5 research outputs found
Gradient Mechanical Properties Facilitate <i>Arabidopsis</i> Trichome as Mechanosensor
It has been reported that <i>Arabidopsis thaliana</i> leaf trichome can act as a mechanosensory
switch, transducing mechanical stimuli into physiological signals,
mainly through a buckling instability to focus external force (e.g.,
exerted by insects) on the base of trichome. The material and structural
properties of trichomes remain largely unknown in this buckling instability.
In this report, we mainly focused on material standpoint to explore
the possible mechanism facilitating the buckling instability. We observed
that the Young’s modulus of trichome cell wall decreased gradually
from branch to the base region of trichome. Interestingly, we also
found a corresponding decline of calcium concentration on the trichome
cell wall. Results of finite element method (FEM) simulation suggested
that such a gradient distribution of Young’s modulus significantly
promotes force focusing and buckling instability on the base of trichome.
It is indicated that <i>Arabidopsis</i> trichome has developed
into an active mechanosensor benefiting from gradient cell wall mechanical
properties
Patterning Cellular Alignment through Stretching Hydrogels with Programmable Strain Gradients
The graded mechanical properties
(e.g., stiffness and stress/strain)
of excellular matrix play an important role in guiding cellular alignment,
as vital in tissue <i>reconstruction with proper functions</i>. Though various methods have been developed to engineer a graded
mechanical environment to study its effect on cellular behaviors,
most of them failed to distinguish stiffness effect from stress/strain
effect during mechanical loading. Here, we construct a mechanical
environment with programmable strain gradients by using a hydrogel
of a linear elastic property. When seeding cells on such hydrogels,
we demonstrate that the pattern of cellular alignment can be rather
precisely tailored by substrate strains. The experiment is in consistency
with a theoritical prediction when assuming that focal adhesions (FAs)
would drive a cell to reorient to the directions where they are most
stable. A fundamental theory has also been developed and is excellent
in agreement with the complete temporal alignment of cells. This work
not only provides important insights into the cellular response to
the local mechanical microenvironment but can also be utilized to
engineer patterned cellular alignment that can be critical in tissue
remodeling and regenerative medicine applications
Fabrication of Microscale Hydrogels with Tailored Microstructures based on Liquid Bridge Phenomenon
Microscale hydrogels (microgels)
find widespread applications in various fields, such as drug delivery,
tissue engineering, and biosensing. The shape of the microgels is
a critical parameter that can significantly influence their function
in these applications. Although various methods have been developed
(e.g., micromolding, photolithography, microfluidics, and mechanical
deformation method), it is still technically challenging to fabricate
microgels with tailored microstructures. In this study, we have developed
a simple and versatile method for preparing microgels by stretching
hydrogel precursor droplets between two substrates to form a liquid
bridge. Microgels with tailored microstructures (e.g., barrel-like,
dumbbell-like, or funnel-like shapes) have been achieved through adjusting
the distance between and the hydrophobicity of the two substrates.
The developed method holds great potential to impact multiple fields,
such as drug delivery, tissue engineering, and biosensing
Melting Away Pain: Decay of Thermal Nociceptor Transduction during Heat-Induced Irreversible Desensitization of Ion Channels
Thermal
transient receptor potential channels play a key role in
thermal sensation. Although predictive models exist for temperature-dependent
transduction through these channels and for the associated sensations
of pain, the ability to predict irreversible desensitization has been
lacking. We explored the role of irreversible ion channel desensitization
in pain sensation and hypothesized that desensitization of ion channels
would follow the kinetics similar to the denaturation of catalytic
enzymes. We therefore proposed a three-state model to simulate the
kinetic of temperature-sensitive ion channels from the closed state
through opening and irreversible thermal desensitization. We tested
the model against data obtained in vivo from a feline model. The theoretical
model predicts all experimental data with reasonable accuracy, and
represents an important step toward the ability for understanding
of the molecular basis of nociceptor signaling providing the possibility
to design local anesthesia regimens and to the prediction of postoperative
pain
Facial Layer-by-Layer Engineering of Upconversion Nanoparticles for Gene Delivery: Near-Infrared-Initiated Fluorescence Resonance Energy Transfer Tracking and Overcoming Drug Resistance in Ovarian Cancer
Development
of multidrug resistance (MDR) contributes to the majority of treatment
failures in clinical chemotherapy. We report facial layer-by-layer
engineered upconversion nanoparticles (UCNPs) for near-infrared (NIR)-initiated
tracking and delivery of small interfering RNA (siRNA) to enhance
chemotherapy efficacy by silencing the MDR1 gene and resensitizing
resistant ovarian cancer cells to drug. Layer-by-layer engineered
UCNPs were loaded with MDR1 gene-silencing siRNA (MDR1-siRNA) by electrostatic
interaction. The delivery vehicle enhances MDR1-siRNA cellular uptake,
protects MDR1-siRNA from nuclease degradation, and promotes endosomal
escape for silencing the MDR gene. The intrinsic photon upconversion
of UCNPs provides an unprecedented opportunity for monitoring intracellular
attachment and release of MDR1-siRNA by NIR-initiated fluorescence
resonance energy transfer occurs between donor UCNPs and acceptor
fluorescence dye-labeled MDR1-siRNA. Enhanced chemotherapeutic efficacy
in vitro was demonstrated by cell viability assay. The developed delivery
vehicle holds great potential in delivery and imaging-guided tracking
of therapeutic gene targets for effective treatment of drug-resistant
cancers