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

We describe an in situ method of synthesizing highly branched gold nanoflower (AuNFs) using aqueous seed extract ofSyzygium 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 aureusMTCC 121), two Gram negative (Escherichia coliMTCC 40 andPseudomonas aeruginosaMTCC 4673) and one fungi (Candida albicansMTCC 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 IC50value of 20 µg mL−1.