Localized surface plasmon coupled fluorescence fiber-optic biosensor with gold nanoparticles

Signal-Amplified Nanobiosensors for Virus Detection Using Advanced Nanomaterials

Rapid diagnosis and treatment of infectious illnesses are crucial for clinical outcomes and public health. Biosensing developments enhance diagnostics at the point of care. This is superior to traditional procedures, which need centralized lab facilities, specialized personnel, and large equipment. The emerging coronavirus epidemic threatens global health and economic security. Increasing viral surveillance and regulatory actions against disease transmission necessitate rapid, sensitive testing tools for viruses. Due to their sensitivity and specificity, biosensors offer a possible reliable and quantifiable viral detection method. Current advances in genetic engineering, such as genetic alteration and material engineering, have provided several opportunities to enhance biosensors' sensitivity, selectivity, and recognition efficiency. This chapter explains biosensing techniques, biosensor varieties, and signal amplification technologies. Challenges and potential developments for viral microorganisms based on biosensors and signal amplification were also investigated.

Carbon nanotubes in COVID-19: A critical review and prospects

The rapid spread of Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2) around the world has ravaged both global health and economy. This unprecedented situation has thus garnered attention globally. This further necessitated the deployment of an effective strategy for rapid and patient-compliant identification and isolation of patients tested positive for SARS-CoV-2. Following this, several companies and institutions across the globe are striving hard to develop real-time methods, like biosensors for the detection of various viral components including antibodies, antigens, ribonucleic acid (RNA), or the whole virus. This article attempts to review the various, mechanisms, advantages and limitations of the common biosensors currently being employed for detection. Additionally, it also summarizes recent advancements in various walks of fighting COVID-19, including its prevention, diagnosis and treatment.

State-of-the-Art of Nanodiagnostics and Nanotherapeutics against SARS-CoV-2

The pandemic outbreak of SARS-CoV-2, with millions of infected patients worldwide, has severely challenged all aspects of public health. In this regard, early and rapid detection of infected cases and providing effective therapeutics against the virus are in urgent demand. Along with conventional clinical protocols, nanomaterial-based diagnostics and therapeutics hold a great potential against coronavirus disease 2019 (COVID-19). Indeed, nanoparticles with their outstanding characteristics would render additional advantages to the current approaches for rapid and accurate diagnosis and also developing prophylactic vaccines or antiviral therapeutics. In this review, besides presenting an overview of the coronaviruses and SARS-CoV-2, we discuss the introduced nanomaterial-based detection assays and devices and also antiviral formulations and vaccines for coronaviruses.

Optical Biosensors for Virus Detection: Prospects for SARS-CoV-2/COVID-19

The recent pandemic of the novel coronavirus disease 2019 (COVID-19) has caused huge worldwide disruption due to the lack of available testing locations and equipment. The use of optical techniques for viral detection has flourished in the past 15 years, providing more reliable, inexpensive, and accurate detection methods. In the current minireview, optical phenomena including fluorescence, surface plasmons, surface-enhanced Raman scattering (SERS), and colorimetry are discussed in the context of detecting virus pathogens. The sensitivity of a viral detection method can be dramatically improved by using materials that exhibit surface plasmons or SERS, but often this requires advanced instrumentation for detection. Although fluorescence and colorimetry lack high sensitivity, they show promise as point-of-care diagnostics because of their relatively less complicated instrumentation, ease of use, lower costs, and the fact that they do not require nucleic acid amplification. The advantages and disadvantages of each optical detection method are presented, and prospects for applying optical biosensors in COVID-19 detection are discussed.

Biosensor and molecular-based methods for the detection of human coronaviruses: A review

The ongoing crisis due to the global pandemic caused by a highly contagious coronavirus (Coronavirus disease - 2019; COVID-19) and the lack of either proven effective therapy or a vaccine has made diagnostic a valuable tool in disease tracking and prevention. The complex nature of this newly emerging virus calls for scientists' attention to find the most reliable, highly sensitive, and selective detection techniques for better control or spread of the disease. Reverse transcriptase-polymerase chain reaction (RT-PCR) and serology-based tests are currently being used. However, the speed and accuracy of these tests may not meet the current demand; thus, alternative technology platforms are being developed. Nano biosensor technology platforms have been established as a promising diagnostic tool for rapid and accurate detection of viruses as well as other life-threatening diseases even in resource-limited settings. This review aims to provide a short overview of recent advancements in molecular and biosensor-based diagnosis of viruses, including the human coronaviruses, and highlight the challenges and future perspectives of these detection technologies.

