Recent Developments in Innovative Magnetic Nanoparticles-Based Immunoassays: From Improvement of Conventional Immunoassays to Diagnosis of COVID-19

Accuracy improvement enzyme-linked immunosorbent assay using superparamagnetic/polyethylene glycol) nanoparticles for leishmaniasis diagnostic

Serodiagnosis methods have been used as platforms for diagnostic tests for many diseases. Due to magnetic nanoparticles' properties to quickly detach from an external magnetic field and particle size effects, these nanomaterials' functionalization allows the specific isolation of target analytes, enhancing accuracy parameters and reducing serodiagnosis time. Superparamagnetic iron oxide nanoparticles (MNPs) were synthesized and functionalized with polyethylene glycol (PEG) and then associated with the synthetic Leishmaniosis epitope. This nano-peptide antigen showed promising results. Regarding Tegumentary leishmaniasis diagnostic accuracy, the AUC was 0.8398 with sensibility 75% (95CI% 50.50 - 89.82) and specificity 87.50% (95CI% 71.93 - 95.03), and Visceral leishmaniasis accuracy study also present high performance, the AUC was 0.9258 with sensibility 87.50% (95CI% 63.98 - 97.78) and specificity 87.50% (95CI% 71.93 - 95.03). Our results demonstrate that the association of the antigen with MNPs accelerates and improves the diagnosis process. MNPs could be an important tool for enhancing serodiagnosis.

Advancements in magnetic nanoparticle-based biosensors for point-of-care testing

The significance of point-of-care testing (POCT) in early clinical diagnosis and personalized patient care is increasingly recognized as a crucial tool in reducing disease outbreaks and improving patient survival rates. Within the realm of POCT, biosensors utilizing magnetic nanoparticles (MNPs) have emerged as a subject of substantial interest. This review aims to provide a comprehensive evaluation of the current landscape of POCT, emphasizing its growing significance within clinical practice. Subsequently, the current status of the combination of MNPs in the Biological detection has been presented. Furthermore, it delves into the specific domain of MNP-based biosensors, assessing their potential impact on POCT. By combining existing research and spotlighting pivotal discoveries, this review enhances our comprehension of the advancements and promising prospects offered by MNP-based biosensors in the context of POCT. It seeks to facilitate informed decision-making among healthcare professionals and researchers while also promoting further exploration in this promising field of study.

A Magnetic-Optical Triple-Mode Lateral Flow Immunoassay for Sensitive and Rapid Detection of Respiratory Adenovirus

Human respiratory adenovirus (ADV) is a highly infectious respiratory virus with potential for pandemics. There are currently no specific drugs to treat ADV worldwide, so early rapid detection of ADV infection is essential. In this study, we developed an innovative magnetic-optical triple-mode lateral flow immunoassay (LFIA) using magnetic quantum dots as immunomarkers. This novel approach addresses the need for rapid and accurate ADV detection, allowing for multimodal quantitative/semiquantitative analysis of magnetic, fluorescent, and visible signals within a mere 15 min. The lower limit of detection (LOD) for magnetic, fluorescent, and visual signals was determined to be 5.6 × 103, 1.2 × 103, and 1.95 × 104 copies/mL, respectively. The detection range for ADV using this approach was 1.2 × 103-5 × 107 copies/mL. Additionally, semiquantitative analysis, which is user-friendly and does not necessitate specialized equipment, was successfully implemented. Notably, seven respiratory viruses showed no cross-reactivity with the generated LFIA test strips. The intrabatch repeatability exhibited a coefficient of variation (CV) of less than 5%, while the interbatch repeatability had a CV of less than 15%. Furthermore, recovery values ranged from 95% to 106.8% for samples analyzed concurrently with dual signals at the same spiking concentration. The assay developed in this study boasts a wide detection range and exceptional sensitivity and specificity. This technique is exceptionally well-suited for on-site rapid detection, with the potential for personal self-testing and early ADV infection diagnosis. Its versatility extends to a broad array of application scenarios.

