Approaches to drug delivery: Confinement of aspirin in MIL-100(Fe) and aspirin in the de novo synthesis of metal–organic frameworks

• This is first report that aspirin was used as the model drug to encapsulate in MOF.
• Two techniques have been demonstrated in delivering drug using a metal-organic framework (MOF) MIL-100(Fe).
• First method is the encapsulation of a small molecule drug (aspirin) by the MIL-100(Fe) referred as the ASA@MIL-100(Fe).
• The other method is that using de novo synthesis of AH-series MOFs (bio-MOFs) with aspirin was utilized.
• Both drug carriers exhibited potential for a sustained delivery in simulated biological fluids for a prolonged period.

Aspirin is known as a wonder drug due to its vast therapeutic range however, side effects after oral administration include gastrointestinal irritation. Shielding of the free aspirin was developed by confining it inside the pores of MIL-100(Fe). This was done by immersion of the metal–organic framework (MOF) in a saturated aspirin solution which achieved a ∼181% loading efficiency by time-of-flight mass spectrometer (TOF/MS) detection and took about 14 days for the drug release in phosphate buffered saline at 37 °C. The pore volume of the MOF was found to be the determinant in the loading efficiency of aspirin when variations arise between batches of the encapsulating material. Another approach in the use of MOFs for aspirin delivery was to incorporate aspirin as ligand in the de novo synthesis of the AH-series MOFs (bioactive MOFs). The diffusion of aspirin from the MOFs was slower in acidic medium and was faster in basic medium. This encapsulation technique of aspirin would potentially spare it from enzymatic degradation and interactions in the stomach that would lessen the amount of the drug transported into the blood.

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