Exploitation of cantaloupe peels for bacterial cellulose production and functionalization with green synthesized Copper oxide nanoparticles for diverse biological applications

Abstract

The promising features of most bacterial celluloses (BC) promote the continuous mining for a cost-effective production approach toward wide and sustainable applications. Herein, cantaloupe peels (CP) were successfully implemented for sustainable BC production. Results indicated that the enzymatically hydrolyzed CP supported the maximum BC production of approximately 3.49 g/L when used as a sole fermentation media. The produced BC was fabricated with polyvinyl alcohol (PVA) and chitosan (Ch), and loaded with green synthesized copper oxide nanoparticles (CuO-NPs) to improve its biological activity. The novel composite showed an antimicrobial activity against several human pathogens such as Staphylococcus aureus, Streptococcus mutans, Salmonella typhimurium, Escherichia coli, and Pseudomonas fluorescens. Furthermore, the new composite revealed a significant in vitro anticancer activity against colon (Caco-2), hepatocellular (HepG-2), and breast (MDA) cancer cells, with low IC₅₀ of 0.48, 0.27, and 0.33 mg/mL for the three cell lines, respectively. On the other hand, the new composite was remarkably safe for human skin fibroblast (HSF) with IC₅₀ of 1.08 mg/mL. Interestingly, the composite membranes exhibited lethal effects against all stages of larval instar and pupal stage compared with the control. In this study, we first report the diverse potential applications of BC/PVA/Ch/CuO-NPs composites based on green synthesized CuO-NPs and sustainably produced BC membrane.

Figure 1

Schematic representation of the four main steps in the present study: (A) synthesis of BC using CP media, (B) green synthesis of CuO-NPs using POP extract, (C) fabrication of the resulting BC membrane with PVA and Ch, and (D) potential composite applications (D).

Figure 2

Scarification of CP (1), enzymatic hydrolysis rate (2) at different time intervals, and BC production from different media (3).

Figure 3

SEM micrographs of BC membranes (A), nanofiber diameter (B), and pore size diameter (C) using different cultivation regimes; HS (1), JCP (2), ECPS (3), and EPC (4) media where all images of SEM were taken with (scales 1, 5 µm, and original magnification 20,000X with applied voltage of 20 kV).

Figure 4

FT-IR spectra of obtained BC membranes using different regimes of cultivation, HS (1), JCP (2), ECPS (3), and EPC (4) media.

Figure 5

XRD patterns of obtained BC using different regimes of cultivation, HS (1), JCP (2), ECPS (3), and EPC (4) media.

Figure 6

TGA thermograph results of obtained BC using different regimes of cultivation, including HS (PBC), JCP (PBC1), ECPS (PBC2), and EPC (PBC3) media.

Figure 7

Full characterization of prepared CuO-NPs., (a) SEM micrograph (image scale 10 µm, original magnification of 7,000 × and applied voltage of 20 kV), (b) EDX analysis, (c) zeta potential, and (d) particle size analysis.

Figure 8

SEM micrographs of BC/PVA/Ch composite membranes loaded with CuO-NPs (0.025, 0.050, 0.075, and 0.100 mg in (a, b, c, d, and e), respectively). All images were taken with 20μm, original magnification of 5000 x, with applied voltage of 20 kV.

Figure 9

FT-IR analysis of BC/PVA/Ch (1), BC/PVA/Ch/CuO-NPs1 (2), BC/PVA/Ch/CuO-NPs2 (3), BC/PVA/Ch/CuO-NPs3 (4), and BC/PVA/Ch/CuO-NPs4 (5) composite membranes.

Figure 10

XRD patterns of BC/PVA/Ch (1), BC/PVA/Ch/CuO-NPs1 (2), BC/PVA/Ch/CuO-NPs2 (3), BC/PVA/Ch/CuO-NPs3 (4), and BC/PVA/Ch/CuO-NPs4 (5) composite membranes.

Figure 11

The swelling ratio (SR%) of the prepared BC/PVA/Ch at different concentrations of CuO-NPs.

Figure 12

Disk diffusion method for antimicrobial activity expressed as halo-zones of the prepared BC/PVA/Ch at four CuO-NPs concentrations including: 1 (0.025), 2 (0.050), 3 (0.075), and 4 (0.100) compared with 5 (CuO-NPs/free BC/PVA/Ch) against nine pathogenic microorganisms.

Figure 13

Effect of BC/PVA/Ch at four CuO-NPs concentrations on the cell viability of both normal and cancer cells. Normal HSF cells (A) and cancer cell lines of Caco-2 (B), HepG-2 (C), and MDA (D) cells were incubated with discs of the prepared composites at various weights of 0–4.0 mg/mL for 48 h and the viability of all tested cells was assayed by MTT method. All values are representing the average values from three experimental trials and expressed as mean ± SEM.

Figure 14

Effect of BC/PVA/Ch at four concentrations of CuO-NPs on the morphological changes of Caco-2, HepG-2, and MDA cancer cell lines as shown under an inverted phase-contrast microscope. Cells were treated at the IC₅₀ value of each prepared composite membrane and untreated (control) cells were included as negative references.