Film Dressings: An Innovative Approach in Wound Management

Wound management is a crucial aspect of healthcare, as   proper healing prevents infection, reduces complications, and improves patient comfort.[1] A wound is defined as a disruption of the integrity of skin ,mucous membranes, or tissue often resulting from trauma, surgery .Clinically, wounds are categorized as acute (e.g., surgical, traumatic) or chronic (e.g., diabetic foot ulcers, venous leg ulcers, pressure ulcers), with chronic wounds posing a substantial burden on healthcare systems due to delayed healing, susceptibility to infection, and high morbidity rates. [2] In earlier practices, wounds were commonly covered using cotton, gauze, or bandages.[3] Although these materials provide basic protection, they often fail to maintain the ideal wound environment, may adhere to the wound surface, and require frequent replacement, which can slow the healing process.

In complex or chronic wounds when tissue regeneration is impeded and inflammation persist conventional bandages have a limited functional contribution to healing while acting as barriers to external contamination. Because untreated wounds can result in infection, systemic sepsis, extended hospital stays, and higher medical expenses, advanced wound care management is essential. These difficulties demonstrate the inadequacy of conventional wound dressings for more complicated wound types, especially chronic ulcers linked to diabetes or vascular insufficiency, where management is further complicated by prolonged healing times and susceptibility to infection.[4]

Film dressings have become increasingly important among contemporary dressings. These are thin, flexible, transparent polymeric membranes that stick to the skin and let moisture vapour and oxygen through while keeping water and microbes out. Film dressings allow for visual monitoring of the healing process without the need for frequent dressing changes, maintain a moist wound environment, and lower the risk of infection. Additionally, some cutting-edge films are made to transport medicinal substances like growth factors, antimicrobials, or anti-inflammatory medications straight to the wound site.

WOUND MANAGEMENT

The primary goal of wound management is to restore the normal structure and function of the damaged tissue. The wound healing process is a natural physiological reaction to tissue injury that consists of four highly integrated phases: hemostasis, inflammation, proliferation, and remodeling. These phases must occur in a specific sequence, at a specific time, and for a particular duration.

1. Hemostasis: -

The hemostasis phase begins minutes to hours after an injury through a cascade of serine protease activation, resulting in platelet activation. This activation also facilitates the release of growth factors, such as PDGF (platelet-derived growth factor), VEGF (vascular endothelial growth factor), and TGF-α (transforming growth factorα), as well as immune mediators.

PDGF and TGF-β recruit neutrophils and monocytes Furthermore, this leads to the formation of a fibrin clot, which acts as a plug for the wound, preventing blood loss, providing a scaffold for incoming immune cells, and offering protection against bacterial invasion. Releasing molecules such as serotonin that induce localized vasoconstriction Subsequently, platelets aggregate and forming a hemostatic plug.

Fig. No.1 Hemostasis

2. Inflammation: - 

The inflammatory phase, which overlaps with hemostasis, occurs within the first 72 hours after injury. During this phase, humoral and   cellular immune responses are activated to protect the wound from infection. Neutrophils and monocytes infiltrate the wound bed to remove debris and microorganisms. The inflammatory phase is divided into early and late stages. 4 In the early phase, neutrophils dominate, performing phagocytosis of bacteria and damaged tissue.

They also release enzymes, reactive oxygen species, and inflammatory mediators such as TNF-α and interleukins. After completing their function, neutrophils undergo apoptosis within 2–3 days. In the late phase, monocytes migrate to the wound site and differentiate into macrophages. These macrophages clear dead cells and secrete enzymes like matrix metalloproteinases and elastase. They also release growth factors such as PDGF, TGF-α, TGF-β, IGF-1, FGF, IL-1, and IL-6, which promote fibroblast activation and transition to the proliferative phase. A decline in macrophage activity signals the end of the inflammatory phase.

Fig. No.2 Inflammation

3. Proliferation: -

The proliferative phase of wound healing involves several interconnected processes that restore tissue structure and function. It begins on the third day after the injury and lasts approximately two weeks. During this phase, angiogenesis, the generation of granulation tissue, collagen deposition, re-epithelialization, and wound contraction occur. It involves the migration and proliferation of endothelial cells to form new blood vessels.

