Safety and Toxicological Evaluation of Subunit Keyhole Limpet Hemocyanin-Loaded Lipid–PLGA Hybrid Nanoparticles (sKLH-hNPs) as a Nanocarrier for an Opioid Use Disorder Vaccine

A nanoparticle-based immunization strategy offers a promising treatment for opioid use disorder (OUD). This study tested the <i>in vivo</i> safety of subunit keyhole limpet hemocyanin-loaded lipid-PLGA hybrid nanoparticles (sKLH-hNPs) as a nanocarrier for OUD vaccine in adult male BALB/c mice by subcutaneous administration at an effective low dose (60 μg) and a dose 5-fold higher (300 μg), with cohorts of animals (n = 10/group, including controls) observed and evaluated for behavioral changes. At 3, 14, 28, and 56 days after dosing, mice (n = 3/dose) were sacrificed, and serum was collected for evaluation of electrolytes, minerals, proteins, liver function, renal function, and energy metabolism. Histological examination included all critical organs, gastrocnemius muscle, and skin from the site of injection. For behavioral evaluation, home cage, open field, and reflex observations were compared among the groups. Results demonstrated no statistical differences among the groups, with the exception of respirations observed in the home cage (O-RESP) on Day 3 (<i>P</i> = 0.03). There was no evidence of any effect of the test product on energy (glucose, cholesterol, triglycerides) or mineral metabolism (phosphorus, calcium) and hepatic function (urea nitrogen, albumin, total bilirubin), and no indication that the test agent caused liver injury, cholestasis, muscle damage, or acid-base imbalance. Histological analysis in control and treated mice generally revealed no significant findings, although small areas of hemorrhage, lymphocyte infiltration, and thick areas in the subcutis were noted in a subset of samples from both control and treated animals. These experiments suggest that the nanoparticle-based product would be safe for vaccines treating OUD.