The entire serial process for microalgal lipid quantification was integrated on the lab-on-a-disc platform. Schematic illustration of (A) absorbance detection setup for lab-on-a-disc,20 (B) the total internal reflection for absorbance measurements in lab-on-a-disc,21 (C) paired emitter detector diode (PEDD) ) device for absorbance detection in lab -on-a-disc.
Introduction
Microfluidics
- Microfluidics in biofuel quantification
- Microfluidics in food antioxidants determination
- Absorbance detection in microfluidics
A subsequent V-groove deflected the light beam out of the disc plane to the optical detector. In the lab-on-a-disc platform, there has also been research to increase the optical path length.
Lab-on-a-disc
- Basic principle of lab-on-a-disc system
- Lab-on-a-disc functions
- Lab-on-a-disc application in biomedical field
- Lab-on-a-disc application in other fields
The core of the disk lab operation platform consists of (1) centrifugal pumping, (2) valves, (3) measurement, (4) mixing, and (5) detection. The valve is used to control the flow of fluid in the lab-on-disk system.
Research motivations
Research aims
Microalgal lipid quantification using lab-on-a-disc
Introduction
Previous studies of microalgal lipid quantification on microfluidics
Centrifugal microfluidic platform was first introduced by Oak Ridge National Labs (ORNL) in the 1960s and further developed by Gamera12, 114 as an advanced sample-to-response system. As shown in recent comprehensive reviews11, 86, lab-on-a-disc has been actively used for various biomedical purposes, such as automated blood analysis, immunoassays, and disease diagnostics.2, 87, 115. In our previous example studies, the format used centrifugal pumping power and valves controlled by remote laser actuation.13 In principle, the centrifugal microfluidic technology can be extended to energy and environmental studies5 for rapid in situ monitoring of microalgal lipid production by facilitating serial lipid extraction in organic solvents and quantification processes.116.
Here, we developed a rapid and fully automated in situ method for the quantification of microalgal lipids. The method is an intensified procedure that includes pre-concentration and lysis of wet cells, extraction and optical detection of lipids using a lab-on-a-disk device that is tolerant to organic solvents (n-hexane and ethanol).
Development of essential techniques
- n-Hexane solvent resistive lab-on-a-disc platform
We expect that our new lab-on-a-disc platform can be applied to more applications requiring compatibility with organic solvents.
A fully integrated lab-on-a-disc for microalgal lipid quantification
- Experimental details
- Result and discussion
- Conclusions
Lab-on-a-disc for simultaneous determination of total phenolic content and antioxidant activity of beverage samples. Experimental design for the simultaneous determination of total phenolic content and antioxidant activity using three colorimetric reactions on a laboratory-on-a-disk apparatus. Spin program used for total phenolic content detection and antioxidant activity detection in our laboratory-on-a-disc.
The analytical characteristics of the lab-on-a-disc method for determining total phenolic content (FC method) and antioxidant activity (DPPH and FRAP) are shown in Table 3.4. Application of lab-on-disc for analysis of total phenolic content and antioxidant activity in three types of beverages (tea, juice and alcoholic beverages). Analytical feature of the lab-on-a-disc method for determination of total phenolic content (FC method) and antioxidant activity (DPPH and FRAP).
Fully integrated lab-on-a-disc for determination of natural antioxidants from
Introduction
- Total phenolic contents and antioxidant activity
Antioxidant activity (AA) of phenolic compounds has been an important parameter in food science, nutrition and medical studies.129 The antioxidant activity has been defined as potential compounds that can delay, inhibit or prevent oxidation reaction of oxidizable materials by scavenging or neutralizing free radicals and reactive oxygen species (ROS).61 The antioxidant activity is related to the presence of. Trolox solution was used as a general standard for the calibration curve of the method.131 The antioxidant activity determination is recommended to be evaluated from two methods as a minimum, therefore normally more than one method is combined to measure antioxidant activity in order to obtain comprehensive information to give about the total antioxidant activity of food and drink.129, 132 There are many publications that determine the content of phenolic compounds by FC method and its antioxidant activity by DPPH, TEAC and FRAP methods. The excellent linear correlation between phenolic compounds concentration and antioxidant activity of phenolic compounds is often found.
