Controlling the size, shape, and stability of SeNPs by bromelain: Improved antioxidant, anti-bacterial and anti-cancer activities

Abstract

Selenium nanoparticles (SeNPs) are of great interest due to their pharmaceutical importance. We describe an advanced procedure to prepare highly stable SeNPs with controllable size by utilizing stem bromelain (BR) as a capping agent in a redox system of ascorbic acid and sodium selenite. We characterized the bromelain capped SeNPs by a number of complementary techniques including dynamic light scattering (DLS), fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, circular dichroism (CD) and fluorescence spectroscopy. The mean dimensions of SeNPs and BR-SeNPs observed are 50.8 nm, 40.6 nm, and a Zeta potential of −14.6 and −4.37 were observed respectively. Further, we observed that bromelain concentration and temperature are critical factors in controlling the dimensions of BR-SeNPs. It was found that bromelain modified the biological activity of SeNPs. BR-SeNPs exhibited higher DPPH scavenging than SeNPs and bromelain. The anticancerous activity of the nanoparticles was studied in two human cancer cell lines, colorectal SW-480 and breast cancer MDA-MB-231. Colorectal carcinoma exhibited more sensitivity to BR-SeNPs (11.61 μg/mL). The normal cell line studies showed that the BR-SeNPs have low toxicity. When tested against four human pathogenic bacterial species (Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, and Xanthomonas oryzae), BR-SeNPs exhibited a zone of inhibition that was approx. two times wider, at 5 mm when compared to native bromelain. Our study offers new insight into how bromelain capping can tune the size, shape, and stability of SeNPs and provides new bases for using distinct proteins to engineer nanoparticles with enhanced anticancer, antibacterial, and antioxidant activities.