Controlled microfluidic reconstitution of functional protein from an anhydrous storage depot

A novel method has been developed for preserving molecules in microfluidic devices that also enables the control of the spatial and temporal concentrations of the reconstituted molecules within the devices. In this method, a storage cavity, embedded in a microchannel, is filled with a carbohydrate matrix containing, for example, a reagent. When the matrix is exposed to flowing liquid, it dissolves, resulting in the controlled reconstitution and release of the reagent from the cavity. The technique was demonstrated using two different model systems; the successful preservation and controlled release of beta-galactosidase was achieved. This method has possible applications for simple point-of-care drug delivery and immunoassays, and could be used to pattern the surfaces of microchannels. More broadly, this preservation and controlled release technique can be applied where the preservation and/or spatial and temporal control of chemical concentrations are desired.     

Controlled liquid-solid interactions at the micron-scale: towards self-assembling MEMS

Self-assembly is the spontaneous and reversible organization of components into ordered structures, representing an alternative to the conventional manufacture of systems made of components from milli to nano scales. First commercial applications of self-assembly have appeared in recent years, for example in the fabrication of radio frequency identification (RFID) tags. However, the full impact of this new approach towards heterogeneous system integration will only be realized once self-assembly can be programmed on demand. A key concept is the “programmable surface” – an interface whose properties can be controlled with high spatial and temporal resolution. Several crucial topics are discussed: real time control of interfacial properties; optimization of binding site designs; and algorithms for the modeling and control of self-assembly. Promising novel manufacturing methods are emerging that combine the precision and reproducibility of semiconductor fabrication with the scalability and parallelism of stochastic self-assembly and with the specificity and programmability of biochemical processes.     

Silver as an example of the applications of photochemistry to the synthesis and uses of nanomaterials

Photochemistry is a powerful tool for controlled synthesis of metal nanoparticles, their modification and in many of the applications that these materials have. Plasmon transitions offer a unique way of delivering energy with exquisite spatial and temporal control and can be used to advantage where visible wavelength control is required. This account of research at the University of Ottawa summarizes details of the synthesis, modification and applications of silver nanostructures.     

Light-Induced Dimerization Approaches to Control Cellular Processes

Light-inducible approaches provide a means to control biological systems with spatial and temporal resolution that is unmatched by traditional genetic perturbations. Recent developments of optogenetic and chemo-optogenetic systems for induced proximity in cells facilitate rapid and reversible manipulation of highly dynamic cellular processes and have become valuable tools in diverse biological applications. New expansions of the toolbox facilitate control of signal transduction, genome editing, “painting” patterns of active molecules onto cellular membranes, and light-induced cell cycle control. A combination of light- and chemically induced dimerization approaches have also seen interesting progress. Herein, an overview of optogenetic systems and emerging chemo-optogenetic systems is provided, and recent applications in tackling complex biological problems are discussed.     

A Photo‐responsive Small‐Molecule Approach for the Opto‐epigenetic Modulation of DNA Methylation

Controlling the functional dynamics of DNA within living cells is essential in biomedical research. Epigenetic modifications such as DNA methylation play a key role in this endeavour. DNA methylation can be controlled by genetic means. Yet there are few chemical tools available for the spatial and temporal modulation of this modification. Herein, we present a small‐molecule approach to modulate DNA methylation with light. The strategy uses a photo‐tuneable version of a clinically used drug (5‐aza‐2′‐deoxycytidine) to alter the catalytic activity of DNA methyltransferases, the enzymes that methylate DNA. After uptake by cells, the photo‐regulated molecule can be light‐controlled to reduce genome‐wide DNA methylation levels in proliferating cells. The chemical tool complements genetic, biochemical, and pharmacological approaches to study the role of DNA methylation in biology and medicine.     

External Regulation of Controlled Polymerizations

Polymer chemists, through advances in controlled polymerization techniques and reliable post‐functionalization methods, now have the tools to create materials of almost infinite variety and architecture. Many relevant challenges in materials science, however, require not only functional polymers but also on‐demand access to the properties and performance they provide. The power of such temporal and spatial control of polymerization can be found in nature, where the production of proteins, nucleic acids, and polysaccharides helps regulate multicomponent systems and maintain homeostasis. Here we review existing strategies for temporal control of polymerizations through external stimuli including chemical reagents, applied voltage, light, and mechanical force. Recent work illustrates the considerable potential for this emerging field and provides a coherent vision and set of criteria for pursuing future strategies for regulating controlled polymerizations.     