Granulation tissue formation occurs concurrently with angiogenesis and primarily comprises type III collagen, fibroblasts, and new vessels. proliferation, and synthesis of extracellular matrix components, contributes to tissue restoration.

Fig. No.3 Proliferation

4. Remodeling: -

His final phase begins several weeks after injury and can last up to 1–2 years. Granulation tissue gradually transforms into a mature scar. Type III collagen is replaced by stronger type I collagen, increasing tissue strength. Myofibroblasts, derived from fibroblasts under TGF-β influence, promote wound contraction through smooth muscle actin (SMA) activity and undergo apoptosis after healing. Capillaries decrease, vessels enlarge, and collagen fibers reorganize and cross-link via lysis oxidase, enhancing tensile strength. However, the healed tissue regains only about 80% of its original strength.

Fig. No.4 Remodeling

A SMART AND ADVANCED   STRATEGY FOR WOUND CARE FILMS

The limitations of conventional dressings have driven the development of advanced wound dressing systems designed to actively support the healing environment. Recent years Advancements in wound care technology have led to the development of modern dressing materials that actively support the healing process. Among these, film dressing has emerged as an innovative solution. These transparent, flexible, and adhesive films, which are usually made of polyurethane and related polymers, offer a number of practical benefits, including the ability to facilitate gaseous exchange (the transfer of oxygen and water vapour), form a barrier that protects against contaminants and bacteria, and allow for clinical monitoring of the wound without the need for frequent removal. [5]

In contrast to traditional dressings, film dressings offer a conformable covering appropriate for superficial and low-exudate wounds, as well as low adherence to wound tissue, which reduces damage during dressing changes. They act as secondary coverings for wounds treated by absorbent or bioactive primary dressings as well as primary dressings for mild wounds. These dressings reinforce the idea of moist wound healing, which was first proven by studies showing faster epithelialisation in hydrated environments. It has been demonstrated that keeping the wound surface moist hasten healing in contrast to the development of dry scabs.[6] This regulated setting lowers the possibility of microbial contamination and encourages quicker tissue regeneration. They are especially well suited for superficial and low-exudate wounds because they allow water vapour transport while preventing bacterial invasion. [7] During dressing changes, their flexible and non-adherent qualities reduce pain and shield freshly produced tissue. Modern film dressings are a useful and cutting-edge choice in modern wound care because of their ability to include therapeutic ingredients, which further improves localised treatment and healing efficiency. Localised therapeutic agents are a useful and cutting-edge choice in modern wound management since they further improve localised treatment and healing efficiency. Clinical data indicates that sophisticated dressings may enhance the rate at which chronic wounds heal when compared to traditional dressings. Meta-analyses indicate superiority of advanced dressings in achieving complete wound closure, although evidence varies by wound type and study quality. Thus, film dressing. represent a significant advancement in wound care technology combining protection comfort and healing efficacy in a single easy -to-use system. [8]

Fig. No.5 Ideal properties of Film

MATERIAL UESD IN FILM DRESSING

The selection of materials plays a critical role in determining the physicochemical, mechanical, and biological performance of film dressings. Materials used for film dressings must exhibit biocompatibility, non-toxicity, flexibility, appropriate permeability, and the ability to support wound healing. Based on origin, these materials are broadly classified into natural polymers and synthetic polymers.

Table No.- 01 Polymers used in film dressings

Fig. No.6 Absorption Mechanism of Film

5. TYPES OF FILMS

1. Transparent Film: -

Transparent films are usually made from polyurethane, polyethylene, or polyvinyl chloride (PVC). These materials form a thin, elastic, and clear membrane that adheres to the skin using a hypoallergenic adhesive. Transparent Allows visualization of the wound without removal. Semi-permeable Permits oxygen and water vapor exchange but prevents bacterial invasion. Elastic and conformable: Fits easily over joints and contoured surfaces. Forms a thin protective layer preventing bacteria and dirt entry. Allows oxygen and CO? exchange but blocks water and microbes. Retains wound moisture, promotes epithelial growth and autolytic debridement. It acts as a barrier to contaminants and supports autolytic debridement by retaining endogenous enzymes within the wound bed. Allows wound observation without removing dressing. Promotes moist wound healing & Prevents contamination by bacteria and water. Thin, flexible, and comfortable. can stay in place for up to 7 days. Not suitable for heavily exuding wounds. Difficult to use on irregular wounds.

