Honey was used in traditional medicine to treat wounds until the advent of modern medicine. The rising global antibiotic resistance has forced the development of novel therapies as alternatives to combat infections. Consequently, honey is experiencing a resurgence in evaluation for antimicrobial and wound healing applications. A range of both Gram-positive and Gram-negative bacteria, including antibiotic-resistant strains and biofilms, are inhibited by honey. Furthermore, susceptibility to antibiotics can be restored when used synergistically with honey. Honey’s antimicrobial activity also includes antifungal and antiviral properties, and in most varieties of honey, its activity is attributed to the enzymatic generation of hydrogen peroxide, a reactive oxygen species. Non-peroxide factors include low water activity, acidity, phenolic content, defensin-1, and methylglyoxal (Leptospermum honeys). Honey has also been widely explored as a tissue-regenerative agent. It can contribute to all stages of wound healing, and thus has been used in direct application and in dressings. The difficulty of the sustained delivery of honey’s active ingredients to the wound site has driven the development of tissue engineering approaches (e.g., electrospinning and hydrogels).
Although used traditionally in wound treatments and other illnesses, the advent of modern medicine and antibiotics has reduced its medical usage. However, the widespread use of antibiotics has led to a significant rise in antibiotic-resistant infections globally, which by 2050 could lead to 10 million deaths per year if new treatments are not developed [2–4]. Subsequently, the discovery and development of new antibiotics is a global priority. This has initiated a re-evaluation of the clinical use of honey in conjunction with a growing awareness and understanding of the material properties, composition, and mechanisms of the antimicrobial action of honey.
Honey is produced by eight species of bee within the genus Apis, which represents a small fraction of the approximately 15,000 species of bee. However, the world population of western honeybee (Apis mellifera), widespread across the world, is decreasing due to several factors, including, but not limited to: climate change, the use of pesticides in agriculture, disruptions to their specialised gut microbiome, and the prevalence of the Deformed Wing Virus associated with the ectoparasitic Varroa destructor mite [5–10].
Honeybees produce honey through a complex process beginning with the collection of floral nectar (floral or blossom honey) or sugar-rich secretions from insects (honeydew honey) as raw materials. These are stored and processed in their hives. The bees dehydrate, add their own compounds to, and modify the nectar through the secretion of specific enzymes to break down sugars. The modified nectar matures and develops into honey. Honey is a viscous and concentrated aqueous sugar solution generally comprising fructose (~40%), glucose (~30%), sucrose (~5%), small quantities of disaccharides (e.g., maltose, isomaltose, and turanose), and water (~20%). It is worth noting that these percentages are only representative and can substantially differ due to botanical sources, nectars, and seasons [11]. In addition, a variety of proteins, amino acids, minerals, enzymes (e.g., glucose oxidase and invertase), vitamins, and polyphenols are also present [12–14]. The composition and properties of honey depend on the surrounding environment of the hive and the metabolic activity of the bees. For example, the collection of nectar can either be predominately monofloral (single species of plant) or multifloral (multiple species of plant) which can give rise to unique properties and distinctive tastes.
2
2) [16–22]. The presence of the enzyme, glucose oxidase (GOx), is fundamental to produce H
2
2
2
2 species [20,22–26]. The enzyme presents no activity in raw honey, due to a lack of free water, to initiate the peroxide-dependent antimicrobial mechanism the honey needs to be diluted. Other important antimicrobial features responsible for the non-peroxide activity of honey include low water content (osmotic effect), low pH (acidic environment), phenolic compounds, bee defensin-1 (Def-1), and methylglyoxal (MGO) (in Leptospermum-derived manuka honey).
Honey is mainly used as a topical application on wounds where the antibacterial properties of honey are essential. The high viscosity of honey provides an effective hydrated barrier between the wound site and external environment. A variety of wound types have been treated with honey, such as burns, trauma, and chronic wounds [27–29]. However, the wound healing process is a complex multi-factorial cascade of events that if interrupted by infection or specific disease states (e.g., diabetes) can lead to the development of chronic wounds, recurrent infections, amputation/limb salvage, and life-threatening conditions. Growing antibiotic resistance further complicates the problem and can lead to preventable deaths from the infection of wound sites and sepsis. Subsequently, there is a critical need for new treatment options. Natural products such as honey can be part of the solution and is a promising candidate to create novel antimicrobial wound dressings.
Honey has been used in combination with traditional wound dressings but presents some limitations, such as being absorbed by the dressing, poor penetration into the wound site, and short-term antimicrobial action. The manufacturers of impregnated dressings are striving to improve their delivery mechanism. However, the limitations of traditional delivery methods of honey to the wound site have highlighted the need for new innovative routes of delivery, with methodologies such as electrospun fibres and hydrogels actively being explored [29–33]. This can enable the honey to remain in direct contact with the wound bed and provide a persistent and long-term release of antimicrobial agents. Furthermore, the presence of reactive oxygen species (ROS) such as H
2
2 has been shown to promote wound healing by encouraging cellular repair processes and tissue regeneration [20,34]. Thus, the use of honey, honey-derived, and honey-inspired products in tissue engineering applications combined with other biomaterials may enable its use in a variety of other clinical situations outside wound care, where the combination of antimicrobial properties and tissue regeneration is desirable.