Growth of Spherical Gold Satellites on the Surface of Au@Ag@SiO2 Core-Shell Nanostructures Used for an Ultrasensitive SERS Immunoassay of Alpha-Fetoprotein

The identification and detection of cancer biomarkers in early stages is an important issue for the therapy of cancer. However, most methods are time-consuming and have limited sensing sensitivity and specificity. In this work, we prepared a novel plasmonic multilayered core-shell-satellite nanostructure (Au@Ag@SiO₂-AuNP) consisting of a gold nanosphere with a silver coating core (Au@Ag), an ultrathin continuous silica (SiO₂) shell, and a high coverage of gold nanosphere (AuNP) satellites. The Au@Ag core is a prominent surface enhanced Raman scattering (SERS) platform, and the thin SiO₂ layer exhibits a long-range plasmon coupling between the Au@Ag core to the AuNP satellites, further leading to enhanced Raman scattering. Meanwhile, the outer AuNP satellites have a high biocompatibility and long-term stability. Combining the above advantages, the well-designed metallic nanoassemblies would be a promising candidate for SERS-based applications in biochemistry. For specific detection of alpha-fetoprotein (AFP), we utilized the SERS-active core-shell-satellite nanostructures modified with AFP antibody as immune probes and nitrocellulose membrane (NC) stabilized captured anti-AFP antibodies as solid substrate. To improve the detection performance, we further systematically optimized the parameters, including the silver coating thickness of the Au@Ag core and the density and size of the satellite AuNPs. Under the optimized conditions, AFP could be detected by the SERS-based sandwich immunoassay with an ultralow detection limit of 0.3 fg/mL, and the method exhibited a wide linear response from 1 fg/mL to 1 ng/mL. The limit of detection (LOD) was considerably lower than conventional methods in the literature. This work relies on the unique Au@Ag@SiO₂-AuNP nanostructures as the immune probe develops a new outlook for the application of multilayered nanoassemblies and demonstrates the great potential in early tumor marker detection.

A repertoire of biomedical applications of noble metal nanoparticles

The emerging properties of noble metal nanoparticles are attracting huge interest from the translational scientific community. In this feature article, we highlight recent advances in the adaptation of noble metal nanomaterials and their biomedical applications in therapeutics, diagnostics and sensing.

Urine Cofilin-1 Detection for Predicting Type 1 Cardiorenal Syndrome in the Coronary Care Unit: A Gold Nanoparticle- and Laser-Based Approach

BACKGROUND

Type 1 cardiorenal syndrome (CRS) is a severe complication for acute decompensated heart failure patients. This study aimed at evaluating the feasibility of using the gold nanoparticle-based localized surface plasmon-coupled fluorescence biosensor (LSPCFB) to detect urine cofilin-1 as a biomarker for predicting CRS among patients in the coronary care unit (CCU).

METHODS

A total of 44 patients were included with prospectively collected urine and blood samples. Both LSPCFB and conventional enzyme-linked immunosorbent assays (ELISAs) were used to measure urine cofilin-1 at admission to the CCU. The occurrence of CRS was judged within 7 days after admission. The discrimination presented as the area under the receiver operating characteristic curve (AUROC) and calibration of both detection methods were used to assess the predictive ability of urine cofilin-1 measured by the LSPCFB and ELISA.

RESULTS

Thirteen patients were diagnosed with CRS, while the other 31 patients were classified into a non-CRS group. For predicting CRS by measuring urine cofilin-1, the LSPCFB had higher accuracy (AUROC: 0.707, p = 0.031; overall accuracy: 79.55%) than the ELISA (AUROC: 0.479, p = 0.827; overall accuracy: 53.27%). The positive and negative predictive values of the LSPCFB were also higher than those of the ELISA (positive predictive value: 70.0 vs. 34.8%; negative predictive value: 82.4 vs. 76.2%).

CONCLUSIONS

The gold nanoparticle-based immunoassay LSPCFB could exploit the potential of urine cofilin-1 as a single biomarker to predict CRS among CCU patients.

