Synthesis of a PEGylated Dopamine Ester with Enhanced Antibacterial and Antifungal Activity

Abstract

Drug-polymer conjugation is a simple and efficient approach to synthesizing new, effective, and potent antimicrobial agents to counter the problem of microbial resistance. In the present study, a PEGylated dopamine ester (PDE) was synthesized using the PEGylation process and synthesis of PDE was confirmed by Fourier-transform infrared spectroscopy, elemental analysis (CHNS-O), and atomic force microscopy techniques. Later, the antimicrobial activity of PDE was assessed against four strains of bacteria (Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Proteus vulgaris; Gram (-)) and two fungi (Aspergillus niger and Aspergillus fumigatus) by the agar well diffusion method. The minimum inhibitory concentration (MIC) of PDE was also determined by the broth dilution method against bacteria. PDE showed significant zones of inhibition ranged from 21 to 27 mm for bacteria and 16 to 20 mm for fungi under study, which were much higher than those for dopamine hydrochloride. MIC values of PDE showed its potential antimicrobial property.

Scheme 1. Synthesis of PDE

Figure 1

(a) CHNS–O analysis of PDE and (b) PEG diacid.

Figure 2

(a) FTIR spectra of dopamine and PDE. (b) Raman spectra of PDE.

Figure 3

AFM images of PDE.

Figure 4

Images of antibacterial and antifungal activity of dopamine, PDE, and ampicillin (product in the pictures indicates PDE).

Figure 5

Images showing MIC values of PDE (top) and dopamine (bottom) against pathogenic bacterial strains.

Figure 6

Image showing the MIC value of dopamine ester (PDE) and dopamine against fungal strains.

Figure 7

Antifungal and antibacterial activity of PDE versus ampicillin (control).