Stacked hexagonal prism of Ag@Ni-MOF-1 as functionalized SERS platform through rational integration of catalytic synthesis of dopamine-quinone at physiological pH with a biomimetic route

State-of-the-Art, Insights, and Perspectives for MOFs-Nanocomposites and MOF-Derived (Nano)Materials

Composite structures created from metal‒organic framework (MOF) matrices are reviewed in this work. Depending on the nature of the second component apart from the MOF platform, several synergistic properties may arise; at the same time, the initial features of the single constituent materials are usually maintained, and individual shortcomings are mitigated. Currently, timely energy and environmental challenges necessitate the quest for more advanced materials and technologies. Significant developments in MOF-nanocomposites have enabled their application across a wide range of modern and traditional fields. This review demonstrates in an exhaustive and critical way a broad range of MOF-based nanocomposites, namely, MOF/perovskite nanoparticles (NPs), MOF/metal (non-iron) oxide NPs, MOF/Fe3O4 NPs, MOF/metal chalcogenide NPs, MOF/metal NPs, and MOF/carbon-based materials, as well as nanocomposites of MOFs with other semiconductor NPs. Key points related to the synthesis, characterization, and applications of these materials are provided. Depending on their configuration, the composites under discussion can be applied in domains such as photoelectrochemical sensing, antibiotic/dye degradation, optoelectronics, photovoltaics, catalysis, solar cells, supercapacitors, batteries, water remediation, and drug loading. Sometimes, MOFs can undergo certain processes (e.g. pyrolysis) and act as precursors for composite materials with appealing characteristics. Therefore, a special section in the manuscript is devoted to MOF-derived NP composites. Toward the end of the text, we conclude while also describing the challenges and possibilities for further investigations in the umbrella of material categories analyzed herein. Despite the progress achieved, key questions remain to be answered regarding the relationships among the morphology, properties, and polyvalent activity of these materials. The present work aims to shed light on most of their aspects and innovative prospects, facilitating a deeper comprehension of the underlying phenomena, functionality, and mechanistic insights governing their behavior.

A Review on the Recent Progress of Metal-Organic Frameworks Based Surface Enhanced Raman Scattering Sensors

Surface enhanced Raman scattering (SERS) has evolved into a significant fingerprint spectroscopic technique for rapidly and nonintrusively tracing target analytes through effective SERS substrates. Metal-organic frameworks (MOFs), as a boom crystalline porous material, serve as promising SERS substrates by accommodating noble metal nanoparticles (NPs) to produce MOFs-based SERS-active materials. Recently, MOFs-based SERS materials (MNPs/MOFs) have gained significant attention due to their enhanced sensing performance. The unique porous nature of MOFs provides an efficient capture capability for analytes, while their shells prevent NPs from oxidization and corrosion, thereby enhancing the consistency of SERS substrates. So far, numerous MNPs/MOFs sensors have been documented. This review outlines the research progress of MNPs/MOFs composites, focusing on the classification, synthesis strategies, and applications in environment analysis, real-time monitoring, food safety, etc.

Enhanced electrochemical detection of dopamine and uric acid using Au@Ni-MOF and employing 2D structure DFT simulation

