Walfre Franco

Hyperthermic injury to adipocyte cells by selective heating of subcutaneous fat with a novel radiofrequency device: feasibility studies.

The main objective of the present study is to demonstrate the feasibility of utilizing a novel non‐invasive radiofrequency (RF) device to induce lethal thermal damage to subcutaneous adipose tissue only by establishing a controlled electric field that heats up fat preferentially.

Radial and temporal variations in surface heat transfer during cryogen spray cooling

Cryogen spray cooling (CSC) is a heat extraction process that protects the epidermis from thermal damage during dermatologic laser surgery. The objective of the present work is to investigate radial and temporal variations in the heat transferred through the surface of a skin phantom during CSC. A fast-response thermal sensor is used to measure surface temperatures every 1 mm across a 16 mm diameter of the sprayed surface of the phantom. An analytical expression based on Fouriers law and Duhamels theorem is used to compute surface heat fluxes from temperature measurements. Results show that radial and temporal variations of the boundary conditions have a strong influence on the homogeneity of heat extraction from the skin phantom. However, there is a subregion of uniform cooling whose size is time dependent. It is also observed that the surface heat flux undergoes a marked dynamic variation, with a maximum heat flux occurring at the centre of the sprayed surface early in the spurt followed by a quick decrease. The study shows that radial and temporal variations of boundary conditions must be taken into account and ideally controlled to guarantee uniform protection during CSC of human skin.

Controlled volumetric heating of subcutaneous adipose tissue using a novel radiofrequency technology

The objective of the present study was to demonstrate the feasibility of varying the size of the heating volume of subcutaneous adipose tissue using a novel radiofrequency (RF) technology that controls the delivered energy distribution on the skin surface.

Review of applications of fluorescence excitation spectroscopy to dermatology

Endogenous molecules that exhibit fluorescence hold the potential to serve as reporters of tissue structure, activity and physiology. Fluorescence excitation spectroscopy is one means to measure and express tissues innate fluorescence. This review focuses on the application of endogenous fluorescence ultraviolet excitation spectroscopy to dermatology.

Fractional Skin Harvesting: Autologous Skin Grafting without Donor-site Morbidity

Background: Conventional autologous skin grafts are associated with significant donor-site morbidity. This study was conducted to determine feasibility, safety, and efficacy of a new strategy for skin grafting based on harvesting small columns of full-thickness skin with minimal donor-site morbidity. Methods: The swine model was used for this study. Hundreds of full-thickness columns of skin tissue (~700 µm diameter) were harvested using a custom-made harvesting device, and then applied directly to excisional skin wounds. Healing in donor and graft sites was evaluated over 3 months by digital photographic measurement of wound size and blinded, computer-aided evaluation of histological features and compared with control wounds that healed by secondary intention or with conventional split-thickness skin grafts (STSG). Results: After harvesting hundreds of skin columns, the donor sites healed rapidly without scarring. These sites reepithelialized within days and were grossly and histologically indistinguishable from normal skin within 7 weeks. By contrast, STSG donor sites required 2 weeks for reepithelialization and retained scar-like characteristics in epidermal and dermal architecture throughout the experiment. Wounds grafted with skin columns resulted in accelerated reepithelialization compared with ungrafted wounds while avoiding the “fish-net” patterning caused by STSG. Conclusion: Full-thickness columns of skin can be harvested in large quantities with negligible long-term donor-site morbidity, and these columns can be applied directly to skin wounds to enhance wound healing.

Fluorescence Excitation Photography of Epidermal Cellular Proliferation

Fluorescence excitation provides the ability to interrogate innate molecules whose radiation emission correlates with specific functional states of tissue.

Sprayable peptide-modified silver nanoparticles as a barrier against bacterial colonization

Sprayable formulations of AgNPs were prepared by exchanging citrate capping agents with LL37-SH peptides. The AgNP@LL37 material was then combined with type I collagen to form a stable film once sprayed. The AgNP@LL37 spray prevented Pseudomonas aeruginosa (P. aeruginosa) proliferation and eradicated a P. aeruginosa biofilm, while being non-toxic for human skin fibroblasts embedded within 3D artificial skin constructs. Finally, no silver infiltration was observed after spraying on a full-thickness skin wound in a mouse model.

UV fluorescence excitation imaging of healing of wounds in skin: Evaluation of wound closure in organ culture model

Molecules native to tissue that fluoresce upon light excitation can serve as reporters of cellular activity and protein structure. In skin, the fluorescence ascribed to tryptophan is a marker of cellular proliferation, whereas the fluorescence ascribed to cross‐links of collagen is a structural marker. In this work, we introduce and demonstrate a simple but robust optical method to image the functional process of epithelialization and the exposed dermal collagen in wound healing of human skin in an organ culture model.

Thermal and elastic response of subcutaneous tissue with different fibrous septa architectures to RF heating: numerical study.

Radiofrequency currents are commonly used in dermatology to treat cutaneous and subcutaneous tissues by heating. The subcutaneous morphology of tissue consists of a fine, collagenous and fibrous septa network enveloping clusters of adipocyte cells. The architecture of this network, namely density and orientation of septa, varies among patients and, furthermore, it correlates with cellulite grading. In this work we study the effect of two clinically relevant fibrous septa architectures on the thermal and elastic response of subcutaneous tissue to the same RF treatment; in particular, we evaluate the thermal damage and thermal stress induced to an intermediate‐ and a high‐density fibrous septa network architecture that correspond to clinical morphologies of 2.5 and 0 cellulite grading, respectively.

Laser-assisted cryosurgery of prostate: numerical study

A new methodology for preventing freezing damage beyond pre-specified boundaries during prostate cryosurgery is proposed herein. It consists of emitting controlled laser irradiation from the urethra, across the wall and into the prostate while conventional cryoprobes freeze the unwanted prostate tissue. The purpose of this methodology is to protect the urethral wall better and confine the desired cryoinjured region more accurately than the current cryosurgery approach. We also explore the potential use of light-absorbing dyes to further enhance the laser light absorption and corresponding heat generation to increase the thickness of the protected region. A finite difference heat diffusion model in polar coordinates with temperature-dependent thermophysical properties simulates the prostate freezing while laser irradiation across the urethral wall is emitted. This approach maintains the temperature of the urethral wall and the adjacent tissue above a pre-specified threshold temperature of -45 degrees C, independent of application time. Temperature contours resulting from prostate cryoablation with (a) conventional constant temperature heating; (b) laser irradiation heating; and (c) laser irradiation heating with pre-injected light-absorbing dye layers indicate that the thickness of the protected region increases in this order, and that the latter two methodologies may be more effective in limiting cryoinjury to a predefined region compared to constant temperature heating. An analysis of laser power requirements and sensibility of laser-assisted cryosurgery (LAC) of prostate is also presented. It is shown that tissue temperature may vary as much as +/-20 degrees C with variations of +/-10% in laser power relative to the nominal power required to maintain the tissue at 37 degrees C. This demonstrates the sensitivity to laser power and the need of an accurate laser power control algorithm.