A 3D-printed, multi-modal microfluidic device for measuring nitric oxide and ATP release from flowing red blood cells

Oxygen-Sensitive Optical Nanosensors: Current Advances and Future Perspectives

Oxygen sensing is essential across a wide range of fields, from understanding cellular metabolism and disease mechanisms to optimizing industrial and environmental processes. In this Perspective, we highlight key developments in optical architectures (at the nanometer to sub-micrometer scale), including their transduction methods and applications to in vitro, in vivo/in situ, and nonbiological systems. We also discuss future directions for the field in the domain of expanding extra/intracellular and nonbiological sensing. We address improving accessibility for nonexpert users through the need for standardized protocols and scalable production methods. Furthermore, we advocate for fostering interdisciplinary collaborations through academic incubators, conference networking, and strategic citation practices to bridge gaps between fundamental research and applied science to expand the impact of these tools to researchers outside the sensing field. Addressing these challenges will help drive the development of more versatile and widely accessible oxygen sensors, thus advancing innovation across diverse disciplines.

Recombinant-Chemosynthetic Biosensors for Probing Cell Surface Signaling of Red Blood Cells and Other Cells

The complex signaling mechanisms in red blood cells (RBCs) enable them to adapt to physiological stresses such as exposure to low O2 levels, metabolic demands, oxidative stress, and shear stress. Since Ca2+ is a crucial determinant of RBC fate, various ion channels, pumps, and exchangers regulate the delicate balance of Ca2+ influx and efflux in RBCs. Elevated intracellular Ca2+ can activate processes such as membrane phospholipid scrambling and alter RBC deformability, which is essential for effective capillary transit. However, the dynamic information about Ca2+ regulation in RBCs is limited. Although static mapping and bioanalytical methods have been utilized, the absence of a nucleus and the presence of hemoglobin create challenges for real-time probing of RBC signaling, necessitating innovative approaches. This work introduces a synthetic chemistry-recombinant protein-based strategy to assemble sensors at genetically intact healthy human RBC surfaces for measuring dynamic signaling. Using this approach, we measured autocrine regulation of RBC Ca2+ influx in response to low O2 tension-induced ATP release. The study also explores the utilization of synthetic glycosylphosphatidylinositol (GPI) anchor mimics and sortagging for targeting sensors to the surfaces of primary as well as immortalized cells. This demonstrated the wide applicability of this approach to probe dynamic signaling in intact cells.

3D-Printed Microfluidic-Based Cell Culture System With Analysis to Investigate Macrophage Activation

In this paper, we describe the development of 3D-printed microfluidic cell culture devices that can be coupled with a circulation system to study the dynamics of both intracellular and extracellular (release) processes. Key to this approach is the ability to quantitate key analytes on a minutes timescale with either on-line (in this study, quantitating nitric oxide production using an amperometric flow cell) or off-line (in this work, quantitating intracellular itaconate production with LC/MS) analytical measurements. To demonstrate the usefulness of this approach, we chose to study macrophage polarization as a function of the extracellular matrix (silk) fiber size, a major area of research in tissue engineering. It was found that the use of larger fibers (1280 nm vs. smaller 512 nm fibers) led to increases in the production of both nitric oxide and itaconate. These findings set the foundation for future research for the creation of finely tuned microfluidic 3D cell culture approaches in areas where flow and the extracellular matrix play a significant role in barrier transport and where integrated analysis of key markers is needed.

3D printed microfluidic devices with electrodes for electrochemical analysis

A review with 93 references describing various 3D printing approaches that have been used to create microfluidic devices containing electrodes for electrochemical detection. The use of 3D printing to fabricate microfluidic devices is a rapidly growing area. One significant research area is how to detect analytes in the devices for quantitation purposes. This review article is focused on methods used to integrate electrodes into the devices for electrochemical detection. The review is organized in terms of the methodology for integrating the electrode within the device. This includes (1) external coupling of traditional electrode materials with 3D printed devices; (2) printing conductive electrode materials as part of device printing; and (3) integrating traditional electrodes into the device as part of the print process. Example applications are given and some future directions are also outlined.

