Magnetized carbon nanotubes for visual detection of proteins directly in whole blood

Lateral flow DNA biosensor for visual detection of nucleic acid with triple-helix DNA functionalized carbon nanotube

We describe a novel lateral flow DNA biosensor (LFDB) based on carbon nanotube (CNT) and triple helix DNA (THD). The carboxylated CNT was first conjugated with amine-modified auxiliary single-stranded DNA probe (P1) by dehydration reaction and used as signal probe. A main DNA probe (P0) was introduced to react with the P1 and formed the THD on the CNT surface. Because of the large spatial effect, P1 was in an inactive state and cannot hybridize with the capture DNA probe (P2) fixed on the LFDB test area. When the target DNA was present, P0 in the triple helix DNA hybridized with the target DNA due to the stronger base action, and the decomposition of the triple helix structure exposed P1. Therefore, P1 on CNT surface was activated to hybridize with P2. The CNT along with P1 was thus captured at the test area and accumulated to show a black line, which can be observed by naked eye for qualitative analysis and recorded with a portable grayscale reader for quantitative analysis. Single-stranded DNA was used as a target to prove the feasibility of the model. Under the best experimental conditions, the THD-CNT based LFDB was able to detect the lowest DNA concentration of 15 pM, which is 2.67 times better than that of the traditional duplex CNT-based LFDB. It should be noted that the LFDB based on THD functionalized CNT can differentiate between one-base-mismatched DNA and the complementary target DNA, can detected target DNA in 10% human serum, and can be employed as a versatile platform to detect various target (proteins, small molecular) by changing the sequence of P0. This biosensor platform has enormous potential in the point-of-care detection of a rich diversity of analytes for clinical diagnosis and biomedical research.

The Use of Crystalline Carbon-Based Nanomaterials (CBNs) in Various Biomedical Applications

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

Advances in Novel Nanomaterial-Based Optical Fiber Biosensors-A Review

This article presents a concise summary of current advancements in novel nanomaterial-based optical fiber biosensors. The beneficial optical and biological properties of nanomaterials, such as nanoparticle size-dependent signal amplification, plasmon resonance, and charge-transfer capabilities, are widely used in biosensing applications. Due to the biocompatibility and bioreceptor combination, the nanomaterials enhance the sensitivity, limit of detection, specificity, and response time of sensing probes, as well as the signal-to-noise ratio of fiber optic biosensing platforms. This has established a practical method for improving the performance of fiber optic biosensors. With the aforementioned outstanding nanomaterial properties, the development of fiber optic biosensors has been efficiently promoted. This paper reviews the application of numerous novel nanomaterials in the field of optical fiber biosensing and provides a brief explanation of the fiber sensing mechanism.

Multifunctional carbon nanomaterials for diagnostic applications in infectious diseases and tumors

Infectious diseases (such as Corona Virus Disease 2019) and tumors pose a tremendous challenge to global public health. Early diagnosis of infectious diseases and tumors can lead to effective control and early intervention of the patient's condition. Over the past few decades, carbon nanomaterials (CNs) have attracted widespread attention in different scientific disciplines. In the field of biomedicine, carbon nanotubes, graphene, carbon quantum dots and fullerenes have the ability of improving the accuracy of the diagnosis by the improvement of the diagnostic approaches. Therefore, this review highlights their applications in the diagnosis of infectious diseases and tumors over the past five years. Recent advances in the field of biosensing, bioimaging, and nucleic acid amplification by such CNs are introduced and discussed, emphasizing the importance of their unique properties in infectious disease and tumor diagnosis and the challenges and opportunities that exist for future clinical applications. Although the application of CNs in the diagnosis of several diseases is still at a beginning stage, biosensors, bioimaging technologies and nucleic acid amplification technologies built on CNs represent a new generation of promising diagnostic tools that further support their potential application in infectious disease and tumor diagnosis.

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Carbon nanomaterials (CNs) are systematically introduced in this review.

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This review studies the application of CNs in infectious diseases and tumors diagnosis.

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CNs act as potent nanostructures for biosensing, bioimaging, & nucleic acid amplification.

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New CN-based detection methods were introduced to detect SARS-CoV-2.

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The challenges and prospects of CN-based diagnostic assays are also discussed.

Paper-microfluidic signal-enhanced immunoassays

Over the past decade, paper-based microfluidic devices have become popular for their simplicity and ability to conduct diagnostic tests at a low cost. An important class of diagnostic assays that paper-based analytical devices have been used for is immunoassays. The lateral flow immunoassay (LFIA), of which the home pregnancy test is the most prominent example, has been one of the most commercially successful membrane-based diagnostic tests. Yet, the analytical sensitivity of LFIAs is lower than the corresponding laboratory technique called ELISA (enzyme-linked immunoassay). As a consequence, traditional LFIAs fail to deliver on the promise of bedside diagnostic testing for many applications. Recognizing this shortcoming, several new developments have been made by researchers to enhance the sensitivity of membrane-based immunoassays. In this chapter, we present the various strategies that have been employed to this end. In the end, we present a brief SWOT analysis to guide future work in this area.

