Laccases are multi-copper
oxidase enzymes having widespread applications in various biotechnological
fields. However, low stability of free enzymes restricts their industrial
use. Development of effective methods to preserve and even increase
the enzymatic activity is critical to maximize their use, though this
remains a challenge. In the present study we immobilized Trametes versicolor laccase on pH-responsive (and
charge-switchable) Pluronic-stabilized silver nanoparticles (AgNPsTrp). Our results demonstrate that colloidal stabilization
of AgNPsTrp with the amphiphilic copolymer Pluronic F127
enhances enzyme activity (AgNPsTrpF1 + Lac6) by changing the active
site microenvironment, which is confirmed by circular dichroism (CD)
and fluorescence spectroscopy. Detailed kinetic and thermodynamic
studies reveal a facile strategy to improve the protein quality by
lowering the activation energy and expanding the temperature window
for substrate hydrolysis. The immobilized nanocomposite did not show
any change in flow behavior which indirectly suggests that the enzyme
stability is maintained, and the enzyme did not aggregate or unfold
upon immobilization. Finally, assessing the anticancer efficacy of
this nanocomposite in breast cancer MCF-7 cells shows the inhibition
of cell proliferation through β-estradiol degradation and cells
apoptosis. To understand the molecular mechanism involved in this
process, semi qRT-PCR experiments were performed, which indicated
significant decrease in the mRNA levels of anti-apoptotic genes, for
example, BCL-2 and NF-kβ,
and increase in the mRNA level of pro-apoptotic genes like p53 in treated cells, compared to control. Overall, this
study offers a completely new strategy for tailoring nano-bio-interfaces
with improved activity and stability of laccase.