Biosynthesis of pure hematite phase magnetic iron oxide nanoparticles using floral extracts of Callistemon viminalis (bottlebrush): their physical properties and novel biological applications

Figures & data

Figure 1. General layout of the study; from biosynthesis to application.

Figure 2. Schematic representation of the plausible biosynthesis mechanism.

Figure 3. XRD spectra of biogenic IONPs after annealing them at various temperatures.

Table 1. Size and lattice strain measured using XRD.

hkl	012	104	110	113	202	024	116	122	214	Avg. (nm)
300 °C
Size	35.41	33.66	23.98	36.46	27.86	28.64	34.48	29.72	36.50	31.74
Strain	0.0099	0.0031	0.0060	0.0050	0.0033	0.0025	0.0027	0.0025	0.0066	0.0046
400 °C
Size	17.33	35.56	23.24	25.47	36.33	32.19	21.52	31.23	10.58	25.93
Strain	0.0048	0.0032	0.0090	0.0072	0.0182	0.0047	0.0043	0.0038	0.0042	0.0066
500 °C
Size	12.3	29.65	28.86	29.69	17.72	21.64	14.84	11.78	20.71	20.79
Strain	0.0128	0.0047	0.0044	0.0029	0.0151	0.0198	0.0201	0.0433	0.0033	0.0146

Figure 4. (A–C) HR-SEM images of biogenic IONPs; (D–F) their SAED pattern.

Figure 5. (A–C) HR-TEM images of biogenic IONPs annealed at 300 °C; (D–F) at 400 °C; (G–I) at 500 °C.

Figure 6. (A) UV absorption spectra of biogenic IONPs at 300, 400 and 500 °C (B) EDS spectra.

Figure 7. (A) FTIR spectrum of biogenic IONPs at 300, 400 and 500 °C (B) Magnetization curves of biogenic iron oxide nanoparticles.

Table 2. Coercivity values measured for each IONP sample.

Sample name	Coercivity at 300K
Fe2O3 – 300 °C	0.00011
Fe2O3 – 400 °C	0.00023
Fe2O3 – 500 °C	0.00049

Figure 8. Antieleishmanial potential of biogenic IONPs.

Figure 9. Anticancer potential of bioinspired IONPs.

Figure 10. Possible cytotoxic mechanism. (A) Extracellular ROS generations (which can easily penetrateinside the cell) followed by their interference with nuclear material, leading to genotoxicity. (B) IONPs are internalized by receptor-mediated endocytosis, followed by their entry into the lysosomes, where Fe2+ dissolution occurs. (C) Surface defects in IONP?s can result in rupturing of cellular membranes. The mechanism have been developed through the work ofearlier researchers. (D) The generated ions not only interfere with other proteins, but also make their way into the mitochondria, where they disrupt its function by creating further ROS. Adapted from [11].

Figure 11. MIC’s of tested bacterial strains using biogenic IONPs.

Table 3. Antibacterial activities of biogenic iron oxide nanoparticles.

	% Inhibition with respect to particle concentration
Name of bacterial strain	12.5µg/mL	25 µg/mL	50 µg/mL	100 µg/mL	200 µg/mL	250 µg/mL	500 µg/mL	1000 µg/mL
Gram –ve strains
Klebsiella pneumonia	1.66	4.66	28.66	39	44.66	69.66	88.33	96.76
Proteus vulgaris	0	23.66	37.33	54.66	68.66	71.33	89	98.33
Escherichia coli	9.33	16.33	21.33	34.33	38.66	69	80.66	87.66
Citrobacter	10	16.33	25.66	42.66	57.66	66.66	86.33	92.66
Vibrio cholera	0	14	20.33	30.33	58	69	84	90.33
Salmonella enterica	3.66	32.33	38.33	47.66	65	76	90.66	94
Shigella dysenteriae	1	6.33	7.33	15	37.33	38.33	61.33	78.66
Cronobacter sakazakii	0	0	0.66	31.66	36.66	37.33	58.66	86.33
Salmonella typhi	3.33	10.33	28.33	35.66	52.66	66.33	82	93.33
Gram + ve strains
Streptococcus pyogenes	0	5.33	28.33	49	68.66	77.9	92.8	97.66
Staphylococcus aureus	3.33	19	42.33	59.33	69.33	85.66	88	95
Staphylococcus epidermidis	5	13.43	21	38.66	65.33	67.66	72	86.66

Figure 12. Enzyme inhibition potential of biomodulated IONPs.

Figure 13. Schematic representation of the inhibition of choline esterase by magnetic IONPs. (A,B) indicate the formation of acetyle choline which is catalyzed by acetyle choline transferase enzyme in the transmitting neurons. (C) indicate the normal conditions where acetyle choline can reach the reciveing neurons. (D) in the presence of choline esterases, acetyle choline is degraded and is unable to transmit the signal. (E) shows nanoparticles inhibitng the choline esterase enzyme which allows the neurotransmitter to transmit the signal.

Figure 14. Antioxidant potential of biogenic IONPs.

Figure 15. Hemolytic activity of bioinspired IONPs against RBC’s.

Table 4. IC₅₀ Values calculated for various biological assays.

Assay	IC50
Promastigote Leishmania tropica	40.8 µg/mL
Aromastigote Leishmania tropica	56.28 µg/mL
Liver cancer (HepG2 cell lines)	20 µg/mL
Hemolytic activity	>200 µg/mL
α-Glucosidase inhibiton	>200 µg/mL
AChE inhibition	83.05 µg/mL
BChE inhibiton	180.71 µg/mL

Khalil AT, Ovais M, Ullah I, et al. Biosynthesis of iron oxide (Fe2O3) nanoparticles via aqueous extracts of Sageretia thea (Osbeck.) and their pharmacognostic properties. Green Chem Lett Rev. 2017;10:186–201.

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