BACKGROUND AND OBJECTIVES: Spodoptera litura nuclear polyhedrosis virus is a potent biological control agent against the tobacco cutworm, Spodoptera litura. However, its field efficacy is severely limited by rapid inactivation due to solar ultraviolet radiation and environmental instability. The study objectives were to synthesize a novel nano-biopesticide formulation by encapsulating Spodoptera litura nuclear polyhedrosis virus within a chitosan matrix and to evaluate its physicochemical properties and protective efficacy against critical environmental stressors.METHODS: Spodoptera litura nuclear polyhedrosis virus-loaded nanoparticles were synthesized via the ionic gelation method using chitosan and sodium tripolyphosphate. The physicochemical characteristics were elucidated using scanning electron microscopy, transmission electron microscopy, and zeta potential measurements. Encapsulation efficiency was quantified via the standard Bradford protein assay. The formulation’s stability and residual infectivity were assessed through bioassays against third-instar Spodoptera litura larvae following exposure to ultraviolet-A with 365 nanometers and ultraviolet-B with 312 nanometers irradiation (1–4 hours), varying potential of hydrogen conditions: 3–6, and thermal stress: 4, 25, and 40 degrees Celsius.FINDINGS: Transmission electron microscopy analysis revealed the formation of discrete, spherical primary nanoparticles with an ultra-small average diameter of approximately 48 nanometers, although scanning electron microscopy indicated a tendency for agglomeration in the freeze-dried state. The formulation exhibited a moderate encapsulation efficiency of 50.25 percent and a zeta potential of -29.6 millivolt, indicating sufficient colloidal stability. Crucially, bioassays demonstrated that the chitosan encapsulation significantly preserved viral infectivity under harsh conditions; the virus remained active after 4 hours of continuous ultraviolet irradiation and survived incubation in acidic environments with a potential of hydrogen: 3–6, conditions that typically inactivate unprotected or naked baculoviruses.CONCLUSION: The synthesized chitosan nanoparticles successfully encapsulate Spodoptera litura nuclear polyhedrosis virus and provide a robust physical shield against ultraviolet radiation and extreme potential of hydrogen. The achievement of a sub-100-nanometer particle size offers potential advantages for cellular uptake and tissue penetration. This formulation represents a promising, environmentally stable delivery system for viral biopesticides, warranting further optimization and open-field trials.
Haryadi et al. (Thu,) studied this question.