Green-fabricated silver nanoparticles from Quercus incana leaf extract to control the early blight of tomatoes caused by Alternaria solani

BACKGROUND

Early blight (EB) of Tomatoes, caused by Alternaria solani, is a serious fungal disease that adversely affects tomato production. Infection is characterized by dark lesions on leaves, stems, and fruits. Several agrochemicals can be used to control infection, these chemicals may disrupt environmental equilibrium. An alternative technology is needed to address this significant fungal threat. This study was designed to control the growth of EB in tomatoes caused by A. solani, using green-fabricated silver nanoparticles (Ag-NPs).

RESULTS

Ag-NPs were synthesized through an environmentally friendly and cost-effective approach using leaf extract of Quercus incana Roxb. (Fagaceae). The physico-chemical characterization of the Ag-NPs was conducted through UV-visible spectroscopy, scanning electron microscopy, X-ray diffraction analysis, and Fourier transform infrared spectrometry. The Ag-NPs produced were round with a mean diameter of 27 nm. The antifungal activity of these Ag-NPs was assessed through in vitro Petri plate and in vitro leaflet assays against A. solani. The green fabricated Ag-NPs exhibited excellent antifungal activity in vitro at a concentration of 100 mg/l against A. solani, inhibiting growth by 98.27 ± 1.58% and 92.79 ± 1.33% during Petri plate and leaflet assays, respectively.

CONCLUSION

In conclusion, this study suggests the practical application of green-fabricated Ag-NPs from Q. incana leaf extract against A. solani to effectively control EB disease in tomatoes.

Role of Electrical Conductivity in the Shielding Effectiveness of Composite Polyvinyl Alcohol/Multiwall Carbon Nanotube Nanofibers for Electromagnetic Interference Applications

The shielding effectiveness (SE) against the electromagnetic interference (EMI) of polyvinyl alcohol/multiwall carbon nanotubes (PVA/MWCNTs) composite nanofibers is characteristic of higher absorptivity of the radiation that enhances with the increasing concentration of MWCNTs content in these composites. However, by enriching the content of conductive fillers (MWCNTs), the conductivity of the composites is also stirred up. Concomitantly, the conductivity of these composites contributes toward the reflectivity of the EM radiation from them. Certain applications of the EMI shielding material require a lower level of reflectivity of the EM radiation. This study intends to see how SE of the PVA/MWCNTs composite nanofibers is affected vis-a-vis their conductivity for S-band radiation. Samples of nanofibers, with (5, 10, 15, and 20) wt % of MWCNTs loading in 10 wt % of PVA solution, were prepared through electrospinning and studied for their electrical conductivity and EMI SE. It is observed that by increasing the content of MWCNTs in PVA solution from 5 to 20 wt % the conductivity of the composites tends to increase from 21 to 866 times that of PVA, while the SE increases from 10 db to 25 db over the S-band range of frequencies.

Antibacterial, antioxidant, and anticancer potential of green fabricated silver nanoparticles made from Viburnum grandiflorum leaf extract

BACKGROUND

Recently, researchers are focusing on creating new tools to combat the antibiotic resistant bacteria and malignancy issues, which pose significant threats to humanity. Biosynthesized silver nanoparticles (AgNPs) are thought to be a potential solution to these issues. The biosynthesis method, known for its environmentally friendly and cost-effective characteristics, can produce small-sized AgNPs with antimicrobial and anticancer properties. In this study, AgNPs were bio-fabricated from the distilled water and methanolic extracts of Viburnum grandiflorum leaves. Physio-chemical characterization of the bio-fabricated AgNPs was conducted using UV-visible spectroscopy, scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction analysis.