Artificial Light‐Gated Catalyst Systems

Having control over an entity or even an entire process is arguably the ultimate demonstration of its understanding and it will enable its potential to be fully exploited. With this in mind, chemists have not only been creating and optimizing a myriad of different catalysts for most (relevant) chemical reactions over the past decades, but have recently started to implement controlling elements into the catalyst design. These incorporated gates operate upon exposure to suitable control stimuli, and light represents perhaps the scientifically and technologically most attractive stimulus. In principle, irradiation can thereby induce activity and selectivity in a given catalyst system with high spatial and temporal control, leading to an overall localization and amplification of an optical signal and translation into chemical action. While nature has developed and utilized this concept, in particular in the processes of vision and photomovement, such artificial photocontrolled catalyst systems offer unique opportunities and have high potential for future applications. In this Review, we outline the general concept of light‐gated catalysis based on photocaged and also photoswitchable systems, and discuss relevant examples of the past and recent literature.     

Tunable and Photoswitchable Chemically Induced Dimerization for Chemo‐optogenetic Control of Protein and Organelle Positioning

The spatiotemporal dynamics of proteins and organelles play an important role in controlling diverse cellular processes. Optogenetic tools using photosensitive proteins and chemically induced dimerization (CID), which allow control of protein dimerization, have been used to elucidate the dynamics of biological systems and to dissect the complicated biological regulatory networks. However, the inherent limitations of current optogenetic and CID systems remain a significant challenge for the fine‐tuning of cellular activity at precise times and locations. Herein, we present a novel chemo‐optogenetic approach, photoswitchable chemically induced dimerization (psCID), for controlling cellular function by using blue light in a rapid and reversible manner. Moreover, psCID is tunable; that is, the dimerization and dedimerization degrees can be fine‐tuned by applying different doses of illumination. Using this approach, we control the localization of proteins and positioning of organelles in live cells with high spatial (μm) and temporal (ms) precision.     

仿生光响应智能纳米孔道的构筑及应用

在生命体中,很多生物过程都和光息息相关,例如光合作用过程和视觉感受系统等,而这些过程大都由生命体中对光敏感的蛋白质离子通道主导。近年来,受这些蛋白质离子通道的启发,具有光响应性的仿生智能固态纳米孔道广受关注。光响应纳米孔道具有灵活的空间和时间可控性,除了和生命过程息息相关,还在能源存储与转化、药物可控释放和分离等方面显示了巨大的应用前景。本综述主要从材料属性出发阐述光响应仿生智能纳米孔道的构筑和分类,并对其应用进行总结和展望。     

Fluorescent Probes for Selective Recognition of Hypobromous Acid: Achievements and Future Perspectives

Reactive oxygen species (ROS) have been implicated in numerous pathological processes and their homeostasis facilitates the dynamic balance of intracellular redox states. Among ROS, hypobromous acid (HOBr) has a high similarity to hypochlorous acid (HOCl) in both chemical and physical properties, whereas it has received relatively little attention. Meanwhile, selective recognition of endogenous HOBr suffers great challenges due to the fact that the concentration of this molecule is much lower than that of HOCl. Fluorescence-based detection systems have emerged as very important tools to monitor biomolecules in living cells and organisms owing to distinct advantages, particularly the temporal and spatial sampling for in vivo imaging applications. To date, the development of HOBr-specific fluorescent probes is still proceeding quite slowly, and the research related to this area has not been systematically summarized. In this review, we are the first to review the progress made so far in fluorescent probes for selective recognition and detection of HOBr. The molecular structures, sensing mechanisms, and their successful applications of these probes as bioimaging agents are discussed here in detail. Importantly, we hope this review will call for more attention to this rising field, and that this could stimulate new future achievements.     

