Low-Field Nuclear Magnetic Resonance Relaxometry – A Tool in Monitoring the Melting Transition of Polymeric Capsules with Applications in Drug Delivery

Polymeric micro and nanocapsules are often used as drug delivery systems. Their main advantage is that the active substances can be placed inside the capsule and released at the position of the diseased tissue or organ. The release can be performed gradually, owing to a continuous exchange process, eventually influenced by temperature, or suddenly as a consequence of melting the capsule wall. In the last case the determination of the melting transition temperature of the fabricated capsules is an important issue. In the present contribution we are showing that low field nuclear magnetic resonance (NMR) relaxometry can be used as a valuable tool in monitoring the melting transition of polymeric capsules prepared by an interfacial polymerization technique. The NMR relaxation experiments were performed at a proton resonance frequency of 20 MHz. The data were analyzed using a numerical Laplace inversion algorithm that allowed us the determination of the melting point for the fabricated capsules.