RESULTS

AgNPs produced from the methanol extract were smaller in size (12.28 nm) compared to those from the aqueous extract (17.77 nm). The bioengineered AgNPs exhibited a circular shape with a crystalline nature. These biosynthesized AgNPs demonstrated excellent bactericidal activity against both gram-negative (Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria. Highest antibacterial activity was observed with the methanol extract against P. aeruginosa (14.66 ± 0.74 mm). AgNPs from the methanol extract also displayed the highest antioxidant activity, with an IC50 value of 188.00 ± 2.67 μg/mL against 2,2-diphenyl-1-picrylhydrazyl (DPPH). Furthermore, AgNPs exhibited notable cytotoxic activity against Rhabdomyosarcoma cell line (RD cell) of human muscle cancer cell. The IC50 values calculated from the MTT assay were 26.28 ± 1.58 and 21.49 ± 1.44 μg/mL for AgNPs synthesized from aqueous and methanol extracts, respectively.

CONCLUSION

The methanol extract of V. grandiflorum leaves demonstrates significant potential for synthesizing AgNPs with effective antibacterial, antioxidant, and anticancer actions, making them applicable in various biomedical applications.

Optimization and bio-fabrication of phyto-mediated silver nanoparticles (Ag-NPs) for antibacterial potential

This report examines the bio-fabrication of silver nanoparticles (Ag-NPs) utilizing AgNO3 and leaf extract of Crataegus monogyna as the precursor material. In order to maximize the antibacterial efficacy against Staphylococcus aureus, Proteus mirabilis, Klebsiella pneumoniae and Pseudomonas aeruginosa, the reaction conditions for the green fabrication of Ag-NPs were optimized. A one factor at a time approach (volume concentration of extract, volume concentration of AgNO3, pH and temperature) was used to optimize the best condition, and results were assessed through UV-visible spectroscopy and particle size distribution. The results showed that 20 mL of plant extract, 80 mL of AgNO3, pH 08, 100 °C temperature were the optimum reaction conditions under which we obtained the smallest Ag-NPs (7 nm). The scanning electron microscopy and X-ray diffraction analysis confirmed the spherical and crystalline nature of Ag-NPs. The antibacterial activity assay demonstrated a high antibacterial effect of Ag-NPs against S. aureus, P. mirabilis, K. pneumoniae and P. aeruginosa, and that impact was greater with smaller-sized nanoparticles (7 nm). This study shows that leaf extract of C. monogyna is a possible medium for the green fabrication of Ag-NPs, and control over reaction factors can establish the characteristics and antibacterial effectiveness of Ag-NPs.Communicated by Ramaswamy H. Sarma.

Design, analysis, and experimental investigation of micro-displacement amplification compliant mechanism for micro-transducers

This paper presents experimental force and buckling analysis of a compliant micro-displacement amplification mechanism fabricated using the commercially available PolyMUMPs process. The proposed mechanism proficiently amplifies displacement, at two output ends, with an optimal amplification factor of 7.2. Buckling analysis revealed that an amplification factor ranging from 2.8 to 11 may be achieved for an input displacement varying from 0.1 to 7.5 µm. Based on the analysis, the optimal value of the amplification factor is found to be 7.2 with an input displacement of 3.5 µm at the operational force of 60 μN having a buckling load factor (BLF) >1. Critical load magnitude is 187 μN having BLF = 1. Buckling occurred when loading exceeded the critical load value, having BLF <1, and the mechanism failed to produce a significant amplification factor. Static analysis showed that stresses produced are within the safe region, and the structural integrity of the mechanism is not compromised having a factor of safety of 1.4. Modal analysis predicted that the natural frequency of the desired mode is 35.47 kHz. Dynamic simulations, under 15 g dynamic load with a frequency range of 30-40 kHz, confirm the possibility of integrating the proposed mechanism with MEMS devices. Parametric optimization comprehends that length and angle are the two major geometric parameters that govern the working range, force, and amplification factor. For input displacements below 1 µm, the amplification factor is even higher, which is highly beneficial for amplifying small displacements. Static, modal, and dynamic analyses of the designed mechanism have been carried out using finite element method based commercial software IntelliSuite^®. The experimental results showed that this mechanism can provide the same amplified displacement at two output points and is self-sufficient to be incorporated as an intermediate compliant mechanism for enhancing the output in the case of both static and dynamic micro-devices.

