A Single-Blind Study Evaluating the Efficacy of Gold Nanoparticle Photothermal-Assisted Liposuction in an Ex Vivo Human Tissue Model

Abstract

Background: Liposuction is one of the most performed cosmetic surgery procedures. In a previously reported study, gold-nanoparticle (GNP) laser-assisted liposuction (NanoLipo) was shown to improve procedure parameters and outcomes in a porcine model.

Objectives: An ex vivo human liposuction model was developed to assess the ease, efficacy, and outcomes of NanoLipo, and to further explore its mechanism of action in facilitating liposuction.

Methods: NanoLipo was compared to a control without GNPs in sets of fresh, nonperfused, anatomically symmetric, matched tissue specimens from 12 patients. A subset of three experiments was performed under single-blinded conditions. Intraoperative assessments included lipoaspirate volume, percentage of free oil, ease of removal, and temperature rise. Specimens were palpated, visualized for evenness, and graded with and without skin. Postoperative assessment included viability staining of the lipoaspirate and remaining tissues. Microcomputed tomography was used to assess the distribution of infused GNPs within the tissues.

Results: NanoLipo consistently removed more adipose tissue with more liberated triglycerides compared to control. NanoLipo specimens were smoother, thinner, and had fewer and smaller irregularities. Infused solutions preferentially distributed between fibrous membranes and fat pearls. After NanoLipo, selective structural-tissue disruptions, indicated by loss of metabolic activity, were observed. Thus, NanoLipo likely creates a bimodal mechanism of action whereby fat lobules are dislodged from surrounding fibro-connective tissue, while lipolysis is simultaneously induced.

Conclusions: NanoLipo showed many advantages compared to control under blinded and nonblinded conditions. This technology may be promising in facilitating fat removal.

Figure 1.

(A) Heating profiles of tissue specimens for NanoLipo and control pretreatments, measure externally and internally for NanoLipo, and externally only for control. Both NanoLipo internal measurements and control skin surface measurements showed mild heating, while NanoLipo external measurements showed the most heating. (B) After centrifugation, the liberated triglyceride phase accounted for nearly 50% of total lipoaspirated tissue volume for the NanoLipo group (left tube, indicated by the arrow), while almost no liberated triglyceride was observed in the control (right tube). (C) Calcein/ethidium homodimer live/dead assay; tissue fluorescing green from the calcein dye shows that the majority of the tissue is viable, while minimal red staining, indicative of dead cells, was observed.

Figure 2.

NanoLipo procedure results in the removal of visibly more fat, indicated by (A) a clearly visible depressed region within the underlying adipose tissue matching the shape and size of the laser aperture (dotted rectangle). (B) The same feature is not present in the control (saline + laser + liposuction) treated specimen. (C) Proportionally more fibrous tissue is observed in the NanoLipo treated specimen with very few fat lobules remaining, while (D) many fat lobules adhering tightly to the connective tissue membranes are observed for the control specimens. Arrows in Figures 2C and 2D indicate lobules of fat.

Figure 3.

Smoothness within the treatment zone was used as a key marker to distinguish the NanoLipo treated specimen from control specimens under blinded conditions. Digital photographs for one set of blinded experiments showing adipose tissue after liposuction and skin removal are shown. (A) NanoLipo treated specimen was even in appearance and was absent of fat lobules, whereas in (B) large and lumpy fat lobules are clearly visible and can be felt throughout the control specimen. Near the edge of the NanoLipo specimen outside of the treatment zone (below the dotted line in A.), several large fat pearls are clearly visible (arrow).

Figure 4.

Micro computer-aided tomography images of the distribution of infused AuNR solution within adipose tissue compared to noninjected control. (A, B) The transverse views, (C, D) coronal views, and (E, F) sagittal views of injected and noninjected adipose tissue specimens, respectively. The relatively darker spaces represent air, the relatively grey spaces represent fat-rich regions, and the relatively white spaces represent water-rich regions of adipose tissue, such as connective tissue membranes. Infused solution preferentially disperses between and expands into the interstitial spaces between fat pearls (A, C, E), while the interstitial spaces between connective tissue of noninjected adipose tissue specimens remain collapsed in their native state (B, D, F). Scarpa’s fascia can be seen in the transverse and sagittal views as a thicker white line parallel to the skin surface.

Figure 5.

Absence of nitroblue tetrazolium staining (arrows) shows selective thermal damage of connective tissue membranes at the fat pearl level in adipose tissue due to photothermal inactivation of intracellular reductases, and is consistent with the way AuNR solution distributes within iinterstitial spaces of adipose tissue. Specimens were subjected to (A) NanoLipo or (B) control treatment, vertically bisected with a surgical scalpel through the optical exposure axis to isolate thin slices approximately 0.5 cm thick, and stained. Complete staining of the control specimen, as well as staining of the overlying skin and deeper adipose tissue regions in the NanoLipo treated specimen, demonstrates that these tissues were unaffected and that photothermal damage was selectively restricted to the fibrous connective tissue membranes at the pearl level.