Biosynthesis of silver nanoparticles from Aloe vera plant extract and its antimicrobial activity against multidrug resistant pathogens

Abstract

Aloe vera is a stem less or very shortstemmed succulent plant growing to 60-100 cm (24-39 in) tall, spreading by offsets. The leaves are thick and fleshy, green to grey-green, with some varieties showing white flecks on the upper and lower stem surfaces. In recent years, researchers in the field of nanotechnology are finding that metal nanoparticles have all kinds of previously unexpected benefits.A new branch of nanotechnology is nanobiotechnology. Nanobiotechnology represents an economic alternative for chemical and physical methods of nanoparticles formation. When compare to physical and chemical methods biological methods have emerged as an alternative to the conventional methods for synthesis of NPs. Synthesis of inorganic nanoparticles by biological systems makes nanoparticles more biocompatible and environmentally benign. Many bacterial as well as fungal species have been used for silver nanoparticles synthesis. But most of them have been reported to accumulate silver nanoparticles intracellularly. Intracellular synthesis always takes longer reaction times and also demands subsequent extraction and recovery steps. On the contrary, plant extract mediated synthesis always takes place extracellularly, and the reaction times have also been reported to be very short compared to that of microbial synthesis. In the present study young fresh plant stems were collected and the inner green flesh was used for the synthesis of silver nanoparticles. 20 mL of aqueous extract was added to 20 mL of 1mM silver nitrate solution. The solution was allowed to react at room temperature and incubated in dark condition. After 24hrs the color change was observed and the extract was subjected to UV - Visible studies. Though the plasmon band is broad due to the presence of components in extract which are also being read in the spectrophotometric range, it is observed that the silver surface plasmon resonance (SPR) occurs at 460nm. Here is no change in peak position, suggesting that nucleation of silver nanoparticles starts with initiation of reaction time only, and the size remains unchanged throughout the course of reaction. The antibacterial activity was conducted against E.coli, and Bacillus Species. Bioreduced silver nanoparticles showed considerable growth inhibition of two of the well-known pathogenic bacteria species. Zones of 11 mm and 10 mm were observed for E. coli and Bacillus Species respectively.