Sensitive and simultaneous detection of different disease markers using multiplexed gold nanorods

Recent advances in gold nanoparticles-based biosensors for tuberculosis determination

Tuberculosis (TB) is one of the major killer diseases affecting lung parenchymal tissues. Mycobacterium tuberculosis (Mtb) is the bacterium that causes it. It most commonly affects the lungs, although it can affect any part of the body, including the stomach, glands, bones, and nervous system. Although anti-mycobacterial drugs are available, it remains a major threat to public health due to the rise of drug-resistant strains, and early and accurate diagnosis is very important. Currently, research science and medical communities are focusing on the use of cost-effective biosensors to manage human biological processes and assess accurate health diagnostics. Due to their high sensitivity in chemical and biological assays, nanomaterials have been considered in the field of biosensors for better diagnosis, and among them, gold nanoparticles (AuNPs) can play an important role in accelerating the diagnosis of TB. Superior biocompatibility, conductivity, catalytic properties, high surface-to-volume ratio, and high density enable their widespread use in the fabrication of biosensors. This review evaluates the diagnostic accuracy of AuNP-based biosensors for the detection of Mtb. According to different transducers of biosensors, their structure, performance, advantages and limitations are summarized and compared. Moreover, the upcoming challenges in their analytical performance have been highlighted and the strategies to overcome those challenges have been briefly discussed.

Emerging biomedical tools for biomarkers detection and diagnostics in schistosomiasis

Schistosomiasis is a neglected disease that strikes many people from tropical and subtropical countries where there are not satisfactory sanitation and wide access to clean water. Schistosoma spp., the causative agents of schistosomiasis, exhibit a quite complex life cycle that involves two hosts (humans and snails, respectively, the definitive and the intermediate), and five evolutive forms: cercariae (human infective form), schistosomula, adult worms, eggs, and miracidia. The techniques to diagnose schistosomiasis still have various limitations, mainly regarding low-intensity infections. Although various mechanisms associated with schistosomiasis have already been evidenced, there is still a need to fulfill the comprehension of this disease, especially to prospect for novel biomarkers to improve its diagnosis. Developing methods with more sensitivity and portability to detect the infection is valuable to reach schistosomiasis control. In this context, this review has gathered information not only on schistosomiasis biomarkers but also on emerging optical and electrochemical tools proposed in selected studies from about the last ten years. Aspects of the assays regarding the sensibility, specificity, and time needed for detecting diverse biomarkers are described. We hope this review can guide future developments in the field of schistosomiasis, contributing to improving its diagnosis and eradication.

Multiplexed Nanobiosensors: Current Trends in Early Diagnostics

The ever-growing demand for fast, cheap, and reliable diagnostic tools for personalised medicine is encouraging scientists to improve existing technology platforms and to create new methods for the detection and quantification of biomarkers of clinical significance. Simultaneous detection of multiple analytes allows more accurate assessment of changes in biomarker expression and offers the possibility of disease diagnosis at the earliest stages. The concept of multiplexing, where multiple analytes can be detected in a single sample, can be tackled using several types of nanomaterial-based biosensors. Quantum dots are widely used photoluminescent nanoparticles and represent one of the most frequent choices for different multiplex systems. However, nanoparticles that incorporate gold, silver, and rare earth metals with their unique optical properties are an emerging perspective in the multiplexing field. In this review, we summarise progress in various nanoparticle applications for multiplexed biomarkers.

Localized surface plasmon resonance based biosensing

INTRODUCTION

Bioanalytical sensing based on the principle of localized surface plasmon resonance experiences is currently an extremely rapid development. Novel sensors with new kinds of plasmonic transducers and innovative concepts for the signal development as well as read-out principles were identified. This review will give an overview of the development of this field. Areas covered: The focus is primarily on types of transducers by preparation or dimension, factors for optimal sensing concepts and the critical view of the usability of these devices as innovative sensors for bioanalytical applications. Expert commentary: Plasmonic sensor devices offer a high potential for future biosensing given that limiting factors such as long-time stability of the transducers, the required high sensitivity and the cost-efficient production are addressed. For higher sensitivity, the design of the sensor in shape and material has to be combined with optimal enhancement strategies. Plasmonic nanoparticles from bottom-up synthesis with a post-synthetic processing show a high potential for cost-efficient sensor production. Regarding the measurement principle, LSPRi offers a large potential for multiplex sensors and can provide a high-throughput as well as highly paralleled sensing. The main trends are expected towards optimal LSPR concepts which represent cost-efficient and robust point-of-care solutions, and the use of multiplexed devices for clinical applications.

