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  1. Abstract

    The fabrication of perfusable hydrogels is crucial for recreating in vitro microphysiological environments. Existing strategies to fabricate complex microchannels in hydrogels involve sophisticated equipment/techniques. A cost‐effective, facile, versatile, and ultra‐fast methodology is reported to fabricate perfusable microchannels of complex shapes in photopolymerizable hydrogels without the need of specialized equipment or sophisticated protocols. The methodology utilizes one‐step ultraviolet (UV) light‐triggered cross‐linking and a photomask printed on inexpensive transparent films to photopattern PEG‐norbornene hydrogels. Complex and intricate patterns with high resolution, including perfusable microchannels, can be fabricated in <1 s. The perfusable hydrogel is integrated into a custom‐made microfluidic device that permits connection to external pump systems, allowing continuous fluid perfusion into the microchannels. Under dynamic culture, human endothelial cells form a functional and confluent endothelial monolayer that remains viable for at least 7 days and respond to inflammatory stimuli. Finally, approach to photopattern norbornene hyaluronic acid hydrogels is adapted, highlighting the versatility of the technique. This study presents an innovative strategy to simplify and reduce the cost of biofabrication techniques for developing functional in vitro models using perfusable three‐dimensional (3D) hydrogels. The approach offers a novel solution to overcome the complexities associated with existing methods, allowing engineering advanced in vitro microphysiological environments.

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  2. Abstract

    Emergent trends in the device development for neural prosthetics have focused on establishing stimulus localization, improving longevity through immune compatibility, reducing energy re-quirements, and embedding active control in the devices. Ultrasound stimulation can single-handedly address several of these challenges. Ultrasonic stimulus of neurons has been studied extensively from 100 kHz to 10 MHz, with high penetration but less localization. In this paper, a chip-scale device consisting of piezoelectric Aluminum Nitride ultrasonic transducers was engineered to deliver gigahertz (GHz) ultrasonic stimulus to the human neural cells. These devices provide a path towards complementary metal oxide semiconductor (CMOS) integration towards fully controllable neural devices. At GHz frequencies, ultrasonic wavelengths in water are a few microns and have an absorption depth of 10–20 µm. This confinement of energy can be used to control stimulation volume within a single neuron. This paper is the first proof-of-concept study to demonstrate that GHz ultrasound can stimulate neuronsin vitro. By utilizing optical calcium imaging, which records calcium ion flux indicating occurrence of an action potential, this paper demonstrates that an application of a nontoxic dosage of GHz ultrasonic waves$$(\ge 0.05\frac{W}{c{m}^{2}})$$(0.05Wcm2)caused an average normalized fluorescence intensity recordings >1.40 for the calcium transients. Electrical effects due to chip-scale ultrasound delivery was discounted as the sole mechanism in stimulation, with effects tested atα = 0.01 statistical significance amongst all intensities and con-trol groups. Ionic transients recorded optically were confirmed to be mediated by ion channels and experimental data suggests an insignificant thermal contributions to stimulation, with a predicted increase of 0.03oCfor$$1.2\frac{W}{c{m}^{2}}\cdot $$1.2Wcm2This paper paves the experimental framework to further explore chip-scale axon and neuron specific neural stimulation, with future applications in neural prosthetics, chip scale neural engineering, and extensions to different tissue and cell types.

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  3. Abstract Osteoarthritis (OA) of the knee joint is a degenerative disease initiated by mechanical stress that affects millions of individuals. The disease manifests as joint damage and synovial inflammation. Post-traumatic osteoarthritis (PTOA) is a specific form of OA caused by mechanical trauma to the joint. The progression of PTOA is prevented by immediate post-injury therapeutic intervention. Intra-articular injection of anti-inflammatory therapeutics (e.g. corticosteroids) is a common treatment option for OA before end-stage surgical intervention. However, the efficacy of intra-articular injection is limited due to poor drug retention time in the joint space and the variable efficacy of corticosteroids. Here, we endeavored to characterize a four-arm maleimide-functionalized polyethylene glycol (PEG-4MAL) hydrogel system as a ‘mechanical pillow’ to cushion the load-bearing joint, withstand repetitive loading and improve the efficacy of intra-articular injections of nanoparticles containing dexamethasone, an anti-inflammatory agent. PEG-4MAL hydrogels maintained their mechanical properties after physiologically relevant cyclic compression and released therapeutic payload in an on-demand manner under in vitro inflammatory conditions. Importantly, the on-demand hydrogels did not release nanoparticles under repetitive mechanical loading as experienced by daily walking. Although dexamethasone had minimal protective effects on OA-like pathology in our studies, the PEG-4MAL hydrogel functioned as a mechanical pillow to protect the knee joint from cartilage degradation and inhibit osteophyte formation in an in vivo load-induced OA mouse model. 
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  4. Abstract