A Singular System with Precise Dosing and Spatiotemporal Control of CRISPR‐Cas9

Several genome engineering applications of CRISPR‐Cas9, an RNA‐guided DNA endonuclease, require precision control of Cas9 activity over dosage, timing, and targeted site in an organism. While some control of Cas9 activity over dose and time have been achieved using small molecules, and spatial control using light, no singular system with control over all the three attributes exists. Furthermore, the reported small‐molecule systems lack wide dynamic range, have background activity in the absence of the small‐molecule controller, and are not biologically inert, while the optogenetic systems require prolonged exposure to high‐intensity light. We previously reported a small‐molecule‐controlled Cas9 system with some dosage and temporal control. By photocaging this Cas9 activator to render it biologically inert and photoactivatable, and employing next‐generation protein engineering approaches, we have built a system with a wide dynamic range, low background, and fast photoactivation using a low‐intensity light while rendering the small‐molecule activator biologically inert. We anticipate these precision controls will propel the development of practical applications of Cas9.     

Near‐Infrared Light‐Initiated Hybridization Chain Reaction for Spatially and Temporally Resolved Signal Amplification

Precise control over signal amplification provides unparalleled opportunities for diverse applications. However, spatiotemporally controlled amplification has not been realized because of the lack of a design methodology. The aim of this study was thus to develop a conceptual approach for remote control over signal amplification at a chosen time and site in living cells. This system was constructed by re‐engineering the functional units of the hybridization chain reaction (HCR) and combination with upconversion photochemistry, thus resulting in an activatable HCR with the high spatial and temporal precision of near‐infrared (NIR) light. As a proof of concept, we demonstrate the spatially and temporally resolved amplified imaging of messenger RNA (mRNA) with ultrahigh sensitivity in vitro and in vivo. Furthermore, by using a system targeting subcellular sites we have developed a new technique for NIR‐initiated amplified imaging of mRNA exclusively within a specific organelle.     

A Photocleavable Masked Nuclear‐Receptor Ligand Enables Temporal Control of C. elegans Development

The development and lifespan of C. elegans are controlled by the nuclear hormone receptor DAF‐12, an important model for the vertebrate vitamin D and liver X receptors. As with its mammalian homologues, DAF‐12 function is regulated by bile acid‐like steroidal ligands; however, tools for investigating their biosynthesis and function in vivo are lacking. A flexible synthesis for DAF‐12 ligands and masked ligand derivatives that enable precise temporal control of DAF‐12 function was developed. For ligand masking, photocleavable amides of 5‐methoxy‐N‐methyl‐2‐nitroaniline (MMNA) were introduced. MMNA‐masked ligands are bioavailable and after incorporation into the worm, brief UV irradiation can be used to trigger the expression of DAF‐12 target genes and initiate development from dauer larvae into adults. The in vivo release of DAF‐12 ligands and other small‐molecule signals by using photocleavable MMNA‐masked ligands will enable functional studies with precise spatial and temporal resolution.     

Reverse engineering of an affinity-switchable molecular interaction characterized by atomic force microscopy single-molecule force spectroscopy

Tunable and switchable interaction between molecules is a key for regulation and control of cellular processes. The translation of the underlying physicochemical principles to synthetic and switchable functional entities and molecules that can mimic the corresponding molecular functions is called reverse molecular engineering. We quantitatively investigated autoinducer-regulated DNA-protein interaction in bacterial gene regulation processes with single atomic force microscopy (AFM) molecule force spectroscopy in vitro, and developed an artificial bistable molecular host-guest system that can be controlled and regulated by external signals (UV light exposure and thermal energy). The intermolecular binding functionality (affinity) and its reproducible and reversible switching has been proven by AFM force spectroscopy at the single-molecule level. This affinity-tunable optomechanical switch will allow novel applications with respect to molecular manipulation, nanoscale rewritable molecular memories, and/or artificial ion channels, which will serve for the controlled transport and release of ions and neutral compounds in the future.     

