Biology subjects

Marar, C.

Publications and source records attributed to Marar, C..

3 recordsLinked to original sources

bioRxiv2024

High-precision photoacoustic neural modulation uses a non-thermal mechanism

Neuromodulation is a powerful tool for fundamental studies in neuroscience and potential treatments of neurological disorders. Both photoacoustic (PA) and photothermal (PT) effects have been harnessed for non-genetic high-precision neural stimulation. Using a fiber-based device excitable by a nanosecond pulsed laser and a continuous wave laser for PA and PT stimulation, respectively, we systematically investigated PA and PT neuromodulation at single neuron level. Our results show that the laser energy needed for PA neurostimulaion is 1/40 of that needed for PT stimulation to achieve the same level of cell response recorded by Ca2+ imaging. The threshold energy for PA stimulation is found to be further reduced in neurons overexpressing mechano-sensitive channels, indicating the direct involvement of mechano-sensitive channels in PA stimulation. Electrophysiology study of single neurons upon PA and PT stimulation was performed by patch clamp recordings. Electrophysiological features stimulated by PA are distinct from those induced by PT, confirming that PA and PT stimulations operate through distinct mechanisms. These insights offer a foundation for rational design of more efficient and safer non-genetic neural modulation approaches.

neuroscience↗

bioRxiv2023

Small extracellular vesicles promote stiffness-mediated metastasis

Tissue stiffness is a critical prognostic factor in breast cancer and is associated with metastatic progression. Here we show an alternative and complementary hypothesis of tumor progression whereby physiological matrix stiffness affects the quantity and protein cargo of small EVs produced by cancer cells, which in turn drive their metastasis. Primary patient breast tissue produces significantly more EVs from stiff tumor tissue than soft tumor adjacent tissue. EVs released by cancer cells on matrices that model human breast tumors (25 kPa; stiff EVs) feature increased adhesion molecule presentation (ITG2{beta}1, ITG6{beta}4, ITG6{beta}1, CD44) compared to EVs from softer normal tissue (0.5 kPa; soft EVs), which facilitates their binding to extracellular matrix (ECM) protein collagen IV, and a 3-fold increase in homing ability to distant organs in mice. In a zebrafish xenograft model, stiff EVs aid cancer cell dissemination through enhanced chemotaxis. Moreover, normal, resident lung fibroblasts treated with stiff and soft EVs change their gene expression profiles to adopt a cancer associated fibroblast (CAF) phenotype. These findings show that EV quantity, cargo, and function depend heavily on the mechanical properties of the extracellular microenvironment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/545937v3_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1be1dbdorg.highwire.dtl.DTLVardef@928710org.highwire.dtl.DTLVardef@1e14e9borg.highwire.dtl.DTLVardef@efdb7f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Wireless Neuromodulation at Submillimeter Precision via a Microwave Split-Ring Resonator

Microwaves, with wavelengths on the order of millimeters, have centimeter-scale penetration depth and have been shown to reversibly inhibit neuronal activity. Yet, microwaves alone do not provide sufficient spatial precision to modulate target neurons without affecting surrounding tissues. Here, we report an implantable split-ring resonator (SRR) that generates a localized and enhanced microwave field at the gap site with submillimeter spatial precision. The SRR breaks the microwave diffraction limit and greatly enhances the efficiency of microwave inhibition. With the SRR, microwaves at dosages below the safe exposure limit are shown to inhibit neurons within 1 mm from the gap site. Application of the microwave SRR to suppress seizures in an in vivo model of epilepsy is demonstrated.

bioengineering↗