Sophie Bulman of Leeds University (UK) thought dressings which used Manuka Honey to increase the rate of healing of chronic wounds owed at least some of their success to the methylglyoxal content of the honey. Infections in chronic wounds were resistant to antibiotics and while some treatment success was claimed for silver impregnated dressings, bacteria were now evolving with silver resistance also. Alternative metals e.g. zinc and naturally derived antibacterials such as Manuka honey were therefore being evaluated. Alginate nonwovens, knitted viscose and non-fibrous hydrocolloids were all being used as substrates for the honey but it was a difficult material to handle due to its stickiness, could cause skin rashes and was not suitable for use on the open wounds of diabetics.
Manuka honey was compared with the equivalent amount of methylglyoxal as an antimicrobial finish on textiles using ISO 20743:2007 and found to be similarly effective. PP spunbond nonwovens samples were then coated either by electrospraying a water-based solution of 8% PVA loaded with 11% MG, or electrospinning the same solution into a web of nanofibres. Both methods were intended to give the maximum possible surface area. FTIR and NMR analysis proved the PVA nanofibres contained MG. The samples were then tested using the zone of inhibition method on agar plates colonised with E. coli and S. aureus bacteria according to ISO 20645:2004. The controls (spunbond with no MG) showed no zone of inhibition, whereas the spunbond electrosprayed with MG showed zones of 4mm for E. Coli and 6mm for S. Aureus. The MG/PVA nanofibre coats were even more effective showing inhibition of bacterial growth up to 20 and 21mms respectively. Asked how much MG was required to render the nonwoven antimicrobial Ms Bulman said 1mg/cm2.