The antimicrobial activity of honey is multi-factorial but has historically been poorly understood. However, within the past century, honey’s antimicrobial properties have been identified and can be broadly attributed to peroxide and non-peroxide activities (Figure 1), with a range of compounds contributing to these activities.
Figure 1.
A
2
2
2
2
B
C
D
E
F
2
2 via a non-enzymatic pathway.
Figure 2.
2
2, def-1 (Swissmodel, P17722) , MGO (Leptospermum honeys only), flavonoids, phenolic acids, and sugars.
Figure 3.
2
2
Product |
Manufacturer |
Description |
Indications |
Mechanism of Action |
Ref. |
Clinical Evidence |
Activon® Manuka Honey Tube |
Advancis Medical |
100% medical-grade manuka honey |
Any wound type but especially sloughy, necrotic, and malodorous wounds, including: pressure ulcers, leg ulcers, diabetic ulcers, surgical wounds, burns, graft sites, infected wounds, cavity wounds and sinuses |
Debrides necrotic tissue; can be used in dressings or directly into cavities. |
[154] |
Inhibition of in vitro formation of clinically important Gram-positive bacteria biofilms [155]. Blistering and cellulitis on a type 2 diabetic patient; paediatric burn; foot ulceration; grade 5 sacral wound [154] |
Activon® Tulle |
Advancis Medical |
Knitted viscose mesh dressing impregnated with 100% manuka honey |
Granulating or shallow wounds, good when debriding or de-sloughing small areas of necrotic or sloughy tissue |
Creates a moist healing environment, eliminates wound odour, and provides antibacterial action |
[154] |
Overgranulated grade 3 and 4 pressure ulcers; extensive leg cellulitis; venous ulcer; chronic wound infections; necrotic foot [154] |
Algivon® Plus |
Advancis Medical |
Reinforced alginate dressing impregnated with 100% manuka honey |
Pressure, leg and diabetic ulcers, surgical wounds, burns, graft sites and infected wounds. Ideal for wetter wounds |
Absorbs exudate. Debrides, removes slough, and reduces bacterial load |
[154] |
Chronic wounds [156]; burn wound management [157] |
Algivon® Plus Ribbon |
Advancis Medical |
Reinforced alginate ribbon impregnated with 100% manuka honey |
Cavities, sinuses, pressure ulcers, leg ulcers, diabetic ulcers, surgical wounds, burns, graft sites, and infected wounds |
Absorb exudates. Debrides, removes slough, and reduces bacterial load |
[154] |
Autoamputation of fingertip necrosis [158] |
Aurum® ostomy bags |
Welland Medical Ltd. |
Medical-grade manuka honey added to the hydrocolloid |
Stoma care |
Kills bacteria, suppresses inflammation, and stimulates the growth of cells to promote healthy skin around the stoma |
[159] |
Pyoderma gangrenosum around ileostomy [160] |
L-Mesitran® Border |
Aspen Medical Europe Ltd. |
Combined hydrogel and honey (30%) pad on a strong fixation layer |
Chronic wounds, such as: pressure ulcers; superficial and partial-thickness burns; venous, arterial, and diabetic ulcers. |
Exudate absorption. Donates moisture to rehydrate dry tissue. Antibacterial properties. Helps to maintain a moist wound environment |
[161] |
Paediatric minor burns and scalds [162] |
L-Mesitran® Hydro |
Aspen Medical Europe Ltd. |
Sterile, semi-permeable hydrogel dressing containing 30% honey with vitamin C and E, as well as an acrylic polymer gel and water, with a polyurethane film backing |
Low to moderate exuding wounds, including: chronic wounds (pressure ulcers, venous and diabetic ulcers), superficial and acute wounds (cuts, abrasions and donor sites), superficial and partial-thickness burns (first- and second-degree), fungating wounds, acute wounds, e.g., donor sites, surgical wounds, cuts and abrasions |
Donates moisture to rehydrate dry tissue. Antibacterial properties. Helps to maintain a moist wound environment |
[161] |
Paediatric minor burns and scalds [162]. Fungating wounds [163] |
L-Mesitran® Ointment |
Aspen Medical Europe Ltd. |
Ointment with 48% medical-grade honey, medical-grade hypoallergenic lanolin, oils, and vitamins |
Superficial, acute, and chronic wounds. Superficial and partial-thickness burns. Fungating wounds (to help deodorise and debride). Colonised acute wounds and (postoperative) surgical wounds |
Aids debridement and reduce bacterial colonisation |
[161] |
Skin tears; irritation and inflammation [163] |
ManukaDress IG |
Medicareplus International |
Wound dressing made with 100% Leptospermum scoparium sterile honey from New Zealand. Non-adherent impregnated gauze |
Leg and pressure ulcers, first- and second-degree burns, diabetic foot ulcers, surgical and trauma wounds |
Osmotic activity that promotes autolytic debridement and helps maintain a moist wound environment |
[164] |
Burn management [165]. Difficult-to-debride wounds [166]. Necrotic pressure ulcer; recurrent venous leg ulceration [167] |
Medihoney® Antibacterial Honey |
Derma Sciences—Comvita |
100% sterilised medical-grade manuka honey |
All types of wounds with low to moderate exudate, including: deep, sinus, necrotic, infected, surgic and malodorous wounds® |
Creates an antibacterial environment (MGO). Autolytic debridement on sloughy and necrotic tissue. Removes malodour. Provides a moist environment. |
[168] |
Wound healing [169]; prevention of catheter-associated infections in haemodialysis patients [170] |
Medihoney® Apinate |
Derma Sciences—Comvita |
Calcium alginate dressing impregnated with 100% medical-grade manuka honey |
