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The global challenges posed by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic have underscored the critical importance of innovative and efficient control systems for addressing future pandemics. The most effective way to control the pandemic is to rapidly suppress the spread of the virus through early detection using a rapid, accurate, and easy-to-use diagnostic platform. In biosensors that use bioprobes, the binding affinity of molecular recognition elements (MREs) is the primary factor determining the dynamic range of the sensing platform. Furthermore, the sensitivity relies mainly on bioprobe quality with sufficient functionality. This comprehensive review investigates aptamers and nanobodies recently developed as advanced MREs for SARS-CoV-2 diagnostic and therapeutic applications. These bioprobes might be integrated into organic bioelectronic materials and devices, with promising enhanced sensitivity and specificity. This review offers valuable insights into advancing biosensing technologies for infectious disease diagnosis and treatment using aptamers and nanobodies as new bioprobes. [ABSTRACT FROM AUTHOR]

The global challenges posed by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic have underscored the critical importance of innovative and efficient control systems for addressing future pandemics. The most effective way to control the pandemic is to rapidly suppress the spread of the virus through early detection using a rapid, accurate, and easy-to-use diagnostic platform. In biosensors that use bioprobes, the binding affinity of molecular recognition elements (MREs) is the primary factor determining the dynamic range of the sensing platform. Furthermore, the sensitivity relies mainly on bioprobe quality with sufficient functionality. This comprehensive review investigates aptamers and nanobodies recently developed as advanced MREs for SARS-CoV-2 diagnostic and therapeutic applications. These bioprobes might be integrated into organic bioelectronic materials and devices, with promising enhanced sensitivity and specificity. This review offers valuable insights into advancing biosensing technologies for infectious disease diagnosis and treatment using aptamers and nanobodies as new bioprobes.

Bioprobe based on fluorescence is widely used in biological and medical research due to its high sensitivity and selectivity. Yet, its quantification in vivo is complicated and often compromised by the interaction between the fluorophore with the environmental factors, as well as the optical scattering and absorption by the tissue. A high florescence quantum yield and minimal interference by the environment are key requirements for designing an effective bioprobe, and the pre-requisitions severely limit the available options. We propose that a comprehensive evaluation of potential bioprobe can be achieved by simultaneously measuring both radiative and non-radiative transitions, the two fundamental and complementary pathways for the energy de-excitation. This approach will not only improve the accuracy of the quantification by catching the information from a broader spectrum of the energy, but also provide additional information of the probe environment that often impacts the balance between the two forms of the energy transition. This work first analyzes the underlying mechanism of the hypothesis. The practical feasibility is then tested by means of simultaneous measurements of photoacoustic signal for the non-radiative and fluorescence for the radiative energy processes, respectively. It is demonstrated that the systematic evaluation of the probe energy de-excitation results in an improved quantitative tracing of a bioprobe in complex environment. [ABSTRACT FROM AUTHOR]

Bioprobe based on fluorescence is widely used in biological and medical research due to its high sensitivity and selectivity. Yet, its quantification in vivo is complicated and often compromised by the interaction between the fluorophore with the environmental factors, as well as the optical scattering and absorption by the tissue. A high florescence quantum yield and minimal interference by the environment are key requirements for designing an effective bioprobe, and the pre-requisitions severely limit the available options. We propose that a comprehensive evaluation of potential bioprobe can be achieved by simultaneously measuring both radiative and non-radiative transitions, the two fundamental and complementary pathways for the energy de-excitation. This approach will not only improve the accuracy of the quantification by catching the information from a broader spectrum of the energy, but also provide additional information of the probe environment that often impacts the balance between the two forms of the energy transition. This work first analyzes the underlying mechanism of the hypothesis. The practical feasibility is then tested by means of simultaneous measurements of photoacoustic signal for the non-radiative and fluorescence for the radiative energy processes, respectively. It is demonstrated that the systematic evaluation of the probe energy de-excitation results in an improved quantitative tracing of a bioprobe in complex environment.

[Display omitted] • Electroporation-based delivery of pH bioprobes into live cells enables rapid intracellular pH measurement and analysis. • Electroporation-based delivery of nanoprobes enables their dispersal throughout the cytoplasm, allowing for the capture of pH information throughout the cell. In this study, electroporation-surface-enhanced Raman scattering (SERS) was applied to rapidly measure intracellular pH. The generation of a sensitive SERS probe for measuring pH in the range of 6.0–8.0 was accomplished through the conjugation of the pH-sensitive molecule 4-mercaptobenzoic acid (4-MBA) to the surface of gold nanoparticles (Au NPs) through its thiol functional group. This bioprobe was then rapidly introduced into nasopharyngeal carcinoma CNE-1 cells by electroporation, followed by SERS scanning and the fitting of intensity ratios of each detection point's Raman peaks at 1423 cm−1 and 1072 cm−1, to create the pH distribution map of CNE-1 cells. The electroporation-SERS assay introduces pH bioprobes into a living cell in a very short time and disperses the nanoprobe throughout the cytoplasm, ultimately enabling rapid and comprehensive pH analysis of the entire cell. Our work demonstrates the potential of electroporation-SERS for the biochemical analysis of live cells. [ABSTRACT FROM AUTHOR]

