Nanoporous Calcium Carbonate-Based Substrates for the Controlled Delivery of Functional Materials

The overall aim of this project was to study `functionalised' calcium carbonates (FCCs) for use as a carrier for the controlled release of `actives,' by permeation and diffusion, and is being proposed as an environmentally friendly and non-toxic pharmaceutical excipient, nutraceutical, and flavour carrier. The delivery of a drug to its target site in the appropriate amount and time-frame in order for it to have a controlled release effect whilst achieving the maximum therapeutic effect remains a topic of design and development for novel drug delivery systems.

 

FCCs encompass a family of new pharmaceutical excipients in which the conditions of manufacture follow strict process regulations with respect to the grade of reagents that are employed and the microbiological environment under which they are produced, and include freedom from organic polymers.

 

Adjustments to the FCC production process can be used to produce a wide range of different morphologies, and raise the possibility of tailoring the void structures of the particles to provide controlled release delivery vehicles for actives across many fields, including drugs and flavours. However, such tailoring can only be fully optimised by a fundamental characterisation of the way in which a drug, loaded into an FCC, then flows and diffuses out over a period of time to provide the delayed release.

 

It was found that adsorption on the FCC surface is selective, for example, saccharin does not become adsorbed from 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES) buffer solution, and neither does anethole from ethanol. FCC also does not adsorb the cationic probe benzyltrimethylammonium bromide (BTMAB) or the anionic probe sodium 2-naphthalenesulphonate (Na2NS). However, it was found that vanillin adsorbs onto the FCC in an amount of 2.00 ± 0.59 mg g^-1. Aspirin and vanillin adsorption from ethanolic solutions with various additions of water onto FCC TP was investigated and fitted with the Tóth isotherm. It was estimated that vanillin adsorbed onto around 17 %, and aspirin onto around 39 %, of the overall FCC TP surface area without the addition of any water. An equation was formulated in order to approximate the adsorption as a function of the FCC's surface coverage by the water. This is discussed in Chapter 4 and has also been published in a peer-reviewed academic journal (Levy et al., 2017)

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