Biology subjects

Tiwari, I.

Publications and source records attributed to Tiwari, I..

5 recordsLinked to original sources

bioRxiv2025

Biofabrication of gold nanoparticles (GNPs) synthesized from Dillenia indica leaves with their anticancer, antibacterial, and antioxidant activities.

In this study, we describe the cytotoxic and antibacterial capabilities of gold nanoparticles (GNPs) synthesized from Dillenia indica leaves. Here, we used an environmentally friendly method to synthesize GNPs and then characterized them using techniques such as transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible spectroscopy, XRD, and Fourier transform infrared spectroscopy. The Surface Plasmon Resonance of GNPs was identified by an absorption peak at 533 nm in the UV-visible spectroscopic studies. The biosynthesized GNPs had an average size of 83 nm and were spherical in shape, according to TEM examination. Its interesting to note that the biosynthesized GNPs exhibited antibacterial action against a variety of bacterial isolates, both Gram-positive and negative. By using an MTT assay, growth inhibition and the cytotoxic effect of the synthesized GNPs against Daltons lymphoma cell lines were also evaluated.

plant biology↗

bioRxiv2025

Adhesion and injury cues enhance blackworm captureby freshwater planaria

In aquatic ecosystems, freshwater planarians (Dugesia spp.) function as predators, employing specialized adaptations for capturing live prey. This exploratory study examines the predatory interactions between the freshwater planarian Dugesia spp. and the California blackworm (Lumbriculus variegatus). Observations demonstrate that Dugesia is capable of capturing prey more than twice its own length. The predation process involves a dual adhesion mechanism whereby the planarian adheres simultaneously to the blackworm and the substrate, effectively immobilizing its prey. Despite the rapid escape response of blackworms, characterized by a reversing spiral swimming gait, planarian adhesion frequently prevents successful escape, although notably larger blackworms exhibit increased escape success. Subsequently, Dugesia employs an eversible pharynx to initiate ingestion, consuming the internal tissues of the blackworm through suction. Injury in blackworms emerged as a significant predictor of predation events, suggesting the potential involvement of chemical cues in prey detection, although this warrants further investigation. This study provides insights into the biomechanics and behaviors of predation involving two interacting muscular hydrostats, highlighting the critical adaptations that enable planarians to subdue and consume relatively large, mobile prey.

biophysics↗

bioRxiv2025

Rhagovelia uses interfacial run-and-tumble locomotionto improve prey capture in flowing environments

Rhagovelia oriander is a freshwater water strider native to the rivers and streams of North and South America, known for its distinctive skating movement on the waters surface. This movement resembles the correlated random-walk pattern seen in microorganisms such as Escherichia coli. Previous studies have primarily focused on limb adaptations and biomechanics, leaving the ecological significance inadequately addressed. We combine field observations with controlled laboratory experiments using a flow mill to investigate the dynamics of R. oriander under typical flow conditions. Our findings indicate that this insect exhibits a two-dimensional run-and-tumble motion, often incorporating lateral tumbles following straight runs (run distance: 30.7 {+/-} 9.3 mm). We find that this behavior is resilient to changes in flow speed. In-silico simulations of particle interception demonstrated that this locomotion method enhances encounter rates compared to linear movement, particularly when the simulated food particle is following a rapid flow field. Our results document run-and-tumble locomotion in a millimeter-scale organism, showcasing a unique example of convergent behavior across diverse taxonomic groups and providing valuable insights into locomotion ecology while serving as a source of inspiration for bioinspired robotics and environmental exploration algorithms.

biophysics↗

bioRxiv2024

Reversible kink instability drives ultrafast jumping in nematodes and soft robots

Entomopathogenic nematodes (EPNs) exhibit a bending-elastic instability, or kink, before becoming airborne, a feature hypothesized but not proven to enhance jumping performance. Here, we provide the evidence that this kink is crucial for improving launch performance. We demonstrate that EPNs actively modulate their aspect ratio, forming a liquid-latched closed loop over a slow timescale O(1 s), then rapidly open it O (10 {micro}s), achieving heights of 20 body lengths (BL) and generating [~] 104 W/Kg of power. Using jumping nematodes, a bio-inspired Soft Jumping Model (SoftJM), and computational simulations, we explore the mechanisms and implications of this kink. EPNs control their takeoff direction by adjusting their head position and center of mass, a mechanism verified through phase maps of jump directions in simulations and SoftJM experiments. Our findings reveal that the reversible kink instability at the point of highest curvature on the ventral side enhances energy storage using the nematodes limited muscular force. We investigated the impact of aspect ratio on kink instability and jumping performance using SoftJM, and quantified EPN cuticle stiffness with AFM, comparing it with C. elegans. This led to a stiffness-modified SoftJM design with a carbon fiber backbone, achieving jumps of [~]25 BL. Our study reveals how harnessing kink instabilities, a typical failure mode, enables bidirectional jumps in soft robots on complex substrates like sand, offering a novel approach for designing limbless robots for controlled jumping, locomotion, and even planetary exploration.

biophysics↗

bioRxiv2023

Collecting-Gathering Biophysics of the Blackworm L. variegatus

Many organisms exhibit collecting and gathering behaviors as a foraging and survival method. Certain benthic macroinvertebrates are classified as collector-gatherers due to their collection of particulate matter as a food source, such as the aquatic oligochaete Lumbriculus variegatus (California blackworms). Blackworms demonstrate the ability to ingest organic and inorganic materials, including microplastics, but previous work has only qualitatively described their possible collecting behaviors for such materials. The mechanism through which blackworms consolidate discrete particles into a larger clumps remains unexplored quantitatively. By analyzing a group of blackworms in a large arena with an aqueous algae solution, we discover that their relative collecting efficiency is proportional to population size. Examining individual blackworms under a microscope reveals that both algae and microplastics physically adhere to the worms body due to external mucus secretions, which cause the materials to clump around the worm. We observe that this clumping reduces the worms exploration of its environment, potentially due to thigmotaxis. To validate the observed biophysical mechanisms, we create an active polymer model of a worm moving in a field of particulate debris with a short-range attractive force on its body to simulate its adhesive nature. We find that the attractive force increases gathering efficiency. This study offers insights into the mechanisms of collecting-gathering behavior, informing the design of robotic systems, as well as advancing our understanding the ecological impacts of microplastics on benthic invertebrates.

ecology↗