TY  - JOUR
A1  - Bertz, Morten
A1  - Molinnus, Denise
A1  - Schöning, Michael Josef
A1  - Homma, Takayuki
T1  - Real-time monitoring of H₂O₂ sterilization on individual bacillus atrophaeus spores by optical sensing with trapping Raman spectroscopy
JF  - Chemosensors
N2  - Hydrogen peroxide (H₂O₂), a strong oxidizer, is a commonly used sterilization agent employed during aseptic food processing and medical applications. To assess the sterilization efficiency with H₂O₂, bacterial spores are common microbial systems due to their remarkable robustness against a wide variety of decontamination strategies. Despite their widespread use, there is, however, only little information about the detailed time-resolved mechanism underlying the oxidative spore death by H₂O₂. In this work, we investigate chemical and morphological changes of individual Bacillus atrophaeus spores undergoing oxidative damage using optical sensing with trapping Raman microscopy in real-time. The time-resolved experiments reveal that spore death involves two distinct phases: (i) an initial phase dominated by the fast release of dipicolinic acid (DPA), a major spore biomarker, which indicates the rupture of the spore’s core; and (ii) the oxidation of the remaining spore material resulting in the subsequent fragmentation of the spores’ coat. Simultaneous observation of the spore morphology by optical microscopy corroborates these mechanisms. The dependence of the onset of DPA release and the time constant of spore fragmentation on H₂O₂ shows that the formation of reactive oxygen species from H₂O₂ is the rate-limiting factor of oxidative spore death.
KW  - DPA (dipicolinic acid)
KW  - sterilization
KW  - Bacillus atrophaeus spores
KW  - optical trapping
KW  - Raman spectroscopy
KW  - optical sensor setup
Y1  - 2023
U6  - https://doi.org/10.3390/chemosensors11080445
SN  - 2227-9040
N1  - This article belongs to the Special Issue "Biosensors and Chemical Sensors for Food and Healthcare Monitoring—Celebrating the 10th Anniversary"
VL  - 8
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Engelmann, Ulrich M.
A1  - Simsek, Beril
A1  - Shalaby, Ahmed
A1  - Krause, Hans-Joachim
T1  - Key contributors to signal generation in frequency mixing magnetic detection (FMMD): an in silico study
JF  - Sensors
N2  - Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel–Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays.
KW  - key performance indicators
KW  - magnetic biosensing
KW  - coupled Néel–Brownian relaxation dynamics
KW  - frequency mixing magnetic detection
KW  - magnetic relaxation
KW  - micromagnetic simulation
KW  - magnetic nanoparticles
Y1  - 2024
U6  - https://doi.org/10.3390/s24061945
SN  - 1424-8220
N1  - This article belongs to the Special Issue "Advances in Magnetic Sensors and Their Applications"
VL  - 24
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Arida, Hassan A.
A1  - Al-Haddad, Ameera
A1  - Schöning, Michael Josef
T1  - New Solid-State Organic Membrane Based Lead-Selective Micro-Electrode
JF  - International Journal of Electrochemical Science. 6 (2011), H. 9
Y1  - 2011
SN  - 1452-3981
SP  - 3858
EP  - 3867
ER  - 
TY  - JOUR
A1  - Schöning, Michael Josef
A1  - Arzdorf, Michael
A1  - Mulchandani, P.
A1  - Chen, W.
A1  - Mulchandani, A.
T1  - Towards a capacitive enzyme sensor for direct determination of organophosphorus pesticides: Fundamentals studies and aspects of development
JF  - Sensors. 3 (2003), H. 6
Y1  - 2003
SN  - 1424-8220
SP  - 119
EP  - 127
ER  - 
TY  - JOUR
A1  - Schöning, Michael Josef
A1  - Arzdorf, Michael
A1  - Mulchandani, P.
A1  - Chen, W.
A1  - Mulchandani, A.
T1  - A capacitive field-effect sensor for the direct determination of organophosphorus pesticides
JF  - Sensors and Actuators B. 91 (2003), H. 1-3
Y1  - 2003
SN  - 0925-4005
SP  - 92
EP  - 97
ER  -