Chitosan–Silver Nanoconjugates to Achieve Enhanced Antimicrobial Effect and Fight Cervical Cancer ^†

Cervical cancer (CC) is considered to be the fourth most frequently diagnosed cancer worldwide and the second leading cause of cancer deaths in women, causing about 10 premature deaths per week in women in the age group 20–39 years [1]. Human papillomavirus (HPV) is the most common sexually transmitted virus and the main cause of CC [2]. Considering that there are several materials, such as polymers and metal nanoparticles, which possess antimicrobial properties against different pathogens, they can also be an asset against HPV. Amongst these materials, chitosan (CH) arises as a potential natural polymer with antibacterial, antifungal and antiviral properties, whilst being non-toxic to human cells, biocompatible and biodegradable [3]; silver nanoparticles (Ag–NPs), which present antimicrobial and potent antiviral effects against various human pathogenic viruses, such as HPV, also arise as potential microbicidal agents [4,5].

Hence, this work presents the first steps towards the formulation and characterization of nanoconjugates based on CH with an Ag–NPs core (Ag–NPs + CH). These materials conjugations are intended to enhance the antimicrobial properties of each of the materials alone, producing a more effective antimicrobial effect. After the formulation of nanoconjugates by electrostatic interactions between the negatively charged CH polymer particles and the positively charged surface of Ag–NPs, different characterization methodologies were applied, namely, UV–vis spectra to trace the efficiency of Ag–NPs coating with CH; scanning electron microscopy (SEM) to analyze the nanoparticles diameter across the coating; and Fourier transformed infrared spectroscopy (FTIR) to chemically verify the Ag–NPs coating with CH. Additionally, the antibacterial effects of these nanoconjugates 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), were also assessed.

In general, the results revealed that it was possible to conjugate the Ag–NPs with the CH: UV–vis spectra measurements show the decrease in the silver peak when covered with CH; using SEM analysis, an increase in size was observed from 10 nm (Ag–NPs) to a mean diameter of 123 nm (Ag–NPs + CH); and in FTIR analysis, the correspondence between peaks was seen, being further confirmation of the CH coating in the Ag–NPs surface. Additionally, from the antimicrobial evaluation, it was possible to observe that the Ag–NPs + CH nanocomplexes presented better results than the Ag–NPs alone. Furthermore, antiviral assays are being scheduled to assess the capacity of the Ag–NPs + CH complex to inhibit different types of viruses to find whether they can be an asset when fighting CC induced by HPV infection.