Ultrasensitive detection of anti-p53 autoantibodies based on nanomagnetic capture and separation with fluorescent sensing nanobioprobe for signal amplification

Acoustofluidics-enhanced biosensing with simultaneously high sensitivity and speed

Simultaneously achieving high sensitivity and detection speed with traditional solid-state biosensors is usually limited since the target molecules must passively diffuse to the sensor surface before they can be detected. Microfluidic techniques have been applied to shorten the diffusion time by continuously moving molecules through the biosensing regions. However, the binding efficiencies of the biomolecules are still limited by the inherent laminar flow inside microscale channels. In this study, focused traveling surface acoustic waves were directed into an acoustic microfluidic chip, which could continuously enrich the target molecules into a constriction zone for immediate detection of the immune reactions, thus significantly improving the detection sensitivity and speed. To demonstrate the enhancement of biosensing, we first developed an acoustic microfluidic chip integrated with a focused interdigital transducer; this transducer had the ability to capture more than 91% of passed microbeads. Subsequently, polystyrene microbeads were pre-captured with human IgG molecules at different concentrations and loaded for detection on the chip. As representative results, ~0.63, 2.62, 11.78, and 19.75 seconds were needed to accumulate significant numbers of microbeads pre-captured with human IgG molecules at concentrations of 100, 10, 1, and 0.1 ng/mL (~0.7 pM), respectively; this process was faster than the other methods at the hour level and more sensitive than the other methods at the nanomolar level. Our results indicated that the proposed method could significantly improve both the sensitivity and speed, revealing the importance of selective enrichment strategies for rapid biosensing of rare molecules.

A review of nanomaterials for biosensing applications

A biosensor is a device that reacts with the analyte to be analyzed, detects its concentration, and generates readable information, which plays an important role in medical diagnosis, detection of physiological indicators, and disease prevention. Nanomaterials have received increasing attention in the fabrication and improvement of biosensors due to their unique physicochemical and optical properties. In this paper, the properties of nanomaterials such as the size effect, optical and electrical properties, and their advantages in the field of biosensing are briefly summarized, and the application of nanomaterials can effectively improve the sensitivity and reduce the detection limit of biosensors. The advantages of commonly used nanomaterials such as gold nanoparticles (AuNPs), carbon nanotubes (CNTs), quantum dots (QDs), graphene, and magnetic nanobeads for biosensor applications are also reviewed. Besides, the two main types of biosensors using nanomaterials involved in their construction and their working principles are described, and the toxicity and biocompatibility of nanomaterials and the future direction of nanomaterial biosensors are discussed.

Au/Pt@ZIF-90 Nanoenzyme Capsule-Based "Explosive" Signal Amplifier for "All-in-Tube" POCT

The sensitive, convenient, and visual detection of low-concentration disease markers in biological samples has always been a priority in disease diagnosis. However, existing research has been problematic due to complex operation and unsatisfactory sensitivity. Consequently, an "explosive" signal amplification platform based on Au/Pt@ZIF-90 was developed for sensitive visual detection of disease markers. In this study, a controllable and explosively released Au/Pt nanoparticles (NPs) "nanoenzyme capsule" was prepared by encapsulating Au/Pt NPs with excellent peroxidase activity in ZIF-90. This was achieved by adjusting the particle size of ZIF-90 and the encapsulation amount of Au/Pt NPs. Using the prepared capsules as the signal output module and aptamer as the target recognition module, an "All-in-Tube" portable point-of-care (POC) platform was constructed by integrating the Au/Pt@ZIF-90/filter paper and TMB/strips into an Eppendorf (EP) tube. By utilizing specific competitive binding of targets to aptamers, the platform enabled the sensitive and convenient measurement of small molecular disease markers. Taking adenosine as the proof of concept, the portable detection achieved excellent sensitivity. Moreover, the platform can achieve universal detection of various targets by varying the aptamer sequence. This signal amplification strategy provides a design pattern for the detection of low-concentration targets in biological samples and holds significant potential in the fields of disease diagnosis and environmental monitoring.

