Gene delivery to periodontal tissue using Bubble liposomes and ultrasound

Background and Objective Periodontitis is the most common inflammatory disease caused by oral biofilm infection. For efficient periodontal treatment, it is important to enhance the outcome of existing regenerative therapies. The physical action of an ultrasound may be able to deliver a therapeutic gene or drugs into the local area of the periodontium being treated for periodontal regeneration. Previously, we developed “Bubble liposomes” as a useful carrier for gene or drug delivery, and reported that delivery efficiency was increased with high‐frequency ultrasound in vitro and in vivo. Hence, the aim of the present study was to examine the possibility of delivering genes into gingival tissues using Bubble liposomes and ultrasound. Material and Methods We attempted to deliver naked plasmid DNA encoding luciferase or enhanced green fluorescent protein (EGFP) into the lower labial gingiva of Wistar rats using Bubble liposomes, with or without ultrasound exposure. Ultrasound parameters were optimized for intensity (0‐4.0 W/cm2) and exposure time (0–120 s) to establish the most efficient conditions for exposure. The efficacy and duration of gene expression in the gingiva were investigated using a luciferase assay and fluorescence microscopy. Results The strongest relative luciferase activity was observed when rats were treated under the following ultrasound conditions: 2.0 W/cm2 intensity and 30 s of exposure time. Relative luciferase activity, 1 d after gene delivery, was significantly higher in gingiva treated using Bubble liposomes and ultrasound than in gingiva of the other treatment groups. Histological analysis also showed that distinct EGFP‐expressing cells were observed in transfected gingiva when rats were treated under optimized conditions. Conclusion From these results, the combination of Bubble liposomes and ultrasound provides an efficient technique for delivering plasmid DNA into the gingiva. This technique can be applied for the delivery of a variety of therapeutic molecules into target tissue, and may serve as a useful treatment strategy for periodontitis.