Staphylococcus epidermidis, a human skin commensal, is the most frequent isolate from infections of medical indwelling devices. This fact reflects the ubiquitous nature of S. epidermidis on the skin and the risk of contamination of a medical device before or during insertion1. A counteraction strategy is to develop coatings of medical devices to reduce bacterial adhesion and kill adhered microbes.
The global rise in antibiotic resistance calls for new treatment options, such as antibacterial photodynamic therapy2. The resulting formation of reactive oxygen species and /or toxic photoproducts may reduce resistance development compared to traditional antibiotics. Curcumin2 is a plant-derived food colourant (E100) which absorbs violet-blue light (λmax430 nm). Its physico-chemical properties demand addition of excipients to increase solubility and stability, such as the Pluronic® F 127 (poloxamer 407) 3.
Curcumin was synthesised as previously described2 and protected from light. Curcumin was dissolved in DMSO and diluted in Pluronic® F 127 (dissolved in PBS)3. Irradiation of samples was performed with visible light in the absorption range of curcumin (radiant exposure: 18 J/cm2). S. epidermidis (ATCC 35984) were grown in brain heart infusion (5% CO2). Aggregation of S. epidermidis was investigated by light microscopy after growth in liquid media. Bacterial adhesion was investigated after 90 minutes exposure to Pluronic® F 127-coated surfaces of a 12 well plate (Corning). Bacterial adhesion and survival were also studied in Pluronic® F 127/curcumin-coated wells as described above when simultaneously exposed to blue light.
Pluronic® F 127 dissolved in the medium induced aggregation of S. epidermidis in a concentration dependent manner. Pluronic® F 127 (8%)-coated (without curcumin) surfaces reduced adhesion of S. epidermidis 157-fold compared to uncoated surfaces. The anti-adhesive properties of Pluronic® F 127 were preserved in samples containing curcumin with and without blue light as well as to the light control alone. Photoactivated curcumin dissolved in Pluronic® F 127 reduced the number of viable adhered S. epidermidis.
DISCUSSION & CONCLUSIONS
Pluronic® F 127 may be used as an excipient in curcumin formulations for application in antibacterial photodynamic therapy to reduce adhesion and eradicate adhered bacteria. Further investigations must be carried out to reveal the susceptibility of S. epidermidis biofilms to the experimental combination of treatment agents.
1Uçkay I, Pittet D, Vaudaux P, Sax H, Lew D, Waldvogel F. Foreign body infections due to Staphylococcus epidermidis. Ann Med. 2009;41:109-19
2Wikene KO, Bruzell E, Tønnesen HH. Characterization and antimicrobial phototoxicity of curcumin dissolved in natural deep eutectic solvents. Eur J Pharm Sci. 2015;80:26-32
3Vukićević M, Hegge AB, Vulić P, Tønnesen HH. Poloxamer-based curcumin solid dispersions for ex tempore preparation of supersaturated solutions intended for antimicrobial photodynamic therapy. Pharm Dev Technol. 2015; 20: 863–871
Antibacterial and anti-adhesive properties of Pluronic® F127 solutions in the absence or presence of photoactivation
H. Valen1, B. Blomqvist2, I. S Dragland1, I.Tho2, E. Bruzell1, H. H. Tønnesen2
1 Nordic Institute of Dental Materials, Oslo, Norway
2 Department of Pharmacy, School of Pharmacy, University of Oslo, Oslo, Norway