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Biomedical Sensing Applications of Microspherical Resonators
Published in Giancarlo C. Righini, Glass Micro- and Nanospheres, 2019
Silvia Soria, Simone Berneschi, Andrea Barucci, Alessandro Cosci, Daniele Farnesi, Gualtiero Nunzi Conti, Stefano Pelli, Giancarlo C. Righini
Other authors have demonstrated that quantum dot-embedded microspheres could enhance up to five times the theoretical sensitivity [67]. Two-photon excited luminescence improved the detection of WGM by localization. In bulk refractometric measurements the authors detected changes of 2.5 × 104 RIU, five times greater than the calculated sensitivity. In nonspecific sensing of protein layers (bovine serum albumin and thrombin) adsorbed to the Q-dot microsphere, the enhancement was almost three times [68]; in this case, however, the authors did not use two photon excitation of the luminescence of the CdSe/ZnS Q dots. Very recently, a new absolute WGM-based sensing method has been proposed that does not require calibration, reference measurements or any prior knowledge about the microsphere radius [69]; only one spectrum acquisition per fluorescent microsphere is needed. The authors proposed the use of commercially available free-floating functionalized fluorescent microspheres, thus reducing significantly the sample preparation. The proposed analyte was constituted by elongated spores of Bacillus atrophaeus subsp. Golbigii (B. golbigii), which is well known as a surrogate organism for pathogenic B. anthracis. The authors used two different parameters, i.e., the apparent refractive index and the calculated mean TE-TM mode spacing, for successful detection of the spores.
Sterilization Methods
Published in Jeanne Moldenhauer, Disinfection and Decontamination, 2018
The key factors to consider in the effectiveness of the sterilization cycle are: concentration of the sterilant and temperature although the pH, extent of mixing (if used), and soil (cells or cellular debris) may also be important. During validation it is common to use Bacillus atrophaeus ATCC 9372 or Bacillus subtilis ATCC 6633 as the biological indicator, since they are representative of worst case bioburden isolates. The indicators are directly inoculated upon the surface to be sterilized. Placement of the biological indicators should be determined by evaluating the most difficult areas for the sterilant to reach (USP<1229.6>, 2013b; Moldenhauer, 2014).
Biological Contamination Control and Planetary Protection Measures as Applied to Sample Acquisition
Published in Yoseph Bar-Cohen, Kris Zacny, Advances in Extraterrestrial Drilling, 2020
James N. Benardini, Moogega Stricker, Kasthuri J. Venkateswaran
Heat microbial reduction is the most widely used and the most well understood of all the hardware microbial reduction methods. The heat microbial specifications were originally developed from the food industry and further applied to various microbial reduction and sterilization applications in not only the food industry but the medical device industry as well (Otterbein & Pflug, 2010). For applicability to spacecraft use, NASA conducted an extensive heat microbial reduction materials compatibility assessment for the Viking lander program, establishing Bacillus pumilus var niger (now B. atrophaeus) as the standard biological challenge organism. As part of the Viking studies, a series of low-abundance environmental organisms that were even more “hardy” than the standard were identified (Puleo et al., 1978). In the early 2000s NASA and ESA undertook a study on a new “hardy” biological challenge standard, Bacillus strain ATCC 29669, as this was a spacecraft assembly facility-associated isolate that exhibited a hardier heat resistance profile as compared to the industry standard of Bacillus atrophaeus ATCC 9372 (Schubert and Beaudet, 2001). The hardier isolate testing revised the NASA and ESA microbial heat standards and are currently captured in the ESA PP standards (ECSS-Q-ST-70-57C, 2013). NASA has also adopted these standards and is currently updating documentation. InSight, Mars 2020, and the Europa Clipper missions utilize the new heat microbial reduction specifications. For the application of heat microbial reduction, there are multiple curves that take into account hardy and non-hardy microbial populations. The implementation of heat microbial reduction includes heat in the range of 110°C–200°C and specification factors to account for free surfaces, mated surfaces, and embedded microorganisms in non-metallic materials.
Inactivation of Bacterial Spores on Polystyrene Substrates Pre-exposed to Dry Gaseous Ozone: Mechanisms and Limitations of the Process
Published in Ozone: Science & Engineering, 2021
Pierre Levif, Sylvie Larocque, Jacynthe Séguin, Michel Moisan, Jean Barbeau
Bacillus atrophaeus spores were employed as bio-indicators because the sporulated form of the bacterium is highly resistant to various biocidal agents such as desiccation, radiation and heat whereas vegetative bacteria are much easier to inactivate. Bacillus atrophaeus spores ATCC® 9372 are currently used to validate the efficiency of sterilization procedures (Craik et al. 2002; Young and Setlow 2004). A working stock of spores was prepared, as previously described (Mahfoudh et al. 2010a) and kept at 4 °C.