Optical design for laser tweezers Raman spectroscopy setups for increased sensitivity and flexible spatial detection

Robinson

et al. 2022

Preprint

Self Cite

Bacterial spores are highly resistant to heat, radiation, and various disinfection chemicals. These impacts on the biophysical and physicochemical properties of spores can be studied on the single-cell level using optical tweezers. However, the effect of the trapping laser on spores germination rate is not fully understood. In this work, we assess the impact of 1064 nm laser light on the germination of Bacillus thuringiensis spores. The results show that the germination rate of spores after laser exposure follows a sigmoid dose-response relationship, with only 15 percent of spores germinating after 20 J of laser light. Under anaerobic growth conditions, the percentage of germinating spores at 20 J increased to 65 percent. The results thereby indicate that molecular oxygen is a major contributor to the germination-inhibiting effect observed. Thus, our study highlights the risk for optical trapping of spores and ways to mitigate it.

Section: Experimental Methodsmentioning

confidence: 99%

Reactive oxygen species generated by infrared laser light in optical tweezers inhibits the germination of bacterial spores

Robinson

et al. 2022

Preprint

Self Cite

“…The laser system used is part of the optical tweezers (laser tweezers) Raman spectroscopy system previously described in References [28][29][30]. Briefly, a diodepumped Gaussian continuous wavelength laser (Rumba, 05-01 Series, Cobolt AB) operating at 1064 nm is coupled into the microscope using a dichroic shortpass mirror with a cut off wavelength of 650 nm.…”

Section: Laser System and Microscopementioning

confidence: 99%

Reactive oxygen species generated by infrared laser light in optical tweezers inhibits the germination of bacterial spores

Robinson

Journal of Biophotonics

et al. 2022

Self Cite

Bacterial spores are highly resistant to heat, radiation and various disinfection chemicals. The impact of these on the biophysical and physicochemical properties of spores can be studied on the single‐cell level using optical tweezers. However, the effect of the trapping laser on spores' germination rate is not fully understood. In this work, we assess the impact of 1064 nm laser light on the germination of Bacillus thuringiensis spores. The results show that the germination rate of spores after laser exposure follows a sigmoid dose‐response relationship, with only 15% of spores germinating after 20 J of laser light. Under anaerobic growth conditions, the percentage of germinating spores at 20 J increased to 65%. The results thereby indicate that molecular oxygen is a major contributor to the germination‐inhibiting effect observed. Thus, our study highlights the risk for optical trapping of spores and ways to mitigate it.

“…Further, to increase the signal-to-noise ratio, we have mounted a 150 m diameter pinhole in the focal point of the telescope. The filtered light is coupled into our spectrometer (Model 207, McPherson) through a 150 m wide entrance slit where a 600 grooves/mm holographic grating disperses the light 22 . The Raman spectrum was then…”

Section: Experimental Setup and Measurement Proceduresmentioning

confidence: 99%

Reference Raman Spectrum and Mapping of Cryptosporidium parvum Oocysts

Dahlberg

et al. 2022

Preprint

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Cryptosporidium parvum is a protozoan parasite and among the most infectious diarrhea-causing pathogens, leading to severe health problems for malnourished children and immunocompromised individuals. Outbreaks are common even in developed countries, originating from water or food contamination and resulting in suffering and large costs for society. Therefore, robust, fast and highly specific detection strategies of Cryptosporidium are needed. Label-free detection techniques such as Raman spectroscopy have been suggested, however high-resolution reported spectra in the literature are limited. In this work, we report reference Raman spectra at 3 cm^{-1} resolution for viable and inactivated Cryptosporidium oocysts of the species C. parvum, gathered at a single oocyst level using a laser tweezers Raman spectroscopy system. We furthermore provide tentative Raman peak assignments for the Cryptosporidium oocysts, along with Raman mapping of the oocysts' heterogeneous internal structure. Finally, we compare the C. parvum Raman spectrum with other common enterotoxigenic pathogens: Escherichia coli, Vibrio cholerae, Bacillus cereus and Clostridium difficile. Our results show a significant difference between C. parvum Raman spectra and the other pathogens.