Targeting Acne Bacteria and Wound Healing In Vitro Using Plectranthus aliciae, Rosmarinic Acid, and Tetracycline Gold Nanoparticles

Isa A Lambrechts; Velaphi C Thipe; Kattesh V Katti; Vusani Mandiwana; Michel Lonji Kalombo; Suprakas Sinha Ray; Rirhandzu Rikhotso; Arno Janse van Vuuren; Tenille Esmear; Namrita Lall

doi:10.3390/ph15080933

Targeting Acne Bacteria and Wound Healing In Vitro Using Plectranthus aliciae, Rosmarinic Acid, and Tetracycline Gold Nanoparticles

Pharmaceuticals (Basel). 2022 Jul 28;15(8):933. doi: 10.3390/ph15080933.

Authors

Affiliations

¹ Department of Plant and Soil Sciences, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield, Pretoria 0002, South Africa.
² Department of Radiology, Institute of Green Nanotechnology, University of Missouri Columbia, Columbia, MO 65212, USA.
³ Chemical Cluster, Centre for Nanostructures and Advanced Materials, Council for Scientific and Industrial Research, Pretoria 0184, South Africa.
⁴ DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0184, South Africa.
⁵ Centre for High-Resolution Transmission Electron Microscopy, Nelson Mandela University, Port Elizabeth 6001, South Africa.
⁶ School of Natural Resources, College of Agriculture, Food and Natural Resources, University of Missouri, Columbia, MO 65211, USA.
⁷ College of Pharmacy, JSS Academy of Higher Education and Research, Mysuru 570015, India.

Abstract

Gold nanoparticles from plant extracts and their bioactive compounds to treat various maladies have become an area of interest to many researchers. Acne vulgaris is an inflammatory disease of the pilosebaceous unit caused by the opportunistic bacteria Cutibacterium acnes and Staphylococcus epidermis. These bacteria are not only associated with inflammatory acne but also with prosthetic-implant-associated infections and wounds. Studies have hypothesised that these bacteria have a mutualistic relationship and act as a multispecies system. It is believed that these bacteria form a multispecies biofilm under various conditions and that these biofilms contribute to increased antibiotic resistance compared to single-species biofilms. This study aimed to investigate the antibacterial and wound healing potential of synthesised gold nanoparticles (AuNP_s) from an endemic South African plant, Plectranthus aliciae (AuNP_PAE), its major compound rosmarinic acid (AuNP_RA) and a widely used antibiotic, tetracycline (AuNP_TET). Synthesised gold nanoparticles were successfully formed and characterised using ultraviolet-visible spectroscopy (UV-vis), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ-potential), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED), and they were investigated for stability under various biological conditions. Stable nanoparticles were formed with ζ-potentials of -18.07 ± 0.95 mV (AuNP_PAE), -21.5 ± 2.66 mV (AuNP_RA), and -39.83 ± 1.6 mV (AuNP_TET). The average diameter of the AuNP_s was 71.26 ± 0.44 nm, 29.88 ± 3.30 nm, and 132.6 ± 99.5 nm for AuNP_PAE, AuNP_RA, and AuNP_TET, respectively. In vitro, biological studies confirmed that although no antibacterial activity or biofilm inhibition was observed for the nanoparticles tested on the multispecies C. acnes and S. epidermis systems, these samples had potential wound closure activity. Gold nanoparticles formed with rosmarinic acid significantly increased wound closure by 21.4% at 25% v/v (≈29.2 µg/mL) compared to the negative cell control and the rosmarinic acid compound at the highest concentration tested of 500 µg/mL. This study concluded that green synthesised gold nanoparticles of rosmarinic acid could potentially be used for treating wounds.

Keywords: Cutibacterium acnes; Plectranthus aliciae; Staphylococcus epidermidis; antibiotic resistance; gold nanoparticles; rosmarinic acid; tetracycline; wound healing.

Abstract

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