Light-mediated inhibition of protein synthesis

The regulation of protein synthesis is vital for a host of cell biological processes, but investigating roles for protein synthesis have been hindered by the inability to selectively interfere with it. To inhibit protein synthesis with spatial and temporal control, we have developed a photo-releasable anisomycin compound, N-([6-bromo-7-hydroxycoumarin-4-yl]methyloxycarbonyl)anisomycin (Bhc-Aniso), that can be removed through exposure to UV light. The area of protein synthesis inhibition can be restricted to a small light-exposed region or, potentially, the volume of two-photon excitation if a pulsed IR laser is the light source. We have tested the compound's effectiveness with an in vitro protein-translation system, CHO cells, HEK293 cells, and neurons. The photo-released anisomycin can inhibit protein synthesis in a spatially restricted manner, which will enable the specific inhibition of protein synthesis in subsets of cells with temporal and spatial precision.     

Photochemical effect driven fluid behavior control in microscale pores and channels

Manipulating the fluid transport in the microscale pores and channels is playing a paramount role in the realization of the versatile functions of microfluidics. In recent years, using light to control the fluid behavior in the microchannels/pores has attracted many researchers’ attention due to the advantages of light such as non-contact stimulation, tunable excitation, high spatial and temporal resolution. With efforts, great achievements and progresses have been achieved for photochemical eff...     

DNA computation: a photochemically controlled AND gate

DNA computation is an emerging field that enables the assembly of complex circuits based on defined DNA logic gates. DNA-based logic gates have previously been operated through purely chemical means, controlling logic operations through DNA strands or other biomolecules. Although gates can operate through this manner, it limits temporal and spatial control of DNA-based logic operations. A photochemically controlled AND gate was developed through the incorporation of caged thymidine nucleotides into a DNA-based logic gate. By using light as the logic inputs, both spatial control and temporal control were achieved. In addition, design rules for light-regulated DNA logic gates were derived. A step-response, which can be found in a controller, was demonstrated. Photochemical inputs close the gap between DNA computation and silicon-based electrical circuitry, since light waves can be directly converted into electrical output signals and vice versa. This connection is important for the further development of an interface between DNA logic gates and electronic devices, enabling the connection of biological systems with electrical circuits.     

Photochemical control of biological processes

Photochemical regulation of biological processes offers a high level of control to study intracellular mechanisms with unprecedented spatial and temporal resolution. This report summarizes the advances made in recent years, focusing predominantly on the in vivo regulation of gene function using irradiation with UV light. The majority of the described applications entail the utilization of photocaging groups installed either on a small molecule modulator of biomolecular function or directly on a biological macromolecule itself.     

Construction and application of photoresponsive smart nanochannels

In living organisms, many biological processes are inextricably linked with light, such as the photosynthesis systems and rhodopsin. Hence, construction of light-sensitive biomimetic-nanochannels, which can realize the functions of cells and other membrane structures with high degree of spatial and temporal control, is particularly attractive and challenging. As a cornerstone of light-sensitive nanochannels, the photoresponsive materials are a big family and at their mature stage after several decades of development, which can provide different strategies to construct biomimetic photoresponsive nanochannels. In this review, we mainly summarize the construction and applications of photoresponsive nanochannels on the basis of various photoresponsive materials. The construction of photoresponsive nanochannels can be classified into four categories: photoresponsive inorganic nanochannels based on inorganic-compound-based photonic sensitive materials; photoresponsive organic nanochannels based on organic-compound-based photonic sensitive materials; photoresponsive polymers nanochannel based on photoresponsive polymers materials and potential photoresponsive nanochannels based on other photoresponsive materials. After introducing the construction of photoresponsive nanochannels, the review highlights some of the most recent applications of photoresponsive nanochannels in separation, energy conversion and storage, drug delivery and so on.     

A Sunscreen-Based Photocage for Carbonyl Groups

Photolabile protecting groups (PPGs) have been exploited in a wide range of chemical and biological applications, due to their ability to provide spatial and temporal control over light-triggered activation. In this work, we explore the concept of a new photocage compound based on the commercial UVA/UVB filter oxybenzone (OB; 2-hydroxy-4-methoxybenzophenone) for photoprotection and controlled release of carbonyl groups. The point here is that oxybenzone not only acts as a mere PPG, but also provides, once released, UV photoprotection to the carbonyl derivative. This design points to a possible therapeutic approach to reduce the severe photoadverse effects of drugs containing a carbonyl chromophore.