Boards, Advisory Committees, Professional Organizations
President, Global Health Club (2022 - Present)
Global Health Postdoctoral Affiliate, Center for Innovation in Global Health (CIGH) (2022 - Present)
Manu Prakash, Postdoctoral Faculty Sponsor
Modified full-face snorkel masks as reusable personal protective equipment for hospital personnel.
2021; 16 (1): e0244422
Here we adapt and evaluate a full-face snorkel mask for use as personal protective equipment (PPE) for health care workers, who lack appropriate alternatives during the COVID-19 crisis in the spring of 2020. The design (referred to as Pneumask) consists of a custom snorkel-specific adapter that couples the snorkel-port of the mask to a rated filter (either a medical-grade ventilator inline filter or an industrial filter). This design has been tested for the sealing capability of the mask, filter performance, CO2 buildup and clinical usability. These tests found the Pneumask capable of forming a seal that exceeds the standards required for half-face respirators or N95 respirators. Filter testing indicates a range of options with varying performance depending on the quality of filter selected, but with typical filter performance exceeding or comparable to the N95 standard. CO2 buildup was found to be roughly equivalent to levels found in half-face elastomeric respirators in literature. Clinical usability tests indicate sufficient visibility and, while speaking is somewhat muffled, this can be addressed via amplification (Bluetooth voice relay to cell phone speakers through an app) in noisy environments. We present guidance on the assembly, usage (donning and doffing) and decontamination protocols. The benefit of the Pneumask as PPE is that it is reusable for longer periods than typical disposable N95 respirators, as the snorkel mask can withstand rigorous decontamination protocols (that are standard to regular elastomeric respirators). With the dire worldwide shortage of PPE for medical personnel, our conclusions on the performance and efficacy of Pneumask as an N95-alternative technology are cautiously optimistic.
View details for DOI 10.1371/journal.pone.0244422
View details for PubMedID 33439902
Volcano-Shaped Scanning Probe Microscopy Probe for Combined Force-Electrogram Recordings from Excitable Cells
2020; 20 (6): 4520-4529
Atomic force microscopy based approaches have led to remarkable advances in the field of mechanobiology. However, linking the mechanical cues to biological responses requires complementary techniques capable of recording these physiological characteristics. In this study, we present an instrument for combined optical, force, and electrical measurements based on a novel type of scanning probe microscopy cantilever composed of a protruding volcano-shaped nanopatterned microelectrode (nanovolcano probe) at the tip of a suspended microcantilever. This probe enables simultaneous force and electrical recordings from single cells. Successful impedance measurements on mechanically stimulated neonatal rat cardiomyocytes in situ were achieved using these nanovolcano probes. Furthermore, proof of concept experiments demonstrated that extracellular field potentials (electrogram) together with contraction displacement curves could simultaneously be recorded. These features render the nanovolcano probe especially suited for mechanobiological studies aiming at linking mechanical stimuli to electrophysiological responses of single cells.
View details for DOI 10.1021/acs.nanolett.0c01319
View details for Web of Science ID 000541691200059
View details for PubMedID 32426984
View details for PubMedCentralID PMC7291358
A biphasic growth model for cell pole elongation in mycobacteria
2020; 11 (1): 452
Mycobacteria grow by inserting new cell wall material in discrete zones at the cell poles. This pattern implies that polar growth zones must be assembled de novo at each division, but the mechanisms that control the initiation of new pole growth are unknown. Here, we combine time-lapse optical and atomic force microscopy to measure single-cell pole growth in mycobacteria with nanometer-scale precision. We show that single-cell growth is biphasic due to a lag phase of variable duration before the new pole transitions from slow to fast growth. This transition and cell division are independent events. The difference between the lag and interdivision times determines the degree of single-cell growth asymmetry, which is high in fast-growing species and low in slow-growing species. We propose a biphasic growth model that is distinct from previous unipolar and bipolar models and resembles "new end take off" (NETO) dynamics of polar growth in fission yeast.
