Dynamic Measurement of Nanoflows: Realization of an Optofluidic Flow Meter to the Nanoliter-per-Minute Scale.

The ultimate performance of flow-based measurements in microfluidic systems is currently limited by their accuracy at the nanoliter-per-minute scale. Improving such measurements (especially in contexts that require continuous monitoring) is challenging because of constraints associated with shrinking system geometries and limitations imposed by making precise measurements of smaller quantities in real time. A particularly interesting limit is the relative uncertainty as flow approaches zero, which diverges for most measurement methods. To address these problems, we have developed an optofluidic measurement system that can deliver and record light in a precise interrogation region of a microfluidic channel. The system utilizes photobleaching of fluorophore dyes in the bulk flow and can identify zero flow to better than 1 nL/min absolute accuracy. The technique also provides an independent method for determining nonzero flow rates based on a robust scaling relationship between the fluorescence emission and flow. Together, these two independent approaches enable precise measurement of flow to within 5% accuracy down to 10 nL/min and validation of flow control to within 5% uncertainty down to 2 nL/min. We also demonstrate that our technique can be used to extend a calibrated flow meter well below its specified range (e.g., 500 nL/min) and to make dynamic measurements of similar relative uncertainties to the calibrated meter, which would have otherwise expanded significantly in this regime.

Brain tumour differentiation: rapid stratified serum diagnostics via attenuated total reflection Fourier-transform infrared spectroscopy.

The ability to diagnose cancer rapidly with high sensitivity and specificity is essential to exploit advances in new treatments to lead significant reductions in mortality and morbidity. Current cancer diagnostic tests observing tissue architecture and specific protein expression for specific cancers suffer from inter-observer variability, poor detection rates and occur when the patient is symptomatic. A new method for the detection of cancer using 1 µl of human serum, attenuated total reflection-Fourier transform infrared spectroscopy and pattern recognition algorithms is reported using a 433 patient dataset (3897 spectra). To the best of our knowledge, we present the largest study on serum mid-infrared spectroscopy for cancer research. We achieve optimum sensitivities and specificities using a Radial Basis Function Support Vector Machine of between 80.0 and 100 % for all strata and identify the major spectral features, hence biochemical components, responsible for the discrimination within each stratum. We assess feature fed-SVM analysis for our cancer versus non-cancer model and achieve 91.5 and 83.0 % sensitivity and specificity respectively. We demonstrate the use of infrared light to provide a spectral signature from human serum to detect, for the first time, cancer versus non-cancer, metastatic cancer versus organ confined, brain cancer severity and the organ of origin of metastatic disease from the same sample enabling stratified diagnostics depending upon the clinical question asked.

Vibrational spectroscopic methods for cytology and cellular research.

The use of vibrational spectroscopy, FTIR and Raman, for cytology and cellular research has the potential to revolutionise the approach to cellular analysis. Vibrational spectroscopy is non-destructive, simple to operate and provides direct information. Importantly it does not require expensive exogenous labels that may affect the chemistry of the cell under analysis. In addition, the advent of spectroscopic microscopes provides the ability to image cells and acquire spectra with a subcellular resolution. This introductory review focuses on recent developments within this fast paced field and highlights potential for the future use of FTIR and Raman spectroscopy. We particularly focus on the development of live cell research and the new technologies and methodologies that have enabled this.

Investigating the rapid diagnosis of gliomas from serum samples using infrared spectroscopy and cytokine and angiogenesis factors.

The ability to diagnose brain cancer rapidly from serum samples is of great interest; such a diagnosis would allow for rapid testing and time to results providing a responsive diagnostic environment, ability to monitor treatment efficacy, early detection of recurrent tumours and screening techniques. Current methods rely upon subjective, time-consuming tests such as histological grading and are particularly invasive with the diagnostic test requiring hospitalisation of 2-3 days. A rapid diagnostic method based upon serum samples would allow for a relatively non-invasive test and open up the possibility of screening for brain cancer. We report for the first time the use of a Bioplex immunoassay to provide cytokine and angiogenesis factor levels that differ between serum from glioma and non-cancer patients specifically angiopoietin, follistatin, HGF, IL-8, leptin, PDGF-BB and PECAM-1 providing sensitivities and specificities as high as 88 % and 81 %, respectively. We also report, for the first time, the use of serum ATR-FTIR combined with a RBF SVM for the diagnosis of gliomas from non-cancer patients with sensitivities and specificities as high as 87.5 % and 100 %, respectively. We describe the combination of these techniques in an orthogonal diagnostic regime, providing strength to the diagnosis through data combinations, in a rapid diagnostic test within 5 h from serum collection (10 min for ATR-FTIR and 4 h for the Bioplex Immunoassay). This regime has the ability to revolutionise the clinical environment by providing objective measures for diagnosis allowing for increased efficiency with corresponding decreases in mortality, morbidity and economic impact upon the health services.

Rapid discrimination of maggots utilising ATR-FTIR spectroscopy.

Entomological evidence is used in forensic investigations to indicate time since death. The species and age of maggots or flies that are present at the scene can be used when estimating how much time has passed since death. Current methods that are used to identify species and developmental stage of larvae and fly samples are highly subjective, costly and often time consuming processes and require the expertise of an entomologist or species identification via DNA analysis. The use of vibrational spectroscopy, as an alternative identification method, would allow for a quicker, cheaper and less subjective technique and would allow entomological evidence to be used more commonly in the forensic process. This proof of principle study shows the potential for using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) as a rapid tool for differentiating between various species of larvae, such as those commonly found at crime scenes. The proposed regime would provide a rapid and valuable tool resulting in reduced time for both species identification and life cycle determination, particularly in forensic situations.

Attenuated total reflection fourier transform infrared (ATR-FTIR) spectral discrimination of brain tumour severity from serum samples.

Gliomas are the most frequent primary brain tumours in adults with over 9,000 people diagnosed each year in the UK. A rapid, reagent-free and cost-effective diagnostic regime using serum spectroscopy would allow for rapid diagnostic results and for swift treatment planning and monitoring within the clinical environment. We report the use of ATR-FTIR spectral data combined with a RBF-SVM for the diagnosis of gliomas (high-grade and low-grade) from non-cancer with sensitivities and specificities on average of 93.75 and 96.53% respectively. The proposed diagnostic regime has the ability to reduce mortality and morbidity rates.