Two birds with one stone: Ratiometric sensing platform overcoming cross-interference for multiple-scenario detection and accurate discrimination of tetracycline analogs

Environmental pollution caused by tetracycline antibiotics (TCs) is a major concern for public health worldwide. Trace detection and reliable discrimination of tetracycline and its analogs are consequently essential to determine the distribution characteristics of various tetracycline family members. Here, a dual-response sensor was constructed by integrating the fluorescence emission of fluorescein isothiocyanate (FITC) doped SiO2 and Eu3+. A portable Lab-on-Paper device is further fabricated through probe immobilization, which allows convenient visual detection of tetracycline using a smartphone. In addition, for the coexistence of multiple tetracycline analogs, dimensionality reduction via principal component analysis is applied to the spectra, realizing accurate differentiation of the four most widely used tetracycline analogs (tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DOX)). The dual-response nanoplatform enabled a wide-gamut color variation crossing from green to red, with limit of detection (LOD) of 2.9 nM and 89.8 nM for spectrometer- and paper-based sensors, respectively. Analytical performance was examined in multiple real samples, including food, environmental, and biological settings, confirming robust environmental adaptability and resistance. Compared to previous TC sensors, this method has several notable improvements, including improved ecological safety, accessibility, reproducibility, practicality, and anti-cross-interference capacity. These results highlight the potential of the proposed "two birds with one stone" strategy, providing an integrated methodology for synchronous quantitative detection and derivative identification toward environmental contaminants.

Immunosensors for Autoimmune-Disease-Related Biomarkers: A Literature Review

Immunosensors are a special class of biosensors that employ specific antibodies for biorecognition of the target analyte. Immunosensors that target disease biomarkers may be exploited as tools for disease diagnosis and/or follow-up, offering several advantages over conventional analytical techniques, such as rapid and easy analysis of patients' samples at the point-of-care. Autoimmune diseases have been increasingly prevalent worldwide in recent years, while the COVID-19 pandemic has also been associated with autoimmunity. Consequently, demand for tools enabling the early and reliable diagnosis of autoimmune diseases is expected to increase in the near future. To this end, interest in immunosensors targeting autoimmune disease biomarkers, mainly, various autoantibodies and specific pro-inflammatory proteins (e.g., specific cytokines), has been rekindled. This review article presents most of the immunosensors proposed to date as potential tools for the diagnosis of various autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, and multiple sclerosis. The signal transduction and the immunoassay principles of each immunosensor have been suitably classified and are briefly presented along with certain sensor elements, e.g., special nano-sized materials used in the construction of the immunosensing surface. The main concluding remarks are presented and future perspectives of the field are also briefly discussed.

Linking peptide-oriented surface imprinting magnetic nanoparticle with carbon nanotube-based fluorescence signal output device for ultrasensitive detection of glycoprotein

Determination of trace glycoprotein has important guiding significance in clinical diagnosis and is usually achieved by immunoaffinity. However, immunoaffinity possesses inherent drawbacks, such as poor probability of high-quality antibodies, instability of biological reagents, and harmfulness of chemical labels to the body. Herein, we propose an innovative method of peptide-oriented surface imprinting to fabricate artificial antibody for recognition of glycoprotein. By integrating peptide-oriented surface imprinting and PEGylation, an innovative hydrophilic peptide-oriented surface imprinting magnetic nanoparticle (HPIMN) was successfully fabricated with human epidermal growth factor receptor-2 (HER2) as a model glycoprotein template. In addition, we further prepared a novel boronic acid-modified/fluorescein isothiocyanate-loaded/polyethylene glycol-covered carbon nanotube (BFPCN) as fluorescence signal output device, which was loaded with numerous fluorescent molecules could specifically label the cis-diol of glycoprotein at physiological pH via boronate-affinity interaction. To prove the practicability, we proposed a HPIMN-BFPCN strategy, in which the HPIMN first selectively captured the HER2 due to the molecular imprinted recognition and then the BFPCN specific labeled the exposed cis-diol of HER2 based on the boronate-affinity reaction. The HPIMN-BFPCN strategy exhibited ultrahigh sensitivity with limit of detection of 14 fg mL^-1 and was successfully used in the determination of HER2 in spiked sample with recovery and relative standard deviation in the range of 99.0%-103.0% and 3.1%-5.6%, respectively. Therefore, we believe that the novel peptide-oriented surface imprinting has great potential to become an universal strategy for fabrication of recognition units for other protein biomarkers, and the synergy sandwich assay could become a powerful tool in prognosis evaluation and clinical diagnosis of glycoprotein-related diseases.

Cerium oxide-doped PEDOT nanocomposite for label-free electrochemical immunosensing of anti-p53 autoantibodies

