The blood-brain barrier is one of the body's most effective protective interfaces. It helps keep harmful substances away from the brain, but it also blocks many medicines from reaching brain tissue. This barrier remains a major challenge for treating neurological diseases, including Alzheimer's disease, Parkinson's disease and malignant glioma.
Nanomedicines offer one possible route forward because they can be designed to interact with natural transport pathways at the barrier. Yet their performance in the body is often difficult to predict. A nanocarrier that looks precisely engineered in the laboratory may look very different once it enters the bloodstream. Proteins rapidly attach to its surface and form a protein corona. This layer can hide engineered targeting ligands, introduce new biological signals or redirect the carrier toward clearance organs.
In a new Perspective published in Science Bulletin, Changjian Xie, Iseult Lynch, Chunying Chen and Zhiling Guo argue that the protein corona should not be treated only as an unwanted coating. Instead, they propose that it can act as a dynamic navigation interface that shapes how nanomedicines are recognized, internalized, sorted and released across the blood-brain barrier.
The article moves the discussion beyond passive leakage. In many brain diseases, passive movement through a disrupted barrier is limited, heterogeneous or unreliable. Receptor-mediated transcytosis provides a more physiologically relevant route because it couples recognition at the endothelial surface with directional transport through the cell. The authors emphasize that successful delivery depends not only on uptake, but also on the intracellular pathway that follows uptake.
The Perspective organizes protein corona behavior into five connected stages. These are circulatory screening, receptor binding, internalization, intracellular trafficking and release on the brain side. During circulation, coronas rich in immune proteins may promote rapid clearance, while coronas enriched in selected dysopsonins or receptor-facing proteins may extend circulation and improve the chance of blood-brain barrier engagement. At the endothelial surface, corona components such as apolipoproteins or transferrin may help connect nanocarriers with receptors including LRP1 and transferrin receptor.
After internalization, the corona continues to change. Blood-derived proteins can be replaced or supplemented by proteins from endocytic and cellular compartments. This remodeling may determine whether a carrier is recycled back to the blood, sent to lysosomes for degradation or transported toward release on the brain side. The authors therefore highlight intracellular sorting and polarized exocytosis as central design challenges for brain-targeted nanomedicine.
The article also reviews strategies for manipulating the corona. These include tuning particle size, surface chemistry and lipid composition to bias the corona that forms in vivo. Another approach is recruitable corona engineering, in which nanocarriers are designed to capture functional endogenous proteins in blood and use them as biological bridges to endothelial receptors. Biomimetic pre-coating and shielding strategies may also help extend circulation while preserving access to the receptors needed for transport.
Several translational bottlenecks remain. Only a small fraction of injected nanomedicine typically reaches diseased tissue, and brain delivery faces additional constraints from the blood-brain barrier, blood-tumor barrier and active efflux systems. Rodent models may overestimate delivery potential. Stimulus-responsive carriers may release their payload too early in off-target tissues. Long-term safety, anti-PEG immune responses and scalable quality control also require closer attention.
Glioblastoma presents a particularly difficult case. The disease contains regions with an intact blood-brain barrier and regions with a more permeable blood-tumor barrier. This creates uneven nanomedicine exposure within and between lesions. The authors suggest that future development will need more informative models and trial designs that combine molecular profiling with biodistribution, pharmacokinetic and imaging readouts.
Looking ahead, the authors call for precision corona design. Future nanocarriers may need to be matched to patient-specific plasma protein fingerprints and disease states. Near-native corona capture, top-down proteomics, molecular dynamics simulation, artificial intelligence-assisted prediction, brain organoids and blood-brain-barrier-on-chip systems could together turn the protein corona into a measurable and programmable quality attribute for brain delivery.
By reframing the protein corona as a stage-aware and potentially programmable interface, the Perspective provides a roadmap for making blood-brain barrier transcytosis more predictable, controllable and clinically relevant.
