Regeneration of Assembled, Molecular-Motor-Based Bionanodevices

Microscope-Free Analyte Detection Based on Fiber-Optic Gliding Motility Assays

Prolonged hospital waiting times are linked with increased patient mortality and cause additional financial burdens on institutions. Efficient point-of-care diagnosis would help alleviate this, but is hampered by a lack of cost-effective devices capable of rapid, in situ, wide ranging analyte detection. Lab-on-fiber technology provides an answer allowing for diagnosis, treatment, and monitoring in situ with real time feedback. Here, a device is demonstrated that harnesses motor-protein-driven-microtubule molecular detection assays to optical fibers. By developing a new method for microscope-free microtubule gliding speed determination, proof of concept is demonstrated in the detection of Monomeric Streptavidin and Neutravidin, which initiate a decrease in speed in biotinylated microtubules as well as bundling in the latter case. Utilizing antibody functionalizsed microtubules label-free and microscope-free detection of the heart attack marker Creatine Kinase-MB, as well secondary antibodies in nm concentration is demonstrated. This detector has the potential to be used in situ, providing rapid, low-cost, multiplex analyte screening and detection.

FOF1-ATPase Biomolecular Motor: Structure, Motility Manipulations, and Biomedical Applications

Biomolecular motors are dynamic systems found in organisms with high energy conversion efficiency. FOF1-ATPase is a rotary biomolecular motor known for its near 100% energy conversion efficiency. It utilizes the synthesis and hydrolysis of ATP to induce conformational changes in motor proteins, thereby converting chemical energy into mechanical motion. Given their high efficiency, autonomous propulsion capability, and modifiable structures, FOF1-ATPase motors have attracted significant attention for potential biomedical applications. This Review aims to introduce the detailed structure of FOF1-ATPase, explore various motility manipulation strategies, and summarize its applications in biological detection and cargo delivery. Additionally, innovative research methods are proposed to analyze the motion mechanism of FOF1-ATPase more comprehensively, with the goal of advancing its biomedical applications. Finally, this Review concludes with key insights and future perspectives.

Improved longevity of actomyosin in vitro motility assays for sustainable lab-on-a-chip applications

In the in vitro motility assay (IVMA), actin filaments are observed while propelled by surface-adsorbed myosin motor fragments such as heavy meromyosin (HMM). In addition to fundamental studies, the IVMA is the basis for a range of lab-on-a-chip applications, e.g. transport of cargoes in nanofabricated channels in nanoseparation/biosensing or the solution of combinatorial mathematical problems in network-based biocomputation. In these applications, prolonged myosin function is critical as is the potential to repeatedly exchange experimental solutions without functional deterioration. We here elucidate key factors of importance in these regards. Our findings support a hypothesis that early deterioration in the IVMA is primarily due to oxygen entrance into in vitro motility assay flow cells. In the presence of a typically used oxygen scavenger mixture (glucose oxidase, glucose, and catalase), this leads to pH reduction by a glucose oxidase-catalyzed reaction between glucose and oxygen but also contributes to functional deterioration by other mechanisms. Our studies further demonstrate challenges associated with evaporation and loss of actin filaments with time. However, over 8 h at 21-26 °C, there is no significant surface desorption or denaturation of HMM if solutions are exchanged manually every 30 min. We arrive at an optimized protocol with repeated exchange of carefully degassed assay solution of 45 mM ionic strength, at 30 min intervals. This is sufficient to maintain the high-quality function in an IVMA over 8 h at 21-26 °C, provided that fresh actin filaments are re-supplied in connection with each assay solution exchange. Finally, we demonstrate adaptation to a microfluidic platform and identify challenges that remain to be solved for real lab-on-a-chip applications.

The potential of myosin and actin in nanobiotechnology

Since the late 1990s, efforts have been made to utilize cytoskeletal filaments, propelled by molecular motors, for nanobiotechnological applications, for example, in biosensing and parallel computation. This work has led to in-depth insights into the advantages and challenges of such motor-based systems, and has yielded small-scale, proof-of-principle applications but, to date, no commercially viable devices. Additionally, these studies have also elucidated fundamental motor and filament properties, as well as providing other insights obtained from biophysical assays in which molecular motors and other proteins are immobilized on artificial surfaces. In this Perspective, I discuss the progress towards practically viable applications achieved so far using the myosin II-actin motor-filament system. I also highlight several fundamental pieces of insights derived from the studies. Finally, I consider what may be required to achieve real devices in the future or at least to allow future studies with a satisfactory cost-benefit ratio.

Nanolithographic Fabrication Technologies for Network-Based Biocomputation Devices

Network-based biocomputation (NBC) relies on accurate guiding of biological agents through nanofabricated channels produced by lithographic patterning techniques. Here, we report on the large-scale, wafer-level fabrication of optimized microfluidic channel networks (NBC networks) using electron-beam lithography as the central method. To confirm the functionality of these NBC networks, we solve an instance of a classical non-deterministic-polynomial-time complete ("NP-complete") problem, the subset-sum problem. The propagation of cytoskeletal filaments, e.g., molecular motor-propelled microtubules or actin filaments, relies on a combination of physical and chemical guiding along the channels of an NBC network. Therefore, the nanofabricated channels have to fulfill specific requirements with respect to the biochemical treatment as well as the geometrical confienement, with walls surrounding the floors where functional molecular motors attach. We show how the material stack used for the NBC network can be optimized so that the motor-proteins attach themselves in functional form only to the floor of the channels. Further optimizations in the nanolithographic fabrication processes greatly improve the smoothness of the channel walls and floors, while optimizations in motor-protein expression and purification improve the activity of the motor proteins, and therefore, the motility of the filaments. Together, these optimizations provide us with the opportunity to increase the reliability of our NBC devices. In the future, we expect that these nanolithographic fabrication technologies will enable production of large-scale NBC networks intended to solve substantially larger combinatorial problems that are currently outside the capabilities of conventional software-based solvers.

Enzyme-driven micro/nanomotors: Recent advances and biomedical applications

Micro/nanomotors (MNMs), both self-propelled actuators and external fields-promoted machines, have joined forces in the past decade to accomplish versatile tasks such as precise detection and targeted cargo delivery with adequate propulsion and desirable locomotion. Amongst, enzyme-driven MNMs have been able to differentiate themselves from others owing to their distinct characteristics, such as absence of chemical fuel, enhanced cellular uptake and the possibility to be easily conjugated with many therapeutics, including both small molecules and biologics, displaying superior efficacy, enhanced specificity and diminished side effects. In the present review, we aim to highlight and summarize recent advances in enzyme-driven MNMs, particularly to provide an in-depth discussion focusing on the enzyme linking approaches onto those MNMs and motion control strategies of such MNMs with advantages and limitations thereof. Conclusions and future perspectives are also provided in brief.