroquinol-1,2,2-triphenylethene (HQTPE), has been designed and synthesized. This AIE core is simple but is fundamentally important to chemistry because of its intrinsic redox and pH activities. The incorporation of hydroquinone (HQ) moiety into a common AIE core tetraphenylethene (TPE) yields HQTPE with unique fluorescent properties like nonlinear self-quenching over most other AIE-active fluorophores (AIEgens) so far reported. There are differences of photochemical properties between HQTPE, 1-benzoquinol-1,2,2-triphenylethene (QTPE, the oxidized counterpart) and its anions. Interestingly, as the solution concentration is increased, AIEgen HQTPE shows stronger fluorescence but QTPE exhibits rapid quenching of fluorescence in a nonlinear fashion, which are in agreement with theoretical studies. The fluorescence of HQTPE is also highly dependent on the pH value of media. We have further explored HQTPE as an ultrasensitive redox probe and efficient deoxidizer, which could lead to potential applications in health care, food security, environmental monitoring, optic and electronic devices.

Nile Red-Based GPCR Ligands as Ultrasensitive Probes of the Local Lipid Microenvironment of the Receptor.

The local lipid microenvironment of transmembrane receptors is an essential factor in G protein coupled receptor (GPCR) signaling. However, tools are currently missing for studying endogenously expressed GPCRs in primary cells and tissues. Here, we introduce fluorescent environment-sensitive GPCR ligands for probing the microenvironment of the receptor in living cells using fluorescence microscopy under no-wash conditions. We designed and synthesized antagonist ligands of the oxytocin receptor (OTR) by conjugating a high-affinity nonpeptidic OTR ligand PF-3274167 to the environment-sensitive fluorescent dye Nile Red. The length of the polar PEG spacer between the pharmacophore and the fluorophore was adjusted to lower the nonspecific interactions of the probe while preserving a strong fluorogenic response. We demonstrated that the new probes embed into the lipid bilayer in the vicinity of the receptor and convey information about the local polarity and the lipid order via the wavelength-shifting emission of the Nile Red fluorophore.

Gold nanostar as an ultrasensitive colorimetric probe for picomolar detection of lead ion

The sensitivity for analytes of interest is vital for environment protection and food safety. Here, we propose an extremely sensitive assay toward Pb2+ by using gold nanostars (GNSs) as probes based on the catalytic activity of Pb on etching gold atoms after being reduced in the presence of 2-mercaptoethanol (2-ME) and sodium thiosulfate. GNSs were prepared by using 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid as both the reducing and capping agents, enabling high stability and sensitivity for quantitation of Pb2+. Upon increasing Pb2+ concentration over the range of 0–10 μM, GNS solution color changed from greenish-blue to blue to purple to red, and eventually to colorless. The color change can be distinguished by naked eye at the Pb2+ concentration as low as 200 pM. Through monitoring longitudinal localized surface plasmon of GNSs, Pb2+ could be detected with a limit of detection of 1.5 pM, and the working range is 2 pM-1 μM. The ultra-high sensitivity of our assay stems from the high catalysis of Pb on etching gold on tips and branches in the presence of 2-ME and sodium thiosulfate, leading to the shape deformation to spherical gold nanoparticle and the corresponding significant changes in their optical properties. The assay provides high selectivity of Pb2+ over the tested interfering metal ions like Cu2+. With high sensitivity and selectivity, the assay was efficiently validated by analyzing water samples and monitoring the migration of Pb2+ from the tested container to water.

Early Diagnosis of Cerebral Ischemia Reperfusion Injury and Revelation of Its Regional Development by a H3R Receptor-Directed Probe.

In vivo imaging of cerebral hydrogen peroxide (H2O2) may facilitate early diagnosis of cerebral ischemia reperfusion injury (CIRI) and a revelation of its pathological progression. In this study, we report our rational design of a brain-targeting fluorescent probe using the basis of a pyridazinone scaffold. A structure-activity relationship study reveals that PCAB is the best candidate (Ki = 15.8 nM) for a histamine H3 receptor (H3R), which is highly expressed in neurons of the central nervous system. As a two-photon fluorescent probe, PCAB exhibits a fast, selective reaction toward both extra- and intracellular H2O2 in SH-SY5Y cells under oxygen glucose deprivation and resupply. In vivo fluorescent imaging of a middle cerebral artery occlusion mouse confirms that PCAB is an ultrasensitive probe with potent blood-brain barrier penetration, precise brain targeting, and fast detection of CIRI.

