Isolation Capability Research Articles

A peptide targeting outer membrane protein A of Acinetobacter baumannii exhibits antibacterial activity by reducing bacterial pathogenicity.

The World Health Organization has classified multidrug-resistant (MDR) Acinetobacter baumannii as a significant threat to human health, necessitating the urgent discovery of new antibacterial drugs to combat bacterial resistance. Outer membrane protein A of A. baumannii (AbOmpA) is an outer membrane-anchored β-barrel-shaped pore protein that plays a critical role in bacterial adhesion, invasion, and biofilm formation. Therefore, AbOmpA is considered a key virulence factor of A. baumannii. Herein, we screened three phage display peptide libraries targeting AbOmpA and identified several peptides. Among them, P92 (amino acid sequence: QMGFMTSPKHSV) exhibited the highest binding affinity with AbOmpA, with a KD value of 7.84 nM. In vitro studies demonstrated that although P92 did not directly inhibit bacterial growth, it significantly reduced the invasion and adhesion capabilities of multiple clinical isolates of MDR A. baumannii and concentration-dependently inhibited biofilm formation by acting on OmpA. Furthermore, the polymerase chain reaction results confirmed a significant positive correlation between the antibacterial effect of P92 and OmpA expression levels. Encouragingly, P92 also displayed remarkable therapeutic efficacy against A. baumannii infection in various models, including an in vitro cell infection model, a mouse skin infection model, and a mouse sepsis model. These results highlight P92 as a novel and highly effective antimicrobial molecule specifically targeting the virulence factor AbOmpA.

Facile synthesis of active sites-rich magnetic adsorbent by simple one-pot hydrothermal strategy for quick and highly capable capture of female-steroid hormones

Rapid and efficient extraction is highly desired in the accurate quantification of female-steroid hormones (FSHs) in complex samples. In this context, an active sites-rich magnetic adsorbent (MAC) modified with carboxylated multiwalled carbon nanotubes and 4-vinylphenylboronic acid was facilely synthesized through one-pot hydrothermal technique for the magnetic solid phase extraction (MSPE) of FSHs in water and urine samples. Various characterizations revealed that the prepared adsorbent contained abundant functional groups, acceptable magnetic properties, high surface area and good stability. Due to the multiple interactions, the developed MAC/MSPE exhibited high isolation and preconcentration capability towards studied FSHs within 10 min. The concentration factors were 151–354 and the adsorption capacity was as high as 3.2 mg/g. Adsorption behaviors of MAC/MSPE towards FSHs were studied based on adsorption kinetics and isotherm experiments. After optimizing the extraction parameters, the MAC/MSPE was combined with HPLC to sensitive and reliable monitoring of studied FSHs in various waters and female urine samples. The limits of detection and recoveries with different spiked contents were 0.0015–0.0026 μg/L and 80.1–119 %, respectively. Accuracy of the established method was evaluated by confirmatory testing. Moreover, sample preparation greenness of the developed method was assessed. The present study uncovered the prospect of MAC/MSPE in the rapid and highly capable capture of FSHs, and also supplied a sensitive and reliable approach for the monitoring of trace FSHs in complex samples.

Soil Actinobacteria Exhibit Metabolic Capabilities for Degrading the Toxic and Persistent Herbicide Metribuzin.

Metribuzin, a widely used triazine herbicide, persists in agricultural soils and poses significant environmental pollution threats globally. The aim of this study was to investigate the biodegradation of metribuzin by actinobacterial strains in vitro at different environmental conditions. From an initial screen of 12 actinobacterial strains, four bacteria exhibited robust growth in the presence of the metribuzin as the sole carbon source at 50 mg/L concentration. The optimization of metribuzin biodegradation under different conditions (pH, temperature and inoculum size) using a spectrophotometric method revealed that maximum degradation of metribuzin occurred at a pH of 7.2, a temperature 30 °C, and at an inoculum volume of 4%. Subsequent GC-MS validation confirmed the remarkable biodegradation capabilities of the actinobacterial isolates, where the strain C1 showed the highest rate of metribuzin degradation of 83.12%. Detailed phylogenetic identified the active strains as Streptomyces toxytricini (CH), Streptomyces stelliscabiei (B2), and two Streptomyces heliomycini (C1, C3). Structural analysis by ATR-FTIR spectroscopy confirmed the extensive biotransformation of the herbicide molecule. Our findings highlight the immense untapped potential of soil actinobacteria, particularly the Streptomyces heliomycini C1 strain, as versatile bioremediation agents for removing persistent agrochemical pollutants.