Moderately to heavily exuding wounds such as: diabetic foot ulcers, leg ulcers, pressure ulcers (partial- and full-thickness), first- and second-degree partial-thickness burns, donor sites and traumatic or surgical wounds. |
Promotes a moisture-balanced environment. Osmotic potential draws fluid through the wound to the surface. Low pH of 3.5–4.5. |
[171] |
Venous leg ulcers [172] |
Medihoney® Barrier Cream |
Derma Sciences—Comvita |
Barrier cream containing 30% medical-grade manuka honey |
Use to protect skin from breakdown (e.g., skin damaged by irradiation treatment or in wet areas due to incontinence). Additionally, to prevent damage caused by shear and friction |
Maintains skin moisture and . |
[173] |
Treatment for intertrigo in large skin folds [174] |
Medihoney® Antibacterial Wound Gel™ |
Derma Sciences—Comvita |
Antibacterial wound gel: 80% medical-grade manuka honey with natural waxes and oils |
Surface wounds with low to moderate exudate and partial- and full-thickness wounds, including burns, cuts, grazes, and eczema wounds |
Creates a moist, low-pH environment. Cleans the wound through osmotic effect. Reduces the risk of infection (MGO) |
[175] |
Reduction in incidence of wound infection after microvascular free tissue reconstruction [176] |
SurgihoneyRO™ |
Matoke Holdings Ltd. |
Antimicrobial wound gel utilising bioengineered honey to deliver Reactive Oxygen® (RO™) |
Infected, chronic (diabetic foot, pressure, and leg ulcers) and acute (surgical, traumatic and abrasions wounds, cuts, burns, donor and recipient sites) wounds |
Controlled release of hydrogen peroxide release for antimicrobial activity. Promotes debridement and new tissue growth |
[177] |
Prevention of caesarean |
2
O2 production, osmotic effect, polyphenols, etc.) and by acting as a physical barrier to the wound site has been extensively explored [16,17,27,28,33,61,70,71,182]. Honey’s antimicrobial properties are crucial for the body’s response to tissue damage. Protein-digesting enzymes produced by bacteria are harmful to tissues and are detrimental to the growth factors and extracellular matrix (ECM) produced by the body as it attempts to stimulate tissue regeneration [16,183,184]. Moreover, the reduction in oxygen availability, due to bacteria consumption, compromises tissue growth [185]. Thus, the elimination of bacteria within the wound site can promote tissue regeneration.
production, osmotic effect, polyphenols, etc.) and by acting as a physical barrier to the wound site has been extensively explored [16][17][27][28][33][61][70][71][150]. Honey’s antimicrobial properties are crucial for the body’s response to tissue damage. Protein-digesting enzymes produced by bacteria are harmful to tissues and are detrimental to the growth factors and extracellular matrix (ECM) produced by the body as it attempts to stimulate tissue regeneration [16][151][152]. Moreover, the reduction in oxygen availability, due to bacteria consumption, compromises tissue growth [153]. Thus, the elimination of bacteria within the wound site can promote tissue regeneration.In addition, honey also has properties that promote the regeneration of damaged tissue and wound healing. These properties are multi-factorial and associated with key aspects of the material such as moisture, pH, sugar content, ROS generation, and the anti-inflammatory effect. All of these aspects contribute to the four stages of the wound healing process: haemostasis (blood clotting), inflammation, proliferation/epithelialisation, and tissue remodelling (Figure 4).
In addition, honey also has properties that promote the regeneration of damaged tissue and wound healing. These properties are multi-factorial and associated with key aspects of the material such as moisture, pH, sugar content, ROS generation, and the anti-inflammatory effect. All of these aspects contribute to the four stages of the wound healing process: haemostasis (blood clotting), inflammation, proliferation/epithelialisation, and tissue remodelling.
Figure 4. Key factors of honey that contribute to wound healing across all four healing phases. Created with BioRender.com ( 23 February 2022).
Moisture: Although honey has a low water activity (‘free’ water), it provides a moist environment to the wound bed. This moist environment effectively provides a barrier that prevents eschar formation (dead tissue) and mitigates dermal necrosis, often observed in wounds exposed to air. The importance of moisture for wound healing has been widely demonstrated. Winter et al. [186] reported that epithelisation occurs faster, and a scab is avoided on skin wounds that are kept moist under a dressing, in contrast to wounds exposed to air. Svensjo et al. [187] further supported this claim and showed that granulation tissue develops faster in moist conditions, when compared to dry, and even wet conditions. Moreover, the moist wound surface enhances the migration of epidermal cells, as opposed to migration under the scab. An additional benefit of applying honey is the osmotic effect and subsequent drawing of water and lymph to the wound environment, which aids the oxygenation and nutrition of damaged tissue [27]. Furthermore, the creation of a mixture of diluted honey and drawn lymph under the dressing prevents it from adhering to the wound bed, minimising the risk of tearing newly formed tissue when changing the dressing [16,27].
