Amyloid detection in neurodegenerative diseases using MOFs

Neurodegenerative diseases (amyloid diseases such as Alzheimer's and Parkinson's), stemming from protein misfolding and aggregation, encompass a spectrum of disorders with severe systemic implications. Timely detection is pivotal in managing these diseases owing to their significant impact on organ function and high mortality rates. The diverse array of amyloid disorders, spanning localized and systemic manifestations, underscores the complexity of these conditions and highlights the need for advanced detection methods. Traditional approaches have focused on identifying biomarkers using imaging techniques (PET and MRI) or invasive procedures. However, recent efforts have focused on the use of metal-organic frameworks (MOFs), a versatile class of materials known for their unique properties, in revolutionizing amyloid disease detection. The high porosity, customizable structures, and biocompatibility of MOFs enable their integration with biomolecules, laying the groundwork for highly sensitive and specific biosensors. These sensors have been employed using electrochemical and photophysical techniques that target amyloid species under neurodegenerative conditions. The adaptability of MOFs allows for the precise detection and quantification of amyloid proteins, offering potential advancements in early diagnosis and disease management. This review article delves into how MOFs contribute to detecting amyloid diseases by categorizing their uses based on different sensing methods, such as electrochemical (EC), electrochemiluminescence (ECL), fluorescence, Förster resonance energy transfer (FRET), up-conversion luminescence resonance energy transfer (ULRET), and photoelectrochemical (PEC) sensing. The drawbacks of MOF biosensors and the challenges encountered in the field are also briefly explored from our perspective.

Progress on the reaction-based methods for detection of endogenous hydrogen sulfide

Hydrogen sulfide (H₂S) is a biologically signaling molecule that mediates a wide range of physiological functions, which is frequently misregulated in numerous pathological processes. As such, measurement of H₂S holds great attention due to its unique physiological and pathophysiological roles. Currently, a variety of methods based on the H₂S-involved reactions have been reported for detection of endogenous H₂S, bearing the advantages of good specificity and high sensitivity. This review describes in detail the types of reactions, their mechanisms, and their applications in biological research, thus hopefully providing some guidelines to the researchers in this field for further investigation.

Emerging analytical tools for the detection of the third gasotransmitter H2S, a comprehensive review

BACKGROUND

Hydrogen sulfide (H2S) is currently considered among the endogenously produced gaseous molecules that exert various signaling effects in mammalian species. It is the third physiological gasotransmitter discovered so far after NO and CO. H2S was originally ranked among the toxic gases at elevated levels to humans. Currently, it is well-known that, in the cardiovascular system, H2S exerts several cardioprotective effects including vasodilation, antioxidant regulation, inhibition of inflammation, and activation of anti-apoptosis. With an increasing interest in monitoring H2S, the development of analysis methods should now follow.

AIM OF REVIEW

This review stages special emphasis on the several analytical technologies used for its determination including spectroscopic, chromatographic, and electrochemical methods. Advantages and limitations with regards to the application of each technique are highlighted with special emphasis on its employment for H2S in vivo measurement i.e., biofluids, tissues.

KEY SCIENTIFIC CONCEPTS AND IMPORTANT FINDINGS OF REVIEW

Fluorescence methods applied for H2S measurement offer an attractive non-invasive and promising approach in addition to its selectivity, however they cannot be considered as H2S-specific probes. On the other hand, colorimetric assays are among the most common methods used for in vitro H2S detection, albeit their employment in vivo H2S measurement has not yet been possible . Separation techniques such as gas or liquid chromatography offer higher selectivity compared to direct spectrophotometric or fluorescence methods especially for suitable for endpoint H2S measurements i.e. plasma or tissue samples. Despite all the developed analytical procedures used for H2S determination, the need for highly selective, much work should be devoted to resolve all the pitfalls of the current methods.

Sensing and Bioimaging of the Gaseous Signaling Molecule Hydrogen Sulfide by Near-Infrared Fluorescent Probes

A fluorescent probe for the monitoring of H₂S levels in living cells and organisms is highly desirable. In this regard, near-infrared (NIR) fluorescent probes have emerged as a promising tool. NIR-I and NIR-II probes have many significant advantages; for instance, NIR light penetrates deeper into tissue than light at visible wavelengths, and it causes less photodamage during biosample analysis and less autofluorescence, enabling higher signal-to-background ratios. Therefore, it is expected that fluorescent probes having emission in the NIR region are more suitable for in vivo imaging. Consequently, a considerable increase in reports of new H₂S-responsive NIR fluorescent probes appeared in the literature. This review highlights the advances made in developing new NIR fluorescent probes aimed at the sensitive and selective detection of H₂S in biological samples. Their applications in real-time monitoring of H₂S in cells and in vivo for bioimaging of living cells/animals are emphasized. The selection of suitable dyes for designing NIR fluorescent probes, along with the principles and mechanisms involved for the sensing of H₂S in the NIR region, are described. The discussions are focused on small-molecule and nanomaterials-based NIR probes.

