Biology subjects

Muthuswamy, J.

Publications and source records attributed to Muthuswamy, J..

3 recordsLinked to original sources

bioRxiv2024

Rapid SARS-CoV-2 Detection Using High-Sensitivity Thickness Shear Mode Sensors

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has emphasized the urgent need for accurate and readily available diagnostic tools. Conventional diagnostic methods, such as reverse transcription real-time polymerase chain reaction (RT-qPCR), are often labor-intensive and time-consuming, which highlights the necessity for rapid point-of-care diagnostic solutions. This study introduces an innovative, low-cost, and highly sensitive diagnostic platform for swift COVID-19 detection. Our platform utilizes the mass sensing properties of thickness shear mode (TSM) transducers to detect and quantify the SARS-CoV-2 nucleocapsid protein through polyethylene glycol (PEG)-based chemistry (1). To confirm surface functionalization and evaluate the effects of the virus lysis buffer, we employed surface characterization techniques including Digital Holographic Microscopy (DHM), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Sensitivity tests with heat-inactivated SARS-CoV-2 samples demonstrated a sensitivity of about 0.256 Hz/TCID50/mL and a limit of detection (LOD) of roughly 150 TCID50/mL. Specificity was verified through cross-reactivity testing. Our detailed characterization and sensitivity analysis underscore the platforms reliability, making it a promising candidate for efficient and accessible COVID-19 diagnosis at the point of care.

bioengineering↗

bioRxiv2019

Engineering microscale systems for fully autonomous intracellular neural interfaces

Conventional electrodes and associated positioning systems for intracellular recording from single neurons in vitro and in vivo are large and bulky, which has largely limited their scalability. Further, acquiring successful intracellular recordings is very tedious, requiring a high degree of skill not readily achieved in a typical laboratory. We report here a robotic, MEMS-based intracellular recording system to overcome the above limitations associated with form-factor, scalability and highly skilled and tedious manual operations required for intracellular recordings. This system combines three distinct technologies: 1) novel microscale, glass-polysilicon penetrating electrode for intracellular recording, 2) electrothermal microactuators for precise microscale movement of each electrode and 3) closed-loop control algorithm for autonomous positioning of electrode inside single neurons. Here, we demonstrate the novel, fully integrated system of glass-polysilicon microelectrode, microscale actuators and controller for autonomous intracellular recordings from single neurons in the abdominal ganglion of Aplysia Californica (n = 5 cells). Consistent resting potentials (< -35 mV) and action potentials (> 60 mV) were recorded after each successful penetration attempt with the controller and microactuated glass-polysilicon microelectrodes. The success rate of penetration and quality of intracellular recordings achieved using electrothermal microactuators were comparable to that of conventional positioning systems. The MEMS-based system offers significant advantages: 1) reduction in overall size for potential use in behaving animals, 2) scalable approach to potentially realize multi-channel recordings and 3) a viable method to fully automate measurement of intracellular recordings. This system will be evaluated in vivo in future rodent studies.

bioengineering↗

bioRxiv2019

Optogenetic Modulation of Cortical Neurons Using Organic Light Emitting Diodes (OLEDs)

ObjectiveThere is a need for low power, scalable photoelectronic devices and systems for emerging optogenetic needs in neuromodulation. Conventional light emitting diodes (LEDs) are constrained by power and lead-counts necessary for scalability. Organic LEDs (OLEDs) offer an exciting approach to decrease power and lead-counts while achieving high channel counts on thin, flexible substrates that conform to brain surfaces or peripheral neuronal fibers. In this study, we investigate the potential for using OLEDs to modulate neuronal networks cultured in vitro on a transparent microelectrode array (MEA) and subsequently validate neurostimulation in vivo in a transgenic mouse model.\n\nApproachCultured mouse cortical neurons were transfected with light-sensitive opsins such as blue-light sensitive channel-rhodopsin (ChR2) and green-light sensitive chimeric channel-rhodopsin (C1V1tt) and stimulated using blue and green OLEDs (with 455 and 520 nm peak emission spectra respectively) at a power of 1 mW/mm2 under pulsed conditions.\n\nMain resultsWe demonstrate neuromodulation and optostimulus-locked, single unit-neuronal activity in neurons expressing stimulating and inhibiting opsins (n=4 MEAs, each with 16 recordable channels). We also validated the optostimulus-locked response in a channel-rhodopsin expressing transgenic mouse model, where at least three isolatable single neuronal cortical units respond to OLED stimulation.\n\nSignificanceThe above results indicate the feasibility of generating sufficient luminance from OLEDs to perform neuromodulation both in vitro and in vivo. This opens up the possibility of developing thin, flexible OLED films with multiple stimulation sites that can conform to the shape of the neuronal targets in the brain or the peripheral nervous system. However, stability of these OLEDs under chronic conditions still needs to be carefully assessed with appropriate packaging approaches.

bioengineering↗