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.