Optical biosensor system with integrated microfluidic sample preparation and TIRF based detection

Abstract

There is a steadily growing demand for miniaturized bioanalytical devices allowing for on-site or point-of-care detection of biomolecules or pathogens in applications like diagnostics, food testing, or environmental monitoring. These, so called labs-on-a-chip or micro-total analysis systems (µ-TAS) should ideally enable convenient sample-in -result-out type operation. Therefore, the entire process from sample preparation, metering, reagent incubation, etc. to detection should be performed on a single disposable device (on-chip). In the early days such devices were mainly fabricated using glass or silicon substrates and adapting established fabrication technologies from the electronics and semiconductor industry. More recently, the development focuses on the use of thermoplastic polymers as they allow for low-cost high volume fabrication of disposables. One of the most promising materials for the development of plastic based lab-on-achip systems are cyclic olefin polymers and copolymers (COP/COC) due to their excellent optical properties (high transparency and low autofluorescence) and ease of processing.We present a bioanalytical system for whole blood samples comprising a disposable plastic chip based on TIRF (total internal reflection fluorescence) optical detection. The chips were fabricated by compression moulding of COP and microfluidic channels were structured by hot embossing. These microfluidic structures integrate several sample pretreatment steps. These are the separation of erythrocytes, metering of sample volume using passive valves, and reagent incubation for competitive bioassays. The surface of the following optical detection zone is functionalized with specific capture probes in an array format. The plastic chips comprise dedicated structures for simple and effective coupling of excitation light from low-cost laser diodes. This enables TIRF excitation of fluorescently labeled probes selectively bound to detection spots at the microchannel surface. The fluorescence of these detection arrays is imaged using a simple set-up based on a digital consumer camera. Image processing for spot detection and intensity calculation is accomplished using customized software. Using this combined TIRF excitation and imaging based detection approach allowes for effective suppression of background fluorescence from the sample, multiplexed detection in an array format, as well as internal calibration and background correction.

Microfluidic-Based Approaches for Foodborne Pathogen Detection

“…Gilli et al designed a disposable plastic sensing device that utilized a total internal reflection fluorescence optical. There is no interference caused by non-specific binding or noise, and the microfluidic chip is connected with automated and sensitive customized software to realize the multiplex detection of the different targets [94].…”

Laser-induced fluorescence detection platform for point-of-care testing

“…Immediate and more frequent information gathered directly adjacent to the patient enables quicker diagnostics as well as more individual and harmonized therapy. To afford each patient an exclusive monitoring device in immediate vicinity to his bed, a POCT device facilitates a high-sensitive detection principle by miniaturization and, at the same time, drastically reduced monitoring costs compared to the use of large scale equipment in the central laboratory [1,2]. An ideal POCT device is small in size, not limited by noise, requires only small sample volumes and gives a linear response to the concentration of the analyte of interest.…”