A roadmap for nanomedicine's 'long march': New review systematically charts path to brain
Researchers detail the multi-step cascade of challenges and innovative material strategies for delivering drugs across the formidable blood-brain barrier.
image: This schematic illustrates the multi-step journey and key strategies for brain-targeted nanomedicines. It highlights the primary challenge: crossing the Blood-Brain Barrier (BBB), a complex structure composed of endothelial cells (ECs), tight junctions, pericytes, and astrocytes. To navigate this, nanoparticles are engineered with surface modifications. Once across the BBB, further targeting strategies are employed to reach brain lesions, including the use of external physical stimuli, targeting the lesion's microenvironment, or specific cells within it. These advanced nanoparticles serve as versatile carriers for a range of therapeutic payloads, including gene editing systems, nucleic acids, antibodies, chemical drugs, antibody-drug conjugates, and fluorescent proteins.
Credit: Rui Ye et al., Nano Research
The blood-brain barrier (BBB) is a formidable defense system, a near-impenetrable wall that protects the brain from toxins and pathogens. But this same shield poses a monumental challenge for medicine, blocking more than 98% of potential drugs from reaching their targets in the central nervous system (CNS). This obstacle severely hinders treatment for devastating conditions like glioblastoma, Alzheimer's disease, and Parkinson's disease.
Engineered nanoparticles, or nanomedicines, have emerged as a leading strategy to overcome this barrier. These tiny carriers can encapsulate therapeutic agents and are designed to navigate the body's complex biological landscape. However, the journey from intravenous injection to a specific diseased cell in the brain is a perilous one, a "long march" with numerous hurdles. A failure at any single step can lead to the failure of the entire mission.
To address this, a team of researchers from Sichuan University, Sichuan Cancer Hospital, and other institutions has published a comprehensive review in the journal Nano Research. The paper systematically outlines the critical multi-step biological cascade required for successful brain-targeted drug delivery and details the innovative functional nanomaterial strategies designed to conquer each stage. This work provides a holistic roadmap for a field striving to translate laboratory breakthroughs into clinical realities.
"For decades, the blood-brain barrier has been the 'Mount Everest' of drug delivery," said Shugang Qin, a corresponding author of the study. "While many brilliant strategies have been developed, they often focus on a single obstacle. We realized the field needed a holistic, end-to-end perspective. A nanocarrier's journey is a multi-stage relay race; winning one leg doesn't matter if you drop the baton in the next."
The review meticulously details the four crucial stages of this "race":
Systemic Circulation Survival: Upon injection, nanoparticles must evade the body's immune surveillance, primarily the mononuclear phagocyte system in the liver and spleen, which is primed to clear foreign invaders. The review discusses strategies like "stealth" coatings (e.g., PEGylation) and biomimetic camouflage (e.g., cloaking nanoparticles with cell membranes) to prolong circulation time.
Blood-Brain Barrier Penetration: The central challenge. The authors analyze three main approaches: passive targeting that exploits the leaky vasculature in some disease states; active targeting that uses ligands to engage with specific transporters or receptors on the BBB to "trick" their way across; and physical-assisted methods that use external energy like focused ultrasound or magnetic fields to temporarily open the barrier.
Precision Targeting in the Brain Microenvironment: Once inside the brain, the nanoparticle must navigate to the specific pathological lesion. This is achieved by designing "smart" nanoparticles that respond to unique cues of the disease microenvironment, such as lower pH, elevated enzyme activity, or oxidative stress, triggering drug release or activation only at the desired site.
Intra-lesional Cell-Specific Action: The final step involves the nanoparticle being taken up by the correct target cell (e.g., a tumor cell, not a healthy neuron) and then escaping the "cellular prison" of the endosome/lysosome to release its therapeutic payload into the cytoplasm or a specific organelle.
"The key takeaway is that success isn't about a single 'magic bullet' but about a series of intelligent, coordinated engineering choices," Wang explained. "It's about creating a nanocarrier that is a master of disguise in the blood, a skilled lock-picker at the BBB, a precise navigator within the brain, and finally, a clever escape artist inside the target cell."
By synthesizing a vast body of research into a coherent framework, the authors provide a valuable resource for material scientists, pharmacologists, and clinicians. The review aims to guide the rational design of next-generation nanomedicines that can successfully complete the entire journey to the brain.
"Our ultimate goal with this review is to provide a clear and actionable framework for researchers," Qin concluded. "By understanding the entire biological cascade and the corresponding material solutions, we can design smarter, safer, and more effective nanomedicines, hopefully shortening the long road from the lab bench to the patient's bedside."
The paper's authors include Rui Ye, Yupei Zhang, Xiangyu Jiao, Wan Xu, Yan Chen, Li Nai, Qiaoshan Guo, Junyu Wang, Zhihe Zhao, Shenbin Liu, and Shugang Qin.
This work was supported by the Technology Innovation R&D Project from the Science and Technology Bureau of Chengdu, Sichuan Province, the National Natural Science Foundation of China, and the Sichuan Province Science and Technology Support Program.
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.