Dry vacuum‐assisted hydration method: A new accelerating method for reconstitution of injectable Poly‐D,L‐lactic acid

Injectable poly-D,L-lactic acid (PDLLA) is a collagen-stimulating filler (AestheFill; REGEN) supplied as lumps of lyophilized powder in vials. Reconstitution with sterile water for injection (SWFI) is required before injection.1, 2 Typically, this involves a reconstitution time of 20–30 min by adding SWFI into the vial and shaking. In 2020, Lin et al.3, 4 proposed a rapid “back-and-forth” reconstitution method, which takes about 5–10 min. Considering that the hydration time of the PDLLA lumps is a crucial step in the reconstitution process, in 2021, they introduced an even faster “vacuum-assisted hydration” (VAH) prior to the back-and-forth technique, which only takes less than 1 min.5 In 2023, Victor Cheong modified and proposed a different VAH method. This article aims to introduce this new method and compare it with the previous VAH method. Lin's VAH method relies on the Boyle's law, which establishes a reciprocal correlation between the pressure and volume of a constant quantity of gas.5, 6 This method is described as follows: A P-syringe housing PDLLA lumps is securely attached to an S-syringe containing SWFI via a 3-way stopcock. After pushing the SWFI into the P-syringe and expelling most of the air, the plunger of the P-syringe is pulled to create negative pressure. At this point, the air within the PDLLA lumps expands, bursts out, and rises to the water surface. Upon releasing the plunger, the air volume within the lumps immediately contracts, drawing surrounding SWFI into them swiftly. The hydration process for all the PDLLA lumps can be completed by repeating these steps twice.5 (Figure 1; Video 1) Cheong's VAH method also relies on the Boyle's law. A P-syringe housing PDLLA lumps and an unoccupied S-syringe are firmly linked through a 3-way stopcock. Then, the plunger of the S-syringe is withdrawn to introduce a negative pressure within both syringes. After that, the valve of 3-way stopcock is turned to close the opening of the P-syringe to maintain the negative pressure inside. By repeating these steps twice, the pressure inside the P-syringe is near a vacuum. Next, draw the desired amount of water into the S-syringe. Reconnect it to the 3-way stopcock. Upon opening the valve connecting these two syringes, the SWFI will be drawn quickly into the P-syringe along with the PDLLA lumps, facilitated by the existing vacuum. The hydration process of all the PDLLA lumps is also very short using this method. (Figure 2; Video 2). To distinguish between these two methods, we refer to Lin's method as the “wet” VAH method, while Cheong's method is known as the “dry” VAH method. Both methods are grounded in Boyle's law, capitalizing on the rapid air volume/pressure changes within PDLLA lumps to expedite the hydration process. The key distinction lies in the vacuum procedure, where it occurs before or after soaking PDLLA lumps in SWFI. In the hands of experienced practitioners, both wet and dry VAH methods are straightforward and innovative, often taking no more than 1 min to complete. However, there are certain drawbacks associated with these methods. The transfer of PDLLA lumps from the vial to the P-syringe may pose a risk of contamination or accidental spillage.4 Moreover, practitioners must possess a thorough understanding of the entire procedure, as any air leakage during the creation of vacuum within the P-syringe could lead to process failure. In conclusion, both wet and dry VAH methods offer simplicity and speed. Nonetheless, strict adherence to aseptic procedures is paramount, and practitioners must have a comprehensive grasp of the entire process. The authors specially thank Sunny Fu and Wen-Yi Yen for their kindly assistance for the video clip filming and editing. The wording of this manuscript is modified by ChatGPT-3.5. Dr. Lin J-Y and Dr. Lin C-Y are medical consultants of Jiangsu Wuzhong Aesthetic Biotech., and medical directors of REGEN Biotech. Dr. Cheong V M-K is a speaker for REGEN Biotech. No ethical approval was required as this artical has no original research data. Video 1. Video 2. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.