Electrospinning Nutritional Supplements

Most nutritional supplements are susceptible to degradation under environmental conditions. Electrospinning provides a method of encapsulating the supplements in a protective matrix with tailored release rate. Almost any type of nutritional supplements can be incorporated into electrospun fibers, This includes water soluble vitamins, fish oil, minerals and even pro-biotic bacteria.

Preservation of active compounds through encapsulation in electrospun fibers is probably the most widely investigated field in the application of food technology. Folic acid without any coating is susceptible to degradation when exposed to light and acidic condition. However, when it is encapsulated within sodium alginate-pectin-poly(ethylene oxide) nanofibers, almost 100% of the folic acid is retained after 41 days of storage in the dark at pH 3. This contrasts against 8% recovery after one day of storage at pH 3 [Alborzi 2012]. Using pure zein, Fernandez et al (2009) was able to encapsulate β-carotene and increase its light (UV) stability up to 24 h compared with unprotected β-carotene and solution cast of fiber β-carotene powder. Moomand (2014) demonstrated the encapsulation of fish oil in electrospun zein fibres. In his thesis, fish oil encapsulated in zein fibres was significantly more stable than non-encapsulated fish oil especially at higher temperature of 25°C and 60°C. However, using a different polymer, Garcia-Moreno et al (2016) showed fish oil encapsulated in electrospun polyvinyl alcohol (PVA) were less stable from unprotected fish oil. More studies are thus required to identify the influence of electrospun matrix on protection of fish oil against environmental degradation.

There are several edible and natural materials that can be electrospun into fibers and these may be used for encapsulating supplements. Inan-Cinkir et al (2023) compared the performance of using zein or gelatin-pectin for encapsulating carotenoid from watermelon using electrospinning. Zein is a plant-based protein while pectin is anionic heteropolysaccharide. Pure zein solution is electrospinnable to form fibers but not pectin hence gelatin was added to form an electrospinnable solution blend. Carotenoid was homogenized with glycerol and then immersed in water to obtain a micro emulsion (ME). This ME was subsequently blended with either zein or gelatin-pectin solution for electrospinning. With zein, loading of ME to 30% and 40% was possible without any significant drop in electrospun fiber quality. However, with gelatin/pectin, smooth fiber can only be maintained up to 30% ME. At 40% ME loading, beads and fused fibers were found on electrospun gelatin/pectin fibers. Therefore, zein is a better choice for encapsulation of carotenoid ME for electrospinning into fibers compared to gelatin/pectin.

For water soluble polymer, high surface area of electrospun nanofibers allows it to quickly dissolve upon contact with water and releases the load it is carrying. Kyzy et al (2014) used this property to introduce nutritional iodine based on electrospun fast dissolving oral mat. With diameter ranging from 120 nm to 400 nm, the polyethylene oxide nanofibers carrying KIO₃ achieves complete dissolution within 5 mins in water. Many active compounds have poor aqueous solubility and this limit their application as therapeutic drugs and supplements. Sriyanti et al (2018) attempted to overcome this constraint by using electrospun fibers as a carrier for α -Mangostin which is a major active compound of mangosteen (Garcinia mangostana L.) pericarp extract (MPE) with potent antioxidant activity. Polyvinylpyrrolidone (PVP) was used as the carrier due to its low toxicity and good water solubility. Electrospun α-mangostin loaded PVP fibers was found to be amorphous compared to the crystalline form of pure α-mangostin powder. Release of α-mangostin was fast in the PVP nanofibers with over 90% released in an hour while less than 35% were released from its powder form. The radical scavenging activity of the α-mangostin released from the electrospun fibers was good with a IC₅₀ value of 55-67 µ g/ml which was slightly lower than pure α-mangostin powder with value of 69 µ g/ml. Porous and thin electrospun mats containing other ingredients such as mint or medications may offer advantages over off-the-shelf oral dissolving film strips. A challenge when water soluble polymer was used as a carrier is that the active ingredients may be poorly soluble in water. This reduces the loading capacity and efficiency in the electrospun fibers. Rezaei et al (2019) used βCD for complexing with curcumin to improve the compound solubility in polyvinyl alcohol (PVA)/gum solution and improve loading efficiency. With pure curcumin, the maximum amount of curcumin that can be added to the PVA/gum solution for electrospinning without beads on the fibers is just 2%(w/w). However, at this concentration, the loading efficiency of curcumin in gum/PVA/curcumin nanofibers is just 65%. With complexing of curcumin in βCD before blending in gum/PVA solution, up to 4%(w/w) can be loaded without beads on the electrospun nanofibers. Further, loading efficiency was around of 92-95%.

Schematic illustration of electrospun fibers with bacteria embedded within.

Beyond encapsulation of vitamins and minerals, electrospun fibers may also be used for delivery of pro-biotic bacteria. Nagy et al (2014) investigated the use of water soluble polymers (polyvinyl alcohol and polyvinylpyrrolidone) for encapsulation and delivery of Lactobacillus acidophilus bacteria. The survival rate of the bacteria was found to be between 34% and 68%. Fung et al (2011) used a mixture of soluble dietary fiber (SDF) from agrowastes and PVA for encapsulation of Lactobacillus acidophilus using electrospinning. The encapsulated bacteria showed a survival rate of 78 to 90% post electrospinning and remained viable in refrigeration temperature for 21 day of storage study. Liu et al (2016) used an aqueous solution containing two edible polysaccharides, pectin (PEC) and pullulan (PUL) for encapsulation of probiotic bacteria Lactobacillus rhamnosus GG (LGG). The electrospun PEC/PUL fibers containing the bacteria were cross-linked by soaking in 5% CaCl₂ solution. 90% of the bacteria were found to remain viable after electrospinning and cross-linking which demonstrates the potential use of edible polysaccharides as bacteria carriers. To further improve the survivability of probiotics, Akkurt et al (2022) blended aqueous calcium caseinate (CaCAS) and sodium caseinate (NaCAS) with pullulan (PUL) aqueous solutions for electrospinning into fibers. Lactobacillus rhamnosus GG (LGG) was added into the solution just before electrospinning. The resultant electrospun fibers CAS-PUL-LGG had a mean diameter of 212 nm while NaCAS-PUL-LGG fibers had a mean diameter of 286 nm. LGG can be seen as elongated beads on part of the fibers. Viability of the LGG recovered from the nanofibrous mats after electrospinning showed no loss in the bacteria. The presence of milk milk proteins such as caseins may aid the survival of encapsulated LGG within the fibers and may potentially improve the survival of the probiotic if the CAS-PUL-LGG fiber mats were taken orally.

Scanning electron microscopy images of electrospun Lactobacillus rhamnosus GG (LGG) incorporated in fibrous mats from CaCAS-PUL-LGG [Akkurt et al 2022].