Comparative assessment of green and chemically synthesized glutathione capped silver nanoparticles for antioxidant, mosquito larvicidal and eco-toxicological activities.

A comparative assessment of AgNPs synthesized through three different routes viz. clove bud extract mediated AgNPs, sodium borohydride AgNPs and Glutathione (GSH) capped AgNPs for antioxidant and mosquito larvicidal activities was the major focus of the present study. The nanoparticles were characterized using UV-VIS spectrophotometry, dynamic light scattering (DLS), X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Characterization studies revealed the synthesis of stable, crystalline AgNPs measuring 28 nm, 7 nm and 36 nm for green, chemical and GSH-capped AgNPs respectively. FTIR analysis exhibited the surface functional moieties that were responsible for reduction, capping and stabilizing AgNPs. Antioxidant activity was found to be 74.11%, 46.62% and 58.78% for clove, borohydride and GSH-capped AgNPs respectively. Mosquito larvicidal bioactivity of AgNPs against Aedes aegypti IIIrd instar larvae depicted clove AgNPs being most effective (LC50-4.9 ppm, LC90-30.2 ppm) followed by GSH-capped (LC50-20.13 ppm, LC90-46.63 ppm) and borohydride AgNPs (LC50-13.43 ppm, LC90-160.19 ppm) after 24 h. Toxicity screening against aquatic model Daphnia magna revealed Clove mediated and GSH-capped AgNPs to be safer as compared to the borohydride AgNPs. It may be envisaged that green and capped AgNPs may be further explored for diverse biomedical and therapeutic applications.

Preparation of Thymus vulgaris (L.) essential oil nanoemulsion and its chitosan encapsulation for controlling mosquito vectors.

Here, we report a novel comparative assessment of preparation and characterization of thyme oil nanoemulsion and its chitosan encapsulation using high energy approach for the management of three major mosquito species viz., Anopheles stephensi (Liston,1901), Aedes aegypti (Linn., 1762) and Culex tritaeniorhynchus (Giles, 1901). The synthesized formulations were analysed for thermodynamic stability, indicating 1:0.5 (oil: surfactant) ratio to be the most stable of thyme oil nanoemulsion while 1:1 (nanoemulsion: chitosan solution) ratio of its chitosan encapsulation. These were further characterized by dynamic light scattering and transmission electron microscopy which revealed the size and morphology of the droplets which measured 52.18 ± 4.53 nm for thyme oil nanoemulsion and 50.18 ± 2.32 nm for its chitosan encapsulation. All the droplets were well dispersed with distinct flower-shaped nanoemulsion and somewhat mitochondria like chitosan encapsulation. In-vitro release study of thyme essential oil from its nanoemulsion and chitosan encapsulation showed that 91.68% and 73.41% of the total oil concentration in water was released respectively to the environment after 48 h clearly depicting controlled release in the encapsulation. Assessment of insecticidal potential against selected mosquito species revealed that both the nanoemulsion and its chitosan encapsulation were effective on the major mosquito species. Maximum activity of thyme oil nanoemulsion was noticed against C. tritaeniorhynchus (LC50-22.58 ppm) after 24 h of exposure while it was observed that its chitosan encapsulation was most effective on A. stephensi (LC50-18.88 ppm) after 24 h of exposure. Consistent morphological alterations could be noticed in the larvae of mosquito species. Hence, these nanoemulsions and encapsulations could be further tested for their applications against other insect pests in agriculture.

Genetic differentiation of invasive Aedes albopictus by RAPD-PCR: implications for effective vector control.

