Near-infrared light-triggered methylene blue/berberine co-loaded polydopamine nanoparticles modified with sialic acid for Alzheimer's disease therapy.

Due to the existence of the blood-brain barrier (BBB) and the complicated pathological mechanisms of Alzheimer's disease (AD), current therapeutic approaches for AD show limited efficacy. To overcome these challenges, a multi-strategy drug delivery system (SA-BP-MB/BBR NPs) was developed: photothermal conversion polydopamine nanoparticles (PDA NPs) were decorated with sialic acid-modified bovine serum albumin (SA-BSA) to prepare SA-modified and BSA-stabilized PDA NPs (SA-BP NPs) for targeting the BBB and co-loaded with photosensitizer methylene blue (MB) and berberine (BBR) to target multiple neuropathological factors, including Aβ aggregation and tau hyperphosphorylation. The prepared SA-BP-MB/BBR NPs had spherical morphology with a uniform particle size of 143.43 nm and PDI of 0.095. Drug loading capacities were 6.98 % for MB and 3.50 % for BBR. Our investigations demonstrated that the cellular uptake efficiency of biocompatible SA-BP-MB/BBR NPs increased by 1.74 times when combined with photothermal and photodynamic therapy, which effectively inhibited Aβ aggregation, Aβ fibril depolymerization, and tau hyperphosphorylation. Pharmacokinetics and in vivo biodistribution studies revealed a higher area under the curve (AUC) of SA-BP-MB/BBR NPs (9.75 and 7.52 times higher) than free MB and BBR, and SA modification promoted brain accumulation. Overall, SA-BP-MB/BBR NPs have the potential to be an effective treatment for AD.