: Although honey has a low water activity (‘free’ water), it provides a moist environment to the wound bed. This moist environment effectively provides a barrier that prevents eschar formation (dead tissue) and mitigates dermal necrosis, often observed in wounds exposed to air. The importance of moisture for wound healing has been widely demonstrated. Winter et al. [154] reported that epithelisation occurs faster, and a scab is avoided on skin wounds that are kept moist under a dressing, in contrast to wounds exposed to air. Svensjo et al. [155] further supported this claim and showed that granulation tissue develops faster in moist conditions, when compared to dry, and even wet conditions. Moreover, the moist wound surface enhances the migration of epidermal cells, as opposed to migration under the scab. An additional benefit of applying honey is the osmotic effect and subsequent drawing of water and lymph to the wound environment, which aids the oxygenation and nutrition of damaged tissue [27]. Furthermore, the creation of a mixture of diluted honey and drawn lymph under the dressing prevents it from adhering to the wound bed, minimising the risk of tearing newly formed tissue when changing the dressing [16][27].pH and sugar content: The high sugar content contributes to the high osmolarity of honey and has been suggested to provide localised nutrition to the wound site [188]. The application of honey provides a low pH environment, which has been shown to promote epithelialisation and wound closure [189]. This low pH also may reduce the activity of proteases and limit ECM removal [190]. Moreover, this acidification promotes oxygen dissociation from haemoglobin, the Bohr effect, which results in improved tissue oxygenation [189]. However, studies have also shown that acidic conditions can prevent wound closure and re-epithelialisation [191,192]. However, the sustained and relatively low pH levels in these studies may not be applicable when using honey-based products.
pH and sugar content: The high sugar content contributes to the high osmolarity of honey and has been suggested to provide localised nutrition to the wound site [156]. The application of honey provides a low pH environment, which has been shown to promote epithelialisation and wound closure [157]. This low pH also may reduce the activity of proteases and limit ECM removal [158]. Moreover, this acidification promotes oxygen dissociation from haemoglobin, the Bohr effect, which results in improved tissue oxygenation [157]. However, studies have also shown that acidic conditions can prevent wound closure and re-epithelialisation [159][160]. However, the sustained and relatively low pH levels in these studies may not be applicable when using honey-based products. Reactive oxygen species: Historically, the production of ROS in cells was seen as a consequence of an anaerobic environment. Moreover, ROS such as H2
O2 have been classed as harmful and responsible for molecular damage such as DNA mutation and protein oxidation. Hence, it was believed that it was imperative for cells to eliminate these oxidising species [193].
have been classed as harmful and responsible for molecular damage such as DNA mutation and protein oxidation. Hence, it was believed that it was imperative for cells to eliminate these oxidising species [161].However, a more important and complex role for ROS in biological functions such as wound healing and growth regulation has been demonstrated [20,194]. The production of H
However, a more important and complex role for ROS in biological functions such as wound healing and growth regulation has been demonstrated [20][162]. The production of H2
O2 is induced when cells are exposed to epidermal growth factor. The ROS produced activates signalling pathways that lead to cell proliferation and differentiation. Furthermore, a clear correlation between the increase in ROS production and increase in mitogenic rate has been identified [194,195]. Furthermore, Love et al. [34] demonstrated that there is a continuous release of H
is induced when cells are exposed to epidermal growth factor. The ROS produced activates signalling pathways that lead to cell proliferation and differentiation. Furthermore, a clear correlation between the increase in ROS production and increase in mitogenic rate has been identified [162][163]. Furthermore, Love et al. [34] demonstrated that there is a continuous release of H2
O2
during tail regeneration in Xenopus tadpoles with amputated tails. This showed that injury-induced ROS production is a crucial regulator of tissue regeneration. Subsequently, the role of H2
O2
generation in honey is a crucial aspect of its potential use in tissue regeneration applications. ROS levels influence the different stages of wound healing [20]. For example, H2
O2 released from honey has been shown to stimulate the proliferation of fibroblasts when used in a time- and dose-dependent manner [196]. However, the authors also show that prolonged exposure to high concentrations of H
released from honey has been shown to stimulate the proliferation of fibroblasts when used in a time- and dose-dependent manner [164]. However, the researchers also show that prolonged exposure to high concentrations of H2
O2 can exhibit a cytotoxic effect. Additionally, honey’s phenolic content and its antioxidant properties can counteract this toxic effect, rendering protection to cells and enhancing their growth [196,197]. Furthermore, honey has the potential to supply the levels of H
can exhibit a cytotoxic effect. Additionally, honey’s phenolic content and its antioxidant properties can counteract this toxic effect, rendering protection to cells and enhancing their growth [164][165]. Furthermore, honey has the potential to supply the levels of H2
O2 required for the Wnt signalling pathway, which is widely implicated in regenerative processes [34,193,194]. ROS can aid in tissue regeneration through the activation of neutrophil protease [198,199]. This enzyme lays inactive inside neutrophil granules until stimulated by the inactivation of its inhibitor. This required inhibitor inactivation occurs as a result of ROS oxidation, hence releasing neutrophil protease to carry out the proteolytic removal of damaged wound tissue, which can potentially simplify debridement in chronic wounds. The regulation of matrix metalloproteinases (MMPs), crucial to the healing process in chronic wounds, can be influenced by honey [200–204]. ROS in skin wounds have been shown to promote the activation of nuclear factor erythroid derived 2-like 3 (Nrf2), which, in turn, increased the activity of MMPs in fibroblasts [205]. Both the up- and downregulation of MMPs in keratinocytes have been observed when cultured with honey and honey-derived flavonoids, which provides contradictory conclusions [202,203]. The use of different honey types may contribute to the discrepancies, and the amount of ROS generated has not been adequately quantified. ROS may be involved in the regulation of MMPs; however, further research is required.
