Advection-Enhanced Kinetics in Microtiter Plates for Improved Surface Assay Quantitation and Multiplexing Capabilities

Micro-/nanoscale robotics for chemical and biological sensing

The field of micro-/nanorobotics has attracted extensive interest from a variety of research communities and witnessed enormous progress in a broad array of applications ranging from basic research to global healthcare and to environmental remediation and protection. In particular, micro-/nanoscale robots provide an enabling platform for the development of next-generation chemical and biological sensing modalities, owing to their unique advantages as programmable, self-sustainable, and/or autonomous mobile carriers to accommodate and promote physical and chemical processes. In this review, we intend to provide an overview of the state-of-the-art development in this area and share our perspective in the future trend. This review starts with a general introduction of micro-/nanorobotics and the commonly used methods for propulsion of micro-/nanorobots in solution, along with the commonly used methods in their fabrication. Next, we comprehensively summarize the current status of the micro/nanorobotic research in relevance to chemical and biological sensing (e.g., motion-based sensing, optical sensing, and electrochemical sensing). Following that, we provide an overview of the primary challenges currently faced in the micro-/nanorobotic research. Finally, we conclude this review by providing our perspective detailing the future application of soft robotics in chemical and biological sensing.

Efficient Pathogen Capture and Sensing Promoted by Dynamic Deformable Nanointerfaces

The M13 bacteriophage (M13 phage) has emerged as an attractive bionanomaterial due to its chemistry/gene modifiable feature and unique structures. Herein, a dynamic deformable nanointerface is fabricated taking advantage of the unique feature of the M13 phage for ultrasensitive detection of pathogens. PIII proteins at the tip of the M13 phage are genetically modified to display 6His peptide for site-specific anchoring onto Ni-NTA microbeads, whereas pVIII proteins along the side of the M13 phage are orderly arranged with thousands of aptamers and their complementary strands (c-apt). The flexible M13 nanofibers with rich recognition sites act as octopus tentacles, resulting in a 19-fold improvement in the capture affinity toward the target. The competitive binding of the target pathogen releases c-apts and initiates rolling circle amplification (RCA). The sway motion of M13 nanofibers accelerates the diffusion of c-apts, thus promoting RCA efficiency. Benefiting from the strengthened capture ability toward the target and the accelerated RCA process, three-orders of magnitude improvement in the sensitivity is achieved, with a detection limit of 8 cfu mL^-1 for Staphylococcus aureus. The promoted capture ability and assay performance highlights the essential role of the deformable feature of the engineered interface. This may provide inspiration for the construction of more efficient reaction interfaces.

Ultrafast Electrothermal Flow-Enhanced Magneto Biosensor for Highly Sensitive Protein Detection in Whole Blood

Current diagnostic tests for sensitive protein detection rely on immunological techniques, such as ELISA, which require sample purification, multiple washing steps and lengthy incubation, hindering their use for rapid testing. Here, we report a simple electrothermal flow-enhanced biosensor for ultrafast, high sensitivity measurements of protein biomarkers in whole blood. Magnetic nanobeads dually-labeled with a detection antibody and enzyme reporter are used to form immunocomplexes with the target protein, which are readily transported to the sensor via magnetic concentration. The incorporation of electrothermal flows enhances immunocomplex formation, allowing for rapid and sensitive detection without requiring blood purification or lengthy incubation. Proof of concept was carried out using Plasmodium falciparum histidine-rich protein 2 (PfHRP2), a malaria parasite biomarker, which could be detected at concentrations as low as 5.7 pg mL^-1 (95 fM) in whole blood in 7 min. The speed, sensitivity and simplicity of this device make it attractive for rapid diagnostic testing.

Microscale hydrodynamic confinements: shaping liquids across length scales as a toolbox in life sciences

Hydrodynamic phenomena can be leveraged to confine a range of biological and chemical species without needing physical walls. In this review, we list methods for the generation and manipulation of microfluidic hydrodynamic confinements in free-flowing liquids and near surfaces, and elucidate the associated underlying theory and discuss their utility in the emerging area of open space microfluidics applied to life-sciences. Microscale hydrodynamic confinements are already starting to transform approaches in fundamental and applied life-sciences research from precise separation and sorting of individual cells, allowing localized bio-printing to multiplexing for clinical diagnosis. Through the choice of specific flow regimes and geometrical boundary conditions, hydrodynamic confinements can confine species across different length scales from small molecules to large cells, and thus be applied to a wide range of functionalities. We here provide practical examples and implementations for the formation of these confinements in different boundary conditions - within closed channels, in between parallel plates and in an open liquid volume. Further, to enable non-microfluidics researchers to apply hydrodynamic flow confinements in their work, we provide simplified instructions pertaining to their design and modelling, as well as to the formation of hydrodynamic flow confinements in the form of step-by-step tutorials and analytical toolbox software. This review is written with the idea to lower the barrier towards the use of hydrodynamic flow confinements in life sciences research.

Simple add-on devices to enhance the efficacy of conventional surface immunoassays implemented on standard labware

We propose microfluidic add-ons easily placed on standard assay labware such as microwells and slides to enhance the kinetics of immunoassays. The devices are compatible with mass production, well-established assay protocols and automated platforms.