(T1230-08-48) Non-Invasive Mechanical Disruption of Adipocytes via NIR-Triggered Gold Nanoparticle/Perfluorohexane Synergistic Cavitation: A Safe and Targeted Fat Reduction Strategy

Purpose: The global obesity epidemic has created an urgent need for non-invasive, precision-targeted fat reduction technologies. Current gold-standard methods (e.g., liposuction, cryolipolysis) either require surgical intervention or lack cellular-level specificity, leading to variable efficacy and potential off-target damage. Photothermal therapies using gold nanoparticles (AuNPs) have shown promise for localized hyperthermia, yet their impact on adipocytes remains limited by insufficient thermal dose and collateral tissue heating. We hypothesized that coupling AuNPs with perfluorohexane (PFH) nanodroplets could create a dual-modal disruption mechanism: (1) AuNP-mediated near-infrared (NIR) photothermal conversion to heat PFH above its boiling point (56 °C), and (2) PFH vaporization-induced cavitation micro-bubbles that mechanically rupture adipocyte membranes. This synergy would achieve (i) precise, on-demand fat cell ablation with minimal thermal diffusion, and (ii) enhanced safety via reduced surface temperature and localized mechanical force. The present study aimed to validate this concept in vitro using 3T3-L1-induced adipocytes and in vivo in a diet-induced obese mouse model, quantifying fat reduction, histopathology, and systemic safety markers.

Methods: AuNPs were conjugated with cysteine for biocompatibility, then assembled with PFH nanodroplets. Phospholipids were used to encapsulate PFH droplets with AuNPs, and peptides that target adipocytes were modified on the surface of the liposomes. Dynamic light scattering confirmed a hydrodynamic diameter of about 100 nm and electric neutrality. The photothermal properties of the prepared nanoparticles were examined. In Vitro Validation. 3T3-L1 adipocytes (differentiated for 10 days) were treated with PFH-Au@lipo and irradiated by 808 nm NIR laser (0.75 W/cm², 5 min). Cell electron microscope, cell permeability, cell viability (MTT), membrane integrity (LDH release), and lipid content (Oil Red O and lipid droplet immunofluorescence staining) were quantified within 24 h. In Vivo Studies. The connection or disconnection of fat-targeting peptides was examined in terms of the accumulation of particles in adipose tissue. Diet-induced obese C57BL/6 mice (n=6/group) received intraperitoneal injection of Au-PFH@lipo in inguinal fat pads, followed by NIR irradiation (0.5 W/cm², 10 min). During the experiment, body weight was recorded regularly. After the experiment, the fat tissue was photographed and the main organs were collected. Histology (H&E, immunofluorescence and immunohistochemistry) and serum markers (ALT, AST, UREA, CREA) assessed safety. Statistical Analysis. Data are mean ± SD. One-way ANOVA with Tukey’s post-hoc test (p < 0.05 significance).

Results: Material Characterization & Photothermal Performance The prepared PFH-Au@lipo nanoparticles exhibited uniform size distribution and demonstrated robust photothermal conversion capability at 808 nm. In Vitro Adipocyte Response. LDH release assays indicated acute membrane disruption within 2 hours of PFH-Au@lipo + NIR treatment, accompanied by visible lipid droplet extrusion. Time-lapse imaging captured the dynamic process of cell membrane repair, with structural integrity fully restored by 8 hours. Remarkably, 24-hour viability assessments confirmed near-complete cellular recovery, highlighting the material's capacity for controlled, reversible adipocyte targeting. In Vivo Therapeutic Outcomes. Mice receiving PFH-Au@lipo + NIR demonstrated progressive reductions in body weight and BMI throughout the study period. Post-treatment analysis revealed significant decreases in hepatic fat accumulation and adipose tissue mass. Histological examination showed marked reduction in adipocyte size without evidence of tissue necrosis. Immunostaining and blood panels collectively confirmed the absence of inflammatory responses or organ toxicity, supporting the treatment's favorable safety profile.

Conclusion: This study demonstrates the first successful integration of AuNP photothermal conversion with PFH cavitation for non-invasive adipocyte ablation. The dual-modal approach achieved (1) superior fat reduction (20% weight loss in vivo), and (2) an exceptional safety profile with minimal thermal diffusion and no systemic inflammation. The localized mechanical disruption mechanism overcomes key limitations of conventional photothermal therapies, offering a translatable strategy for precision fat reduction. Future work will optimize dosing, explore long-term metabolic effects, and scale to human clinical trials. Overall, AuNPs and PFH synergistic cavitation represents a paradigm shift toward safe, effective, and non-surgical body contouring.

Fabrication and Physicochemical Characterization of PFH-Au@lipo
A：Schematic illustration depicting the stepwise fabrication process of PFH-Au@lipo.
B：Transmission Electron Microscopy (TEM) image of Au NPs.
C：TEM image of PFH-Au@lipo.
D：Size distribution profile of PFH-Au@lipo.
E：Zeta potential distribution of PFH-Au@lipo.
F-G：Photothermal performance assessment of PFH-Au@lipo under 808 nm laser irradiation (0.75 W/cm²): (F) Infrared thermal images illustrating temperature elevation at varying PFH-Au@lipo concentrations; (G) Corresponding temperature-time curves quantifying the photothermal heating effect.

Interactions Between PFH-Au@lipo and Adipocytes
A：TEM images capturing ultrastructural changes in adipocytes at 0 h, 5 min, 1 h, 2 h, and 8 h post - incubation with PFH-Au@lipo+NIR.
B：Cell viability assay results for adipocytes treated with different formulations in 24 h.
C: Lactic dehydrogenase (LDH) level quantification in adipocytes exposed to PFH-Au@lipo+NIR.
D：Fluorescence microscopy images of adipocytes incubated with different formulations, stained with DAPI (nuclei, blue) and BODIPY (lipid droplets, green).

In Vivo Evaluation of PFH-Au@lipo
A：In vivo fluorescence imaging quantified results comparing the adipose-targeting capability of PFH-Au@lipo with/without the adipocyte-targeting sequence.
B-C：Photographs of mice and excised adipose tissues from different treatment groups.
D-E：Longitudinal monitoring of relative body weight (D) and (E) body mass index (BMI) in mice across different treatment groups.
F：Hematoxylin and Eosin (H&E) - stained histological sections of skin and inguinal tissues from treated mice.
G：Serum biochemical markers (ALT, AST, CREA, UREA, TC, TG) measurements for mice in various treatment groups.