The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology.

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Secondary Metabolites in the Green Synthesis of Metallic Nanoparticles

Quercetin (Que) and its derivatives are naturally occurring phytochemicals with promising bioactive effects. The antidiabetic, anti-inflammatory, antioxidant, antimicrobial, anti-Alzheimer's, antiarthritic, cardiovascular, and wound-healing effects of Que have been extensively investigated, as well as its anticancer activity against different cancer cell lines has been recently reported. Que and its derivatives are found predominantly in the Western diet, and people might benefit from their protective effect just by taking them via diets or as a food supplement. Bioavailability-related drug-delivery systems of Que have also been markedly exploited, and Que nanoparticles appear as a promising platform to enhance their bioavailability. The present review aims to provide a brief overview of the therapeutic effects, new insights, and upcoming perspectives of Que.

Therapeutic Potential of Quercetin: New Insights and Perspectives for Human Health.

A pH and NH3 sensing intelligent film based on Artemisia sphaerocephala Krasch. gum and red cabbage anthocyanins anchored by carboxymethyl cellulose sodium added as a host complex

An overview of functional nanoparticles as novel emerging antiviral therapeutic agents.

Infectious diseases can be transmitted and they cause a significant burden on public health globally. They are the greatest world killers and it is estimated that they are responsible for the demise of over 17 million people annually. The impact of these diseases is greater in the developing countries. People with compromised immune systems and children are the most affected. Infectious diseases may be caused by bacteria, viruses, and protozoa. The treatment of infectious diseases is hampered by simultaneous resistance to multiple drugs, indicating that there is a serious and pressing need to develop new therapeutics that can overcome drug resistance. This review will focus on the recent reports of metal-based nanoparticles that are potential therapeutics for the treatment of infectious diseases and their biological efficacy (in vitro and in vivo).

Metal-Based Nanoparticles for the Treatment of Infectious Diseases

Highly monodispersed gold nanoparticles synthesis and inhibition of herpes simplex virus infections.

Semi-interpenetrating hydrogels from carboxymethyl guar gum and gelatin for ciprofloxacin sustained release.

Edible nano-bio-composite film cargo device for food packaging applications

Visceral leishmaniasis (VL) is a chronic protozoan infection in humans associated with significant global morbidity and mortality. There is an urgent need to develop drugs and strategy that will improve therapeutic response for effective clinical treatment of drug resistant VL. To address this need, andrographolide (AG) nanoparticles were designed with P-gp efflux inhibitor vitamin E TPGS (D-α-tocopheryl polyethyleneglycol 1000 succinate) for sensitivity against drug resistant Leishmania strains. AG loaded PLGA (50∶50) nanoparticles (AGnps) stabilized by vitamin E TPGS were prepared for delivery into macrophage cells infested with sensitive and drug resistant amastigotes of Leishmania parasites. Physico-chemical characterization of AGnps by photon correlation spectroscopy exhibited an average particle size of 179.6 nm, polydispersity index of 0.245 and zeta potential of −37.6 mV. Atomic force microscopy and transmission electron microscopy visualization revealed spherical nanoparticles with smooth surfaces. AGnps displayed sustained AG release up to 288 hours as well as minimal particle aggregation and drug loss even after three months study period. Antileishmanial activity as revealed from selectivity index in wild-type strain was found to be significant for AGnp with TPGS in about one-tenth of the dosage of the free AG and one-third of the dosage of the AGnp without TPGS. Similar observations were also found in case of in vitro generated drug resistant and field isolated resistant strains of Leishmania. Cytotoxicity of AGnp with and without TPGS was significantly less than standard antileishmanial chemotherapeutics like amphotericin B, paromomycin or sodium stibogluconate. Macrophage uptake of AGnps was almost complete within one hour as evident from fluorescent microscopy studies. Thus, based on these observations, it can be concluded that the low-selectivity of AG in in vitro generated drug resistant and field isolated resistant strains was improved in case of AG nanomedicines designed with vitamin E TPGS.

In vitro susceptibilities of wild and drug resistant leishmania donovani amastigote stages to andrographolide nanoparticle: role of vitamin E derivative TPGS for nanoparticle efficacy.

Leishmaniasis is a WHO notified neglected tropical disease (NTD) caused by the Leishmania parasite species. The parasite locates rapidly in the macrophage cells and survives there for a long period of time with or without any symptomatic response. Eliminating Leishmania from the macrophage sites is complicated. Only a few antileishmanial drugs are known and most of them have developed resistance over the time. We have synthesized highly monodispersed gold nanoparticles (KAunp) in a rapid reduction reaction catalyzed in kaempferol. Kaempferol stabilized nanoparticles in 18.24 nm size domain were used as leishmanicidals in macrophage infested conditions. KAunps' CC50 in the macrophages was at 2.4 × 102 μM while that for sodium stibogluconate was 27 μM. Phagocytic uptake in infested cells was fast and remarkable. KAunps were explicitly effective against both the wild and drug resistant organisms. Monodispersed gold nanoparticles synthesized in green technology appeared as safer alternatives for leishmanial chemotherapy.

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Asim Halder

Papers

Highly monodispersed gold nanoparticles synthesis and inhibition of herpes simplex virus infections.

Semi-interpenetrating hydrogels from carboxymethyl guar gum and gelatin for ciprofloxacin sustained release.

Edible nano-bio-composite film cargo device for food packaging applications

In vitro susceptibilities of wild and drug resistant leishmania donovani amastigote stages to andrographolide nanoparticle: role of vitamin E derivative TPGS for nanoparticle efficacy.

Rapid synthesis for monodispersed gold nanoparticles in kaempferol and anti-leishmanial efficacy against wild and drug resistant strains