Nanotechnology-Based Surface Plasmon Resonance Affinity Biosensors for In Vitro Diagnostics

Revolutionizing Stroke Care: Nanotechnology-Based Brain Delivery as a Novel Paradigm for Treatment and Diagnosis

Stroke, a severe medical condition arising from abnormalities in the coagulation-fibrinolysis cycle and metabolic processes, results in brain cell impairment and injury due to blood flow obstruction within the brain. Prompt and efficient therapeutic approaches are imperative to control and preserve brain functions. Conventional stroke medications, including fibrinolytic agents, play a crucial role in facilitating reperfusion to the ischemic brain. However, their clinical efficacy is hampered by short plasma half-lives, limited brain tissue distribution attributed to the blood-brain barrier (BBB), and lack of targeted drug delivery to the ischemic region. To address these challenges, diverse nanomedicine strategies, such as vesicular systems, polymeric nanoparticles, dendrimers, exosomes, inorganic nanoparticles, and biomimetic nanoparticles, have emerged. These platforms enhance drug pharmacokinetics by facilitating targeted drug accumulation at the ischemic site. By leveraging nanocarriers, engineered drug delivery systems hold the potential to overcome challenges associated with conventional stroke medications. This comprehensive review explores the pathophysiological mechanism underlying stroke and BBB disruption in stroke. Additionally, this review investigates the utilization of nanocarriers for current therapeutic and diagnostic interventions in stroke management. By addressing these aspects, the review aims to provide insight into potential strategies for improving stroke treatment and diagnosis through a nanomedicine approach.

Optical Sensors for Bacterial Detection

Analytical devices for bacterial detection are an integral part of modern laboratory medicine, as they permit the early diagnosis of diseases and their timely treatment. Therefore, special attention is directed to the development of and improvements in monitoring and diagnostic methods, including biosensor-based ones. A promising direction in the development of bacterial detection methods is optical sensor systems based on colorimetric and fluorescence techniques, the surface plasmon resonance, and the measurement of orientational effects. This review shows the detecting capabilities of these systems and the promise of electro-optical analysis for bacterial detection. It also discusses the advantages and disadvantages of optical sensor systems and the prospects for their further improvement.

Improvement of Seed-Mediated Growth of Gold Nanoparticle Labels for DNA Membrane-Based Assays

Gold nanoparticles (AuNPs) are popular labels for colorimetric detection of various analytes, involving proteins, nucleic acids, viruses, and whole cells because of their outstanding optical properties, inertness, and modification variability. In this work, we present an improved approach for enhancement of color intensity for DNA membrane microarrays based on seed-mediated growth of AuNP labels. Biotin-labeled DNA is hybridized with capture oligonucleotide probes immobilized on the microarrays. Then biotin is revealed by a streptavidin-AuNP conjugate followed by the detection of AuNPs. Optimization of seed-mediated enlargement of AuNPs by the reduction of tetrachloroauric acid with hydroxylamine made it possible to change the coloring of specific spots on the microarrays from pink to a more contrasting black with minor background staining. Mean size of the resulting AuNPs was four times larger than before the enhancement. Adjusting the pH of HAuCl₄ solution to 3.5 and use of a large excess of hydroxylamine increased the signal/background ratio by several times. The method's applicability was demonstrated for quantification of a short oligonucleotide of 19 bases and full-length TEM-type β-lactamase genes of 860 bp responsible for the development of bacterial resistance against β-lactam antibiotics. Improved protocol for AuNP enlargement may be further transferred to any other membrane-based assays of nucleic acids with both instrumental and visual colorimetric detection.

Chitosan mediated layer-by-layer assembly based graphene oxide decorated surface plasmon resonance biosensor for highly sensitive detection of β-amyloid

Alzheimer's disease (AD), and its consequent effect primarily clinical dementia, Parkinson's disease dementia, etc. currently bring potential avenues for diagnosis centered on identification of beta-amyloid_1-42 (Aβ_1-42). Unfortunately, techniques engaged in AD core biomarker (Aβ_1-42) detection are majorly suffering from poor sensitivity and selectivity. Thus, we fabricated graphene oxide (GO) surface decorated chitosan (CS) mediated layer-by-layer (LbL) assembly based surface plasmon resonance (SPR) biosensor for highly sensitive and selective recognition of Aβ_1-42. Briefly, silver nanoparticles (AgNPs) and GO synthesis were achieved through a greener approach. LbL assembly was designed using CS and polystyrene sulphonate (PSS) on surface of AgNPs (AgNPs-CS-PSS-CS) and then antibodies of Aβ (anti-Aβ) were fixed on LbL assembly (AgNPs-CS-PSS-CS@anti-Aβ). Herein, amine functionality of CS offers a plethora of sites for anti-Aβ antibody immobilization that gives specific direction, high selectivity, and an adequate amount of antibody immobilization. For fabrication, synthesized GO was immobilized on an amine-modified gold-coated sensor chip via carbodiimide chemistry followed by AgNPs-CS-PSS-CS@anti-Aβ immobilization on an activated GO surface. Inimitable features of LbL assembly showed improved selectivity towards Aβ peptide whereas utilization of affinity biotransducer with a combination of plasmonic and non-plasmonic nanomaterial improved sensitivity and selectivity. Consequently, linearity range and limit of detection (LOD) of Aβ_1-42 antigens were found to be 2 fg/mL to 400 ng/mL and 1.21 fg/mL, respectively. Moreover, analysis of Aβ_1-42 in AD-induced rats confirmed the real-time-applicability of the designed SPR biosensor. Hence, GO surface decorated AgNPs-CS-PSS-CS@anti-Aβ mediated SPR biosensor would provide a novel approach for exceptionally sensitive and selective Aβ detection.

