The field of biomarker detection is constantly in search of novel methods to improve speed of detection, measurement accuracy, lower detection limits, specificity and applicability in mobile settings without the need for trained personnel. Most existent techniques like microbiological analysis, cell culturing, but also more novel techniques with electrical readouts suffer from either slow response time, are expensive or need well-trained operators. Very fast response lateral flow assays on the other hand, often show false negative results due to a lack of specificity. Furthermore, a plethora of, e.g., fluorescence-based techniques cannot be used in turbid samples like waste water or blood and require excessive sample pre-treatment. The global covid pandemic and the German Ahrtal flooding in 2021 are just some vivid examples of quickly evolving outbreaks and disasters of our time. Such crisis scenarios have taught us once and again that quick, safe and mobile Point of Care Testing (PoCT) is needed. For biomarker detection, the Frequency Mixing Magnetic Detection (FMMD) technology provides a useful combination of advantages with its very high specificity, fast response times and mobile applicability. FMMD relies on the utilization of magnetic nanoparticles (MNPs) bound to the analyte of interest as magnetic markers which further provides highly selective signal acquisition. The readout of the magnetic particle signal in this magnetic immunoassay (MIA)upon application of two distinct magnetic excitation fields others potential for multiplexed signal acquisition. However, the requirements in actual disaster situations go further than the 'potential benefits' of a technology. Applicability and accuracy despite harsh conditions outside the lab, very low susceptibility to errors by untrained users and low false negatives rates are crucial for on-site decision making and rapid detection of for example a pathogen. FMMD is sensitive to changes in temperature due to the signal-dependency on a biological reaction, the magnetization behavior of the magnetic markers and the ohmic resistance of the miniaturized induction coil environment. Consequently, we mimic in-field rather than lab-based conditions to investigate the thermal dependencies of different aspects of the FMMD signal acquisition. We found indication of diverse signal variation depending on constant ambient temperature level. Therefore, aiming at finding optimal input excitation signals for thermal stability and signal-invariability, we further propose a methodology to test these input and ambient influences computationally. Our 3-parametertransient model utilizes non-integer order Padé approximations to follow the thermal dynamics of the FMMD sensor unit. The incorporation of Joule heating feedback emphasizes physical significance of the model. A cross-identification with Finite Element Analysis (FEA) in COMSOL promises potential for thermal and electromagnetic property analysis and sensor design. Furthermore, it is possible to find low-frequency input schemes for the excitation fields of FMMD, that improve the accuracy of measuring biological probes while minimizing the measurement time. It also promises to reduce the error susceptibility for the magnetic reader user in terms of sample handling in PoCT and improves functionality in terms of sample preparation in the Measurement Head (MH).
Max Jessing (2026) studied this question.