Electrospun Polyvinylpyrrolidone Fibers for Fast-Dissolving Drug Delivery: Defining the Viscosity Window and Evaluating the Role of Molecular Weight

Background/Objectives: Electrospun polyvinylpyrrolidone (PVP) fibers are highly promising for fast-dissolving drug delivery. Methods: In this study, five PVP grades with molecular weights ranging from 4000 to 1,300,000 Da were investigated over a broad concentration range (10–60 w/w%) to evaluate their electrospinnability and dissolution behavior. Results: A well-defined viscosity window of approximately 150–680 mPa·s was identified for the formation of continuous, bead-free fibers. Deviations from this optimal window resulted in electrospraying or jet instability. Continuous fibers were successfully prepared from all investigated PVP grades, including low-molecular-weight PVP K-12 (Mw 4000), demonstrating that appropriate solution viscoelasticity can compensate for limited chain entanglement. Remarkably, in vitro testing revealed that all fibrous formulations exhibited ultrafast disintegration (0.29–1.33 s) and dissolution (0.39–2.32 s). Statistical analysis confirmed no significant differences attributable to polymer molecular weight or fiber diameter, effectively challenging the common assumption that higher-molecular-weight PVP delays disintegration. Instead, the immediate dissolution originates from rapid wetting and capillary-driven fluid uptake, facilitated by the highly porous nano- and microfibrous network. Conclusions: By highlighting the dominant role of macroscopic structural properties over polymer chain length, these findings provide a practical framework for the development of fast-dissolving electrospun PVP-based drug delivery systems.