Silver Nanoparticles Obtained by Aqueous or Ethanolic Aloe vera Extracts: An Assessment of the Antibacterial Activity and Mercury Removal Capability

Abstract

Silver nanoparticles (AgNPs) were synthesized by chemical reduction of Ag + ions (from silver nitrate AgNO 3 ), using aqueous or ethanolic Aloe vera extracts as reducing, stabilizing, and size control agent. The nanoparticles' sizes were between 2 and 7 nm for ethanolic extract and between 3 and 14 nm for aqueous extract, as measured by High-Resolution Transmission Electron Microscope (HRTEM). The antibacterial activity against a mesophilic microorganism, Kocuria varians, a Gram-positive coccus, was measured by counting bacterial colonies in agar plate for both extracts. We found that 4% effective concentration is the lowest concentration that completely inhibited visible growth. Mercury removal was investigated by Atomic Absorption Spectroscopy (AAS) measurements, where it was shown that it is not necessary to use high concentrations of nanoparticles for effective removal of mercury inasmuch as with a 20% V/V concentration of both extracts; the Hg(II) removal percentage was above 95%. These results show that the mercury remaining unremoved from the different essays is below the level allowed by World Health Organization (WHO) and the Environmental Protection Agency (EPA).

Antibacterial Polyelectrolytic chitosan derivatives conjugated natural rubber latex films with minimized bacterial adhesion

“…The increased charge density provide a better reach to the negatively charged bacterial cell membrane. [16] However, in case of QCS, DS Q is low compared to many studies [16,49] and the aqueous environment has reduced the chances of further protonation.…”

“…[40,41] The reduction in intensity FT-IR peak between 1,159 cm −1 and 1,050 cm −1 also supports the attachment of alkyl group at C3 and C6 -OH group. [16]…”

“…The better reach towards the bacterial cell membrane by increased positive charge in the main chain itself is not enough to provide improved antibacterial activity. [16,19,50] The lower DS Q due to over methylation [50] also might be one of the reason behind the lower antibacterial activity. Quarterization can provide an improved hydrophilicity to the molecule.…”

Green synthesis of silver nanoparticles using cauliflower waste and their multifaceted applications in photocatalytic degradation of methylene blue dye and Hg2+ biosensing

“…Several research studies have successfully synthesized AgNPs using extracts prepared from fresh plant material of Ocimum sanctum (Tulsi), olive leaf, Amaranthus gangeticus (Chinese red spinach), Citrullus lanatus, Datura stramonium, coffee, Azadirachta indica (neem), Matricaria recutita (Babunah), Aloe vera etc. [11,15,20,21,[25][26][27][28][29]. Alternatively, fruit and vegetable wastes have also been utilized for synthesizing AgNPs with the purpose of curbing their overwhelming burden on the environment [24,[30][31][32].…”

Mangifera indica Mediated Synthesis of Silver Nanoparticles as An Efficient Electrochemical Sensor for The Detection of Ascorbic Acid

“…Biological methods of nanoparticles synthesis using microorganisms [3], enzyme [4] and plant or plant extracts [5] have been suggested as possible eco-friendly alternatives to chemical and physical methods. Although many plants extract, some of which include, Azadirachta indica, Aloe barbadensis, Musa paradisiaca, Saccharum officinarum, Basella alba, Mangifera indica, Oryza sativa and others [6][7][8][9][10][11][12] have been successfully used in the synthesis of metal nanoparticles. This study seeks to synthesize silver nanoparticles using leaves extract of Mangifera indica and show its electrochemical behavior towards the detection of ascorbic acid.…”