An article recently published in the journal Scientific Reports discussed the removal of azithromycin (Azr) antibiotic from contaminated wastewater using hematite nanoparticles (α-HNPs), which were biofabricated from a perennial medicinal herb, Echinacea purpurea.

The adsorption studies revealed the Azr removal capacity of α-HNPs from contaminated pharmaceutical wastewater. Additionally, the parameters like adsorption kinetics, isotherm, and thermodynamics were investigated to understand the adsorption process of Azr on the α-HNPs surface.

Anticancer, antibacterial, and antiviral properties of Azr@α-HNPs were assessed, and the results revealed a better synergistic effect of Azr@α-HNP nanosystems against Gram-positive bacteria compared to Gram-negative bacteria. Moreover, the half-maximal inhibitory concentration (IC50) of Azr@α-HNPs was measured to evaluate its cytotoxic effect against HepG2, MCF7, and HCT116 cell lines, and the results revealed IC₅₀ concentrations of 81.7 (HepG2), 78.1 (MCF7), and 93.4 (HCT116) microgram per milliliter, respectively.

Thermodynamic studies confirmed that the adsorption of Azr on α-HNPs was via a spontaneous endothermic chemisorption process. Furthermore, the antiviral activity of Azr@α-HNP nanosystem against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) showed a safety therapeutic index of 25.4, suggesting its promising antiviral activity.

Nanomaterials Towards Wastewater Treatment

Antibiotics of the macrolide family (Azr) and cephalosporin family (ceftriaxone and cefixime) are used in treating cancerous and viral diseases. The unique physicochemical properties of nanomaterials offer advantages in designing nanocarriers to carry various drugs efficiently inside a biological system. Thus, loading the antibiotics into biocompatible nanomaterials could result in effective drug delivery systems.

The growing demand for macrolide and cephalosporin antibiotics resulted in their production in large quantities. Consequently, the wastewater from pharmaceutical factories and hospitals contaminated with antibiotics pollute the aquatic environment on entering water bodies. Furthermore, the excess presence of antibiotics in the human body may cause necrosis of the renal tubules and induce antibiotic resistance.

Removal of Azr is possible via physicochemical methods such as advanced oxidation using ozone and the photodegradation process. Adsorption is a cost-effective and facile process with high-performance efficiency and does not pose a risk of producing highly toxic by-products. It is one of the most effective and safe strategies to remove antibiotics from aqueous environments.

Previous reports mentioned the use of iron oxide nanoparticles in water treatment techniques. Iron oxide offers desirable characteristics such as high adsorption capacity of organic pollutants, high surface area, and magnetizing ability, favorable for water treatment techniques.

α-HNPs and Azr@-HNPs

In the present study, the researchers used α-HNP-based nano-adsorbents to assess the remediation and removal of the Azr antibiotic via adsorption technology. This study discussed the quadruple use of α-HNPs: firstly, as a bioadsorbent to remove Azr antibiotic found in the wastewater from pharmaceutical factories; secondly, using Azr@α-HNPs as an antibacterial agent against Gram-positive and Gram-negative bacteria; thirdly, comparing the efficacies of Azr@α-HNPs and α-HNPs alone as anticancer agents; and finally, in examining the efficiency of Azr@α-HNPs as nano-drug-delivery against coronavirus.

The transmission electron microscope (TEM) images revealed that the average particle sizes of α-HNPs and Azr@-HNPs were 27.8 ± 7.7 and 38.1 ± 9.3 nanometers, respectively, and their median sizes were 25.9 and 39.2 nanometers, respectively. The lowest and highest particle sizes of α-HNPs and Azr@-HNPs were 17.7 and 16.4 nanometers and 49 and 50.5 nanometers, respectively.

The experimental results of the adsorption study revealed that a pH of 10, 150 milligrams dose of α-HNPs, and 400 milligrams per liter concentration of Azr, and a temperature of 293 kelvin were the optimal conditions for the efficient adsorption of Azr on α-HNPs. Furthermore, the thermodynamic study revealed that the adsorption of Azr on α-HNPs was via a spontaneous endothermic chemisorption process and followed second-order kinetics.

Conclusion

In conclusion, the researchers of the present study aimed to use biosynthesized α-HNPs as a bioadsorbent of Azr found in contaminated pharmaceutical wastewater. The adsorption studies revealed that Langmuir was the suitable isothermal model with a correlation coefficient R² of 0.9992 and maximum adsorption capacity was 114.05 milligram of adsorbate per one gram of contaminant (mg/g).

The results revealed that the α-HNP-based nanobioadsorbent was a promising agent for removing the Azr from contaminated wastewater. Azr@α-HNPs served as versatile nanosystems with biomedical applications such as anticancer, antiviral, and antibacterial agents. The antibacterial studies showed a high synergistic impact of Azr@α-HNPs, especially against Gram-positive bacteria.

Additionally, Azr@α-HNPs showed anticancer effects on HepG2, MCF7, and HCT116 cell lines, and its IC₅₀ was comparatively less than α-HNPs alone against the same cell lines. The present work is the first study that revealed the use of Azr@α-HNPs as an antiviral agent against SARS-CoV-2.