The efficacy of some endophytic fungi against primary grapevine black foot disease pathogens

ABSTRACT Black foot disease (BFD), primarily attributed to taxa within the genera Dactylonectria and Ilyonectria, is a significant problem that causes serious damage worldwide in many grape and wine regions. This threat could especially be destructive in nurseries and early-stage vineyards, where it induces a decline in growth along with drying, leading to a reduction in the quality and lifespan of the grapevines. This research mainly focused on assessing the biocontrol capabilities of endophytic isolates derived from grapevine saplings, specifically Acremonium sclerotigenum and Clonostachys rosea. The study aimed to assess their effectiveness against the major pathogens responsible for BFD, including Dactylonectria macrodidyma, D. torresensis, and I. liriodendri, under laboratory and in vivo conditions. In the conducted paired culture assays, Trichoderma harzianum KRL-AG2 was employed for comparative purposes. On the 28th day of antagonistic tests, the inhibition response of A. sclerotigenum (≥94%) and C. rosea (>90%) isolates against the three species of BFD, D. macrodidyma, D. torresensis, and I. liriodendri, reached the maximum inhibition rate. Based on the in vivo analysis conducted with 1103 P rootstocks, T. harzianum, A. sclerotigenum, and C. rosea isolates significantly reduced the disease severity and supplied notable positive effects on plant growth parameters, including root dry weight, root length, and shoot dry weight. These results suggest that these biocontrol agents have potential for the biological management of BFD.

Beyond Harmful: Exploring Biofilm Formation by Enterococci Isolated from Portuguese Traditional Cheeses.

This study investigated the biofilm-forming capabilities of Enterococcus isolates from Portuguese traditional cheeses with protected designation of origin (PDO) status, specifically Azeitão and Nisa. Given the absence of added starter cultures in the cheesemaking process, the characteristics of these cheeses are intrinsically linked to the autochthonous microbiota present in the raw materials and the production environment. Our findings demonstrate that all isolates possess biofilm production abilities, which are crucial for their colonization and persistence within cheese factories, thereby maintaining factory-specific microbial heritage. Through an integrated analysis utilizing principal component analysis (PCA), a direct correlation between biofilm formation and cell viability was established. Notably, these results underscore the adaptive capacity of enterococci to survive environmental fluctuations and their role in the unique characteristics of Portuguese traditional cheeses. Overall, this research enhances our understanding of the microbial dynamics in cheese production and highlights the importance of enterococci in preserving cheese quality and heritage.

Minimizing conduction losses in multiple active bridge converters across wide voltage ranges using advanced dual‐duty modulation

AbstractMultiple port DC/DC converters have applications in many fields: hybrid energy storage systems where batteries are combined with supercapacitors, multi‐level and multi‐modular inverters that need multiple DC sources, and DC microgrids. Among these converters, the Multiple Active Bridge (MAB) is particularly attractive due to its high power ratings and galvanic isolation capabilities. This paper introduces an advanced dual‐duty modulation technique for MAB converters designed to significantly reduce conduction losses over a wide range of input voltages by minimizing the harmonics’ reactive power on the AC stage. Consequently, it can improve the converter's efficiency when dealing with non‐constant voltage sources such as batteries and supercapacitors. The overall control technique is based on the dq‐frame control method under the first harmonic approach (FHA). This method is verified through simulations and implemented in a 1000 W triple‐port prototype. In the simulation, conductive and switching losses are modelled, and the trade‐off between these loss types is discussed. The experimental results affirm an overall improvement in efficiency for certain scenarios involving non‐unit voltage conversion ratios.