The accurate and expeditious detection of minute biomolecules within human body fluids holds paramount significance in the advancement of novel electrode materials. In this research, a novel non-enzyme electrochemical sensor was constructed. It was founded on Au@Ni-MOF (Ni(CH3CO2)2) hybrids, with Ni(II) (nickel acetate) serving as the precursor. Specifically, [Ni3(BTC)2]n (H3BTC = 1,3,5-trimesic acid) featuring coordinatively unsaturated Ni(II) sites and decorated with gold nanoparticles was synthesized via an in-situ growth methodology. The Au@Ni-MOF hybrids exhibit outstanding electrochemical and electrocatalytic characteristics, attributable to the meticulous assembly of AuNPs and Ni-MOF. The Au@Ni-MOF (Ni(CH3CO2)2)/SPCE was fabricated onto the surface of the screen-printed electrode (SPCE). Subsequently, its electrochemical performance was probed for the discrete and concurrent quantification of dopamine (DA) and uric acid (UA) in 0.01 M phosphate-buffered saline through differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Notably, the cathodic peak current manifested a linear correlation with the DA and UA concentrations across an extensive range, spanning from 0.1 µM to 2 mM for DA and from 0.5 µM to 1.5 mM for UA, respectively. This sensor is applicable in non-enzyme sensing of DA and UA. Additionally, the adsorption energy and bond length of the 2D structures of Ni-MOF and Au@Ni-MOF (Ni(CH3CO2)2) were ascertained via DFT simulations, thereby affording valuable insights into the interaction mechanisms between biomolecules and the surfaces of these 2D structures.

Sensitive SERS assay for L-cysteine based on functionalized silver nanoparticles

L-cysteine, an indispensable amino acid present in natural proteins, plays pivotal roles in various biological processes. Consequently, precise and selective monitoring of its concentrations is imperative. Herein, we propose a Surface-enhanced Raman Scattering (SERS) sensor for detecting L-cysteine based on the anti-aggregation of 4-mercaptobenzoic acid (4-MBA) and histidine (His) functionalized silver nanoparticles (Ag NPs). The presence of Hg2+ ions can induce the aggregation of Ag NPs@His@4-MBA due to the unique nanostructures of Ag NPs@His@4-MBA, resulting in a robust SERS intensity of 4-MBA. However, in the presence of L-cysteine, the stronger affinity between L-cysteine and Hg2+ reduces the concentration of free Hg2+, causing the dispersion of the aggregated functionalized Ag NPs and the reduction of the SERS signal intensity of 4-MBA. The developed SERS platform demonstrates excellent performance with a low detection limit of 5 nM (S/N = 3) and linear detection capabilities within the range of 0.01-100 μM for L-cysteine. Additionally, the method was successfully employed for the determination of L-cysteine in spiked serum samples, yielding recoveries ranging from 95.0 % to 108.1 % with relative standard deviations of less than 3.3 %. This study not only presents a novel approach for fabricating highly sensitive and specific SERS biosensors for biomolecule detection but also offers a significant strategy for the development and construction of SERS substrates using anti-aggregation design.

Recent Progress in the Application of Metal Organic Frameworks in Surface-Enhanced Raman Scattering Detection

Metal-organic framework (MOF) compounds are centered on metal ions or metal ion clusters, forming lattices with a highly ordered periodic porous network structure by connecting organic ligands. As MOFs have the advantages of high porosity, large specific surface area, controllable pore size, etc., they are widely used in gas storage, catalysis, adsorption, separation and other fields. SERS substrate based on MOFs can not only improve the sensitivity of SERS analysis but also solve the problem of easy aggregation of substrate nanoparticles. By combining MOFs with SERS, SERS performance is further improved, and tremendous research progress has been made in recent years. In this review, three methods of preparing MOF-based SERS substrates are introduced, and the latest applications of MOF-based SERS substrates in biosensors, the environment, gases and medical treatments are discussed. Finally, the current status and prospects of MOF-based SERS analysis are summarized.

Progress of advanced nanomaterials in diagnosis of neurodegenerative diseases

Neurodegenerative diseases (NDDs) encompass a wide range of clinically and pathologically diverse diseases characterized by progressive long-term cognitive decline, memory and function loss in daily life. Due to the lack of effective drugs and therapeutic strategies for preventing or delaying neurodegenerative progression, it is urgent to diagnose NDDs as early and accurately as possible. Nanomaterials, emerged as one of the most promising materials in the 21st century, have been widely applied and play a significant role in diagnosis and treatment of NDDs because of their remarkable properties including stability, prominent biocompatibility, unique structure, novel physical and chemical characteristics. In this review, we outlined general strategies for the application of different types of advanced materials in early and staged diagnosis of NDDs in vivo and in vitro. According to applied technology, in vivo research mainly involves magnetic resonance, fluorescence, and surface enhanced Raman imaging on structures of brain tissues, cerebral vessels and related distributions of biomarkers. In vitro research is focused on the detection of fluid biomarkers in cerebrospinal fluid and peripheral blood based on fluorescence, electrochemical, Raman and surface plasmon resonance techniques. Finally, we discussed the current challenges and future perspectives of biomarker-based NDDs diagnosis as well as potential applications regarding advanced nanomaterials.

