Effect of single nanoparticle-nanopore interaction strength on ionic current modulation.

Solid-state nanopores are rapidly emerging as promising platforms for developing various single molecule sensing applications. The modulation of ionic current through the pore due to translocation of the target molecule has been the dominant measurement modality in nanopore sensors. Here, we focus on the dwell time, which is the duration taken by the target molecule or particle to traverse the pore and study its dependence on the strength of interaction of the target with the pore using single gold nanoparticles (NPs) as targets interacting with a silicon nitride (SiN) nanopore. The strength of interaction, which in our case is electrostatic in nature, can be controlled by coating the nanoparticles with charged polymers. We report on an operating regime of this nanopore sensor, characterized by attractive interactions between the nanoparticle and the pore, where the dwell time is exponentially sensitive to the target-pore interaction. We used negatively and positively charged gold nanoparticles to control the strength of their interaction with the Silicon Nitride pore which is negatively charged. Our experiments revealed how this modulation of the electrostatic force greatly affects the dwell time. Positively charged NPs with strong attractive interactions with the pore resulted in increase of dwell times by 2-3 orders of magnitude, from 0.4 ms to 75.3 ms. This extreme sensitivity of the dwell time on the strength of interaction between a target and nanopore can be exploited in emerging nanopore sensor applications.

Dealing with infodemic during COVID-19 pandemic: Role of effective health communication in facilitating outbreak response & actions - An ICMR experience.

Objectives: To highlight and assess the impact of intervention tools used by Indian Council of Medical Research (ICMR) against COVID19 associated infodemic in the world's largest democratic country, India. Study design: It is a retrospective cross sectional study. The impact of ICMR's multi-pronged strategy to address the infodemic during pandemic has been assessed through analysis of print media reportage and social media engagements. Methods: The impact of the interventions was assessed using cloud media mappers like MediaCloud and Meltwater using keywords. The data was analysed in terms of reportage, theme of reportage. A sub-section of media reportage (Feb 2020-June 2020) was analysed in details from 4 major dailies to understand the coverage and tonality of media reports. The data on COVID 19 related tweets, posts and uploads were taken from social media platforms of Indian Council of Medical Research (ICMR) particularly twitter, instagram, facebook and youtube and estimate of pre and post pandemic changes in followers or users were collected for analysis. The data was curated and analysed using MS excel. Results: There was a surge of 3800% reportage in media during pandemic as compared to same time frame in pre-pandemic times. A surge of followers on twitter from 26,823 on Feb 2020 (before pandemic) to 3,36,098 at March 2022 (after pandemic) was observed. A drastic increase in monthly followers was observed after start of Pandemic (after Feb 2020) in comparison to before pandemic (Before Feb 2020). Similar trends were observed on other social media platforms of ICMR. Conclusions: The Communications Unit at ICMR geared up with more robust plans and designed several interventions to mitigate the infodemic which helped in evidence based decision making towards outbreak response and action. This highlights the importance of evidence based, crisp, timely and effective communication during the epidemics/pandemics to buid trust and confidence in the community.

DNA Translocation through Vertically Stacked 2D Layers of Graphene and Hexagonal Boron Nitride Heterostructure Nanopore.

Cost-effective, fast, and reliable DNA sequencing can be enabled by advances in nanopore-based methods, such as the use of atomically thin graphene membranes. However, strong interaction of DNA bases with graphene leads to undesirable effects such as sticking of DNA strands to the membrane surface. While surface functionalization is one way to counter this problem, here, we present another solution based on a heterostructure nanopore system, consisting of a monolayer of graphene and hexagonal boron nitride (hBN) each. Molecular dynamics studies of DNA translocation through this heterostructure nanopore revealed a surprising and crucial influence of the heterostructure layer order in controlling the base specific signal variability. Specifically, the heterostructure with graphene on top of hBN had nearly 3-10× lower signal variability than the one with hBN on top of graphene. Simulations point to the role of differential underside sticking of DNA bases as a possible reason for the observed influence of the layer order. Our studies can guide the development of experimental systems to study and exploit DNA translocation through two-dimensional heterostructure nanopores for single molecule sequencing and sensing applications.

DNA Translocation through Hybrid Bilayer Nanopores.

Pore functionalization has been explored by several groups as a strategy to control DNA translocation through solid-state nanopores. Here we present a hybrid nanopore system consisting of single-layer graphene and a DNA origami layer to achieve base-selective control of DNA translocation rate through aligned nanopores of the two layers. This is achieved by incorporating unpaired dangling bases called overhangs to the origami near the pore region. Molecular dynamics simulations were used to optimize the design of the origami nanopore and the overhangs. Specifically, we considered the influence of the number and spatial distribution of overhangs on translocation times. The simulations revealed that specific interactions between the overhangs and the translocating single-stranded DNA resulted in base-specific residence times.