Fabrication and spectroscopic studies of folic acid-conjugated Fe3O4@Au core-shell for targeted drug delivery application

Gold coated magnetite core shell is a kind of nanoparticle that include magnetic iron oxide core with a thin layer nanogold. Fe3O4-gold core-shell nanostructure can be used in biomedical applications such as magnetic bioseparation, bioimaging, targeting drug delivery and cancer treatment. In this study, the synthesis and characterization of gold coated magnetite nanoparticles were discussed. Magnetite nanoparticles with an average size of 6 nm in diameter were synthesized by the chemical co-precipitation method and gold-coated Fe3O4 core-shell nanostructures were produced with an average size of 11.5 nm in diameter by reduction of Au(3+) with citrate ion in the presence of Fe3O4. Folate-conjugated gold coated magnetite nanoparticles were synthesized to targeting folate receptor that is overexpressed on the surface of cancerous cells. For this purpose, we used l-cysteine, as a bi-functional linker for attachment to gold surface and it was linked to the gold nanoparticles surface through its thiol group. Then, we conjugated amino-terminated nanoparticles to folic acid with an amide-linkage formation. These gold magnetic nanoparticles were characterized by various techniques such as X-ray powder diffraction (XRD) analysis, Fourier transform infrared spectrometer (FT-IR), UV-visible spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), dispersive analysis of X-ray (EDAX) and vibrating sample magnetometer (VSM) analysis. The magnetic and optical properties of Fe3O4 nanostructure were changed by gold coating and attachment of l-cysteine and folic acid to Fe3O4@Au nanoparticles.

Gold nanorod biochip functionalization by antibody thiolation

Conjugation of biomolecules on gold nanorod (GNR) surfaces is the basis for successful applications in biosensing, imaging, and drug delivery. Current functionalization methods are often problematic, involving multi-step nanoparticle modification to replace surfactant bilayer, delicate nanoparticle protection during surfactant exchange, and material loss due to inevitable aggregation. Instead of intensive surface modification of GNRs, we describe herein a facile method to functionalize gold nanorod surfaces via covalent Au-S bonds by thiolating receptors. The resulting GNR-bioconjugates showed superior dispersion and stability in buffer for months without morphology change and aggregation. ELISA tests confirmed the high biofunctionality of the thiolated anti-IgG moieties immobilized on the GNR surfaces. Furthermore, this simple method facilitated a straightforward functionalization of GNR assembly on glass substrate to construct a specific biochip, which can detect human IgG targets in a label-free fashion with high sensitivity and specificity. Compared to electropolymeric coating to functionalize the GNR, our method exhibited a five-fold enhancement in the spectral sensitivity to refractive index change caused by the target binding. This universal GNR bioconjugation method can be extended to bind different proteins and antibodies for development of biosensors or drug delivery.

