Biology subjects

Marar, C.

Publications and source records attributed to Marar, C..

7 recordsLinked to original sources

bioRxiv2026

Blood-Mediated Opto-Acoustic Stimulation of Brain Cortex at Sub-millimeter Precision

Direct modulation of neural activity with high spatiotemporal precision is a cornerstone in experimental neuroscience. Here, we present a blood-mediated optoacoustic stimulation (BOAS) approach that utilizes blood as an endogenous transducer for brain stimulation. By delivering 532-nm nanosecond pulsed laser to the cortex, we demonstrate that the absorption of hemoglobin generates sufficient acoustic pressure to trigger neuronal activity. By integrating BOAS with calcium imaging in GCaMP6f-expressing mice, localized neuronal responses were observed. Quantitative analysis reveals that BOAS produces responses comparable to natural visual stimulation and is significantly more efficient than the photothermal stimulation. Furthermore, we show that the response is dose-dependent. At high energy doses, BOAS induces cortical spreading depression. Histological evaluation confirmed that the brain maintains tissue integrity even under these stimulation parameters. Together, this work establishes a versatile method for precise brain stimulation as an alternative method for stimulating neuron at cortex.

bioengineering↗

bioRxiv2025

Highly reproduceable tapered fiber optoacoustic emitters by in-situ photothermal curing of PDMS for single neuron stimulation

Precise neural modulation is an important tool in neuroscience research for intervene of specific neural pathways. Photoacoustic is an emerging technology enabling high precision non-genetic neural stimulation in vitro and in vivo. In this paper, we report a new method to prepare a Candle Soot - Tapered Fiber based Optoacoustic Emitter (CSTFOE) through an in-situ photothermal curing process. The emitter created was found with high spatial resolution and efficiency for neuromodulation. In the meanwhile, the in-situ photothermal curing procedure is highly reproducible and allows for fabricating the photoacoustic coating on the tiny tip of the tapered fiber with a diameter less than 20 m. With the high efficiency and reproducibility, we designed an integrated photoacoustic neuromodulation system incorporating the CSTFOE, a nanosecond pulsed laser for photoacoustic generation, and a function generator for synchronization, achieving effective neuromodulation in vitro.

neuroscience↗

bioRxiv2025

Bi-modal microwave neuromodulation via thermal and nonthermal mechanisms

Electrical neuromodulation, the current clinical standard, is invasive, expensive, and prone to malfunction. Electromagnetic waves can perform noninvasive neuromodulation, but existing methods are limited by the tradeoff between penetration depth and spatial precision. Microwaves in the 0.9 - 3 GHz range are widely used for telecommunications and can penetrate to the deep brain. Microwaves have been shown to nonthermally modulate neural activity, but the acute bioeffects remain unclear and under-studied. Here, we employ a microwave rod antenna (MRA) to demonstrate bi-modal neuromodulation via thermal and non-thermal mechanisms. The MRA enabled electrophysiological recordings of neurons exposed to microwaves, which elucidated the differential effects of pulsed and continuous microwaves on neurons. These findings build the foundation for developing microwave-based wireless neuromodulation devices for drug-free treatment of seizures and chronic pain.

neuroscience↗

bioRxiv2024

Ultrasensitive in vivo infrared spectroscopic imaging via oblique photothermal microscopy

In vivo IR spectroscopy faces challenges due to poor sensitivity in reflection mode and low resolution at micrometer scale. To break this barrier, we report an oblique photothermal microscope (OPTM) to enable ultrasensitive IR spectroscopic imaging of live subjects at sub-micron resolution. Classic photothermal measurement captures only a small fraction of probe photons through a pinhole to extract the photothermal signal. Instead, OPTM uses a differential split detector placed on the sample surface to collect 500-fold more photons and suppress the laser noise by 12 fold via balanced detection. Leveraging its improved sensitivity, OPTM enables low-dose IR imaging of skin without photodamage. Depth-resolved in vivo OPTM imaging of metabolic markers beneath mouse and human skin is shown. Furthermore, we demonstrate in vivo OPTM tracking of topical drug contents within mouse and human skin. Collectively, OPTM presents a highly sensitive imaging platform for in vivo and in situ molecular analysis.

bioengineering↗

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↗