One-step immunoassay of SARS-CoV-2 using screened Fv-antibodies and switching peptides

The Fv-antibodies were correponded to VH region of immunoglobulin G, which were composed of three complementarity determining regions (CDRs) for the specific binding of antigens. In this work, the Fv-antibodies against SARS-CoV-2 spike protein (SP) were screened from an autodisplayed Fv-antibody library which was expressed on E. coli outer membrane, and the receptor binding domain (RBD) of SP was used as a screening probe. The screened target clones were analyzed to have quantitative binding properties to the RBD, and the Fv-antibodies from the screened target clones were expressed as soluble proteins. The binding affinity (KD) of expressed Fv-antibodies to the RBD was estimated to be 70-85 nM using SPR biosensor. The specific binding properties of Fv-antibodies were analyzed for pseudo-virus particles with SARS-CoV-2 SP on the Lenti-virus envelope, such as wild type (Wuhan-1) and variants (Delta, Omicron BA.2, Omicron BA.4/5) using a SPR biosensor. The detection of real SARS-CoV-2 (Wild type, Wuhan-1) based on a SPR biosensor was also presented using the Fv-antibodies with the binding constant (KD) of cycle threshold value (Ct) = 33.8-32.9 (2.19-4.08 copies/μL) and LOD of 0.67-0.83 copies/μL (Ct = 35.5-35.2). Finally, one-step immunoassay based on switching peptide was demonstrated for the detection of the real SARS-CoV-2 (Wuhan-1) without any washing step. The binding constant (KD) was estimated to be Ct = 35.2-33.9 (0.83-2.04 copies/μL), and LOD was estimated to be 0.14-0.47 copies/μL (Ct = 37.8-36.0). Considering the LOD of the conventional RT-PCR (Ct = 35), the LOD of the one-step immunoassay based on the switching peptide was determined to be feasible for the medical diagnosis of COVID-19.

Biohybrid Nanoparticle-Based In Situ Monitoring of In Vivo Drug Delivery

Nanomaterials have gained huge attention worldwide owing to their unique physicochemical characteristics which enable their applications in the field of biomedicine and drug delivery systems. Although nanodrug delivery systems (NDDSs) have better target specificity and bioavailability than traditional drug delivery systems, their behavior and clearance mechanisms in living subjects remain unclear. In this regard, the importance of bioimaging methods has come to the forefront for investigating the biodistribution of nanocarriers and discovering drug release mechanisms in vivo. In this review, we introduce several examples of biohybrid nanoparticles and their clinical applications, focusing on their advantages and limitations. The various bioimaging methods for monitoring the fate of nanodrugs in biological systems and the future perspectives of NDDSs have also been discussed.

Recent Advances in Biosensor Development for the Detection of Viral Particles in Foods: A Comprehensive Review

Viral foodborne diseases cause serious harm to human health and the economy. Rapid, accurate, and convenient approaches for detecting foodborne viruses are crucial for preventing diseases. Biosensors integrating electrochemical and optical properties of nanomaterials have emerged as effective tools for the detection of viruses in foods. However, they still face several challenges, including substantial sample preparation and relatively poor sensitivity due to complex food matrices, which limit their field applications. Hence, the purpose of this review is to provide an overview of recent advances in biosensing techniques, including electrochemical, SERS-based, and colorimetric biosensors, for detecting viral particles in food samples, with emerging techniques for extraction/concentration of virus particles from food samples. Moreover, the principle, design, and advantages/disadvantages of each biosensing method are comprehensively described. This review covers the recent development of rapid and sensitive biosensors that can be used as new standards for monitoring food safety and food quality in the food industry.

Exploiting the Potential of Magnetic Nanoparticles for Rapid Diagnosis Tests (RDTs): Nanoparticle-Antibody Conjugates and Color Development Strategies

Magnetic nanoparticles (MNPs) have emerged as a promising material in disease diagnostics due to their potential to enhance detection sensitivity, facilitate concentration and purification of target substances in diverse samples, and enable favorable color-based detection. In this study, antibody-conjugated MNPs were successfully synthesized and validated through two appropriate methods: the measurement of MNPs' size and the use of phosphatase methods. Additionally, three methods were suggested and implemented for developing color in MNPs-based immunoassay, including the formation of MNP aggregations, utilization of MNPs' peroxidase-like activity, and synthesis of dually-conjugated MNPs with both enzyme and antibody. In particular, color development utilizing nanoparticle aggregations was demonstrated to result in a more yellowish color as virus concentration increased, while the peroxidase activity of MNPs exhibited a proportional increase in color intensity as the MNP concentration increased. This observation suggests the potential applicability of quantitative analysis using these methods. Furthermore, effective concentration and purification of target substances were demonstrated through the collection of MNPs using an external magnetic field, irrespective of factors such as antibody conjugation, dispersion medium, or virus binding. Finally, based on the key findings of this study, a design proposal for MNPs-based immunoassay is presented. Overall, MNPs-based immunoassays hold significant potential for advancing disease diagnostics.

