Evaluation of porphyrin loaded dry alginate foams containing poloxamer 407 and -cyclodextrin-derivatives intended for wound treatment

Dry alginate foams intended for antibacterial photodynamic therapy (aPDT) of infected wounds were prepared. aPDT is a treatment modality involving light of appropriate wavelength, oxygen and a photosensitizer (PS) to produce radicals that attack biological targets (e.g. bacteria). The hydrophobic 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) was chosen as a model PS and loaded into the foams. The foams contained a poloxamer (Pluronic F127) and/or -cyclodextrin (CD)-derivatives, i.e. methylCD (MCD), heptakis(2,6-di-O-methyl)-CD (HkCD) or hydroxypropylCD (HPCD).The physical characteristics of the various foams prepared and the THPP load, release and photostability were evaluated. All the foams were thin and flexible and could easily be handled and cut to fit a potential wound. Fast disintegration were observed for dry foams in water or phosphate buffered saline, while in Hanks' balanced salt solution the foams absorbed liquid without losing their integrity. All the foams had a similar THPP load of 0.12-0.13% w/w. The presence of CD-derivatives improved THPP release, however, no differences were observed between the different types of CD-derivatives evaluated. THPP loaded into the foams was photolabile, which induced a color change combined with fading. Alginate foams formulated with PF127, CD-derivatives and THPP demonstrated applicability as delivery vehicles for PSs in aPDT of wounds.