required for the Wnt signalling pathway, which is widely implicated in regenerative processes [34][161][162]. ROS can aid in tissue regeneration through the activation of neutrophil protease [166][167]. This enzyme lays inactive inside neutrophil granules until stimulated by the inactivation of its inhibitor. This required inhibitor inactivation occurs as a result of ROS oxidation, hence releasing neutrophil protease to carry out the proteolytic removal of damaged wound tissue, which can potentially simplify debridement in chronic wounds. The regulation of matrix metalloproteinases (MMPs), crucial to the healing process in chronic wounds, can be influenced by honey [168][169][170][171][172]. ROS in skin wounds have been shown to promote the activation of nuclear factor erythroid derived 2-like 3 (Nrf2), which, in turn, increased the activity of MMPs in fibroblasts [173]. Both the up- and downregulation of MMPs in keratinocytes have been observed when cultured with honey and honey-derived flavonoids, which provides contradictory conclusions [170][171]. The use of different honey types may contribute to the discrepancies, and the amount of ROS generated has not been adequately quantified. ROS may be involved in the regulation of MMPs; however, further research is required. The H2
O2 released from honey to the wound site will influence multiple wound healing pathways and have complex effects on aspects of cellular behaviour, including proliferation, signalling, metabolism, and migration. Maintaining a low level of ROS is likely key to promoting tissue regeneration and wound healing, as the high and excessive production of ROS can lead to oxidative stress and impaired wound healing [206].
released from honey to the wound site will influence multiple wound healing pathways and have complex effects on aspects of cellular behaviour, including proliferation, signalling, metabolism, and migration. Maintaining a low level of ROS is likely key to promoting tissue regeneration and wound healing, as the high and excessive production of ROS can lead to oxidative stress and impaired wound healing [174]. Defensin-1: The antibacterial peptide, Def-1, has been shown to be responsible for promoting re-epithelialisation in vivo in a study using royal jelly [86]. The presence of Def-1 elevates the keratinocyte production of MMP-9 and enhances keratinocyte migration, resulting in a significant increase in wound closure rates.Anti-inflammation: Honey’s anti-inflammatory ability also plays a crucial role in tissue regeneration. During haemostasis, blood flow can be restricted through the capillaries (ischaemia) causing oxygen starvation (hypoxia), along with a lack of nutrients, both of which are vital for cell proliferation, which is required to repair tissue damage [16]. In addition, the previously mentioned antioxidative effect attributed to honey’s high phenolic content also supports anti-inflammation effects. These compounds exhibit radical scavenging properties due to the high reactivity of their hydroxyl radicals, clearing the free radicals formed due to inflammation [84,207,208]. This antioxidative effect has further been found to counter necrosis and reduce ischaemia on burns [209,210]. On the other hand, in weakly alkaline conditions (pH 7.0–8.0), honey’s phenolic acids and flavonoids demonstrate oxidative potential. Pro-oxidative phenols accelerate hydroxyl radical formation and H
Anti-inflammation: Honey’s anti-inflammatory ability also plays a crucial role in tissue regeneration. During haemostasis, blood flow can be restricted through the capillaries (ischaemia) causing oxygen starvation (hypoxia), along with a lack of nutrients, both of which are vital for cell proliferation, which is required to repair tissue damage [16]. In addition, the previously mentioned antioxidative effect attributed to honey’s high phenolic content also supports anti-inflammation effects. These compounds exhibit radical scavenging properties due to the high reactivity of their hydroxyl radicals, clearing the free radicals formed due to inflammation [84][175][176]. This antioxidative effect has further been found to counter necrosis and reduce ischaemia on burns [177][178]. On the other hand, in weakly alkaline conditions (pH 7.0–8.0), honey’s phenolic acids and flavonoids demonstrate oxidative potential. Pro-oxidative phenols accelerate hydroxyl radical formation and H2
O2 production, enhancing honey’s antimicrobial and anti-inflammatory effects [84,208].
production, enhancing honey’s antimicrobial and anti-inflammatory effects [84][176].Honey and tissue-engineered honey-based products have been explored to treat acute and chronic wounds by direct application, as a dressing, or in combination with other materials. When used as a topical agent it requires a secondary wound dressing such as gauze to protect the wound and contain the honey at a specific location, as the honey can leak away from the wound. The difficulty in the delivery and sustained release of the active ingredients of honey has facilitated the development of new strategies. Tissue-engineered scaffolds containing honey offer a potential route to precisely deliver and sustain honey at the site of wound healing and in other tissue regeneration applications [29,32,33]. Electrospinning [211–235], hydrogels and cryogels [219,220,236–250], foams [251,252], films [253], powders [254], cements [255], and bioinks [256,257] have been utilised to fabricate honey-based scaffolds (Figure 5).