Theoretical-Computational Study of Atmospheric DBD Plasma and Its Utility for Nanoscale Biocompatible Plasmonic Coating

In this study, time-dependent, one-dimensional modeling of a surface dielectric barrier discharge (SDBD) device, driven by a sinusoidal voltage of amplitude 1-3 kV at 20 kHz, in argon is described. An SDBD device with two Cu-stripe electrodes, covered by the quartz dielectric and with the discharge gap of 20 × 10-3 m, was assumed, and the time-dependent, one-dimensional discharge parameters were simulated versus time across the plasma gap. The plasma device simulated in the given arrangement was constructed and used for biocompatible antibacterial/antimicrobial coating of plasmonic particle aerosol and compared with the coating strategy of the DBD plasma jet. Simulation results showed discharge consists of an electrical breakdown, occurring in each half-cycle of the AC voltage with an electron density of 1.4 × 1010 cm-3 and electric field strength of 4.5 × 105 Vm-1. With SDBD, the surface coating comprises spatially distributed particles of mean size 29 (11) nm, while with argon plasma jet, the nanoparticles are aggregated in clusters that are three times larger in size. Both coatings are crystalline and exhibit plasmonic features in the visible spectral region. It is expected that the particle aerosols are collected under the ionic wind, induced by the plasma electric fields, and it is assumed that this follows the dominant charging mechanisms of ions diffusion. The cold plasma strategy is appealing in a sense; it opens new venues at the nanoscale to deal with biomedical and surgical devices in a flexible processing environment.

Green synthesis of silver nanoparticles and their applications as an alternative antibacterial and antioxidant agents

Antimicrobial resistance is a complex global health challenge today. Discovery and development of new natural alternates with novel targets is utmost priority. In this experiment, alternative antibiotic agents in the form of silver nanoparticles (SNPs) and Achillea millefolium L. extracts were evaluated for antibacterial and antioxidant activity. The SNPs were synthesized using aqueous, ethanol and methanol extracts of A. millefolium and were monitored by a color change and UV-vis spectroscopy. The size and shape of the nanoparticles were determined through scanning electron microscopy and phase was assessed through X-ray diffraction. The SNPs were shown to have an average diameter of 20.77, 18.53 and 14.27 nm with spherical, rectangular and cubical shapes, synthesized from aqueous, ethanol and methanol extract respectively. The response of biomolecules present in plant extract during the formation of SNPs was analyzed by Fourier transform infrared spectrometry, showing polyphenols, proteins, carboxylic acid and alcohol are involved in the formation of SNPs. The plant extracts and SNPs were then studied for their antibacterial potential against common human pathogens such as gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa), displaying a very good activity against both types of bacteria. The Methanol-SNPs exhibit greater inhibition of DPPH radicals with IC₅₀ 7.03 ± 0.31 μg/mL. This green method of synthesis of SNPs would support the production of SNPs with considerably boosted antibacterial and antioxidant properties and significantly enhanced therapeutic performance.

Altered accelerator pedal control in a driving simulator in people with diabetic peripheral neuropathy

AIM

To investigate whether the sensory-motor impairment attributable to diabetic peripheral neuropathy would affect control of the accelerator pedal during a driving simulator task.

METHODS

A total of 32 active drivers, 11 with diabetic peripheral neuropathy (mean ± sd age 67±5.0 years), 10 with diabetes but no neuropathy (diabetes group; mean ± sd age 62±10 years), and 11 healthy individuals without diabetes (healthy group; mean ± sd age 60±11 years), undertook a test on a dynamometer to assess ankle plantar flexor muscle strength and ankle joint proprioception function of the right leg, in addition to a driving simulator task. The following variables were measured: maximal ankle plantar flexor muscle strength; speed of strength generation (Nm/s); and ankle joint proprioception (ankle repositioning error, degrees). In the driving simulator task, driving speed (mph), accelerator pedal signal (degrees) and the duration of specific 'loss-of-control events' (s) were measured during two drives (Drive 1, Drive 2).