Advances in surface plasmon resonance-based biosensor technologies for cancer biomarker detection

Surface plasmon resonance approach is a highly useful option to offer optical and label-free detection of target bioanalytes with numerous advantages (e.g., low-cost fabrication, appreciable sensitivity, label-free detection, and outstanding accuracy). As such, it allows early diagnosis of cancer biomarkers to monitor tumor progression and to prevent the recurrence of oncogenic tumors. This work highlights the recent progress in SPR biosensing technology for the diagnosis of various cancer types (e.g., lung, breast, prostate, and ovarian). Further, the performance of various SPR biosensors is also evaluated in terms of the basic quality assurance criteria (e.g., limit of detection (LOD), selectivity, sensor response time, and reusability). Finally, the limitations and future challenges associated with SPR biosensors are also discussed with respect to cancer biomarker detection.

Self-Assembling Nucleic Acid Nanostructures Functionalized with Aptamers

Researchers have worked for many decades to master the rules of biomolecular design that would allow artificial biopolymer complexes to self-assemble and function similarly to the diverse biochemical constructs displayed in natural biological systems. The rules of nucleic acid assembly (dominated by Watson-Crick base-pairing) have been less difficult to understand and manipulate than the more complicated rules of protein folding. Therefore, nucleic acid nanotechnology has advanced more quickly than de novo protein design, and recent years have seen amazing progress in DNA and RNA design. By combining structural motifs with aptamers that act as affinity handles and add powerful molecular recognition capabilities, nucleic acid-based self-assemblies represent a diverse toolbox for use by bioengineers to create molecules with potentially revolutionary biological activities. In this review, we focus on the development of self-assembling nucleic acid nanostructures that are functionalized with nucleic acid aptamers and their great potential in wide ranging application areas.

Emerging Biosensors to Detect Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Review

Coronavirus disease (COVID-19) is a global health crisis caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) is the gold standard test for diagnosing COVID-19. Although it is highly accurate, this lab test requires highly-trained personnel and the turn-around time is long. Rapid and inexpensive immuno-diagnostic tests (antigen or antibody test) are available, but these point of care (POC) tests are not as accurate as the RT-PCR test. Biosensors are promising alternatives to these rapid POC tests. Here we review three types of recently developed biosensors for SARS-CoV-2 detection: surface plasmon resonance (SPR)-based, electrochemical and field-effect transistor (FET)-based biosensors. We explain the sensing principles and discuss the advantages and limitations of these sensors. The accuracies of these sensors need to be improved before they could be translated into POC devices for commercial use. We suggest potential biorecognition elements with highly selective target-analyte binding that could be explored to increase the true negative detection rate. To increase the true positive detection rate, we suggest two-dimensional materials and nanomaterials that could be used to modify the sensor surface to increase the sensitivity of the sensor.

Recent trends in analytical and digital techniques for the detection of the SARS-Cov-2

The current global outbreak of COVID-19 due to SARS-CoV-2 is an unprecedented humanitarian crisis. Considering the gravity of its impact there is an immediate need to develop a detection technique that is sensitive, specific, fast, and affordable for the clinical diagnosis of the disease. Real time Polymerase Chain Reaction (RT-PCR)-based detection platforms are contemplated to be the gold standard to detect viral RNA. However, that may be susceptible to errors, and there is a risk of obtaining false results, which ultimately compromises the strategy of efficient disease management. Several modern techniques exhibiting assured results with enhanced sensitivity and specificity against the SARS-CoV-2 associated viral components or immune response against it have been developed and may be implemented. The review deals with the conventional RT-PCR detection techniques and compares them to other detection platforms viz., biosensor based detection of antigens, fluorescent or colorimetric detection systems including CRISPR-Cas 13 based SHERLOCK kit, CRISPR Cas-9 based FELUDA test kit, CRISPR DETECTR kit, Next Generation Sequencing or microarray-based kits. These modern techniques are great as a point of care detection methods but should be followed by RT PCR based detection for the confirmation of COVID-19 status.

