Wound dressings

Ideal wound dressings

  • keep the proper moisture of the wound,
  • transport gasses,
  • absorb exudates,
  • protect from pathogens,
  • prevent from necrosis,
  • are easy to replace,
  • are biodegradable,
  • biocompatible,
  • elastic,
  • non-toxic,
  • relieve pain,
  • are cost-effective,
  • and environment-friendly.1

Furthermore, different injuries require different dressings. The goal of personalized medicine is producing wound dressing designed to each patient.

Materials in wound dressings

Semipermeable film from both bio-based and synthetic materials are the common wound dressings, alongside with sponges, foams, hydrogels, nanofibers and decellularized tissues. All these materials form a scaffold for skin cells, support their viability, migration, and proliferation.

Wound dressings very often consist of several layers. The inner layers absorb exudates and carry pharmaceutics, while the outer layers protect from pathogens and drying.

In the Table 1, there are the most common materials used for wound dressings. The trend is to use natural materials as they are more biocompatible. Local allergic reactions to synthetic polymers or adhesives are common. Residual synthetic particles from wound dressings remaining in the wound can also cause complications. That’s why biodegradable polymers are preferred.2

 

Material

Features

Synthetic polymers

Polyurethan

Polyurethan is a transparent film, permeable for gasses, but not for pathogens, keeps moisture and is easily removable. Polyurethan is not suitable for wet wound with lot of exudate. The advantages are the possibility to monitor the wound without dressing replacement and low cost.2

Silicone

Protects from hypertrophic and keloid scars formation.3

Proteins

Collagen

The most abundant animal protein, the main structure of the extracellular matrix. Collgaen I is the most common in tissue engineering. Animal collagen can cause allergic reaction, thus bacterial collagen is preferred in biomedicine. Collagen supports natural adhesion, proliferation, and migration of cells as well as moderate immune response. Not optimal mechanic properties and fast degradation.4, 5

Gelatin

Gelatin is produced by collagen hydrolysis. It is biodegradable and biocompatible, but allergenic as much as collagen. Gelatin absorbs moisture and forms gel. Gelatin is more stable than collagen, better for nanofiber formation and cost-efficient.4, 6

Keratin

Water-insoluble fibrous protein produced by epithelial animal cells. It is the main structural protein of wool, horns, down, hair, and nails. The production from animal biomass is complicated.5

Fibroin

Water-insoluble fibrous protein from silk. It is of high mechanical resistance and supports cell adhesion.5

Fibronectin

Human glycoprotein, supports cell adhesion, biodegrades quickly.4

Polysacharides

Hyaluronic acid

One of the main components of connective tissue. It absorbs high abouts of water, forms hydrogel – suitable for wet wounds and controlled-release systems.5

Chitosan

Produced by chitin deacetylation. Chitin forms exoskeletons of crustaceans and insects. It is biocompatible, biodegradable, with antimicrobial and hemostatic properties.4, 5

Alginate

Biodegradable polysaccharide from brown algae. It is non-toxic, non-inflammatory, hydrophile, absorbs water – gels formation, high porosity, cost-effective. Suitable for wet wounds.5

Pectin

Plant polysaccharide, which absorbs water and forms gel.

Cellulose

The most abundant biopolymer on this planet – the main structural polymer for plant cell walls. Traditional gauze is made of cellulose, its main advantage is the very low price, but it does not transport gasses perfectly, does not protect from infection and is not easily removeable. In tissue engineering, cellulose acetate and carboxymethylcellulose are the most common derivatives.

Table 1 – Materials used in wound dressings

Besides the wound dressings, systemic therapy is also part of the treatment – mostly represented by antibiotics. Other local therapy includes physical approaches (dead tissue elimination, compression, hyperbaric oxygen therapy, etc.) or pharmacologic (antiseptics, antibiotics, natural oils, aloe vera, honey, etc.).

PHAs nanofibers in wound dressings

PHAs fit perfectly into biomedicine applications due to their full biocompatibility and biodegradability. However, their material properties must be adjusted – PHAs are brittle, little elastic and hydrophobic. This is the reason for searching the best composite material. Table 2 comprises recent literature on PHAs composites suitable for electrospinning and tissue engineering applications.

Surface modifications of PHAs enhance cells adhesion – treatment of PHAs surface with plasma is the effective choice. 7-9

Nanofiber scaffold from P3HB and chitosan supported fibroblasts adhesion and proliferation10, similarly as P3HB/gelatin6 and PHBV/collagen11 composites. These composites were also tested as wound dressings.12, 13

Nanofibers can also serve as drug carriers – they can bind pharmaceuticals (e.g. antibiotics) and slowly release them.14

Group

Mixture

References

PHA mixtures

PHB/PHBV

15-17

PHBHH/P34HB

18-21

P3HB/P3HO

22, 23

PHA/polysacharides

PHA/chitosan

14, 24, 25

PHB/carrageenan

26

PHB/glucosamine sulphate

27

PHB/pectin

28

PHB/acetyl cellulose

29, 30

PHBV/cellulose nanocrystals

31

PHA/proteins

PHA/collagen

11, 13, 32-35

PHA/gelatin

12, 36-40

PHA/fibroin

41, 42

PHA/keratin

43, 44

P34HB/zein

45

P3HB/poly-β-alanine

46

PHB/laminin

47

PHA/inorganic compounds

PHA/carbon nanotubes

48, 49

PHA/graphene

50, 51

PHA/hydroxyapatite

52-56

Other composites

PHB/PLCL

57

PHA/PCL

58-61

PHA/PLA

62-64

PHA/PEO (PEG)

65-68

PHBHH/chitosan/PCL

69

PHA/graphene/Ag nanoparticles

70

Table 2: Composites of PHAs tested for nanofiber production in tissue engineering. Zein is protein from corn. Poly-β-alanine is a synthetic protein. Laminin is a glycoprotein of epithelial tissue lamina. Poly-e-caprolactone (PCL) is biodegradable hydrophobic plastics. Poly-lactis acid (PLA) is biodegradable, bio-based, and biocompatible polymer. PEG/PEO/POE is polymer of ethylene oxide.

References

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