Owing to their multiple mechanisms of bactericidal activity, inorganic metal oxides and hybrid metal oxide nanocomposites may serve as a new class of effective disinfectants. Among metal oxide nanoparticles, iron oxide nanoparticles exhibit minimal or no cytotoxicity to human cells with very efficient bactericidal properties over a wide spectrum of bacteria. This paper presents the very first report on antibacterial properties of novel nanocomposites of iron oxide and cobalt oxide nanoparticles against pathogenic bacterial strains B. subtilis, S. aureus, E.coli and S. typhi. The enhanced bactericidal activity of the Fe/Co oxide nanocomposite was the result of synergistic effect of iron oxide and cobalt oxide nanoparticles. The nanocomposites were synthesized using co-precipitation route with increasing cobalt content in the sample and further characterized using XRD, TEM, Raman and VSM to investigate structural, optical and magnetic properties of the prepared nanocomposites, respectively. Also, the prepared nanocomposites were highly biocompatible and found non-toxic to human cell line MCF7.

In the present study, we demonstrate a rapid, in situ reduction of metal (Ag⁺ and Au³⁺) ions and subsequent carbonization of Citrus limon (lemon) extract to synthesize highly luminescent carbon-dots (C-dots) and their metal nanohybrids (MCNs) using one-pot microwave (MW) assisted technique within 6 min. In principle, L-ascorbic acid, citric acid and flavonoids reduce metal ions into corresponding metal nanoparticles followed by carbonization of carbohydrates in the lemon extract along with externally added ethylenediamine (EDA) to form EDA-functionalized C-dots based nanohybrids. The synthesized pristine C-dots, Ag/C-dot and Au/C-dot nanohybrids (<5 nm) colloidal solution exhibited bright photoluminescence (PL) at ∼515 nm with significant quantum yield (QY) of 48.3%, 46.2%, 62.2% and PL emission lifetime of 3.6 ns, 9.4 ns and 9.0 ns respectively. The reduced PL intensity and QY for Ag/C-dot nanohybrids could be due to fluorescence resonance energy transfer (FRET) while enhanced PL intensity and QY for Au/C-dot nanohybrids could be attributed to surface plasmonic resonance (SPR), when compared to pristine C-dots. These C-dots-based nanohybrids exhibited no signs of cytotoxicity in colon cancer cell lines (SW-480) and were easily internalized for fluorescence bioimaging. Thus, the MW-assisted sustainable synthesis of pristine C-dots and metal/C-dot nanohybrids derived from natural lemon extract can be exhibited as eco-friendly intense potential nano-bioprobes for cancer cellular imaging applications.

Hepatocellular carcinoma (HCC) is the most common liver cancer and is known to be resistant to conventional chemotherapy. The use of herbal medicine and supplements has increased over recent decades following side effects and resistant to conventional chemotherapy. The seeds of Bixa orellana L. commonly known as annatto have recently gained scientific attention due to presence of a carotenoid bixin for its substantial anticancer properties. However, molecular mechanisms underlying bixin-induced apoptosis are still unclear. Treatment of bixin significantly decreased the number of Hep3B cells and morphological study revealed the change in cellular and nuclear morphology that trigger the events of apoptosis confirmed by annexin V/PI staining. Further DCFDA and rhodamine 123 spectrofluorimetry study showed elevation in reactive oxygen species (ROS) production and loss of mitochondrial membrane potential (MMP), respectively. ROS production caused DNA damage and apoptosis was marked by cell cycle arrest, up-regulation of Bax and FasL protein as well as cleavage of caspase-9, caspase-8 and caspase-3 protein. Docking study with pro-apoptotic molecule Bax and surface Fas ligand exhibited energetically favourable binding interaction. Collectively, these results suggest that bixin capable of modulating the extrinsic and intrinsic molecules of apoptosis indicating its potential for development of promising candidate for hepatocellular carcinoma.