Tolerance and Physiological Responses in Two Populations of Harmel Plant to Silver Stress, A Suitable Candidate for Accumulation of Ag

By studying harmel plants in Ag metal-contaminated mineral areas, it was found that harmel plants can accumulate Ag metal, so the present study aimed to investigate the effects of Ag exposure (0, 1, 2.5, 5, 10 mgL− 1 Ag) to harmel seedlings. Two populations (metallicolous and non-metallicolous) were compared about Ag tolerance, Ag accumulation, translocation factor (TF), photosynthetic pigments, antioxidant enzyme activity and, non-enzyme metabolite. At first, harmel plants were studied for their ability to accumulate silver metal in a silver metal-contaminated mineral area. Also, the results of hydroponic culture showed that the increase of Ag concentrations in the nutrient solution reduced root length, shoot length, root dry weight, shoot dry weight, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid and, total soluble sugars in both populations, but the accumulation is more pronounced in metallicolous populations than non-metallicolous. In response to this, the antioxidant activities were increased under Ag exposure, and sharp in the metallicolous population. In conclusion, the above results show that harmel seems a suitable candidate for Ag-accumulation; and these findings support the use of harmel as an acceptable species for cultivation in soils that are contaminated with Ag and strategies to minimize the toxicity of Ag in plants.

XPS Study for Chemical Basis of Silver Based Bhasmas

This review concerns the appropriate study of X-ray Photo-electron Spectroscopy to analyze oxidation states in the herbo-mineral drugs. It describes multivalent forms of silver and silver based drugs. Silver exhibits multivalent forms with various phases like AgO, Ag2O and Ag2O3 etc. Silver Bhasma is one of the potent Ayurvedic drug from herbo-metallic combinations. This traditional preparation is used for treating various ailments such as disorders related to eye and nerve, brain functioning and tuberculosis etc. Mixture of silver metal and herbal ingredients passes through Bhasmikarana method and then gets converted into organo-metallic complex i.e. silver Bhasma. The preparation method of Bhasmas aims at removing injurious substances which are foreign to the body from metals. The process of Bhasmikarana transferred the material from its inorganic state to the organic; therefore the assimilation of the substances for their therapeutic use will be easier in the human body. Silver Bhasma plays an essential role in Ayurvedic therapeutics due to its versatile qualities. Therefore, if a Bhasma is to be considered as a standard one, X-ray photoelectron spectroscopy should be one of the essential methods. Scanning electron microscope (SEM) technique was used to detect morphology of silver based Bhasmas and Energy dispersive X-ray spectroscopy (EDAX) detected elemental analysis. X-ray photoelectron spectroscopy is the useful platform to detect important chemical constituents as per their required oxidation states which are essential part in therapeutic use.

Photocatalytic Decomposition of Nitrobenzene in Aqueous Solution by Ag/Cu2O Assisted with Persulfate under Visible Light Irradiation

The mineralization of nitrobenzene was executed using an innovative method, wherein Ag/Cu2O semiconductors stimulated by visible light irradiation were supported with persulfate anions. Batch-wise experiments were performed for the evaluation of effects of silver metal contents impregnated, persulfate concentrations and Ag/Cu2O dosages on the nitrobenzene removal efficiency. The physicochemical properties of fresh and reacted Ag/Cu2O were illustrated by X-ray diffraction analyses, FE-SEM images, EDS Mapping analyses, UV–Vis diffuse reflectance spectra, transient photocurrent analyses and X-ray photoelectron spectra, respectively. Because of intense scavenging effects caused by benzene, 1-propanol and methanol individually, the predominant oxidant was considered to be sulfate radicals, originated from persulfate anions via the photocatalysis of Ag/Cu2O. As regards oxidation pathways, nitrobenzene was initially transformed into hydroxycyclohexadienyl radicals, followed with the production of 2-nitrophenol, 3-nitrophenol or 4-nitrophenol. Afterwards, phenol compounds descended from denitration of nitrophenols were converted into hydroquinone and p-benzoquinone.

Platelet membrane-camouflaged silver metal-organic framework drug system against infections caused by methicillin-resistant Staphylococcus aureus

Background Due to the intelligent survival strategy and self-preservation of methicillin-resistant Staphylococcus aureus (MRSA), many antibiotics are ineffective in treating MRSA infections. Nano-drug delivery systems have emerged as a new method to overcome this barrier. The aim of this study was to construct a novel nano-drug delivery system for the treatment of MRSA infection, and to evaluate the therapeutic effect and biotoxicity of this system. We prepared a nano silver metal-organic framework using 2-methylimidazole as ligand and silver nitrate as ion provider. Vancomycin (Vanc) was loaded with Ag-MOF, and nano-sized platelet vesicles were prepared to encapsulate Ag-MOF-Vanc, thus forming the novel platelet membrane-camouflaged nanoparticles PLT@Ag-MOF-Vanc. Results The synthesized Ag-MOF particles had uniform size and shape of radiating corona. The mean nanoparticle size and zeta potential of PLT@Ag-MOF-Vanc were 148 nm and − 25.6 mV, respectively. The encapsulation efficiency (EE) and loading efficiency (LE) of vancomycin were 81.0 and 64.7 %, respectively. PLT@Ag-MOF-Vanc was shown to be a pH-responsive nano-drug delivery system with good biocompatibility. Ag-MOF had a good inhibitory effect on the growth of three common clinical strains (Escherichia coli, Pseudomonas aeruginosa, and S. aureus). PLT@Ag-MOF-Vanc showed better antibacterial activity against common clinical strains in vitro than free vancomycin. PLT@Ag-MOF-Vanc killed MRSA through multiple approaches, including interfering with the metabolism of bacteria, catalyzing reactive oxygen species production, destroying the integrity of cell membrane, and inhibiting biofilm formation. Due to the encapsulation of the platelet membrane, PLT@Ag-MOF-Vanc can bind to the surface of the MRSA bacteria and the sites of MRSA infection. PLT@Ag-MOF-Vanc had a good anti-infective effect in mouse MRSA pneumonia model, which was significantly superior to free vancomycin, and has no obvious toxicity. Conclusions PLT@Ag-MOF-Vanc is a novel effective targeted drug delivery system, which is expected to be used safely in anti-infective therapy of MRSA. Graphic abstract