Biomagnetic Methods: Technologies Applied to Pharmaceutical Research

Abstract

Biomagnetic methods have been designed for a wide range of applications. Recently, such methods have been proposed as alternatives to scintigraphy for evaluating of a number of pharmaceutical processes in vitro as well as under the influence of gastrointestinal physiological parameters. In this review, physical characterization as well as the most recent applications of Superconducting Quantum Interference Device (SQUID), Anisotropic Magnetoresistive (AMR) and AC Biosusceptometry (ACB) in the pharmaceutical research will be explored. Moreover, their current status and how these technologies can be employed to improve the knowledge about the impact of gastrointestinal physiology on drug delivery in association with pharmacokinetic outcomes, termed pharmacomagnetography, will be presented.

Employment of a noninvasive magnetic method for evaluation of gastrointestinal transit in rats

“…Such investigations are performed employing radiolabeled meals; however the costs, radiation exposure, licensing for handling radioactive materials and approval by appropriate institutional committee as well as limited temporal and spatial resolution are some of the drawbacks of this technique, especially when considering animal studies [9,10]. Breath hydrogen test is a noninvasive technique that was utilized in some animal studies despite of serious pitfalls in data interpretation [2,11].…”

Dissolution testing of oral modified-release dosage forms

“…Whereas the earliest methods of GI monitoring, such as traditional X-ray methods using radioopaque markers, [10] are nowadays rarely used, methods such as gamma scintigraphy [13][14][15][16] and several magnetictracking techniques, such as magnetic marker monitoring (MMM), magnetic moment imaging (MMI), alternate current biosusceptometry (ACB) and magnetic resonance imaging (MRI), are all currently in use for this purpose. [17][18][19] Moreover, the whole-gut transit can nowadays also be assessed with a wireless capsule monitoring system. [20] Through the use of these techniques, we nowadays know that independent of the nature of the formulation, GI transport is rather a discontinuous than a continuous process, [21] that there is also not necessarily a continuous phase of free fluid available in the gut lumen [18] and that the intraluminal conditions are strongly affected by food intake.…”

Development of an AMR-ACB Array for Gastrointestinal Motility Studies

“…The excitation coil operates with a frequency of 10 kHz to provide low offset and high sensitivity as well as to avoid significant eddy current effects produced by biological tissue in the presence of the electrically conductive fluids. In this system, a current of 15 mA is needed to generate a magnetic field of 2 mT (measured in the center of excitation coil) which induces magnetic flux in the detection coils [5].…”

“…These sensors are composed of pairs of detection and excitation coils in a first-order gradiometric configuration to provide good signal-to-noise ratio. Considering their features, AMR sensors can detect constant and time-varying magnetic fields [7], [13], [14], while ACB sensors are able to measure alternating magnetic field and to monitor ferromagnetic particles that were not previously magnetized [5], [11], [12]. The association between AMR and ACB consists of replacing the ACB detection coils by AMR sensors.…”

“…Ideally when no magnetic material is close to this arrangement, the current I e in the excitation coils generates a voltage in each coil that is canceled by the gradiometric configuration. Only the signal from the ferromagnetic source coupled to the coil is detected as the difference of inductance M. (Modified from[5].)Fig. 2.…”