A novel process for size controlled biosynthesis of gold nanoparticles using bromelain

• Biosynthesis of bromelain encapsulated GNps.
• GNps of desired sizes were synthesized by varying conc. of bromelain at 40 oC.
• With increase in conc. of bromelain and temp. size of GNps increases.

There are various synthetic methods known for the synthesis of gold nanoparticles (GNPs); however, they possess potential environmental as well as biological risks. In addition to this, the methods are characterized by very low efficiency. Herein, we report a simple novel method for the synthesis of GNPs from chloroauric acid using bromelain (a cysteine protease) as a reducing as well as capping agent. GNPs of desired sizes were obtained by altering the concentration of bromelain and the temperature of incubation. Monodispersed GNPs with low size distribution (i.e. 8.59–12.92 nm) were produced using 0.33 mg/mL of bromelain at 40 °C. On the other hand, the sizes of GNPs increased with increase in both the concentration of bromelain and incubation temperature. Moreover, GNPs synthesized by this method are stable for several months at room temperature of the reaction. Thus, this method offers an environmentally friendly, single-step approach for fabricating different sizes of stable GNPs which have great potential in the commercial-scale manufacturing of nanoparticles.