Examples are: Tegaderm ®, Bioclusive ®, Polyskin ®. 

2. Hydrogel: -

Hydrogel films are water-based polymer networks that can hold large amounts of water while maintaining a soft, elastic structure. They are used as moist wound dressings that cool, soothe, and promote healing. Hydrogel films are made from hydrophilic polymers such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), carboxymethylcellulose (CMC), or polyacrylamide, containing 70–90% water. Soft, elastic, and transparent. Capable of absorbing wound exudate while maintaining moisture. Cooling effect due to high water content.                                 

Maintains hydration at the wound surface, promoting epithelialization. Provides soothing and pain-relieving effect due to high water content. Absorbs exudates moderately and keeps the wound clean. Allow oxygen to pass but prevents bacterial contamination. Maintain a moist and cool, soothing effect for burns. Non-adherent and easy to remove. Poor mechanical strength. Require secondary dressing for fixation.

Burns and scalds. Pressure ulcers and necrotic wounds.      

Radiation-damaged skin. Examples are: AquaClear ®, Intrasite ® Gel Sheet, Derma-Gel®, Nu-Gel®.

3. Hydrocolloid Film: -

Hydrocolloid films are modern occlusive or semi-occlusive wound dressings that promote healing by maintaining a moist environment, protecting the wound, and facilitating autolytic debridement (natural removal of dead tissue)

Hydrocolloid films contain gel-forming agents like gelatin, pectin, and carboxymethylcellulose (CMC) combined with an adhesive layer and a polyurethane backing film. Occlusive and adhesive to the skin. Swells and forms a gel when in contact with wound exudate. Self-healing and conformable. When exudate interacts with the hydrocolloid layer, a moist gel forms, protecting granulating tissue and stimulating autolytic debridement. Maintains optimal moisture. Waterproof and bacterial barrier. Encourages granulation tissue formation. Not suitable for infected wounds (occlusive nature). Can leave residue upon removal. Pressure ulcers, burns, and donor sites.

Light to moderately exuding wounds. Venous leg ulcers.

Examples are: DuoDERM®, Comfeel®, Hydrocoll®, Tegasorb®.

4. Bioactive films: -

Bioactive films are an advanced form of wound dressing designed not only to protect the wound but also to actively promote the healing process. Natural Polymers: - Chitosan, Alginate, Gelatin. Synthetic Polymers: - Polyvinyl alcohol (PVA), Polycaprolactone (PCL)Polyethylene glycol (PEG), Polylactic acid (PLA). Composite Blends: - Chitosan–PVA, Alginate–PCL, Collagen–PCL (used to balance biological and mechanical properties). Plasticizers: - Used to improve flexibility and film-forming properties. Examples: Glycerol, Propylene glycol, Sorbitol. Bioactive Agents: - The key component responsible for therapeutic action Antimicrobial Agent, Antioxidants & Anti-inflammatory Compounds, Growth Factors. Crosslinking Agents: - Enhance film strength and regulate degradation. Examples: Glutaraldehyde, Calcium chloride. maintains a moist environment at the wound site, essential for epithelialization. The bioactive agents are gradually released from the film matrix to the wound bed. Growth factors stimulate fibroblast migration, collagen synthesis, and angiogenesis. Provides active healing through drug or bioactive release. Maintains optimal moisture balance for cell growth. Can be biodegradable, avoiding painful removal. Suitable for chronic, diabetic, and infected wounds. Complex preparation process. Stability issues with sensitive bioactive agents. Limited shelf life due to degradation of natural ingredients. Chronic non healing wounds, Burn wound, Infected wounds.

FORMULATION AND MANUFACTURING METHOD OF FILM DRESSINGS

Film dressings' mechanical strength, thickness, permeability, drug release behaviour, and biological efficacy are all greatly influenced by the formulation and manufacturing process used. The kind of polymer, the intended wound application, and the addition of active agents all influence the choice of a suitable technique. Solvent casting, hot-melt extrusion, electrospinning, and cross-linking processes are the most frequently reported methods.