Specific Detection of Carcinoembryonic Antigen Based on Fluorescence Quenching of Hollow Porous Gold Nanoshells with Roughened Surface

The detection of tumor biomarkers in the early stage is highly desirable for the therapy of cancer. However, rapid, low-cost, sensitive, and selective detection of biomarkers remains a challenge owing to the sequence homology, short length, and low abundance. This Research Article describes the synthesis of a novel carcinoembryonic antigen (CEA) probe using hollow porous gold nanoparticles (HPGNPs) with roughened surface based on fluorescence quenching. For specific detection of CEA, the surface of HPGNP is modified by carboxyl modification, carboxyl activation, and antibody conjugation. Furthermore, to enhance the detection performance, we have systematically optimized the parameters, such as particle size, surfactants, surface roughness, surface hole size, and the molecule-particle distance (MPD). The results demonstrate that the fluorescence quenching efficiency would be enhanced with a larger particle size and surface hole size, roughened surface and a greater MPD. Also, with careful inspection of different surfactants of CTAB and PVP, we find that PVP has the optimal performance on fluorescence quenching. Under these optimized conditions, CEA could be detected with an ultralow detection limit of 1.5 pg/mL, and the probe shows a linear range from 2 to 100 pg/mL. The limit of detection is an order of intensity lower than related methods. Interference experiment results have shown that the influence of the interfering proteins could be neglected in the detection procedure.

Magnetic Nanoparticles for Antibiotics Detection

Widespread use of antibiotics has led to pollution of waterways, potentially creating resistance among freshwater bacterial communities. Microorganisms resistant to commonly prescribed antibiotics (superbug) have dramatically increased over the last decades. The presence of antibiotics in waters, in food and beverages in both their un-metabolized and metabolized forms are of interest for humans. This is due to daily exposure in small quantities, that, when accumulated, could lead to development of drug resistance to antibiotics, or multiply the risk of allergic reaction. Conventional analytical methods used to quantify antibiotics are relatively expensive and generally require long analysis time associated with the difficulties to perform field analyses. In this context, electrochemical and optical based sensing devices are of interest, offering great potentials for a broad range of analytical applications. This review will focus on the application of magnetic nanoparticles in the design of different analytical methods, mainly sensors, used for the detection of antibiotics in different matrices (human fluids, the environmental, food and beverages samples).

Weakening Circular Dichroism of Plasmonic Nanospirals Induced by Surface Grafting with Alkyl Ligands

Silver nanospirals with strong chiroptical activity (characterized by circular dichroism) are grafted with achiral alkyl ligands, resulting in a weakening of the chiroptical activity. The chiroptical weakening is exacerbated with increasing bond energy of the Ag-ligand contacts, which is ascribed to the effective medium screening effect and electron withdrawal toward the alkyl ligands.

Silver island film substrates for ultrasensitive fluorescence detection of (bio)molecules

A silver island film (SIF) substrate was used to demonstrate that Metal-Enhanced Fluorescence (MEF) is a powerful tool to enable detection of emission from (bio)molecules at very low concentrations. The experiments were carried out with the Fenna-Matthews-Olson (FMO) pigment-protein complex from the photosynthetic green sulfur bacterium Chlorobaculum tepidum. FMO was diluted to a level, at which no emission was detectable on a glass substrate. In contrast, the fluorescence of FMO was readily observed on the SIF substrate, even though the emission wavelength of FMO is displaced by over 300 nm from the maximum of the plasmon resonance of the SIF layer. Estimated enhancements of the fluorescence intensity of FMO on SIF are about 40-fold. The enhancement factor correlates with the improvement of the signal-to-noise ratio for FMO emission on SIF substrates.

Smart design of fiber optic surfaces for improved plasmonic biosensing

Although the phenomenon of surface plasmon resonance (SPR) is known for more than a century now, traditional prism-based SPR platforms have hardly escaped the research laboratories despite being recognized for the sensitive and specific performance. Significant efforts have been made over the last years to overcome their existing limitations by coupling the SPR phenomenon to the fiber optic (FO) technology. While this platform has been promoted as cost-effective and simpler alternative capable of handling label-free bioassays, quantification and real-time monitoring of biomolecular interactions, examples of its applicability in sensing and biosensing remain to date very limited. The FO-SPR system is still in development and requires further advancements for reaching the stability and sensitivity of the benchmark SPR systems. Among existing strategies for device improvement, those based on modifying the FO tips using nanomaterials are mostly studied. These small-scale objects provide a wide range of possibilities for alternating the architecture of the FO sensitive zone, enabling also unique effects such as localized SPR (LSPR). This mini-review summarizes the latest innovations in the fabrication procedures which use nanoparticles or other nanomaterials, aiming at FO-SPR technology performance improvements, as well as addition of new device features and functionalities.

