Pollution-Free and Highly Sensitive Lactate Detection in Cell Culture Based on a Microfluidic Chip

Droplet Impedance Feedback-Enabled Microsampling Microfluidic Device for Precise Chemical Information Monitoring

Microelectrodes have transformed our understanding of spatiotemporal responses to electrical stimulation. However, biological signals are often molecular, complicating the capture of intricate chemical signals. The microfluidic chip developed in this paper accurately measures droplet volume by using impedance analysis. The utilization of droplet volume as a feedback signal for precise microsampling pressure control ensures that microsampling remains unaffected by droplet volume influence. Once the microsampling is complete, chemiluminescence detection enables high temporal resolution and continuous and sensitive monitoring of chemical information within the droplets. Experimental verification shows that the chip can avoid volume influence through impedance feedback, achieving consistent and stable microampling at the nanoliter level (0-3 nL). In just 0.3 s, it can perform sensitive chemiluminescence detection of H2O2 and glucose within droplets. The linear detection ranges for these analytes are 10-50,000 and 20-600 μM, respectively, with the limit of detection being 0.648 and 0.334 μM. The significance of this chip lies in its ability to reveal changes in both electrical and chemical signals during transient biological processes. Its potential applications are numerous, encompassing a wide range of emerging areas such as single-cell analysis, cell communication, and cellular immunity.

A tempo-spatial controllable microfluidic shear-stress generator for in-vitro mimicking of the thrombus

Pathological conditions linked to shear stress have been identified in hematological diseases, cardiovascular diseases, and cancer. These conditions often exhibit significantly elevated shear stress levels, surpassing 1000 dyn/cm2 in severely stenotic arteries. Heightened shear stress can induce mechanical harm to endothelial cells, potentially leading to bleeding and fatal consequences. However, current technology still grapples with limitations, including inadequate flexibility in simulating bodily shear stress environments, limited range of shear stress generation, and spatial and temporal adaptability. Consequently, a comprehensive understanding of the mechanisms underlying the impact of shear stress on physiological and pathological conditions, like thrombosis, remains inadequate. To address these limitations, this study presents a microfluidic-based shear stress generation chip as a proposed solution. The chip achieves a substantial 929-fold variation in shear stress solely by adjusting the degree of constriction in branch channels after PDMS fabrication. Experiments demonstrated that a rapid increase in shear stress up to 1000 dyn/cm2 significantly detached 88.2% cells from the substrate. Long-term exposure (24 h) to shear stress levels below 8.3 dyn/cm2 did not significantly impact cell growth. Furthermore, cells exposed to shear stress levels equal to or greater than 8.3 dyn/cm2 exhibited significant alterations in aspect ratio and orientation, following a normal distribution. This microfluidic chip provides a reliable tool for investigating cellular responses to the wide-ranging shear stress existing in both physiological and pathological flow conditions.

High sensitivity and automatic chemiluminescence detection of glucose and lactate using a spin-disc paper-based device

This paper reports a spin-disc paper-based device with 10 individual detection units containing electromagnetic modules controlling the sample incubation time before chemiluminescence (CL) signal detection. After the sample was added to the top paper chip and incubated with the enzyme, the electromagnet was turned off to allow contact between the top and bottom paper. The H2O2 generated by the sample flowed vertically to the bottom paper and initiated the oxidase of the luminol to generate the CL signal. After one detection the disc was automatically rotated to the next position to repeat the above detection. The advantage of using the device over the lateral flow and the in situ detection was firstly proved using the detection of H2O2 and the glucose/lactate sample with 5 minute incubation. The CL intensity was increased 300 times/1000 times as the glucose/lactate was incubated for 5 minutes compared to the non-incubated samples. Afterward, the device was employed to separately detect glucose and lactate diluted in PBS, artificial sweat, artificial saliva, and fresh cell culture media. Finally, the device was employed to detect the glucose and lactate in the media collected over the 24 hour culture of PC3 cells. The uptake and production rates of glucose and lactate were correspondingly determined as 0.328 ± 0.015 pmol h-1 per cell and 1.254 ± 0.053 pmol h-1 per cell, respectively. The reported device has wide application potential due to its capabilities in automatic detection of multiple samples with very high sensitivity and small sample volume (down to 0.5 μL).