Tuning Hydrophobicity of Paper Substrates for Effective Colorimetric detection of Glucose and Nucleic acids.

This study investigated the colorimetric response of standard glucose, serum glucose, and nucleic acid assays on various paper surfaces with different wettability, including hydrophilic, hydrophobic, and nearly superhydrophobic surfaces. Water contact angles (WCA) formed by water droplets on each surface were measured using ImageJ software. The hydrophilic surface showed no contact angle, while the hydrophobic and nearly superhydrophobic surfaces exhibited contact angles of 115.667° and 133.933°, respectively. The colorimetric sensitivity of the standard glucose assay was analyzed on these surfaces, revealing enhanced sensitivity on the nearly superhydrophobic surface due to the high molecular crowding effect owing to its non-wetting behavior and eventually confined reaction product at the sample loading zone. The hydrophobic nature of the surface restricts the spreading and diffusion of the reaction product, leading to a controlled and localized concentration of the assay product leading to moderate colorimetric intensity. On the other hand, the hydrophilic surface showed the least enhancement in colorimetric sensitivity; this is attributed to the high wettability of the hydrophilic surface causing the reaction product to spread extensively, resulting in a larger area of dispersion and consequently a lower colorimetric intensity. The measured limit of detection (LOD) for nucleic acid on nearly superhydrophobic surfaces was found to be 16.15 ng/µL, which was almost four-fold lower than on hydrophilic surfaces (60.08 ng/µL). Additionally, the LODs of standard glucose and clinical serum samples were two-fold lower on nearly superhydrophobic surfaces compared to hydrophilic surfaces. Our findings clearly highlight the promising potential of utilizing superhydrophobic surfaces to significantly enhance colorimetric sensitivity in paper-based diagnostic applications. This innovative approach holds promise for advancing point-of-care diagnostics and improving disease detection in resource-limited settings.

DNA compaction enhances the sensitivity of fluorescence-based nucleic acid assays: a game changer in point of care sensors?

Fluorescence-based nucleic acid assays frequently exhibit a feeble signal at low analyte concentrations, necessitating complex, expensive methods such as the development of sequence-specific oligo tags, molecular beacons, and chemical modifications to maintain high detection sensitivity. Hence, there is growing interest in accomplishing fluorescence enhancement in nucleic acid assays using robust and cost-effective strategies. The study exploits the use of two compaction agents, PEG 8000 and CTAB, to compact the ITS-2 amplicon of the fungus Candida albicans and evaluates the effect of both of these agents on the fluorescence intensity of SYTO-9 labelled nucleic acids. Conventional fluorometric measurements showed that both CTAB and PEG 8000 enhanced the emission intensity by ∼1.2- and 2-fold, respectively. Furthermore, we leveraged paper-based spot tests and distance-based assays to validate the effect of DNA compaction for enhancing sensitivity in the point-of-care context. The spot assay performed on paper with compacted samples showed an increase in the emission intensity of SYTO-9 and this was manifested by an elevated G channel intensity in the order of PEG 8000 compacted > CTAB compacted > amplified. Moreover, in the distance-based assay, the PEG 8000 compacted sample was found to migrate farther compared to CTAB compacted and amplified DNA samples at amplicon concentrations, 15 µg ml-1 and 39.65 µg ml-1. The limit of detection (LOD) for PEG 8000 and CTAB compacted samples on both paper-spot and distance-based assays were found to be 0.4 µg ml-1 and 0.5 µg ml-1, respectively. Hence our work provides an overview of employing DNA compaction as an approach for enhancing the sensitivity of fluorescence-based point-of-care nucleic acid assays without the need for cumbersome sensitivity enhancement methods.

A Hypothetical Approach to Concentrate Microorganisms from Human Urine Samples Using Paper-Based Adsorbents for Point-of-Care Molecular Assays.

This hypothesis demonstrates that the efficiency of loop-mediated isothermal amplification (LAMP) for nucleic acid detection can be positively influenced by the preconcentration of microbial cells onto hydrophobic paper surfaces. The mechanism of this model is based on the high affinity of microbes towards hydrophobic surfaces. Extensive studies have demonstrated that hydrophobic surfaces exhibit enhanced bacterial and fungal adhesion. By exploiting this inherent affinity of hydrophobic paper substrates, the preconcentration approach enables the adherence of a greater number of target cells, resulting in a higher concentration of target templates for amplification directly from urine samples. In contrast to conventional methods, which often involve complex procedures, this approach offers a simpler, cost-effective, and user-friendly alternative. Moreover, the integration of cell adhesion, LAMP amplification, and signal readout within paper origami-based devices can provide a portable, robust, and highly efficient platform for rapid nucleic acid detection. This innovative hypothesis holds significant potential for point-of-care (POC) diagnostics and field surveillance applications. Further research and development in this field will advance the implementation of this technology, contributing to improved healthcare systems and public health outcomes.

Immunity elicitors for induced resistance against the downy mildew pathogen in pearl millet.

Pearl millet (Pennisetum glaucum (L.) R. Br.) is a globally important cereal whose production is severely constrained by downy mildew caused by Sclerospora graminicola (Sacc.). In this study, immunity eliciting properties of 3,5-dichloroanthranilic acid (DCA), Cell Wall Glucan (CWG), Lipopolysaccharide (LPS), and Glycinebetaine (GB) was deciphered through enzymatic and protein studies based on elicitor treatment activated defense mechanisms. Glycinebetaine, LPS, CWS and DCA elicited enzyme activities and gene expression of the defense enzymes, such as ß-1,3-glucanase, phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO), lipoxygenase (LOX) and defense protein hydroxyproline-rich glycoproteins (HRGPs). However, the speed and the extent of elicitation differed. High levels of enzyme activities and gene expression in elicitor-treated P. glaucum positively correlated with the increased downy mildew resistance. A very rapid and large changes in elicitor-treated seedlings, in contrast to the delayed, smaller changes in the untreated susceptible control seedlings suggests that the rate and magnitude of defense gene expression are important for effective manifestation of defense against pathogen. As compared to other elicitors and control, GB promoted increase in enzyme activities and gene expression, implicating that GB is a promising elicitor of downy mildew resistance in P. glaucum.

Green Synthesis of Silver Nanoparticles by Cytobacillus firmus Isolated from the Stem Bark of Terminalia arjuna and Their Antimicrobial Activity.

This work reports an eco-friendly synthesis of silver nanoparticles (AgNPs) using endophytic bacteria, Cytobacillus firmus isolated from the stem bark of Terminalia arjuna. The synthesis of AgNPs was confirmed by visual observation as a change in color of the bacterial solution impregnated with silver. Further, the morphology of the AgNPs, average size, and presence of elemental silver were characterized by UV-Visible spectroscopy, scanning electron microscopy, and dynamic light scattering spectroscopy. The roles of endophytic secondary metabolites in the metal reduction, stabilization, and capping of silver nanoparticles were studied by qualitative FTIR spectral peaks. The antimicrobial ability of AgNPs was evaluated against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and pearl millet blast disease-causing fungi (Magnoporthe grisea). The biosynthesized AgNPs showed good antibacterial and antifungal activities. AgNPs effectively inhibited the bacterial growth in a dose-dependent manner and presented as good antifungal agents towards the growth of Magnoporthe grisea.