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Electrospun fibers for fungus control

Fungus is an important class of plants that can be found in almost any environment and have major impact in food, agriculture, hygiene and healthcare. Food spoilage is often caused by fungus and pathogenic fungus is a threat to global agriculture and healthcare. In the search for methods to control fungus, researchers are starting to explore the possible use of electrospun nanofibers. There are various strategies that can be employed to control fungal pathogens or even fungi growth.

The most straight forward strategy is to use electrospinning to encapsulate anti-fungal compounds within nanofibers. Dar and Soytong (2014) have shown that electrospinning is able to encapsulate active compounds from Chaetomium species which are known to be effective anti-fungal agent. El-Newenhy tested the effectiveness of Nylon-6 nanofibers loaded with 5,5-dimethyl hydantoin (DMH) against various microbes including two pathogenic fungi: (1) Aspergillus niger and (2) Aspergillus flavus. Their results showed that the drug loaded nanofibers are able to exhibit zone of inhibitions on the two fungal species after 4 hours. Ketoconazole is an azole antifungal drug that is used for superficial and systemic fungal infection treatment. Veras et al (2016) incorporated ketoconazole into electrospun polycaprolactone (PCL) fibers and tested against Aspergillus flavus, A. carbonarius and Penicillium citrinum by agar diffusion test. After 5 days, zone of inhibition was observed for all tested fungi with significantly greater zone of inhibition against A. flavus and P. citrinum compared to A. carbonarius.


Inhibition zones of the electrospun nylon-6 nanofiber containing drug against two pathogenic fungi: (1) Aspergillus niger and (2) Aspergillus flavus. [El-Newehy et al. Journal of Nanomaterials, vol. 2011, Article ID 626589, 8 pages, 2011. This work is licensed under a Creative Commons Attribution 3.0 Unported License.]

Misra et al (2017) tested the effect of tolnaftate-loaded polyacrylate electrospun nanofibers on dermatophytosis. They used a combination of Eudragit grades (ERL100 and ERS100) to construct an electrospun membrane with good exudate absorption ability, adhesion property on wound and controlled release of tolnaftate. PEG 400, a plasticizer was added to the mixture to reduce agglomeration of tolnaftate. With 3:1 ratio of ERL100/ERS100, the preferred sustained drug release for 8 hrs were obtained. An in vivo rat model was used to test the effectiveness of the tolnaftate loaded electrospun fibers on Trichophyton rubrum and M. canis. While the drug loaded membrane was shown to be effective against T. rubrum, it was not effective against M. canis. Interestingly, mice treated with pure tolnaftate had symptoms of dermatophytosis after seven days but the drug loaded membrane were able to completely eradicate T. rubrum. Better efficacy of the membrane can be attributed to the continuous drug release over the treatment period.

Electrospun fibers with anti-fungal properties have been tested for agricultural application. Castaneda et al (2014) used blending to incorporate commercially available fungicide (Vitavax Thiram SC-200 and Carbex 500) into ethyl cellulose before electrospinning over rice seeds. The results showed an improvement of rice germination to about 95% with the nanofiber coating, which is 8% more than the negative control (rice without coating). Using nanofibers to encapsulate the fungicide may allow different chemical additives to be used together through separate nanofibers. Esca is a disease of grapevine caused by Phaeomoniella chlamydospora and Phaeoacremonium aleophilum. Spasova et al (2019) tested the use of electrospun cellulose acetate/polyethylene glycol (CA/PEG) containing 5-chloro-8-hydroxyquinolinol (5-Cl8Q) for the protection of grapevine against P. chlamydospora and P. aleophilum fungi. Using agar culture, the electrospun CA/PEG membrane loaded with 5-Cl8Q showed inhibitory effect on P. chlamydospora and P. aleophilum fungi while neat electrospun membrane has no effect on them. This inhibitory effect was sustained over a 96 hrs period. Drug release test showed an initial burst release with 83% of the load released in the first 30 mins and this allows the minimum inhibitory concentration (MIC) to be reached quickly. An advantage of electrospun membrane is that its high porosity allows the plant to breathe although actual application method needs to be determined.

Food industry will also benefit greatly from fungal control for the reduction of spoilage. Ai-Tang et al (2013) has shown that micelles containing natural Neem Seed Oil and encapsulated within electrospun fibers of cellulose acetate (CA) and poly (ethylene oxide) (PEO) was able to exhibit antifungal effect on wounded-inoculated tomatoes. For this, a high loading of 50% Neem Seed Oil within the fibers is needed.

Another area for fungal control is the prevention of fungal infection in wound management. Lakshminarayanan et al (2014) tested the effectiveness of five different US Food and Drug Administration-approved antifungal drugs (amphotericin B, natamycin, terbinafine, flucon¬azole, and itraconazole) loaded into electrospun gelatin fiber mats. Of the drugs loaded into the gelatin fibers, polyenes (amphotericin B, natamycin) was the most effective in terms of inhibiting the growth of yeasts and filamentous fungal pathogens while being noncytotoxic to primary human corneal and sclera fibroblasts.

Apart from using additives with anti-fungal properties, another method of controlling phytopathogenic strains of fungus is to introduce natural occurring fungus to inhibit the growth of others. Trichoderma viride is a mold and a natural biofungicide which has been tested for seed and soil treatment to suppress other fungal pathogens. Spasova et al (2011) has successfully electrospun nanofibrous mat containing chitosan and Trichoderma viride spores. The resultant mat is able to inhibit the growth of phytopathogenic strains of fungus such as Fusarium and Alternaria.

There are numerous research on the effect of fiber diameter on mammalian cells such as adhesion, proliferation and contact guidance. However, there are far less research on the effect of fiber diameter on fungus growth. Parveen carried out studies on the alignment and size effect of electrospun polyacrylonitrile (PAN) on the growth of two fungal strains, S. cerevisae and C. albicans. Their studies showed that smaller fiber diameter (760 nm) showed more inhibitions to the two yeasts cells compared to larger diameter fibers (1800 nm) and PAN film showed the least inhibition. They hypothesised that with smaller fiber diameter, greater contact points with the yeast cell body resulted in more internal stress on it and thus greater inhibition effect. Similarly, inhibition from randomly oriented fibers were greater than aligned fibers due to more contact points on random fibers compared to aligned fibers. Since more contact points to yeast cell body have lead to greater inhibition, Parveen (2018) tested the effect of electrospun fibers surface roughness on the fungus. Using electrospun PAN finer, they vary its surface roughness either by loading with graphene to create positive curvature (bumps) or removal of sacrificial polymers to create negative curvature (pores). With positive curvature on sub-micron diameters fiber, its effects on fungal strains, S. cerevisae and C. albicans were not significant. In fact larger fiber diameter from the addition of graphene resulted in less inhibition effect. However for fibers with diameter more than a micron, the roughened surface due to the addition of graphenes there were significant inhibition effect. This may be due to increased contact points compared to smooth, large diameter fibers. For negative curvature surface roughness, there were obvious increase in S. cerevisae and C. albicans inhibition. The pores on the fiber surface increases contact points and this is consistent with the hypothesis that more contact points led to more internal stress experienced by the fungi cell body and thus reducing growth.



Published date: 25 Aug 2015
Last updated: 16 June 2020

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