Gold Nanoparticle-Quantum Dot Fluorescent Nanohybrid: Application for Localized Surface Plasmon Resonance-induced Molecular Beacon Ultrasensitive DNA Detection

Stimulation the immune response through ξ potential on core-shell 'calcium oxide/magnetite iron oxides' nanoparticles

This study investigated the role of ξ Potential on Monometallic (MM) and Bimetallic (BM) Calcium Oxide/Magnetite Iron Oxides nanoparticles to stimulate the immune response. Metallic nanoparticles (MNPs) were biosynthesis using Pseudomonas fluorescens S48. MNPs characterization was carried out by UV-Vis spectra, XRD analysis, Zeta potential and Particles size, SEM-EDS, and TEM, and the concentrations were calculated by ICP-AES. The immune system activity was measured by estimation of lymphocytes transformation, phagocytic activity. The end point was in evaluating the toxicity of Metallic NPs by comet assay. SEM-EDS and TEM micrographs showed that MM CaO and Fe3O4 represent a perfect example of zero-dimensional (0-D) NPs with cubic and spherical particles in shape, while BM CaO/Fe3O4 NPs appeared in the form of Core-shell structure. The variations effect of novelty MM, BM CaO/Fe3O4 NPs in enhancing immune activity were based on the ξ Potential whereas negatively and positively charged. These findings demonstrate that the cationic CaO/Fe3O4 NPs are inefficient in stimulating the immune system which causes a high cytotoxic effect. But the anionic CaO/Fe3O4 NPs have advantages in targeting the immune system because of enhanced delivery to the cells through adsorptive endocytosis as well as the half-life clearance from the blood.

An achromatic colorimetric nanosensor for sensitive multiple pathogen detection by coupling plasmonic nanoparticles with magnetic separation

Rapid screening of multiple pathogens will greatly improve the efficiency of pandemic prevention and control. Colorimetric methods exhibit the advantages of convenience, portability, low cost, time efficiency, and free of sophisticated instruments, yet usually have difficulties in simultaneous detection and suffer from monotonous color changes with low visual resolution and sensitivity. Hence, coupled three kinds of plasmonic nanoparticles (NPs) with magnetic separation, we developed an achromatic colorimetric nanosensor with highly enhanced visual resolution for simultaneous detection of SARS-CoV-2, Staphylococcus aureus, and Salmonella typhimurium. The achromatic nanosensor was composed of SARS-CoV-2-targeting red gold NPs, S. aureus-targeting yellow silver NPs and S. typhimurium-targeting blue silver triangle NPs mixed as black color. In the detection, three corresponding magnetic probes were added into the above mixture. In the presence of a target pathogen, it would be recognized and combined with corresponding colored reporters and magnetic probes to form sandwich complexes, which were removed by magnetic separation, and the sensor changed from black to a chromatic color (the color of the reporters remained in supernatant). Consequently, different target pathogen induced different color. For example, SARS-CoV-2, S. aureus, and S. typhimurium respectively produced green, purple, and orange. While coexistence of S. aureus and S. typhimurium produced red, and coexistence of S. aureus and SARS-CoV-2 produced blue, etc. Therefore, by observing the color change or measuring the absorption spectra, multiple pathogen detection was achieved conveniently. Compared with most colorimetric sensors, this achromatic nanosensor involved rich color change, thus significantly enhancing visual resolution and inspection sensitivity. Therefore, this sensor opened a promising avenue for efficient monitoring and early warning of food safety and quality.

Determination of the Highly Sensitive Carboxyl-Graphene Oxide-Based Planar Optical Waveguide Localized Surface Plasmon Resonance Biosensor

