The encapsulation of active substances offers significant advantages for various pharmaceutical applications. In this study, we explored the potential of nanotechnology to enhance the efficacy of the organic selenium compound 7-chloro-4-(phenylselanyl) quinoline (4-PSQ) by encapsulating it within ethylcellulose polymeric nanocapsules. Initially, we developed and characterized the nanocapsule containing 4-PSQ. To evaluate their safety and pharmacological benefits, we conducted a series of studies, including hemolysis assays (in vitro), neurotoxicity assessments usingCaenorhabditis elegans, and analyses of hepatic and renal toxicity in Swiss mice. The pharmacological activity of 4-PSQ nanocapsules (4-PSQ NCs) was further investigated in nociception and acute inflammation models in male and female Swiss mice. The physicochemical characteristics of 4-PSQ NC comply with nanometric standards and allow for controlled release in vitro. In toxicity evaluations, 4-PSQ NCs exhibited reduced hemolytic and neurotoxic effects compared to the free compound (4-PSQ Free). Furthermore, oxidative damage markers and plasma biomarkers showed no significant differences between the encapsulated and free forms of 4-PSQ. Treatment with 4-PSQ Free or 4-PSQ NC demonstrated antinociceptive and antiedematogenic effects in the glutamate and hot plate tests
however, 4-PSQ NCs showedsignificantly greater efficacy. Furthermore, 4-PSQ NC showed a prolonged effect, reducing mechanical hypersensitivity in the inflammatory pain model induced by Complete Freund's Adjuvant. These findings highlight the potential of 4-PSQ NCs as a novel and promising strategy for developing safer and more effective analgesic and anti-inflammatory therapies.