Carrier-free photosensitizer nanocrystal for photodynamic therapy

In recent years, many nanomaterials have been developed as drug carriers to overcome their low solubility. However, the poor drug loading (general <5%) requires excessive use of carrier materials which may induce side effects and inhibit their clinical translation. Herein, hydrophobic meso- tetraphenylporphyrin (TPP) photosensitizer (PS) molecules are firstly assembled into pure nanocrystals by solvent exchange. Secondly, amphiphilic multidentate polymer ligand, PEG-grafted poly (maleic anhydride-alt-1-octadecene) (C ₁₈PMH-PEG), is modified on the nanocrystal surface to enhance their stability in saline. The as-prepared drug delivery system (DDS) by the two-step strategy significantly improves the drug loading (over 87%). The DDS shows high stability in saline and is engulfed by cancer cells. Further study demonstrates that the DDS is an effective photodynamic therapeutic agent of cancer cells while the free PS molecules quickly precipitate without obvious destruction of cancer cells.