Vaccines and diagnostics for zoonotic schistosomiasis japonica

Schistosomiasis is one of the most prevalent, insidious and serious of the tropical parasitic diseases. Although the effective anthelmintic drug, praziquantel, is widely available and cheap, it does not protect against re-infection, drug-resistant schistosome may evolve and mass drug administration programmes based around praziquantel are probably unsustainable long term. Whereas protective anti-schistosome vaccines are not yet available, the zoonotic nature of Schistosoma japonicum provides a novel approach for developing a transmission-blocking veterinary vaccine in domestic animals, especially bovines, which are major reservoir hosts, being responsible for up to 90% of environmental egg contamination in China and the Philippines. However, a greater knowledge of schistosome immunology is required to understand the processes associated with anti-schistosome protective immunity and to reinforce the rationale for vaccine development against schistosomiasis japonica. Importantly as well, improved diagnostic tests, with high specificity and sensitivity, which are simple, rapid and able to diagnose light S. japonicum infections, are required to determine the extent of transmission interruption and the complete elimination of schistosomiasis following control efforts. This article discusses aspects of the host immune response in schistosomiasis, the current status of vaccine development against S. japonicum and reviews approaches for diagnosing and detecting schistosome infections in mammalian hosts.

Localized surface plasmon resonance as a biosensing platform for developing countries

The discovery of the phenomena known as localized surface plasmon resonance (LSPR) has provided the basis for many research areas, ranging from materials science to biosensing. LSPR has since been viewed as a transduction platform that could yield affordable, portable devices for a multitude of applications. This review aims to outline the potential applications within developing countries and the challenges that are likely to be faced before the technology can be effectively employed.

Plasmonic nanomaterials for biodiagnostics

The application of nanomaterials to detect disease biomarkers is giving rise to ultrasensitive assays, with scientists exploiting the many advantageous physical and chemical properties of nanomaterials. The fundamental basis of such work is to link unique phenomena that arise at the nanoscale to the presence of a specific analyte biomolecule, and to modulate the intensity of such phenomena in a ratiometric fashion, in direct proportion with analyte concentration. Precise engineering of nanomaterial surfaces is of utmost importance here, as the interface between the material and the biological environment is where the key interactions occur. In this tutorial review, we discuss the use of plasmonic nanomaterials in the development of biodiagnostic tools for the detection of a large variety of biomolecular analytes, and how their plasmonic properties give rise to tunable optical characteristics and surface enhanced Raman signals. We put particular focus on studies that have explored the efficacy of the systems using physiological samples in an effort to highlight the clinical potential of such assays.

Rapid optimization of metal nanoparticle surface modification with high-throughput gel electrophoresis

The ability to effectively control and optimize surface modification of metal nanoparticles is paramount to the ability to employ metal nanoparticles as diagnostic and therapeutic agents in biology and medicine. Here we present a high-throughput two-dimensional-grid gel electrophoresis cell (2D-GEC)-based method, capable of optimizing the surface modification of as many as 96 samples of metal nanoparticles in approximately 1 h. The 2D-GEC method determines not only the average zeta-potential of the modified particles but also the homogeneity of the surface modification by measuring the distance between the front of the sample track and the area where the maximum optical density is achieved. The method was tested for optimizing pH and concentration of the modifiers (pM) for functionalizing gold nanorod thiol-containing acidic agents.

Chemisorption assembly of Au nanorods on mercaptosilanized glass substrate for label-free nanoplasmon biochip

The fabrication of a localized surface plasmon resonance nanosensor in a chip based format that utilizes Au nanorods (GNRs) as the optical transducer were systematically studied. (3-mercaptopropyl)trimethoxysilane (MPTMS) modified glass substrate offers GNR deposition with maximal sensitivity to local refractive index changes, which subsequently results in better optical recognition of receptor-analyte binding. Kinetics governing the mass transport and chemisorption of nanorods from bulk to solid surface can be dynamically controlled in a predictable fashion. We demonstrate that slight aggregation induced by a low ionic strength (5 mM NaCl) can facilitate the nanorod assembly to result in a dense, well-distributed surface monolayer. In high ionic media (e.g. 40-80 mM), anions present electrostatically bind with the positively charged cetyltrimethylammonium bromide (CTAB) surrounding nanorod surfaces, thereby leading to instability with heavy aggregation in solution. However, once chemically bound on silanized substrates, the nanorods exhibit excellent stability in physiological buffer where high amount of ionic species are present. The fundamental study is followed by demonstration of a practical application of the fabricated biochip in label-free detection based on GNR wavelength shift of the longitudinal palsmon maxima as the optical signature of human IgG model detection.