Preparation of Memantine-Loaded Chitosan Nanocrystals: In Vitro and Ex Vivo Toxicity Analysis

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with unmet medical need, and is the leading cause of age-related dementia affecting millions of people worldwide. This work aims at developing small, high-drug loading capacity (DL) and -entrapment efficiency (EE) memantine hydrochloride (MEM)/chitosan nanocrystals (CS-NCs) to treat moderate to severe dementia associated with AD. MEM-loaded chitosan nanocrystals (MEM/CS-NCs, further abbreviated as MEM-NCs) were prepared by the ionic gelation method. Different formulations were prepared by varying the concentrations of CS and sodium tripolyphosphate (STPP). The prepared MEM-NCs formulations (n = 8) were evaluated for their particle size (PS), polydispersibility index (PDI), zeta potential (ZP), DL, EE and characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, in vitro (i.e., release behavior, cytotoxicity) and ex vivo studies (i.e., histopathology) studies were carried out. The results show that the DL was over 92% and the EE was higher than 73%, while the particles were relatively small with nanometric PS (152.63 +/- 12.95 to 310.23 +/- 10.49 nm), uniform with acceptable PDI (0.336 +/- 0.05 to 0.534 +/- 0.02), and stable with positive ZP (23.8 +/- 0.4 mV to 54.0 +/- 0.5 mV). The optimal formulation (MEM-NC3) was selected mainly based on the PS (152.63 +/- 12.95 nm), DL (98.44 +/- 3.31%), and EE (78.7 +/- 3.11%). Interestingly, it does not elicit any cytotoxic and tissue damage when examining at goat nasal mucosa. The selected formulation was subjected to surface morphological studies such as transmission electron microscopy (TEM), which revealed that the NCs were spherical in shape and small (100 nm). Interestingly, the selected formulation was able to sustain the drug release for up to 24 h with an initial burst release (86.51 %). We conclude that the prepared MEM-NCs represent a promising drug formulation for further in vivo studies (in animal models and in a clinical setting) to prevent and treat AD.