Targeted and efficient delivery of rifampicin to macrophages involved in non-tuberculous mycobacterial infection via mannosylated solid lipid nanoparticles

Non-tuberculous mycobacterial infections are representative difficult-to-cure lung diseases with high incidence. Conventional treatments have several limitations such as negative side effects and increased drug resistance due to long-term administration. To overcome these limitations, there is a growing need for more stable drug delivery systems. Among the various drug delivery platforms developed thus far, solid lipid nanoparticles can be effectively loaded with hydrophobic substances and their physicochemical properties can be easily manipulated through surface modification, which makes them highly suitable drug delivery materials. Recent studies have reported the successful development of nanoparticles capable of selectively delivering drugs by targeting lectin-like receptors overexpressed on the surface of immune cells. Among these lectin-like receptors, the mannose receptor is a promising target because it is expressed on the surface of macrophages and is involved in immune activity. This study sought to synthesize rifampicin-loaded mannose surface-modified solid lipid nanoparticles (Man-RIF SLNs). The Man-RIF SLN synthesis process was first optimized, after which the characteristics of the synthesized particles were analyzed using dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and transmission electron microscopy (TEM). The surface modification with mannose was confirmed through FT-IR analysis. More importantly, the synthesized Man-RIF SLNs exhibited antibacterial and anti-biofilm properties against Mycobacterium intracellulare, a causative agent of non-tuberculous lung disease. Therefore, this study demonstrated that mannose receptor-targeted rifampicin delivery through solid lipid nanoparticles can be effectively applied to the treatment of non-tuberculous lung disease. Moreover, Man-RIF SLNs could also be used for the targeted delivery of drugs to several types of carcinoma cells or immune cells, as well as to treat lung diseases.

Molecular test for COVID-19 diagnosis based on a colorimetric genomagnetic assay

The world is in a long pandemic period caused by the SARS-CoV-2 virus and massive diagnostic tests to assist efforts to control the spread of the disease and also to avoid new coronavirus variants are still needed. Herein, we propose a simple and accurate saliva-based colorimetric test for the diagnosis of COVID-19. Magnetic beads (MBs) modified with a sequence of single-strand DNA (ssDNA) complementary to the N gene of the SARS-CoV-2 RNA were developed and used for magnetic capture and separation from a complex saliva sample. A second biotinylated ssDNA sequence was applied, and the colorimetric detection was carried out by adding streptavidin-horseradish peroxidase conjugate, H₂O_2, and tetramethylbenzidine (TMB) as chromogenic substrate. The test does not require viral RNA isolation, transcription, or amplification steps and can be performed at room temperature. The molecular assay test can be run using 96-well microplates, allowing the diagnosis of a large number of samples in 90 min. A simple support for magnets was designed and constructed using a 3D printer that allows the magnetic separations directly in the 96-well microplate. The colorimetric test showed an excellent ability to discriminate between healthy individuals and patients infected with SARS-CoV-2, with 92% and 100% of clinical sensitivity and specificity, respectively. This performance was similar to that achieved using the gold standard RT-PCR technique. The proposed genomagnetic assay offers an opportunity to greatly increase population testing, contribute to controlling the spread of the virus, and improve health equity in testing for COVID-19.

Lipid-based colloidal nanoparticles for applications in targeted vaccine delivery

Bioactive molecules and their effects have been influenced by their solubility and administration route. In many therapeutic reagents, the performance of therapeutics is dependent on physiological barriers in the human body and delivery efficacy. Therefore, an effective and stable therapeutic delivery promotes pharmaceutical advancement and suitable biological usage of drugs. In the biological and pharmacological industries, lipid nanoparticles (LNPs) have emerged as a potential carrier to deliver therapeutics. Since studies reported doxorubicin-loaded liposomes (Doxil®), LNPs have been applied to numerous clinical trials. Lipid-based nanoparticles, including liposomes, solid lipid nanoparticles (SLNs), and nanostructured lipid nanoparticles, have also been developed to deliver active ingredients in vaccines. In this review, we present the type of LNPs used to develop vaccines with attractive advantages. We then discuss messenger RNA (mRNA) delivery for the clinical application of mRNA therapeutic-loaded LNPs and recent research trend of LNP-based vaccine development.