Fire blight, caused by the bacterium Erwinia amylovora , is a rapidly progressing and highly contagious disease of apple and pear, which leads to great economic losses with high recovery fees. To control fire blight, the infected trees are either treated with antibiotics or, in some countries, buried. To minimize the damage caused by E. amylovora and to manage its spread to other trees and orchards, early diagnosis of fire blight is critical. The direct extraction of E. amylovora cells or DNA from infected tissues is a laborious and time-consuming process, and a non-destructive diagnosis method has not yet been applied. In this study, we employed receptonics, a nanotechnology platform equipped with a receptor protein that perceives airborne bacterial signals and converts them into electronic signals, for onsite fire blight diagnosis. Two bacterial volatiles, 2,3-butanediol and 2-phenylethyl alcohol, were used as E. amylovora biomarkers both in vitro and in situ. To design receptor protein for identifying the target biomarkers, the bioprobe, nanodiscs human olfactory receptor family 1 subfamily D member 5 (hOR1D5), and Drosophila melanogaster or9a were engineered and fabricated. Our portable receptonics platform was able to detect both bacterial volatiles at concentrations as low as 10 pM within 10 s under field conditions. Thus, our results suggest that the receptonics platform could be used as a non-destructive diagnostic tool for the onsite, rapid, and accurate identification of plant diseases. • Fire blight is one of the major concerns in the agriculture field. • Early detection of the causing bacteria (E. amylovora) is important for Fire blight prevention. • A portable receptonics for on-site utilizing was developed. • The portable receptonics were demonstrated by monitoring in orchards. [ABSTRACT FROM AUTHOR]

That sulfide anions (S2−) in aquatic environments are produced by microorganisms through degrading sulfur-containing proteins and other organics are harmful to human health. Thus, it is of significance to develop a convenient method for the detection of S2− in water. Small molecular fluorescent probes are very popular for their advantages of visualization, real-time, high sensitivity, and convenience. However, low solubility in water limits the application of existing S2− probes. In this work, we found that our previously developed water-soluble glycosylated fluorescent bioprobe Cu[GluC] can achieve detection of S2− in water. Cu[GluC] can restore fluorescence within 20 s when it encounters S2− and shows good sensitivity towards S2− with a detection limit of 49.6 nM. Besides, Cu[GluC] derived fluorescent test strips were obtained by immersion and realized conveniently visual S2− detection in water by coupling with a UV lamp and a smartphone app. This work provides a fluorescent bioprobe with good water solubility as well as its derived fluorescent test strip for sensitive and simple detection of S2− in water, which shows good prospects in on-site water quality monitoring. [ABSTRACT FROM AUTHOR]

As a functional dye, cyanine dye promotes the widespread application of bioprobes in the fields of medicine, genetics and environment, owing to its advantages of good photophysical properties, excellent biocompatibility and low toxicity to biological systems. Nowadays, it is mainly used in the fields of life sciences such as fluorescent labeling of biological macromolecules, disease diagnosis, immunoassay and DNA detection, all of which lie at the core of this review. First, we briefly introduced the characteristics and principles of the cyanine dye bioprobe. Afterward, we paid attention to the recent progress of cyanine dye bioprobes widely used in the 10 years from 2010 to 2020. The application of cyanine dyes as bioprobes with different identification elements, including enzymes, organelles, immunity and DNAs, was mainly summarized. Finally, this review gave an outlook on the future development trend of cyanine dye bioprobes. This facilitates the construction of a new type of multifunctional fluorescent probe and promotes its clinical application. [ABSTRACT FROM AUTHOR]

Background: Alzheimer’s disease (AD) is a common form of dementia, characterized by production and deposition of β-amyloid peptide in the brain. Thus, β-amyloid peptide is a potentially promising biomarker used to diagnose and monitor the progression of AD. Objective: The study aims to develop a biosensor based on a molecularly imprinted poly-pyrrole for detection of β-amyloid.Material and Methods: In this experimental study, an imprinted poly-pyrrole was employed as an artificial receptor synthesized by electro-polymerization of pyrrole on screen-printed carbon electrodes in the presence of β-amyloid. β-amyloid acts as a molecular template within the polymer. The biosensor was evaluated by cyclic voltammetry using ferro/ferricyanide marker. The parameters influencing the biosensor performance, including electro-polymerization cycle umbers and β-amyloid binding time were optimized to achieve the best biosensor sensitivity. Results: The β-amyloid binding affinity with the biosensor surface was evaluated by the Freundlich isotherm, and Freundlich constant and exponent were obtained as 0.22 ng mL-1 and 10.60, respectively. The biosensor demonstrated a detection limit of 1.2 pg mL-1. The biosensor was applied for β-amyloid determination in artificial cerebrospinal fluid. Conclusion: The biosensor is applicable for early Alzheimer’s disease detection.

A competitive electrochemical aptamer biosensor for the selective detection of Pb2+ was developed in this study. The PAMAM@Au hybrid materials and the bioprobe MB-GNPs-ssDNA were synthesized with chemical methods. Modified electrode with carboxylated graphene oxide was prepared via electrodeposition. PAMAM@Au was immobilized on the modified electrode using the EDC/NHS crosslinker, and aptamer (Apt) was bound to PAMAM@Au hybrid materials using the glutaraldehyde crosslinker. The assembly of MB-GNPs-ssDNA/Apt/PAMAM@Au/GO/SPCE biosensors was achieved through immobilizing bioprobe onto electrodes, based on the theory of aptamer-complementary chain reactions. The fabricated biosensor was characterized through electrochemical experiments, SEM, AFM, TEM, XPS and FTIR. The biosensor's performance was evaluated in a series of Pb2+ aqueous solutions by differential pulse voltammetry (DPV), and the results demonstrated this biosensor had excellent repeatability, stability, and specificity. The detection range spanned from 0.5 pM/L to 500 nM/L, with a detection limit of 5 fM/L. Consequently, the proposed biosensor can serve as a reliable analytical tool for the sensitive detection of lead ions. • A novel competitive electrochemical aptamer biosensor for detecting lead ions was Designed. • The polyamidoamine (PAMAM) dendrimer encapsulated with nanogold was innovatively synthesized. • A biosignal probe MB-GNPs-ssDNA for enhancing the detection signal of biosensor was synthesized. • The redox property of methylene blue was employed to generate a detectable electrical signal. [ABSTRACT FROM AUTHOR]

