Abstract

The synthetic antimicrobial peptide SAAP-148 was found to be effective against a wide range of (antimicrobial-resistant) gram-positive and gram-negative bacteria, in vitro and in a superficial skin infection model in mice, but not a surgical wound infection model in rats. In addition, the efficacy of SAAP-148 in protein-rich environments such as blood plasma and eschar extract is considerably reduced as compared to PBS. The aim of the present study is to determine which wound-related factors reduce SAAP-148’s efficacy. As high dosages of SAAP-148 may be required in infected wounds we also assessed the in vitro and ex vivo cytotoxicity of SAAP-148. Preincubation of SAAP-148 in 50% (v/v) blood plasma or eschar extract for 24 h, 3% (v/v) bovine serum albumin or a collagen-elastin 3D matrix significantly reduced the bactericidal efficacy of the peptide. Also, the presence of protease inhibitors did not restore the bioactivity of SAAP-148, suggesting a reduced bioavailability of SAAP-148 due to protein binding, rather than degradation. Furthermore, relatively low concentrations of SAAP-148 (≥0.23 nmol/100 µl) induced cytotoxicity for human skin cells in 2D culture. Contrarily, SAAP-148 did not induce cytotoxicity for cells in ex vivo human skin. In addition, unlike silver sulfadiazine (SSD), SAAP-148 showed no statistically significant adverse effects on the re-epithelialization of ex vivo excision wounds and burn wounds. Hence, SAAP-148 potentially has a beneficial profile for antimicrobial treatment of infected wounds.

Key words: SAAP-148, proteolytic degradation, bioactivity, peptide interaction, cytotoxicity, skin and soft tissue infection.

Abbreviation

AMPs, antimicrobial peptides; BrdU, 5-bromo-2- deoxyuridine; BSA, bovine serum albumin; CFU, colony forming units; DMEM, Dulbecco's Modified Eagle Medium; DNA, deoxyribonucleic acid; EDTA, ethylenediaminetetraacetic acid; EWM, excision wound model; FCS, fetal calf serum; LB, Luria Bertani; LDH, lactate dehydrogenase; MRSA, methicillin resistant Staphylococcus aureus; PBS, phosphate-buffered saline; P/S, penicillin/streptomycin; RPMI, Roswell Park Memorial Institute; SD, standard deviation; SPS, sodium polyanethol sulfonate; SSD, silver sulfadiazine.