Background: Monopolar radiofrequency devices for facial skin tightening offer a promising non-invasive approach that targets the deep dermis to prompt immediate collagen contraction and subsequent remodeling.However, non-clinical evidence supporting the efficacy and mechanisms of action of these treatments remains limited, despite their increasing use. This study aimed to evaluate the effectiveness and safety of a dualfrequency non-invasive monopolar radiofrequency (NMRF) device using a porcine model, directly comparing a conventional 6.78 MHz setting with a dual-frequency (6.78 + 2 MHz) mode. Methods: Female porcine subjects were treated using an innovative NMRF device (XERF; Cynosure Lutronic Inc.). Efficacy was assessed histologically for up to 1 month. Safety was evaluated through thermal skinsurface monitoring and standard assessments. Results: When compared with 6.78 MHz alone, the dual-frequency (6.78 + 2 MHz) mode produced greater immediate thickening and shortening of deep dermal collagen bundles and more prominent remodeling of subcutaneous fibrous septa. At 1 month, the dual-frequency treatment yielded larger increases in dermal collagen density, more regular bundle alignment, and higher elastin signals. Surface temperature remained below 43ºC, and no tissue damage was observed following NMRF treatment. Conclusion Our research strongly indicates that immediate tissue contraction occurs following treatment and that dual-frequency application results in more substantial collagen reconstruction. In the long term, NMRF stimulates the production of new collagen and elastin. The dual-frequency mode enhances these effects, supporting its use in effective and safe skin tightening and rejuvenation.

BACKGROUND: Bone growth factors, particularly bone morphogenic protein-2 (BMP-2), are required for effective treatment of significant bone loss. Despite the extensive development of bone substitutes, much remains to be desired for wider application in clinical settings. The currently available bone substitutes cannot sustain prolonged BMP-2 release and are inconvenient to use. In this study, we developed a ready-to-use bone substitute by sequential conjugation of BMP to a three-dimensional (3D) poly(L-lactide) (PLLA) scaffold using novel molecular adhesive materials that reduced the operation time and sustained prolonged BMP release. METHODS: A 3D PLLA scaffold was printed and BMP-2 was conjugated with alginate-catechol and collagen. PLLA scaffolds were conjugated with different concentrations of BMP-2 and evaluated for bone regeneration in vitro and in vivo using a mouse calvarial model. The BMP-2 release kinetics were analyzed using ELISA. Histological analysis and microCT image analysis were performed to evaluate new bone formation. RESULTS: The 3D structure of the PLLA scaffold had a pore size of 400 lm and grid thickness of 187–230 lm. BMP-2 was released in an initial burst, followed by a sustained release for 14 days. Released BMP-2 maintained osteoinductivity in vitro and in vivo. Micro-computed tomography and histological findings demonstrate that the PLLA scaffold conjugated with 2 lg/ml of BMP-2 induced optimal bone regeneration. CONCLUSION The 3D-printed PLLA scaffold conjugated with BMP-2 enhanced bone regeneration, demonstrating its potential as a novel bone substitute.