This study aimed to add two functional components—antibacterial 45S5BGs particles and AIE nanoparticles (TPE-NIM+) with bioprobe characteristics—to the guided tissue regeneration (GTR) membrane, to optimize the performance. The PLGA/BG/TPE-NIM+ membrane was synthesized. The static water contact angle, morphologies, and surface element analysis of the membrane were then characterized. In vitro biocompatibility was tested with MC3T3-E1 cells using CCK-8 assay, and antibacterial property was evaluated with Streptococcus mutans and Porphyromonas gingivalis by the LIVE/DEAD bacterial staining and dilution plating procedure. The fluorescence staining of bacteria was observed by Laser Scanning Confocal Microscope. The results showed that the average water contact angle was 46°. In the cytotoxicity test, except for the positive control group, there was no significant difference among the groups (p > 0.05). The antibacterial effect in the PLGA/BG/TPE-NIM+ group was significantly (p < 0.01), while the sterilization rate was 99.99%, better than that in the PLGA/BG group (98.62%) (p < 0.01). Confocal images showed that the membrane efficiently distinguished G+ bacteria from G− bacteria. This study demonstrated that the PLGA/BG/TPE-NIM+ membrane showed good biocompatibility, efficient sterilization performance, and surface mineralization ability and could be used to detect pathogens in a simple, fast, and wash-free protocol. [ABSTRACT FROM AUTHOR]

Abstract Surface‐enhanced Raman scattering (SERS) technology with feature of high sensitivity, selective enhancement, in situ detection, nondestructive, label free, and fingerprint spectrum has been widely utilized in various practical applications, especially for bioanalysis. Cancer diagnosis and therapy based on SERS bioimaging has been reported as a promising approach in recent decades, and various types of material‐based SERS bioprobes are rapidly designed continuously. SERS bioimaging has been successfully employed in cancer screening, diagnosis, and componential analysis in both in vitro and in vivo cancer tissue samples, which simultaneously provides visual morphology and biochemical information. Precise tumor tissue excision, real‐time monitoring of cellular uptake process, and noninvasive cell tracking and labeling are realized due to the effective Raman image bioprobes, satisfying the requirements of precision medicine. Here, an overview of SERS bioprobes based on noble metals, metal oxides, and composite materials is presented by highlighting their respective, unique advantages and recent achievements in cancer imaging realm. This review also offers a distinctive perspective on designing multifunctional micro–nanoparticles with remarkable SERS activity, and proposing novel strategies for establishing high‐performance sensors and imaging bioprobes derived from the deep insight of enhancement mechanism for different types of SERS substrates.

Surface‐enhanced Raman scattering (SERS) technology with feature of high sensitivity, selective enhancement, in situ detection, nondestructive, label free, and fingerprint spectrum has been widely utilized in various practical applications, especially for bioanalysis. Cancer diagnosis and therapy based on SERS bioimaging has been reported as a promising approach in recent decades, and various types of material‐based SERS bioprobes are rapidly designed continuously. SERS bioimaging has been successfully employed in cancer screening, diagnosis, and componential analysis in both in vitro and in vivo cancer tissue samples, which simultaneously provides visual morphology and biochemical information. Precise tumor tissue excision, real‐time monitoring of cellular uptake process, and noninvasive cell tracking and labeling are realized due to the effective Raman image bioprobes, satisfying the requirements of precision medicine. Here, an overview of SERS bioprobes based on noble metals, metal oxides, and composite materials is presented by highlighting their respective, unique advantages and recent achievements in cancer imaging realm. This review also offers a distinctive perspective on designing multifunctional micro–nanoparticles with remarkable SERS activity, and proposing novel strategies for establishing high‐performance sensors and imaging bioprobes derived from the deep insight of enhancement mechanism for different types of SERS substrates. [ABSTRACT FROM AUTHOR]

This work describes a novel fluorescent 2,1,3-benzothiadiazole derivative designed to act as a water-soluble and selective bioprobe for plasma membrane imaging. The new compound was efficiently synthesized in a two-step procedure with good yields. The photophysical properties were evaluated and the dye proved to have an excellent photostability in several solvents. DFT calculations were found in agreement with the experimental data and helped to understand the stabilizing intramolecular charge-transfer process from the first excited state. The new fluorescent derivative could be applied as selective bioprobe in several cell lines and displayed plasma-membrane affinity during the imaging experiments for all tested models.

That sulfide anions (S2−) in aquatic environments are produced by microorganisms through degrading sulfur-containing proteins and other organics are harmful to human health. Thus, it is of significance to develop a convenient method for the detection of S2− in water. Small molecular fluorescent probes are very popular for their advantages of visualization, real-time, high sensitivity, and convenience. However, low solubility in water limits the application of existing S2− probes. In this work, we found that our previously developed water-soluble glycosylated fluorescent bioprobe Cu[GluC] can achieve detection of S2− in water. Cu[GluC] can restore fluorescence within 20 s when it encounters S2− and shows good sensitivity towards S2− with a detection limit of 49.6 nM. Besides, Cu[GluC] derived fluorescent test strips were obtained by immersion and realized conveniently visual S2− detection in water by coupling with a UV lamp and a smartphone app. This work provides a fluorescent bioprobe with good water solubility as well as its derived fluorescent test strip for sensitive and simple detection of S2− in water, which shows good prospects in on-site water quality monitoring.

