This conference presentation was prepared for SPIE BiOS, 2023.

Although Raman spectroscopy has shown some promise for noninvasive glucose monitoring, the absence of the characteristic Raman peaks and true prospective prediction have been criticized. Here, we present experimental data that may finalize the long debate. We present the results of direct observation of glucose-specific Raman peaks in swine glucose clamping experiments. From the measured spectra, we confirm the presence of the glucose signal and the linearity between intensities of the glucose Raman peaks and the reference glucose concentrations. Prospective prediction was achieved by simply tracking glucose Raman peak intensities.

We suggest a method to monitor dehydration status using the change of albumin concentration measured from short wavelength infrared (SWIR) in-vivo spectrum. Absorption spectra were measured on swine skin using Fourier transform infrared spectroscopy based system, while dehydration and rehydration of the swine subject were induced by intravenous infusion of mannitol and saline solutions, respectively. The effective water path length and the amount of albumin absorption were regressed from the measured skin spectrum. Then, albumin concentration was acquired by normalizing albumin absorption by water path length. Experimental results showed that albumin concentration increases during dehydration period and decreases during rehydration period, which indicates the possibility of SWIR spectroscopy as a means for optical hydration status monitoring.

Esophageal pressure, bile content and pH in the gastroesophageal apparatus are important parameters to be monitored in gastroesophageal diseases. An all-optical device was developed for their simultaneous measurement and utilizes a catheter where plastic optical fibres for the measurement of bile and pH and a glass fibre with FBGs for pressure monitoring are integrated. The interrogation device contains two different modules: one for the pressure monitoring based on the measurement of the wavelength shift of the grating peaks, and the other one for bile and pH measurement, based on absorption changes caused by the esophageal content.

Capillary refill time (CRT) is used to assess circulatory status in the pediatric emergency department patient. It is recommended by the World Health Organization and is part of the Pediatric Early Warning Score. Current manual assessment methods show high inter-observer variability. Assessment of CRT using polarized reflectance imaging could eliminate this problem and improve the reliability. A Canon EOS M100 camera was used to obtain videos (50 fps) of CRT tests from 15 pediatric emergency patients aged ≤ 6, with a variety of chief complaints. The system was easy to use, well tolerated and produced highly consistent assessments of CRT.

The purpose of this study is to investigate the effects of external factors – including environmental conditions (e.g., ambient temperature, ambient relative humidity), and deployment parameters (e.g., working distance, viewing angle, setting temperature of external temperature reference source (ETRS)) – on the use of infrared thermographs (IRTs) for elevated body temperature (EBT) detection. These effects were theoretically evaluated through computer simulation and experimentally evaluated through bench tests. Overall, the insights into the influence of these factors provided by this study may improve IRT performance and thus enhance the potential of IRTs as countermeasures for high-quality point-of-care EBT screening.

The optimal design and development of multispectral cameras could potentially improve the diagnosis of esophageal and colon cancer during routine screening and surveillance programs. We used an open-source Python toolbox Opti-MSFA and spectral data from clinical studies to determine the optimal spectral bands for inclusion in a snap-shot multispectral imaging system based on multispectral filter arrays (MSFAs) atop a CMOS image sensor. We emulated the feasibility of the proposed optimization method via synthetic datasets, which shows that the optimized MSFAs allow the accurate spectral unmixing of blood oxygen levels. The next steps are to implement the spectral imaging system with optimized MSFAs and demonstrate that the selected spectral bands are versatile in clinical trials.

For the industrialization of Point-of-care applications, the miniaturization of diagnostic microscopes maintaining their performance for a reasonable pricing and a fast time-to-market are the biggest challenges. Providing application-tailored digital microscope subsystems for integration into next-generation devices, they have to meet the needs for image quality, automation and digitalization. With the invention of JENOPTIK SYIONS as a platform for many different applications (E.g. fluorescence, bright field, dark-field, Raman microscopy) a concept is proven to be reliable and flexible on, e.g. size, application-dependent target resolutions or needed field-of views.

Here we present a point-of-care biosensor for the diagnosis and quantification of SARS-CoV-2 using a simple agglutination assay, portable lens-free holographic microscopy, and machine learning. We achieve a sensitivity near that of traditional PCR methods within 3 hours and with a simple 1- or 2-step assay. This sensor is capable of quantifying complex samples consisting of large viral particles and cell debris through its machine learning algorithm, implicating its use as an assay for similarly complex human samples.

A fluorescence-based device was developed for immunosuppressants. A measuring chip with ten parallel microchannels allows the simultaneous detection of more than one analyte with replicate measurements. The device is equipped with a microfluidic circuitry, which handles the sample mixing with necessary chemicals using an additional chip and its pumping into the measuring chip, and with integrated thin-film amorphous silicon photodiodes for the fluorescence detection. Submicrometric fluorescent magnetic particles are used to improve the efficiency of the assay. Results on the measurements of mycophenolic acid and cyclosporine A in both spiked solutions and microdialysate samples from patient blood are reported.

We demonstrate a compact interrogation method for resonance-based biosensors, based on an integrated photonic chip with an array of resonant-cavity enhanced photodetectors. Due to the high signal-to-noise ratio, wavelength shifts in the 10 pm range can be measured, orders of magnitude smaller than the sensor and interrogator linewidths. This approach allows the read-out of resonance-based optical biosensors with simple integrated components, potentially enabling compact and low-cost sensing systems for point-of-care diagnostics.

This conference presentation was prepared for the Optical Diagnostics and Sensing XXIII: Toward Point-of-Care Diagnostics conference at SPIE BiOS, 2023.

This conference presentation was prepared for the Optical Diagnostics and Sensing XXIII: Toward Point-of-Care Diagnostics conference at SPIE BiOS, 2023.