On-Chip Photothermal Analyte Detection Using Integrated Luminescent Temperature Sensors

Abstract

Optical absorbance detection based on attenuated light transmission is limited in sensitivity due to short path lengths in microfluidic and other miniaturized platforms. An alternative is detection using the photothermal effect. Herein we introduce a new kind of photothermal absorbance measurement using integrated luminescent temperature sensor spots inside microfluidic channels. The temperature sensors were photopolymerized inside the channels from NOA 81 UV-curable thiolene prepolymer doped with a tris(1,10-phenanthroline)ruthenium(II) temperature probe. The polymerized sensing structures were as small as 26 ± 3 μm in diameter and displayed a temperature resolution of better than 0.3 K between 20 and 50 °C. The absorbance from 532 nm laser excitation of the food dye Amaranth as a model analyte was quantified using these spots, and the influence of the flow rate, laser power, and concentration was investigated. Calibration yielded a linear relationship between analyte concentration and the temperature signal in the channels. The limit of detection for the azo-dye Amaranth (E123) in this setup was 13 μM. A minimal detectable absorbance of 3.2 × 10 AU was obtained using an optical path length of 125 μm in this initial study. A microreactor with integrated temperature sensors was then employed for an absorbance-based miniaturized nitrite analysis, yielding a detection limit of 26 μM at a total assay time of only 75 s. This technique is very promising for sensitive, and potentially spatially resolved, optical absorbance detection on the micro- and nanoscale.

Review of ultrasensitive readout for micro-/nanofluidic devices by thermal lens microscopy

“…The non-radiative relaxation process allows the molecules to release the energy of photon as heat and the temperature rise is detected in diverse manners. [32][33][34][35] Typically, the temperature change is observed as a change in the refractive index through optical deflection, lensing, and various interferometric techniques. [36][37][38] In photoacoustic spectroscopy, a periodical change in density of the surrounding air is also detected as a sound wave.…”

Microelectromechanical Microsystems-Supported Photothermal Immunoassay for Point-of-Care Testing of Aflatoxin B1 in Foodstuff

“…Recently, it has been demonstrated that biosensing strategies based on target-triggered temperature changes may be more suitable for in situ testing of POC due to their low cost, high portability, and ease of implementation. − In general, the sensing strategies developed for photothermal sensing require the involvement of additional photothermal agents such as photothermal nanomaterials or dye molecules and structurally consist of an excitation light source and a temperature signal output device. Accompanied by the advancement of 3D additive technology and the development of near-infrared light source fabrication technology, the testing of small biological molecules in micro-compact photothermal transduction devices has been realized .…”

Integrated Photothermal‐Pyroelectric Biosensor for Rapid and Point‐of‐Care Diagnosis of Acute Myocardial Infarction: A Convergence of Theoretical Research and Commercialization

“…With the increased stress of modern life, acute myocardial infarction (AMI) has shown a trend toward younger age and has become an important global health problem in the last two photothermal-based temperature biosensing platforms are gaining momentum due to their naked eye discernible signal window and high portability. [18][19][20][21] In fact, photothermal imaging and sensing in small molecule detection relies on functional photothermal agents or bio-photothermal agents such as melanin or hemoglobin, which limit the further development of photothermal biosensors. In addition, limited by the inherent drawbacks of temperature testing devices, typically near-infrared cameras or thermometers, the independent temperature signal output is not sufficient for sensitive testing in low abundance proteins, which poses a new challenge for the construction of efficient sensitive bioassay platforms.…”