Abstract
Chitosan (CH) is a biopolymer that exhibits a number of interesting properties such as anti-inflammatory and antibacterial activity and is also a promising platform for the incorporation of photosensitizing agents. This study aimed to evaluate the efficacy of antimicrobial activity of chitosan hydrogel formulation alone and in combination with the methylene blue (MB) associated with antimicrobial photodynamic therapy (aPDT) against planktonic and biofilm phase of Propionibacterium acnes. Suspensions were sensitized with 12.5, 25.0, 37.5, 50.0 μg/mL of MB for 10 min and biofilms to 75, 100 and 150 μg/mL for 30 min then exposed to red light (660 nm) at 90 J/cm2 and 150 J/cm2 respectively. After treatments, survival fractions were calculated by counting the number of colony-forming units. The lethal effect of aPDT associated with CH hydrogel in planktonic phase was achieved with 12.5 µg/mL MB and 1.9 log10 biofilm reduction using 75 µg/mL MB. Rheological studies showed that formulations exhibited pseudoplastic non-Newtonian behavior without thixotropy. Bioadhesion test evidenced that the formulations are highly adhesive to skin and the incorporation of MB did not influence the bioadhesive force of the formulations.
Highlights
Acne vulgaris exemplifies a disease whose main bacterium related to its etiology is theGram-positive Propionibacterium acnes (P. acnes)
The present study aimed to evaluate the in vitro efficacy of a chitosan hydrogel formulation alone and chitosan hydrogel doped with methylene blue as a photosensitizer to be associated with antimicrobial photodynamic therapy (aPDT) under irradiation of a red light emitting system (660 nm) against P. acnes in planktonic and biofilm phase
In addition to the surface characteristics of the microorganisms, there are several factors that may interfere with the antimicrobial activity of chitosan inherent in the polymer itself, such as molecular weight, positive charge density, hydrogel concentration, and external factors such as ionic strength and pH, being able to justify the results found in planktonic phase [28]
Summary
Acne vulgaris exemplifies a disease whose main bacterium related to its etiology is theGram-positive Propionibacterium acnes (P. acnes). When the infectious process is installed and follicle rupture occurs, P. acnes can reach more superficial layers of the skin such as the epidermis, characterizing the disease [1]. This dermatosis is mainly observed in adolescents and young adults, being more prevalent in males and more precocious in female adolescents [2]. The disease is not associated with severe morbidity, it causes patients significant psychological repercussions, among them, low self-esteem, social inhibition, depression and anxiety, mainly due to scarring that can be minimized with appropriate early treatment [3]. There are a large number of acne treatment options available to patients
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