Structure-specific amyloid precipitation in biofluids

Self-assembled peptide microtubes (SPMTs)/SnO2 sensors for enhanced room-temperature gas detection under visible light illumination

Nitrogen dioxide (NO2) is an important contaminant that poses a severe threat to environmental sustainability. Traditional inorganic NO2 gas detectors are generally used under harsh operating conditions and employ environmentally unfriendly resources, thus preventing widespread practical applications. Herein, self-assembled peptide microtubes (SPMTs) are combined with SnO2 nanoparticles (NPs) to develop a bioinspired NO2 gas sensor. The sensor incorporated with SPMTs exhibits a lower resistance and a stronger response under visible light irradiation. Under exposure to 4.7-mW/cm2 white light irradiation, the device exhibits a response of 412 and a resistance of only 97 MΩ, contrast to 318 and 340 MΩ for the bare SnO2-based counterpart under the same test conditions. This work exemplifies the feasibility of using bioinspired approach employing peptides self-assembly strategy to engineer comprehensive pollution detectors, potentially enabling development in the environmentally friendly sensing field.

Utilization of a Branched Late-Stage Clickable Biotinylated Chassis on the Example of a Pittsburgh B Analogue

Biotinylation is probably the most frequent and practically useful modification of molecules to facilitate selective and highly affine binding to (strept)avidin for immobilization, enrichment, and purification for further (bio)chemical or (bio)physical investigations. We present a protecting-group-free synthesis of a branched biotin bis-azide that enables dual-payload late-stage functionalization with arbitrary alkynes via click chemistry. Utility of the chassis is briefly showcased on the example of a valuable Pittsburgh B analogue, which binds pathological protein aggregates, commonly found in neurodegenerative diseases.

Improved Imaging Surface for Quantitative Single-Molecule Microscopy

Preventing nonspecific binding is essential for sensitive surface-based quantitative single-molecule microscopy. Here we report a much-simplified RainX-F127 (RF-127) surface with improved passivation. This surface achieves up to 100-fold less nonspecific binding from protein aggregates compared to commonly used polyethylene glycol (PEG) surfaces. The method is compatible with common single-molecule techniques including single-molecule pull-down (SiMPull), super-resolution imaging, antibody-binding screening and single exosome visualization. This method is also able to specifically detect alpha-synuclein (α-syn) and tau aggregates from a wide range of biofluids including human serum, brain extracts, cerebrospinal fluid (CSF) and saliva. The simplicity of this method further allows the functionalization of microplates for robot-assisted high-throughput single-molecule experiments. Overall, this simple but improved surface offers a versatile platform for quantitative single-molecule microscopy without the need for specialized equipment or personnel.

Self-assembled peptide nanotubes (SPNTs)/SnO2nanocomposites for high-performance NO2sensing at room temperature

Nitrogen dioxide (NO2) is a major pollutant that poses significant risks to sustainable human life. As a result, a growing focus has been placed on the development of highly selective and sensitive gas sensors for NO2. Traditional cutting-edge non-organic NO2gas detectors often necessitate stringent production conditions and potentially harmful materials, which are not environmentally friendly, and these shortcomings have limited their widespread practical use. To overcome these challenges, we synthesized self-assembled peptide nanotubes (SPNTs) through a molecular self-assembly process. The SPNTs were then combined with SnO2in varying proportions to construct NO2gas sensors. The design of this sensor ensured efficient electron transfer and leverage the extensive surface area of the SPNTs for enhanced gas adsorption and the effective dispersion of SnO2nanoparticles. Notably, the performance of the sensor, including its sensitivity, response time, and recovery rate, along with a lower detection threshold, could be finely tuned by varying the SPNTs content. This approach illustrated the potential of bioinspired methodologies, using peptide self-assemblies, to develop integrated sensors for pollutant detection, providing a significant development in environmentally conscious sensor technology.

Highly tunable bimane-based fluorescent probes: design, synthesis, and application as a selective amyloid binding dye

Small molecule fluorescent probes are indispensable tools for a broad range of biological applications. Despite many probes being available, there is still a need for probes where photophysical properties and biological selectivity can be tuned as desired. Here, we report the rational design and synthesis of a palette of fluorescent probes based on the underexplored bimane scaffold. The newly developed probes with varied electronic properties show tunable absorption and emission in the visible region with large Stokes shifts. Probes featuring electron-donating groups exhibit rotor effects that are sensitive to polarity and viscosity by "intramolecular charge transfer" (ICT) and twisted intramolecular charge transfer (TICT) mechanisms, respectively. These properties enable their application as "turn-on" fluorescent probes to detect fibrillar aggregates of the α-synuclein (αS) protein that are a hallmark of Parkinson's disease (PD). One probe shows selective binding to αS fibrils relative to soluble proteins in cell lysates and amyloid fibrils of tau and amyloid-β. Finally, we demonstrate the diagnostic potential of the probe in selectively detecting αS fibrils amplified from PD with dementia (PDD) patient samples.

