Biochemical Engineering CEN 551. Instructor: Dr. Christine Kelly Chapter 15: Medical Applications of Bioprocess Engineering. Schedule. Thursday, April 1: Dr. Hasenwinkel (hand out homework). Tuesday, April 6: Finish chapter 15.
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Instructor: Dr. Christine Kelly
Chapter 15: Medical Applications of Bioprocess Engineering
April 20: Meka, Chapeaux, Chang, Sayut
April 22: Pasenello, Prantil, Lu, Menon
April 27 Price, Reis
“The application of principles and methods of engineering and life sciences toward fundamental understanding of structure-function relationships in normal and pathological mammalian tissues and the development of biological substitutes to restore, maintain or improve tissue function” (Whitaker Foundation “Tissue engineering”).
The term “artificial skin” was first introduced by JF Burke in 1987, and used to designate a bilayered dermal- epidermal replacementdevised by Burke and Yannas.
Now it can be applied to several on bilayeredproducts that have been engineered for permanent replacementof lost human dermis and that provide either a temporary orpotentially permanent epidermis.
Autograft (Split-thickness skin grafts)
The best material for wound closure, when practical, is the patient’s own skin (autograft). Split-thickness skin grafts (epidermis plus a thin layer of dermis) harvested from the patient’s uninjured skin is essential for closure.
The two artificial skins that currently exist have sought to meet these constraints in two different ways:
Figure 1.Integra, the bilaminate artificial skin of Burke & Yannas, applied to a full-thickness skin defect.
Figure 2.Integra 1 week after application to a full-thickness skin defect.
Figure 3. Second-stage Integra grafting. At 2 weeks after Integra application, the process of neodermis formation is complete, the temporary silicone epidermal analog has been removed.
Figure 4. Second-stage Integra grafting. A meshed ultrathin autograft has been applied. The epidermal cells of the autograft proliferate and attach to the underlying neodermis, forming a durable and confluent epithelium.
as a Pre-engineered Tissue Substitute
In contrast to the materials science and engineering approachof Burke & Yannas, Bell and colleagues took theapproach of reconstituting dermal injury by applying a preformedtissue.
The resulting product is described as a dermal equivalent, which, unlike Integra, relies on living cells in tissue culture to organize the collagen network.
Inorder to provide definitive wound closure, an Apligraf-likeproduct would have to be constructed from a patient’sown fibroblasts and keratinocytes. The production of a patient-specificproduct (i.e. with fibroblasts and keratinocytes taken fromthe patient) would take several weeks, during which the woundwould have to be covered with a temporary skin substitute.
Deramagraft-TC is a two-layer synthetic material designed as a temporary skin substitute. The outer layer is a silicone polymer, and the inner layer is a nylon mesh.
Scanning electron micrograph of human dermal fibroblasts grown on a three-dimensional nylon scaffold (Dermagraft-TC).
Several new products available
In the future, a combination of materials science and tissueculture techniques is likely to produce a skin substitute thatcan function as an autograft for both dermis and epidermis.
Althoughexpensive, the new approach has demonstrated the feasibility ofcombining Integratechnology with that of tissue engineeringand may be the forerunner of 21st-century skinreplacement.
Most peoples “Achilles heel” is not their achilles heel but their knees. The knee is not that simple, it is actually an interwoven system of ligaments, cartilage, and muscle.
The knee in flexion (bent)
The Swedish Method of Articular Cartilage Replacement
The procedure is used on patients who suffer from defects in the articular cartilage on the bottom of the femur.
Articular cartilage (chondral) defect before removing damaged articular cartilage.
Photograph of an Arthroscopic Surgery
Arthroscopic Surgery Instrumentation
Articular cartilage (surface) defect (circled in red) after removing damaged articular cartilage.
Articular cartilage (surface) defect after periosteum patch is sewn in place.
5 differential equations
Decay of virus
Inhibition by proteoglycans
with human or pig liver cells
have been examined.