Significant increase in the water dispersibility of zinc phthalocyanine nanowires and applications in cancer phototherapy

The phototherapy is one of the widely accepted noninvasive clinical methodologies to eradicate cancer cells owing to its minimal side effects and high selectivity to the light of specific wavelength. As represented by photodynamic (PD) and photothermal (PT) therapy, the phototherapy requires light and photosensitizer to generate reactive oxygen species and heat, respectively. Zinc phthalocyanine (ZnPc) is one of the promising photosensitizers as it has a strong absorption cross-section in the spectral range of 650-900 nm that guarantees maximum tissue penetration. One critical issue in using Pc molecule, including ZnPc as a biocompatible sensitizer is the poor water solubility. To increase water solubility, various chemical modifications inducing hydrophilicity have been widely attempted to introduce various functional groups in the ZnPc backbone. We report that ZnPc nanowires (NWs) directly grown from ZnPc powder by vaporization-condensation-recrystallization process show surprisingly increased water dispersibility without any functionalization. The ZnPc NW solution exhibits highly efficient dual PD and PT effects upon the irradiation of near infrared (808 nm) laser. The dual phototherapeutic effect of ZnPc NW is proven to enhance cytotoxic efficiency according to both in vitro and in vivo experimental results. NPG Asia Materials (2012) 4, e12; doi:10.1038/am.2012.22; published online 13 April 2012