View details for DOI 10.1038/s41467-019-14088-z
View details for Web of Science ID 000558877800005
View details for PubMedID 31974342
View details for PubMedCentralID PMC6978421
Overlapping and essential roles for molecular and mechanical mechanisms in mycobacterial cell division
2020; 16 (1): 57-+
Mechanisms to control cell division are essential for cell proliferation and survival 1. Bacterial cell growth and division require the coordinated activity of peptidoglycan synthases and hydrolytic enzymes 2-4 to maintain mechanical integrity of the cell wall 5. Recent studies suggest that cell separation is governed by mechanical forces 6,7. How mechanical forces interact with molecular mechanisms to control bacterial cell division in space and time is poorly understood. Here, we use a combination of atomic force microscope (AFM) imaging, nanomechanical mapping, and nanomanipulation to show that enzymatic activity and mechanical forces serve overlapping and essential roles in mycobacterial cell division. We find that mechanical stress gradually accumulates in the cell wall concentrated at the future division site, culminating in rapid (millisecond) cleavage of nascent sibling cells. Inhibiting cell wall hydrolysis delays cleavage; conversely, locally increasing cell wall stress causes instantaneous and premature cleavage. Cells deficient in peptidoglycan hydrolytic activity fail to locally decrease their cell wall strength and undergo natural cleavage, instead forming chains of non-growing cells. Cleavage of these cells can be mechanically induced by local application of stress with AFM. These findings establish a direct link between actively controlled molecular mechanisms and passively controlled mechanical forces in bacterial cell division.
View details for DOI 10.1038/s41567-019-0679-1
View details for Web of Science ID 000508800600018
View details for PubMedID 31921326
View details for PubMedCentralID PMC6952280
- Hybrid hydrodynamic characteristic for hydrocephalus valve: A numerical investigation using electrical equivalent networks COGENT ENGINEERING 2017; 4 (1)
- Microfluidic bacterial traps for simultaneous fluorescence and atomic force microscopy NANO RESEARCH 2017; 10 (11): 3896-3908
Cancer-cell stiffening via cholesterol depletion enhances adoptive T-cell immunotherapy
NATURE BIOMEDICAL ENGINEERING
Malignant transformation and tumour progression are associated with cancer-cell softening. Yet how the biomechanics of cancer cells affects T-cell-mediated cytotoxicity and thus the outcomes of adoptive T-cell immunotherapies is unknown. Here we show that T-cell-mediated cancer-cell killing is hampered for cortically soft cancer cells, which have plasma membranes enriched in cholesterol, and that cancer-cell stiffening via cholesterol depletion augments T-cell cytotoxicity and enhances the efficacy of adoptive T-cell therapy against solid tumours in mice. We also show that the enhanced cytotoxicity against stiffened cancer cells is mediated by augmented T-cell forces arising from an increased accumulation of filamentous actin at the immunological synapse, and that cancer-cell stiffening has negligible influence on: T-cell-receptor signalling, production of cytolytic proteins such as granzyme B, secretion of interferon gamma and tumour necrosis factor alpha, and Fas-receptor-Fas-ligand interactions. Our findings reveal a mechanical immune checkpoint that could be targeted therapeutically to improve the effectiveness of cancer immunotherapies.
View details for DOI 10.1038/s41551-021-00826-6
View details for Web of Science ID 000727131700001
View details for PubMedID 34873307
View details for PubMedCentralID PMC7612108
- Passive flow control valve for protein delivery COGENT ENGINEERING 2017; 4 (1)
Division site selection linked to inherited cell surface wave troughs in mycobacteria
2017; 2 (9): 17094
Cell division is tightly controlled in space and time to maintain cell size and ploidy within narrow bounds. In bacteria, the canonical Minicell (Min) and nucleoid occlusion (Noc) systems together ensure that division is restricted to midcell after completion of chromosome segregation1. It is unknown how division site selection is controlled in bacteria that lack homologues of the Min and Noc proteins, including mycobacteria responsible for tuberculosis and other chronic infections2. Here, we use correlated optical and atomic-force microscopy3,4 to demonstrate that morphological landmarks (waveform troughs) on the undulating surface of mycobacterial cells correspond to future sites of cell division. Newborn cells inherit wave troughs from the (grand)mother cell and ultimately divide at the centre-most wave trough, making these morphological features the earliest known landmark of future division sites. In cells lacking the chromosome partitioning (Par) system, missegregation of chromosomes is accompanied by asymmetric cell division at off-centre wave troughs, resulting in the formation of anucleate cells. These results demonstrate that inherited morphological landmarks and chromosome positioning together restrict mycobacterial division to the midcell position.
View details for DOI 10.1038/nmicrobiol.2017.94
View details for Web of Science ID 000410622800016
View details for PubMedID 28650475
Components for high-speed atomic force microscopy optimized for low phase-lag
IEEE. 2017: 731-736
View details for Web of Science ID 000426448500120
- Design of a passive flow regulator using a genetic algorithm ELSEVIER SCIENCE BV. 2016: 1016-1019