Honey and tissue-engineered honey-based products have been explored to treat acute and chronic wounds by direct application, as a dressing, or in combination with other materials. When used as a topical agent it requires a secondary wound dressing such as gauze to protect the wound and contain the honey at a specific location, as the honey can leak away from the wound. The difficulty in the delivery and sustained release of the active ingredients of honey has facilitated the development of new strategies. Tissue-engineered scaffolds containing honey offer a potential route to precisely deliver and sustain honey at the site of wound healing and in other tissue regeneration applications [29][32][33]. Electrospinning [179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195][196][197][198][199][200][201][202][203], hydrogels and cryogels [187][188][204][205][206][207][208][209][210][211][212][213][214][215][216][217][218], foams [219][220], films [221], powders [222], cements [223], and bioinks [224][225] have been utilised to fabricate honey-based scaffolds.Electrospinning is the most commonly used approach to fabricate honey-based scaffolds due to its versatility in material and solvent compatibility, high surface area and porosity, allowing the loading of bioactive agents (e.g., nanoparticles, drugs, and growth factors), and its ability to produce nanofibres that can mimic the ECM. The non-woven fibrous meshes, produced through electrostatic acceleration and the elongation of a polymer jet and subsequent solvent evaporation or melt solidification, are widely explored as wound dressings [258]. Honey has been used in combination with polymers such as polyvinyl alcohol (PVA), cellulose acetate (CA), and polycaprolactone (PCL) to fabricate electrospun meshes. Schuhladen et al. [218] produced electrospun nanofibrous PCL and methylcellulose (MC) meshes containing manuka honey and bioactive glass. The presence of MGO in the manuka acted as a novel crosslinker for the MC. The meshes showed improved wettability, bioactivity, and cell viability and migration. However, the meshes showed no noticeable antibacterial properties against S. aureus or E. coli, which was attributed to the low manuka concentration used. The therapeutic properties of honey can be complemented by using additional natural bioactive agents. Gaydhane et al. [227] developed electrospun multi-layered PVA/CA fibres loaded with honey and curcumin, which had anti-inflammatory properties. The composite meshes showed enhanced antioxidant properties and moderate antibacterial activity. Alternatively, Ghalei et al. [226] developed a polylactic acid mesh containing honey and an nitric oxide donor, S-nitroso-N-acetyl-penicillamine, a potent antibacterial. The meshes showed sustained nitric oxide release for up to 48 h, a synergistic antibacterial effect with a 95% reduction in S. aureus and E. coli, and high cell viability and proliferation. The ability of honey to promote wound healing is a key factor in the use of honey in dressings. Yang et al. [212] fabricated a silk fibroin electrospun mesh containing manuka. The meshes showed significant bacterial inhibition, especially at a high manuka loading concentration, whilst supporting cell proliferation. An in vivo wound study in a mouse model showed a similar healing and closure rate by day 12 compared to a commercially available wound dressing, AquacelAg (, Reading, United Kingdom).
Electrospinning is the most commonly used approach to fabricate honey-based scaffolds due to its versatility in material and solvent compatibility, high surface area and porosity, allowing the loading of bioactive agents (e.g., nanoparticles, drugs, and growth factors), and its ability to produce nanofibres that can mimic the ECM. The non-woven fibrous meshes, produced through electrostatic acceleration and the elongation of a polymer jet and subsequent solvent evaporation or melt solidification, are widely explored as wound dressings [226]. Honey has been used in combination with polymers such as polyvinyl alcohol (PVA), cellulose acetate (CA), and polycaprolactone (PCL) to fabricate electrospun meshes. Schuhladen et al. [186] produced electrospun nanofibrous PCL and methylcellulose (MC) meshes containing manuka honey and bioactive glass. The presence of MGO in the manuka acted as a novel crosslinker for the MC. The meshes showed improved wettability, bioactivity, and cell viability and migration. However, the meshes showed no noticeable antibacterial properties against S. aureus or E. coli, which was attributed to the low manuka concentration used. The therapeutic properties of honey can be complemented by using additional natural bioactive agents. Gaydhane et al. [195] developed electrospun multi-layered PVA/CA fibres loaded with honey and curcumin, which had anti-inflammatory properties. The composite meshes showed enhanced antioxidant properties and moderate antibacterial activity. Alternatively, Ghalei et al. [194] developed a polylactic acid mesh containing honey and an nitric oxide donor, S-nitroso-N-acetyl-penicillamine, a potent antibacterial. The meshes showed sustained nitric oxide release for up to 48 h, a synergistic antibacterial effect with a 95% reduction in S. aureus and E. coli, and high cell viability and proliferation. The ability of honey to promote wound healing is a key factor in the use of honey in dressings. Yang et al. [180] fabricated a silk fibroin electrospun mesh containing manuka. The meshes showed significant bacterial inhibition, especially at a high manuka loading concentration, whilst supporting cell proliferation. An in vivo wound study in a mouse model showed a similar healing and closure rate by day 12 compared to a commercially available wound dressing, AquacelAg (ConvaTec Inc., Reading, UK).Hydrogels, crosslinked polymer networks swollen by water, are widely explored in tissue engineering and drug delivery applications due to their aqueous and porous three-dimensional structure, mimicking the native ECM, which allows the encapsulation of biomolecules and enables cell attachment, proliferation, and