1. Solvent Casting Method: -

The most popular and straightforward approach for creating polymeric film dressings, especially in a lab setting, is solvent casting. [9] This technique involves dissolving or dispersing polymers in an appropriate solvent system (organic or aqueous), then adding plasticisers and active agents. [10,11] Solvent evaporation and film formation result from pouring the homogenous solution into a mould or Petri dish and letting it dry at a regulated temperature. [12] This method works well with hydrophilic synthetic polymers like PVA and PVP as well as natural polymers such chitosan, alginate, gelatin, and cellulose derivatives.[13] Solvent casting is frequently used to create drug-loaded film dressings because it allows for easy formulation optimisation and uniform drug distribution inside the polymer matrix. [14]

Fig. No.7 Solvent Casting Method

2. Hot-Melt Extrusion (HME): -

Hot melt extrusion (HME) is a continuous, solvent-free manufacturing process that is frequently used in pharmaceutical formulation to improve solubility, bioavailability, and controlled drug delivery in wound treatment systems such bioactive scaffolds and antimicrobial films. To create a homogenous physical mixture, the active pharmaceutical ingredient (API) is first precisely weighed and combined with appropriate thermoplastic polymers (such as polyvinylpyrrolidone, polyethylene oxide, ethyl cellulose, or polycaprolactone) and functional excipients. The selection of polymers is based on glass transition temperature (Tg), melting point, and drug–polymer miscibility to guarantee molecular dispersion. [15,16]

A single-screw or twin-screw extruder's hopper receives the prepared blend, which is then passed via a heated barrel divided into numerous zones with varying temperatures. [17,18] Under regulated shear stress and heat energy, the material melts, mixes, kneads, and homogenises as it moves along the revolving screws, promoting the production of amorphous solid dispersion or drug solubilisation. [19,20]

Depending on the intended wound dressing application, the molten mass is then driven through a die with a predetermined shape to produce extrudates in the form of films, rods, filaments, or implants. [21,22] To stabilise the drug-polymer matrix and harden the structure, the extrudate is cooled using conveyor systems or air cooling after leaving the die.

The solidified extrudates are then gathered and put through downstream processing, such as cutting, milling, or shaping into transdermal films, implanted devices, or wound dressings. Mechanical strength, drug content homogeneity, and in vitro release behaviour are next characterised. [23] Solvent-free processing, enhanced content consistency, scalability, and the capacity to create controlled or sustained medication release systems appropriate for advanced wound care are some benefits of the HME process. [24]

Fig. No.8 Hot Melt Extrusion Method

3. Electrospinning Method: -

In order to create bioactive nanofibrous dressings that resemble the extracellular matrix (ECM), electrospinning is a flexible nanofabrication process that is frequently used in wound care. To create a homogenous spinning solution, a suitable biocompatible polymer, such as polyvinyl alcohol (PVA), polycaprolactone (PCL), chitosan, or Gelatin is first dissolved in a suitable solvent. Therapeutic agents, such as antibiotics, growth factors, or anti-inflammatory compounds, are then added. Viscosity, conductivity, surface tension, and polymer concentration are important factors that affect fibre morphology and spinnability. [25,26] After that, the prepared solution is put into a syringe with a metallic needle and placed on a syringe pump. During processing, a regulated flow rate guarantees steady and continuous jet formation.

[27,28] Subsequently, a high-voltage power supply (typically 5–30 kV) is applied between the needle and a grounded collector, generating electrostatic forces that overcome surface tension and produce a Taylor cone followed by the ejection of a charged polymer jet. [29,30] As the jet travels toward the collector, it undergoes rapid elongation and whipping instability, accompanied by solvent evaporation, resulting in the formation of ultrafine nanofibers with high surface area. [31,32] These nanofibers are deposited onto a stationary or rotating grounded collector to form a nonwoven nanofibrous mat, with fiber diameter and morphology influenced by process parameters such as applied voltage, flow rate, needle-to-collector distance, temperature, and humidity.

The resulting nanofibrous scaffold exhibits high porosity, excellent oxygen permeability, moisture retention capacity, and the ability to provide sustained drug release, thereby making electro spun membranes highly suitable for advanced wound dressing applications. [33,34]

Fig. No.9 Electrospinning Method