Therapeutic nanoparticles are designed to enhance efficacy, real-time monitoring, targeting accuracy, biocompatibility, biodegradability, safety, and the synergy of diagnosis and treatment of diseases by leveraging the unique physicochemical and biological properties of well-developed bio-nanomaterials. Recently, bio-inspired metal nanoclusters (NCs) consisting of several to roughly dozens of atoms (<2 nm) have attracted increasing research interest, owing to their ultrafine size, tunable fluorescent capability, good biocompatibility, variable metallic composition, and extensive surface bio-functionalization. Hybrid core–shell nanostructures that effectively incorporate unique fluorescent inorganic moieties with various biomolecules, such as proteins (enzymes, antigens, and antibodies), DNA, and specific cells, create fluorescently visualized molecular nanoparticle. The resultant nanoparticles possess combinatorial properties and synergistic efficacy, such as simplicity, active bio-responsiveness, improved applicability, and low cost, for combination therapy, such as accurate targeting, bioimaging, and enhanced therapeutic and biocatalytic effects. In contrast to larger nanoparticles, bio-inspired metal NCs allow rapid renal clearance and better pharmacokinetics in biological systems. Notably, advances in nanoscience, interfacial chemistry, and biotechnologies have further spurred researchers to explore bio-inspired metal NCs for therapeutic purposes. The current review presents a comprehensive and timely overview of various metal NCs for various therapeutic applications, with a special emphasis on the design rationale behind the use of biomolecules/cells as the main scaffolds. In the different hybrid platform, we summarize the current challenges and emerging perspectives, which are expected to offer in-depth insight into the rational design of bio-inspired metal NCs for personalized treatment and clinical translation. The current review presents a comprehensive and timely overview of various metal nanoclusters (NCs) for various therapeutic applications, with a special emphasis on the design rationale behind the use of biomolecules/cells as the main scaffolds. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is a common form of dementia, characterized by production and deposition of β-amyloid peptide in the brain. Thus, β-amyloid peptide is a potentially promising biomarker used to diagnose and monitor the progression of AD. Objective: The study aims to develop a biosensor based on a molecularly imprinted poly-pyrrole for detection of β-amyloid. Material and Methods: In this experimental study, an imprinted poly-pyrrole was employed as an artificial receptor synthesized by electro-polymerization of pyrrole on screen-printed carbon electrodes in the presence of β-amyloid. β-amyloid acts as a molecular template within the polymer. The biosensor was evaluated by cyclic voltammetry using ferro/ferricyanide marker. The parameters influencing the biosensor performance, including electro-polymerization cycle umbers and β-amyloid binding time were optimized to achieve the best biosensor sensitivity. Results: The β-amyloid binding affinity with the biosensor surface was evaluated by the Freundlich isotherm, and Freundlich constant and exponent were obtained as 0.22 ng mL-1 and 10.60, respectively. The biosensor demonstrated a detection limit of 1.2 pg mL-1. The biosensor was applied for β-amyloid determination in artificial cerebrospinal fluid. Conclusion: The biosensor is applicable for early Alzheimer's disease detection. [ABSTRACT FROM AUTHOR]

This study aimed to add two functional components—antibacterial 45S5BGs particles and AIE nanoparticles (TPE-NIM+) with bioprobe characteristics—to the guided tissue regeneration (GTR) membrane, to optimize the performance. The PLGA/BG/TPE-NIM+ membrane was synthesized. The static water contact angle, morphologies, and surface element analysis of the membrane were then characterized. In vitro biocompatibility was tested with MC3T3-E1 cells using CCK-8 assay, and antibacterial property was evaluated with Streptococcus mutans and Porphyromonas gingivalis by the LIVE/DEAD bacterial staining and dilution plating procedure. The fluorescence staining of bacteria was observed by Laser Scanning Confocal Microscope. The results showed that the average water contact angle was 46°. In the cytotoxicity test, except for the positive control group, there was no significant difference among the groups (p > 0.05). The antibacterial effect in the PLGA/BG/TPE-NIM+ group was significantly (p < 0.01), while the sterilization rate was 99.99%, better than that in the PLGA/BG group (98.62%) (p < 0.01). Confocal images showed that the membrane efficiently distinguished G+ bacteria from G− bacteria. This study demonstrated that the PLGA/BG/TPE-NIM+ membrane showed good biocompatibility, efficient sterilization performance, and surface mineralization ability and could be used to detect pathogens in a simple, fast, and wash-free protocol.

In this study, positively charged polystyrene-co-poly (ar-vinylbenzyl) trimethylammonium nanoparticles loading with Aggregation Induced Emission (AIE) fluorescent molecule sulfonated 9,10-distyrylanthracene derivatives (SDSA) by coulomb force denoted as SDSA/PS-co-PVBTAC have been prepared. The size, size distribution and morphology of nanoparticles have been tested by Dynamic light scattering (DLS) and Scanning electron microscope (SEM). The synthesized nanoparticles possess uniform size, good monodispersity and low biological toxicity. The AIE-type SDSA/PS-co-PVBTAC showed good fluorescence stability at pH from 3 to 10. It has been proved that the biological macromolecules including Bovine Serum Albumin (BSA), DNA and RNA can amplify the cell imaging signals. Moreover, the AIE-type nanoparticles have been shown to perform fluorescent imaging of various cells. It suggests that the prepared SDSA/PS-co-PVBTAC can be used as a new biological probe in the field of cell imaging and detection, as well as expanding the application of AIE fluorescent molecules in biosensing field. Through Coulomb force of nanoparticles with AIE fluorophore SDSA, hybrid polymeric nanoparticles SDSA/PS-co-PVBTAC for various cells imaging were prepared. It has been proven that the biological macromolecules can amplify the fluorescence signals, accompanied with good fluorescence stability at pH from 3 to 10. The electrostatic attraction between the positively charged nanoparticles and the negatively charged cell membrane is conducive to improve the cellular uptake of nanoparticle, as well as the effect of intracellular imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • 4000 to 7500 cm−1 of raw NIR spectra from C.rupestris was linke to carbohydrate and stretching of the N–H and the O–H overtone associated with proline and MT. • IR spectroscopy technique coupled with PLS quantitative analysis model has the high potential. • PCA analysis indicate that there are clear boundaries in the spatial distribution of Pb2+ concentrations. • R c 2 of chlorophyll, total soluble sugar, proline and MT between measured and predicted value was higher than 0.99. Near-infrared (NIR) spectroscopy was used as a bioprobe to estimation chlorophyll, total sugar, proline, and metallothionein (MT) response to Pb2+ (0, 1, 2.5, 5, 7.5, 10, and 20 mg/l) in Cladophora rupestris. Spectra between 3775.94 and 12315.19 cm−1 were analysed using a partial least-squares regression (PLS). Principal component analysis (PCA) was performed by evaluating the distance between the C. rupestris samples treated with different concentrations of Pb2+. Results showed that 4000–7500 cm−1 of raw NIR spectra from C. rupestris was linked to carbohydrates and stretching of N–H, and the O–H overtone was associated with proline and MT. NIR spectroscopy technique coupled with PLS quantitative analysis model has high potential. Multiplicative scatter correction and standard normal variate combining first-order derivative with S-G smoothing filter are superior to the other models. The root mean square error of cross of chlorophyll, total sugar, proline, and MT was 0–1, indicating the accuracy of the model is high. The R c 2 values of chlorophyll, total soluble sugar, proline, and MT between measured and predicted values were higher than 0.99. PCA analysis indicate clear boundaries in the spatial distributions of seven Pb2+ concentrations, indicating that NIR spectroscopy has high potential as a tool assisting bioprobes for estimating metabolites' responses to Pb2+ in Cladophora rupestris. [ABSTRACT FROM AUTHOR]

