Formulation and Evaluation of Antibacterial Creams and Gels Containing Metal Ions for Topical Application

Abstract

Background. Skin infections occur commonly and often present therapeutic challenges to practitioners due to the growing concerns regarding multidrug-resistant bacterial, viral, and fungal strains. The antimicrobial properties of zinc sulfate and copper sulfate are well known and have been investigated for many years. However, the synergistic activity between these two metal ions as antimicrobial ingredients has not been evaluated in topical formulations. Objective. The aims of the present study were to (1) formulate topical creams and gels containing zinc and copper alone or in combination and (2) evaluate the in vitro antibacterial activity of these metal ions in the formulations. Method. Formulation of the gels and creams was followed by evaluating their organoleptic characteristics, physicochemical properties, and in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus. Results. Zinc sulfate and copper sulfate had a strong synergistic antibacterial activity in the creams and gels. The minimum effective concentration was found to be 3 w/w% for both active ingredients against the two tested microorganisms. Conclusions. This study evaluated and confirmed the synergistic in vitro antibacterial effect of copper sulfate and zinc sulfate in a cream and two gels.

Figure 1

Spreadability values for the selected cream (C1) and gels (G1 and G5) compared to various marketed products (n = 3, results shown as mean ± SD).

Figure 2

Viscosity curves for the selected cream (C1) and gels (G1 and G5) (n = 3, results shown as mean ± SD).

Figure 3

Antimicrobial activity of copper sulfate and zinc sulfate solutions in various concentrations against Escherichia coli and Staphylococcus aureus (n = 3, results shown as mean ± SD) (p = 0.05).

Figure 4

Antimicrobial activity of the selected cream (C1) containing copper sulfate and zinc sulfate in various concentrations against (a) Escherichia coli and (b) Staphylococcus aureus (n = 3, results are shown as mean ± SD) (p = 0.05).

Figure 5

Antimicrobial activity of the selected cream (C1), gels (G1 and G5), and three marketed products (Nexcare Cold Sore Treatment Cream, Campho-Phenique Cold Sore Treatment Gel, and Equate Diaper Rash Relief Cream) against Escherichia coli and Staphylococcus aureus (n = 3, results shown as mean ± SD).

Figure 6

Antimicrobial activity of one of the selected gels (G5) during the stability testing compared to the control (gentamicin) against Escherichia coli (n = 3, results shown as mean ± SD).