Perioperative Anesthetic Considerations for Catheter-Based Pulmonary Vein Interventions in Fibrosing Mediastinitis

IntroductionFibrosing mediastinitis is a rare disease characterized by abnormal proliferation of fibrous tissue, causing compression, and narrowing of the airway, blood vessels and other mediastinal structures, including the pulmonary veins. Catheter based interventions are available palliative strategies. Due to the complex nature of the disease and the profound respiratory and hemodynamic sequela that may ensue, anesthetic management requires meticulous interdisciplinary planning. MethodsWe performed a retrospective descriptive study including patients with Fibrosing Mediastinitis undergoing catheter-based interventions for pulmonary vein stenosis from January 2020 to April 2024. A total of fourteen patients underwent chart review and we reported patient sex, preprocedural pulmonary artery pressures, comorbidities, lung isolation strategies, intra-procedural anesthestic complications, post procedural ICU admissions and length of stayResults: All patients underwent pulmonary vasculature angioplasty, with or without stent placement, under general anesthesia with lung isolation capabilities and echocardiogram guidance. 11 of 18 (61%) cases were uncomplicated. 4 of 18 (22%) required unanticipated postoperative ICU care, 2 (11%) in the setting of pulmonary hemorrhage, one due to hypoxic respiratory failure, and one due to difficult airway. One patient developed self-limiting postoperative hemoptysis in two different occasions and one patient developed a vascular access related complication. Mean hospital length of stay (LOS) was 2.6 days (0-13 days) and mean ICU LOS was 1.75 days (1-4 days). One patient presented 6-weeks postoperatively with massive hemoptysis likely secondary to PV rupture and passed away following a protracted ICU course. ConclusionPatients with FM can achieve successful intraprocedural outcomes by ensuring a comprehensive understanding of the disease, addressing significant anesthetic concerns and considerations, and engaging a multi-disciplinary team.

Hybrid vibration isolator based on piezoelectric actuator and metal rubber and its adaptive control method

To achieve vibration isolation across the entire working frequency range, this paper proposes a novel hybrid vibration isolator combining metal rubber and piezoelectric actuators, along with an adaptive active control algorithm. The passive isolation system allows for manual adjustment of stiffness and damping based on the preload, overcoming the issue of fixed stiffness and damping in traditional passive isolation units. For the active isolation system, an improved Filtered-x Normalized Least Mean Squares with adaptive step size active control algorithm is proposed, overcoming the problem of narrow frequency range applicability in traditional active control algorithms. A hybrid model of electromechanical coupling and hysteresis for the piezoelectric actuator is developed for the secondary path in the algorithm. Experimental results confirm that the hybrid isolator possesses vibration isolation capabilities within the 5–500 Hz working frequency range, with vibration suppression at the first and second resonance frequencies improved by 98.9% and 92.2%, respectively, compared to the passive system. Additionally, the hybrid isolator effectively suppresses complex multifrequency signals and demonstrates robustness and adaptability. This research provides advanced technological means to address complex vibration problems, and establishes both theoretical and practical foundations for multi-degree-of-freedom vibration isolation.

High-Level Isolation: A Landscape Analysis of Global Capabilities and Opportunities to Advance the Field.