Aedes albopictus is an invasive mosquito species of great concern to public health as it is responsible for the biological transmission of several pathogens causing dengue, chikungunya, yellow fever, etc. In 2009, this mosquito was detected for the first time in Agra City. This study represents the first genetic analysis of A. albopictus from India. Random amplified polymorphic DNA (RAPD) was used to study the genetic structure of A. albopictus in four populations from different larval habitats. Seven RAPD primers produced 141 loci. The results displayed rich genetic variation among larval populations which is evident from high value of genetic differentiation (G ST), i.e. 0.280, indicating a very great genetic differentiation. Effective migration rates were observed to be 1.28, depicting a limited gene flow. According to analysis of molecular variance (AMOVA), the genetic distance between populations was significant (P < 0.05), showing a very high intrapopulation variation (96%) with only 4% variation among populations. Average genetic distances between populations were also calculated using PopGene software. Nei's average genetic distance between these populations was 0.112 (0.05-0.18). The cluster analysis technique of unweighted pair-group mean analysis (UPGMA) method of arithmetic averages was used to develop the phylogenetic tree which clearly shows two clusters of different larval habitats. The findings highlight high genetic differentiation indicating a slight migration rate confirming the recent introduction of this species in Agra region.

Haematological profile in Rattus norvegicus during experimental cysticercosis.

The present study pertains to the haematological examination of the rats experimentally infected with cysticercosis which revealed significant alterations in several parameters. Haemoglobin concentration was observed to be significantly lower in later stages of cysticercosis with respect to the control rats whereby 36% decline was observed at 60 days post infection (pi). These changes in haemoglobin were more or less parallel to those recorded for RBC counts with 18% reduction at 60 days pi. A significant rise was noticed in the erythrocyte sedimentation rates throughout the course of infection with a maximum increase (42%) at 60 days pi whereas a decline in packed cell volume as the cyst development was also evident. Leucocytosis was observed at 10, 30 and 60 days post infection with 2.6, 2.5 and 1.5 fold increase, respectively. Moreover, haematological indices were prominently altered by cysticercosis indicating macrocytic hypochromia in advance stages of the cyst development.

Biochemical evidence of efficacy of potash alum for the control of dengue vector Aedes aegypti (Linnaeus).

Aedes aegypti is the primary vector of dengue, yellow fever and chikungunya in India and other South East Asian countries, and novel insecticides for vector control are urgently needed. In the present investigation, efficacy of potash alum, a traditionally known double salt in Indian and Chinese medicine system, was tested against the larvae of dengue vector, A. aegypti. LC(50,) LC(90) and LC(99) values were recorded for various instar larvae where I instar larvae were found to be the most susceptible and IV instar larvae as the least susceptible one. The LC(50) values of crude and standard potash alum of various instar larvae ranged between 15.29 and 48.53 ppm and 20.50-65.10 ppm, respectively. Biochemical changes were also evidenced in IV instar A. aegypti larvae following a sublethal exposure for 24 h in the levels of various nutrient reserves and primary metabolites such as sugar, glycogen, lipids and proteins suggesting possible mode of action responsible for larval mortality. Sugar and glycogen concentrations were measured as 24.6 and 10.67 µg per five larvae in controls which were significantly (p<0.05) reduced by 32.11-93.98% and 39.26-94.47%, respectively, in larvae treated with crude alum. In controls, protein and lipid content were recorded as 210.74 and 94.71 µg per five larvae which dropped up to 26.53% and 25.5%, respectively, in larvae following treatment with crude alum. Moreover, drastic changes were also recorded for DNA content with 25.39-44.17% decrease in crude alum-treated larvae. It is evident from these results that potash alum, a fairly cheaper and readily available ecofriendly compound could be recommended as a potential chemical larvicide against dengue vector at mosquito breeding sites in the vicinity of human dwellings.

Mosquito larvicidal potential of potash alum against malaria vector Anopheles stephensi (Liston).

Mosquito larviciding may prove to be an effective tool for incorporating into integrated vector management strategies for reducing malaria transmission. Here, we report the potential of potash alum, a traditionally known salt in Indian Ayurveda and Chinese medicine system, in malaria vector control by evaluating its aqueous suspension as larvicide and growth disruptor of Anopheles stephensi, under laboratory conditions. Immature stages of the mosquito were tested using WHO guidelines. 50 and 90% lethal concentrations among various larvae ranged between 2.1 to 48.74 ppm and 15.78 to 93.11 ppm, respectively. The results indicated that larvicidal effects of potash alum were comparable to various biological and chemical insecticides. The study provides considerable scope in exploiting local indigenous resources for the control of nuisance mosquito vectors.