The membrane depolarization and increase intracellular calcium level produced by silver nanoclusters are responsible for bacterial death

This work highlights how our silver ultra nanoclusters (ARGIRIUM-SUNc) hand-made synthesized, are very useful as a bactericide and anti-biofilm agent. The Argirium-SUNc effective antibacterial concentrations are very low (< 1 ppm) as compared to the corresponding values reported in the literature. Different bacterial defense mechanisms are observed dependent on ARGIRIUM-SUNc concentrations. Biochemical investigations (volatilome) have been performed to understand the pathways involved in cell death. By using fluorescence techniques and cell viability measurements we show, for the first time, that membrane depolarization and calcium intracellular level are both primary events in bacteria death. The ARGIRIUM-SUNc determined eradication of different biofilm at a concentration as low as 0.6 ppm. This suggests that the effect of the nanoparticles follows a common mechanism in different bacteria. It is highly probable that the chemical constitution of the crosslinks could be a key target in the disrupting mechanism of our nanoparticles. Since the biofilms and their constituents are essential for bacterial survival in contact with humans, the silver nanoparticles represent a logical target for new antibacterial treatments.

CLSM and TIRF images from lignocellulosic materials: garlic skin and agave fibers study

ABSTRACTFluorescence techniques have been widely used by scientists to reveal valuable information from biological samples, but in food science, small progress is known due to the complexity of the samples. In this study, two different biological samples, garlic skin (GS) and agave fibers (AF), were used to evaluate the techniques of confocal laser scanning microscopy (CLSM) and total internal reflection fluorescence (TIRF) microscopy, to obtain valuable information on the fiber size of the samples. A compositional characterization with calcofluor white in CLSM was achieved, but a superficial characterization of the samples with TIRF was made, evidencing fiber sizes of 398.67 ± 48.47 nm and 677.38 ± 76.88 nm for GS and AF, respectively. This work reveals that only an untreated sample can be used with the two techniques in the same microscope. In addition, it is possible to characterize the sample only using a spatial field of research and which valuable information about the structure of the material is found. This work provides the opportunity to use advanced fluorescence techniques for elucidation of structures shortly before studied with these techniques.

Super-resolution label-free volumetric vibrational imaging

Innovations in high-resolution optical imaging have allowed visualization of nanoscale biological structures and connections. However, super-resolution fluorescence techniques, including both optics-oriented and sample-expansion based, are limited in quantification and throughput especially in tissues from photobleaching or quenching of the fluorophores, and low-efficiency or non-uniform delivery of the probes. Here, we report a general sample-expansion vibrational imaging strategy, termed VISTA, for scalable label-free high-resolution interrogations of protein-rich biological structures with resolution down to 78 nm. VISTA achieves decent three-dimensional image quality through optimal retention of endogenous proteins, isotropic sample expansion, and deprivation of scattering lipids. Free from probe-labeling associated issues, VISTA offers unbiased and high-throughput tissue investigations. With correlative VISTA and immunofluorescence, we further validated the imaging specificity of VISTA and trained an image-segmentation model for label-free multi-component and volumetric prediction of nucleus, blood vessels, neuronal cells and dendrites in complex mouse brain tissues. VISTA could hence open new avenues for versatile biomedical studies.

Highly Sensitive, Naked Eye, and On-Spot Detection of pH Change Using Novel Phenothiazine based Schiff Base

Background: Visual pH sensors have received significant attention in the fields of environmental monitoring, analytical chemistry, food safety and biomedicine. Therefore, a single organic moiety showing both naked-eye and fluorescence sensing of pH change are rare and in higher demands. Objective: A novel phenothiazine based Schiff base PTz-SB was synthesized via facile organic transformations. This molecule showed promising naked-eye and on-spot pH sensing application, both using UV-visible and fluorescence techniques. Method: The novel phenothiazine based Schiff base was synthesized via facile organic transformation. The Schiff base was applied for both naked eye and fluorescence sensing of pH, using UV-visible and fluorescence techniques, respectively. Result: A redshift of 27 nm and 80 nm was observed in the λmax of absorption and emission spectra, respectively, on changing the pH from 12.2 to 1. The naked-eye pH sensing may be attributed to the change in colour from blue (higher pH) to dark green (lower pH), under daylight conditions. Furthermore, the change in fluorescence spectra is more pronounced. The fluorescence colour of the compound changes from dark blue to green and then finally to orange, on changing the pH from 12.2 to 4 to 1.5, respectively. Moreover, the electrochemical studies of the Schiff base were also procured. The bandgap obtained from the cyclic voltammetry studies was found to be 2.04 eV, which is characteristic of green emission. Conclusion: The easily synthesizable novel Schiff base can be utilized for real-life, on-spot practical application of pH sensing, which does not require sophisticated analytical instruments. Moreover, the time and cost of detection of pH using this thermally robust Schiff base are also very promising.

Carbon Dots-Based Logic Gates

Carbon dots (CDs)-based logic gates are smart nanoprobes that can respond to various analytes such as metal cations, anions, amino acids, pesticides, antioxidants, etc. Most of these logic gates are based on fluorescence techniques because they are inexpensive, give an instant response, and highly sensitive. Computations based on molecular logic can lead to advancement in modern science. This review focuses on different logic functions based on the sensing abilities of CDs and their synthesis. We also discuss the sensing mechanism of these logic gates and bring different types of possible logic operations. This review envisions that CDs-based logic gates have a promising future in computing nanodevices. In addition, we cover the advancement in CDs-based logic gates with the focus of understanding the fundamentals of how CDs have the potential for performing various logic functions depending upon their different categories.