ObjectivesNovel synthetic antimicrobial peptides which consist of a new immunomodulatory peptide 1018 and two different modifications with hydroxyapatite-binding affinity were developed. We compared the effect(s) of these peptides against oral plaque biofilms and measured their effectiveness in killing biofilm microbes and in reducing biofilm volume.Materials and methodsThe high affinity hydroxyapatite (HA)-binding peptide 1018 (SHABP), the mild affinity HA-binding peptide 1018 (MHABP), and peptide 1018 without additional amino acid sequence (peptide 1018) were synthesized. Oral multispecies biofilms were grown anaerobically for 3days. The biofilms were exposed to three peptides at two different concentrations (0.65 and 3.25mol/L) for 24, 48, and 72h. The biofilms were also treated for 3 or 9min with the peptides (3.25mol/L). The percentage of killed biofilm bacteria and biofilm volume were determined by using LIVE/DEAD viability staining and confocal laser scanning microscopy.ResultsSHABP was superior to MHABP and peptide 1018 in its killing efficacy of the pre-formed biofilms, especially at concentration of 3.25mol/L (p<0.05). SHABP performed also better than MHABP and peptide 1018 in reducing the overall biofilm volume at both concentrations (p<0.05). During the 3days of long-term exposure, MHABP and peptide 1080 killed more bacteria in the top half of the biofilms, compared to bottom half. SHABP killed more bacteria in the bottom half (39%) of the biofilms than in the top half (29%) at day 1 (p<0.05), whereas more bacteria were killed in the upper layers on days 2 and 3. SHABP killed a much higher percentage of plaque biofilm bacteria when used on 3-day-old biofilms for one or three times for 3min than MHABP or peptide 1018 at high concentration (p<0.05).ConclusionsThe modified peptide 1018 with high HA-binding affinity had higher antimicrobial activity against biofilm microbes and reduced biofilm volume more than the other peptides tested.Clinical relevanceModified peptide 1018 with high hydroxyapatite-binding affinity is a promising agent for use in oral antibiofilm strategies in the future.