RESULTS

Participants with diabetic peripheral neuropathy had a lower speed of strength generation (P<0.001), lower maximal ankle plantar flexor muscle strength (P<0.001) and impaired ankle proprioception (P=0.034) compared to healthy participants. The diabetic peripheral neuropathy group drove more slowly compared with the healthy group (Drive 1 P=0.048; Drive 2 P=0.042) and showed marked differences in the use of the accelerator pedal compared to both the diabetes group (P=0.010) and the healthy group (P=0.002). Participants with diabetic peripheral neuropathy had the longest duration of loss-of-control events, but after one drive, this was greatly reduced (P=0.023).

CONCLUSIONS

Muscle function, ankle proprioception and accelerator pedal control are all affected in people with diabetic peripheral neuropathy, adversely influencing driving performance, but potential for improvement with targeted practice remains possible.

Electrospun Microbial-Encapsulated Composite-Based Plasticized Seed Coat for Rhizosphere Stabilization and Sustainable Production of Canola ( Brassica napus L.)

Plant-growth-promoting bacteria show promises in crop production; nevertheless, innovation in their stable delivery is required for practical use by farmers. Herein, the composite of poly(vinyl alcohol)/poly(vinylpyrrolidone) plasticized with glycerol and loaded with the microbial consortium ( Bacillus subtilis plus Seratia marcescens) was fabricated and engineered onto canola ( Brassica napus L.) seed via electrospinning. Scanning electron microscopy showed that the biocomposite is a one-dimensional membrane, which encapsulated microbes in a multilayered nanostructure, and their interfacial behavior between microorganism and seed is beneficial for safer farming. A universal testing machine and thermogravimetric analysis demonstrated that the biocomposite holds sufficient thermomechanical properties for stable handling and practical management. A spectroscopic study resolved the living hybrid-polymer structure of the biocomposite and proved the plasticizing role of glycerol. A swelling study supports the degradation of the biocomposite in the hydrophilic environment as a result of the leaching of the plasticizer, which is important for the sustained release of microbial cells. A shelf life study supported that the biocomposite seed coat placed a threshold level of microbes [5.675 ± 0.48 log₁₀ colony forming units (CFU)/seed] and maintained their satisfactory viability for 15 days at room temperature. An antifungal and nutrient-solubilizing study supported that the biocomposite seed coat could provide opportunities to biocontrol diseases and improve nutrient acquisition by the plant. A pot study documents the better performance of the biocomposite seed coat on seed germination, seedling growth, leaf area, plant dry biomass, and root system. A chemical and microbial study demonstrated that the biocomposite seed coat improved the effectiveness of the bioinoculant in the root-soil interface, where they survive, flourish, and increase the nutrient pool status. In particular, this study presents advances in the fabrication of the biocomposite for encapsulation, preservation, sustained release, and efficacious use of microorganisms onto seeds for precision farming.

Optic flow direction coding in area PEc of the behaving monkey

The cortical representation of heading perception derives from several functional processes distributed across many cortical areas. The aim of the present study was to assess if the optic flow motion directions, expansion and contraction, differently modulate the firing activity of area PEc neurons. We determined the influence of the eye position and/or the spatial position of the focus of expansion (FOE) on this activity. Single neuron activity during radial optic flow stimulation was recorded in three behaving monkeys. The retinal FOE position and the spatial eye position were examined in order to study eye position's influence upon the directional selectivity for the radial stimuli. We observed that the neurons able to discriminate the retinotopic FOE position are differently modulated by expansion and contraction. One class of neurons exhibited a different preferred FOE position during expansion and contraction. A second class showed the same preferred position with similar firing activity in the two stimuli. A third class showed the same preferred position but different firing activity. Eye position affected the directional selectivity of most PEc cells. The main result of this study is that there is a continuum in cell modulation by optic flow direction, and it can be modified by the angle of gaze with respect to the FOE. These results shed light on potential cellular integrative mechanisms of area PEc in heading perception.

