A novel marker design for magnetic marker monitoring in the human gastrointestinal tract

Application of In Vivo MRI Imaging to Track a Coated Capsule and Its Disintegration in the Gastrointestinal Tract in Human Volunteers

Oral specially coated formulations have the potential to improve treatment outcomes of a range of diseases in distal intestinal tract whilst limiting systemic drug absorption and adverse effects. Their development is challenging, partly because of limited knowledge of the physiological and pathological distal gastrointestinal factors, including colonic chyme fluid distribution and motor function. Recently, non-invasive techniques such as magnetic resonance imaging (MRI) have started to provide novel important insights. In this feasibility study, we formulated a coated capsule consisting of a hydroxypropyl methylcellulose (HPMC) shell, coated with a synthetic polymer based on polymethacrylate-based copolymer (Eudragit®) that can withstand the upper gastrointestinal tract conditions. The capsule was filled with olive oil as MRI-visible marker fluid. This allowed us to test the ability of MRI to track such a coated capsule in the gastrointestinal tract and to assess whether it is possible to image its loss of integrity by exploiting the ability of MRI to image fat and water separately and in combination. Ten healthy participants were administered capsules with varying amounts of coating and underwent MRI imaging of the gastrointestinal tract at 45 min intervals. The results indicate that it is feasible to track the capsules present in the gastrointestinal tract at different locations, as they were detected in all 10 participants. By the 360 min endpoint of the study, in nine participants the capsules were imaged in the small bowel, in eight participants in the terminal ileum, and in four in the colon. Loss of capsule integrity was observed in eight participants, occurring predominantly in distal intestinal regions. The data indicate that the described approach could be applied to assess performance of oral formulations in undisturbed distal gastrointestinal regions, without the need for ionizing radiation or contrast agents.

Dissolution of magnetically marked tablets: investigations in a physical phantom

Pharmacological research is strongly driven by maximizing the bioavailability of new pharmaceuticals. For orally applied drugs the bioavailability highly depends on the process of dissolution in the gastrointestinal tract and is affected by numerous physiological and environmental factors. Available techniques for in vivo monitoring of the dissolution process are very limited and not applicable for large studies. The technique of magnetic marker monitoring provides new prospects for these investigations. However, it is currently limited due to low fields common magnetic markers produce. Hence, only highly sensitive sensors are applicable. In this paper, we performed dissolution tests of novel markers in a physical phantom with magnetoresistive sensors in an unshielded environment. The markers were continuously localized and the movement through the phantom was tracked. By analyzing the changing magnetic moment of the markers we were able to monitor the progress of dissolution in the phantom. We conclude that our proposed phantom and tracking technique is an important step towards new systems for in vivo monitoring of pharmaceutical dissolution processes.