Crystal Engineering: Upcoming Paradigm for Efficacious Pulmonary Drug Delivery

Background and objective: Pulmonary drug delivery has transformed over a past few decades from being a platform for local pulmonary disease treatment to systemic drug delivery opportunities. In case of pulmonary delivery systems, particle properties are critical as they affect inhalation efficacy, pulmonary deposition, drug delivery and overall performance. With this in view, particle engineering has emerged as an advanced science that helps in designing of efficacious pulmonary delivery systems. Among various particle engineering branches, crystal engineering is being extensively explored as it provides an opportunity to optimize particles at morphological, physicochemical and molecular levels which are essential to understand the role of crystal engineering in pulmonary drug delivery. Methods: A thorough literature survey in the field of crystal engineering approaches explored for pulmonary drug delivery was conducted and the collected data was meticulously studied and summarized. Results: In the review, pulmonary system is discussed with respect to various sites for drug deposition in respiratory tract, mechanism of drug deposition and clearance. Further, critical crystal parameters are discussed in-depth and various crystal engineering methods are summarized with emphasis on their impact on pulmonary delivery. Also, inhalation devices are overviewed to understand their performance in relation to crystal based pulmonary formulations. Conclusion: The review enabled a detailed insight on crystal engineering approaches for design of pulmonary delivery systems.