Infection Control in Wound Care


3 good reasons to consider using electrospun fibers in your next wound dressing design.

When the body’s immune defences are overwhelmed and it is unable to effectively cope with normal bacterial growth on open wounds, infection occurs. Infections are responsible for slowing down healing, causing wound odour, and often increases pain or discomfort.

  • 20% of all hospital-acquired infections (HAI) in Europe in 2011/2012 were surgical site infections (SSI).1
  • Up to 30% of all wounds become infected.2
  • Roughly 75% of the deaths associated with burn wounds covering more than 40% of the body surface are due to infections caused by bacterial contamination during the wound healing process.3

These statistics highlight the importance of improving control over infections during the healing of wounds for both the patient and the health care provider.

Wound dressings generally have to perform several functions to be effective:

– Act as a barrier to prevent further harm and intrusion of infectious pathogens
– Prevent excessive moisture that can cause maceration of healthy peripheral tissue,
– Prevent drying out of the wound, which slows healing and can lead to cracking and pain,
– Allow the exchange of gases (oxygen, CO2, and water vapor), and
– Have antibacterial capability.

Conventional wound dressing materials like gauzes, foams and films have limited ability to deal with all of these requirements simultaneously. By harnessing and tailoring the properties of electrospun fiber materials, we are able to design smart, highly potent, infection controlling wound dressings that can perform most, if not all, of the functions mentioned above.

In this post, we highlight 3 reasons to consider using electrospun fiber based materials when designing a new wound dressing product. For a broader overview, please download this free white paper: Electrospun fibers – A new dawn for advanced wound care.


1. Their microporous structure make them breathable barriers

The low diameters of electrospun nanofibers lead to a microporous structure of electrospun fiber webs, which can be tailored specifically so that they have pores smaller than bacteria like MRSA. In other words, the structure acts as a barrier that can restrict foreign bodies from entering a vulnerable area via a “sieve” effect. This minimizes the risk of further infection from the external environment and simultaneously creates a physical barrier against further trauma.4

Electrospun fiber dressings not only maintain the barriers to infection, but the added advantage of the micropores serves as a barrier that is also breathable. Electrospun fiber dressings have the ability to maintain the appropriate oxygen and moisture levels with the continuous exchange of gasses and fluids between a vulnerable area and the external environment – a necessity to help wounds heal. So while foreign bodies are kept out, proper healing can still to occur.5,6


2. You can build active ingredients into the fibers

Inflammation is a physiological response to wounding and is a necessary part of the wound healing process. Excessive inflammation can however provide an ideal environment for bacterial infiltration and proliferation. This makes prolonged inflammation, typical of chronic wounds, an important target for therapeutic interventions.

The systemic administration of antibiotics remains one of the more commonly used treatments for infections. However, the development of antibiotic resistant strains over time are a concern, and so is the possibility of systemic toxicity due to the high concentrations needed to treat heavily infected wounds effectively. The use of topical antimicrobial agents like iodine (cadexomer iodine and povidone iodine), silver (silver sulfadiazine) and polyhexamethylene biguanide (PHMB) with conventional dressings, provide an alternative to typically used systemic treatment procedures. Unfortunately the poor dosage control of antimicrobials when using topical agents with these conventional dressings can lead to the poisoning of the wound.

The controlled, targeted and topical release of antimicrobials is expected to be a more effective approach, since the minimum inhibitory concentration needed to kill all bacteria can be achieved in a highly localised position, over a number of days. This minimises the risk of severely harmful effects to the body. Incorporating antimicrobials into electrospun fiber materials, can aid in the controlled release of, for instance, antibiotics into the wound.

The electrospinning process can generally be performed at room temperature and uses mild, safe, solvent systems for the dissolution of the fiber forming polymer(s) and other additives like antimicrobials, antibiotics, analgesics, anti-inflammatories and many more.