Therefore, both total phenolic content and antioxidant activity evaluation have become routine tests in phenolic antioxidant research133. The amount of these types of health care additives is becoming a decisive factor in the consumption of food and beverages.134 The presence of natural antioxidants in food and beverages, such as total phenolic compound and its antioxidant activity, has attracted significant interest due to its potential . health care function and therapeutic effects. Therefore, quantification methods for total phenolic content and antioxidant activity in food and beverages have received great attention to measure the phenolic compounds and thereby ensure the quality of the products.
Available methods for total phenolic content and antioxidant activity
Recently, a lab-on-a-chip system has been used for simple one-step reaction and detection of total phenolic content and antioxidant activity in microfluidic channels. Both lab-on-a-chip based detection of total phenolic content and antioxidant activity detection are novelties in automating the complicated steps and reducing the sample and reagent volume. Moreover, both studies cannot detect total phenolic content and antioxidant activity at the same time, and also in Lee's work, they only used the DPPH method for the detection of antioxidant activity.
143 As the advantages described above, laboratory-on-disk can be an ideal solution to overcome the limitations of preliminary detection of total phenolic content and antioxidant activity, such as huge consumption of reagents that requires complex pumping, high cost, long analysis time, and labor-intensive manual handling and minimum amount of instrument. In this work, we present a new fully integrated lab-on-a-disc system for simultaneous determination of total phenolic content and detection of antioxidant activity from various beverage samples (teas, fruit juices, beer and wines). The lab-on-disk method was validated with a conventional method for the analysis of total phenolic content and antioxidant activity in various beverage samples.
Simultaneous determination of total phenolic contents and antioxidant activity of
- Experimental details
- Results and discussion
- Conclusions
The consumption of sample and reagent volumes for the determination of the total phenolic content (FC method) and antioxidant activity (DPPH and FRAP methods) was studied using the spectrophotometric method (manual method). Therefore, eight beverage samples dilution ratio for the determination of total phenolic content (FC method) and antioxidant activity (DPPH and FRAP methods) were studied using the spectrophotometric method (manual method) before being integrated with laboratory-on-a- disk system. The total phenolic content and antioxidant activity of eight different types of beverage samples were evaluated in our lab-on-a-disc platform as shown in Figure 3.8.
A lab-on-a-disc method was successfully developed for the integrated and automated analysis of total phenolic content and antioxidant activity from beverage samples. The lab-on-a-disc method was successfully validated with the conventional method for the analysis of total phenol content and antioxidant activity in various beverage samples. The total phenolic content and antioxidant activity values obtained from our lab-on-a-disc method showed relatively good correlation.
Absorbance and luminescence detection on a disc
History of on-disc absorbance and luminescence detection
Ding et al. demonstrated that an in-line, miniature, low-cost, and portable spectrophotometric detection system can be used for rapid protein determination and calibration in a laboratory-on-a-disk platform.85 Their portable detection analyzer is configured with a paired transmitter and detector diodes, meaning that the light beam between both paired LEDs is collimated with improved system tolerance. The wavelength of light emitted by a molecule in chemiluminescence is the same as in its fluorescence, where the energy levels of the molecules are the same. If the energy of the chemical reaction is lower than required to reach the excited state, chemiluminescence does not occur.
Also, the deactivation of the excited molecule by non-radiative processes, such as collisions with other molecules, takes place for chemiluminescence in the same way as fluorescence. In 2006, Riegger et al. a versatile concept for the automated protocols and high-speed (< 1s) reading of parallel chemiluminescent ELISAs. Czilwik et al, developed a LabDisk player which integrates detector to measure chemiluminescent signal in immunoassay for human C-reactive protein.
On-disc absorbance detection
To investigate the absorbance measurement specifics of our disk analyzer, we loaded the dye solution (absorbance wavelength at 500 nm) with dilution onto a disk and measured the absorbance using the disk analyzer. As shown in Figure 4.6C, the measured OD value of our disk analyzer was compared with that of the conventional spectrometer (Tecan, Infinite® 200 PRO). A high linear correlation was obtained between the OD value from the disc analyzer and the OD value from the conventional spectrometer (R2 > 0.99).
