Can Zinc Oxide Have An Impact On Wound Healing?
As the complexity and price of wound care materials seems to be reaching mind-numbing proportions, choosing the right product for your patients seems to be getting harder instead of easier. However, taking into account cost, effectiveness and availability, one would be hard pressed to find a product better than zinc oxide. Although it is most commonly associated with diaper rash ointments and Unna boot wraps, zinc oxide has remained relatively underused in podiatry offices and in wound care centers. Considering that more than 300 enzymes are dependent on zinc for activity such as matrix metalloproteinases (MMPs), zinc oxide (which averages between $2 and $3 a tube) should be a product that is used more in treating wounds. Despite a very long history, zinc oxide is a uniquely modern material. Having a wide array of properties, it continues to increase in value in many of the ever-widening fields of science and technology: physics, chemistry, biology, electronics, industry, agriculture and wound healing. The favorable effects of zinc oxide (ZnO) were discovered almost accidentally during animal studies in the 1950s. Since that time, researchers have vigorously studied zinc with regard to its biochemical impact on healing. Not only does zinc play a role in metalloenzyme activity, it is also involved in nucleic acid and protein metabolism. In fact, zinc protrusions were recently found within large quantities in transcription factors that interact with the promoter region of DNA before a segment is transcribed into RNA coding for growth factors.1 What The Literature Reveals The beneficial effects of zinc in wound healing have been reported to explain the retarded wound repair response seen in zinc-deficient patients along with the normalization of the wound healing mechanisms with zinc therapy.2 In animal studies, zinc deficiency decreased the tensile strength of surgical wounds. This could also be explained by the fact that 20 percent of the body’s zinc is stored in the skin and is concentrated in the epithelium.3 In contrast to oral zinc, topical zinc appears to be beneficial regardless of zinc status. The increased demand for zinc during the wound healing process is satisfied for prolonged periods by applying zinc oxide to the wound. When zinc oxide is delivered, zinc ions stay within the wound fluid for an extended period of time, which results in constant wound tissue zinc levels.4 The ultimate effect of zinc oxide seems to be in the acceleration of re-epithelialization within the wound, yet most of the mechanisms are unknown. What has been clearly demonstrated, however, is that zinc oxide does have a positive impact on the wound. In a 1991 study, researchers found that using zinc oxide increased the degradation of collagen in necrotic wounds.5 In another recent study, zinc oxide was found to promote epithelialization of full thickness skin wounds by the activation of zinc-dependent MMPs, which facilitate keratinocyte migration. The study also demonstrated that zinc oxide augmented endogenous expression of insulin-like growth factor (IGF-1), which is fundamental in the production of granulation tissue.1 In a randomized, double-blind study of the efficacy of locally applied zinc oxide on the healing of leg ulcers, 37 geriatric patients (19 with arterial and 18 with venous leg ulcers) were treated with either a gauze compress medicated with zinc oxide or an identical compress without zinc oxide. The treatment was assessed from ulcer size measurements and the presence or absence of granulation, and ulcer debridement over a period of eight weeks. The zinc-treated patients (83 percent success rate) responded significantly better than the placebo-treated patients. Researchers found that infections and the deterioration of ulcers were less common in zinc oxide treated patients.6 In another animal study, reepithelialization was enhanced when zinc oxide was applied topically on partial-thickness wound in pigs with normal zinc status. The inflammatory reaction was diminished in zinc-treated wounds except when researchers applied a high zinc sulfate concentration.7 Researchers also assessed bacterial growth in full-thickness wounds and demonstrated a reduced rate of growth with topical zinc oxide but not in hyperglycemic diabetic rats.