High-level isolation units (HLIUs) have been established by countries to provide safe and optimal medical care for patients with high-consequence infectious diseases. We aimed to identify global high-level isolation capabilities and determine gaps and priorities of global HLIUs, using a multiple method approach that included a systematic review of published and gray literature and a review of Joint External Evaluations and Global Health Security Index reports from 112 countries. A follow-up electronic survey was distributed to identified HLIUs. The landscape analysis found 44 previously designated/self-described HLIUs in 19 countries. An additional 33 countries had potential HLIUs; however, there were not enough details on capabilities to determine if they fit the HLIU definition. An electronic survey was distributed to 36 HLIUs to validate landscape analysis findings and to understand challenges, best practices, and priorities for increased networking with a global HLIU cohort; 31 (86%) HLIUs responded. Responses revealed an additional 30 confirmed HLIUs that were not identified in the landscape analysis. To our knowledge, this was the first mapping and the largest ever survey of global HLIUs. Survey findings identified major gaps in visibility of HLIUs: while our landscape analysis initially identified 44 units, the survey unveiled an additional 30 HLIUs that had not been previously identified or confirmed. The lack of formalized regional or global coordinating organizations exacerbates these visibility gaps. The unique characteristics and capabilities of these facilities, coupled with the likelihood these units serve as core components of national health security plans, provides an opportunity for increased connection and networking to advance the field of high-level isolation and address identified gaps in coordination, build an evidence base for HLIU approaches, and inform HLIU definitions and key components.

Natural mechanism of superexcellent vibration isolation of the chicken neck

No matter how the chicken's body shakes, its head can always remain relatively motionless, leading to the intuitive impression that the S-configuration of the chicken neck possesses an unparalleled vibration isolation capability. However, this viewpoint has not been rigorously substantiated. To unravel the vibration isolation mechanism inherent in the chicken neck, this study introduces a multi-modular S-configurational model inspired by its biological structure. Utilizing Newton's law and Lagrange's equations, both the static and dynamic models for the S-configurational model are formulated. Furthermore, we incorporate actuators into the model and develop a bionic attitude control method. Surprisingly, numerical simulations reveal that the S-configuration of the chicken neck does not exhibit any passive vibration isolation function, challenging the intuitive impression. Instead, the motionless of a chicken head results from active control implemented by the corresponding chicken neck. This study may contribute to a better understanding of the vibration attenuation function of the neck of birds.

Biofilm Formation and Antibiotic Resistance Profiles in Carbapenemase-Producing Gram-Negative Rods-A Comparative Analysis between Screening and Pathological Isolates.

(1) Background: Carbapenem-resistant (CR) bacteria pose a significant global public health challenge due to their ability to evade treatment with beta-lactam antibiotics, including carbapenems. This study investigates the biofilm-forming capabilities of CR clinical bacterial isolates and examines the impact of serum on biofilm formation. Additionally, the study evaluates the resistance profiles and genetic markers for carbapenemase production. (2) Methods: Bacterial isolates were collected from the microbiology laboratory of Mures County Clinical Hospital between October 2022 and September 2023. Pharyngeal and rectal swabs were screened for carbapenem-resistant bacteria using selective media. Lower respiratory tract samples were also analyzed for CR Gram-negative bacteria. The isolates were tested for their ability to form biofilms in the presence and absence of fetal bovine serum at 24 and 48 h. Carbapenemase production was detected phenotypically and confirmed via PCR for relevant genes. (3) Results: Out of 846 screened samples, 4.25% from pharyngeal swabs and 6.38% from rectal swabs tested positive for CR bacteria. Acinetobacter baumannii and Klebsiella pneumoniae were the most common species isolated. Biofilm formation varied significantly between clinical isolates and standard strains, with clinical isolates generally showing higher biofilm production. The presence of serum had no significant effect on biofilm formation in Klebsiella spp., but stimulated biofilm formation for Acinetobacter spp. Carbapenemase genes blaKPC, blaOXA-48-like, and blaNDM were detected in various isolates, predominantly in Klebsiella spp., but were not the main determinants of carbapenem resistance, at least in screening isolates. (4) Conclusions: This study highlights the variability in biofilm formation among CR clinical isolates and underscores the differences between the bacteria found as carriage versus infection. Both bacterial species and environmental factors variably influence biofilm formation. These insights are crucial for the development of effective treatment and infection control strategies in clinical settings.