Arginine is an important amino acid in humankind bodies and is of essential clinical significance. This paper presents a novel bioprobe based on fluorescence resonance energy transfer (FRET), which can be used to detect arginine efficiently and economically. In this bioprobe system, positively charged up-conversion phosphor NaYF 4 (NYF) acts as energy donor, and negatively charged gold nanoparticle (AuNP) acts as energy acceptor. The oppositely charged donor and acceptor come into close proximity through electrostatic attraction effect, which results in the occurrence of FRET between NYF and AuNP. The FRET process is thus in the "on" state, meanwhile the system is in the "off" state, and the emitting light of NYF quenched. When positively charged arginine is added into the system, the guanidyl of arginine binds to AuNP and leads to the negatively charged AuNP becomes positively charged one, and the AuNP separates from NYF because of the electrostatic repulsion. The FRET process is blocked and the system switches to the "on" state because the distance between NYF and AuNP becomes longer. In the "on" state, the intensity of the restored emitting light is proportional to the concentration of arginine. This approach brings a good linear relationship between the fluorescence intensity and the concentration of arginine in the concentration range of 14.42–115.04 μM. The limit of detection is as low as 2.9 μM. A new method for quantitative determination of arginine by just measuring the fluorescence intensity of the system is established. Image 1 • This work presents a novel up-conversion FRET sensor for detection of arginine. • Positively charged donor and negatively charged acceptor attract each other. • The donor and receptor become into FRET proximity through electrostatic attraction effect. • The linear response range is 14.42–115.04 μM. [ABSTRACT FROM AUTHOR]

Abstract In this work, we have developed an efficient method based on silica fluorescent dye-doped nanoparticles and second antibody for cancer cell labeling. The dye-doped silica nanoparticles were synthesized by the reverse microemulsion method with the conjugate of 3-aminopropyltriethoxysilane and rhodamine B isothiocynate. A PEG with flexible long chain as the bridge was introduced onto the surface of the nanoparticle via cyanogens bromide method. The second antibody, goat anti-rabbit IgG, was conjugated on the surface of the PEG-terminal modified silica fluorescent nanoparticles by covalent binding to the PEG linkers via the EDC/sulfo-NHS method. The concentrations of goat anti-rabbit IgG covering the nanoparticles were quantified via the Bradford method. The silica fluorescent nanoparticles functionalized with rabbit anti-MUC1 antibody were employed as bioprobes for the recognition of MUC1 protein in human breast carcinoma molecules MCF-7 cells. Compared with fluorescent dye labeled IgG, the fluorescent nanoprobes display dramatically increased photostability. Highlights • A new method to prepare luminescent and photostable probe for bioimaging was report. [ABSTRACT FROM AUTHOR]

The development of lanthanide-based luminescent probes with a long emission lifetime has the potential to revolutionize imaging-based diagnostic techniques. By a rational design strategy taking advantage of computational predictions, a novel, water-soluble Eu3+ complex from a cyclen-based ligand bearing 1,3-disubstituted benzo[h]isoquinoline arms was realized. The ligand has been obtained overcoming the lack of reactivity of position 3 of the isoquinoline moiety. Notably, steric hindrance of the heteroaromatic chromophore allowed selective and stoichiometry-controlled insertion of two or three antennas on the cyclen platform without any protection strategy. The complex bears a fourth heptanoic arm for easy conjugation to biomolecules. This new chromophore allowed the sensitization of the metal center either with one or two photons excitation. The suitability as a luminescent bioprobe was validated by imaging BMI1 oncomarker in lung carcinoma cells following an established immunofluorescence approach. The use of a conventional epifluorescence microscope equipped with a linear structured illumination module disclosed a simple and inexpensive way to image confocally Ln-bioprobes by single photon excitation in the 350–400 nm window, where ordinary confocal systems have no excitation sources.

The food-borne diseases triggered by Escherichia coli O157: H7 (E. coli O157: H7) have become a life-threatening problem for tens of thousands of people around the world in the past few decades. Therefore, a rapid, simple, and user-friendly biosensing label to monitor E. coli O157: H7 has become necessary and important. In this work, carboxyl functionalized graphene quantum dots (cf-GQDs) as fluorescent labels for optical imaging and sensing in E. coli O157: H7 have been firstly proposed and evaluated. E. coli O157: H7 antibody is successfully covalently conjugated to water-soluble cf-GQDs via a cross-linking reaction, and then cf-GQDs immunofluorescence probe is achieved. The probe can effectively recognize E. coli O157: H7 and generate strong fluorescent signal. The experimental result shows that the blocking agent can obviously improve the specificity of the bioprobe for E. coli O157: H7 with the minimum detection limit of 100 cfu/mL. This novel detection method could be as a useful tool to detect E. coli O157: H7 in food, water, and environment. [ABSTRACT FROM AUTHOR]

