Photo-induced leaching behaviors and biodegradability of dissolved organic matter from microplastics and terrestrial-sourced particles.

Recent studies have increasingly focused on the occurrence of plastic leachate and its impacts on aquatic ecosystems. Nonetheless, the environmental fate of this leachate in the presence of abundant natural organic matter (NOM)-a typical scenario in environments contaminated with plastics-remains underexplored. This study investigates the photo-induced leaching behaviors of dissolved organic matter (DOM) from terrestrial-sourced particles (forest soil and leaf litter) and microplastics (MPs), specifically polystyrene (PS) and polyvinyl chloride (PVC), over a two-week period. We also examined the biodegradability and spectroscopic characteristics of the leached DOM from both sources. Our results reveal that DOM from microplastics (MP-DOM) demonstrates more persistent leaching behavior compared to terrestrial-derived DOM, even with lesser quantities per unit of organic carbon. UV irradiation was found to enhance DOM leaching across all particle types. However, the photo-induced leaching behaviors of fluorescent components varied with the particle type. The MP group exhibited a broader range and higher biodegradability (ranging from 19.7% to 61.6%) compared to the terrestrial-sourced particles (ranging from 3.7% to 16.5%). DOM leached under UV irradiation consistently showed higher biodegradability than that under dark conditions. Furthermore, several fluorescence characteristics of DOM, such as the protein/phenol-like component (%C2), terrestrial humic-like component (%C3), and humification index (HIX)-traditionally used to indicate the biodegradability of natural organic matter-were also effective in assessing MP-DOM (with correlation coefficients R2 = 0.6055 (p = 0.003), R2 = 0.5389 (p = 0.007), and R2 = 0.4640 (p = 0.015), respectively). This study provides new insights into the potential differences in environmental fate between MP-DOM and NOM in aquatic environments heavily contaminated with MPs.

Structure-activity relationship analysis of activity-based probes targeting HTRA family of serine proteases.

High temperature requirement A serine proteases (HTRA) are ubiquitously expressed and participate in protein quality control and cellular stress responses. They are linked to several clinical illnesses, including bacterial infection, cancer, age-related macular degeneration, and neurodegenerative diseases. In addition, several recent studies have revealed HTRAs as important biomarkers and potential therapeutic targets, necessitating the development of an effective detection method to evaluate their functional states in various disease models. We developed a new series of HTRA-targeting activity-based probes with enhanced subtype selectivity and reactivity. In conjunction with our previously developed tetrapeptide probes, we established the structure-activity relationship of the new probes for different HTRA subtypes. Our probes are cell-permeable and have potent inhibitory effects against HTRA1 and HTRA2, making them valuable for identifying and validating HTRAs as an important biomarker.

A fluorescent molecular rotor for the in situ imaging of latent fingerprints.

Efficient techniques for developing latent fingerprints are invaluable resources to solve crimes. In this work, we developed a fluorescent molecular rotor probe that responds to hydrophobic and viscous environments and visualizes latent fingerprints with level 3 details. We believe that the simple and convenient features of LFP-1 will benefit forensic practice.

Recent Advances in Organelle-Targeted Fluorescent Probes.

Recent advances in fluorescence imaging techniques and super-resolution microscopy have extended the applications of fluorescent probes in studying various cellular processes at the molecular level. Specifically, organelle-targeted probes have been commonly used to detect cellular metabolites and transient chemical messengers with high precision and have become invaluable tools to study biochemical pathways. Moreover, several recent studies reported various labeling strategies and novel chemical scaffolds to enhance target specificity and responsiveness. In this review, we will survey the most recent reports of organelle-targeted fluorescent probes and assess their general strategies and structural features on the basis of their target organelles. We will discuss the advantages of the currently used probes and the potential challenges in their application as well as future directions.

Activity-Based Probes for the High Temperature Requirement A Serine Proteases.

