1952, and the company Spansule® just came out with a sustained-release capsule technology– marked as the first modern drug delivery system—delivering a drug to its desired location in the body 12 hours after being taken orally. Since then, drug delivery systems have made notable leaps in efficiency and safety. However, these advances are held back by the limitations of synthetic carriers, including toxicity levels and non-efficient delivery. As a result, scientists have turned their attention to nature-derived carriers. Their decreased levels of toxicity make them safer and they already contain properties that suit them to drug delivery.
The carriers must be nanosized, exhibit high levels of stability, be cell-membrane permeable, and in general, be able to navigate the body, while simultaneously protecting and releasing the drug when necessary.
Many possible natural substances that may be used, however, one notable option that is already being tested is an iron-storage protein called ferritin. Ferritin is ideal as it self assembles into a 24 monomer protein with reliably uniform size and structure available for chemical or genetic modification to transport various cargoes and target specific sections of molecules.
Ferritin’s unique characteristics have already made a name for themselves in other applications as wall. For example, the capacity of ferritin to load iron gives it the ability to combine and interact with with oxyanions which the Dutch company BiAqua has been using as a new water treatment strategy. As a drug delivery candidate, ferritin expresses remarkable temperature and pH tolerance, biodegradability, and a hollow cage for the cargo that can be dissembled and reassembled as needed for encapsulation of drugs.
Certain ferritin-based nanotherapeutics have been created by loading ferritin with certain small molecules.It as been determined that ferritin provides strategies for metal nanoparticle encapsulation as it is already naturally an iron storage protein.
A study published in sciencedirect.com titled “Ferritin-based drug delivery systems: Hybrid nanocarriers for vascular immunotargeting” revealed multiple loading methods with a drug and examples of these modified platforms. One idea is to bind the drugs to the ferritin surface, which may be suitable for certain drugs, though it leaves them exposed to the external environment. Another idea is the diffusion of drug particles through the pores of ferritin or possibly pH/salt-based deconstruction, then reconstruction of drugs inside the hollow ferritin center.
As mentioned before, ferritin can be modified to load specific drugs and this is already being done, for example, by incorporating a Fe-binding peptide to aid in antibody binding. Others have engineered ferritin to have certain peptides which makes siRNA binding easier.
Ultimately, protein nanocages may just be the future for in-body drug delivery and nanotherapy. They are less invasive, safer, and extremely abundant, with ferritin alone being found in most living organisms. Their versatile structures are modifiable to better suit a spectrum of drug types and open up the possibility of even further uses for this protein.
Ferritin has a strong potential in the drug delivery world and even other medical fields. After further research into them and their biocompatibility, these protein nanocages may just be ready to change how we transport drugs forever.
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