Pyrene derivative-functionalized mesoporous silica-Cu2+ hybrid ensemble for fluorescence "turn-on" detection of H2S and logic gate application in aqueous media

The ensemble system PyH-SBA-15-Cu²⁺ was obtained via coordination interaction of pyrene derivative-functionalized mesoporous SBA-15 and Cu²⁺, and applied for the selective and sensitive detection of H₂S over pH 6.0-12.0 in aqueous media. The sensing strategy was designed on the basis of the H₂S-induced dissolution of Cu²⁺ from PyH-SBA-15-Cu²⁺. Cu²⁺ has good binding affinity to N atoms in PyH-SBA-15; therefore, the organic-inorganic hybrid ensemble PyH-SBA-15-Cu²⁺ was formed, which is nonfluorescent in aqueous solution because of the Cu²⁺-promoted emission quenching of PyH-SBA-15. The addition of H₂S induces the dissolution of PyH-SBA-15-Cu²⁺ by the formation of stable CuS, thereby producing fluorescence revival of PyH-SBA-15. The correlative "turn-on" fluorescence signals of this ensemble system are linearly proportional to [H₂S] in the concentration region of 0-1.0 × 10^-4 M, showing a low detection limit of 3.7 × 10^-7 M. Other common anions do not induce distinct fluorescence changes. When using the fluorescence intensity signal changes of PyH-SBA-15 as outputs and Cu²⁺ and S^2- as inputs, PyH-SBA-15 can act as an XNOR logic gate.

HS- facilitated sulfur pyran realizing hydrogen sulfide detection and imaging in HepG2 cells and chlorella

The new carbazole-based fluorescent probe CA-1 was designed and synthesized for the high selective detection of H₂S based on HS^- facilitated sulfur pyran resulting in UV-Vis and fluorescent spectra changes. At the same time, the probe showed good sensitivity to the detection of H₂S with a low detection limit of 0.16 μM. The detection process can be monitored by naked eye: with the addition of H₂S, the probe system changed from yellow to pink. Importantly, the probe could be applied in monitoring H₂S in HepG2 cells and Chlorella. These results indicate that CA-1 can be used as a promising fluorescent probe for the detection of H₂S in situ.

Rapid "turn-on" photoluminescence detection of bisulfite in wines and living cells with a formyl bearing bis-cyclometalated Ir(iii) complex

A new photoluminescence (PL) probe based on a formyl bearing bis-cyclometalated Ir(iii) complex, [Ir(ppy)2phen-CHO]+PF6- (1), is synthesized and applied to the selective detection of a bisulfite anion (HSO3-). Probe 1 is prepared using 2-phenylpyridine (ppy) as the C^N main ligand and 1,10-phenanthroline-5-carboxaldehyde (phen-CHO) as the N^N ancillary ligand. Probe 1 displayed excellent selective PL enhancement in response to HSO3- in acetic acid-sodium acetate buffer solution (pH = 5.0). The increase of PL signal is directly proportional to the concentration of HSO3- in the range of 2 μM to 45 μM with a detection limit of 0.9 μM using 50 μM probe 1 and in the range of 0.5 μM to 6 μM with a detection limit of 0.3 μM using 10 μM probe 1. More importantly, probe 1 can respond to HSO3- rapidly within 40 s. Furthermore, probe 1 was successfully applied to detect HSO3- in real white wines and the bioimaging of HSO3- in living cells. The superior properties of probe 1 make it of great potential use for studying the effects of HSO3- in other biosystems.

Living cell imaging and sensing of hydrogen sulfide using high-efficiency fluorescent Cu-doped carbon quantum dots

A simple Cu-doped carbon quantum dot-based fluorescent sensor for H₂S sensing and intracellular bioimaging was constructed.

A circular dichroism sensor for selective detection of Cd2+ and S2- based on the in-situ generation of chiral CdS quantum dots

We demonstrate an advance in the fabrication of circular dichroism (CD) sensors for detection of Cd²⁺ and S^2- based on chiral CdS quantum dots (QDs) generated by a facile in-situ reaction. The chiral quantum dots are generated in solutions composed of Cd²⁺, S^2-, cysteamine (CA) and L-penicillamine (L-PA), with the number of the generated particles limited by either the Cd²⁺ or S^2- concentration. We show that the magnitude of the CD signal produced by the QDs is linearly related to the initial concentration of Cd²⁺ and S^2-, with excellent selectivity over other ions. Our sensor functions over concentration ranges of 65-200μM and 7-125μM with detection limits of 59.7 and 1.6μM for Cd²⁺ and S^2-, respectively. The sensor is applied in real water samples with results comparing favorably with those obtained from ICP-OES (for Cd²⁺) and HPLC (for S^2-).

Highly sensitive and selective colorimetric detection of sulphide using Ag–Au nanoalloys: a DFT study

For the colorimetric detection of S, SH, cysteine, and H₂S, the sensitivity of Ag–Au nanoalloy is better than pure Ag cluster, and both of them possess high selectivity for the detection of S.

A novel scattering switch-on detection technique for target-induced plasmon-coupling based sensing by single-particle optical anisotropy imaging

A novel scattering switch-on detection technique by using flash-lamp polarization darkfield microscopy (FLPDM) has been proposed for target-induced plasmon-coupling based sensing in homogeneous solution.

Metal oxides and metal salt nanostructures for hydrogen sulfide sensing: mechanism and sensing performance

Metal oxides and metal salt nanostructures for hydrogen sulfide sensing based on conductivity response.