β-Amyloid Peptide 1-42-Conjugated Magnetic Nanoparticles for the Isolation and Purification of Glycoproteins in Egg White

Aβ_1-42-conjugated magnetic nanoparticles, Aβ_1-42@MNP, were prepared by covalently coupling Aβ_1-42 to hyperbranched polyethyleneimine (PEI)-modified magnetic nanoparticles via N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). Aβ_1-42's high binding capacity to glycosyl groups facilitates Aβ_1-42@MNP composite to be a promising selective adsorbent for glycoproteins in egg whites. In our study, under conditions of pH 4.0, the adsorption efficiency of Aβ_1-42@MNP composite for ovalbumin (100 μg mL^-1) was 98.4% and its maximum adsorption capacity was 344.8 mg g ^-1; under the condition of pH 4.0 and 200 mmol L^-1 NaCl, its adsorption efficiencies for ovalbumin and ovotransferrin were 96.9% and 60.0%, respectively. According to these primary data, in practice, ovalbumin was removed from egg white by Aβ_1-42@MNP composite at pH 4.0 (step I), and then after adding NaCl until the final salt concentration reached 200 mmol L^-1 (pretreated egg white), we utilized the same adsorbent to further isolate/purify glycoproteins (step II). SDS-PAGE results showed that Aβ_1-42@MNP composite could largely remove ovalbumin in step I and could isolate/purify the remaining ovalbumin and ovotransferrin in step II. LC-MS/MS analysis results showed that the removal of ovalbumin reduced its percentage in egg white samples from 32.93% to 11.05% in step I and the remaining ovalbumin and ovotransferrin were enriched in step II, where the final percentage reached 11.6% and 12.6%, respectively. In summary, 81 protein species were identified after two-step extraction with Aβ_1-42@MNP on egg white, while only 46 protein species were identified directly from raw egg white without any pretreatment. This work well illustrates the excellent adsorption performance of Aβ_1-42@MNP composite to glycoproteins and its potential in the application of proteomic studies on low-abundance proteins in egg white.

Lateral flow biosensors based on the use of micro- and nanomaterials: a review on recent developments

This review (with 187 refs.) summarizes the progress that has been made in the design of lateral flow biosensors (LFBs) based on the use of micro- and nano-materials. Following a short introduction into the field, a first section covers features related to the design of LFBs, with subsections on strip-based, cotton thread-based and vertical flow- and syringe-based LFBs. The next chapter summarizes methods for sample pretreatment, from simple method to membrane-based methods, pretreatment by magnetic methods to device-integrated sample preparation. Advances in flow control are treated next, with subsections on cross-flow strategies, delayed and controlled release and various other strategies. Detection conditionst and mathematical modelling are briefly introduced in the following chapter. A further chapter covers methods for reliability improvement, for example by adding other validation lines or adopting different detection methods. Signal readouts are summarized next, with subsections on color-based, luminescent, smartphone-based and SERS-based methods. A concluding section summarizes the current status and addresses challenges in future perspectives. Graphical abstractRecent development and breakthrough points of lateral flow biosensors.

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing.

Comparison of three sample addition methods in competitive and sandwich colloidal gold immunochromatographic assay

Immunochromatographic assays (ICAs) are mainstream point-of-care diagnostic tools in disease control, food safety, and environmental monitoring. However, the important issue pertaining to the influence of sample addition methods on the detection performance of ICAs has not been addressed, and related information is still lacking. Herein, we selected the well-accepted gold nanoparticles (AuNPs) as visual labels. AuNP-based ICA was then used to explore the effects of three sample addition methods (i.e., dry, wet, and insert) on the analytical performance of ICAs by using competitive and sandwich models. Under optimized conditions, the competitive ICA with clenbuterol as an analyte showed a negligible difference (p > 0.05) in the detection performance of the three methods in ideal phosphate buffered saline solution. However, the wet method demonstrated the worst performance in pork samples (p < 0.05). The sandwich ICA strip with human chorionic gonadotropin as an analyte revealed the significantly different analytical performances of the three approaches in phosphate buffer (PB) solution and spiked serum (p < 0.05). Two independent linear correlations were observed with the increase in target concentration. However, for the wet method in the PB solution and serum, the first linear correlation was at a relatively narrow target concentration range, and the second linear correlation was at a wider concentration range compared with those for the dry and insert methods. Our findings demonstrated that sample addition methods slightly influence competitive ICAs (p > 0.05) but remarkably affect sandwich ICAs (p < 0.05). We believe that this study can further explain the differences in detection results for the same target analyte in actual ICA detection. The results may serve as a reference in the rational selection of the appropriate sample addition method for succeeding ICA works.