For low OD detection (less than 0.1 OD), we tested our disk analyzer with a low concentration dye solution. As shown in Figure 4.7, the measured low OD value of our disk analyzer was compared with that of a commercial spectrometer (Tecan, Infinite® 200 PRO). A high linear correlation was obtained between the low OD value of a disk analyzer and the low OD value of a commercial spectrometer (R2 > 0.99).
On-disc luminescence detection set-up
As shown in the figure the chemiluminescence signal in the affected central chamber in the other detection chamber without ferrofluid barrier (left column graph). 2.9 % chemiluminescence signal will be very critical when the next detection chamber shows low chemiluminescence signal, while the central chamber shows high chemiluminescence signal. As shown in the chemiluminescence image, the signal was transferred to the next ferrofluid barrier detection chamber (right graph).
2.9% of chemiluminescence signal in middle chamber affected to next detection chamber without ferrofluid barrier (left bar graph) and 0.63% of chemiluminescence signal was transferred to next detection chamber with ferrofluid barrier (right bar graph). To investigate the chemiluminescence signal measurement specifications of our disk analyzer, we put the CRP solution with dilution on a disk and measured the chemiluminescence using the disk analyzer. Chemiluminescence signal comparison results between commercial spectrometer (PerkinElmer, EnVision 2105 Multimode Plate Reader) and disk analyzer were given in Figure 4.12.
Conclusions
- On-going portable disc analyzer
For on-site use of lab-on-a-disk, portable lab-on-a-disk analyzer is required. This device will integrate five-wavelength LED and photodiode for absorption detection, BLDC motor with encoder driver for motion control, rechargeable battery pack for portability, laser drive for valves and camera module for disk imaging. As a preliminary observational test, we detected the 540 nm wavelength absorption using lab-on-a-disk with a 5.14 mm path length.
As the future works, we will test other functional parts including 4 more LED and photodiode pair, motor spin rpm and torque with lab-on-a-disk integration, laser module for valves and camera module for imaging the disk. We believe that our new portable lab-on-a-disk analyzer can be used for the detection of various field applications, such as microalgae lipid quantification, and the detection of total phenolic and antioxidant compounds from a beverage sample. Schematic illustration showing (A) functional module (B) top view of board (C) detection module (D) expected image of device. E) Schematic of side view of sensing part, overall path length for absorption detection is 5.14 mm.
General conclusions and future perspectives
General conclusions
Disc analyzer system is a custom machine that uses the following components: stepper motor, optomechanical components, translation stages, light source, optical density detector, and commercially available PMT. The optomechanical parts and stepper motor are assembled to hold the device, and the motor can rotate the disc. The detection is performed by both optical density detector and PMT fixed on the optomechanical parts, and it is located above the detection chambers of the device.
For optical density detection (colorimetric absorbance detection), OD detector coupled optical fiber and light source coupled optical fiber are aligned, and disc detection chamber is aligned between optical fibers. For chemiluminescence detection, if the stepper motor manipulates, the detection chambers are aligned right below the detection zone of PMT. By using it, certain position of disc chamber can be selected and its signal can be detection.
Future perspective
- Microfluidic in biofuel production
- Microfluidics in food nutrient determination
For sample preparation, all microfluidic devices need additional off-chip sample preparation, such as off-chip dilution, fluorescent dye labeling, filtration, and (solid-liquid) extraction. Nutrient Sample Microchip Device for sample preparation for detection. tyramine, histamine) Wines, sakes, beers Division in MCE. 9157 Biogenic amine (tryptamine, . tyramine), amino acid (tryptophan) Rice wine, beer CZE microchip Off-chip dilution Electrochemical detection 10158 Vanillin, ethyl vanillin Vanilla pod,.
Focke, M.; Stumpf, F.; Roth, G.; Zengerle, R.; von Stetten, F., Centrifugal microfluidic system for primary amplification and secondary real-time PCR. Mark, D.; Haeberle, S.; Roth, G.; von Stetten, F.; Zengerle, R., Laboratory microfluidic platforms on a chip: requirements, characteristics and applications. G.; Cho, Y.-K., Fully integrated disk-based laboratory for simultaneous biochemistry and immunoassay analysis from whole blood.