Effect of early isolation on signal transfer in the entorhinal cortex–dentate–hippocampal system

Deprivation of socio-sensory interactions during early life impairs brain function in adulthood. In previous investigations we showed that early isolation severely affects neuron development in several structures of the hippocampal region, including the entorhinal cortex. In the present study we investigated the effects of early isolation on signal processing along the entorhinal cortex-dentate-CA3-CA1 system, a major memory circuit of the hippocampal region. Male and female guinea-pigs were assigned at 6-7 days of age to either a social or an isolated environment. At 90-100 days of age the animals were anesthetized and field potentials were recorded from the entorhinal cortex-dentate-CA3-CA1 circuit, driven by dorsal psalterium commissural volleys. Analysis of the input-output function in the different structures showed that in isolated males there was a small reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in layer II of the entorhinal cortex. No changes occurred in isolated females. In isolated males and females there was a reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in the dentate gyrus, CA3 and CA1, but this effect was larger in males. In isolated males, but not in females, the population spike/population excitatory postsynaptic potential ratio was reduced in all investigated structures, indicating that in males the size of the discharged neuron population was reduced more than due to the decreased input. Results show that isolation reduces the synaptic function in the whole entorhinal cortex-dentate gyrus-CA3-CA1 system. While the entorhinal cortex was moderately impaired, the dentate-hippocampal system was more severely affected. The impairment in the signal transfer along the entorhinal cortex-dentate gyrus-CA3-CA1 system was heavier in males, confirming the larger susceptibility of this sex to early experience. This work provides evidence that malfunctioning of a major hippocampal network may underlie the learning deficits induced by impoverished surroundings during early life.

Effects of early isolation on layer II neurons in the entorhinal cortex of the guinea pig

Previous studies showed that early environmental conditions severely affect the morphology of the granule cells in the hippocampal dentate gyrus and pyramidal neurons in fields CA3 and CA1. The aim of the present study was to determine whether early isolation affects neuron morphology in layer II of the entorhinal cortex, from which the perforant path to the dentate gyrus and CA3 takes its origin. Male and female guinea pigs were assigned at 6-7 days of age to either a control (social) or an isolated environment where they remained for 80-90 days. The brains were Golgi-Cox stained and neurons were sampled from layer II of the entorhinal cortex. Morphometric analysis was carried out on star cells, the most abundant neuron population. Isolated males had star cells with less dendritic branches, a shorter dendritic length and a smaller dendritic spine density than control males. In contrast, isolated females had more dendritic branches than control females, though this difference was of small magnitude. While isolated males had star cells with a smaller soma than control males, isolated females had a soma larger than control females. In both environments sex differences were found in the star cell morphology. In the control environment males had more dendritic branches, a greater dendritic length, a larger soma but a smaller spine density than females. In the isolated environment males had less branches, a shorter dendritic length, a smaller spine density and a smaller soma than females. The results indicate that early isolation affects the structure of the star cells in the entorhinal cortex and that males and females react to isolation in an opposite manner. A similar sexually dimorphic response to early isolation was previously observed in the dentate gyrus and fields CA3 and CA1. The presence of widespread effects of isolation in the entorhinal cortex and numerous hippocampal structures suggests that the outcome of early isolation might be a change in learning and memory functions requiring the hippocampal region.

Visual motion responses of neurons in the caudal area pe of macaque monkeys

Area PE of macaques has traditionally been considered a somatosensory association cortex. Recent studies, however, suggest that neurons of this and neighboring areas are involved in the visual control of movement, especially arm movement. We investigated the neuronal sensitivity to local visual stimuli of this region by recording neuronal activity in two behaving macaque monkeys trained in a simple visual fixation task. Recordings were performed from the dorsal surface of the caudal pole of the superior parietal lobule (SPL). Classical receptive fields (RFs) were mapped by using conventional static or moving luminous figures. We found that many neurons in this area were selectively activated by moving visual stimuli. Cell responses were tuned to the movement direction. RFs were usually large; their mean surface covered some 30 x 30 degrees of the visual field. The fovea was often included into RF, in many cases it was along a RF side. The center of RFs was mainly located in the contralateral hemifield, although RFs having the center ipsilaterally sited were also found. No evident retinotopy was found. Visual neurons were especially concentrated in a region of the SPL likely corresponding to area PEc. These results suggest that the caudal part of area PE contains neuronal populations specifically signaling local visual motion, possibly encoding the direction of moving objects. These signals might well be suited for sensorimotor integration mechanisms aimed at motor acts.