Synthesis of near infrared absorbing cationic zinc aminophthalocyanine and its application as an efficient photo-sensitizing nanoparticle in anti-drug-resistant bacteria

The emergence of drug-resistant bacteria threatens human health, and photodynamic therapy and photothermal therapy are promising methods to eliminate drug-resistant bacteria. However, the key to photodynamic and photothermal therapy is efficient photosensitizers, which are not fully developed. Herein, a novel cationic zinc aminophthalocyanine, zinc tetrakis(dimethyloctylammonium bromide) phthalocyanine (DMAZnPc-C8), is synthesized and investigated. The structures of the cationic zinc aminophthalocyanines are characterized by Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance hydrogen spectrum (1H NMR)，Mass spectrometry and X-ray spectroscopy. The singlet oxygen generation ability, photo-thermal properties and antibacterial properties against methicillin-resistant Staphylococcus aureus (MRSA) of cationic zinc aminophthalocyanine nanoparticles (DMAZnPc-C8 NP) in aqueous dispersion are investigated. The results show that the maximum ultraviolet absorption wavelength of DMAZnPc-C8 in DMSO is at 764 nm, and DMAZnPc-C8 shows good response to near-infrared light. DMAZnPc-C8 NP has good photo-thermal performance. After irradiation with an 808 nm laser (0.5 W/cm2) for 10 min, the temperature of DMAZnPc-C8 NP dispersion (0.05 mg/mL) is increased by 7.4 °C. And DMAZnPc-C8 NP has good singlet oxygen production capacity. DMAZnPc-C8 NP has excellent antibacterial effect against MRSA-resistant bacteria. When the concentration of DMAZnPc-C8 NP is 0.03 mg/mL, the growth of MRSA is almost completely inhibited after 10 min of laser irradiation at 808 nm (0.5 W/cm2), the antibacterial rate reach over 99 %. This study shows that cationic zinc aminophthalocyanine has promising application prospects in the field of anti-drug-resistant bacteria.