Multidrug-resistant pathogenic microorganisms have become a serious threat to public health, making it difficult to prevent, treat and fight the infections. This drug resistance is often associated with the overuse and misuse of antibiotics [1]. In this light, silver nanoparticles (Ag-NPs) arise as potential antimicrobial agents for being toxic and lethal against a wide range of microorganisms [2]. In addition, Ag-NPs can also cooperate with other biomolecules, such as polymers with antimicrobial properties to increase their biocidal activity. Among these polymers, dopamine (DA) could be a good alternative to be combined with silver, since it presents great adhesive properties and strong biocompatibility, making it an excellent fit for numerous biological applications [3].
Therefore, for this work, Ag-NP and DA nanoconjugates were formulated based on electrostatic interactions and characterized by UV–Vis spectra measurements, showing a decrease in the silver peak when covered with DA. A scanning electron microscopy (SEM) analysis showed an increase in size when dopamine was conjugated with the Ag-NPs; and Fourier transformed infrared spectroscopy (FTIR) analysis confirmed the presence of DA mixed with the Ag-NPs.
Next, the antimicrobial properties of DA-coated Ag-NPs (Ag-NPs and DA) against the Gram-positive Staphylococcus aureus (S. aureus) and the Gram-negative Escherichia coli (E. coli) bacteria, as well as the antifungal effect against Candida albicans (C. albicans), was assessed and compared with DA and Ag-NPs alone.
So far, the results revealed that Ag-NP and DA nanoconjugates presented higher antibacterial and antifungal effects when compared with Ag-NPs and DA alone. Further experiments will comprise the cytotoxicity evaluation of these nanoparticles, as well the characterization of their ability to successfully deliver drugs and genetic information.
Author Contributions
Conceptualization, J.F.A.V. and Â.S.; writing—original draft preparation, D.P., J.F.A.V. and Â.S.; writing, review and editing, J.F.A.V., Â.S., S.F. and N.A.; funding acquisition, J.F.A.V., N.A., Â.S. and D.P. All authors have read and agreed to the published version of the manuscript.
Funding
This work was funded by the Fundação para a Ciência e a Tecnologia (FCT) and Centro2020 through the following Projects: UIDB/04044/2020, UIDP/04044/2020, UIDB/00709/2020, PAMIROTEIRO/0328/2013 (No. 22158), MATIS (CENTRO-01-0145-FEDER-000014) and Centro-01-02B7-FEDER-069244. D. Pereira acknowledges her PhD fellowship (Ref. 2021.09331.BD).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
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