A label-free nanoimmunosensor is reported based on p53/CeO₂/PEDOT nanobiocomposite-decorated screen-printed gold electrodes (SPAuE) for the electrochemical detection of anti-p53 autoantibodies. CeO₂ nanoparticles (NPs) were synthesized and stabilized with cyanopropyltriethoxysilane by a soft chemistry method. The nanoimmunosensing architecture was prepared by in situ electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on SPAuE in the presence of CeO₂ NPs. The CeO₂ NPs and Ce/PEDOT/SPAuE were characterized by scanning and transmission electron microscopy, dynamic and electrophoretic light scattering, ultraviolet-visible spectrophotometry, X-ray diffraction, Fourier-transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Ce/PEDOT/SPAuE was biofunctionalized with p53 antigen by covalent bonding for the label-free determination of anti-p53 autoantibodies by differential pulse voltammetry. The nanobiocomposite-based nanoimmunosensor detected anti-p53 autoantibodies in a linear range from 10 to 1000 pg mL^-1, with a limit of detection (LOD) of 3.2 pg mL^-1. The nanoimmunosensor offered high specificity, selectivity, and long-term storage stability with great potential to detect anti-p53 autoantibodies in serum samples. Overall, incorporating organo-functional nanoparticles into polymeric matrices can provide a simple-to-assemble, rapid, and ultrasensitive approach for on-site screening of anti-p53 autoantibodies and other disease-related biomarkers with low sample volumes.

Probing polymer brushes with electrochemical impedance spectroscopy: a mini review

Polymer brushes are frequently used as surface-tethered antifouling layers in biosensors to improve sensor surface-analyte recognition in the presence of abundant non-target molecules in complex biological samples by suppressing nonspecific interactions. However, because brushes are complex systems highly responsive to changes in their surrounding environment, studying their properties remains a challenge. Electrochemical impedance spectroscopy (EIS) is an emerging method in this context. In this mini review, we aim to elucidate the potential of EIS for investigating the physicochemical properties and structural aspects of polymer brushes. The application of EIS in brush-based biosensors is also discussed. Most common principles employed in these biosensors are presented, as well as interpretation of EIS data obtained in such setups. Overall, we demonstrate that the EIS-polymer brush pairing has a considerable potential for providing new insights into brush functionalities and designing highly sensitive and specific biosensors.

Ultrasensitive detection of specific IgE based on nanomagnetic capture and separation with a AuNP-anti-IgE nanobioprobe for signal amplification

The accurate detection of allergen specific IgE (sIgE) is fundamental in the diagnosis of allergic diseases. The present commercial platforms fail to meet the need for personalized diagnosis, due to the unsuitable allergen-fixation model and large amounts of serum consumption. In this work, we developed a nano-capturer Fe₃O₄@SiO₂-NTA with an enhanced signal by taking advantage of a AuNP-anti-IgE nanobioprobe for precise and highly sensitive quantification detection of sIgE in serum of allergic patients. The recombinant allergen was immobilized on Fe₃O₄@SiO₂-NTA through the interaction between its His-tag and Ni-NTA, which is more consistent with the real binding mode of allergens with sIgE in vivo than the present clinically used allergen-fixation methods. Numerous horseradish peroxidase (HRP)-labeled anti-IgE were modified onto one AuNP to detect the sIgE probed by Fe₃O₄@SiO₂-NTA@rCanf1. Once one anti-IgE binds to sIgE, other HRP-labeled anti-IgE modified on the same AuNP would all create signals, resulting in a significantly amplified chemiluminescence (CL) signal. Our results showed that this immunosensor could realize fast, accurate, low-cost and highly sensitive sIgE detection in serum samples. In vitro experiments demonstrated a 0.02 ng mL^-1 detection limit, which was lower than that of any standard analyzer used for allergy immunoassays. Furthermore, our method was utilized for the diagnosis of clinical samples. The results were in good agreement with those obtained by the clinical gold standard ImmunoCAP, with 1000 times less serum consumption than ImmunoCAP. Therefore, the presented immunosensor holds great promise to improve clinical sIgE quantitative detection and constitutes a potentially useful tool for clinical diagnosis and subsequent individual treatment of allergic diseases.

High-Fidelity and Simultaneous Sensing of Endogenous Mutant and Wild p53 Proteins for Precise Cancer Diagnosis and Drug Screening

The simultaneous sensing of endogenous wild and mutant proteins plays a critical role in disease diagnosis and drug screening, and this remains a major current challenge. Here, we present a new and highly specific target-triggered dual proximity ligation assay (dPLA) strategy for sensitive and simultaneous sensing of wild and mutant p53 proteins from cancer cells. Two proximity DNA probes bind the target protein to form the primer/circular DNA template complexes with two nicks in the presence of the hairpin and ssDNA connector sequences via the strand displacement reaction. Only when the two nicks are simultaneously ligated can the rolling circle amplification be triggered with high fidelity for yielding substantially enhanced fluorescence. By encoding the hairpin sequence, two distinct fluorescence signals can be generated for simultaneous detection of the wild and mutant p53 proteins. Importantly, our method significantly reduces the possibility of nonspecific ligation reactions by using two ligation nicks, which minimizes the background noise. With this dPLA method, the regulation transition of intracellular mutant p53 to wild p53 proteins upon anticancer drug treatment has also been demonstrated, highlighting its usefulness for potential early disease diagnosis and drug screening with high fidelity.