Incorporating small molecules or biologics into nanofibers for optimized drug release: A review

Over the past several decades, the formulation of novel nanofiber-based drug delivery systems focusing on specific delivery purposes has been investigated worldwide with a continuous level of interest. The unique structure and properties of nanoscale fibrous systems, such as their high specific-area-to-volume ratio and high porosity and the possibility of controlling their crystalline-amorphous phase transitions, make them a desirable formulation pathway to satisfy the needs of recent pharmaceutical development. Fibrous delivery systems can facilitate the accelerated dissolution and increased solubility of small molecules and can also be useful in controlling drug delivery over time (for local or systemic drug administration). In the latter case, the release periods can be tuned over a wide range (from hours to weeks), e.g., by adjusting the fiber diameter and selecting the appropriate polymers. The solubility of the polymer, the fiber diameter and the fiber structure are the primary parameters affecting drug release. In addition to immediate and sustained release, other release profiles, such as biphasic release, can also be achieved. Chemical conjugation and surface functionalization offer further possibilities for the control of drug release. In the case of small molecules, developments focus mostly on overcoming the unfavorable physicochemical nature of the active agents. By contrast, in the preparation of macromolecule-loaded nanofibers, maximizing the biological activity of the macromolecules presents the greatest challenge. The authors' intent is to provide a comprehensive overview of the key parameters of advanced drug delivery systems of this type.