Microfluidic Organ-on-A-chip: A Guide to Biomaterial Choice and Fabrication.

Organ-on-A-chip (OoAC) devices are miniaturized, functional, in vitro constructs that aim to recapitulate the in vivo physiology of an organ using different cell types and extracellular matrix, while maintaining the chemical and mechanical properties of the surrounding microenvironments. From an end-point perspective, the success of a microfluidic OoAC relies mainly on the type of biomaterial and the fabrication strategy employed. Certain biomaterials, such as PDMS (polydimethylsiloxane), are preferred over others due to their ease of fabrication and proven success in modelling complex organ systems. However, the inherent nature of human microtissues to respond differently to surrounding stimulations has led to the combination of biomaterials ranging from simple PDMS chips to 3D-printed polymers coated with natural and synthetic materials, including hydrogels. In addition, recent advances in 3D printing and bioprinting techniques have led to the powerful combination of utilizing these materials to develop microfluidic OoAC devices. In this narrative review, we evaluate the different materials used to fabricate microfluidic OoAC devices while outlining their pros and cons in different organ systems. A note on combining the advances made in additive manufacturing (AM) techniques for the microfabrication of these complex systems is also discussed.

A Tri-Channel Oxide Transistor Concept for the Rapid Detection of Biomolecules Including the SARS-CoV-2 Spike Protein.

Solid-state transistor sensors that can detect biomolecules in real time are highly attractive for emerging bioanalytical applications. However, combining upscalable manufacturing with the required performance remains challenging. Here, an alternative biosensor transistor concept is developed, which relies on a solution-processed In2 O3 /ZnO semiconducting heterojunction featuring a geometrically engineered tri-channel architecture for the rapid, real-time detection of important biomolecules. The sensor combines a high electron mobility channel, attributed to the electronic properties of the In2 O3 /ZnO heterointerface, in close proximity to a sensing surface featuring tethered analyte receptors. The unusual tri-channel design enables strong coupling between the buried electron channel and electrostatic perturbations occurring during receptor-analyte interactions allowing for robust, real-time detection of biomolecules down to attomolar (am) concentrations. The experimental findings are corroborated by extensive device simulations, highlighting the unique advantages of the heterojunction tri-channel design. By functionalizing the surface of the geometrically engineered channel with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody receptors, real-time detection of the SARS-CoV-2 spike S1 protein down to am concentrations is demonstrated in under 2 min in physiological relevant conditions.

Point-of-care microvolume cytometer measures platelet counts with high accuracy from capillary blood.

BACKGROUND: Point-of-care (PoC) testing of platelet count (PLT) provides real-time data for rapid decision making. The goal of this study is to evaluate the accuracy and precision of platelet counting using a new microvolume (8 µL), absolute counting, 1.5 kg cytometry-based blood analyzer, the rHEALTH ONE (rHEALTH) in comparison with the International Society of Laboratory Hematology (ISLH) platelet method, which uses a cytometer and an impedance analyzer. METHODS: Inclusion eligibility were healthy adults (M/F) ages 18-80 for donation of fingerprick and venous blood samples. Samples were from a random N = 31 volunteers from a single U.S. site. Samples were serially diluted to test thrombocytopenic ranges. Interfering substances and conditions were tested, including RBC fragments, platelet fragments, cholesterol, triglycerides, lipids, anti-platelet antibodies, and temperature. RESULTS: The concordance between the rHEALTH and ISLH methods had a slope = 1.030 and R2 = 0.9684. The rHEALTH method showed a correlation between capillary and venous blood samples (slope = 0.9514 and R2 = 0.9684). Certain interferents changed platelet recovery: RBC fragments and anti-platelet antibodies with the ISLH method; platelet fragments and anti-platelet antibodies on the rHEALTH; and RBC fragments, platelets fragments, triglycerides and LDL on the clinical impedance analyzer. The rHEALTH's precision ranged from 3.1-8.0%, and the ISLH from 1.0-10.5%. CONCLUSIONS: The rHEALTH method provides similar results with the reference method and good correlation between adult capillary and venous blood samples. This demonstrates the ability of the rHEALTH to provide point-of-care assessment of normal and thrombocytopenic platelet counts from fingerprick blood with high precision and limited interferences.

Reliable and highly sensitive biosensor from suspended MoS2 atomic layer on nano-gap electrodes.

