Nanocages and cell-membrane display technology as smart biomaterials

Gold nanocages (AuNCs) have been invented and developed over two decades as biomaterial in clinical medicine with great application potential. AuNCs have a characteristic structure of porous walls with hollow interior and a compact size. This makes it possible for them to transport biomolecules or drugs with the advantages of their photothermal effects that could help further destroy germs or tumors while also regulating the release of drugs inside. Furthermore, their bioactivity and application can be broadened by using cell-membrane display technology. AuNCs have shown tremendous potential in antibacterial activity, inflammation modulation, and tissue regeneration, which is required in periodontitis and peri-implantitis treatment. Thus, this article provides an overview of AuNCs synthesis, characteristics, surface modifications, and clinical applications, aiming to serve as a reference for the design and fabrication of AuNCs-based smart materials for periodontal or peri-implant application.

SERS-based methods for the detection of genomic biomarkers of cancer

Genomic biomarkers of cancer are based on changes in nucleic acids, which include abnormal expression levels of some miRNAs, point mutations in DNA sequences, and altered levels of DNA methylation. The presence of tumor-related nucleic acids in body fluids (blood, saliva, or urine) makes it possible to achieve a non-invasive early-stage cancer diagnosis. Currently existing techniques for the discovery of nucleic acids require complex, time-consuming, costly assays and have limited multiplexing abilities. Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique that is able to provide molecular specificity combined with trace sensitivity. SERS has gained research attention as a tool for the detection of nucleic acids because of its promising potential: label-free SERS can decrease the complexity of assays currently used with fluorescence-based detection due to the absence of the label, while labeled SERS may outperform the gold standard in terms of the multiplexing ability. The first papers about SERS-based methods for the measurement of genomic biomarkers were written in 2008, and since then, more than 150 papers have been published. The aim of this paper is to review and evaluate the proposed SERS-based methods in terms of their level of development and their potential for liquid biopsy application, as well as to contribute to their further evolution by attracting research attention to the field. This goal will be reached by grouping, on the basis of their experimental protocol, all the published manuscripts on the topic and evaluating each group in terms of its limit of detection and applicability to real body fluids. Thus, the methods are classified according to their working principles into five main groups, including capture-based, displacement-based, sandwich-based, enzyme-assisted, and specialized protocols.

Rapid and sensitive detection of superoxide dismutase in serum of the cervical cancer by 4-aminothiophenol-functionalized bimetallic Au-Ag nanoboxs array

Early, efficient and sensitive detection of serum markers in cervical cancer is very important for the treatment and prognosis to cervical cancer patients. In this paper, a SERS platform based on surface enhanced Raman scattering technology was proposed to quantitatively detect superoxide dismutase in serum of cervical cancer patients. Au-Ag nanoboxs array was made by oil-water interface self-assembly method as the trapping substrate. The single-layer Au-AgNBs array was verified by SERS for possessing excellent uniformity, selectivity and reproducibility. 4-aminothiophenol (4-ATP) was used as Raman signal molecule, it will be oxidized to dithiol azobenzene under the surface catalytic reaction with the condition of PH = 9 and laser irradiation. The quantitative detection of SOD could be achieved by calculating the change of characteristic peak ratio. When the concentration was from 10 U mL−1–160 U mL−1, the concentration of SOD could be accurately and quantitatively detected in human serum. The whole test was completed within 20 min and the limit of quantitation was 10 U mL−1. In addition, serum samples from the cervical cancer, the cervical intraepithelial neoplasia and healthy people were tested by the platform and the results were consistent with those of ELISA. The platform has great potential as a tool for early clinical screening of cervical cancer in the future.

