Mueller Matrix Analysis of Collagen and Gelatin Containing Samples Towards More Objective Skin Tissue Diagnostics

Abstract

Electrospun polycaprolactone:gelatin (PCL:GT) fibre scaffolds are widely employed in the field of tissue implants. Here, the orientation of fibres plays an important role in regard to implantation due to the impact on the mechanical properties. Likewise, the orientation of collagen fibres in skin tissue is relevant for dermatology. State-of-the-art fibre orientation measurement methods like electron microscopy are time consuming and destructive. In this work, we demonstrate polarimetry as a non-invasive approach and evaluate its potential by measuring the Mueller matrix (MM) of gelatin and collagen containing samples as simple skin tissue phantoms. We demonstrate that it is possible to determine the orientation of PCL:GT fibre scaffolds within one MM measurement. Furthermore, we determine the structural orientation in collagen film samples. Currently, the diagnosis of skin diseases is often performed by image analysis or histopathology respectively, which are either subjective or invasive. The method presented, here, provides an interesting alternative approach for such investigations. Our findings indicate that the orientation of collagen fibres within skin lesions might be detectable by MM measurements in the future, which is of interest for skin diagnostics, and will be further investigated during the next step.

In Situ Characterization of Polycaprolactone Fiber Response to Quasi-Static Tensile Loading in Scanning Electron Microscopy

“…The relative velocity, at the surface of the collector, is of special interest for this study. As shown by Fricke et al (2019), an increase in relative collector velocity leads to an increased degree of fiber orientation [ 9 , 14 ].…”

“…The used electrospinning device (see Figure 1 ) was assembled according to Fricke et al (2019) and is composed of a syringe pump, a syringe, polyethylene tubing, a blunt cannula, and an electric motor driving the rotating drum collector [ 6 , 9 , 14 ].…”

“…The samples were manufactured out of a solution of polycaprolactone (PCL, 80 kDa, Sigma-Aldrich Chemistry Corporate, St. Louis, MO, US) in 2,2,2-TFE (99.8%, abcr GmbH, Karlsruhe, Germany) with a concentration of 17% ( w / v ) (170 mg/mL). The solution was prepared according to Fricke et al (2019) [ 9 , 14 ]. The samples were fabricated with a 250 mm tip-to-collector distance, voltage of 20 kV, relative collector velocities of 2 m/s and 8 m/s, and a process duration of 120 min ( Figure 1 ).…”

“…All values located outside of the 1.5 × IQR are individually displayed as dots. These were defined as outliers, with regard to the IQR, but do not necessarily have to be considered as extreme values [ 9 ].…”

“…With this in mind, polymers are commonly used materials in TE [ 6 , 7 , 8 ]. In fact, the fabrication of fiber scaffolds by electrospinning (see Figure 1 ) has produced great results for several different combinations of polymers and solvents (e.g., polycaprolactone (PCL) in trifluoroethanol (TFE) or polyethylene oxide in water) [ 9 , 10 , 11 ]. The resulting fibers inherit diameters between a few hundred nanometers and a few microns [ 12 , 13 ].…”