Reciprocal signaling between stromal and tumor cells was believed to contribute to tumor cell proliferation and apoptosis in heterocellular systems. Herein we used the CO 2 -sensitive AIEgen as bioprobe to study the synergistic effect of stromal cells and tumor cells in a heterocellular system. The experimental results demonstrated that metabolic rates of living tumor cells in the co-culture system were still faster than that of stromal cell through the detection of CO 2 generation rate in living cell. All rates were, however, slower than that in homocellular system. It indicated that tumor cells would induce neighboring stromal cells to establish a common protection mechanism against foreign material invasion, which enhanced the cell activity and drug resistance. In addition, tumor cells in solid carcinoma exhibited delayed growth but less apoptosis in co-culture systems. Taken these results together, a bidirectional signaling pathway theory was proposed between tumor and stromal cells in co-culture system and could play a different and important role in anticancer drug molecules designs. [ABSTRACT FROM AUTHOR]

In this report, fluorescence detection coupled capillary electrophoresis (CE-FL) was used to detect Protein A. Antibody was first labeled with Cy5 and then mixed with quantum dots (QDs) to form QDs-antibody bioprobe. Further, we observed fluorescence resonance energy transfer (FRET) from QDs donor to Cy5 acceptor. The bioprobe was formed and brought QDs and Cy5 close enough to allow FRET to occur. After adding protein A, the FRET system was broken and caused the FRET signal to decrease. Thus, a new method for the determination of protein A was proposed based on the FRET signal changes. This study provides a new trail of thought for the detection of protein.

Ultrasensitive, rapid and selective diagnostic probes are urgently needed to overcome the limitations of traditional probes for norovirus (NV). Here, we report the detection of NV genogroup II via nucleic acid hybridization technology using a quantum dot (QD)-conjugated molecular beacon (MB) probe. To boost the sensitivity of the MB assay system, an ultrasensitive QD fluorophore with unique optical properties was synthesized, characterized and exploited as a fluorescence signal generator. Alloyed thioglycolic (TGA)-capped CdZnSeS QDs with a high photoluminescence (PL) quantum yield (QY) value of 92% were synthesized, and a modified silanization method was employed to encapsulate the thiol-capped QDs in a silica layer. The resulting highly luminescent alloyed SiO 2 -coated CdZnSeS QDs had a remarkable PL QY value of 98%. Transmission electron microscopy and dynamic light scattering confirmed the monodispersity of the alloyed nanocrystals, and zeta potential analysis confirmed their colloidal stability. Powder X-ray diffraction and PL lifetime measurements confirmed the surface modification of the QDs. The alloyed TGA-capped and SiO 2 -coated CdZnSeS QD-conjugated MB bioprobes detected extremely low concentrations of NV RNA. Ultrasensitive detection of low concentrations of NV RNA with a limit of detection (LOD) of 8.2 copies/mL in human serum and a LOD of 9.3 copies/mL in buffer was achieved using the SiO 2 -coated CdZnSeS QD-MB probes, an increase in sensitivity of 3-fold compared with the detection limit for NV RNA using TGA-capped CdZnSeS QD-MBs. The additional merits of our detection system are rapidity, specificity and improved sensitivity over conventional molecular test probes. [ABSTRACT FROM AUTHOR]

Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the 1980s, but it is only in the past decade that their use as a glucose sensor has increased significantly. These analogues were developed for monitoring glucose uptake in blood cells, but their recent applications include tracking glucose uptake by tumor cells and imaging brain cell metabolism. This review outlines the development of fluorescent-tagged glucose analogues, describes their recent structural modifications and discusses their increasingly diverse biological applications.

Conventional techniques used to diagnose influenza virus face several challenges, such as low sensitivity, slow detection, false positive results and misinterpreted data. Hence, diagnostic probes that can offer robust detection qualities, such as high sensitivity, rapid detection, elimination of false positive data, and specificity for influenza virus, are urgently needed. The near-infrared (NIR) range is an attractive spectral window due to low photon absorption by biological tissues, hence well-constructed fluorescent biosensors that emit within the NIR window can offer an improved limit of detection (LOD). Here, we demonstrate the use of a newly synthesized NIR quinternary alloyed CdZnSeTeS quantum dots (QDs) as an ultrasensitive fluorescence reporter in a conjugated molecular beacon (MB) assay to detect extremely low concentrations of influenza virus H1N1 RNA. Under optimum conditions, two different strains of influenza virus H1N1 RNA were detected based on fluorescence enhancement signal transduction. We successfully discriminated between two different strains of influenza virus H1N1 RNA based on the number of complementary nucleotide base pairs of the MB to the target RNA sequence. The merits of our bioprobe system are rapid detection, high sensitivity (detects H1N1 viral RNA down to 2 copies/mL), specificity and versatility (detects H1N1 viral RNA in human serum). For comparison, a conventional CdSe/ZnS-MB probe could not detect the extremely low concentrations of H1N1 viral RNA detected by our NIR alloyed CdZnSeTeS-MB probe. Our bioprobe detection system produced a LOD as low as ~1 copy/mL and is more sensitive than conventional molecular tests and rapid influenza detection tests (RIDTS) probes. [ABSTRACT FROM AUTHOR]

Phenotype-based chemical screening is an attractive strategy for the identification of bioactive compounds. We searched for a compound that induces cellular morphological change and identified a novel compound that we named seco-clavilactone B (Seco- CB). Treatment with Seco- CB decreased the ratio of filament actin (F-actin) to globular actin (G-actin). An in vitro actin polymerization assay revealed that Seco- CB inhibited actin polymerization directly. Further analysis demonstrated that the inhibitory effect of Seco- CB on actin polymerization was associated with Seco- CB binding to either Thr5 or Cys285 of actin. These data indicate that Seco- CB is a novel actin polymerization inhibitor. [ABSTRACT FROM AUTHOR]

