*2.1.2 Material source*

As the name suggests, biologic skin substitutes are made using biological materials from human or animal sources. Synthetic material refer to non-biological materials engineered in a laboratory to replace or support regeneration of one or more components of normal skin structure. Biosynthetic skin substitutes are those made using a combination of biological and synthetic materials. Skin substitutes with biological components may allow replication of a more natural neodermal structure generated by native extracellular matrix and can allow excellent re-epithelialisation, although staged procedures are often necessary due to slow vascularisation. Synthetic skin substitutes offer increased control over scaffold composition and less propensity to loss due to cross-species antigenicity or infective complications [16] as compared with materials with biological origins, following integration with the burn wounds to which they applied.

### *2.1.3 Layering*

Single layered skin substitutes replace either the epidermal (e.g., Suprathel) or dermal (e.g., Matriderm) component of skin, the latter of which requires autologous skin grafting to complete the epidermal reconstruction. Bilayered dermal substitutes are designed to replace or replicate both dermal and epidermal layers during their application whether this is on a temporary basis (e.g., Biobrane) or a permanent basis (e.g., Integra, BTM). In the latter case a two-stage approach is required whereby the impermeable pseudo-epidermal layer is removed or 'delaminated' prior to autologous skin graft application for definitive wound closure. A two staged strategy is particularly advantageous in major burn patients by allowing autologous skin harvest to be deferred until such time as the patient has reached a point of physiological stabilisation, resolution of inhalational injury or other concomitant traumatic injury [12] and optimisation of cardiac or other medical comorbidities [17]. This approach also facilitates re-epithelialisation of donor site harvest for repeated harvest in major burn patients who may have a paucity of donor site due to their total body surface area of burn, while permitting mobilisation during the integration phase [18].