Nanobiosensors as new diagnostic tools for SARS, MERS and COVID-19: from past to perspectives

The severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) and novel coronavirus 19 (COVID-19) epidemics represent the biggest global health threats in the last two decades. These infections manifest as bronchitis, pneumonia or severe, sometimes fatal, respiratory illness. The novel coronavirus seems to be associated with milder infections but it has spread globally more rapidly becoming a pandemic. This review summarises the state of the art of nanotechnology-based affinity biosensors for SARS, MERS and COVID-19 detection. The nanobiosensors are antibody- or DNA-based biosensors with electrochemical, optical or FET-based transduction. Various kinds of nanomaterials, such as metal nanoparticles, nanowires and graphene, have been merged to the affinity biosensors to enhance their analytical performances. The advantages of the use of the nanomaterials are highlighted, and the results compared with those obtained using non-nanostructured biosensors. A critical comparison with conventional methods, such as RT-PCR and ELISA, is also reported. It is hoped that this review will provide interesting information for the future development of new reliable nano-based platforms for point-of-care diagnostic devices for COVID-19 prevention and control.

Acoustic Methodology for Selecting Highly Dissipative Probes for Ultrasensitive DNA Detection

The objective of this work is to present a methodology for the selection of nanoparticles such as liposomes to be used as acoustic probes for the detection of very low concentrations of DNA. Liposomes, applied in the past as mass amplifiers and detected through frequency measurement, are employed in the current work as probes for energy-dissipation enhancement. Because the dissipation signal is related to the structure of the sensed nanoentity, a systematic investigation of the geometrical features of the liposome/DNA complex was carried out. We introduce the parameter of dissipation capacity by which several sizes of liposome and DNA structures were compared with respect to their ability to dissipate acoustic energy at the level of a single molecule/particle. Optimized 200 nm liposomes anchored to a dsDNA chain led to an improvement of the limit of detection (LoD) by 3 orders of magnitude when compared to direct DNA detection, with the new LoD being 1.2 fmol (or 26 fg/μL or 2 pM). Dissipation monitoring was also shown to be 8 times more sensitive than the corresponding frequency response. The high versatility of this new methodology is demonstrated in the detection of genetic biomarkers down to 1-2 target copies in real samples such as blood. This study offers new prospects in acoustic detection with potential use in real-world diagnostics.

pH-Based Detection of Target Analytes in Diluted Serum Samples Using Surface Plasmon Resonance Immunosensor

Detection of minute quantities of target antigens in serum samples (consisting of a mixture of proteins/biomolecules) can be achieved by enhancement of the capture efficiencies of heterogeneous immunosensors. An important process parameter which affects the capture of target analytes in such immunosensors is the pH of the solution as the target proteins present in the serum samples are charged molecules. Here, we investigated the capture of prostate-specific antigens (PSAs), first in a mixed-analyte system wherein the solution contained two other non-specific proteins along with the target analyte, using the surface plasmon resonance spectroscopy. There are no reports on the detection of antigens in a mixed system based on the optimization of the pH values of the carrier fluid, and this is the motivation of the present work. Further, we studied interference effects caused by the presence of these non-specific proteins in the mixed-analyte systems by artificially increasing the ratio of the interfering proteins to that of the target protein. Eventually PSA spiked into the rabbit serum samples was captured through the optimization of the pH of the solution. We could detect PSA in the serum samples when diluted to 100 times or more, where the amounts of other interfering proteins were ~ 66 times that of the amount of PSA. This study proposes a heterogeneous immunosensor to detect the target analytes in the diluted serum samples by tuning pH the of solution mixture, which can be utilized to detect disease biomarkers in serum samples.

Improving health-care delivery in low-resource settings with nanotechnology: Challenges in multiple dimensions

In the two decades after 1990, the rates of child and maternal mortality dropped by over 40% and 47%, respectively. Despite these improvements, which are in part due to increased access to medical technologies, profound health disparities exist. In 2015, a child born in a developing region is nearly eight times as likely to die before the age of 5 than one born in a developed region and developing regions accounted for nearly 99% of the maternal deaths. Recent developments in nanotechnology, however, have great potential to ameliorate these and other health disparities by providing new cost-effective solutions for diagnosis or treatment of a variety of medical conditions. Affordability is only one of the several challenges that will need to be met to translate new ideas into a medical product that addresses a global health need. This article aims to describe some of the other challenges that will be faced by nanotechnologists who seek to make an impact in low-resource settings across the globe.