An investment of $1.3 million from the Federal Economic Development Agency for Southern Ontario is helping P&P Optica Inc. (Kitchener, Canada) develop "near-instantaneous" blood analysis instruments for the point-of-care medical market. In partnership with ELCAN Optical Technologies, P&P will pursue a reagent-free instrument based on P&P's non-scanning optical spectrometers with gel gratings.
"The standard suite of blood testing requires a handful of vials and several days of waiting," says Rob McAleer, VP Business Development with P&P. "Now imagine getting your blood tested while you wait in the doctor's office from a single small sample of blood." Or, says McAleer, "imagine you are a healthcare provider and you are able to reduce both the cost and wait of blood testing by over 80%." That is what P&P is planning.
Right for bio
The technique calls on the high sensitivity and low noise of P&P's spectrometers, which collect spectral information in a single exposure. According to P&P, the 100,000:1 signal-to-noise ratio (SNR) of the proprietary technology provides a sensitivity improvement of about 20 times over the closest competing technology.
Initial studies show that with minimal sample processing (treatment only with anti-coagulants), each of 15 analytes can be measured within a single, centrifuged, 1cc test tube of blood. Without a high-performance spectrometer, only a few components of blood can be detected. But high-sensitivity instrumentation provides rich data from which it is possible to extract information about difficult-to-measure compounds, such as blood.
Hematology applications of spectroscopy require careful measurement of a "training set" of blood samples. A mathematical multivariate model is constructed for individual components; the model is later used to evaluate unknown concentrations. Achieving results within acceptable error levels requires high-quality data for both training and analysis.
P&P Optica instruments cover the spectral range from 250 to 2500 nm, are capable of measuring both broadband and Raman spectra, and provide both multichannel and high-throughput modes for detection of signals previously considered undetectable by non-scanning optical systems. Because the spectrometer has no moving parts, it acquires its entire signal simultaneously for all colors—which is crucial for the measurement of biological systems and sensitive samples that change under observation and, thus, can affect signals obtained via scanning.
The spectrometer is built around transmission-based volume phase holographic (VPH) gratings (a.k.a. gel gratings), which enable much higher optical throughput than is typical. Compared to etched or ruled gratings, VPH gratings typically produce far less scattering. And their diffraction efficiency depends on a greater number of factors, including gel thickness, refractive index, the modulation depth of the refractive index, and the distribution of refraction index across the gel layer. This enables design of a grating with much higher efficiency and lower polarization dependency. When a sufficiently thick layer of gel is used, VPH diffraction gratings can reach close to 100% efficiency, even for high spatial frequencies. And because of the way they are made, a single gel layer can register more than one grating.
A comparison of the P&P setup with a Czerny-Turner reflective grating spectrometer for a standoff LIBS measurement application showed that the former provided a 363% SNR improvement and a 1,445% increase in throughput.1
In addition to the blood analysis system, P&P Optica is working with various partners on other biomedical initiatives, including broadband trans-illumination for breast cancer risk assessment, second and third harmonic functional and structural imaging of cancer cells, and high-resolution OCT imaging of the eye (an NIR version enables deeper penetration).
- Applied Optics, Vol. 49 Issue 13, pp. C200-C210 (2010)