Stair‐Stepping Mechanical Metamaterials with Programmable Load Plateaus

AbstractMaterials with target load plateaus offer the potential for developing innovative vibration suppression and isolation systems for applications such as satellite platforms, submarines, and electric vehicles. However, implementing these materials can pose significant challenges. In this study, stair‐stepping mechanical metamaterials with programmable load plateaus are presented, which are created via a three‐level (unit, module, and 3D object) construction strategy. The strategy inspired by the inverse design concept achieves tunability in the number and properties of load plateaus within the force–displacement profiles of the metamaterials. This approach even yields appealing stair‐stepping response patterns, as validated by experiments and finite element simulations. Promisingly, programming the unit from its initial configuration to a “zero stiffness” configuration enables these metamaterials excellent vibration isolation performance. Furthermore, two reversible methods are proposed for switching among various unit configurations, namely shape memory programming and supporting payload. This innovative design strategy for programmable load plateaus opens up new possibilities for creating metamaterials with customized force–displacement responses. It also provides opportunities to incorporate multimodal vibration isolation capabilities into precision devices.

Some virulence genes and biofilm formation capabilities of Listeria monocytogenes isolates from different sources

In this study, it was aimed to determine the biofilm-forming abilities of both clinical and food-borne isolates of Listeria monocytogenes, to investigate the presence of nine different virulence genes, and to consider the current threat status of this agent. A total of 28 isolates, 21 from food and seven from clinical origin, were used in the study. To determine the biofilm formation abilities of isolates, two different methods namely “tube adherence” and “microplate” were used respectively. For the determination of nine different virulence genes of Listeria monocytogenes (inlA, inlC, inlJ, hylA, luxS, flaA, prfA, inlB, actA), the method of polymerase chain reaction (PCR) was used. As a result, all isolates were found to be able to form a biofilm to varying degrees by both tube and microplate methods. These two methods were similar in terms of their results. All nine different virulence gene regions were detected at various rates in the isolates. Whereas the genes directly related to biofilm formation for the isolates weren't detected, to form biofilm was observed. The virulence genes detected in clinical origin isolates were proportionally higher than in food-borne isolates (except for flaA and prfA gene regions). It was concluded that bacteria of Listeria monocytogenes continue to form biofilm and carry virulence genes regardless they are from food or clinical origin. Also, food-borne contaminations continue to be a severe threat to human health. So, to prevent listeriosis cases of both humans and animals should be taken required precautions and all cases should be considered carefully.

Topology optimization of programable quasi-zero-stiffness metastructures for low-frequency vibration isolation

Quasi-zero-stiffness (QZS) isolators have been demonstrated to realize low-frequency vibration isolation without loss of static stiffness. However, most previous designs are based on spring-driven links, cam-roller structures, or two-phased network structures resorting to complex assembling components, other than compact and integrative single-phased solid structures. In this paper, we propose a topology optimization scheme to inversely design QZS metastructures with smooth boundaries for customized nonlinear force-displacement curves. The optimization model is established based on the distinguishing features of the QZS force-displacement curve. The boundary smoothing procedure is introduced in the genetic algorithm to improve the convergence and stability of topology optimization. The designed metastructures are verified to have robust QZS feature. A linear relationship between the platform force and the initial modulus of the base material is obtained. We numerically show the high-static-low-dynamic performance, the load bearing, and even full band vibration isolation capabilities of the designed QZS metastructures. In addition, experiments are performed to verify the QZS feature of the designed metastructure. The inverse design scheme developed in this paper can efficiently design QZS isolators suitable for different scenarios with great flexibility. The metastructures with smooth boundaries are obtained so that postprocessing is not required before manufacture. The proposed inverse-design methodology paves the way for low-frequency vibration isolation using compact solid structures without any positive or negative stiffness units.

