Preparation Of Gelatin/CMC Complex Condensed Nuclear Polyhedrosis Virus Microcapsule And Performance Studies

Microencapsulation technology is a process that uses natural or large molecular weight polymers as wall materials to encapsulate solid,liquid,or gaseous materials capsule cores to form semi-permeable or well-sealed spheres.It can protect susceptible core materials from the external environment.Biological pesticides,particularly baculoviruses,change their behavior by sensory stimuli such as temperature,external light,and gravity.Hence,using microencapsulation of baculovirus may extend its biological activity and ensure efficiency.In this paper,Spodoptera litura nuclear polyhedrosis virus has been used as the core material,while gelatin and sodium carboxymethyl cellulose(CMC)are used as wall,and tea polyphenols are used as the curing agent.A gelatin/CMC-Spodoptera litura nuclear polyhedrosis virus microcapsule was prepared using a complex coacervation process.Single-factor experiments were carried out to optimize the preparation conditions and to examine the morphological characteristics,apparent morphology,embedding rate,drug loading,particle size,indoor virulence,and UV resistance of microcapsule virus.The optimal conditions used for the preparation of gelatin/CMC-Spodoptera litura and polyhedrosis virus microcapsules are as follows:the gelatin/CMC ratio was used as 9:1,the wall material concentration was applied as 1%,the core-to-wall solid mass ratio was used as 1:2,pH value of the material was 4.67 and finally the curing time was kept as 1h.The microcapsule,which was prepared under the above conditions,has high sphericity,an average particle size of 13μm with an embedding rate of 62.53%,and a drug load of43.87%.Microencapsulated virus laboratory virulence assays showed a 10%loss of activity compared to untreated virus activity.The microencapsulated virus was then exposed to temperature,ultraviolet radiation,and field exposure treatment,The bioassay data were analyzed using Graphpad-Prism software.The results showed that microencapsulation did not have a significant effect on increasing temperature in water/power tolerance,but increased resistance to ultraviolet radiation.Especially for water agents,the low-intensity UV-resistant period(350μw/cm~2)was extended from 474 min to 570.4 min,while the inactivation intensity increased from1557μw/cm~2 to 2841μw/cm~2 at 30 min.Ultraviolet radiation did not significantly influence on the entire period of infection of the host Spodoptera litura nuclear polyhedrosis virus(2-5 d).However,microencapsulation preserved the effect of virus on the later period of infection(7-9 d),and half of the lethal days,i.e.,1-2 d earlier.In the presence of exposure,the survival ability of the microencapsulated virus was significantly higher than that of the unencapsulated virus.Specific primers were designed for Spodoptera litura nuclear polyhedrosis virus based on the Polyhedrin sequence.A standard curve,y=-3.399x+36.089,was generated by a quantitative real-time PCR method,while a rapid detection method for Spodoptera litura nuclear polyhedrosis virus was established.Hence,the virus content of the midgut,hemolymph,and whole worms of the infected larvae was dynamically monitored by this process.The microencapsulated virus was found to have a lower initial rate of proliferation in the midgut and hemolymph tissues than the unembedded virus.However,the virus reached the expected level after 30 and 60 hours of infection.The midgut tissue was stable within 10~5-10~5.5.5 copies per mg in the presence of polyhedron gene.Nevertheless,the hemolymph tissue fluctuated in the presence of virus per microliter within the range of10~4-10~5 copies.The whole worm virus content was linear over time,and the regression equation represented as y=1.392+3.231x(R=0.957).The results show that the microcapsule wall material does not affect the replication and proliferation of the virus in the insect body after the virus is completely released,and the insecticidal effect is only related to the virus activity.