Recent Progress in Plasmonic based Electrochemiluminescence Biosensors: A Review

Electrochemiluminescence (ECL) analysis has become a powerful tool in recent biomarker detection and clinic diagnosis due to its high sensitivity and broad linear range. To improve the analytical performance of ECL biosensors, various advanced nanomaterials have been introduced to regulate the ECL signal such as graphene, gold nanomaterials, and quantum dots. Among these nanomaterials, some plasmonic nanostructures play important roles in the fabrication of ECL biosensors. The plasmon effect for the ECL signal includes ECL quenching by resonant energy transfer, ECL enhancement by surface plasmon resonance enhancement, and a change in the polarized angle of ECL emission. The influence can be regulated by the distance between ECL emitters and plasmonic materials, and the characteristics of polarization angle-dependent surface plasmon coupling. This paper outlines the recent advances of plasmonic based ECL biosensors involving various plasmonic materials including noble metals and semiconductor nanomaterials. The detection targets in these biosensors range from small molecules, proteins, nucleic acids, and cells thanks to the plasmonic effect. In addition to ECL biosensors, ECL microscopy analysis with plasmonic materials is also highlighted because of the enhanced ECL image quality by the plasmonic effect. Finally, the future opportunities and challenges are discussed if more plasmonic effects are introduced into the ECL realm.

SERS "hot spot" enhance-array assay for misfolded SOD1 correlated with white matter lesions and aging

Misfolding of superoxide dismutase-1 (SOD1) has been correlated with many neurodegenerative diseases, such as Amyotrophic lateral sclerosis's and Alzheimer's among others. However, it is unclear whether misfolded SOD1 plays a role in another neurodegenerative disease of white matter lesions (WMLs). In this study, a sensitive and specific method based on SERS technique was proposed for quantitative detection of misfolded SOD1 content in WMLs. To fabricate the double antibodysandwich substrates for SERS detection, gold nanostars modified with capture antibody were immobilized on glass substrates to prepare active SERS substrates, and then SERS probes conjugated with a Raman reporter and a specific target antibody were coupled with active SERS substrates. This SERS substrates had been employed for quantitative detection of misfolded SOD1 levels in WMLs and exhibited excellent stability, reliability, and accuracy. Moreover, experimental results indicated that the level of misfolded SOD1 increased with the increase in age and the degree of WMLs. Hence, misfolded SOD1 may be a potential blood marker for WMLs and aging. Meanwhile, SERS-based gold nanostars have great clinical application potential in the screening, diagnosis and treatment of WMLs.

Recent advances of catalytic hairpin assembly and its application in bioimaging and biomedicine

Catalytic hairpin assembly (CHA) appears to be a particularly appealing nucleic acid circuit because of its powerful amplification capability, simple protocols, and enzyme-free and isothermal conditions, and can combine with various signal output modes for the biosensing of various analytes. Especially in the last five years, vast CHA related studies have sprung up. With the deep exploration of the CHA mechanism, some novel and excellent CHA strategies have been proposed; meanwhile the CHA cascade strategies with various amplification techniques further improve the analysis performance. Furthermore, diverse CHA based biosensors have been tactfully engineered and extensively employed in imaging applications in living cells and in vivo ascribed to its gentle reaction, efficient amplification and universality. Hence, we present a comprehensive and systematic summary of the progress in CHA and its application in bioimaging and biomedicine to date. At first, we introduced the mechanism and diversification of CHA in detail, including the newly developed CHA and its ingenious combination with a variety of other technologies. Concurrently, we summarized the latest application progress of different CHA strategies in bioimaging and biomedicine, highlighting the merits and drawbacks of representative approaches. Finally, we put forward some views on the challenges and prospects of CHA in bioimaging and biomedicine in the future.

Plasmonic Nanomaterials for Colorimetric Biosensing: A Review

In the last few decades, plasmonic colorimetric biosensors raised increasing interest in bioanalytics thanks to their cost-effectiveness, responsiveness, and simplicity as compared to conventional laboratory techniques. Potential high-throughput screening and easy-to-use assay procedures make them also suitable for realizing point of care devices. Nevertheless, several challenges such as fabrication complexity, laborious biofunctionalization, and poor sensitivity compromise their technological transfer from research laboratories to industry and, hence, still hamper their adoption on large-scale. However, newly-developing plasmonic colorimetric biosensors boast impressive sensing performance in terms of sensitivity, dynamic range, limit of detection, reliability, and specificity thereby continuously encouraging further researches. In this review, recently reported plasmonic colorimetric biosensors are discussed with a focus on the following categories: (i) on-platform-based (localized surface plasmon resonance, coupled plasmon resonance and surface lattice resonance); (ii) colloid aggregation-based (label-based and label free); (iii) colloid non-aggregation-based (nanozyme, etching-based and growth-based).