The high temperature requirement A (HTRA) family of serine proteases mediates protein quality control. These proteins process misfolded proteins in several diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). While their structures and activation mechanisms have been studied, the precise details of the regulation of their activity under physiological conditions have not been completely elucidated, partly due to the lack of suitable chemical probes. In the present study, we developed novel activity-based probes (ABPs) targeting the HTRAs and demonstrated their utility in the monitoring and quantification of changes in enzyme activity in live cells. Using our probes, we found the activity of HTRA1 to be highly elevated in an AD-like cell-based model. We also observed the active HTRA2 in live cells by using a mitochondrion-targeted probe. We believe that our probes can serve as a useful tool to study the role of human HTRAs in neurodegenerative diseases.

Development of a smart activity-based probe to detect subcellular activity of asparaginyl endopeptidase in living cells.

We developed a smart activity-based probe that detects the activity of asparaginyl endopeptidase (AEP) in live cells to monitor the dynamics of enzyme regulation. The newly designed probe generated a turn-on fluorescence signal in response to the activity of AEP in living cells without compromising the labelling efficiency or selectivity. Our probe closely reflected the enzyme activity in its native state, detecting subcellular AEP activity in colon cancer cells and neuronal cells.

Noninvasive imaging of radiolabeled exosome-mimetic nanovesicle using (99m)Tc-HMPAO.

Exosomes known as nano-sized extracellular vesicles attracted recent interests due to their potential usefulness in drug delivery. Amid remarkable advances in biomedical applications of exosomes, it is crucial to understand in vivo distribution and behavior of exosomes. Here, we developed a simple method for radiolabeling of macrophage-derived exosome-mimetic nanovesicles (ENVs) with (99m)Tc-HMPAO under physiologic conditions and monitored in vivo distribution of (99m)Tc-HMPAO-ENVs using SPECT/CT in living mice. ENVs were produced from the mouse RAW264.7 macrophage cell line and labeled with (99m)Tc-HMPAO for 1 hr incubation, followed by removal of free (99m)Tc-HMPAO. SPECT/CT images were serially acquired after intravenous injection to BALB/c mouse. When ENVs were labeled with (99m)Tc-HMPAO, the radiochemical purity of (99m)Tc-HMPAO-ENVs was higher than 90% and the expression of exosome specific protein (CD63) did not change in (99m)Tc-HMPAO-ENVs. (99m)Tc-HMPAO-ENVs showed high serum stability (90%) which was similar to that in phosphate buffered saline until 5 hr. SPECT/CT images of the mice injected with (99m)Tc-HMPAO-ENVs exhibited higher uptake in liver and no uptake in brain, whereas mice injected with (99m)Tc-HMPAO showed high brain uptake until 5 hr. Our noninvasive imaging of radiolabeled-ENVs promises better understanding of the in vivo behavior of exosomes for upcoming biomedical application.

Combined expression of miR-122a, miR-1, and miR-200b can differentiate degraded RNA samples from liver, pancreas, and stomach.

The effect of RNA degradation on the diagnostic utility of microRNA has not been systematically evaluated in clinical samples. We asked if the microRNA profile is preserved in degraded RNA samples derived from mouse and human tissue. We selected tissue-specific microRNA candidates from published human microarray data, and validated them using quantitative reverse transcription polymerase chain reaction (QRTPCR) analyses on flash-frozen, normal mouse liver, pancreas, and stomach tissue samples. MiR-122a, miR-1, and miR-200b were identified as tissue-specific, and the 3-microRNA-based QRTPCR could predict the tissue origin for mouse tissue samples that were left at room temperature for 2 h with an accuracy of 91.7%. When we applied this 3-microRNA predictor to clinical specimens with various degree of RNA degradation, the predictor differentiated degraded RNA samples from liver, pancreas, and stomach with an accuracy of 90% (26/29). Expression levels of miR-122a, miR-1, and miR-200b were modestly changed after the extended (2-4 h) storage at room temperature, but the magnitudes of expression changes were small compared to the expression differences between various tissues of origin. This proof-of-principle study demonstrates that RNA degradation due to extended storage at room temperature does not affect the predictive power of tissue-specific microRNA QRTPCR predictor.