Given the significant impact of ions on environment pollution and human health, it is urgently needed to establish effective and convenient ion detection approaches, particularly in living cells. In this paper, we constructed multicolor N-doped-carbon dots (mPD-CDs) by facile one-step hydrothermal carbonization of m-phenylenediamine (mPD). mPD-CDs were successfully deployed for multicolor cellular imaging for animal cells, fungi, and bacteria in a wash-free way with high photostability and satisfactory biocompability. Moreover, mPD-CDs can be used as a fluorescent sensing probe for ultrasensitive detection of both iodide ion (I−) and typical heavy metals such as cadmium (Cd2+), copper (Cu2+), mercury (Hg2+), gadolinium (Gd3+), ferrous ion (Fe2+), Zinc (Zn2+), and ferric ion (Fe3+). This is the first report using CDs as optical sensing probe for the detection of Gd3+, and for detection of Fe3+ with fluorescence "turn on". More significantly, with these versatile and fascinating properties, we applied mPD-CDs for intracellular ion detection in living cells like Hep G2 and S. cerevisiae, and zebra fish. Altogether, mPD-CDs displayed great potential for multicolor cell imaging and the multiple ion detection in vitro and in vivo, presenting a promising strategy for in-situ ultrasensitive sensing of multiple metal ions in the environment and the biological systems. [ABSTRACT FROM AUTHOR]

We describe a novel fluorescent bioprobe for the sensitive and selective detection of double-stranded DNA (dsDNA). It consists of quantum dots (Q-dots) whose fluorescence is quenched (through photoinduced electron transfer) on covering them with the Al(III)-pefloxacin complex. It is found, however, that dsDNA has an affinity for this complex that is so strong that it can break up the binding to the quantum dots, this leading to a complete recovery of the fluorescence of both the Q-dots and the Al(III)-pefloxacin complex. Dual fluorescence (peaking at 420 and 547 nm) is observed under a single excitation wavelength of 350 nm. Neither ribonucleic acid, bovine serum albumin, nor biologically relevant metal ions are capable of giving this effect. The detection limit (3σ/k) for herring sperm DNA is 15.3 μg L if determined via the fluorescence of the Q-dots, and 48 μg L via the Al(III)-pefloxacin complex. The method was applied to the determination of hsDNA in synthetic samples and gave excellent results. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper reviews our recent works on the functionalized nanoparticles. [•] The applications of the nanoparticles to biomaterials are illustrated. [•] Synthetic protocols for the typical products are briefly presented. [ABSTRACT FROM AUTHOR]

The results of quantum dot (QD) probe preparation for multiplexed single-cell array staining and analysis are reported. By controlling the reaction temperature, time, and ratio of Cd to Se, multicolor CdSe QDs emitting fluorescence ranging from purple to red in a safer, simpler, and more convenient way than traditional methods is obtained. To detect cells using these oil-soluble QDs, they are first coated with water-soluble thioglycolic aid (TGA) so that biocompatible multiwavelength bioprobes can be obtained. QDs' surface is somewhat damaged when binding TGA to QDs is found, which results in a reduction of QDs' emission wavelength and a slight blue shift of QDs' emission wavelength after water-soluble modification with TGA. Comparison of the emission spectrum showed that it is negligible, and the fluorescent properties of QDs capped by TGA are still satisfactory. Living cells are then stained with multiplexed probes by conjugating TGA-QDs with antibodies specific to these cell antigens. Changes in fluorescence intensity can indicate change in the relative quantity of antigens expressed in the same cell caused by external stimulus, offering effective methods to multiplexed optical analysis of single cells. [ABSTRACT FROM AUTHOR]

We report here a simple quantum dot-FRET (QD-FRET) bioprobe based on fluorescence resonance energy transfer (FRET) for the sensitive and specific detection of hepatitis B virus DNA (HBV DNA). The proposed one-pot HBV DNA detection method is very simple, rapid and convenient due to the elimination of the washing and separation steps. In this study, the water-soluble CdSe/ZnS QDs were prepared by replacing the trioctylphosphine oxide on the surface of QDs with mercaptoacetic acid (MAA). Subsequently, DNA was attached to QDs surface to form the functional QD-DNA bioconjugates by simple surface ligand exchange. After adding 6-carboxy-X-rhodamine (ROX)-modified HBV DNA (ROX-DNA) into the QD-DNA bioconjugates solution, DNA hybridization between QD-DNA bioconjugates and ROX-DNA was formed. The resulting hybridization brought the ROX fluorophore, the acceptor, and the QDs, the donor, into proximity, leading to energy transfer from QDs to ROX. When ROX-DNA was displaced by the unlabeled HBV DNA, the efficiency of FRET was dramatically decreased. Based on the changes of both fluorescence intensities of QDs and ROX, HBV DNA could be detected with high sensitivity and specificity. Under the optimized conditions, the linear range of HBV DNA determination was 2.5 - 30 nmol L, with a correlation coefficient (R) of 0.9929 and a limit of detection (3σ black) of 1.5 nmol L. The relative standard deviation (R.S.D.) for 12 nmol L HBV DNA was 0.9 % ( n = 5). There was no interference to non-complementary DNA. Time-resolved fluorescence spectra and fluorescence images were performed to verify the validity of this method and the results were satisfying. [ABSTRACT FROM AUTHOR]

Application of nano-particles to diagnostic fields has attracted much attention. Biotechnology can contribute to produce useful nano-materials by engineering bacteriophage nano-particles, which are easily prepared by infecting phages to bacterial host cells. In this study, establishment of nano-bioprobes was demonstrated, based on the T7 phage display system, by constructing phage particles displaying a ligand polypeptide S-tag and a green fluorescent protein (GFP) at the same time on the surface of phage head. To achieve this purpose, two types of phage particles were tested: One displayed S-tag and GFP as a single polypeptide (tandem display), and another displayed these molecules as two different polypeptides (parallel display). Only the parallelly displayed phage could be detected with ligand blotting using S-protein and with immunoblotting using an anti-GFP antibody. S-protein-coated magnetic beads and nano-particles were successively labeled with fluorescence using the parallelly displayed phage but could not be labeled with the tandemly displayed phage. Thus, the parallel display of a ligand molecule and fluorescent protein on the head surface of bacteriophage T7 could provide a new scheme of producing fluorescent nano-bioprobes for diagnostic applications. [ABSTRACT FROM AUTHOR]

