Magnetoelastic Immunosensor via Antibody Immobilization for the Specific Detection of Lysozymes

Ratiometric fluorescence aptasensor for lysozyme based on the controllable excimer formation of perylene probe

As an important biological indicator, the abnormity of the lysozyme level is closely related to many diseases. Herein, we devise a novel ratiometric fluorescence aptasensor for lysozyme based on the controllable excimer formation of a perylene probe, N, N'-bis(6-caproic acid)-3,4:9,10-perylene diimide (PDI) induced by cationic silver nanoparticles (Ag NPs). Binding of lysozyme aptamer with multiple phosphate groups to cationic Ag NPs strongly hinders the formation of excimer, yielding intense monomer fluorescence of PDI probe. With the introduction of lysozyme, the adsorption of aptamer on the surface of Ag NPs will be weakened owing to the specific interactions between aptamer and lysozyme, which greatly facilitates the excimer formation of PDI. Based on the monomer-excimer transition triggered by lysozyme, ratiometric fluorescence aptasensor for lysozyme can be established. A good linear relationship between the ratio of monomer intensity to excimer intensity and the logarithm of lysozyme concentration was obtained in the range of 0.25-15 nM, and as few as 0.25 nM lysozyme could be easily detected. Moreover, excellent selectivity for lysozyme detection and satisfactory results in real sample analysis were also achieved. This work provides an innovative platform for the construction of simple, label-free ratiometric fluorescence sensors towards a wide range of analytes based on perylene probe.

An Amplitude Analysis-Based Magnetoelastic Biosensing Method for Quantifying Blood Coagulation

Blood coagulation tests are crucial in the clinical management of cardiovascular diseases and preoperative diagnostics. However, the widespread adoption of existing detection devices, such as thromboelastography (TEG) instruments, is hindered by their bulky size, prohibitive cost, and lengthy detection times. In contrast, magnetoelastic sensors, known for their low cost and rapid response, have garnered attention for their potential application in various coagulation tests. These sensors function by detecting resonant frequency shifts in response to changes in blood viscosity during coagulation. Nevertheless, the frequency-based detection approach necessitates continuous and precise frequency scanning, imposing stringent demands on equipment design, processing, and analytical techniques. In contrast, amplitude-based detection methods offer superior applicability in many sensing scenarios. This paper presents a comprehensive study on signal acquisition from magnetoelastic sensors. We elucidate the mathematical relationship between the resonant amplitude of the response signal and liquid viscosity, propose a quantitative viscosity measurement method based on the maximum amplitude of the signal, and construct a corresponding sensing device. The proposed method was validated using glycerol solutions, demonstrating a sensitivity of 13.83 V-1/Pa0.5s0.5Kg0.5m-1.5 and a detection limit of 0.0817 Pa0.5s0.5Kg0.5m-1.5. When applied to real-time monitoring of the coagulation process, the resulting coagulation curves and maximum amplitude (MA) parameters exhibited excellent consistency with standard TEG results (R2 values of 0.9552 and 0.9615, respectively). Additionally, other TEG parameters, such as R-time, K-time, and α-angle, were successfully obtained, effectively reflecting viscosity changes during blood coagulation.

A smartphone-based multichannel magnetoelastic immunosensor for acute aortic dissection supplementary diagnosis

Some biomarkers of acute aortic dissection (AAD) can be used for the potential supplementary diagnosis of AAD, such as C-reactive protein (CRP), smooth muscle myosin heavy chain (SmMHC), and D-dimer (D-D). However, the current measurement methods for common markers primarily rely on sophisticated instruments. The operation process is complicated, and the reagents used are expensive. To provide chronic disease monitoring and home self-examination services for potential AAD patients in real time, we developed a smartphone-based multichannel magnetoelastic (ME) immunosensing device to detect protein levels. Our immunosensor reduced the aforementioned restrictions and demonstrated excellent performance for the supplementary diagnosis of AAD. In this paper, we successfully combined the intelligent terminal with the hardware system to sample the resonance frequency shift (RFS) on the multichannel ME immunosensor. According to the target detection objects with their respective antibodies in the immune binding response, multiple experiments were conducted to detect multiple groups of samples, and we found that a CRP concentration, a SmMHC concentration, and a D-D concentration in the range of 0.1-100μg/mL, 1-4ng/mL, and 0.25-5μg/mL were linearly proportional to the RFS of the ME immunosensor, respectively. For CRP, SmMHC, and D-D, the sensitivities were 13.37Hz/μg∙mL-1, 155.19Hz/ng∙mL-1, and 332.72Hz/μg∙mL-1, respectively, and the detection limits were 2.634×10-3μg/mL, 1.155×10-2ng/mL, and 3.687×10-3μg/mL, respectively. The experiments demonstrated that the accuracy and stability of our device were comparable to those of the vector network analyzer (VNA, Calibration instrument).