This study develops a highly sensitive and low-cost carboxyl-graphene-oxide-based planar optical waveguide localized surface plasmon resonance biosensor (GO-OW LSPR biosensor), a system based on measuring light intensity changes. The structure of the sensing chip comprises an optical waveguide (OW)-slide glass and microfluidic-poly (methyl methacrylate) (PMMA) substrate, and the OW-slide glass surface-modified gold nanoparticle (AuNP) combined with graphene oxide (GO). As the GO has an abundant carboxyl group (–COOH), the number of capture molecules can be increased. The refractive index sensing system uses silver-coated reflective film to compare the refractive index sensitivity of the GO-OW LSPR biosensor to increase the refractive index sensitivity. The result shows that the signal variation of the system with the silver-coated reflective film is 1.57 times that of the system without the silver-coated reflective film. The refractive index sensitivity is 5.48 RIU⁻¹ and the sensor resolution is 2.52 ± 0.23 × 10⁻⁶ RIU. The biochemical sensing experiment performs immunoglobulin G (IgG) and streptavidin detection. The limits of detection of the sensor for IgG and streptavidin are calculated to be 23.41 ± 1.54 pg/mL and 5.18 ± 0.50 pg/mL, respectively. The coefficient of variation (CV) of the repeatability experiment (sample numbers = 3) is smaller than 10.6%. In addition, the affinity constants of the sensor for anti-IgG/IgG and biotin/streptavidin are estimated to be 1.06 × 10⁷ M⁻¹ and 7.30 × 10⁹ M⁻¹, respectively. The result shows that the GO-OW LSPR biosensor has good repeatability and very low detection sensitivity. It can be used for detecting low concentrations or small biomolecules in the future.

Photoluminescence Properties of CdSe/ZnS Quantum Dot Donor-Acceptor via Plasmon Coupling of Metal Nanostructures and Application on Photovoltaic Devices

Hybrid nanostructures composed of quantum dots (QDs) and metal nanoparticles (MNS) have gained immense research interest because of their unique optical properties. In optoelectronic applications, quenching and enhancement in QD photoluminescence (PL) are critical parameters. Herein, gold nanoparticles coating a silica layer decorated with quantum dots (AuNPs@SiO₂@QDs) are prepared with diverse SiO₂ thickness and QD diameter for investigating the exciton-plasmon interaction. This reveals the charge interaction between QDs and AuNPs@SiO₂ resulting from different impacts of the Föster energy-transfer process and plasmon resonance enhancement. The variation in both radiative and nonradiative energy-transfer processes in CdSe/ZnS QDs donor-acceptor pairs clarifies the impact of AuNPs@SiO₂. In addition, the hybrid structures are plainly incorporated with silicon solar cells, which activated the improvement in the power conversion efficiency (PCE). With the significant tunability of the PL intensity in the visible and near-infrared regions, this hybrid nanostructure provides potential strategies for developing efficient optoelectronics via facile methods.

Biosensors for the Determination of SARS-CoV-2 Virus and Diagnosis of COVID-19 Infection

Monitoring and tracking infection is required in order to reduce the spread of the coronavirus disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To achieve this goal, the development and deployment of quick, accurate, and sensitive diagnostic methods are necessary. The determination of the SARS-CoV-2 virus is performed by biosensing devices, which vary according to detection methods and the biomarkers which are inducing/providing an analytical signal. RNA hybridisation, antigen-antibody affinity interaction, and a variety of other biological reactions are commonly used to generate analytical signals that can be precisely detected using electrochemical, electrochemiluminescence, optical, and other methodologies and transducers. Electrochemical biosensors, in particular, correspond to the current trend of bioanalytical process acceleration and simplification. Immunosensors are based on the determination of antigen-antibody interaction, which on some occasions can be determined in a label-free mode with sufficient sensitivity.

Development of a long noncoding RNA BC032469-dependent gold nanoparticle molecular beacon for the detection of gastric cancer cells

Aim: Long noncoding RNA (lncRNA) BC032469-dependent gold nanoparticle molecular beacons (AuNP-MB) were constructed for the detection of gastric cancer cells. Materials & methods: The AuNP-MBs were prepared according to well-established procedures based on the Au-S interaction between the gold lattice and thiol functionalized oligonucleotides. More importantly, the stability and targeting ability of AuNP-MB were verified by a series of in vitro and in vivo experiments. Results: The lncRNA-dependent probes were successfully utilized for AuNP-MB-based intracellular imaging, with fluorescence effectively emitted in GC cells, but not in normal cells. Notably, such fluorescent emission was positively correlated with lncRNA BC032469 expression. Conclusion: The authors developed an effective fluorescent imaging probe for the recognition of gastric cancer cells.

