Exploration of the bioadhesivity of sporopollenin microcapsules and their use to encapsulate and release drugs and vitamin D

Almutairi, Farooq

Abstract

Sporopollenin is the polymeric fabric of the outer shell (known as exine) of plant spores and pollen grains. It is a highly cross-linked polymer composed of carbon, hydrogen and oxygen. It contains functional groups such as phenols, carboxylic acids and aliphatic alcohols as well as hydrophobic saturated and unsaturated alkyl chains. Sporopollenin is one of the most extraordinarily resistant polymers known in the organic world. It has the ability to resist harsh biological, chemical and physical environments, as intact sporopollenin exines have been found intact in some sedimentary rocks that are 500 million years old.

This hydrophobic biopolymer has interesting properties, as its lipids (which are 20 % w/w of the total mass of extracted spores) possess liquid-like behavior in a dry solid polymer. This biopolymer has the ability to transform the liquid simple C18 fatty acids into “dry liquid” state when adsorbed or attached chemically to the surface.

Sporopollenin exine capsules (SECs) have potential as a microparticle for vitamin and drug microencapsulation offering protection, controlled release and absorption enhancement. SECs have been shown to be able to encapsulate hydrophilic and hydrophobic drugs and vitamins and they have the ability to control the release of the encapsulated actives depending on the pH.

In this study vitamin D, diclofenac sodium salt and mesalamine were encapsulated in L. clavatum SECs, and then released into buffer solutions at different pHs that mimic the GIT pHs. The release of such kind of vitamin and drugs showed the direct effect of pH factor on the release of the SECs contents. Vitamin D was released in pH 7.4, but was not in acidic pH. This was an interesting point, especially, for protecting the encapsulated vitamin D from the harsh acidic environment of stomach and release it in the mildly basic environment of small intestine. Also, diclofenac sodium was released fully in pH 7.4 within 12 hours, whereas less than 40 % was released in pH 1.5. However, the mesalamine showed a full release in acidic pH which showed that SECs need coating to be used for mesalamine. The adsorption of the drugs to the SECs was shown to be very low (0.4 %), which means that almost all the drug will be released and would not adsorb to the SECs surface, especially in the GIT when they would be flushed with fluid continuously.

It is proposed that the ability of SECs to enhance the absorption is related to the mucoadhesivity that they possess, which was shown to be higher than chitosan and lower than carbopol. The mucoadhesion strength for L. clavatum powder polymer was statistically significant either with their lipids in (p-value = 0.03), or when their lipids were removed (p-value = 0.01).Also, the “dry liquid” C16 and C18 fatty acids of SECs might play role in absorption enhancement by disturbing the tight junction of the paracellular pathway transport, were most of the hydrophilic small molecules pass through to blood stream.

The disintegration time of SECs tablets gives an idea about the best extraction protocol to use to increase the time of disintegration or decrease it depending in the site of absorption. For example, AH-SECs of L. clavatum was disintegrated within 2 h and lost 23.33 % of their mass, which is a preferable SECs type to be used for drug release in intestine within 2 h from the time of SECs tablet ingestion.

Citation

Almutairi, F. (2015). Exploration of the bioadhesivity of sporopollenin microcapsules and their use to encapsulate and release drugs and vitamin D. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4223953

• Thesis Type: Thesis
• Deposit Date: Feb 21, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4223953
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Nov 1, 2015