Magnetized Carbon Nanotube Based Lateral Flow Immunoassay for Visual Detection of Complement Factor B

The authors describe a magnetized carbon nanotube (MCNT) based lateral flow immunoassay (LFI) for visual detection of complement factor B (CFB) in blood. MCNT was prepared by decorating magnetic Fe₃O₄ nanoparticles on multi-walled CNT surface and used as a colored tag for LFI. Monoclonal antibody (mAb, Ab₁) of CFB was covalently immobilized on the MCNT surface via diimide-activated conjugation between the carboxyl groups on the MCNT surface and amino groups of antibodies. Polyclonal antibody of CFB (Ab₂) and the secondary antibody were used to prepare the lateral flow test strips. The assay involved: (1) the capture of CFB in blood with the mAb-functionalized MCNT; (2) magnetic separation of the formed CFB-mAb-MCNT and excess of mAb-MCNT from the blood with an external magnet; (3) lateral flow test to capture the CFB-mAb-MCNT complex on the test zone and the excess of mAb-MCNT on the control zone; (4) Recording the intensities of the produced the characteristic brown bands with a portable strip reader and quantitating the concentration of CFB. The proof-of-concept was demonstrated by testing CFB in the buffer, and the detection limit was 5 ng mL^-1 under the optimized analytical parameters. CFB in 1 μL of human blood was detected successfully in 30 min with this LFI and the results had a high correlation with commercial ELISA kit. Thence, the MCNT-based LFI offers a rapid and low-cost tool for detecting CFB in human blood directly.

Gold-platinum nanoflowers as a label and as an enzyme mimic for use in highly sensitive lateral flow immunoassays: application to detection of rabbit IgG

The authors describe the preparation of gold-platinum nanoflower (AuPt NFs) and show that they can be simultaneously used as a label and as an enzyme mimic in lateral flow immunoassays (LFIs). The AuPt NFs were prepared by growing Pt nanowires on the surface of gold nanoparticle. The assay involves the capture of target proteins (here: rabbit IgG as a model analyte) by the immobilized capture antibody, and by using AuPt NF-labeled secondary antibody. The AuPt NFs are thus captured by the test zone and produce a characteristic black band for visual detection of the antigen (IgG). The coloration of the test line can be further enhanced by addition of the chromogenic substrate 3-amino-9-ethyl-carbazole which is catalytically oxidized by the captured Pt nanowires on the AuPt NF and produce a red coloration. Quantitative results were obtained by reading the test line intensities with a portable strip reader. The LFI has a 5 pg mL-1 detection limit for IgG under optimized experimental conditions. This is 100 times lower than that of the conventional AuNP-based LFI. Conceivably, this assay has a wide scope in that it may be applied to numerous other targets for which appropriate antibodies are available. Graphical abstract Gold-platinum nanoflowers are used as a label and as an enzyme mimic in a highly sensitive lateral flow immunoassay for IgG. The detection limit of gold-platinum nanoflower-based lateral flow assay is 100 times lower than that of the conventional gold nanopaticle-based lateral flow assay.

Detection platforms for point-of-care testing based on colorimetric, luminescent and magnetic assays: A review

Along with the considerable potential and increasing demand of the point-of-care testing (POCT), corresponding detection platforms have attracted great interest in both academic and practical fields. The first few generations of conventional detection devices tend to be costly, complicated to operate and hard to move on account of early limitations in the level of technological development and relatively high requirement of performance. Owing to the requirements for rapidity, simplicity, accuracy and cost controlling in the POCT, reader systems are urgently needed to be developed, upgraded and modified constantly, realizing on-site testing and healthcare management without a specific place or cumbersome operation. Accordingly, numerous rapid detection platforms with diverse size and performance have emerged such as bench-top apparatuses, handheld devices and intelligent detection devices. This review discusses various devices developed mainly for the detection of lateral flow test strips (LFTSs) or microfluidic strips in the POCT and summarizes these devices by size and portability. Furthermore, on the basis of various detection methods and diverse probes usually containing specific nanoparticles composites, three most common aspects of detection rationale in the POCT are selected to elaborate each kind of detection platforms in this paper: colorimetric assay, luminescent detection and magnetic signal detection. Herein, we focus on their structures, detection mechanisms and assay results, accompany with discussions and comments on the performances, costs and potential application, as well as advantages and limitations of each technique. In addition, perspectives on the future advances of detection platforms and some conclusions are proposed.