Starch-templated bio-synthesis of gold nanoflowers for in vitro antimicrobial and anticancer activities

D Borah,M Hazarika,A R Silva,G Singaravelu,B Chetia,P Tailor,P Das

doi:10.1007/s13204-018-0793-x

Abstract

We describe an in situ method of synthesizing highly branched gold nanoflower (AuNFs) using aqueous seed extract of Syzygium cumini (L.) Skeels as reductant in the presence of 0.3% starch. Surprisingly, when the same reaction was carried out in the absence of starch or with starch at a lower concentration (0.15%), instead of flower-like morphology quasi-spherical or polyhedral nanoparticles (AuNPs) are obtained. The nanomaterials were extensively characterized by HRTEM, FESEM, UV–Vis, FTIR, XRD, XPS and TGA analysis. The biological activities of the materials were investigated for antimicrobial activities against four bacterial strains that include one Gram positive (Staphylococcus aureus MTCC 121), two Gram negative (Escherichia coli MTCC 40 and Pseudomonas aeruginosa MTCC 4673) and one fungi (Candida albicans MTCC 227). The nanoparticles functioned as effective antimicrobial and anti-biofilm agents against all the strains under study. Controlled study revealed that, the AuNFs showed improved efficacy over conventional polyhedral AuNPs against all the microbes under study which might be attributed to the larger surface-to-volume ratio of the nanoflowers. The AuNFs also showed effective in vitro anticancer activity against a human liver cancer cell line (HepG2) with no significant cytotoxicity. Our data suggest that the AuNFs can significantly reduce the cancer cell growth with IC50 value of 20 µg mL−1.

Highlights

Over the past few decades, noble metal nanoparticles have received unprecedented attentions because of their potential utility in various fields such as catalysis, material sciences, heavy metals removal, pharmaceutical sciences, andD
The gold nanoparticles are prepared by a simple in situ method using aqueous seed extract of the plant Syzygium cumini (L.) Skeels and HAuCl4
The formation of Au nanoparticles (AuNPs) was further confirmed by TEM analysis (Fig. 1a, b) and the spectra reveal that the NPs are well dispersed with both spherical and non-spherical morphologies with an average particle size of about 10 nm (Fig. 1c)

Summary

Introduction

As potential source of reductant, with or without the assistance of some naturally occurring stabilizers such as cellulose, carbohydrate polymers such as chitosan, starch, and DNA (Liu et al 2012; Siddiqi and Husen 2017; Opris et al 2017; Phukan et al 2016; Virkutyte and Varma 2011; Tiwari et al 2011; Schreiber et al 2016; Wang et al 2010) These bio-inspired stabilizers protect the NPs against aggregation and sometimes act as soft template to attach smaller particles onto its surface in a particular fashion, forming highly branched flower-like structures (Wang et al 2010). Recently, Ahn et al 2017 reported synthesis of gold nanoflower using an extract of Acanthopanacis cortex and successfully investigated their anti-inflammatory activity

Methods

Results

Conclusion