Recent progress in electrochemiluminescence microscopy analysis of single cells

An overview of recent progress in electrochemiluminescence microscopy analysis of single cells classified according to different ECL routes, namely the oxidative-reduction, low oxidation potential, catalytic and direct oxidation routes.

Recent advances in catalytic hairpin assembly signal amplification-based sensing strategies for microRNA detection

Accumulative evidences have indicated that abnormal expression of microRNAs (miRNAs) is closely associated with many health disorders, making them be regarded as potentialbiomarkers for early clinical diagnosis. Therefore, it is extremely necessary to develop a highly sensitive, specific and reliable approach for miRNA analysis. Catalytic hairpin assembly (CHA) signal amplification is an enzyme-free toehold-mediated strand displacement method, exhibiting significant potential in improving the sensitivity of miRNA detection strategies. In this review, we first describe the potential of miRNAs as disease biomarkers and therapeutics, and summarize the latest advances in CHA signal amplification-based sensing strategies for miRNA monitoring. We describe the characteristics and mechanism of CHA signal amplification and classify the CHA-based miRNA sensing strategies into several categories based on the "signal conversion substance", including fluorophores, enzymes, nanomaterials, and nucleotide sequences. Sensing performance, limit of detection, merits and disadvantages of these miRNA sensing strategies are discussed. Moreover, the current challenges and prospects are also presented.

Lateral flow assay-based detection of long non-coding RNAs: A point-of-care platform for cancer diagnosis

Lateral flow assay (LFA) is a flexible, simple, low-costpoint-of-care platform for rapid detection of disease-specific biomarkers. Importantly, the ability of the assay to capture the circulating bio-molecules has gained significant attention, as it offers a potential minimal invasive system for early disease diagnosis and prognosis. In the present article, we review an innovative concept of LFA-based detection of circulating long non-coding RNAs (lncRNAs), one of the key regulators of fundamental biological processes. In addition, their disease-specific expression pattern and presence in biological fluids at differential levels make them excellent biomarker candidates for cancer detection. Our article also provides an update on the requirements for developing and improving such systems and discusses the key aspects of material selection, operational concepts, principles and conceptual design. We assume that the reviewed points will be helpful to improve the diagnostic applicability of LFA based lncRNA detection in cancer diagnosis.

A highly sensitive electrochemical biosensor for microRNA122 detection based on a target-induced DNA nanostructure

Specific and sensitive biomarker detection is significant for the early diagnosis of cancers. Herein, a highly sensitive electrochemical biosensor employing a tetrahedral DNA nanostructure (TDN) probe and multiple signal amplification strategies has been constructed, and successfully applied to microRNA-122 (miR-122) detection. The platform consisted of a TDN probe anchoring on a gold nanoparticle-coated gold electrode and multiple signal amplification procedures combining the electrodeposition of gold nanoparticles, hybridization chain reaction (HCR), and horseradish peroxidase enzymatic catalysis (HPEC). In the presence of the target, the hairpin structure of the helper probe could be opened and trigger the HCR through the hybridization of H1 and H2 probes, and then avidin-HRP was attached on the surface of the gold electrode that can produce an electro-catalytic signal. We used TDN probe as the scaffold to increase the reactivity and multiple signal amplification greatly improve the sensitivity of this biosensor. This biosensor offers an excellent sensitivity (a limit of detection of 0.74 aM) and differentiation ability for single and multiple mismatches. This multiplexing biosensor for trace microRNA detection shows promising applications in the early diagnosis of cancer.

