Differential effects of in vitro cultures of Linum usitatissimum L. (Flax) on biosynthesis, stability, antibacterial and antileishmanial activities of zinc oxide nanoparticles: a mechanistic approach

The use of plants and plant-derived materials for biosynthesis of zinc oxide nanoparticles (ZnO NPs) is developing into a lucrative field of green nanotechnology and gaining more importance owing to its simplicity, rapidity, and eco-friendliness. In present study, a novel and efficient green approach has been developed for biosynthesis of ZnO NPs by exploiting the in vitro platform of plants. Two different in vitro cultures extracts i.e.; callus extract (CE) and adventitious root extract (RE) of Flax were used as a source of reducing and stabilizing agents. Phytochemical analysis revealed that the RE was rich in phytochemical reducing agents as compared to CE. UV-visible spectroscopy showed that the bioreduction of RE-mediated ZnO NPs completed in shorter time than CE-mediated ZnO NPs. Scanning electron microscopy showed that CE- mediated ZnO NPs were spherical with weak agglomeration but the RE-mediated ZnO NPs were hexagonal in shape with uniform distribution of particles. X-ray diffraction analysis showed that the both type of ZnO NPs exhibited the same crystalline nature (wurtzite hexagonal) but vary in their sizes. RE-mediated ZnO NPs were smaller in size (34.97 nm) than CE-mediated ZnO NPs (61.44 nm). Fourier-transform infrared spectroscopy revealed that the polyphenols (lignans), carboxylic acids and aromatic compounds were mainly involved in reduction and capping of both type of ZnO NPs. Moreover, the RE-mediated ZnO NPs showed more potent antibacterial and antileishmanial activity against multidrug resistant bacterial strains and parasite of Leishmania major than CE-mediated ZnO NPs. The present work highlighted the potent role of in vitro cultures of Flax in enhanced biosynthesis, antibacterial and antileishmanial activities of ZnO NPs.