Biological nanoparticles found in living systems possess distinct molecular architectures and diverse functions. Glycogen is a unique biological polysaccharide nanoparticle fabricated by nature ...through a bottom‐up approach. The biocatalytic synthesis of glycogen has evolved over time to form a nanometer‐sized dendrimer‐like structure (20–150 nm) with a highly branched surface and a dense core. This makes glycogen markedly different from other natural linear or branched polysaccharides and particularly attractive as a platform for biomedical applications. Glycogen is inherently biodegradable, nontoxic, and can be functionalized with diverse surface and internal motifs for enhanced biofunctional properties. Recently, there has been growing interest in glycogen as a natural alternative to synthetic polymers and nanoparticles in a range of applications. Herein, the recent literature on glycogen in the material‐based sciences, including its use as a constituent in biodegradable hydrogels and fibers, drug delivery vectors, tumor targeting and penetrating nanoparticles, immunomodulators, vaccine adjuvants, and contrast agents, is reviewed. The various methods of chemical functionalization and physical assembly of glycogen nanoparticles into multicomponent nanodevices, which advance glycogen toward a functional therapeutic nanoparticle from nature and back again, are discussed in detail.
Glycogen is one of nature's unique biological polysaccharide nanoparticles, which holds promise as a material for biomedical, including therapeutic, applications. The recent literature on advancing glycogen as a building block for advanced biofunctional materials is reviewed.
Most cells take simple sugar (α-
d
-glucose) and assemble it into highly dense polysaccharide nanoparticles called glycogen. This is achieved through the action of multiple coupled-enzymatic ...reactions, yielding the cellular store of polymerised glucose to be degraded in times of metabolic need. These nanoparticles can be readily isolated from various animal tissues and plants, and are commercially available on a large scale. Importantly, glycogen is highly water soluble, non-toxic, low-fouling, and biodegradable, making it an attractive nanoparticle for use in nanomedicine, for both diagnosing and treating disease. This concept has been pursued actively recently, with exciting results on a variety of fronts, especially for targeting specific tissues and delivering nucleic acid and peptide cargo. In this perspective, the role of glycogen in nanomedicine going forward is discussed, with opportunities highlighted of where these sugary nanoparticles fit into the problem of treating disease.
Glycogen is a biomaterial nanoparticle composed of sugar. In this perspective, the opportunities of glycogen in nanomedicine going forward is discussed.
Polymer brush surfaces that alter their physical properties in response to chemical stimuli have the capacity to be used as new surface‐based sensing materials. For such surfaces, detecting the ...polymer conformation is key to their sensing capabilities. Herein, we report on FRET‐integrated ultrathin (<70 nm) polymer brush surfaces that exhibit stimuli‐dependent FRET with changing brush conformation. Poly(N‐isopropylacrylamide) polymers were chosen due their exceptional sensitivity to liquid mixture compositions and their ability to be assembled into well‐defined polymer brushes. The brush transitions were used to optically sense changes in liquid mixture compositions with high spatial resolution (tens of micrometers), where the FRET coupling allowed for noninvasive observation of brush transitions around complex interfaces with real‐time sensing of the liquid environment. Our methods have the potential to be leveraged towards greater surface‐based sensing capabilities at intricate interfaces.
FRET chemistry was integrated within stimuli‐responsive polymer brush layers on planar substrates for spatial sensing of changing polymer conformations. Sensing was demonstrated for a variety of liquid mixture compositions, including high‐resolution observation of lateral differences in polymer conformation at immiscible liquid interfaces (see picture), thus offering great potential to be leveraged for new surface‐based sensing devices.
Identifying changes in the nanoscopic domain is a key challenge in the physicochemical sciences, where great interest is on sensing complex processes that involve cellular biochemical reactions, ...chemical heterogeneities, contact forces, and other interfacial phenomena. This has stimulated the development of diverse materials that allow subtle nanoscopic environments to be "seen". The challenge in the nano‐domain has always been the ability to sense changes on the minute scale and rapidly transduce the information out for macroscopical observation. Ideally, materials should inform when processes are occurring. Recently, new systems that leverage established concepts with fluorescence‐ and plasmonic‐based sensing have been devised, which has reinvigorated the domain, where functional polymers coupled in specific architectures to transducing motifs allow for a new basis of messenger materials to be realized. The key aspect in this regard is that the polymers allow for sensing to be achieved only when they are carefully coupled to the amplification system. In this perspective, the role of specific functional polymer architectures for the realization of nano‐to‐macro sensing of subtle nano‐messengers is discussed and where the exciting field of messenger materials is seen moving forward is pointed out.
Materials that are capable of responding to nano‐scale stimuli by dynamically producing a macroscopic signal, termed messenger materials, offer outstanding potential for use in new sensing technologies that allow a material to inform when something is changing. A perspective is offered on where this exciting branch of material sciences leading can be seen as the field progresses forward.