A vertically paired electrode for redox cycling and its application to immunoassays

An electrochemical immunoassay based on the redox cycling method was presented using vertically paired electrodes (VPEs), which were fabricated using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as an electrode material and parylene-C as a dielectric layer. For the application to immunoassays, different electrochemical properties of PEDOT:PSS were analyzed for the redox reaction of 3,3',5,5'-tetramethylbenzidine (TMB, the chromogenic substrate for enzyme-immunoassays) at different pH conditions, including the conductivity (σ), electron transfer rate constant (k_app), and double-layer capacitance (C_dl). The influencing factors on the sensitivity of redox cycling based on VPE based on PEDOT:PSS were analyzed for the redox reaction of TMB, such as the electrode gap and number of electrode pairs. Computer simulation was also performed for the redox cycling results based on VPEs, which had limitations in fabrication, such as VPEs with an electrode gap of less than 100 nm and more than five electrode pairs. Finally, the redox cycling based on VPE was applied to the medical diagnosis of human hepatitis-C virus (hHCV) using a commercial ELISA kit. The sensitivity of the redox cycling method for the medical diagnosis of hHCV was compared with conventional assay methods, such as TMB-based chromogenic detection, luminol-based chemiluminescence assay, and a rapid test kit (lateral flow immunoassay).

Multifunctional Nanoparticle Platform for Surface Accumulative Nucleic Acid Amplification and Rapid Electrochemical Detection: An Application to Pathogenic Coronavirus

Of various molecular diagnostic assays, the real-time reverse transcription polymerase chain reaction is considered the gold standard for infection diagnosis, despite critical drawbacks that limit rapid detection and accessibility. To confront these issues, several nanoparticle-based molecular detection methods have been developed to a great extent, but still possess several challenges. In this study, a novel nucleic acid amplification method termed nanoparticle-based surface localized amplification (nSLAM) is paired with electrochemical detection (ECD) to develop a nucleic acid biosensor platform that overcomes these limitations. The system uses primer-functionalized Fe3O4-Au core-shell nanoparticles for nucleic acid amplification, which promotes the production of amplicons that accumulate on the nanoparticle surfaces, inducing significantly amplified currents during ECD that identify the presence of target genetic material. The platform, applying to the COVID-19 model, demonstrates an exceptional sensitivity of ∼1 copy/μL for 35 cycles of amplification, enabling the reduction of amplification cycles to 4 cycles (∼7 min runtime) using 1 fM complementary DNA. The nSLAM acts as an accelerator that actively promotes and participates in the nucleic acid amplification process through direct polymerization and binding of amplicons on the nanoparticle surfaces. This ultrasensitive fast-response system is a promising method for detecting emerging pathogens like the coronavirus and can be extended to detect a wider variety of biomolecules.

How to choose proper magnetic particles for bioaffinity interactions? The case for immobilised glyconanoconjugate

In this study, an assay for detection of the cancer biomarker Thomsen-nouvelle (Tn) antigen on the ELISA plates format was designed and developed. The effects of size and the interfacial density of the negative charge of magnetic beads (MBs) on the specific sensitivity of the bioaffinity interaction were studied. In particular, glyconanoconjugate, i.e. glycan Tn antigen conjugated to bovine serum albumin (BSA) was covalently immobilised on MBs for the bioaffinity detection of anti-Tn antibodies as cancer biomarkers. Six different MBs were used in the study, i.e. carboxy-modified MBs of 250 nm, 500 nm, 1000 nm and 2800 nm and epoxy-modified MBs of 2800 nm and 4500 nm. In order to evaluate which MBs are the best suited for detection of the analyte anti-Tn antibodies, sensitivities of detection (slopes from calibration curves) were calculated. Next, specific sensitivities were calculated for each type of MBs as a ratio of sensitivity of detection to the mass of MBs. From zeta potential ζ for each type of MBs, the interfacial charge density on MBs was calculated, expressed as the density of zeta potential ζ_d (ratio of zeta potential to surface area of MBs, i.e. ζ_d = ζ/A). Then, we evaluated the effect of size and ζ_d on the specific sensitivity of detection of anti-Tn antibodies in order to understand the immobilisation process on nanoscale. We also identified an optimal value of ζ_d on MBs; this was essential to achieve highly sensitive detection of the analyte, which made it possible to attain limit of detection (LOD) of (0.31 ± 0.01) ng mL^-1 or (2.10 ± 0.04) pM for analyte detection. In addition, the optimal assay configuration was highly selective and enabled reliable detection of the analyte in human serum with a recovery index in the range of 102-104%.