Diagnosis of human metapneumovirus in patients hospitalized with acute lower respiratory tract infection using a metal-enhanced fluorescence technique

Human metapneumovirus (hMPV) is a common respiratory tract infection in children. However, conventional immunofluorescence assays (IFAs) for detecting hMPV in respiratory samples have limited reliability with a sensitivity and false-negative predictive value of 58.1% and approximately 17.8%, respectively. In this study, hMPV was measured in 91 clinical respiratory samples (55 sputum and 36 nasopharyngeal aspirate samples), which were obtained from children under three years of age, utilizing our previously developed high-throughput metal-enhanced fluorescence (MEF)-based biosensor (HT-MEFB). The sensitivity of HT-MEFB for hMPV detection in the 91 samples was improved by up to 77.4% compared with that obtained with IFAs, and the specificity of HT-MEFB for hMPV detection was 91.7%. In addition, the specificity and accuracy obtained after the selection of 55 sputum samples as the analyzed specimen reached 92.3% and 90.9%, respectively. Thus, in terms of accuracy, high throughput, and sensitivity, HT-MEFB exhibits considerable potential for hMPV detection in clinical settings.

Molecular plasmonics for nanoscale spectroscopy

Surface- and tip-enhanced Raman and LSPR spectroscopies have developed over the past 15 years as unique tools for uncovering the properties of single particles and single molecules that are unobservable in ensemble measurements. Measurements of individual events provide insight into the distribution of molecular properties that are averaged over in ensemble experiments. Raman and LSPR spectroscopy can provide detailed information on the identity of molecular species and changes in the local environment, respectively. In this review a detailed discussion is presented on single-molecule and single-particle Raman and LSPR spectroscopy focusing on the major developments in the fields and applications of the techniques.

Optical detection of NADH based on biocatalytic growth of Au-Ag core-shell nanoparticles

We have developed an optical assay for NADH (Dihydronicotinamide adenine dinucleotide) based on the catalytic growth of gold-silver core-shell nanoparticles (Au-Ag-CSNPs). The nanoparticles were immobilized on pretreated glass slide and are shown to catalyze the NADH-mediated reduction of Ag(I) ions in the presence of 1,4-benzoquinone and cetyltrimethyl ammonium ion. This leads to the formation of Au-Ag-CSNPs on the glass. The absorption peak of the Au-Ag-CSNPs at 415 nm increases with the concentration of NADH in the solution used, and this can be measured by UV-vis photometry. High-resolution scanning electron microscopy analysis of the morphology of the surface of the Au-Ag-CSNPs before and after the catalytic reaction revealed a growth of their diameter. Under optimal conditions, NADH can be determined in the concentration range from 0.2 to 3.2mM, and the detection limit is 15.6 μM. The sensor has good precision and good storage stability, simple in operation, and can be fabricated at low costs, which made it suitable for the determination of NADH in complex biological systems and in related degradation processes of contaminants.

Nanoparticles prepared from the water extract of Gusuibu (Drynaria fortunei J. Sm.) protects osteoblasts against insults and promotes cell maturation

Our previous study showed that Gusuibu (Drynaria fortunei J. Sm.) can stimulate osteoblast maturation. This study was further designed to evaluate the effects of nanoparticles prepared from the water extract of Gusuibu (WEG) on osteoblast survival and maturation. Primary osteoblasts were exposed to 1, 10, 100, and 1000 μg/mL nanoparticles of WEG (nWEG) for 24, 48, and 72 hours did not affect morphologies, viability, or apoptosis of osteoblasts. In comparison, treatment of osteoblasts with 1000 μg/mL WEG for 72 hours decreased cell viability and induced DNA fragmentation and cell apoptosis. nWEG had better antioxidant bioactivity in protecting osteoblasts from oxidative and nitrosative stress-induced apoptosis than WEG. In addition, nWEG stimulated greater osteoblast maturation than did WEG. Therefore, this study shows that WEG nanoparticles are safer to primary osteoblasts than are normal-sized products, and may promote better bone healing by protecting osteoblasts from apoptotic insults, and by promoting osteogenic maturation.

Detection of swine-origin influenza A (H1N1) viruses using a localized surface plasmon coupled fluorescence fiber-optic biosensor

