ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
Softer membranes make pyrene nanovesicles 14 times more sensitive to water pressure
Institute of Science Tokyo researchers made pyrene nanovesicles whose softest version reads water pressure 14 times more sensitively than the stiffest. They pitch the vesicles for microscopic pressure measurements in water and living tissue, where existing molecular sensors struggle.
The Scientist · Science desk
What happened
- Pressure pushes pyrene molecules in the vesicle membrane together into excimers that glow near 500 nm, and the ratio of that glow to the 380 nm monomer signal tracks the pressure.
- The team set membrane stiffness by varying the concentration of the crosslinker EDC, keeping the vesicles near 100 nm in diameter.
- The work, led by Hayato Mizuno and Yasutaka Anraku at Institute of Science Tokyo with Gaku Fukuhara of Kyushu University, appears in ACS Applied Nano Materials.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- decision A lab has to fix membrane stiffness to suit its instrument before it starts: soft vesicles for a two-colour intensity ratio, stiff ones for a lifetime microscope.
- capability Because pyrene loading also raises sensitivity, users get a second setting besides crosslinking and can adjust the response without changing particle size.
- constraint The reported characterization stops at 0.1 to 50 MPa, so any use at pressures outside that window would first need its own calibration.
The stiffness effect is large. The softest membranes measured 7.3 pN/nm and gave an excimer-to-monomer sensitivity of 0.28 per MPa. The stiffest measured 39 pN/nm and gave 0.02 per MPa, both over 0.1 to 50 MPa [6]. Stiffness rose about 5.3-fold from one end of the series to the other [13], and ratio sensitivity fell 14-fold [12]. The design is clean on one point: crosslinker dose was the variable, and vesicle diameter stayed near 100 nm throughout [4], so particle size cannot account for the gap.
The lifetime readout turned up while the team was studying how pyrene affects the vesicles' excited-state dynamics [8]. Fluorescence lifetime is how long a molecule stays in its excited state. On that measure the ordering reversed, with stiffer membranes giving the larger change as pressure rose [8]. If the stiffest vesicles' slope is constant across the window, their lifetime would fall by about 4.5 ns between 0.1 and 50 MPa [15]. The authors describe them as good candidates for probes in fluorescence lifetime imaging microscopy, or FLIM [9].
"An important aspect of our platform is that it does not rely on a single sensing mechanism," Mizuno said. "By changing the membrane stiffness, we can access different fluorescence readouts, providing flexibility in how the pressure is measured." [11]
I think the stiffness result holds up as chemistry. The claim about reaching hard places is, for now, a proposal. According to the phys.org report, existing molecular pressure sensors suffer from poor water solubility, weak sensitivity in the megapascal range or trouble operating in biological settings [2]. PICsomes self-assemble in water from oppositely charged polymers [3], so the solubility problem is handled by design. The report says the findings open pressure-dependent phenomena in diverse inaccessible environments to study, and it names the deep ocean and living tissue as places where hydrostatic pressure matters [14]. The results it reports are the vesicles' responses across 0.1 to 50 MPa [6]. It does not describe a measurement inside a cell, a tissue sample or seawater.
What to watch
- Tests of whether the excimer-to-monomer ratio stays tied to pressure when temperature or salt concentration changes, as both would inside a biological sample.
- A first measurement with Pyr-PICsomes inside living cells, tissue or pressurized seawater, using either the ratio or the FLIM readout.
- Full lifetime curves for the stiff vesicles, since a response that bends within 0.1 to 50 MPa would change the roughly 4.5 ns span estimated from the slope.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence50
- Adoption
- Insufficient
- Hype gap+25
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The research team was led by assistant professor Hayato L. Mizuno and associate professor Yasutaka Anraku of Institute of Science Tokyo, with professor Gaku Fukuhara of Kyushu University; the study is published in ACS Applied Nano Materials.
- [2]
Existing molecular sensors for hydrostatic pressure face limitations such as poor water solubility, insufficient sensitivity in the megapascal range or operational difficulties in biological settings.
- [3]
PICsomes are polymer-based vesicles that self-assemble in water from oppositely charged polymers.
- [4]
The researchers chemically crosslinked PICsome membranes with EDC, using the EDC concentration to adjust membrane stiffness while keeping vesicle size at approximately 100 nm in diameter, then incorporated pressure-sensitive pyrene probes into the membrane.
- [5]
Separated pyrene molecules fluoresce mainly as monomers at around 380 nm; under hydrostatic pressure neighbouring pyrenes are brought closer and form excimers emitting at around 500 nm, so the excimer-to-monomer fluorescence ratio measures hydrostatic pressure.
- [6]
The softest vesicles, stiffness 7.3 pN/nm, showed the largest change in excimer-to-monomer ratio across 0.1-50 MPa, with sensitivity 0.28 MPa^-1, compared with 0.02 MPa^-1 for the stiffest vesicles at 39 pN/nm.
- [7]
More pyrene molecules led to greater excimer formation and higher pressure-detection sensitivity.
- [8]
While investigating pyrene's influence on the excited-state dynamics of Pyr-PICsomes, the researchers identified fluorescence lifetime (how long a fluorescent molecule remains in an excited state) as another pressure readout; stiffer vesicles showed stronger lifetime changes as pressure increased, and the stiffest showed a lifetime sensitivity of -0.09 ns/MPa between 0.1 and 50 MPa.
- [9]
The stiff vesicles' lifetime properties make them good candidates for fluorescence lifetime imaging microscopy (FLIM) probes.
- [10]
The findings suggest membrane stiffness should be tailored depending on whether hydrostatic pressure is measured through fluorescence intensity or FLIM.
- [11]
"An important aspect of our platform is that it does not rely on a single sensing mechanism. By changing the membrane stiffness, we can access different fluorescence readouts, providing flexibility in how the pressure is measured."
- [12]
The softest vesicles' ratio sensitivity was 14 times that of the stiffest.
- [13]
Membrane stiffness rose about 5.3-fold from the softest to the stiffest vesicles.
- [14]
The findings enable the investigation of hydrostatic pressure-dependent phenomena in diverse inaccessible environments; measuring hydrostatic pressure is important in environments ranging from the deep ocean to living tissues.
ReportedInsufficientSource: phys.org report2 sources— create a free account to open themView cited source - [15]
If the stiffest vesicles' lifetime slope is constant across the range, their fluorescence lifetime would fall by about 4.5 ns between 0.1 and 50 MPa.
Sources
1 independent publisher whose own reporting we read for this story.
Topics and entities
Follow any of these and your For You feed starts watching them — no settings page required.
Topics
Entities
- Institute of Science TokyoFollow
- Kyushu UniversityFollow
- Hayato L. MizunoFollow
- Yasutaka AnrakuFollow
- Gaku FukuharaFollow
- ACS Applied Nano MaterialsFollow
- Pyr-PICsomeFollow