Inhalable spray dried human platelet lysate powders.

Human platelet lysate (PL) is a mixture of proteins containing growth factors, cytokines, and other biomolecules. PL shows promising effects on tissue regeneration and immunomodulation and may be applied to the lungs. Inhalation enables direct deposition of PL in the airways, maximising its therapeutic potential. This study aimed to develop inhalable spray dried PL powders with two excipients, trehalose and leucine. Spray dried PL alone contained 5% w/w residual solvent by mass and was amorphous, while powders containing excipients were partially crystalline with lower residual moisture content (2-4% w/w). Their particles were about 4 µm in volumetric size and exhibited hollow, rough-surfaced morphologies. Compared with spray dried pure PL, the excipient containing powders adsorbed significantly less moisture, and no recrystallisation was observed in the formulation with 60% w/w leucine. Our spray-drying process largely maintained protein content. Protein recovery was about 90% for spray dried PL alone, while the addition of trehalose further improved preservation. For aerosol performance, the fine particle fraction (FPF) of spray dried PL was 23%, with higher FPFs observed in the powders containing excipients. The highest FPF (34%) was achieved in the formulation with 60% w/w leucine. This formulation also significantly diminished the increased levels of nitric oxide and interleukine-6 (IL-6) in J774A.1 cells stimulated with lipopolysaccharide, indicating the preservation of immunomodulatory activity of PL in the inhalable powder. This study demonstrates the feasibility of producing inhalable and biological viable PL powders via spray drying and provides a proof of concept for developing platelet-based powders as potential treatments for lung conditions.