Abstract
Multiple new approaches to tackle multidrug resistant infections are urgently needed and under evaluation. One nanotechnology-based approach to delivering new relevant therapeutics involves silicon accumulator plants serving as a viable silicon source in green routes for the fabrication of the nanoscale drug delivery carrier porous silicon (pSi). If the selected plant leaf components contain medicinally-active species as well, then a single substance can provide not only the nanoscale high surface area drug delivery carrier, but the drug itself. With this idea in mind, porous silicon was fabricated from joints of the silicon accumulator plant Bambuseae (Tabasheer) and loaded with an antibacterial extract originating from leaves of the same type of plant (Bambuseae arundinacea). Preparation of porous silicon from Tabasheer includes extraction of biogenic silica from the ground plant by calcination, followed by reduction with magnesium in the presence of sodium chloride, thereby acting as a thermal moderator that helps to retain the mesoporous structure of the feedstock. The purified product was characterized by a combination of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and low temperature nitrogen gas adsorption measurements. Antimicrobial activity and minimum inhibitory concentration of a leaf extract of Bambuseae arundinacea was tested against the bacteria Escherichia Coli (E. Coli) and Staphylococcus aureus (S. Aureus), along with the fungus Candida albicans (C. Albicans). A S. aureus active ethanolic leaf extract was loaded into the above Tabasheer-derived porous silicon. Initial studies indicate sustained in vitro antibacterial activity of the extract-loaded plant derived pSi (25 wt %, TGA), as measured by disk diffusion inhibitory zone assays. Subsequent chromatographic separation of this extract revealed that the active antimicrobial species present include stigmasterol and 2,6-dimethoxy-p-benzoquinone.
Highlights
The rise in drug-resistant pathogens is of major importance and rightly receiving significant worldwide attention [1]
Washing the product of this reaction with 36% hydrochloric acid dissolves all the traces of magnesium which was confirmed by energy dispersive X-ray analysis (EDX) (S1 Fig)
This magnesiothermic reduction resulted in the formation of porous silicon (pSi) microparticles comprised of an aggregate of small nanoparticles creating nanopores along the microparticle surface, as gauged by transmission electron microscopy (Fig 2a)
Summary
The rise in drug-resistant pathogens is of major importance and rightly receiving significant worldwide attention [1]. A multitude of alternatives to antibiotics are being explored, including the use of specific metallic ions, biomolecules and even predatory pathogens themselves like phages [2]. Plant-derived approaches are promising for supplying indigenous low-cost therapies [3]. They are highly amenable to synergistic approaches where a multitude of antimicrobial weapons are employed [4]. Whilst phytochemistry is an established field, and increasing research is being undertaken on their utility with regard antibiotic-resistant microorganisms [5,6,7], we are not aware of prior studies combining biodegradable biomaterial and antimicrobial extraction from a single type of plant
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