Synthesis And Functionalization Of Metal Nanoparticles With Phvtochemicals And Their Bioactivities Against Bacteria And Leishmania

Leishmaniasis, a category -1 disease (emerging and uncontrollable), has not attracted the appropriate consideration it needs and therefore, has developed into serious health troubles worldwide. Unfortunately, the available leishmanicidal drugs are limited and coupled with serious side effects and additionally the leishmania parasites have shown an inevitable resistance toward most of these drugs. All these factors pose a barrier to control the parasite.Secondly, several pathogenic bacteria have shown significant degree of resistance to several antibiotics. Hence, new strategies are required to prepare more efficient and safe (less toxic)agents that could eradicate the emerging microbial resistance and control the spread of Leishmania parasite and pathogenic bacteria. One of the effective strategies is to develop nano-metals and functionalized them with biologically active molecules. Such a hybrid nanomaterials have exhibited promising activities against a wide range of microorganisms. In our research study, we prepared nanoscale particles of metals (silver and gold) using bioactive molecules from a variety of medicinal plants. These bioactive molecules perform dual functions (i) reducing metal ions and (ii) capping them for long term stability. Particles of gold (AuNPs) and silver (AgNPs) prepared in all the projects were successfully characterized by different techniques like UV-Vis spectroscopy, FTIR, TEM, XRD and dynamic light scattering (DLS).Project-1. In this project, particles of gold and silver were prepared with bio-chemicals present in the water extract of Sargentodoxa cuneata (medicinal plant). Various experimental conditions (pH, temperature, salt amount and extract concentration) were optimized in order to obtain the desired product. These nanoparticles (AgNPs and AuNPs) were applied as leishmanicidal and bactericidal agents. We disclosed that both the bio-prepared nanoparticles were the efficient material in inhibiting the growth of parasites (leishmania) and different bacteria used. The calculated IC50 values of Ag and AuNPs against leishmania were found to be 4.40 and 5.30 ?g/mL respectively. In addition, these nonmaterial's displayed considerable efficacy against antibiotic resistant (streptomycin sulfate) Gram +ve and Gram -ve bacteria.Project-?. Project ? comprise on the biogenic preparation of AgNPs by using active constituents (phytochemicals) in the water extract of Isatis tinctoria (Chinese medicinal plant). The bio-synthesized AgNPs were functionalized with amphotericin B (antileishmanial drug) and both the prepared nanoparticles were applied as antileishmanial agents. Our findings disclosed that these nanoparticles have enhanced efficacy against the tested leishmania when irradiated with light (visible light). The irradiated AgNPs (88 % growth inhibition) and AmB-AgNPs (96% growth inhibition) showed improved efficacy than non-irradiated samples (73% inhibition). We concluded that greater amount of silver is released from AgNPs when irradiated with light, which in turn produce a high level of reactive oxygen species. Reactive oxygen species destroy intracellular parasites by different mechanisms.Project-?. In this project, we prepared AgNPs of different surfaces. First, negatively charged biogenic AgNPs were synthesized, which were then modified with chitosan biopolymer (positive charge). The biological efficacy of positive and negatively charged AgNPs was evaluated against bacteria. We observed that surface chemistry of the nanoparticles plays a vital role in their biological activity. The AgNPs which were modified with chitosan (positive charge) had improved activity than negatively charged AgNPs. We suggested that positive AgNPs can make a better electrostatic contact with the negative cell wall of bacteria, and therefore, exerts an improved antibacterial action as compared with negative AgNPs. It was further concluded that positive AgNPs have more drastic effect in rupturing bacterial cell wall than negative AgNPs. In addition, positive AgNPs generated higher amount of intracellular reactive oxygen species than negative charge AgNPs. All these experimental observation led us conclude that nanoparticles and bacterial interface chemistry is critical for enhanced antibacterial activity.Project-IV. Herein,we report on the catalytic performance of biosynthesized AuNPs in a size dependent assay. The effect of experimental variables such as extract (plant extract)amount and salt precursor were also optimized in order to bio-fabricate AuNPs of different sizes. Our data showed that particle size affect the catalytic behavior of AuNPs. Particles(AuNPs) of small sizes displayed better activity in reducing methylene blue (a hazardous dye) and 4-nitrophenol (hazardous chemical) into a useful product 4-aminophenol. Almost 80% of methylene blue was reduced in 80 min under the specified experimental conditions(pH 8, visible light at 30 ?) using particles of 20 nm sizes. Furthermore, kinetic study revealed that catalytic rate constant for the conversion of nitrophenol to aminophenol was higher for AuNPs of small sizes as compared with their large counterparts. The experimental findings conclude that surface area of the nanomaterials plays a vital role in their catalytic performance.