Ultrasensitive fluorescence detection of bismuth ion (III) in plasma, urine and medicines by a terbium chelate probe

Abstract A novel, ultrasensitive probe of Bi3+ ion based on the fluorescence of a terbium chelate was presented and synthesized. This terbium chelate probe for Bi3+ is composed of a carbostyril-linked polyaminocarboxylate chelator and fluorescent terbium ion, and is highly fluorescent due to the sensitization of carbostyril to terbium ion. The extremely strong binding of polyaminocarboxylate chelator to Bi3+ replaced the binding of terbium ion, quenching the fluorescence of the probe. The probe based on this principle shows an ultra-high sensitivity for the detection of Bi3+ with a limit of detection as low as 0.1 pM in aqueous solution and 1 pM in urine and plasma solution respectively, at least 100-fold more sensitive than current various assays for Bi3+. The probe can be used to determine trace Bi3+ in medicines, urine and plasma. Due to a long fluorescence lifetime of the probe containing terbium ion, which allows the elimination of various short-lived nonspecific fluorescence via a time-delay measurement, this probe is particularly advantageous for the determination of biological samples like plasma and urine with autofluorescence.

Ultrasensitive Electrochemical Sensing of Biotin-Avidin Interaction on Gold Electrode Bio-Conjugated With Silver Nanoparticles

The influence of silver nanoparticles (AgNP) labeled with biomolecules on the electrochemical sensing of avidin-biotin interaction was investigated. Self-assembled monolayers of mercapto propionic acid on gold wire electrode were coupled with AgNP labeled biotin or avidin through bio-conjugation of complementary biomolecules. The electrochemical sensing of biotin-avidin interaction on the gold electrode modified with AgNP labeled biomolecules was compared with that of the unlabeled biomolecule layers. The sensing performances were studied using cyclic voltammetry and electrochemical impedance spectroscopy methods in ferric/ferrous redox system with varying concentration of bio-affinity molecules. The peak currents of AgNP labeled layers were gradually increased as concentration of bio-affinity molecules was increased in the electrolyte while opposite effect was observed for unlabeled layers. Here, the sensing mechanism was established to explain the role of AgNP as the electron transfer mediator. The AgNP modified electrode might be considered as ultrasensitive probe to detected biotin-avidin couple below 20 ng L−1 and to sense change of concentration above 10 or 20 ng L−1 at higher concentration region as well. This type of ultrasensitive detection of biotin-avidin interaction should be considered to explore robust and highly sensitive assays in combination with other primary-secondary antibodies for the bio-analyses, separations and clinical diagnostics.

An ultra-sensitive electrochemiluminescence probe based on ternary nanocomposite and boron nitride quantum dots for detection of diazinon.

Anew enzyme-free electrochemiluminescence (ECL) pesticide sensor was fabricated based on ternary nanocomposite of ruthenium nanoparticles/silver nanoparticles/graphene oxide on the surface of glassy carbon electrode for ultratrace determination of diazinon. Due to some drawbacks of enzyme-based sensors such as enzyme instability at elevatedtemperature, humidity, changes of pH, and high price of the enzyme, the use ofenzyme was omitted in the construction of the developed sensor. The silver nanoparticles with good electrocatalytic proficiency as a signal improving agent and tris(2,2bipyridine) ruthenium(II) as a popular luminophore were uniformly deposited on the surface of the prepared graphene oxide/GC electrode at nanoscale. Boron nitride quantum dots as an efficient co-reactant created the superior efficiency in amplifying the ECL intensity of the ruthenium-based ECL system. The prepared electrode was utilized for the detection of diazinon via the robust ECL method. For the present sensor, a wide linear dynamic range and low detection limit were achieved (3.0 × 10-15 to 6.5 × 10-9M and 9.5 × 10-16M, respectively). The obtained results confirmed the fabrication of the robust ECL probe, which is characterized by the cooperative effect of silver nanoparticles and the attached luminophore species. The main advantage of the presented sensor was that the samples could be diluted so that the effect of the interference species was negligible. Due to excellent properties toward accurate determination of diazinon, the ECL sensor as a new practical platform was applied for quantitative detection of diazinon in some real samples.

A nanobody\u2010horseradish peroxidase fusion protein\u2010based competitive ELISA for rapid detection of antibodies against porcine circovirus type 2

