Dilip Kumar Agarwal

Water contamination by harmful chemicals is a growing global concern, creating a need to develop technologies that can detect a range of target compounds at the required concentrations. Here, we address this need by merging biological allosteric transcription factors with DNA-coated nanomechanical microcantilevers to detect chemicals in water with a digital readout. After proof-of-concept demonstration and optimization to detect anhydrotetracycline with the TetR transcription factor, we use the CadC transcription factor to detect Pb²⁺ and Cd²⁺ in water at concentrations down to 2 and 1 ppb, respectively, in less than 15 min. A computational model suggests this improvement in sensitivity could be achieved by the DNA-coated microcantilever surface changing the transcription factor binding properties. Our findings demonstrate a promising approach for water quality monitoring with fast, highly sensitive, digital readout.

Water contamination is a growing global concern, creating a need to develop technologies that can detect a range of target compounds at the required thresholds. Here, we address this need by merging biological allosteric transcription factors with DNA coated nanomechanical microcantilevers to detect chemicals in water with digital readout. After proof-of-concept demonstration and optimization to detect tetracycline with the TetR transcription factor, we use the CadC transcription factor to detect Pb ²⁺ and Cd ²⁺ in water at concentrations down to 2 ppb and 1 ppb, respectively, in less than fifteen minutes. A computational model suggests this improvement in sensitivity could be achieved by the DNA coated microcantilever surface changing transcription factor binding properties. Our findings demonstrate a promising new approach for water quality monitoring with fast, highly sensitive, digital readouts.

Binding configuration of ade novostapled peptide on SARS-CoV-2 spike protein, as predicted by molecular simulation. Stapled residues enhance peptide stability while interacting residues engage key amino acids on the protein receptor-binding domain.

This research paper aims to provide a comprehensive understanding of the process validation of Paracetamol tablets according to the guidelines outlined by the International Council for Harmonisation of Technical Requirements forPharmaceuticals for Human Use (ICH). Paracetamol is a widely used analgesic and antipyretic drug, and ensuring the quality, safety, and efficacy of its dosage form is of utmost importance. This study encompasses the three stages of process validation, namely process design, process qualification, and continued process verification, with a focus oncritical parameters and attributes. The article also explores the role of regulatory guidelines, such as the ICH Q8 (R2), Q9,and Q10, in facilitating effective process validation. (1) Key words: Process Validation, ICH, CPP, CQA, SPC, Change Control, VMP;

New platforms for the rapid and sensitive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern are urgently needed. Here we report the development of a nanomechanical sensor based on the deflection of a microcantilever capable of detecting the SARS-CoV-2 spike (S) glycoprotein antigen using computationally designed multivalent minibinders immobilized on a microcantilever surface. The sensor exhibits rapid (<5 min) detection of the target antigens down to concentrations of 0.05 ng/mL (362 fM) and is more than an order of magnitude more sensitive than an antibody-based cantilever sensor. Validation of the sensor with clinical samples from 33 patients, including 9 patients infected with the Omicron (BA.1) variant observed detection of antigen from nasopharyngeal swabs with cycle threshold (Ct) values as high as 39, suggesting a limit of detection similar to that of the quantitative reverse transcription polymerase chain reaction (RT-qPCR). Our findings demonstrate the use of minibinders and nanomechanical sensors for the rapid and sensitive detection of SARS-CoV-2 and potentially other disease markers.

Dynamic sensing using microcantilevers has held the centre stage for a long time in biomolecular detection. In this work, we have reported a comparative study of dynamic responses of asymmetric (top or bottom surface) and symmetric (both top and bottom surfaces) modifications (biofunctionalization) of silicon nitride/oxide microcantilevers. For the first time, surface stress (in terms of surface energy/area) has been shown to govern the change in resonant frequency by studying the dynamic responses of asymmetrically and symmetrically modified microcantilevers using a conventional laser doppler vibrometer. The resonant frequency of asymmetrically modified microcantilever was found to be lower than that of symmetrically modified one by a magnitude of ~0.4 kHz. Also, it was observed that the amplitude of oscillation increased from symmetrically modified to asymmetrically modified microcantilever. Consequentially, we have reported (by means of mathematical calculations and nanoindentation experiments) the increase in flexural rigidity as well as surface stress from symmetric modification to the asymmetric one. Owing to the decrease in the resonant frequencies as well as downward bending of microcantilevers, we conclude that compressive surface stress is developed after surface modifications. This work will be of immense interest to the researchers working in the field of dynamic sensing using MEMS-based sensors.

Microcantilever-based sensor platform has attracted a lot of attention over the time in detection of a variety of molecules due to their miniaturized dimensions. Sensitivity enhancement is an important aspect of such sensors, especially when used for point-of-care diagnostic purpose. However, the major concern while operating these sensors in deflection mode is their sensitivity which mainly relies on selective chemical modification protocols employed on these sensor surfaces. One of the ways of getting better sensitivity is through asymmetric (one side) biofunctionalization of the sensor surface. In the presented work here, we have demonstrated a novel approach of asymmetric biofunctionalization of proteins in overall sensitivity enhancement of piezoresistive silicon nitride-oxide microcantilever sensor platform inside a flow chamber. Herein, using our developed surface chemistry, asymmetrically biofunctionalized microcantilevers first exhibited a greater electrical response in terms of piezoresistance change than their symmetric counterpart in the detection of human immunoglobulins (HIgGs) protein. Finally, these microcantilevers were employed to exhibit the enhanced sensitivity towards the detection of a crucial cardiac marker protein, i.e. Troponin-I (cTnI) down to 250 ng ml ⁻¹ using asymmetric biofunctionalization process. This study shows that the developed asymmetric biofunctionalization methodology may be used as a general protocol to detect other important biomarkers of clinical applications with improved sensitivity.

Acute myocardial infarction (AMI) is a serious health problem that must be identified in its early stages. Considerable progress has been made in understanding the condition of AMI through ascertaining the role of biomarkers, such as myoglobin, cardiac troponin proteins (T and I), creatine kinase-MB, and fatty acid-binding protein (FABP). A field-effect transistor (FET) is an effective platform; however, innovations are required in all layers of the FET for it to become robust and highly sensitive. For the first time, we made use of the synergistic combination of noble metal nanoparticles (AuNPs) with Co₃O₄ for the detection of cardiac troponin T (cTnT) in a FET platform. We determined the morphology of Au-decorated Co₃O₄ NRs and their electronic properties by characterizing the channel layer using electron microscopies and transient measurements. Subsequently, we performed the detection of cardiac troponin T by immobilizing its complementary biotinylated DNA aptamer on the channel surface using a drop-casting method. To understand the changes in drain current caused by this interaction, we probed our SWCNT–Co₃O₄ NR transistor with limited gate and drain bias (≤1 V), achieving a sensitivity of 0.5 μA μg⁻¹ mL⁻¹ for the Au-decorated NRs. A 250% increase in the sensitivity and a limit of detection (LOD) of 0.1 μg mL⁻¹ were achieved by using this device. Finally, selectivity studies proved that this synergistic combination works well in the FET configuration for the successful detection of cTnT.