Rapid, culture-independent, optical diagnostics of centrifugally captured bacteria from urine samples

Abstract

This work presents a polymeric centrifugal microfluidic platform for the rapid and sensitive identification of bacteria directly from urine, thus eliminating timeconsuming cultivation steps. This "Lab-on-a-Disc" platform utilizes the rotationally induced centrifugal field to efficiently capture bacteria directly from suspension within a glass-polymer hybrid chip. Once trapped in an array of small V-shaped structures, the bacteria are readily available for spectroscopic characterization, such as Raman spectroscopic fingerprinting, providing valuable information on the characteristics of the captured bacteria. Utilising fluorescence microscopy, quantification of the bacterial load has been achieved for concentrations above 2 Â 10 À7 cells ml À1 within a 4 ll sample. As a pilot application, we characterize urine samples from patients with urinary tract infections. Following minimal sample preparation, Raman spectra of the bacteria are recorded following centrifugal capture in stopped-flow sedimentation mode. Utilizing advanced analysis algorithms, including extended multiplicative scattering correction, high-quality Raman spectra of different pathogens, such as Escherichia coli or Enterococcus faecalis, are obtained from the analyzed patient samples. The whole procedure, including sample preparation, requires about 1 h to obtain a valuable result, marking a significant reduction in diagnosis time when compared to the 24 h and more typically required for standard microbiological methods. As this cost-efficient centrifugal cartridge can be operated using low-complexity, widely automated instrumentation, while providing valuable bacterial identification in urine samples in a greatly reduced time-period, our opto-microfluidic Lab-on-a-Disc device demonstrates great potential for nextgeneration patient diagnostics at the of point-of-care. V C 2015 AIP Publishing LLC.

The application of Raman spectroscopy for the detection and identification of microorganisms

“…In yet another recent study, a budget‐friendly ‘Lab‐on‐a‐Disc’ platform was developed and employed to capture and analyze bacteria from patients' urine samples without prior cultivation steps in under 70 min . Here, the characterization of the captured germs comprised not only the label‐free Raman microspectroscopy but also fluorescence measurements, which can serve as a basis for future microfluidics‐based immunochemical assays.…”

Point-of-Care Diagnostics: Recent Developments in a Connected Age

“…For instance, a centrifugal microfluidic device was built for detection of bacteria in urine samples 104 . The detection method was Raman spectroscopy, performed on a fluorescent microscope for imaging and subsequent Raman spectroscopic fingerprinting 104 . In another advance, a microfluidic chip was developed for thrombosis detection from whole blood 105 .…”

A Review of Biomedical Centrifugal Microfluidic Platforms

“…These particles were then sedimented through a density-media and were quantified by laser-induced fluorescence [ 149 ]. Schroder et al presented a LOAD platform for rapid and sensitive detection of bacteria from urine [ 150 ], while Kim et al used their LOAD system for on-site quantification of microalgal lipids [ 151 ].…”