Magnetoelastic Immunosensor for the Rapid Detection of SARS-CoV-2 in Bioaerosols

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a protein-coated, single-stranded RNA virus that parasitizes and infects primates, including humans. The current detection methods are mainly carried out using humans as a medium, such as a chest computed tomography (CT) examination, nucleic acid detection, antibody detection, and antigen detection. In addition, SARS-CoV-2 in bioaerosols is an important way of transmission and infection, which has attracted wide attention. In this paper, we simulate a sampling system of SARS-CoV-2 in bioaerosols and detect SARS-CoV-2 in bioaerosols by means of a magnetoelastic (ME) sensing device based on an Android intelligent terminal, which can directly detect SARS-CoV-2 in bioaerosols in a certain unit environment. This approach aims to achieve early detection and prevention. The experimental results show that the sampling system can successfully collect SARS-CoV-2 in bioaerosols. In the linear range of 5-20 ng/mL, the ME sensing detection system results closely match those of the calibration instrument (VNA), with goodness-of-fit values of 0.997 and 0.995, respectively. This work demonstrates that the ME sensing detection system proposed is stable, highly specific, real-time, rapid, and has certain reference values and feasibility.

Advanced applications in enzyme-induced electrospun nanofibers

Electrospun nanofibers, renowned for their high specific surface area, robust mechanical properties, and versatile chemical functionalities, offer a promising platform for enzyme immobilization. Over the past decade, significant strides have been made in developing enzyme-induced electrospun nanofibers (EIEN). This review systematically summarizes the advanced applications of EIEN which are fabricated using both non-specific immobilization methods including interfacial adsorption (direct adsorption, cross-linking, and covalent binding) and encapsulation, and specific immobilization techniques (coordination and affinity immobilization). Future research should prioritize optimizing immobilization techniques to achieve a balance between enzyme activity, stability, and cost-effectiveness, thereby facilitating the industrialization of EIEN. We elucidate the rationale behind various immobilization methods and their applications, such as wastewater treatment, biosensors, and biomedicine. We aim to provide guidelines for developing suitable EIEN immobilization techniques tailored to specific future applications.

A highly sensitive point-of-care detection platform for Salmonella typhimurium by integrating magnetic enrichment and fluorescent CsPbBr3@SiO2

A platform was designed based on Fe3O4 and CsPbBr3@SiO2 for integrated magnetic enrichment-fluorescence detection of Salmonella typhimurium, which significantly simplifies the detection process and enhances the working efficiency. Fe3O4 served as a magnetic enrichment unit for the capture of S. typhimurium. CsPbBr3@SiO2 was employed as a fluorescence-sensing unit for quantitative signal output, where SiO2 was introduced to strengthen the stability of CsPbBr3, improve its biomodificability, and prevent lead leakage. More importantly, the SiO2 shell shows neglectable absorption or scattering towards fluorescence, making the CsPbBr3@SiO2 exhibit a high quantum yield of 74.4%. After magnetic enrichment, the decreasing rate of the fluorescence emission intensity of the CsPbBr3@SiO2 supernatant at 527 nm under excitation light at UV 365 nm showed a strong linear correlation with S. typhimurium concentration of 1 × 102~1 × 108 CFU∙mL-1, and the limit of detection (LOD) reached 12.72 CFU∙mL-1. This platform has demonstrated outstanding stability, reproducibility, and resistance to interference, which provides an alternative for convenient and quantitative detection of S. typhimurium.

Superior Efficacy of Apathogenic Genotype I (V4) over Lentogenic Genotype II (LaSota) Live Vaccines against Newcastle Disease Virus Genotype VII.1.1 in Pathogen-Associated Molecular Pattern-H9N2 Vaccinated Broiler Chickens

A comparison of the efficacy of apathogenic genotype I (V4) and lentogenic genotype II (LaSota) strains of live Newcastle disease virus (NDV) vaccines was performed following vaccination with pathogen-associated molecular pattern (PAMP) H9N2 avian influenza vaccine and challenge with velogenic NDV genotype VII.1.1 (vNDV-VII.1.1). Eight groups (Gs) of day-old chicks were used (n = 25). Groups 1-4 received a single dose of PAMP-H9N2 subcutaneously, while Gs (1, 5) and (2, 6) received eye drops of V4 and LaSota, respectively, as two doses. All Gs, except for 4 and 8, were intramuscularly challenged with vNDV-VII.1.1 at 28 days of age. No signs were detected in Gs 1, 5, 4, and 8. The mortality rates were 0% in Gs 1, 4, 5, and 8; 40% in G2; 46.66% in G6; and 100% in Gs 3 and 7. Lesions were recorded as minimal in Gs 1 and 5, but mild to moderate in Gs 2 and 6. The lowest significant viral shedding was detected in Gs 1, 2, and 5. In conclusion, two successive vaccinations of broilers with a live V4 NDV vaccine provided higher protection against vNDV-VII.1.1 challenge than LaSota. PAMP-H9N2 with live NDV vaccines induced more protection than the live vaccine alone.

