BIOPRINTING FOR SKIN - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 273

CHAPTER

13

BIOPRINTING FOR SKIN

Lothar Koch 1, * , Stefanie Michael 2, * , Kerstin Reimers 2 , Peter M. Vogt 2 and Boris Chichkov 1
1 Nanotechnology Department, Laser Zentrum Hannover e.V., Hollerithallee 8, Hannover, Germany
2 Department of Plastic, Hand- and Reconstructive Surgery, Hannover Medical School,
Hannover, Germany
* These authors contributed equally

13.1 SKIN, SKIN SUBSTITUTES, POSSIBLE APPLICATIONS
FOR PRINTED SKIN
13.1.1 SKIN: FUNCTION AND STRUCTURE
13.1.1.1 Function
The skin is the largest organ, covering the whole body and having a surface area of 1.5-2 m 2 and
a weight of 3-10 kg. Due to its specific structure, it represents a barrier between the external en-
vironment and the inside of the person, thereby serving as a highly effective means of protection
against environmental harm, such as chemical, mechanical, and thermal influences, irradiation, or
pathogens.
The first protection against pathogens is achieved by the acid mantle of the skin, with a pH of
5.5-5.7. It is complemented by antimicrobial peptides (defensins) of the innate immune system and
several cell types of the adaptive immune system (e.g. Langerhans cells, macrophages, leucocytes,
plasma cells, and mast cells). Furthermore, the apical surface of the skin is inhabited by various
bacteria and fungi, which constitute the normal skin flora and contribute to its protective function.
As commensals, they protect their habitat—and thereby us—against pathogenic microorganisms
( Michael, 2013c ).
Apart from its protective function against external influences, the skin is crucial for the maintenance
of temperature and water balance homeostasis, avoiding conditions such as dehydration or hypother-
mia. In case of large burn injuries, the barrier function of the skin is destroyed and liquid and protein
loss may result in a life- threatening condition.
Moreover, the skin acts as a sensory organ that can detect pain, contact, pressure, vibration,
itching, and temperature. This contributes to our protection, but also to our general perception of the
environment by complementing visual or auditory perceptions.
On the social level, the skin is essential in representation, communication, and manifestation of
current mood. It is therefore important for daily living, especially for communication and interac-
tion among individuals. In this context, people's skin color may indicate their habits and preferences
(e.g. having deeply tanned skin due to regular engagement in outdoor activities or frequent visits to a