RESUMEN
We report surprising results for the self-assembly of lecithin (a common phospholipid) in water-ethanol mixtures. Lecithin forms vesicles (â¼100 nm diameter) in water. These vesicles are transformed into small micelles (â¼5 nm diameter) by a variety of destabilizing agents such as single-tailed surfactants and alcohols. In a surfactant-induced vesicle-micelle transition (VMT), vesicles steadily convert to micelles upon adding the surfactantâthereby, the turbidity of the solution drops monotonically. Instead, when an alcohol like ethanol is added to lecithin vesicles, we find a new, distinctive pattern in phase behavior as the ethanol fraction feth in water is increased. The turbidity first decreases (from feth = 0 to 37%), then rises sharply (feth = 37 to 50%), and then eventually decreases again (feth > 55%). Concomitant with the turbidity rise, the vesicles separate into two phases around feth = 50% before a single phase reappears at higher fethâin other words, there is a "re-entrant" phase transition from 1-phase to 2-phase and back to 1-phase with increasing feth. Vesicles near the phase boundary (â¼feth = 45%) also show a VMT upon heating. Similar patterns are seen with other alcohols such as methanol and propanol. We ascribe these complex trends to the dual role played by alcohols: (a) first, alcohols reduce the propensity for flat lipid bilayers to bend and form closed spherical vesicles; and (b) second, alcohols diminish the tendency of lipids to self-assemble in the solvent mixture. At low alcohol fractions, (a) dominates, causing the initially unilamellar vesicles to grow into multilamellar vesicles (MLVs), which eventually phase-separate. Thereafter, (b) dominates, and the vesicles convert into micelles. Support for our hypothesis comes from scattering (SANS) and microscopy (cryo-TEM). Thus, we have uncovered a general paradigm for lipid self-assembly in solvent mixtures, and this may even have physiological relevance.
RESUMEN
BACKGROUND: Phalloplasty procedures are performed to create a phallus, typically as a gender-affirming surgery for treating gender dysphoria. Due to the controversial nature of this specific procedure, more innovation is needed to directly assist surgical teams in this field. As a result, surgeons are left to improvise and adapt tools created for other procedures to improve surgical outcomes. This study developed a patient-specific 3D printed model from segmented computed tomography (CT) scans to accurately represent the relevant vasculature necessary for anterolateral thigh (ALT) flap phalloplasty. The surgical procedure seeks to maintain intact vessels that derive from the descending branch of the lateral circumflex femoral artery, typically found traveling within the intermuscular septum between the rectus femoris and vastus lateralis. METHODS: In this study, we created and printed 3D models of the leg and vasculature using two techniques: (1) a standard segmentation technique with the addition of a reference grid and (2) a bitmap method in which the total CT volume is colorized and printed. RESULTS: The results gathered included the physician's view on the model's accuracy and visualization of relevant anatomy. Bitmap-printed models resulted in a high amount of detail, eliciting surgeons' undesirable reactions due to the excess of information. The hybrid method produced favorable results, indicating positive feasibility. CONCLUSIONS: This study tested the ability to accurately print a patient-specific 3D model that could represent the vasculature necessary for ALT flap procedures and potentially be used in surgical reference and planning in the future. A surgeon performing phalloplasty procedures discussed their approval of both models and their preference for grid creation and application.