A new gold nanoflower sol SERS method for trace iodine ion based on catalytic amplification

As one of the essential trace elements in metabolism, iodine is crucial to maintain the normal physiological functions. Therefore, based on health and environmental protection, it is very important to realize sensitive detection of iodide ion. Herein, we developed a simple, rapid and sensitive method for the determination of iodide ion. Trypsin was used as an ideal template for the synthesis of gold nanoflower sol (AuNFs) with anisotropic surface structure and good stability. It exhibits highly active surface enhanced Raman scattering (SERS) effect and can be used as facile SERS sol substrate. The TMBox generated by the catalytic oxidation reaction of TMB-chloramine T-iodide ion is used as the SERS probe. The enhanced SERS signal intensity is linearly related to the iodide ion with high sensitivity. In addition, TMB has fluorescence effect, and the colored TMBox can produce RRS signal due to polymerization. Based on this, a quad-mode detection method of SERS, RRS, fluorescence and colorimetry for quantitative detection of trace iodide ions was established, and this method can be applied to the detection of iodide ions in natural water and drinking water.

Versatile template-directed synthesis of gold nanocages with a predefined number of windows

Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures. The optical properties of nanocages with 4 and 12 windows were measured at the single particle level by spatial modulation spectroscopy and correlated with numerical simulations based on finite-element modeling. The new multi-step synthesis approach reported here also allows the synthesis of rattle-like nanostructures through filling of the nanocages with a guest nano-object. With the potential to adjust the chemical composition, size and geometry of both the guest particle and the host cage, it opens new routes towards the fabrication of hollow nanostructures of high interest for a variety of applications including sensing devices, catalytic reactors and biomedicine.

FeII 4L4 Tetrahedron-Assisted Three-Way Junction Probe for Multiple miRNA Detection

MicroRNAs (miRNAs) modulate a variety of cellular signaling pathways and play a vital role in cell-to-cell communication. The overlapped expression of a certain miRNA is commonly reported to be related to cancers. Therefore, combined detection of multiple miRNAs is of great significance for cancer diagnosis. Herein, we developed a Fe^II ₄L₄ tetrahedron-assisted three-way junction (3WJ) probe, which exhibited a higher stability than the normal 3WJ probe, for multiple miRNA detection. In this method, the simultaneous existence of miRNA-21 and miRNA-144 triggers the release of the Y3 sequence in the Fe^II ₄L₄ tetrahedron-assisted 3WJ probe, which in turn triggers subsequent CRISPR-Cas12a-assisted rolling circle amplification. Based on this, simultaneous detection of miRNA-21 and miRNA-144 was achieved. Furthermore, we also applied this method to the detection of miRNAs in clinical samples and achieved good agreement with quantitative real-time polymerase chain reaction (qRT-PCR), indicating its significant potentials in early diagnosis and treatment of cancer.

A novel surface-enhanced Raman scattering probe based on Au nanoboxes for dynamic monitoring of caspase-3 during cervical cancer cell apoptosis

The highly sensitive and reliable detection, imaging, and monitoring of changes of intracellular caspase-3 are critical for understanding the cell apoptosis and studying the progression of caspase-3-related cervical cancer.

Fluorescent-Raman Binary Star Ratio Probe for MicroRNA Detection and Imaging in Living Cells

The expression of microRNAs (miRNAs) is critical in gene regulation and has been counted into disease diagnosis marks. Precise imaging and quantification of miRNAs could afford the important information for clinical diagnosis. Here, two smart binary star ratio (BSR) probes were designed and constructed, and miRNA triggered the connection of the binary star probes and the reciprocal changes of dual signals in living cells. This multifunctional probe integrates fluorescence and surface enhanced Raman scattering (SERS) imaging, with enzyme-free numerator signal amplification for dual-mode imaging and dual-signal quantitative analysis of miRNA. First, compared with the single-mode ratio imaging method, using fluorescence-SERS complementary ratio imaging, this probe enables more accurate imaging contrast for direct visualization signal changes in living cells. Multiscale information about the dynamic behavior of miRNA and the probe is acquired. Next, via SERS reverse signal ratio response and a novel enzyme-free numerator signal amplification, the amplified signal and reduced black value were achieved in the quantification of miRNA. More importantly, BSR probes showed good stability in cells and were successfully used for accurate tracing and quantification of miR-203 from MCF-7 cells. Therefore, the reported BSR probe is a potential tool for the reliable monitoring of biomolecule dynamics in living cells.

Prediction of premature rupture of membranes via simultaneous detection of procalcitonin and interleukin-6 by a SERS-based immunochromatographic assay

The rapid and sensitive detection strip with two test lines was developed based on SERS for the early screening of PROM.