A cost-effective smartphone-based device for rapid C-reaction protein (CRP) detection using magnetoelastic immunosensor

C-Reaction protein (CRP) is a marker of nonspecific immunity for vital signs and wound assessment, and it can be used to diagnose infections in clinical medicine. However, measuring CRP level currently requires hospital-based instruments, high-cost reagents, and a complex process, all of which have limited its full capabilities for self-detection, a growing trend in modern medicine. In this study, we developed a novel smartphone-based device using advanced methods of magnetoelastic immunosensing to mitigate these limitations. We combined a system-on-chip (SoC) hardware architecture with smartphone apps to realize the sampling of resonance frequency shift on magnetoelastic chips, which can determine the ultra-sensitivity to mass change caused by the binding of anti-CRP antibody and CRP. Through detecting a multi-group of samples, we found that the resonance frequency shift was linearly proportional to the CRP concentration in the range from 0.1 to 100 μg mL^-1, with a sensitivity of 12.90 Hz μg^-1 mL^-1 and a detection limit of 2.349 × 10^-4 μg mL^-1. Meanwhile, compared with the large-scale instrument used in clinical settings, the performance of our device was stable and significantly more portable, rapid and cost-effective, offering excellent potential for modern home-based diagnosis.

Autodisplay of streptococcal protein G for construction of an orientation-controlled immunoaffinity layer

An immunoaffinity layer with orientation-controlled antibodies was constructed to express streptococcal protein G in Escherichia coli cells using autodisplay technology. The sequence of protein G, a specific IgG-binding protein, was inserted into the autodisplay vector using recombinant technology and the constructed plasmid vector was transformed into E. coli cells. Protein G was confirmed to be autodisplayed with a high density of 2 × 10⁵ copies per cell by SDS-PAGE analysis, and its IgG-binding affinity was confirmed by fluorescence microscopy. Autodisplayed protein G showed higher affinity than the IgG-binding Z-domain for goat IgG. Immunoassays based on E. coli cells were established to detect horseradish peroxidase (HRP) and C-reactive protein (CRP). Protein G autodisplaying E. coli cells were utilized as a solid support and immunoassays showed improved sensitivity by orientation control of autodisplayed protein G. The outer membrane (OM) of protein G autodisplaying E. coli was isolated and layered to construct an immunoaffinity layer. The OM was coated on a microplate to perform the immunoassays, which showed limits of detection of 5 and 0.2 ng mL^-1 for HRP and CRP, respectively. An OM layer with autodisplayed protein G was applied as the immunoaffinity layer of a surface plasmon resonance (SPR) biosensor. After CRP detection, the SPR responses showed good linearity, with an R² value of 0.99. The immunoaffinity layer with orientation control by autodisplayed protein G was confirmed to be applicable in immunoassays and immunosensors to improve sensitivity.

Multi-Factors Cooperatively Actuated Photonic Hydrogel Aptasensors for Facile, Label-Free and Colorimetric Detection of Lysozyme

Responsive two-dimensional photonic crystal (2DPC) hydrogels have been widely used as smart sensing materials for constructing various optical sensors to accurately detect different target analytes. Herein, we report photonic hydrogel aptasensors based on aptamer-functionalized 2DPC poly(acrylamide-acrylic acid-N-tert-butyl acrylamide) hydrogels for facile, label-free and colorimetric detection of lysozyme in human serum. The constructed photonic hydrogel aptasensors undergo shrinkage upon exposure to lysozyme solution through multi-factors cooperative actuation. Here, the specific binding between the aptamer and lysozyme, and the simultaneous interactions between carboxyl anions and N-tert-butyl groups with lysozyme, increase the cross-linking density of the hydrogel, leading to its shrinkage. The aptasensors’ shrinkage decreases the particle spacing of the 2DPC embedded in the hydrogel network. It can be simply monitored by measuring the Debye diffraction ring of the photonic hydrogel aptasensors using a laser pointer and a ruler without needing sophisticated apparatus. The significant shrinkage of the aptasensors can be observed by the naked eye via the hydrogel size and color change. The aptasensors show good sensitivity with a limit of detection of 1.8 nM, high selectivity and anti-interference for the detection of lysozyme. The photonic hydrogel aptasensors have been successfully used to accurately determine the concentration of lysozyme in human serum. Therefore, novel photonic hydrogel aptasensors can be constructed by designing functional monomers and aptamers that can specifically bind target analytes.

Magnetoelastic Resonance Sensors: Principles, Applications, and Perspectives

Magnetoelastic resonators are gaining attention as an incredibly versatile and sensitive transduction platform for the detection of varied physical, chemical, and biological parameters. These sensors, based on the coupling effect between mechanical and magnetic properties of ME platforms, stand out in comparison to alternative technologies due to their low cost and wireless detection capability. Several parameters have been optimized over the years to improve their performance, such as their composition, surface functionalization, or shape geometry. In this review, the working principles, recent advances, and future perspectives of magnetoelastic resonance transducers are introduced, highlighting their potentials as a versatile platform for sensing applications. First, the fundamental principles governing the magnetoelastic resonators performance are introduced as well as the most common magnetoelastic materials and their main fabrication methods are described. Second, the versatility and technical feasibility of magnetoelastic resonators for biological, chemical, and physical sensing are highlighted and the most recent results and functionalization processes are summarized. Finally, the forefront advances to further improve the performance of magnetoelastic resonators for sensing applications have been identified.