Freeze-dried chitosan nanoparticles to stabilize and deliver bromelain

Bromelain has many therapeutic properties including wound healing and blood circulation improvement. However, bromelain is usually unstable and suffers autolysis, which results in a decrease of enzymatic activity and limited applications. Encapsulation of bromelain in nanoparticles can diminish degradation by protease immobilization, which may increase its stability and efficacy. The natural polymer chitosan can be nanostructured and trap the enzyme, maintaining the claims of biocompatibility, biodegradability and natural source of the formulation ingredients. Considering the above, chitosan-bromelain nanoparticles (C-B-NP) were produced by ionic crosslinking and presented spherical shape (electron microscopy) of 100.9 +/- 0.5 nm and polydispersity index of 0.222 +/- 0.012 (dynamic light scattering). Encapsulation efficiency was calculated as 85.1 +/- 1% with regard to enzymatic activity, and C-B-NP presented 4.9 U/mL of enzymatic activity, which corresponds to 104.7% of free bromelain activity, confirming its integrity upon encapsulation. However, C-B-NP were unstable when stored in aqueous suspension, leading to freeze-drying studies of the formulation. Glycine and maltose were used as potential lyoprotectors and the formulation optimized by a factorial design; resultant products presented short resuspension time, slightly altered nanoparticles mean size and increased encapsulation rate compared to the previous liquid form. Maltose was able to better maintain formulation's enzymatic activity over time (90 days), especially when stored under refrigeration. Therefore, freeze-dried C-B-NP can effectively improve bromelain and nanoparticle stability, which allow further in vivo applications as a dried powder for topical administration or as a raw material for other dosage forms. (AU)