Biochemical, Biophysical and Mechanical Characterization of Decellularized Dermal Implants

Abstract

Allografts have been used in a variety of applications to augment as well as replace tissues throughout the body. A number of steps are involved in selection, harvesting, processing and testing of dermal allografts. Grafts can be obtained that are: free of antibodies to viruses and low in viral titers. Cellular material can be eliminated from the tissue and the product becomes almost exclusively a collagen fiber network. The purpose of this paper is to examine the changes in collagen structure and properties that occur during processing of decellularized dermis. The results indicate that collagen fiber swelling occurs during processing although the product preserves the native collagen banding pattern at the fibrillar structural level. Fiber swelling and decreased collagen deformability of processed dermis, may lead to stress concentration at the implant-tissue interface and up-regulation of mechanotransduction. This may lead to premature mechanical failure due to creation of a chronic inflammatory condition at the implant-tissue interface. It is suggested that all dermal allografts be oriented such that Langer's lines of the implant match those of the host tissue, and that wound closure by suturing be done under conditions that preserve the normal tension in skin in order to minimize implant-interfacial failure.

Comparative “virtual biopsies” of normal skin and skin lesions using vibrational optical coherence tomography

“…Vibrational optical coherence tomography (VOCT) is a new technique developed in the Department of Pathology at Robert Wood Johnson Medical School, Rutgers University. It uses near infrared light and audible sound applied transversely to the tissue surface to image and measure the resonant frequency of tissues . The resonant frequency is directly related to the tissue stiffness measured using conventional uniaxial tensile testing as described previously …”

“…OCT cross‐sectional images were obtained using an OQ Labscope (Lumedica Inc) and a laboratory spectral‐domain optical coherence tomography device (SD‐OCT) operating in the scanning mode …”

“…Transverse sample displacement was generated by placing a speaker next to the skin or under the excised lesion to be studied by spectral‐domain optical coherence tomography (SD‐OCT), a non‐contact, interferometric technique as discussed previously . The SD‐OCT system uses a fiber‐coupled superluminescent diode light source with an 810 nm center wavelength and 100 nm bandwidth (full‐width at half maximum) as described previously …”

“…Identification of tissue margins and tissue stiffness non‐invasively in conjunction with enhanced imaging techniques has the potential to facilitate detection of abnormal skin lesions and lead to early removal. We have developed at technique termed vibrational optical coherence tomography (VOCT) to image skin in three dimensions and measure the stiffness simultaneously, non‐invasively and non‐destructively to provide a “virtual biopsy” of skin and skin lesions …”

“…Using VOCT to image and analyze the biomechanical properties of tissues non‐invasively and non‐destructively, it is possible to get a “virtual biopsy” of normal skin and abnormal skin lesions . Correlating these measurements with in vitro calibration data can be used to interpret mechanical measurements made in vivo .…”