Biological Effects Of Silver Nanoparticles On Silkworm Bombyx Mori

Silver nanoparticles are widely used in various fields due to their excellent antibacterial,electrical and thermal conductivity.These applications greatly increase the possibility of silver nanoparticles contacting with people in natural environment.The safety of silver nanoparticles has become the focus of attention.Some metal nanoparticles that are relatively inert under natural conditions show a sharp increase in toxicity as the particle size decreases.Therefore,it is very important to study the biological effects of silver nanoparticles with different sizes.In the research of nano-materials,the research objects are mostly cells and model organism mice.Silkworm,as a new model organism,has the advantages of short generations,many offspring,no moral controversy and high similarity between genes and human genes,which has become a research hotspot.Therefore,the biological effects of silver nanoparticles with different sizes were studied in this experiment using silkworm as a model organism.1.Silver nanoparticles were prepared by using sodium citrate and tannic acid as reducing agents to reduce the precursor Ag NO₃.The results of ultraviolet spectrum and transmission electron microscope show that the synthesized Ag NPS has a size of23.2±2.8 nm,34.6±4.6 and 47.6±5.2?sign as 23 nm,35 nm and 47 nm respectively?,and has good dispersibility and low particle size dispersion,which can be used for subsequent research.2.Ag NPs was introduced into silkworm body by gastropod injection,and the death numbers of different groups of silkworm were counted.Bliss method was used to calculate the LD50 of 23 nm,35 nm and 47 nm Ag NPs to the 3 day of 5th instar silkworm larvae were 170.71,248.67and 303.06?unit?g per silkworm?,respectively,thus it can be seen that 23 nm Ag NPs has greater acute toxicity to silkworm.The weight and cocoon weight of the high concentration group Ag NPs?180?g per silkworm?silkworm are lower than those of the control group,high concentration will inhibit the growth of silkworm.3.Inductively coupled plasma mass spectrometry?ICP-MS?was used to measure the changes of silver content in the midgut,blood,silk gland,silkworm feces and silk of silkworm within 72 hours.The results showed that Ag NPs was injected directly into blood,resulting in a very high concentration of Ag in the blood after 24 hours of injection.Ag transported into the blood will be transported into the midgut,and Ag transported into the midgut will participate in metabolism and be discharged out of the body with silkworm feces.Ag concentration in silk gland remained basically unchanged from 24 h to 72 h.Small-sized Ag NPs are more easily absorbed and enriched in vivo,while large-sized Ag NPs are more easily metabolized into silkworm feces.Ag NPs is metabolized into silk in silk gland,and 23 nm Ag NPs is more distributed in sericin.The total protein,malondialdehyde?MDA?,superoxide dismutase?SOD?and catalase?CAT?of the midgut were determined.The results showed that the oxidation damage of small-sized Ag NPs to the midgut tissue of silkworm was more serious,and the greater the concentration of the same size,the more serious the damage.4.The secondary structure of degummed silk was qualitatively and quantitatively analyzed by synchrotron radiation micro-infrared spectrometer.The results show that Ag NPs can increase the content of?-sheet in the secondary structure of silk,and the increase is larger for small size.5.The mechanical properties of degummed silk were tested by using a single fiber strength tester.The results showed that the Ag NPs pair would reduce the maximum breaking strength and elongation at break of degummed silk,at the same time its Young's modulus also decreased to different degrees,which indicated that Ag NPs would cause the mechanical properties of silkworm silk fiber to decline.To sum up,the small-sized Ag NPs has greater acute toxicity to the silkworm,more obvious inhibition on the life activities of the silkworm,and greater influence on the structure and performance of silk.In this experiment,silkworm was used as a model organism,and the biological effects of Ag NPs on silkworm were preliminarily studied,which provided a certain basis for toxicological study of Ag NPs.