Providing spatial isolation for Mixed-Criticality Systems

Hard real-time systems, characterized by stringent timeliness requirements, occur in an increasing variety of industrial sectors. Some such domains carry important safety-critical concerns, notably avionics, space, and automotive. One common design trend across those domains seeks to reduce the number of computing devices embedded in them by integrating software applications of different criticality levels into one and the same onboard computer. A safety-savvy design approach however requires isolation among components of different criticality, to prevent unintended reciprocal interference across them. Isolation is traditionally achieved through partitioning. Partitioning, however, incurs low resource utilization as cautionary margins are used to inflate partition budgets over their anticipated needs. This situation has prompted research into alternative ways to integration that can safely afford higher levels of utilization. The Mixed-Criticality (MC) approach, which concentrates on the CPU scheduling problem, has yielded a large body of research results that show considerable gains in sustained utilization, but it has yet to meet all of the isolation requirements of safety-critical systems. This work presents a solution to augment a state-of-the-art MC solution with efficient and effective spatial isolation capabilities. Experimental results show that our solution provides adequate guarantees of temporal and spatial isolation with very small runtime overhead.

A four-port self-multiplexing tunable graphene based dielectric resonator antenna with defective ground structure for high isolation and MIMO capabilities

Objectives and designA novel self-multiplexing terahertz antenna with four tunable ports is proposed in this work. The configuration comprises four rectangular dielectric resonators (DRs) affixed to a substrate, which are excited through L-shaped microstrip-fed slots positioned beneath them. To guarantee efficient isolation among the tunable antenna components, periodic unit cells are introduced into the ground plane, forming a defective ground structure (DGS). Each L-shaped slot element is equipped with a graphene strip to regulate the tunability of each DR element. Results and applicationsThis antenna can operate in various modes with resonant frequencies at 4.01, 4.23, 4.37, and 4.57 THz. It holds potential for future terahertz wireless applications that require the utilization of adjacent channels with distinct communication frequencies. Furthermore, a four-port antenna design is implemented, offering tunable MIMO capabilities with self-quadruplexing ability. The MIMO parameters, specifically the envelope correlation coefficient (ECC) and diversity gain (DG), have been assessed and found to fall within acceptable limits across the operating frequency bands. Additionally, an equivalent circuit model (ECM) is analysed to shed light on the antenna's working principle and verify the obtained results.

Full-scale laboratory investigation on laminated rubber bearings for metro-induced vibration mitigation

The vibration response generated by the operation of a metro system has a profound impact on the physical and mental well-being of urban residents. Vibration control is essential to effectively isolate the multi-band vibration response and structure-borne noise of buildings. Laminated rubber bearings between the foundation and the superstructures serve as a common, cost-effective solution for the seismic isolation of structures and have great potential to be used for metro-induced vibration mitigation. In this study, two types of full-scale laminated rubber bearings (i.e., linear natural rubber bearing and lead rubber bearing) were tested under various compressive stresses, ranging from 5 MPa to 15 MPa, to examine the static and dynamic characteristics of the bearings, including vertical hysteresis curves, vertical static stiffness, time history response, and frequency spectrum. Then, the numerical simulation of a base-isolated building structure equipped with laminated rubber bearings was conducted to evaluate the vertical vibration isolation performance and structure-borne noise isolation capability. It was demonstrated that the laminated rubber bearings have stable vertical bearing capacities and performance in isolating vertical vibrations.

Molecular and aflatoxigenicity analyses of Aspergillus flavus isolates indigenous to grain corn in Malaysia; potentials for biological control.

The present work aimed to distinguish the indigenous Aspergillus flavus isolates obtained from the first (pioneer) grain corn farms in Terengganu, Malaysia, into aflatoxigenic and non-aflatoxigenic by molecular and aflatoxigenicity analyses, and determine the antagonistic capability of the non-aflatoxigenic isolates against aflatoxigenic counterparts and their aflatoxin production in vitro. Seven A. flavus isolates previously obtained from the farms were characterized molecularly and chemically. All isolates were examined for the presence of seven aflatoxin biosynthesis genes, and their aflatoxigenicity were confirmed using high performance liquid chromatography with fluorescence detector (HPLC-FLD). Phylogenetic relationships of all isolates were tested using ITS and β-tubulin genes. Of the seven isolates, two were non-aflatoxigenic, while the remaining were aflatoxigenic based on the presence of all aflatoxin biosynthesis genes tested, and the productions of aflatoxins B1 and B2. All isolates were also confirmed as A. flavus following phylogenetic analysis. The indigenous non-aflatoxigenic isolates were further examined for their antagonistic potential against aflatoxigenic isolates on 3% grain corn agar (GCA). Both non-aflatoxigenic isolates significantly reduced AFB1 production of the aflatoxigenic isolates. The indigenous non-aflatoxigenic A. flavus strains identified in the present work were effective in controlling the aflatoxin production by the aflatoxigenic A. flavus isolates in vitro and can be utilized for in situ testing.

