Chuang, H.-S. | Search bioRxiv

bioRxiv2024

Immunojanus Particles for low-volume and isolation-free unlabeled characterization of small Extracellular Vesicle in biofluids: Characterization of disease type by surface marker profiling

Small extracellular vesicles (sEVs) are vital for cellular communication and serve as critical biomarker carriers for diseases such as cancer. However, quantifying and profiling sEV surface markers presents significant challenges due to the low concentration of specific sEV-bound proteins and interference by more abundant dispersed proteins. This paper presents Immunojanus Particles (IJPs), a new method that enables the direct detection of sEVs in less than an hour without isolation. The design of IJPs incorporates fluorescent and non- fluorescent halves, utilizing rotational Brownian motion to detect captured sEVs through the change in the blinking rate, without interference from the smaller dispersed proteins. We demonstrate a detection limit of 2E5 sEVs/mL with low sample volumes and the capability to characterize sEVs directly from plasma, serum, cell culture media, and urine. In a small pilot study involving 87 subjects, including individuals with colorectal cancer, pancreatic ductal adenocarcinoma, glioblastoma, Alzheimers disease, and healthy controls, our method accurately identified the type of disease with a high 0.90-0.99 AUC in a blind setting. Compared with an orthogonal ultracentrifugation plus surface plasmon resonance (UC+SPR) method that requires about 24 hours, the sensitivity and dynamic range of IJP are better by 2 logs.

scientific communication and education↗

bioRxiv2019

Caenorhabditis elegans Exhibits Positive Gravitaxis

Whether or not the micro swimmer Caenorhabditis elegans senses and respond to gravity is unknown. We find that C. elegans aligns its swimming direction with that of the gravity vector (positive gravitaxis). When placed in an aqueous solution that is denser than the animals, they still orient downwards, indicating that non-uniform mass distribution and/or hydrodynamic effects are not responsible for animals downward orientation. Paralyzed worms and worms with globally disrupted sensory cilia do not change orientation as they settle in solution, indicating that gravitaxis is an active behavior that requires gravisensation. Other types of sensory driven orientation behaviors cannot explain our observed downward orientation. Like other neural behaviors, the ability to respond to gravity declines with age. Our study establishes gravitaxis in the micro swimmer C. elegans and suggests that C. elegans can be used as a genetically tractable system to study molecular and neural mechanisms of gravity sensing and orientation.\n\nSignificance StatementUnderstanding how animals respond to gravity is not only of fundamental scientific interest, but has clinical relevance, given the prevalence of postural instability in aged individuals. Determining whether C. elegans responds to gravity is important for mechanistic studies of gravity sensing in an experimentally tractable animal, for a better understanding of nematode ecology and evolution, and for studying biological effects of microgravity. Our experiments, which indicate that C. elegans senses and responds to gravity, set the stage for mechanistic studies on molecular mechanisms of gravity sensing.

neuroscience↗