Plasmonic Biosensors for Single-Molecule Biomedical Analysis

The rapid spread of epidemic diseases (i.e., coronavirus disease 2019 (COVID-19)) has contributed to focus global attention on the diagnosis of medical conditions by ultrasensitive detection methods. To overcome this challenge, increasing efforts have been driven towards the development of single-molecule analytical platforms. In this context, recent progress in plasmonic biosensing has enabled the design of novel detection strategies capable of targeting individual molecules while evaluating their binding affinity and biological interactions. This review compiles the latest advances in plasmonic technologies for monitoring clinically relevant biomarkers at the single-molecule level. Functional applications are discussed according to plasmonic sensing modes based on either nanoapertures or nanoparticle approaches. A special focus was devoted to new analytical developments involving a wide variety of analytes (e.g., proteins, living cells, nucleic acids and viruses). The utility of plasmonic-based single-molecule analysis for personalized medicine, considering technological limitations and future prospects, is also overviewed.

Novel nucleic acid origami structures and conventional molecular beacon-based platforms: a comparison in biosensing applications

Nucleic acid nanotechnology designs and develops synthetic nucleic acid strands to fabricate nanosized functional systems. Structural properties and the conformational polymorphism of nucleic acid sequences are inherent characteristics that make nucleic acid nanostructures attractive systems in biosensing. This review critically discusses recent advances in biosensing derived from molecular beacon and DNA origami structures. Molecular beacons belong to a conventional class of nucleic acid structures used in biosensing, whereas DNA origami nanostructures are fabricated by fully exploiting possibilities offered by nucleic acid nanotechnology. We present nucleic acid scaffolds divided into conventional hairpin molecular beacons and DNA origami, and discuss some relevant examples by focusing on peculiar aspects exploited in biosensing applications. We also critically evaluate analytical uses of the synthetic nucleic acid structures in biosensing to point out similarities and differences between traditional hairpin nucleic acid sequences and DNA origami.

Affinity Sensors for the Diagnosis of COVID-19

The coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was proclaimed a global pandemic in March 2020. Reducing the dissemination rate, in particular by tracking the infected people and their contacts, is the main instrument against infection spreading. Therefore, the creation and implementation of fast, reliable and responsive methods suitable for the diagnosis of COVID-19 are required. These needs can be fulfilled using affinity sensors, which differ in applied detection methods and markers that are generating analytical signals. Recently, nucleic acid hybridization, antigen-antibody interaction, and change of reactive oxygen species (ROS) level are mostly used for the generation of analytical signals, which can be accurately measured by electrochemical, optical, surface plasmon resonance, field-effect transistors, and some other methods and transducers. Electrochemical biosensors are the most consistent with the general trend towards, acceleration, and simplification of the bioanalytical process. These biosensors mostly are based on the determination of antigen-antibody interaction and are robust, sensitive, accurate, and sometimes enable label-free detection of an analyte. Along with the specification of biosensors, we also provide a brief overview of generally used testing techniques, and the description of the structure, life cycle and immune host response to SARS-CoV-2, and some deeper details of analytical signal detection principles.

Light-triggered Janus nanomotor for targeting and photothermal lysis of pathogenic bacteria

The rapid photothermal lysis of Escherichia coli O157:H7 treated with light-triggered Janus nanomotors was visualized by Hilbert differential contrast transmission electron microscopy (HDC-TEM). The extraordinary advantage of this high-resolution microscopic technique was that it revealed the detailed ultrastructure alterations of the treated cells at a state close to their native one. The micrographs demonstrated that Janus nanomotors (mesoporous silica nanoparticles with gold hemisphere and half-capped with cysteamine) were able to target and bind to the pathogenic E. coli. The biorecognition reaction proceeded at slightly acid pH thankful to the formed electrostatic adhesion between positively charged amino groups on nanoparticles surface and the negatively charged cell envelope. The exposure of labeled cells to near infrared laser irradiation leaded to occurrence of effective photothermal damage of their plasma membranes, which was enough strong to lyse bacteria. It was because of the overheating obtained by the photon-to-thermal conversion reaction generated by the surface plasmon resonance response of Janus nanomotors. The good efficiency of photothermal lysis to inactivate E. coli O157:H7 was confirmed by staining with LIVE/DEAD viability kit and quantification of the few survived cells in epifluorescence microscope. Furthermore, HDC-TEM images of ice-embedded inhibited bacteria documented the labeling, membrane disruptions and lysis due to the designed operation of Janus nanomotors. The reported microscopic technique provides a novel strategy for developing of Janus nanomachines as promising platform for nondrug treatment and defeating of antibiotic-resistant pathogenic microorganisms.

