Drug Delivery

Currently, most diseases are treated with advanced molecular biology strategies and drugs. Due to their susceptibility to degradation and deactivation, it is recommended that the drugs are loaded in a matrix until the moment of release. Drug delivery systems control the drug release rate and release location in the body. These systems will have the ability to treat diseases locally and more effectively, preventing non-specific and harmful interaction with healthy tissues and decreasing the amount of drug dose required.

Drug Delivery System

To allow a localized and improved control on drug release, newer drug delivery systems focus on implantable nanoscaled delivery devices. Drug delivery systems having this length scale allow for a relative high drug load while at same time possess a large surface area to weight ratio. The versatility of electrospinning allows the creation of porous fibrous nano- to micron sized structures in a very controlled and reproducible way. Moreover, a biodegradable electrospun membrane could be implanted close to a diseased organ for localized and sustained drug delivery/release. Several techniques can be used to incorporate drugs or biomolecules in electrospun nanofibers. Following techniques and statement are also transferable to electrospraying of particles:

  • Direct dissolution/blending: Drugs, proteins or other bioactive substances can be incorporated by simply adding them directly to the electrospinning polymer solution. The drug is released mostly via diffusion and the degradation rate of these structures can be tuned by choosing the proper material and by controlling the fiber size.
  • Emulsion electrospinning: The drug, protein or compound of interest is mixed in the electrospinning solution with a surfactant, allowing the formation of nano and microspheres loaded with the drug. The resulting fibers will have a core shell conformation with the micro- nanospheres in the core of the fiber surrounded by the polymer.
  • Coaxial electrospinning: Coaxial electrospinning enables two different solutions to be spun simultaneously, generating a core/sheath structure. It is used when the drug has limited resistance against the used solvent or is immiscible with the polymer solution. The resulting mesh will be composed by fibers with a core/shell structure. The polymer will act as the shell, protecting and holding the drug in the core of the fiber. The drug release can be adjusted by the wall thickness and polymer-drug interactions.
  • Supramolecular interactions: Drugs, proteins or other bioactive substances can also be bound or incorporated in the side chains or polymer backbone via supramolecular chemistry. The drug can be expressed on top of the fiber or slowly released by time, depending on the polymer degradation rate.
  • Post processing: Additionally the drug, proteins and bioactive substances can be bound to the fiber surface using post electrospinning treatments with chemically bonding or simpler dip coating processes.

Recent studies have shown that electrospun fibers with inherently high surface area to volume ratio and high interconnectivity have a number of benefits, including: high drug loading efficiency; the ability to overcome mass transfer limitations associated with most polymeric delivery systems; the facilitation of drug diffusion; and improvement of solubility of various bioactive molecules. Encapsulation of these bioactive molecules into electrospun fibers allows for localized delivery of antimicrobials, anti-inflammatories, antiscarring agents, antineoplastic agents, immunosuppressives, growth factors, cytokines, genes (DNA and RNA), enzymes, and a number of other important bioactive ingredients to target sites.

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