2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/167076We consider a ubiquitous scenario where a fluctuating, semipermeable vesicle is embedded in solution while enclosing a fixed number of solute particles. The swelling with increasing number of particles or decreasing concentration of the outer solution exhibits a continuous phase transition from a fluctuating state to the maximum-volume configuration, whereupon appreciable pressure difference and surface tension build up. This criticality is unique to particle-encapsulating vesicles, whose volume and inner pressure both fluctuate. It implies a universal swelling behavior of such vesicles as they approach their limiting volume and osmotic lysis.4 pages, 1 figureSoft Condensed MatterStatistical Mechanicstext