In Vitro Assessment of Apoptotic and Cell Cycle Arrest Analysis on HepG2 Cells by Polyethylene Glycol–Coupled Selenium Nanocomposite Fabricated From <i>Cassia fistula</i> Flowers

Polymer-encapsulated nanocomposite has been proven to have ameliorative effects in the treatment of cancer. The focused objective of the present research is to fabricate polyethylene glycol (PEG)-based <i>Cassia fistula</i> flower selenium nanocomposite (CFF-SeNC). The fabricated CFF-SeNC was characterised using a UV-visible spectrophotometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM)-energy dispersive x-ray (EDX), and x-ray diffractometer (XRD) analysis. The highest UV-visible absorption spectra were at 355 nm. The oval-shaped, less agglomerated nanocomposite with a rough surface was seen in the SEM results with the elemental composition of carbon, oxygen, and selenium. The XRD analysis results showed the crystalline form of CFF-SeNC. The potency of CFF-SeNC against pathogenic bacteria and fungi proved that CFF-SeNC is effective against the tested fungi <i>Candida albicans</i>. The antioxidative assays-DPPH, ABTS, and H₂O₂ of CFF-SeNC-revealed the inhibition percent of 85.51% ± 0.79%, 90.53% ± 0.90%, and 84.87% ± 0.80% at maximum concentration (50 <i>μ</i>g/mL), respectively. The anti-inflammatory efficiency of CFF-SeNC was found to be 80.61% ± 0.87% and 87.78% ± 0.88% by egg albumin denaturation and HRBCs (human red blood cells) membrane stabilisation assay. The biocompatible nature of CFF-SeNC was tested by brine shrimp lethality activity, which proved that at 48 h, the minimal dose was not toxic; however, mild toxicity was shown at a higher dosage. The anticancer studies of CFF-SeNC in HepG2 cells were active in inhibiting 50% of cells (IC₅₀ value) at 27.30 <i>μ</i>g/mL. HepG2 cells depicted predominant morphological changes upon treatment with CFF-SeNC, whereas there was no alteration in <i>Vero</i> cells. The elaborative study on determining the phases of cell apoptosis was further analysed by fluorescence microscopy, cell cycle arrest, and Annexin V/propidium iodide staining through flow cytometric analysis. The outcome of current research has corroborated the enhanced therapeutical efficiency of PEG-encapsulated selenium nanocomposite with emphasis on the apoptotic effect in hepatocellular carcinoma (HepG2 cells).