Metal-organic frameworks based surface-enhanced Raman spectroscopy technique for ultra-sensitive biomedical trace detection

Metal-organic frameworks (MOFs) have attracted widespread interest due to their unique and unprecedented advantages in microstructures and properties. Besides, surface-enhanced Raman scattering (SERS) technology has also rapidly developed into a powerful fingerprint spectroscopic technique that can provide rapid, non-invasive, non-destructive, and ultra-sensitive detection, even down to single molecular level. Consequently, a considerable amount of researchers combined MOFs with the SERS technique to further improve the sensing performance and broaden the applications of SERS substrates. Herein, representative synthesis strategies of MOFs to fabricate SERS-active substrates are summarized and their applications in ultra-sensitive biomedical trace detection are also reviewed. Besides, relative barriers, advantages, disadvantages, future trends, and prospects are particularly discussed to give guidance to relevant researchers.

Highly catalysis amplification of MOFNd-loaded nanogold combined with specific aptamer SERS/RRS assay of trace glyphosate

A neodymium metal-organic framework (MOFNd) was prepared using 1H-pyrazole-3,5-dicarboxylic acid (H3pdc) and 2-pyrazinecarboxylic acid as ligands. Through the addition of HAuCl4 as a precursor and NaBH4 as a reducing agent, a new MOFNd-loaded nanogold (AuNPs) (Au@MOFNd) nanosol with good stability and high catalytic activity was conveniently prepared via a solvothermal-reduction method and characterized. It was found that the indicator reaction of reducing HAuCl4 by Na2SO3 to generate AuNPs was slow. Au@MOFNd strongly catalyzes this nanoreaction, and the produced AuNPs exhibit a strong resonance Rayleigh scattering (RRS) peak at 370 nm, and a strong surface-enhanced Raman scattering (SERS) peak at 1617 cm-1 with the addition of the molecular probe Victoria blue 4R (VB4r). A novel SERS/RRS di-mode quantitative analysis method for glyphosate (GLY) was established by coupling this new Au@MOFNd catalytic indicator reaction with the aptamer (Apt) reaction of GLY, with SERS and RRS detection limits of 0.02 nM and 0.3 nM, respectively. It has been applied to the analysis of soil samples with a recovery rate of 93.0%-106.5% and precision of 2.2%-4.1%, and the results were satisfactory.

A Liquid Interfacial SERS Platform on a Nanoparticle Array Stabilized by Rigid Probes for the Quantification of Norepinephrine in Rat Brain Microdialysates

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real-time quantification of trace norepinephrine (NE). The rigid molecule, 4-(thiophen-3-ylethynyl)-benzaldehyde (RP1) was designed and co-assembled at AuNPs with 4-mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in-the-field testing of NE in rat brain microdialysates following anxiety.