Recent Progress in Plasmonic Biosensing Schemes for Virus Detection

The global burden of coronavirus disease 2019 (COVID-19) to public health and global economy has stressed the need for rapid and simple diagnostic methods. From this perspective, plasmonic-based biosensing can manage the threat of infectious diseases by providing timely virus monitoring. In recent years, many plasmonics’ platforms have embraced the challenge of offering on-site strategies to complement traditional diagnostic methods relying on the polymerase chain reaction (PCR) and enzyme-linked immunosorbent assays (ELISA). This review compiled recent progress on the development of novel plasmonic sensing schemes for the effective control of virus-related diseases. A special focus was set on the utilization of plasmonic nanostructures in combination with other detection formats involving colorimetric, fluorescence, luminescence, or Raman scattering enhancement. The quantification of different viruses (e.g., hepatitis virus, influenza virus, norovirus, dengue virus, Ebola virus, Zika virus) with particular attention to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was reviewed from the perspective of the biomarker and the biological receptor immobilized on the sensor chip. Technological limitations including selectivity, stability, and monitoring in biological matrices were also reviewed for different plasmonic-sensing approaches.

Fluorescence signal amplification assay for the detection of B. melitensis 16M, based on peptide-mediated magnetic separation technology and a AuNP-mediated bio-barcode assembled by quantum dot technology

Members of the Brucella spp. are facultative intracellular bacteria that can cause global brucellosis, a zoonotic disease. Herein, a novel fluorescence signal amplification (FSA) method for the rapid detection of B. melitensis 16M was developed based on peptide-mediated magnetic separation (PMS) technology and Au nanoparticle (AuNP)-mediated bio-barcode assay technology assembled by quantum dots (QDs). The PMS technology was used to specifically capture and isolate B. melitensis 16M from food. The immunomagnetic bead-B. melitensis 16M bioconjugates (IMBs-B. melitensis 16M) were then identified by IgY on the surface of AuNPs and the oligonucleotide chains on the surface of the gold nanoparticles were hybridized with bio-barcodes assembled by quantum dots (QD-probe2). The IMB/B. melitensis 16M/IgY-AuNP-probe1/QD-probe2 bioconjugates were concentrated by magnetic separation. Therefore, as the concentration of B. melitensis 16M in the sample increased, the unbound QD-probe2 in the supernatant reduced, and the B. melitensis 16M in the sample could be indirectly measured by detecting the fluorescence in the supernatant. This FSA method can detect B. melitensis 16M concentration in the range of 10 to 106 cfu ml-1 without pre-enrichment, and the limit of detection (LOD) is as low as 10 cfu ml-1 with high specificity. Furthermore, the proposed method for the detection of B. melitensis 16M has a LOD of 1.07 × 102 cfu ml-1 and a linear range from 102 to 107 cfu ml-1 in milk, and a LOD of 1.72 × 102 cfu ml-1, and a linear range from 102 to 106 cfu ml-1 in lamb leach. In addition, this method takes less than 3 h to perform. Thus, the assay that was developed in this study shows promise for rapid, sensitive, and specific detection of B. melitensis 16M.

In vitro investigation of the effects of boron nitride nanotubes and curcumin on DNA damage

BACKROUND

Stem cells provide an opportunity to analyse the effects of xenobiotic on cell viability, differentiation and cell functions. Evaluation of the possible cytotoxic and DNA damaging effects on bone marrow CD34+ stem cells is important for their ability to differentiate into blood cells, and also for bone marrow diseases therapy. Boron nitride nanotubes and curcumin are potential nanoformulation agents that can be used together in the treatment of cancer or bone marrow diseases. Therefore, it is important to evaluate their possible effects on different cell lines.

