In vivo evaluation of novel particle-free polycaprolactone fillers for safety, degradation, and neocollagenesis in a rat model.

Dermal fillers have become popular due to the increased demand for skin rejuvenation products. Polycaprolactone (PCL), a newly developed bioresorbable medical polymer, has emerged as a durable and safe dermal filler. However, available PCL fillers cause irritation; carrier gels can coagulate PCL particles, block the injection needle, and cause nonhomogeneity of particle suspensions that could be responsible for the observed side effects. To relieve pain, premixing PCL filler with lidocaine. However, this formulation changes the property of the CMC portion of the PCL filler, and possibly results in an uneven suspension of the PCL particles. Hence, a particle-free PCL homogeneously solubilized in water was developed to overcome these limitations. This study aimed to assess the in vivo safety, biodegradability, and neocollagenesis ability of a novel PCL filler, DLMR01 using a rat model. Fillers were characterized after injecting a vehicle control or DLMR01 using a digital camera, folliscope, and a three-dimensional profiling system. Biopsy was performed to evaluate biocompatibility and neocollagenesis. Skin elasticity was measured using a Cutometer. DLMR01 caused no needle occlusion by particle aggregation or laborious injectability. Filler nodules dispersed to surrounding tissues within 6 hours without further granuloma formation. Histological inspection revealed no tissue residual material or foreign body reaction during the 12-week test period. DLMR01 increased dermal thickness, collagen regeneration, and skin elasticity. In conclusion, this study demonstrates the potential of DLMR01 for dermal rejuvenation in a rat model.