The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap, and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology.

Bionanotechnology is a branch of science that has revolutionized modern science and technology. Nanomaterials, especially noble metals, have attracted researchers due to their size and application in different branches of sciences that benefit humanity. Metal nanoparticles can be synthesized using green methods, which are good for the environment, economically viable, and facilitate synthesis. Due to their size and form, gold nanoparticles have become significant. Plant materials are of particular interest in the synthesis and manufacture of theranostic gold nanoparticles (NPs), which have been generated using various materials. On the other hand, chemically produced nanoparticles have several drawbacks in terms of cost, toxicity, and effectiveness. A plant-mediated integration of metallic nanoparticles has been developed in the field of nanotechnology to overcome the drawbacks of traditional synthesis, such as physical and synthetic strategies. Nanomaterials′ tunable features make them sophisticated tools in the biomedical platform, especially for developing new diagnostics and therapeutics for malignancy, neurodegenerative, and other chronic disorders. Therefore, this review outlines the theranostic approach, the different plant materials utilized in theranostic applications, and future directions based on current breakthroughs in these fields.

Zinc Oxide Nanoparticles (ZnONPs) are one of the most widely used metal oxide nanoparticles in biological applications because of their outstanding biocompatibility, affordability, and low toxicity. In biomedicine, ZnONPs have shown promise, particularly in the disciplines of anticancer and antibacterial fields. In comparison to other standard synthesis methods, the environmentally-friendly synthesis of metallic nanoparticles utilizing various plant extracts is a good option. The current research focuses on the synthesis of zinc oxide nanoparticles (ZnONPs) from R. sativus leaf extract under various physical conditions (Precipitation method). Analytical methods were used to confirm and characterize the produced ZnONPs. The spherical nature of the produced nanoparticles was established by SEM analysis. The generation of very pure ZnONPs was confirmed by EDS data. The crystalline nature of the produced nanoparticles, with a particle size of 66.47 nm, was confirmed by XRD. The XRD graphs’ presence of the (100), (002), and (101) planes strongly suggest the production of wurtzite ZnO. The visual and infrared area exhibits transmissions of 84 percent in the pH 10 nanoparticles. The band gap of the nanoparticles increases from 3.34 to 3.38 eV when the pH increases. These nanoparticles were effective against both Gram-positive and Gram-negative bacteria. The effect of several process parameters such as pH and temperature were investigated, and the best conditions were discovered to be pH 12 and 80 °C, respectively. The effect of ZnONPs was tested with human breast cancer cells (MCF-7), and they showed significant cytotoxic results. Collectively, our data suggest that ZnONPs of R. sativus leaf extract inhibit breast cancer cell lines. The ZnONPs are, therefore, a prospective source of chemopreventive drugs that merit additional exploration in order to uncover lead compounds with cancer chemotherapeutic potential.

Enzymes that degrade pectin are called pectinases. Pectinases of microbial origin are used in juice clarification as the process is cost-effective. This study screened a pectinase-producing bacterium isolated from soil and identified as Bacillus subtilis 15A B-92 based on the 16S rRNA molecular technique. The purified pectinase from the isolate showed 99.6 U/mg specific activity and 11.6-fold purity. The molecular weight of the purified bacterial pectinase was 14.41 ± 1 kD. Optimum pectinase activity was found at pH 4.5 and 50 °C, and the enzyme was 100% stable for 3.5 h in these conditions. No enzymatic inhibition or activation effect was seen with Fe²⁺, Ca²⁺, or Mg²⁺. However, a slight inhibition was seen with Cu²⁺, Mn²⁺, and Zn²⁺. Tween 20 and 80 slightly inhibited the pectinase, whereas iodoacetic acid (IAA), ethylenediaminetetraacetate (EDTA), urea, and sodium dodecyl sulfate (SDS) showed potent inhibition. The bacterial pectinase degraded citrus pectin (100%); however, it was inactive in the presence of galactose. With citrus pectin as the substrate, the Km and Vmax were calculated as 1.72 mg/mL and 1609 U/g, respectively. The high affinity of pectinase for its substrate makes the process cost-effective when utilized in food industries. The obtained pectinase was able to clarify orange and apple juices, justifying its application in the food industry.