That sulfide anions (S 2- ) in aquatic environments are produced by microorganisms through degrading sulfur-containing proteins and other organics are harmful to human health. Thus, it is of significance to develop a convenient method for the detection of S 2- in water. Small molecular fluorescent probes are very popular for their advantages of visualization, real-time, high sensitivity, and convenience. However, low solubility in water limits the application of existing S 2- probes. In this work, we found that our previously developed water-soluble glycosylated fluorescent bioprobe Cu[GluC] can achieve detection of S 2- in water. Cu[GluC] can restore fluorescence within 20 s when it encounters S 2- and shows good sensitivity towards S 2- with a detection limit of 49.6 nM. Besides, Cu[GluC] derived fluorescent test strips were obtained by immersion and realized conveniently visual S 2- detection in water by coupling with a UV lamp and a smartphone app. This work provides a fluorescent bioprobe with good water solubility as well as its derived fluorescent test strip for sensitive and simple detection of S 2- in water, which shows good prospects in on-site water quality monitoring.

Urea (CH6ON2) is one of the main human nitrogen-based metabolic wastes. The concentration of urea in blood lies between 2.5-7 mM for healthy individuals, and is commonly used as an indicator for several diseases that may alter this value. Spectrophotometric methods are employed for the determination of blood urea concentration during clinical assays. Although these methods are sensitive, they make use of toxic reagents and complex reaction schemes. Therefore, in this research we present the bioelectrochemical determination of urea by the use of the protein urease (E.C.3.1.1.5) along with a nano-platinized boron-doped diamond electrode. This approach has been proven to be efficient and sensitive providing a platform with detection limits of 1.79 mM ( S/ N=3). The linear range resulted from 1 mM to 25 mM for the determination of urea, and response time of five minutes. [ABSTRACT FROM AUTHOR]

Abstract: A general approach for the preparation of a library consisting of reactive rhodamine B (RhB) bioprobes based on ester or thioester linkages is described. The synthesis of this library proceeds fast and efficiently in one reaction step. Pure RhB ester chromophores are readily obtained directly from the reaction mixture following a simple and straight forward workup procedure without further HPLC purification required. A variety of functional groups are attached to the RhB scaffold yielding the functional chromophores in moderate to high yields with particular focus on introducing bioorthogonal substituents suitable for protein and peptide labeling. The approach reported herein provides a concise and practical route to access a variety of reactive RhB fluorophores that could be applied for various bioconjugation chemistries. [Copyright &y& Elsevier]

Abstract: Progress in biomedical imaging depends on the development of bioprobes with a high sensitivity and stability. Fluorescent silica nanoparticles (NPs) covalent conjugation of avidin has been proposed for cancer cells imaging by fluorescence microscopy. Uniform silica NPs were prepared using water-in-oil (W/O) microemulsion methods and primary amine groups were introduced onto the surface of the NPs by condensation of tetraethyl orthosilicate (TEOS). Optically stable organic dyes, tris(2,2''-bipyridyl) dichlororuthenium(II) hexahydrate (Rubpy), were doped inside the silica NPs. The amine functions were transferred to carboxyl groups coupled with a linker elongation. Avidin was immobilized at the surface of the NPs by covalent binding to the carboxyl linkers. The binding capacity of the avidin-covered NPs for ligand biotin was quantified by titration with biotin(5-fluorescein) conjugate to 1.25 biotin binding sites/100nm2. We used biotinylated antibody and cell recognition by fluorescence microscopy imaging technique. The lung carcinoma cells were identified easily with high efficiency using these antibody-coated NPs. By comparison with fluorescein isothiocyanate (FITC), dye-doped silica NPs display dramatically increased stability of fluorescence as well as photostability, as compared to the common organic dye, when under continuous irradiation. [Copyright &y& Elsevier]

Multifunctional nanostructures containing magnetite and gold have warranted interest due to their significant applications in biotechnology and medical diagnosis. In the present study, Au-nanorod@FeO core-shell nanocomposites are synthesized by the decomposition of Fe(acac) onto Au-nanorods (GNRs) through a solvothermal reaction using octylamine as a reductive reagent. The reaction conditions, including temperature, concentration, and molar ratio of Fe and Au elements, are investigated to obtain the desired nanocomposites. The sizes of nanocomposites are observed to be 30-50 nm in length and ca. 20 nm in diameter for GNR cores, and ca. 5 nm in thickness for FeO shells. The compositions are investigated by X-ray photoelectron spectroscopy instrument. The surface-enhanced Raman scattering (SERS) of the sample is studied using 4-aminothiophenol as an imitational object. The magnetic property is characterized by a quantum magnetometer at 300 K. Folic acid is connected on the surface of GNR@FeO nanocomposite through surface modification to form a probe nanostructure for cancer cells. The nanocomposites could be used to separate HeLa cells from the culture medium by an external magnetic field, and further shows a pronounced SERS effect in the detection of HeLa cells. [ABSTRACT FROM AUTHOR]

Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the 1980s, but it is only in the past decade that their use as a glucose sensor has increased significantly. These analogues were developed for monitoring glucose uptake in blood cells, but their recent applications include tracking glucose uptake by tumor cells and imaging brain cell metabolism. This review outlines the development of fluorescent-tagged glucose analogues, describes their recent structural modifications and discusses their increasingly diverse biological applications. [ABSTRACT FROM AUTHOR]