Shake table tests on a rigid block isolated with high-damping unbonded fiber-reinforced elastomeric isolators

Fiber-reinforced elastomeric isolators (FREIs) represent a relatively recent type of elastomeric device. In contrast to traditional steel-reinforced elastomeric isolators (SREIs), FREIs are constructed with multiple layers of rubber pads and fiber layers instead of steel laminas. This choice is aimed at cost reduction during the manufacturing and installation process. To enhance cost-efficiency, FREIs can also be used in unbonded applications (UFREIs), where the device is placed between the foundation and the superstructure without bonding or fastening. This approach helps to further minimize installation expenses. Furthermore, the lateral rollover deformation, a characteristic feature of this configuration, improves energy dissipation. This study investigates the seismic isolation capabilities of high-damping unbonded FREIs for low-rise masonry buildings. Specifically, unidirectional cyclic and shake table tests of a rigid block isolated with two UFREIs are discussed. The primary goals of this experimental study include evaluating the effectiveness of UFREIs in reducing seismic demands, analyzing the response of UFREIs under unidirectional ground-motion excitation, confirming the ability of UFREIs to withstand major unidirectional excitation without sustaining damage, and exploring the limitations of this isolation system under a range of seismic inputs and low axial loads.

Distinguishable Magnetic Reporter Coordination with Buoyancy-Magnetism Separation for Immobilization-Free Dual-Target Electrochemical Immunosensing.

Simultaneous sensitive and precise determination of multibiomarkers is of great significance for improving detection efficiency, reducing diagnosis and treatment expenses, and elevating survival rates. However, the development of simple and portable biosensors for simultaneous determination of multiplexed targets in biological fluids still faces challenges. Herein, a unique and versatile immobilization-free dual-target electrochemical biosensing platform, which combines distinguishable magnetic signal reporters with buoyancy-magnetism separation, was designed and constructed for simultaneous detection of carcinoembryonic (CEA) and α-fetoprotein (AFP) in intricate biological fluids. To construct such distinguishable magnetic signal reporters with signal transduction, amplification, and output, secondary antibodies of CEA and AFP were respectively functionalized on methylene blue (MB) and 6-(ferrocenyl)hexanethiol (FeC) modified Fe3O4@Au magnetic nanocomposites. Meanwhile, a multifunctional flotation probe with dual target recognition, capture, and isolation capability was prepared by conjugating primary antibodies (Ab1-CEA, Ab1-AFP) to hollow buoyant microspheres. The target antigens of CEA and AFP can trigger a flotation-mediated sandwich-type immunoreaction and capture a certain amount of the distinguishable magnetic signal reporter, which enables the conversion of the target CEA and AFP quantities to the signal of the potential-resolved MB and FeC. Thus, the MB and FeC currents of magnetically adsorbed distinguishable magnetic reporters can be used to determine the CEA and AFP targets simultaneously and precisely. Accordingly, the proposed strategy exhibited a delightful linear response for CEA and AFP in the range of 100 fg·mL-1-100 ng·mL-1 with detection limits of 33.34 and 17.02 fg·mL-1 (S/N = 3), respectively. Meanwhile, no significant nonspecific adsorption and cross-talk were observed. The biosensing platform has shown satisfactory performance in the determination of real clinical samples. More importantly, the proposed approach can be conveniently extended to universal detection just by simply substituting biorecognition events. Thus, this work opens up a new promising perspective for dual and even multiple targets and offers promising potential applications in clinical diagnosis.