Biological Dressing can be conceptualized as a form of Speciality Dressing that aids in treating wounds and injuries of different degrees. To elucidate 'biologic dressings' in a detailed spectrum, one needs to be familiar with the concepts of Autografts, xenografts, and allografts. A brief of the three looks like:

Autografts – they are derived from the patient’s skin

Allografts – they are derived from someone else’s skin

Xenografts – they are derived from animal’s hide

Let us start expounding ‘biological dressings’ with allografts. An allograft is cadaver skin that has been donated. It is usually cryopreserved and when required, is available at the tissue banks.

How allografts were used as biologic dressings?

Earlier, allografts were used to cover large burn wounds as well as treating chronic wounds like ulcers. They are used by medical professionals as a matrix for the growth of granulation tissue. The cadaveric skin is placed carefully after preparing the wound bed. An antimicrobial dressing is applied over the graft and a compression dressing is also applied to reduce edema. Generally, the allograft is debrided within a week. If they are not removed, the wound might exhibit an added inflammation. The grafting may be reapplied, or some other form of dressing could be alternatively used. But debriding after the initial week is necessary, else, the patient starts rejecting the grafts.

Allografts are effective in controlling pain, reducing infection risks, promote neovascularization, cutting down the healing time. In short, these biologic dressings efficiently bathe the wound with essential cytokines and thus functions as a ‘growth factor’.

Biologic dressings in the form of autografts

As you already know, first degree or minor burns heal naturally; this is because the body's mechanism replaces the damaged skin cells. Second degree or deeper burns require special treatments like skin grafting for quick healing. Autograft is the procedure where the skin is taken from the unaffected part of the same victim (who will undergo the grafting) and placed on the wound site.

What is the procedure of autografting?

The injured tissues are removed, and a donor site is selected from where the healthy skin needs to be collected. Before placing the grafted skin on the cleaned wound site, the donor skin area is harvested. Since the wound needs to heal, the grafted portion is kept immobile for a few days so that the blood vessels begin to build up again.

Autografting is again of two kinds – sheet grafting and meshed skin grafting. The former involves spreading the piece of skin grafted from the donor area upon the burnt space and its edges are stapled. The donor skin is slightly larger in size to leave space for shrinkage after harvesting. This is applicable in the case of a limited burnt portion of the body.

Contrarily, when things turn the other way round, that is, the total area of open wounds is large and there is not enough donor skin available, the latter is meshed (running through a machine such that the skin stretches in order to cover a larger area).

Xenografts as a form of biologic dressings

In a brief, xenografting is using animal skin (mostly pig skin) on wound sites for the purpose of healing. A xenograft is a rather lesser expensive alternative and has been there in practice since the 16th century! Although the practice of xenografting can be executed using the skin of any species like dogs, cats, rats, sheep, cows, etc. yet, pigs are most commonly in use. It is therefore termed as porcine xenografts; they are readily available and comparatively cheaper.

Porcine xenografts effectively protect wounds from physical trauma, any bacterial infection, and pain. The wound at first should be debrided after which the graft adheres. If any infection persists in the site, antibiotics are initiated before the graft is applied. This dressing aids in heat and moisture retention in the wound site.

While xenograft dressing is being discussed, a few things need to be reasonably mentioned:

• Xenografts could be used in conjunction with meshed allografts

• Xenografting should be followed by compression therapy too. It reduces the chances of edema.

• They need to be inspected as well as changed weekly such that the healing is quick; it also ensures that rejection does not occur!

Another modern and upcoming concept of biologic dressings is: Collagen Dressing

What is collagen dressing in a gist?

Collagen dressings are wound healing products that are also obtained from animal sources. They are mainly drawn from cows, horses, and pigs. They essentially aid in promoting the growth of new collagen in the wound site. In certain cases, they help maintain the appropriate temperature as well as a proper microenvironment for a safe and speedy recovery of the wound.

The different forms that collagen dressings are available in are gels, powders, freeze-dried-sheets, and even pastes. Mostly, these dressings include antimicrobial agents that effectively contain the spread of potential infections, if any.

Collagen dressings address wounds that have a partial thickness, necrotic wounds, and even second-degree burns. However, depending on the wound's nature, a collagen dressing should be inspected and changed in about a week to yield effective results.

While we are discussing biologic dressings, the list goes on since this one’s a broad spectrum! Calcium Alginate dressing is yet another form – it’s highly absorbent, biodegradable that maintains a moist microenvironment in and around the wound. It promotes healing and formation of granulation tissue also. So, they are typically applied to full-thickness burns, diabetic wounds, wounds that involve major blood veins and chronic ulcers too.

Thanks to medical breakthroughs, there are important advancements in biological dressings that can efficaciously maintain microbial control and speed up wound maturation in the process.