Schematic of the modified tri-axial electrospinning process and its use for preparing core-shell drug-loaded nanofibers.
(a) A FESEM image of the cross-section of a fiber and (b) a TEM image of the same.Researchers have developed a novel composite fiber, and a clever way to make it, that could make drug delivery more effective [Yang et al., Acta Biomaterialia 35 (2016) 77].
Electrospinning is a well-known and simple means of producing long, continuous fibers. A starting liquid – usually a polymer in solution or melted form – is drawn from the tip of a needle known as a ‘spinneret’ by an electric force. Using two needles, one nested inside the other, produces two-component fibers with a core-shell structure. Now researchers from the University of Shanghai for Science and Technology, the University of Westminster, and University College London have added a third needle to create a tri-axial process.
But not only that, the researchers have shown for the first time that not all the liquids used in the process have to be spinnable. Despite the ubiquity of the process, only around 100 polymers can actually be electrospun into fibers. The new tri-layer concentric spinneret designed by the researchers means that only one of the liquid components has to be spinnable. The other two could be different liquids, such as a solvent or solution of a fragile active ingredient like a protein or drug.
The core/shell fibers have ideal characteristics for advanced drug delivery systems, believe the researchers. As an example, the team produced a pH-sensitive polymer fiber with a lipid core loaded with the anti-inflammatory drug diclofenac.
“To the best of our knowledge, this is the first time that a ‘hard’ polymer and ‘soft’ lipid-drug core/shell fiber nanocomposite has been investigated,” says Deng-Guang Yu from Shanghai. “It is also the first time that a modified tri-axial electrospinning process has been reported to prepare this type of material.”
The core-shell structure of the nanocomposite fiber leads to a two-step drug release process in the body. Using a pH sensitive polymer as the fiber shell prevents drug release in the low-pH conditions of the stomach. But when the fiber is in the neutral pH conditions of the colon, for example, the polymer shell dissolves, releasing some of the drug; the core then breaks down gradually releasing the remainder.
“This novel structure demonstrates excellent performance in targeting delivery of the drug and improving the dissolution and absorption of poorly water-soluble drugs,” says Yu.
While core-shell nanoparticles have been widely reported for drug delivery, similar fibers have received much less attention. But with the easy production of large volumes of high-quality fibers now becoming a reality, this modified electrospinning technique could represent a significant innovation for biomaterials and tissue engineering as well as drug delivery.