Casein-loaded proteoliposomes: Drug Delivery Systems and Potential Inhibitors in Aβ1-40 Fibrillogenesis

Abstract

Alzheimer's disease (AD) represents the most common cause of dementia worldwide. The early symptom is usually a short-term memory loss, followed by symptoms including problems with language, disorientation, mood swings, loss of motivation, not managing self-care, and behavioral issues, until loss of body functions and, ultimately, death. The cause of AD is poorly understood and the diagnosis is complex. One of the main AD hallmarks is the extracellular deposition in brain tissue of proteinaceous amyloid plaques, composed by well-ordered fibrillary aggregates of the amyloid β-peptide (Aβ). The Aβ aggregation process follows typical nucleation-polymerization kinetics, characterized by structural intermediates with relevant cytotoxic activity. Such smaller soluble Aβ prefibrillar oligomers result indeed the most toxic species, able to interact with membranes by interfering with the cell function. Therefore, novel therapeutic strategies target oligomers or prefibrillar aggregates rather than mature fibers. At this regard, αs1-Casein results able to inhibit the nucleation phase by sequestering the Aβ peptide on its surface and thus slowing down the entire Aβ1-40 fibrillogenesis process. αs1-Casein is a natural amphiphilic almost unfolded protein. In order to be useful as an inhibitor for AD treatment, it is crucial to define a way to efficiently protect αs1-Casein and deliver it to the brain in a controlled way. Liposomes are spherical phospholipids-based vesicles characterized by excellent biocompatibility and biodegradability, low toxicity, ability to incorporate and protect both hydrophilic and hydrophobic drugs as well as ability to cross the Blood Brain Barrier in order to access the Central Nervous System. Based on these considerations, novel proteoliposomes composed by phospholipids, cholesterol and αs1-Casein were prepared and characterized. The proteoliposome preparation protocol was optimized in order to obtain the best results. Nanosystems were characterized by different biophysics techniques such as: light scattering, zeta-potential, laurdan fluorescence, chromatography and AFM imaging.