Mesoporous silica nanoparticle incorporation of essential oils onto synthetic textiles for tailored antimicrobial activity

Lillie, John (2016) Mesoporous silica nanoparticle incorporation of essential oils onto synthetic textiles for tailored antimicrobial activity. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Healthcare associated infections (HCAI) impose significant financial and environmental problems for modern healthcare settings, therefore it is important to develop novel strategies to combat HCAIs and the causative microorganisms. This study investigates the use of an encapsulated essential oil (EO) antimicrobial coating for textiles in the healthcare environment. The antimicrobial activity of several EOs were studied, individually and in blends, against five microorganisms associated with HCAI (Staphylococcus aureus, methicillin resistant Staphylococcus aureus, Candida albicans, Escherichia coli, and Pseudomonas aeruginosa). A 1:1 blend of cinnamon (CIN) and clove oils (CLO) containing 94.8 % (v/v) eugenol (by GC-MS) showed the highest antimicrobial efficacy and gave a minimum inhibitory concentration (MIC) of less than 0.25% (v/v). Mesoporous silica nanoparticles (MSN) were used to encapsulate volatile EOs. The MSNs displayed narrow size distribution, high surface area and pore size between 1.8-2.2 nm. MSNs, directly loaded with CIN:CLO blend (72 % by mass of MSN), achieved bactericidal values (25-50 mg/mL) against the test microorganisms. Dynamic killing profiles of the EO loaded MSNs against the test microorganisms were recorded. The highest kill rates were observed during the first 15 minutes of contact. Organically modified silica (ormosil) gels were synthesised to provide thin film coverage of synthetic fibres. Gamma-methacryloxypropyltrimethoxysilane (-MPS) was used to attach un-loaded MSNs to the ormosil coating. A layer-by-layer treatment method provided good coverage of synthetic fibres with MSNs, as evidenced by scanning electron microscopy (SEM). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to monitor the layer-by-layer treatment sequence. Head space GC-MS sampling of EO loaded MSN treated textile coupons showed that EO was able to diffuse from the MSN mesopores after being bonded to the synthetic fibres. The EO loaded MSN textile coupons were microbiologically challenged using a method based on AATCC 100. The EO loaded MSN textile coupons displayed good antimicrobial activity over five washing cycles using a method based on (AATCC 61 and 135) thereby indicating a degree of controlled release.