BackgroundThe widespread popularity of porcine circovirus type 2(PCV2) has seriously affected the healthy development of the pig industry and caused huge economic losses worldwide. A rapid and reliable method is required for epidemiological investigation and evaluating the effect of immunization. However, the current methods for PCV2 antibody detection are time-consuming or very expensive and rarely meet the requirements for clinical application. we have constructed the platform for expressing the nanobody(Nb)‑horseradish peroxidase(HRP) fusion protein as an ultrasensitive probe to detect antibodies against the Newcastle disease virus(NDV), previously. In the present work, an Nb-HRP fusion protein-based competitive ELISA(cELISA) for rapid and simple detection antibodies against PCV2 was developed using this platform to detect anti-PCV2 antibodies in clinical porcine serum.ResultsUsing phage display technology, 19 anti-PCV2-Cap protein nanobodies were screened from a PCV2-Cap protein immunized Bactrian camel. With the platform, the PCV2-Nb15‑HRP fusion protein was then produced and used as a sensitive reagent for developing a cELISA to detect anti‑PCV2 antibodies. The cut‑off value of the cELISA is 20.72 %. Three hundreds and sixty porcine serum samples were tested by both newly developed cELISA and commercial kits. The sensitivity and specificity were 99.68 % and 95.92 %, respectively. The coincidence rate of the two methods was 99.17 %. When detecting 620 clinical porcine serum samples, a good consistent (kappa value = 0.954) was found between the results of the cELISA and those of commercial kits.ConclusionsIn brief, the newly developed cELISA based PCV2-Nb15‑HRP fusion protein is a rapid, low-cost, reliable and useful nanobody-based tool for the serological evaluation of current PCV2 vaccine efficacy and the indirect diagnosis of PCV2 infection.

Dynamic change of MMP-9 in diabetic stroke visualized by optical imaging and treated with CD28 superagonist.

Type 2 diabetes mellitus is associated with an increased risk for stroke and unfavorable outcomes following stroke. Matrix metalloproteinase-9 (MMP-9) is a potential contributor to the poor prognosis of diabetic ischemic stroke. Investigations on diabetic stroke are limited by the lack of non-invasive imaging techniques. In this study, we report a fast and ultra-sensitive MMP-activatable optical imaging probe (MMP-P12) to achieve non-invasive and real-time visualization of the dynamic expression of MMP-9 in diabetic stroke. Moreover, by using this probe, we aim to detect the therapeutic efficacy of CD28 SA in diabetic stroke. Serial near-infrared fluorescence (NIRF) imaging was performed on wild-type and STZ-induced diabetic mice after MMP-P12 probe injection on days 1, 3, and 7 post ischemic stroke. The dynamic change in MMP-9 expression after CD28 SA treatment was also imaged on days 1, 3, and 7 post stroke and confirmed by immunohistochemistry staining and western blotting. NIRF imaging showed that diabetic stroke mice presented a trend of higher levels of MMP-9. CD28 SA treatment significantly downregulated the expression of MMP-9 on day 7 post stroke. Glucose also had a downward trend in CD28 SA treated diabetic stroke mice. In conclusion, our data suggest that MMP-P12 probe successfully detect the dynamic change of MMP-9 in diabetic stroke by utilizing optical imaging.CD28 SA treatment decreased the expression of MMP-9 and could be a promising therapeutic strategy for the treatment of diabetic stroke.

Ultrasensitive small molecule fluorogenic probe for human heparanase.

Heparanase (HPA) is a critical enzyme involved in the remodeling of the extracellular matrix (ECM), and its elevated expression has been linked with diseases such as various types of cancer and inflammation. The detection of heparanase enzymatic activity holds tremendous value in the study of the cellular microenvironment, and search of molecular therapeutics targeting heparanase, however, no structurally defined probes are available for the detection of heparanase activity. Here we present the development of the first ultrasensitive fluorogenic small-molecule probe for heparanase enzymatic activity via tuning the electronic effect of the substrate. The probe exhibits a 756-fold fluorescence turn-on response in the presence of human heparanase, allowing one-step detection of heparanase activity in real-time with a picomolar detection limit. The high sensitivity and robustness of the probe are exemplified in a high-throughput screening assay for heparanase inhibitors.

An ultrasensitive polarity-specific two-photon probe for revealing autophagy in live cells during scrap leather-induced neuroinflammation process.

A polarity-sensitive fluorescence probe AMN was developed to demonstrate the role of autophagy inhibitory drugs in the process of leather residue-induced neuroinflammation, promoting the knowledge of the relationship between autophagy and neuroinflammation. AMN showed a turn-on fluorescent signal in the process of autophagy inhibition via two-photon confocal imaging, which is different from the current popular autophagy probes. Therefore, AMN can offer high-sensitive imaging analysis of the autophagy inhibition process to better understand the role of autophagy in the process of neuroinflammation. The model of scrap leather-induced neuroinflammation using PC12 cells demonstrated that neuroinflammation can induce autophagy by releasing reactive oxygen species (ROS), and autophagy can alleviate neuroinflammation significantly via ROS scavenging.