Exosome detection via surface-enhanced Raman spectroscopy for cancer diagnosis

As nanoscale extracellular vesicles, exosomes are secreted by various cell types, and they are widely distributed in multiple biological fluids. Studies have shown that tumor-derived exosomes can carry a variety of primary tumor-specific molecules, which may represent a novel tool for the early detection of cancer. However, the clinical translation of exosomes remains a challenge due to the requirement of large quantities of samples when enriching the cancer-related exosomes in biological fluids, the insufficiency of traditional techniques for exosome subpopulations, and the complex exosome isolation of the current commercially available exosome phenotype profiling approaches. The evolving surface-enhanced Raman scattering (SERS) technology, with properties of unique optoelectronics, easy functionalization, and the particular interaction between light and nanoscale metallic materials, can achieve sensitive detection of exosomes without large quantities of samples and multiplexed phenotype profiling, providing a new mode of real-time and noninvasive analysis for cancer patients. In the present review, we mainly discussed exosome detection based on SERS, especially SERS immunoassay. The basic structure and function of exosomes were firstly introduced. Then, recent studies using the SERS technique for cancer detection were critically reviewed, which mainly included various SERS substrates, biological modification of SERS substrates, SERS-based exosome detection, and the combination of SERS and other technologies for cancer diagnosis. This review systematically discussed the essential aspects, limitations, and considerations of applying SERS technology in the detection and analysis of cancer-derived exosomes, which could provide a valuable reference for the early diagnosis of cancer through SERS technology. STATEMENT OF SIGNIFICANCE: Surface-enhanced Raman scattering (SERS) has been applied to exosomes detection to obtain better diagnostic results. In past three years, several reviews have been published in exosome detection, which were narrowly focus on methods of exosome detection. Selection and surface functionalization of the substrate and the combination detection with different methods based on SERS will provide new strategies for the detection of exosomes. This review will focus on the above aspects. This emerging detection method is constantly evolving and contributing to the early discovery of diseases in the future.

The Progress of Label-Free Optical Imaging in Alzheimer's Disease Screening and Diagnosis

As the major neurodegenerative disease of dementia, Alzheimer's disease (AD) has caused an enormous social and economic burden on society. Currently, AD has neither clear pathogenesis nor effective treatments. Positron emission tomography (PET) and magnetic resonance imaging (MRI) have been verified as potential tools for diagnosing and monitoring Alzheimer's disease. However, the high costs, low spatial resolution, and long acquisition time limit their broad clinical utilization. The gold standard of AD diagnosis routinely used in research is imaging AD biomarkers with dyes or other reagents, which are unsuitable for in vivo studies owing to their potential toxicity and prolonged and costly process of the U.S. Food and Drug Administration (FDA) approval for human use. Furthermore, these exogenous reagents might bring unwarranted interference to mechanistic studies, causing unreliable results. Several label-free optical imaging techniques, such as infrared spectroscopic imaging (IRSI), Raman spectroscopic imaging (RSI), optical coherence tomography (OCT), autofluorescence imaging (AFI), optical harmonic generation imaging (OHGI), etc., have been developed to circumvent this issue and made it possible to offer an accurate and detailed analysis of AD biomarkers. In this review, we present the emerging label-free optical imaging techniques and their applications in AD, along with their potential and challenges in AD diagnosis.

Applications of surface-enhanced Raman spectroscopy in detection fields

Surface-enhanced Raman spectroscopy (SERS) is a Raman spectroscopy technique that has been widely used in food safety, environmental monitoring, medical diagnosis and treatment and drug monitoring because of its high selectivity, sensitivity, rapidness, simplicity and specificity in identifying molecular structures. This review introduces the detection mechanism of SERS and summarizes the most recent progress concerning the use of SERS for the detection and characterization of molecules, providing references for the later research of SERS in detection fields.

Understanding the Role of Metal-Organic Frameworks in Surface-Enhanced Raman Scattering Application

Metal-organic frameworks (MOFs), built from organic linkers and metal ions/clusters, have emerged as highly promising materials for wide applications. Combining highly porous crystalline MOFs with the surface-enhanced Raman scattering (SERS) technique can achieve unprecedented advantages of high selectivity, high sensitivity, and expedience in analysis and detection. In this critical review, the aim is to present a comprehensive review of recent advances in understanding of the roles of MOFs in MOF-SERS systems, particularly their structure-to-property correlation. Key examples are selected from representative literature to illustrate critical concepts and the MOF-based property-dependent applications are particularly emphasized. Finally, the barriers, future trends, and prospects for further advances in MOF-SERS platforms are also discussed.