Biomedical Engineering Reference
In-Depth Information
optimal conditions for cell proliferation and differentiation, makes fibrin an
attractive candidate as a carrier matrix for the delivery of cells to the wound bed.
This attractiveness as a wound repair material is further enhanced as fibrin
degrades completely without causing any immunogenic response (Ronfard
et al
.,
1991).
The principle ways in which fibrin can be used to deliver cells to the wound bed
are as follows:
1
Apply the thrombin and calcium solution to the wound bed and spray the fibrin
component containing cells onto the wound. On contact the solutions mix and
polymerise. The use of this sprayed technique is covered elsewhere in this
book.
2
Mix the thrombin and fibrin fractions with cells and apply to the wound bed as
the solution polymerises.
3
Generate fibrin sheets
in vitro
seeded with keratinocytes and apply these as
sheets to the wound bed.
This review examines the use of fibrin delivered to the wound as sheet material.
9.2.1
Use of fibrin sheets for restoration of the epidermis
The first reported use of fibrin as a delivery vehicle for keratinocytes was by
Hunyadi
et al
. (1987) for the treatment of chronic wounds. In this study keratinocytes
were isolated from split thickness skin by trypsin digestion and suspended in the
fibrinogen component of Beriplast
®
fibrin sealant. This was combined with the
thrombin and calcium components on the wound bed to form a fibrin matrix
containing keratinocytes. This method avoided the use of cultured keratinocytes
and although limited data are presented, demonstrated increased epithelialisation.
A further study (Hunyadi
et al
., 1988) described the treatment of chronic wounds
in 20 patients with fibrin and keratinocytes of which 16 healed well when
compared with five patients treated with fibrin alone, where no healing occurred.
This idea was further developed by Ronfard
et al
. (1991) who used keratinocytes
cultured with irradiated 3T3 mouse fibroblast cells according to the methods of
Rheinwald and Green (1975). At the final subculture, cells were seeded into Petri
dishes which had been pre-coated with fibrin glue matrix. The fibrin glue matrix
was prepared by combining fibrin solution in the presence of aprotinin and
thrombin. This mixture was spread evenly over the base of the dish and allowed to
polymerise into a homologous fibrin matrix. Proteolytic degradation of the matrix
was prevented by the high concentration of aprotinin. Cells were cultured for either
2 days, forming colonies of 10-20 cells or for 10 days after which time they formed
a confluent sheet 1-4 cells thick. The fibrin matrices, populated with keratinocytes,
were then transferred to the wound. It appears from the data presented in this study
that a better take rate occurred when the fibrin matrix was oriented with keratinocytes
facing the wound and the fibrin outward. Sub-confluent keratinocytes, rather than