Strong superchiral fields and an ultrasensitive chiral sensor of biomolecules based on a dielectric photonic crystal slab with air holes

Detection and quantification of chiral enantiomers of biomolecules are of considerable importance for biomedical diagnostics and pathogen analyses. However, the chiral signals from natural molecules are typically small and weak; a long measuring time and a large amount of samples are needed to fulfill the detection limit for the present technique. How to improve the detection efficiency for realizing ultrasensitive probing of chiral molecules has become a key problem. Here we propose a scheme to perform ultrasensitive detection of chiral molecules based on degeneracy states of orthogonal polarization modes in the achiral dielectric nanostructure. The degeneracy states are realized by designing dielectric photonic crystal slabs with air holes. Based on such degeneracy states, homogeneous superchiral fields of both handednesses over arbitrarily large areas can be obtained in a wide spectral range, resulting in the enhancement of the circular dichroism signal by more than three orders of magnitude, thus paving the road toward ultrasensitive characterization and quantification of molecular chirality.

Design of a dual functionalized chemiluminescence ultrasensitive probe for quinones based on their redox cycle. Application to the determination of doxorubicin in lyophilized powder and human serum

Quinones are ubiquitous compounds that have two-sided nature; a beneficial one, especially in the electron transport chain, and a toxic one through the generation of reactive oxygen species in vivo. Herein we developed a new dual-function chemiluminescence probe for their determination namely N-(4-aminobutyl)-N-ethylisoluminol-lipoic acid (ABEI-LA). This probe has two moieties, a reductant one, lipoic acid (LA), which upon its redox cycle reaction with quinones, generate superoxide anion, and the other moiety is the luminophore, ABEI, which generates intense chemiluminescence upon reaction with the generated superoxide anion. ABEI-LA is the first single reagent that could generate CL with quinones in a one-step operation. A simple rapid chemiluminescence assay for the anticancer drug, doxorubicin, was developed using ABEI-LA as a probe. The method showed good linearity towards doxorubicin in the range of 1−200 nM and excellent sensitivity with a detection limit of 0.17 nM (25 pg/assay). The proposed probe, ABEI-LA, was successfully applied for the quantification of doxorubicin, in lyophilized powder for injections and human serum samples and it showed very good recoveries of 84–91 % and 98–101 %, respectively. These results demonstrate the ability of ABEI-LA for the determination of quinones in different matrices enabling the in-depth study of quinones two-sided nature.

Ultrasensitive and reusable SERS probe for the detection of synthetic dyes in food industry through hybrid flower-shaped ZnO@Ag nanostructures

A reliable and accurate sensing of synthetic dyes in foodstuffs is highly significant to prevent health risks. Recently, various heterogeneous structures are used predominantly to explore the distinguished enhancement action of surface-enhanced Raman scattering (SERS) for ultrasensitive detection of multiple food colorants. Herein, we construct a semiconductor/noble-metal heterostructure by deposition of Ag nanoparticles (NPs) on flower-like ZnO microcrystals using a facile photoreduction method. The synergistic effect of flower-like ZnO@Ag nanostructures offers high SERS activity for detection of rhodamine 6G (R6G), sunset yellow (SY), and tartrazine (TZ) with an ultra-low detection limit of 10−12 M, 10−10 M, and 10−11 M, respectively. The flower-like ZnO@Ag nanostructures possess an excellent analytical enhancement factor, sensitivity, and uniformity, towards sensing multiple food colorants. Moreover, the self-reviving ability of the proposed flower-like ZnO@Ag nanostructures is demonstrated by UV-irradiation process and shows its excellent reusability on a single substrate for multiple SERS detection. This work demonstrates the promising use of semiconductor/noble-metal heterostructure with excellent reusability in real-time applications and food safety monitoring.

Development of peptide aptamers as alternatives for antibody in the detection of amyloid-beta 42 aggregates

Alzheimer's disease (AD) causes cognitive impairment and serious social isolation. However, there are no effective treatments and even no established confirmatory diagnostic tools for the disease. Amyloid beta (Aβ) aggregation in the brain is the best-known pathognomonic mechanism of AD, so various methods for Aβ detection have been developed for the diagnosis of this disease. We synthesized two novel, ultra-sensitive peptide probes specialized in detecting Aβ aggregates, and examined their potential for future diagnostic application. The peptides are produced through phage high-throughput screening (HTS) and amplified through a serial process called biopanning, which is a repeating method of elution and amplification of probes. We picked phages specific for amyloid from two kinds of phage display. The synthesized peptides were confirmed to have excellent binding affinity to Aβ aggregates, by immunohistochemical staining and western blotting using the brains of 3X transgenic (Tg) AD mice at different stages (5–7, 12–17 months old) of AD severity. In the present study, it was confirmed that newly developed amyloid-binding peptides could be used as novel probes for the detection of Aβ aggregates, which can be used for clinical diagnosis of AD in the future.