migration [31][227][228]. The ability to precisely tune the physiochemical, mechanical, and biological properties of the hydrogel enables a wide range of applications to be considered. For example, Bonifacio et al. [207] developed a gellan gum and manuka hydrogel with tuneable mechanical properties and release profiles of MGO depending on the type of cation crosslinker and presence of an inorganic material. Biofilms composed of clinical isolates of S. aureus and S. epidermidis cultured with the hydrogel showed a significant reduction in viability. The hydrogels were cytocompatible and exhibited chondrogenic differentiation. Subsequently, further investigation using silica, bentonite, and halloysite fillers showed improved mechanical properties [208]. The hydrogels were able to inhibit bacterial growth in an infected scaffold implanted into an in vivo mouse model; additionally, the silica improved this inhibition. PVA-based hydrogels which are biocompatible, water-soluble, highly swelling, and non-toxic have been explored, with honey showing antibacterial properties. A manuka and PVA hydrogel crosslinked using sodium tetraborate and containing 80% honey in the dry state was developed by Tavakoli and Tang [204]. The hydrogel exhibited the sustained release of honey for over 24 h, low adhesion in a model after 24 h swelling, and the significant inhibition of S. aureus but negligible inhibition of E. coli. An alternative crosslinking method for PVA is freeze–thawing, or cryogelation, explored by Santos et al. [217] in the development of a multi-layer hydrogel with graded honey concentrations. The samples showed negligible inhibition against S. aureus, attributed to the low manuka concentration used. Shamloo et al. [211] fabricated PVA hydrogels by freeze–thawing, which contained gelatin, chitosan, and honey. PVA by itself has poor bioactivity; thus, adding chitosan and gelatin provides a haemostatic agent and cell-binding motifs, respectively. The antibacterial inhibition against P. aeruginosa and S. aureus increased with a higher concentration of honey and showed higher inhibition than a hydrogel dressing for burns (Burn Tec, KikGel Ltd., Ujazd, Poland). The hydrogels were cytocompatible and in an in vivo rat model increased the rate of wound closure and formed well-defined epidermal and dermal tissue with increased expression of collagen.
Figure 5. Honey-containing scaffolds. Scanning electron microscopy images of electrospun fibres containing (a) 0%, (b) 30%, and (c) 70% manuka honey [212]; (d) gellan gum hydrogels with 2% manuka honey and (e) reinforced with clay halloysite nanotubes [240]; and freeze-dried powders using methylated-β-cyclodextrin and (f) 70% or (g) 50% SurgihoneyRO™ and (h) (2-hydroxypropyl)-β-cyclodextrin with 50% SurgihoneyRO™ [254]. Reproduced with permission from Elsevier.
Hixon et al. [187] compared the properties of silk fibroin electrospun meshes, hydrogels, and cryogels containing manuka. The use of a single material, silk, was to elucidate how the structural properties of the scaffold influenced bacterial inhibition. The electrospun scaffolds had a higher inhibition of S. aureus than the hydrogel or cryogels. This was attributed to the high surface area of the fibres allowing the rapid release of the manuka and the flat mesh structure having a greater contact area with the bacteria. This demonstrates the importance of scaffold design for the intended application.Hydrogels, crosslinked polymer networks swollen by water, are widely explored in tissue engineering and drug delivery applications due to their aqueous and porous three-dimensional structure, mimicking the native ECM, which allows the encapsulation of biomolecules and enables cell attachment, proliferation, and migration [31,259,260]. The ability to precisely tune the physiochemical, mechanical, and biological properties of the hydrogel enables a wide range of applications to be considered. For example, Bonifacio et al. [239] developed a gellan gum and manuka hydrogel with tuneable mechanical properties and release profiles of MGO depending on the type of cation crosslinker and presence of an inorganic material. Biofilms composed of clinical isolates of S. aureus and S. epidermidis cultured with the hydrogel showed a significant reduction in viability. The hydrogels were cytocompatible and exhibited chondrogenic differentiation. Subsequently, further investigation using silica, bentonite, and halloysite fillers showed improved mechanical properties [240]. The hydrogels were able to inhibit bacterial growth in an infected scaffold implanted into an in vivo mouse model; additionally, the silica improved this inhibition. PVA-based hydrogels which are biocompatible, water-soluble, highly swelling, and non-toxic have been explored, with honey showing antibacterial properties. A manuka and PVA hydrogel crosslinked using sodium tetraborate and containing 80% honey in the dry state was developed by Tavakoli and Tang [236]. The hydrogel exhibited the sustained release of honey for over 24 h, low adhesion in a model after 24 h swelling, and the significant inhibition of S. aureus but negligible inhibition of E. coli. An alternative crosslinking method for PVA is freeze–thawing, or cryogelation, explored by Santos et al. [249] in the development of a multi-layer hydrogel with graded honey concentrations. The samples showed negligible inhibition against S. aureus, attributed to the low manuka concentration used. Shamloo et al. [243] fabricated PVA hydrogels by freeze–thawing, which contained gelatin, chitosan, and honey. PVA by itself has poor bioactivity; thus, adding chitosan and gelatin provides a haemostatic agent and cell-binding motifs, respectively. The antibacterial inhibition against P. aeruginosa and S. aureus increased with a higher concentration of honey and showed higher inhibition than a hydrogel dressing for burns (Burn Tec, KikGel Ltd., Ujazd, Poland). The hydrogels were cytocompatible and in an in vivo rat model increased the rate of wound closure and formed well-defined epidermal and dermal tissue with increased expression of collagen.