A review of the recent achievements and future trends on 3D printed microfluidic devices for bioanalytical applications

3D printing has revolutionized the manufacturing process of microanalytical devices by enabling the automated production of customized objects. This technology promises to become a fundamental tool, accelerating investigations in critical areas of health, food, and environmental sciences. This microfabrication technology can be easily disseminated among users to produce further and provide analytical data to an interconnected network towards the Internet of Things, as 3D printers enable automated, reproducible, low-cost, and easy fabrication of microanalytical devices in a single step. New functional materials are being investigated for one-step fabrication of highly complex 3D printed parts using photocurable resins. However, they are not yet widely used to fabricate microfluidic devices. This is likely the critical step towards easy and automated fabrication of sophisticated, complex, and functional 3D-printed microchips. Accordingly, this review covers recent advances in the development of 3D-printed microfluidic devices for point-of-care (POC) or bioanalytical applications such as nucleic acid amplification assays, immunoassays, cell and biomarker analysis and organs-on-a-chip. Finally, we discuss the future implications of this technology and highlight the challenges in researching and developing appropriate materials and manufacturing techniques to enable the production of 3D-printed microfluidic analytical devices in a single step.

3D printed microfluidic devices for integrated solid-phase extraction and microchip electrophoresis of preterm birth biomarkers

BACKGROUND

Preterm birth (PTB) is a leading cause of neonatal mortality, such that the need for a rapid and accurate assessment for PTB risk is critical. Here, we developed a 3D printed microfluidic system that integrated solid-phase extraction (SPE) and microchip electrophoresis (μCE) of PTB biomarkers, enabling the combination of biomarker enrichment and labeling with μCE separation and fluorescence detection.

RESULTS

Reversed-phase SPE monoliths were photopolymerized in 3D printed devices. Microvalves in the device directed sample between the SPE monolith and the injection cross-channel in the serpentine μCE channel. Successful on-chip preconcentration, labeling and μCE separation of four PTB-related polypeptides were demonstrated in these integrated microfluidic devices. We further show the ability of these devices to handle complex sample matrices through the successful analysis of labeled PTB biomarkers spiked into maternal blood serum. The detection limit was 7 nM for the PTB biomarker, corticotropin releasing factor, in 3D printed SPE-μCE integrated devices.

SIGNIFICANCE

This work represents the first successful demonstration of integration of SPE and μCE separation of disease-linked biomarkers in 3D printed microfluidic devices. These studies open up promising possibilities for rapid bioanalysis of medically relevant analytes.

High-performance microchip electrophoresis separations of preterm birth biomarkers using 3D printed microfluidic devices

We employed digital light processing-stereolithography 3D printing to create microfluidic devices with different designs for microchip electrophoresis (µCE). Short or long straight channel, and two- or four-turn serpentine channel microfluidic devices with separation channel lengths of 1.3, 3.1, 3.0, and 4.7 cm, respectively, all with a cross injector design, were fabricated. We measured current as a function of time and voltage to determine a separation time window and conditions for the onset of Joule heating in these designs. Separations in these devices were evaluated by performing µCE and measuring theoretical plate counts for electric field strengths near and above the onset of Joule heating, with fluorescently labeled glycine and phenylalanine as model analytes. We further demonstrated µCE of peptides and proteins related to preterm birth risk, showing increased peak capacity and resolution compared to previous results with 3D printed microdevices. These results mark an important step forward in the use of 3D printed microfluidic devices for rapid bioanalysis by µCE.

Assessment of stored red blood cells through lab-on-a-chip technologies for precision transfusion medicine

Transfusion of red blood cells (RBCs) is one of the most valuable and widespread treatments in modern medicine. Lifesaving RBC transfusions are facilitated by the cold storage of RBC units in blood banks worldwide. Currently, RBC storage and subsequent transfusion practices are performed using simplistic workflows. More specifically, most blood banks follow the "first-in-first-out" principle to avoid wastage, whereas most healthcare providers prefer the "last-in-first-out" approach simply favoring chronologically younger RBCs. Neither approach addresses recent advances through -omics showing that stored RBC quality is highly variable depending on donor-, time-, and processing-specific factors. Thus, it is time to rethink our workflows in transfusion medicine taking advantage of novel technologies to perform RBC quality assessment. We imagine a future where lab-on-a-chip technologies utilize novel predictive markers of RBC quality identified by -omics and machine learning to usher in a new era of safer and precise transfusion medicine.