Nanoparticles loaded with natural medicines for the treatment of Alzheimer's disease

Abstract

Alzheimer's disease (AD) is a progressive neurodegenerative disease that disrupts cognitive function and severely affects the quality of life. Existing drugs only improve cognitive function and provide temporary relief of symptoms but do not stop or delay disease progression. Recently, natural medicines, especially Chinese herbal medicines, have gained attention in the treatment of AD due to their antioxidant, anti-inflammatory, and neuroprotective effects. However, conventional oral dosage forms lack brain specificity and have side effects that lead to poor patient compliance. Utilizing nanomedicine is a promising approach to improve brain specificity, bioavailability, and patient compliance. This review evaluates recent advances in the treatment of AD with nanoparticles containing various natural medicines. This review highlights that nanoparticles containing natural medicines are a promising strategy for the treatment of AD. It is believed that this technology can be translated into the clinic, thereby providing opportunities for AD patients to participate in social activities.

Keywords: Alzheimer’s disease; Chinese herbal medicines; blood–brain barrier; nanoparticles; natural medicines.

Figure 1

The nanoparticles penetrate the blood–brain barrier and act on the central nervous system. The presence of the BBB is crucial for preventing harmful substances from entering the brain from the bloodstream. However, it also hinders the transfer of most small-molecule drugs and large molecules (such as peptides, proteins, and gene-based drugs), severely limiting the treatment of central nervous system diseases, such as neurodegenerative diseases, brain tumors, brain infections, and strokes. Nanoparticles, such as nanosuspensions, nanoemulsions, carbon nanotubes, immune liposomes, solid lipid nanoparticles, and liposomes, can be administered through the gastrointestinal system, respiratory tract, and nasal cavity. They can effectively traverse the blood–brain barrier and enter target brain cells, including neurons, microglial cells, and astrocytes. Natural compounds often face challenges in penetrating the blood–brain barrier. Therefore, nanoparticles can be employed to facilitate the delivery of active ingredients from natural compounds to the central nervous system, thereby exerting neuroprotective, anti-inflammatory, and antioxidant effects.

Figure 2

Natural herbal extract loaded on the nanoparticles. Natural medicines, especially Chinese herbal medicines, including but not limited to curcumin, berberine, quercetin, resveratrol, epigallocatechin gallate, and triptolide, are widely used to treat Alzheimer’s disease. However, these extracts tend to have large molecular weights that make it difficult for them to penetrate the blood–brain barrier to reach the brain. Herbal extracts loaded on the nanoparticles can maximize their utilization.