Larvicidal and pupicidal evaluation of silver nanoparticles synthesized using Aquilaria sinensis and Pogostemon cablin essential oils against dengue and zika viruses vector Aedes albopictus mosquito and its histopathological analysis

Figures & data

Table 1. Larval and pupal toxicity of essential oil aquilaria sinensis (AsEO) and pogostemon cablin (PcEO) against zika vector ae. Albopictus.

			95% confidence limit LC50 (LC90)
Treatment	Stage	LC50 (LC90)	LCL	UCL	Regression equation	X^2 (df =4)
	I	44.23 (397)	33.68 (220)	54.89 (1448)	Y= −2.83 + 1.71x	12.33
	II	54.94 (559)	43.18 (275)	70.95 (2884)	Y= −2.46 + 1.43x	11.96
AsEO	III	89.66 (652)	71.91 (329)	129.97 (2812)	Y= −3.23 + 1.71x	18.89
	IV	118.7 (809)	91.09 (385)	196.68 (4086)	Y= −3.43 + 1.71x	20.87
	Pupa	166 (2258)	108.5 (650)	513.82 (8666)	Y= −2.86 + 1.42x	12.70
	I	32.49 (287)	22.14 (172)	40.95 (863.9)	Y= −2.63 + 1.71x	11.02
	II	47.88 (591)	35.56 (275)	61.78 (3967)	Y= −2.46 + 1.43x	10.08
PcEO	III	60.03 (517)	48.45 (269)	77.34 (2165)	Y= −3.03 + 1.71x	14.61
	IV	90.05 (602)	72.79 (314)	128.33 (2351)	Y= −3.80 + 2.00x	19.16
	Pupa	n.m.	n.m.	n.m.

LC₅₀: Lethal concentration that kills 50% of insects; LC₉₀: Lethal concentration that kills 90% of insects; LCL: lower confidence limit; UCL: upper confidence limit; χ²: Chi-square value; df: degrees of freedom; n.m.: No mortality.

Significant at p<.05 level.

Table 2. Larval and pupal toxicity of aquilaria sinensis and pogostemon cablin essential oil synthesized silver nanoparticles (AsEO-AgNPs and PcEO-AgNPs) against zika vector ae. Albopictus.

			95% confidence limit LC50 (LC90)
Treatment	stage	LC50 (LC90)	LCL	UCL	Regression equation	X^2 (df = 4)
	I	0.81 (1.72)	0.61 (1.50)	0.97 (2.10)	Y = 0.0 + 5.0x	19.71
	II	0.83 (2.33)	0.56 (1.95)	1.02 (3.14)	Y = 0.2 + 2.8x	19.74
AsEO-AgNPs	III	1.02 (2.49)	0.81 (2.17)	1.19 (3.02)	Y = 0.1 + 3.6x	25.03
	IV	1.12 (4.36)	0.81 (4.36)	1.37 (6.48)	Y= −0.2 + 2.0x	28.46
	Pupa	0.90 (2.07)	0.68 (1.79)	1.06 (2.59)	Y = 0.1 + 4.0x	20.99
	I	0.85 (1.79)	0.65 (1.56)	1.00 (2.18)	Y = 0.2 + 5.0x	21.14
	II	0.91 (2.26)	0.68 (1.92)	1.08 (2.91)	Y = 0.2 + 4.0x	22.56
PcEO-AgNPs	III	1.04 (2.85)	0.79 (2.36)	1.23 (3.93)	Y = 0.1 + 4.0x	28.23
	IV	1.19 (3.43)	0.95 (2.89)	1.39 (4.42)	Y= −0.2 + 2.6x	32.09
	Pupa	0.84 (2.15)	0.59 (1.82)	1.02 (2.78)	Y = 0.1 + 4.0x	19.30

LC₅₀: Lethal concentration that kills 50% of insects; LC₉₀: Lethal concentration that kills 90% of insects; LCL: lower confidence limit; UCL: upper confidence limit; χ²: Chi-square value; df: degrees of freedom.

Significant at p < .05 level.

Figure 1. Preparation process of AgNPs, and UV-vis spectrum. (A) Reactants before and after the reaction. (B) UV–Vis adsorption spectrum of AgNPs. The maximum absorption peaks of AsEO-AgNP and PcEO-AgNP were 408 and 430 nm, respectively, after 90 min from the reaction.

Figure 2. (A) SEM image of synthesized AgNPs using Aquilaria sinensis essential oil (AsEO). (B) SEM image of synthesized AgNPs using Pogostemon cablin essential oil (PcEO). (C) EDX pattern of synthesized AsEO-AgNPs and (D) EDX pattern of synthesized PcEO-AgNPs.

Figure 3. (A) TEM image of synthesized AgNPs using Aquilaria sinensis essential oil (AsEO) (B) TEM image of synthesized AgNPs using Pogostemon cablin essential oil (PcEO). (C) XRD pattern of synthesized silver nanoparticles by AsEO and (D) XRD pattern of synthesized silver nanoparticles by PcEO.

Figure 4. Fourier transform infrared (FT-IR) spectrum of freeze-dried powder of silver nanoparticles synthesized using Aquilaria sinensis essential oil (AsEO) and Pogostemon cablin essential oil (PcEO).

Figure 5. Larvicidal and pupicidal efficacy of (A) Aquilaria sinensis essential oil (AsEO), Pogostemon cablin essential oil (PcEO) and (B) green-synthesized silver nanoparticles using AsEO and PcEO against I-IV instar larvae and pupae of dengue and zika vector Aedes albopictus. Mortality was recorded after 24 h of exposure. No mortality was observed in the control. Different letters above each bar indicate significant differences among treatments (ANOVA, Tukey’s HSD test, p < .05).

Figure 6. Longitudinal sections of the midgut of an Aedes albopictus 4th instar larvae, magnification: 40×. (A, B) control, (C) a larva under treatment with Aquilaria sinensis essential oil, (D) a larva under treatment with Pogostemon cablin essential oil, (E) a larva under treatment with AsEO-AgNPs, (F) a larva under treatment with PcEO-AgNPs. EP: Epithelial cells; BM: basement membrane; M: muscles; N: nucleus; LU: gut lumen.