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Title: Biopolymer scaffolds for use in delivering antimicrobial Sophorolipids to the acne-causing bacterium propionibacterium acnes

Author
item Ashby, Richard - Rick
item Zerkowski, Jonathan
item Solaiman, Daniel
item Liu, Linshu

Submitted to: New Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2010
Publication Date: 1/1/2011
Citation: Ashby, R.D., Zerkowski, J.A., Solaiman, D., Liu, L.S. 2011. Biopolymer scaffolds for use in delivering antimicrobial Sophorolipids to the acne-causing bacterium propionibacterium acnes. New Biotechnology. 28(1):24-30.

Interpretive Summary: Acne is a common ailment amongst the adolescent population which can result in scarring and more significantly, self-image problems. Currently, there are a number of treatments for acne most of which focus on inhibiting pore blockage, killing the causative bacterium (Propionibacterium acnes), limiting the inflammation and/or regulating hormone levels. Each of these treatments carries side-effects that make it less than ideal. Currently, two popular treatments include the application of ointments containing benzoyl peroxide and/or oral or topical antibiotic treatments. However, benzoyl peroxide has been known to cause localized skin irritations and the potential for bleaching while prolonged antibiotic treatments may cause bacterial resistance which limits effectiveness. Sophorolipids (SLs) are molecules that are produced by yeasts from renewable resources and have been documented to be effective in controlling P. acnes. In this study we demonstrated the effectiveness of SL application using four different biodegradable polymers (pectin, alginate, poly-3-hydroxybutyrate, and poly-3-hydroxybutyrate-co-10%-3-hydroxyhexanoate) as molecular scaffolds to introduce the SL molecules to the acne-causing organism. Data suggested that pectin-, alginate-, (long chain plant sugars) and both polyhydroxyalkanoate (bacterial storage molecules)-SL composite films all proved successful in combating P. acnes. However, pectin- and alginate-based SL composite films required dramatically less SL to be effective thereby favoring moderate to fast release applications. In addition, these films remained comparatively transparent in the presence of SL which may be more appealing for visible/facial applications. On the other hand, PHA-SL films required a higher SL concentration to induce the antimicrobial effects on P. acnes but, as the SL concentration increased the films became more opaque making these composites more favorable for slower-release, nonvisible applications. Results of this study may help to direct treatments more towards the use of biological polymers and SLs in anti-acne applications thereby eliminating many of the current and potential side-effects that existing treatments present.

Technical Abstract: Sophorolipids (SLs) are known to possess antimicrobial properties towards many species (particularly Gram-positive, or Gram+) of bacteria. However, they can only be exerted if the SLs can be introduced to the bacterial cells in an acceptable manner. Propionibacterium acnes is the common bacterial cause of acne. It is a Gram+ facultative anaerobe that is susceptible to the action of SLs. In this study we demonstrated that different biopolymer matrices could be used to produce SL composite films that exert various antimicrobial efficiencies against P. acnes. Increasing SL concentrations in poly-3-hydroxybutyrate (PHB) and PHB-co-10%-3-hydroxyhexanoate (PHB/HHx) resulted in noticeably improved (PHB/HHx was best) antimicrobial activity based on the size of the zones of inhibition using an overlay plating technique on synthetic growth medium. However, increasing concentrations of SLs in PHB and PHB/HHx films also increased film opacity, which diminishes the likelihood of use especially in visible (facial) areas. Pectin- and alginate- improved the transparent character of SL composite films while also acting as successful carriers of SLs to P. acnes. The lactone form of the SLs proved to exhibit the best antimicrobial action and in concert with either pectin or alginate biopolymers provided a comparatively transparent, successful means of utilizing SLs as a renewable, environmentally benign anti-acne solution with the potential for minimal side effects.