Silver Nanoparticles from Oregano Leaves’ Extracts as Antimicrobial Components for Non-Infected Hydrogel Contact Lenses

Abstract

The oregano leaves’ extract (ORLE) was used for the formation of silver nanoparticles (AgNPs(ORLE)). ORLE and AgNPs(ORLE) (2 mg/mL) were dispersed in polymer hydrogels to give the pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2 using hydroxyethyl–methacrylate (HEMA). The materials were characterized by X-ray fluorescence (XRF) spectroscopy, X-ray powder diffraction analysis (XRPD), thermogravimetric differential thermal analysis (TG-DTA), derivative thermogravimetry/differential scanning calorimetry (DTG/DSC), ultraviolet (UV-Vis), and attenuated total reflection mode (ATR-FTIR) spectroscopies in solid state and UV–Vis in solution. The crystallite size value, analyzed with XRPD, was determined at 20 nm. The antimicrobial activity of the materials was investigated against Gram-negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). The Gram-positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus) are known to be involved in microbial keratitis by the means of inhibitory zone (IZ), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The IZs, which developed upon incubation of P. aeruginosa, E. coli, S. epidermidis, and S. aureus with paper discs soaked in 2 mg/mL of AgNPs(ORLE), were 11.7 ± 0.7, 13.5 ± 1.9, 12.7 ± 1.7, and 14.3 ± 1.7 mm. When the same dose of ORLE was administrated, the IZs were 10.2 ± 0.7, 9.2 ± 0.5, 9.0 ± 0.0, and 9.0 ± 0.0 mm. The percent of bacterial viability when they were incubated over the polymeric hydrogel discs of pHEMA@AgNPs(ORLE)_2 was interestingly low (66.5, 88.3, 77.7, and 59.6%, respectively, against of P. aeruginosa, E. coli, S. epidermidis, and S. aureus) and those of pHEMA@ORLE_2 were 89.3, 88.1, 92.8, and 84.6%, respectively. Consequently, pHEMA@AgNPs(ORLE)_2 could be an efficient candidate toward the development of non-infectious contact lenses.

Silver Nanoparticles Using Eucalyptus or Willow Extracts (AgNPs) as Contact Lens Hydrogel Components to Reduce the Risk of Microbial Infection

“…Bacteria such as P. aeruginosa, S. epidermidis and S. aureus often colonize materials such as contact lenses [ 2 , 3 ]. This means that there is a requirement for novel materials that can retain the benefits of typical contact lenses without the peril of severe bacterial infections [ 5 , 6 ]. Contact lenses are typically made from hydrogels based on pHEMA; this gives contact lenses the desirable water and oxygen permeability [ 7 , 8 ].…”

“…Contact lenses are typically made from hydrogels based on pHEMA; this gives contact lenses the desirable water and oxygen permeability [ 7 , 8 ]. The dispersion of an antimicrobial agent gives antibacterial properties to the polymeric material [ 5 , 6 , 9 ].…”

“…Two strategies have been developed, with the aim of forming new antimicrobial materials for contact lenses that are able to reduce microbial infection risk. One involves the usage of silver nanoparticles using extracts from natural products as a combined reducing and capping agent [ 6 ] while the second is the use of small molecules, which also act as antimicrobial agents [ 5 , 6 , 9 , 19 ]. The materials pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2, which contain silver nanoparticles AgNPs(ORLE) from oregano leaves’ extract (ORLE), were reported on recently [ 6 ].…”

“…One involves the usage of silver nanoparticles using extracts from natural products as a combined reducing and capping agent [ 6 ] while the second is the use of small molecules, which also act as antimicrobial agents [ 5 , 6 , 9 , 19 ]. The materials pHEMA@ORLE_2 and pHEMA@AgNPs(ORLE)_2, which contain silver nanoparticles AgNPs(ORLE) from oregano leaves’ extract (ORLE), were reported on recently [ 6 ]. The antimicrobial ability of these materials against the bacteria that are involved in the microbial contamination of contact lenses demonstrates the value of further research into this strategy [ 6 ].…”

Characterization of Biocompatible Hydrogel Lenses Using Methacrylic Acid with Neodymium Oxide Nanoparticles

“…In particular, in the case of nanoparticles, the physical properties are largely different depending on the type and size of the particles and sizes. There are several studies applying nanoparticles to contact lens materials, but it has been difficult to synthesize these particles and materials so as to secure compliance between materials [ 26 , 27 , 28 , 29 ]. However, the new materials must be compatible with the basic material of existing ophthalmic lenses: the hydrogel.…”