Antibacterial and anticancer potentials of graphene-silicon nitride nanomaterials-enhanced polymer nanocomposites

Hybrid nanomaterials (HNMs) have become more interesting to researchers for various optoelectronic and biological applications. To that end, a duo of researchers from Iraq fabricated PEO–CMC–PANI ternary polymer nanocomposites filled with 0%, 1%, 3%, 5% GO–Si₃N₄ hybrid nanomaterials via sol–gel-ultrasonic synthesis. They used XRD, FTIR, FESEM, TEM and UV–vis spectroscopy to characterize structural, morphological and optical properties, while agar diffusion and MTT assays tested antibacterial and anti-A549 lung cancer activities.

“All samples showed semi-crystalline structures,” shares corresponding author Ehssan Al-Bermany. “FTIR confirmed strong hydrogen-bond interfacial interactions between polymers and nanofillers.”

Meanwhile, microscopic images proved uniform dispersion of GO and Si₃N₄ inside the matrix. “Intense UV absorption occurred at 200–280 nm from π–π* transitions,” says Al-Bermany. “Higher GO–Si₃N₄ loading raised light absorbance and narrowed optical band gaps, allowing indirect gap to drop from 3.55 eV to 3.10 eV, forbidden gap from 3.45 eV to 2.75 eV, because nanofillers generated mid-gap energy levels.”

The researchers found that antibacterial performance was concentration-dependent against E. coli (Gram-negative) and S. aureus (Gram-positive). “The 5% composite reached maximum inhibition zones of 26 mm and 14 mm respectively,” adds Al-Bermany. “Antibacterial mechanism included ROS overproduction, mechanical membrane rupture by sharp GO edges and anti-adhesion rough Si₃N₄ surfaces.”

Notably, MTT and AO–EtBr staining verified the 5% nanocomposite effectively induced A549 cancer cell apoptosis, while GO and Si₃N₄ synergistically triggered oxidative stress, mitochondrial dysfunction, DNA damage and cell cycle arrest, alongside photothermal effects under light irradiation to eliminate tumor cells.

PEO, CMC and PANI were then selected for good biocompatibility. “Most prior GO–Si₃N₄ composite research focused on mechanical stability, lacking biomedical exploration,” says co-author Rawaa A. Abdul-Nabi. “In our case, polymers were dissolved separately, mixed stepwise, then blended with dispersed GO–Si₃N₄ suspensions with long stirring and periodic sonication for homogeneity.”

Standard spectroscopic, microscopic and biological evaluation methods were adopted with triple parallel tests.

“GO–Si₃N₄ fillers greatly improved optical absorption, bactericidal and anticancer capacity of the ternary polymer blend,” adds  Abdul-Nabi. “The 5% loading sample exhibited optimal comprehensive performance.”

The researchers believe such nanocomposites with adjustable optical and biological functions have wide prospects in biosensors, medical antibacterial coatings and photodynamic therapy devices.

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Contact the author:

Ehssan Al-Bermany. Physics Department, Education College for Pure Sciences, University of Babylon, Hilla, Iraq. ehssan@uobabylon.edu.iq

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