    Antibiotic‐resistant bacteria are a major global health threat that continues to rise due to a lack of effective vaccines. Of concern areKlebsiella pneumoniae(K. pneumoniae) that fail to induce in vivo germinal center B cell responses, which facilitate antibody production to fight infection. Immunotherapies using antibodies targeting antibiotic‐resistant bacteria are emerging as promising alternatives, however, they cannot be efficiently derived ex vivo, necessitating the need for immune technologies to develop therapeutics. Here, polyethylene glycol (PEG)‐based immune organoids are developed to elucidate the effects of polymer end‐point chemistry, integrin ligands, and mode ofK. pneumoniaeantigen presentation on germinal center‐like B cell phenotype and epigenetics, to better define the lymph node microenvironment factors regulating ex vivo germinal center dynamics. Notably, PEG vinyl sulfone or acrylate fail to sustain primary immune cells, but functionalization with maleimide (PEG‐4MAL) leads to B cell expansion and germinal center‐like induction. RNA sequencing analysis of lymph node stromal and germinal center B cells shows niche associated heterogeneity of integrin‐related genes. Incorporation of niche‐mimicking peptides reveals that collagen‐1 promotes germinal center‐like dynamics and epigenetics. PEG‐4MAL organoids elucidate the impact ofK. pneumoniaeouter membrane‐embedded protein antigen versus soluble antigen presentation on germinal centers and preserve the response across young and aged mice.

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  5. Abstract

    Following treatment with androgen receptor (AR) pathway inhibitors, ≈20% of prostate cancer patients progress by shedding their AR‐dependence. These tumors undergo epigenetic reprogramming turning castration‐resistant prostate cancer adenocarcinoma (CRPC‐Adeno) into neuroendocrine prostate cancer (CRPC‐NEPC). No targeted therapies are available for CRPC‐NEPCs, and there are minimal organoid models to discover new therapeutic targets against these aggressive tumors. Here, using a combination of patient tumor proteomics, RNA sequencing, spatial‐omics, and a synthetic hydrogel‐based organoid, putative extracellular matrix (ECM) cues that regulate the phenotypic, transcriptomic, and epigenetic underpinnings of CRPC‐NEPCs are defined. Short‐term culture in tumor‐expressed ECM differentially regulated DNA methylation and mobilized genes in CRPC‐NEPCs. The ECM type distinctly regulates the response to small‐molecule inhibitors of epigenetic targets and Dopamine Receptor D2 (DRD2), the latter being an understudied target in neuroendocrine tumors. In vivo patient‐derived xenograft in immunocompromised mice showed strong anti‐tumor response when treated with a DRD2 inhibitor. Finally, we demonstrate that therapeutic response in CRPC‐NEPCs under drug‐resistant ECM conditions can be overcome by first cellular reprogramming with epigenetic inhibitors, followed by DRD2 treatment. The synthetic organoids suggest the regulatory role of ECM in therapeutic response to targeted therapies in CRPC‐NEPCs and enable the discovery of therapies to overcome resistance.

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  6. Abstract

    Nanoparticle shape has emerged as a key regulator of nanoparticle transport across physiological barriers, intracellular uptake, and biodistribution. We report a facile approach to synthesize ellipsoidal nanoparticles through self‐assembly of poly(glycerol sebacate)‐co‐poly(ethylene glycol) (PGS‐co‐PEG). The PGS‐PEG nanoparticle system is highly tunable, and the semiaxis length of the nanoparticles can be modulated by changing PGS‐PEG molar ratio and incorporating therapeutics. As both PGS and PEG are highly biocompatible, the PGS‐co‐PEG nanoparticles show high hemo‐, immuno‐, and cytocompatibility. Our data suggest that PGS‐co‐PEG nanoparticles have the potential for use in a wide range of biomedical applications including regenerative medicine, stem cell engineering, immune modulation, and cancer therapeutics. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2048–2058, 2018.

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