The uneven morphology and the trapped charges at the surface of the traditionally used supporting substrate-based 2D biosensors produces a scattering effect, which leads to a irregular signals from individually fabricated devices. Though suspended 2D channel material has the potential to overcome scattering effects from the substrates but achieving reliability and selectivity, have been limiting the using of this biosensor technology. Here, we have demonstrated nanogap electrodes fabrication by using the self-assembly technique, which provides suspension to the 2D-MoS2. These nano-spacing electrodes not only give suspension but also provide robustness strength to the atomic layer, which remains freestanding after coating of the Hafnium oxide (HfO2) as well as linkers and antibodies. For evaluating the electrical characteristics of suspended MoS2 FET, gating potential was applied through an electrolyte on the suspended MoS2 transistor. This helped in achieved a lower subthreshold swing 70 mV/dec and ON/OFF ratio 107. Later, pH detection was conducted at room temperature, which showed an impressive sensitivity of ~880 by changing 1 unit of pH. We have also successfully shown Escherichia coli (E. coli) bacteria sensing from the suspended MoS2 transistor by functionalizing dielectric layer with E. coli antibodies. The reported biosensor has shown the ~9% of conductance changes with a lower concentration of E. coli (10 CFU/mL; colony-forming unit per mL) as well as maintain the constant sensitivity in three fabricated devices. The obtained enhancement in the sensitivity of devices and its effect on biomolecules detection can be extened to other biomolecules and this type of architecture has the potential to detect COVID-19 viruses based biomolecules.

Real-time physiological measurements of oxygen using a non-invasive self-referencing optical fiber microsensor.

Reactive molecular oxygen (O2) plays important roles in bioenergetics and metabolism and is implicated in biochemical pathways underlying angiogenesis, fertilization, wound healing and regeneration. Here we describe how to use the scanning micro-optrode technique (SMOT) to measure extracellular fluxes of dissolved O2. The self-referencing O2-specific micro-optrode (also termed micro-optode and optical fiber microsensor) is a tapered optical fiber with an O2-sensitive fluorophore coated onto the tip. The O2 concentration is quantified by fluorescence quenching of the fluorophore emission upon excitation with blue-green light. The micro-optrode presents high spatial and temporal resolutions with improved signal-to-noise ratio (in the picomole range). In this protocol, we provide step-by-step instructions for micro-optrode calibration, validation, example applications and data analysis. We describe how to use the technique for cells (Xenopus oocyte), tissues (Xenopus epithelium and rat cornea), organs (Xenopus gills and mouse skin) and appendages (Xenopus tail), and provide recommendations on how to adapt the approach to different model systems. The basic, user-friendly system presented here can be readily installed to reliably and accurately measure physiological O2 fluxes in a wide spectrum of biological models and physiological responses. The full protocol can be performed in ~4 h.

Antibody Micropatterned Lubricant-Infused Biosensors Enable Sub-Picogram Immunofluorescence Detection of Interleukin 6 in Human Whole Plasma.

Recent studies have shown a correlation between elevated interleukin 6 (IL-6) concentrations and the risk of respiratory failure in COVID-19 patients. Therefore, detection of IL-6 at low concentrations permits early diagnosis of worst-case outcome in viral respiratory infections. Here, a versatile biointerface is presented that eliminates nonspecific adhesion and thus enables immunofluorescence detection of IL-6 in whole human plasma or whole human blood during coagulation, down to a limit of detection of 0.5 pg mL-1 . The sensitivity of the developed lubricant-infused biosensor for immunofluorescence assays in detecting low molecular weight proteins such as IL-6 is facilitated by i) producing a bioink in which the capture antibody is functionalized by an epoxy-based silane for covalent linkage to the fluorosilanized surface and ii) suppressing nonspecific adhesion by patterning the developed bioink into a lubricant-infused coating. The developed biosensor addresses one of the major challenges for biosensing in complex fluids, namely nonspecific adhesion, therefore paving the way for highly sensitive biosensing in complex fluids.

From micro to nano: evolution and impact of drug delivery in treating disease.

Over the past 50 years, drug delivery breakthroughs have enabled the approval of several important medicines. Often, this path starts with innovation from academic collaborations amongst biologists, chemists, and engineers, followed by the formation of a start-up company driving clinical translation and approval. An early wave featured injectable (i.e., intramuscular, subcutaneous) biodegradable polymeric microspheres to control drug release profiles for peptides and small molecules (e.g., Lupron Depot®, Risperdal Consta®). With these early successes for microspheres, research shifted to exploring systemic delivery by intravenous injection, which required smaller particle sizes and modified surface properties (e.g., PEGylation) to enable long circulation times. These new innovations resulted in the nanoparticle medicines Doxil® and Abraxane®, designed to improve the therapeutic index of cytotoxic cancer agents by decreasing systemic exposure and delivering more drug to tumors. Very recently, the first siRNA lipid nanoparticle medicine, Patisiran (Onpattro®), was approved for treating hereditary transthyretin-mediated amyloidosis. In this inspirational note, we will highlight the technological evolution of drug delivery from micro- to nano-, citing some of the approved medicines demonstrating the significant impact of the drug delivery field in treating many diseases.