A new cell‐free bandage‐type artificial skin for cutaneous wounds

Engineered skin substitutes are widely used in skin wound management. However, no currently available products satisfy all the criteria of usability in emergency situations, easy handling, and minimal scar formation. To overcome these shortcomings, we designed a cell‐free bandage‐type artificial skin, named “VitriBand” (VB), using adhesive film dressing, silicone‐coated polyethylene terephthalate film, and collagen xerogel membrane defined as a dried collagen vitrigel membrane without free water. We analyzed its advantages over in‐line products by comparing VB with hydrocolloid dressing and collagen sponge. For evaluation, mice inflicted with full‐thickness skin defects were treated with VB, hydrocolloid dressing, and collagen sponge. A plastic film group treated only with adhesive film dressing and silicone‐coated polyethylene terephthalate film, and a no treatment group were also compared. VB promoted epithelization while inhibiting the emergence of myofibroblasts and inflammation in the regenerating tissue more effectively than the plastic film, hydrocolloid dressing, and collagen sponge products. We have succeeded in establishing a cell‐free bandage‐type artificial skin that could serve as a promising first‐line medical biomaterial for emergency treatment of skin injuries in various medical situations.     

A new finite element approach for near real‐time simulation of light propagation in locally advanced head and neck tumors

Background and Objectives

Several clinical studies suggest that interstitial photodynamic therapy (I‐PDT) may benefit patients with locally advanced head and neck cancer (LAHNC). For I‐PDT, the therapeutic light is delivered through optical fibers inserted into the target tumor. The complex anatomy of the head and neck requires careful planning of fiber insertions. Often the fibers' location and tumor optical properties may vary from the original plan therefore pretreatment planning needs near real‐time updating to account for any changes. The purpose of this work was to develop a finite element analysis (FEA) approach for near real‐time simulation of light propagation in LAHNC.

Methods

Our previously developed FEA for modeling light propagation in skin tissue was modified to simulate light propagation from interstitial optical fibers. The modified model was validated by comparing the calculations with measurements in a phantom mimicking tumor optical properties. We investigated the impact of mesh element size and growth rate on the computation time, and defined optimal settings for the FEA. We demonstrated how the optimized FEA can be used for simulating light propagation in two cases of LAHNC amenable to I‐PDT, as proof‐of‐concept.

Results

The modified FEA was in agreement with the measurements (P = 0.0271). The optimal maximum mesh size and growth rate were 0.005–0.02 m and 2–2.5 m/m, respectively. Using these settings the computation time for simulating light propagation in LAHNC was reduced from 25.9 to 3.7 minutes in one case, and 10.1 to 4 minutes in another case. There were minor differences (1.62%, 1.13%) between the radiant exposures calculated with either mesh in both cases.

Conclusions

Our FEA approach can be used to model light propagation from diffused optical fibers in complex heterogeneous geometries representing LAHNC. There is a range of maximum element size (MES) and maximum element growth rate (MEGR) that can be used to minimize the computation time of the FEA to 4 minutes. Lasers Surg. Med. 47:60–67, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.