Polyethyleneimine functionalized green synthesized gold nanoparticles for laccase immobilization: Biodegradation of 17β-estradiol and in vitro cytotoxicity against prostate cancer PC-3 cells

Laccases are multi-copper oxidase enzymes that are used significantly in many different biotechnological fields. However, the free enzymes have limited industrial utility because of their low stability. There is a need to develop efficient methods to maintain and enhance enzymatic activity which is a prerequisite for their optimal utilization. In the present study, Trametes versicolor laccase was immobilized on gold nanoparticles (AuNPs) fabricated by using bark extract of Terminalia arjuna. Positively charged cationic polymer, polyethyleneimine (PEI) was used to immobilize laccase through electrostatic interactions. The immobilized enzyme exhibited good activity [effectiveness factor (η): 0.72], and displayed high thermal and storage stability as compared to the free form of the enzyme. The immobilized laccase exhibited better reusability, maintaining 48 % activity after 12 cycles. 17β - estradiol is an estrogenic pollutant that causes prostate cancer. The immobilized enzyme efficiently degraded 17β - estradiol. MTT assay showed dose dependent cytotoxicity of AuNP-PEI-laccase on prostate cancer (PC-3) cells. Therefore, laccase immobilized on green synthesized AuNPs exhibits enhanced stability and in vitro cytotoxicity against PC-3 cells.