OBJECTIVES

In this study, it was aimed to evaluate the cytotoxic and DNA damaging effects of boron nitride nanotubes which are commonly used in pyroelectric, piezoelectric and optical applications, but there is not enough information about its biocompatibility. Also, it was intended to research the effects of curcumin being used frequently in treatment processes for antioxidant properties.

METHODS

The possible cytotoxic and DNA damaging effects of boron nitride nanotubes and curcumin on CD34+ cells, HeLa and V79 cells were evaluated by MTT assay and Comet assay, respectively.

RESULTS AND CONCLUSION

Boron nitride nanotubes and curcumin had cytotoxic effects and cause DNA damage on CD34+ cells, HeLa and V79 cells at several concentrations, probably because of increased ROS level. However, there were not concentration - dependent effect and there were controversial toxicity results of the studied cell lines. Its mechanism needs to be enlightened by further analysis for potential targeted drug development. Graphical abstract.

Plasmonic Nanomaterial-Based Optical Biosensing Platforms for Virus Detection

Plasmonic nanomaterials (P-NM) are receiving attention due to their excellent properties, which include surface-enhanced Raman scattering (SERS), localized surface plasmon resonance (LSPR) effects, plasmonic resonance energy transfer (PRET), and magneto optical (MO) effects. To obtain such plasmonic properties, many nanomaterials have been developed, including metal nanoparticles (MNP), bimetallic nanoparticles (bMNP), MNP-decorated carbon nanotubes, (MNP-CNT), and MNP-modified graphene (MNP-GRP). These P-NMs may eventually be applied to optical biosensing systems due to their unique properties. Here, probe biomolecules, such as antibodies (Ab), probe DNA, and probe aptamers, were modified on the surface of plasmonic materials by chemical conjugation and thiol chemistry. The optical property change in the plasmonic nanomaterials was monitored based on the interaction between the probe biomolecules and target virus. After bioconjugation, several optical properties, including fluorescence, plasmonic absorbance, and diffraction angle, were changed to detect the target biomolecules. This review describes several P-NMs as potential candidates of optical sensing platforms and introduces various applications in the optical biosensing field.

Localized surface plasmon resonance-mediated fluorescence signals in plasmonic nanoparticle-quantum dot hybrids for ultrasensitive Zika virus RNA detection via hairpin hybridization assays

The current epidemic caused by the Zika virus (ZIKV) and the devastating effects of this virus on fetal development, which result in an increased incidence of congenital microcephaly symptoms, have prompted the World Health Organization (WHO) to declare the ZIKV a public health issue of global concern. Efficient probes that offer high detection sensitivity and specificity are urgently required to aid in the point-of-care treatment of the virus. In this study, we show that localized surface plasmon resonance (LSPR) signals from plasmonic nanoparticles (NPs) can be used to mediate the fluorescence signal from semiconductor quantum dot (Qdot) nanocrystals in a molecular beacon (MB) biosensor probe for ZIKV RNA detection. Four different plasmonic NPs functionalized with 3-mercaptopropionic acid (MPA), namely MPA-AgNPs, MPA-AuNPs, core/shell (CS) Au/AgNPs, and alloyed AuAgNPs, were synthesized and conjugated to _L-glutathione-capped CdSeS alloyed Qdots to form the respective LSPR-mediated fluorescence nanohybrid. The concept of the plasmonic NP-Qdot-MB biosensor involves using LSPR from the plasmonic NPs to mediate a fluorescence signal to the Qdots, triggered by the hybridization of the target ZIKV RNA with the DNA loop sequence of the MB. The extent of the fluorescence enhancement based on ZIKV RNA detection was proportional to the LSPR-mediated fluorescence signal. The limits of detection (LODs) of the nanohybrids were as follows: alloyed AuAgNP-Qdot646-MB (1.7 copies/mL)) > CS Au/AgNP-Qdot646-MB (LOD =2.4 copies/mL) > AuNP-Qdot646-MB (LOD =2.9 copies/mL) > AgNP-Qdot646-MB (LOD =7.6 copies/mL). The LSPR-mediated fluorescence signal was stronger for the bimetallic plasmonic NP-Qdots than the single metallic plasmonic NP-Qdots. The plasmonic NP-Qdot-MB biosensor probes exhibited excellent selectivity toward ZIKV RNA and could serve as potential diagnostic probes for the point-of care detection of the virus.