The ability to select polymers with different wetting, swelling and biodegradation profiles makes it possible to tailor drug release profiles from these fibers. For example, it is possible to tailor the release of an active additive to have an initial burst release followed by a slow, sustained release over a number of days. These materials are ideal to use as topical delivery systems because they lead to higher concentrations of the antibiotic at the wound bed during infection, while simultaneously preventing systemic toxicity coupled with systemic antibiotic administration.7,8

Case studies highlighting the compositional and functional flexibility of electrospun fibers:

  1. An antibiotic (cefoxitin sodium) was incorporated into an electrospun fibrous material, and initial studies showed a burst release of 70% of the drug with little to no sustained release observed thereafter. Subsequently, instead of using a single polymer, an additional amphiphilic polymer was incorporated into the spin solution. This resulted in the encapsulation of cefoxitin sodium in the hydrophilic part of the amphiphilic polymer with the encapsulation leading to a smaller burst release of cefoxitin sodium (50%) initially, followed by a sustained release of 27% over a one week period. Slightly modifying the electrospinning solution formulation resulted in the prolonged release of the antibiotic from the electrospun fiber scaffold.9
  2. Ciprofloxacin, a hydrophilic antibiotic, was incorporated into a water-soluble electrospun fibrous scaffold, where the burst release behaviour was observed within 2 minutes. When ciprofloxacin was incorporated into a hydrophobic fiber web, it resulted in a sustained release of the drug (80%) over a 10 day period. Similar behaviour was observed for other hydrophilic antibiotics such as ampicillin, metronidazole and cefazolin.10 Sandwiching of drugs between shell layers of PLGA/collagen where PLGA/vancomycin, gentamicin and lidocaine formed the core layer, has also been investigated. This resulted in antibacterial effects being observed against E. coli and S. aureus for up to 24 days.11

3. They can reduce the number of dressing changes

A large proportion of hospital-acquired infections are attributed to how medical devices are used, and it is important to design devices and develop usage protocols that minimise the risk of spreading infection. This also applies to wound dressing design and dressing change protocols. Every time a wound dressing is changed, the risk of infection increases as the wound is uncovered every time. Furthermore, the removal of the dressing can potentially facilitate the spread of infection from the wound to the external environment. Reducing the number of dressing changes reduces the risk of infection and has the additional benefits like reduced costs, improved patient comfort, and potentially accelerated wound healing.

The combined breathability and wound moisture management capabilities of electrospun fiber dressings, reduces the required frequency of dressing changes. Electrospun fiber dressings can be tailored to be either hydrophilic or hydrophobic, resulting in dressings that can either absorb large amounts of exudate, due to high surface area hydrophilic material, or allow for exudate to pass through the primary dressing material (hydrophobic material) to be absorbed by a secondary dressing. This eliminates the need for excessive dressing changes, usually needed for exudate control in highly exudating wounds.

Slow, sustained release of antimicrobials from electrospun fiber materials over extended periods (sometimes from 3-4 weeks and upward), can also negate the need for frequent dressing changes when treating infected wounds. This allows the wound to stay closed for longer periods, minimising further infection risk, and facilitating the healing process.

It is also important to consider patient comfort when selecting dressings, especially when dressing changes are not as frequent. The nano-scaled smoothness and lack of protruding fibers in electrospun fiber dressings, result in extreme softness which increases comfort when compared to conventional dressings.

Find out how you can harness the benefits and power of electrospun fibers for infection control in advanced wound care.

Contact SNC today

References:

  1. European Centre for Disease Prevention and Control. Point prevalence survey of healthcare associated infections and antimicrobial use in European acute care hospitals. 2011-2012. Available at: https://ecdc.europa.eu/sites/portal/files/media/en/publications/Publications/healthcare-associated-infections-antimicrobial-use-PPS.pdf [Last accessed March 2018]
  2. Lindholm, C., Ostomy Wound Manage. 2003, 49, 4-7
  3. Church, D. et al., Clin. Microbiol. Rev. 2006, 19, 403-434
  4. Espíndola-González, A. et al., Int. J. Mol. Sci. 2011, 12, 1908-1920
  5. Joshi, M. et al., J. Nanosci. Nanotechnol. 2014, 14, 853-867
  6. Zahedi, P. et al., Polym. Adv. Technol. 2010, 21, 77-95
  7. Katti, D. S. et al., J. Biomed. Mater. Res. B Appl. Biomater. 2004, 70, 286-296
  8. Jannesari, M. et al., Int. J. Nanomed. 2011, 6, 993-1003
  9. Kim, K. et al., J. Control. Release. 2004, 98, 47-56
  10. Li, H. et al., Int. J. Pharm. 2017, 517, 135-147
  11. Chen, D. W. et al., Int. J. Pharm. 2012, 430, 335-341


Dr. Hennie Kotzé
Dr. Hennie Kotzé
Hennie Kotzé (PhD) – Senior Scientist, SNC