Hixon et al. [219] compared the properties of silk fibroin electrospun meshes, hydrogels, and cryogels containing manuka. The use of a single material, silk, was to elucidate how the structural properties of the scaffold influenced bacterial inhibition. The electrospun scaffolds had a higher inhibition of S. aureus than the hydrogel or cryogels. This was attributed to the high surface area of the fibres allowing the rapid release of the manuka and the flat mesh structure having a greater contact area with the bacteria. This demonstrates the importance of scaffold design for the intended application.
An alternative approach by Hall et al. [254] is the development of an absorbent and in situ gelling powder containing SurgihoneyRO™ (Matoke Holdings Ltd., Abingdon, United Kingdom), a commercially available engineered honey with demonstrated antimicrobial and wound healing properties [18,19,178–180]. A starch-based drying agent combined with freeze-drying and milling was used to produce a powder (particle size ~200 µm). Sodium polyacrylate was incorporated to allow in situ gelation, which was observed after <1 min in response to a volume of simulated wound exudate forming a hydrogel barrier that filled the defect. The powders showed production of H
An alternative approach by Hall et al. [222] is the development of an absorbent and in situ gelling powder containing SurgihoneyRO™ (Matoke Holdings Ltd., Abingdon, UK), a commercially available engineered honey with demonstrated antimicrobial and wound healing properties [18][19][229][230][231]. A starch-based drying agent combined with freeze-drying and milling was used to produce a powder (particle size ~200 µm). Sodium polyacrylate was incorporated to allow in situ gelation, which was observed after <1 min in response to a volume of simulated wound exudate forming a hydrogel barrier that filled the defect. The powders showed production of H2
O2
(~30 µmol g−1 at the peak) for up to 8 days. This resulted in the inhibition of the growth of P. aeruginosa, E. coli, and S. aureus. Additionally, high cell viability and comparable cell proliferation to a cell-only control was observed when cultured with different powder concentrations. Subsequently, Hall et al. [255] explored the development of a calcium sulphate cement containing SurgihoneyRO™ (Matoke Holdings Ltd., Abingdon, United Kingdom) for orthopaedic applications. The production of H
at the peak) for up to 8 days. This resulted in the inhibition of the growth of P. aeruginosa, E. coli, and S. aureus. Additionally, high cell viability and comparable cell proliferation to a cell-only control was observed when cultured with different powder concentrations. Subsequently, Hall et al. [223] explored the development of a calcium sulphate cement containing SurgihoneyRO™ (Matoke Holdings Ltd., Abingdon, UK) for orthopaedic applications. The production of H2
O2
in the cements peaked at 24 h and the inhibition of S. aureus and P. aeruginosa growth was comparable to a dose of gentamicin.The versatility and variety of approaches using honey in scaffolds shows the drive to reformulate honey into innovative delivery systems for both antimicrobial and tissue-regenerative applications. For example, a novel approach is the use of bioprinting to develop alginate scaffolds [256] and pectin patches [257] containing honey. The predominant application areas are wound dressings, but new areas such as cartilage [239,240] and bone [255] are being explored, which demonstrates the potential of honey-based scaffolds outside the traditional clinical uses.
The versatility and variety of approaches using honey in scaffolds shows the drive to reformulate honey into innovative delivery systems for both antimicrobial and tissue-regenerative applications. For example, a novel approach is the use of bioprinting to develop alginate scaffolds [224] and pectin patches [225] containing honey. The predominant application areas are wound dressings, but new areas such as cartilage [207][208] and bone [223] are being explored, which demonstrates the potential of honey-based scaffolds outside the traditional clinical uses. However, the majority of studies lack characterisation for the presence of GOx in the processed honey-based scaffold or the generation of H2
O2
. This is key for the peroxide-based antimicrobial properties and the modulation of cell behaviour. Furthermore, the harsh processing steps utilised in the development of the scaffolds (e.g., high temperatures, use of solvents, crosslinking steps, and sterilisation protocols) may denature the GOx, rendering it inactive. Additionally, prolonged contact with water during processing can prematurely activate the GOx and initiate the production of H2
O2
. However, other honey antimicrobial and bioactive compounds may remain active, especially MGO in manuka-honey-based scaffolds.