Syntesis, spectroscopies properties and photodynamic activity of Zn (II) phthalocyanine-polymer conjugates as antimicrobial agents

BAIGORRIA ESTEFANÍA; MILANESIO M. ELISA; DURANTINI EDGARDO N.

EUROPEAN POLYMER JOURNAL

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020

0014-3057

The discovery of antibiotics has produced a large incidence in the reduction of diseases caused by microorganisms. However, the combination of different factors is related to the appearance of microbial strains with resistance to them. In this sense, the PDI could become a tool for the eradication of diseases of microbial origin. Different studies have shown that the cationic phthalocyanine derivatives can act as efficient phototherapeutic agents. In this work, a new Zn(II)phthalocyanine bearing a carboxylic acid group (A-ZnPc 3) was obtained from hydrolysis reaction of ester group present in the precursor phthalocyanine (Bn-ZnPc 2). The asymmetric Bn-ZnPc 2 was synthesized by the ring expansion reaction of boron(III) subphthalocyanine (SubPc) chloride with an appropriated phthalonitrile derivative (Bn-Pn 1). A-ZnPc 3 was designed to obtain two conjugates with cation polymers. Thus, A-ZnPc 3 was attached to chitosan (CH-ZnPc 4) and polyethylenimine (PA-ZnPc 5), through the amide bond. The peak at 1550 cm-1 was observed in the IR spectrum and confirms the amide bond formation. UV-visible absorption and fluorescence spectra presented the characteristic bands of phthalocyanines in N,N-dimethylformamide (DMF), with appropriate fluorescence quantum yield (F). These conjugates were able to photosensitize singlet molecular oxygen in DMF and aqueous medium with quantum yields of about 0.45 and 0.30, respectively. Also, the formation of superoxide anion radical was detected by nitro blue tetrazolium reduction in the presence of NADH. The results showed that type II mechanism is involved in the photodescomposition of L-Trp sensitized by these conjugates in presence of ROS scavenges. Photoinactivation of microorganisms was investigated in Staphylococcus aureus, Escherichia coli and Candida albicans, varying the concentration of CH-ZnPc 4 and PA-ZnPc 5 and the irradiation times. A similar efficiency was observed in the eradication of S. aureus (6 log decrease) for both conjugates, while that PA-ZnPc 5 was the most effective for the PDI of C. albicans. The efficiency of these conjugates in the photoinactivation of E. coli was scarce. However, the addition of chitosan polymer (0.25 mg/mL) allowed improving the photoinactivation of this Gram-negative bacterium. These results indicate that PA-ZnPc 5 conjugate is an efficient photosensitizer to inactivate S. aureus and C. albicans. In addition, it is capable of killing Gram-negative bacteria, such as E. coli, in the presence of chitosan.