Advances in targeted tracking and detection of soluble amyloid-β aggregates as a biomarker of Alzheimer's disease

Misfolding and aggregation of amyloid-β (Aβ) peptides are key hallmarks of Alzheimer's disease (AD). With accumulating evidence suggesting that different Aβ species have varied neurotoxicity and implications in AD development, the discovery of affinity ligands and analytical approaches to selective distinguish, detect, and monitor Aβ becomes an active research area. Remarkable advances have been achieved, which not only promote our understanding of the biophysical chemistry of the protein aggregation during neurodegeneration, but also provide promising tools for early detection of the disease. In view of this, we summarize the recent progress in selective and sensitive approaches for tracking and detection of Aβ species. Specific attentions are given to soluble Aβ oligomers, due to their crucial roles in AD development and occurrence at early stages. The design principle, performance of targeting units, and their cooperative effects with signal reporters for Aβ analysis are discussed. The applications of the novel targeting probes and sensing systems for dynamic monitoring oligomerization, measuring Aβ in biosamples and in vivo imaging in brain are summarized. Finally, the perspective and challenges are discussed regarding the future development of Aβ-targeting analytical tools to explore the unknown field to contribute to the early diagnosis and treatment of AD.

Adaptive and Ultrahigh-Affinity Recognition in Water by Sulfated Conjugated Corral[5]arene

The pursuit of synthetic receptors with high binding affinities has long been a central focus in supramolecular chemistry, driven by their significant practical relevance in various fields. Despite the numerous synthetic receptors that have been developed, most exhibit binding affinities in the micromolar range or lower. Only a few exceptional receptors achieve binding affinities exceeding 109  M-1 , and their substrate scopes remain rather limited. In this context, we introduce SC[5]A, a conjugated corral-shaped macrocycle functionalized with ten sulfate groups. Owing to its deep one-dimensional confined hydrophobic cavity and multiple sulfate groups, SC[5]A displays an extraordinarily high binding strength of up to 1011  M-1 towards several size-matched, rod-shaped organic dications in water. Besides, its conformation exhibits good adaptability, allowing it to encapsulate a wide range of other guests with diverse molecular sizes, shapes, and functionalities, exhibiting relatively strong affinities (Ka =106 -108  M-1 ). Additionally, we've explored the preliminary application of SC[5]A in alleviating blood coagulation induced by hexadimethrine bromide in vitro and in vivo. Therefore, the combination of ultrahigh binding affinities (towards complementary guests) and adaptive recognition capability (towards a wide range of functional guests) of SC[5]A positions it as exceptionally valuable for numerous practical applications.

Artificial intelligence-coupled plasmonic infrared sensor for detection of structural protein biomarkers in neurodegenerative diseases

Diagnosis of neurodegenerative disorders (NDDs) including Parkinson's disease and Alzheimer's disease is challenging owing to the lack of tools to detect preclinical biomarkers. The misfolding of proteins into oligomeric and fibrillar aggregates plays an important role in the development and progression of NDDs, thus underscoring the need for structural biomarker-based diagnostics. We developed an immunoassay-coupled nanoplasmonic infrared metasurface sensor that detects proteins linked to NDDs, such as alpha-synuclein, with specificity and differentiates the distinct structural species using their unique absorption signatures. We augmented the sensor with an artificial neural network enabling unprecedented quantitative prediction of oligomeric and fibrillar protein aggregates in their mixture. The microfluidic integrated sensor can retrieve time-resolved absorbance fingerprints in the presence of a complex biomatrix and is capable of multiplexing for the simultaneous monitoring of multiple pathology-associated biomarkers. Thus, our sensor is a promising candidate for the clinical diagnosis of NDDs, disease monitoring, and evaluation of novel therapies.

Construction of a multifunctional peptide nanoplatform for nitric oxide release and monitoring and its application in tumor-bearing mice

As a "star molecule", nitric oxide (NO) either promotes or inhibits many physiological processes depending on its concentration. The in situ generation and monitoring of therapeutic gas molecules has been a problem that many researchers have been working to address due to the stochastic nature of gas molecule movement. There are still relatively few studies using short peptides as NO storage systems, and there are still challenges in monitoring NO release in situ with real-time imaging over long periods of time. In this work, a morphologically transformable NO release, diagnosis and treatment integrated multifunctional nanoplatform was fabricated. A new NO-activated probe (DPBTD) with emission in the first near infrared (NIR-I) region was encapsulated into the hydrophobic domains of Ac-KLVFFAL-NH₂ peptide derivatives as a biosensor for NO release. Peptide scaffolds were endowed with the capacity of controlled NO release by the introduction of NO donor (organic nitrates). Interestingly, morphology of the nanoplatform could be transformed from one-dimensional (1D) nanowires to two-dimensional (2D) nanosheets via nanorods transition state under tip sonication, which was allowed for better cell uptake. Eventually, this nanocarrier was used for stimuli-responsive NO release, real-time imaging and treatment in tumor tissues of 4T1 tumor-bearing mice. This strategy expands the application potential of peptide-based nanomaterials and provides ideas for monitoring the progress of gas-mediated cancer therapy.

Role of conformational dynamics in pathogenic protein aggregation

The accumulation of pathogenic protein oligomers and aggregates is associated with several devastating amyloid diseases. As protein aggregation is a multi-step nucleation-dependent process beginning with unfolding or misfolding of the native state, it is important to understand how innate protein dynamics influence aggregation propensity. Kinetic intermediates composed of heterogeneous ensembles of oligomers are frequently formed on the aggregation pathway. Characterization of the structure and dynamics of these intermediates is critical to the understanding of amyloid diseases since oligomers appear to be the main cytotoxic agents. In this review, we highlight recent biophysical studies of the roles of protein dynamics in driving pathogenic protein aggregation, yielding new mechanistic insights that can be leveraged for design of aggregation inhibitors.