Swine-origin influenza A (H1N1) virus (S-OIV) was identified as a new reassortant strain of influenza A virus in April 2009 and led to an influenza pandemic. Accurate and timely diagnoses are crucial for the control of influenza disease. We developed a localized surface plasmon coupled fluorescence fiber-optic biosensor (LSPCF-FOB) which combines a sandwich immunoassay with the LSP technique using antibodies against the hemagglutinin (HA) proteins of S-OIVs. The detection limit of the LSPCF-FOB for recombinant S-OIV H1 protein detection was estimated at 13.9 pg/mL, which is 10³-fold better than that of conventional capture ELISA when using the same capture antibodies. For clinical S-OIV isolates measurement, meanwhile, the detection limit of the LSPCF-FOB platform was calculated to be 8.25 × 10⁴ copies/mL, compared with 2.06 × 10⁶ copies/mL using conventional capture ELISA. Furthermore, in comparison with the influenza A/B rapid test, the detection limit of the LSPCF-FOB for S-OIV was almost 50-fold in PBS solution and 25-fold lower in mimic solution, which used nasal mucosa from healthy donors as the diluent. The findings of this study therefore indicate that the high detection sensitivity and specificity of the LSPCF-FOB make it a potentially effective diagnostic tool for clinical S-OIV infection and this technique has the potential to be applied to the development of other clinical microbe detection platforms.

Detection of severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein in human serum using a localized surface plasmon coupled fluorescence fiber-optic biosensor

In order to enhance the sensitivity of conventional immunoassay technology for the detection of SARS coronavirus (SARS-CoV) nucleocapsid protein (N protein), we developed a localized surface plasmon coupled fluorescence (LSPCF) fiber-optic biosensor that combines sandwich immunoassay with the LSP technique. Experimentally, a linear relationship between the fluorescence signal and the concentration of recombinant SARS-CoV N (GST-N) protein in buffer solution could be observed from 0.1 pg/mL to 1 ng/mL. In addition, the concentration of GST-N protein in diluted serum across a similar range could also be measured. The correlation coefficients (linear scale) for these two measurements were 0.9469 and 0.9624, respectively. In comparison with conventional enzyme linked immunosorbent assay (ELISA), the detection limit of the LSPCF fiber-optic biosensor for the GST-N protein was improved at least 10⁴-fold using the same monoclonal antibodies. Therefore, the LSPCF fiber-optic biosensor shows an ability to detect very low concentration (∼1 pg/mL) of SARS-CoV N protein in serum. The biosensor should help with the early diagnosis of SARS infection.

Gold nanoparticles in nanomedicine: preparations, imaging, diagnostics, therapies and toxicity

This critical review provides an overall survey of the basic concepts and up-to-date literature results concerning the very promising use of gold nanoparticles (AuNPs) for medicinal applications. It includes AuNP synthesis, assembly and conjugation with biological and biocompatible ligands, plasmon-based labeling and imaging, optical and electrochemical sensing, diagnostics, therapy (drug vectorization and DNA/gene delivery) for various diseases, in particular cancer (also Alzheimer, HIV, hepatitis, tuberculosis, arthritis, diabetes) and the essential in vitro and in vivo toxicity. It will interest the medicine, chemistry, spectroscopy, biochemistry, biophysics and nanoscience communities (211 references).

Fluorescence enhancements of fiber-optic biosensor with metallic nanoparticles

The mechanism of fluorescence enhancements of fiber-optic biosensor with metallic nanoparticles is studied using scattering theory of evanescent waves by a metallic nanoparticle in dilute solution approximation. High local-field enhancement in the vicinity of metallic nanoparticles resulting from localized surface plasmon excitation and the fluorescence enhancement is estimated by calculating averaged local-field enhancement and radiative-rate enhancement of fluorophores in the presence of metallic anoparticles. The metallic nanoparticles not only provide strong local field to enhance the fluorescence signal of fluorophores, but also help to scatter the fluorescence signal and to increase the far-field detectable signals of the fiber-optic biosensor. The effects of the radius of gold nanoparticles, fluorophore-particle separation, and fiber-particle separation on the fluorescence enhancement are discussed in detail.

Gold nanoparticles for the development of clinical diagnosis methods

The impact of advances in nanotechnology is particularly relevant in biodiagnostics, where nanoparticle-based assays have been developed for specific detection of bioanalytes of clinical interest. Gold nanoparticles show easily tuned physical properties, including unique optical properties, robustness, and high surface areas, making them ideal candidates for developing biomarker platforms. Modulation of these physicochemical properties can be easily achieved by adequate synthetic strategies and give gold nanoparticles advantages over conventional detection methods currently used in clinical diagnostics. The surface of gold nanoparticles can be tailored by ligand functionalization to selectively bind biomarkers. Thiol-linking of DNA and chemical functionalization of gold nanoparticles for specific protein/antibody binding are the most common approaches. Simple and inexpensive methods based on these bio-nanoprobes were initially applied for detection of specific DNA sequences and are presently being expanded to clinical diagnosis. Figure Colorimetric DNA/RNA detection using salt induced aggregation of AuNP-DNA nanoprobes.