Surfaces that respond to local environmental stimuli offer intriguing possibilities for new surface‐based sensing concepts to emerge. An attractive concept is to push beyond the milli‐ to micrometer ...lateral resolution limit in sensing, toward the ultimate surface‐sensitive device; one capable of real‐time sensing of the nanoscopic, or molecular “touch.” This sensing needs an approach that is capable of spatially transducing information on nanotouch. Polymer brushes are a class of surface that provides dramatic changes in surface properties depending on stimuli that affect the conformation of end‐tethered polymer chains. However, the brush response is typically quantified by measuring changes in polymer brush “height”. That is, the ensemble average distance over which polymer density exists away from the anchoring surface (i.e., a single parameter to describe the surface). Moving beyond this conceptual paradigm of quantifying the ensemble average height in a single dimension over the entire surface under applied stimuli, developing methods for spatially resolving chain conformation has the very real potential to lead to extraordinary possibilities in the applied sciences. In this perspective, the current paradigms and methods forward for extracting rich details on polymer brush conformational dynamics that is spatially resolved, which can lead to new understandings of surface contact, are discussed and pointed out.
Polymer brush surfaces provide an intriguing platform with which to engineer nanoscale surface‐based sensing devices. In this perspective, methods and benefits of resolving polymer brush conformation spatially across a surface are discussed, and where the polymer brush field still has room to move with respect to building surface sensing devices.
Water is a unique solvent that is ubiquitous in biology and present in a variety of solutions, mixtures, and materials settings. It therefore forms the basis for all molecular dynamics simulations of ...biological phenomena, as well as for many chemical, industrial, and materials investigations. Over the years, many water models have been developed, and it remains a challenge to find a single water model that accurately reproduces all experimental properties of water simultaneously. Here, we report a comprehensive comparison of structural and dynamic properties of 30 commonly used 3-point, 4-point, 5-point, and polarizable water models simulated using consistent settings and analysis methods. For the properties of density, coordination number, surface tension, dielectric constant, self-diffusion coefficient, and solvation free energy of methane, models published within the past two decades consistently show better agreement with experimental values compared to models published earlier, albeit with some notable exceptions. However, no single model reproduced all experimental values exactly, highlighting the need to carefully choose a water model for a particular study, depending on the phenomena of interest. Finally, machine learning algorithms quantified the relationship between the water model force field parameters and the resulting bulk properties, providing insight into the parameter–property relationship and illustrating the challenges of developing a water model that can accurately reproduce all properties of water simultaneously.
The manipulation of interfacial properties has broad implications for the development of high‐performance coatings. Metal–phenolic networks (MPNs) are an emerging class of responsive, adherent ...materials. Herein, host–guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin‐based MPNs are highly permeable (even to high molecular weight polymers: 250–500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).
Networking: The synthesis of host phenolic building blocks, consisting of macrocyclic host rings and phenolic coordinating functions, enables the rapid assembly of adherent conformal metal–phenolic network coatings on diverse substrates with modular and tunable interfacial properties using host–guest chemistry.
Mixtures of short-chain alcohols and water produce anomalous thermodynamic and structural quantities, including molecular segregation into water-rich and alcohol-rich components. Herein, we used ...molecular dynamics simulations with polarizable models to investigate interactions that could drive the self-association of water molecules in mixtures with methanol (MeOH). As water was diluted with MeOH, significant changes in the distribution of molecules and solvation properties occurred, where water exhibited a clear preference for self-association. When common structural quantities were analyzed, it was found that there was a clear reduction in water–water hydrogen bonding and tetrahedral order (both in terms of typical bulk behavior), contrary to the observed water self-association. However, when dipolar dispersion forces between all molecules as a function of system composition were analyzed, it was found that water–water dipolar interactions became significantly stronger with dilution (6-fold stronger interaction in 75% MeOH compared to 0% MeOH). This was only observed for water, where MeOH–MeOH interactions became weaker as the systems were more dilute in MeOH. These forces result from specific dipole orientations, likely occurring to adopt lower energy configurations (i.e., head-to-tail or antiparallel). For water, this may result from lost other interactions (e.g., hydrogen bonding), leading to more rotational freedom between the dipole moments. These intriguing changes in dipolar interactions, which directly result from structural changes, can therefore explain, in part, the driving force for water self-association in MeOH–water mixtures.
The self-assembly of molecular building blocks into well-defined macroscopic materials is desirable for developing emergent functional materials. However, the self-assembly of molecules into ...macroscopic materials remains challenging, in part because of limitations in controlling the growth and robustness of the materials. Herein, we report the molecular self-assembly of nano- to macroscopic free-standing materials through the coordination of metals with natural phenolic molecules. Our method involves a simple and scalable solution-based template dipping process in precomplexed metal–phenolic solutions, enabling the fabrication of free-standing macroscopic materials of customized architectures (2D and 3D geometries), thickness (about 10 nm to 5 μm), and chemical composition (different metals and phenolic ligands). Our macroscopic free-standing materials can be physically folded and unfolded like origami, yet are selectively degradable. Furthermore, metal nanoparticles can be grown in the macroscopic free-standing films, indicating their potential for future applications in biotechnology and catalysis.
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