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The EPR-effect

Spago Nanomedical’s nanomaterials utilize the so-called EPR-effect (Enhanced Permeability and Retention) for tumor selective delivery of nanomedical diagnostic and therapeutic products. The EPR-effect is a phenomenon leading to enhanced accumulation of particles of certain sizes in tumors than in healthy tissues. The reason behind this is that blood vessels supplying solid tumor tissue are usually leaky.

In solid tumors, the aggressive growth of cells creates an increased demand for oxygen and nutrients. The cancer cells therefore give rise to an environment with increased levels of factors driving vascular growth. The uncontrolled growth of tumor vessels makes them immature, rigid and hyper-permeable – fundamentally different from healthy vessels which have strict borders regulating passage of larger molecules. Furthermore, lymphatic vessels that are responsible for draining tissues from liquid and metabolic products are frequently dysfunctional in tumors. Collectively, these factors lead to an effect called Enhanced Permeability and Retention (EPR)-effect. The EPR-effect was first described by Maeda et al., 1986.

When nanomaterials that are tailored with regards to size and chemical properties, are injected into the bloodstream they will remain within the vasculature of healthy tissue but they will leak out, or extravasate, into tumor tissues because of the increased permeability characterizing tumor vessels. The nanomaterials will then accumulate in tumor tissue due to the lack of functional lymphatic drainage.


The EPR-effect. Nanoparticles injected into the bloodstream will leak out into tumor tissue due to enhanced vessel leakiness which is a physiological feature separating healthy tissue from cancer tissue (enhanced permeability). A lack of functional lymphatic drainage gives rise to a retention effect (retention).

SpagoPix is a nanomaterial with paramagnetic manganese ions that selectively and passively accumulates in tumor tissue via the EPR-effect. The size of the contrast mediating nanomaterial and the retention effect enables a longer time-window for tumor visualization with MRI than what is possible with clinically available small-molecule MRI-contrast agents.

Tumorad is a nanomaterial loaded with radioactive isotopes that are chosen for optimized radiation type, range and half-life. After injection, the nanomaterial accumulates in tumors via the EPR-effect, and expose cancer cells to a controlled therapeutic radiation dose. Surrounding tissues are spared from radiation which reduces the risk of side effects.