Nature of water molecules in hydrogels based on a liquid crystalline cellulose derivative

Tissue development and regeneration are governed by processes that span subcellular signaling, cell-cell interactions, and the integrated mechanical properties of cellular collectives with their extracellular matrix. Synthetic biomaterials that can emulate the hierarchical structure and supracellular mechanics of living systems are paramount to the realization of regenerative medicine. Recent reports detail directed cell alignment on mechanically anisotropic but stiff liquid crystalline polymer networks (LCNs). While compelling, the potential implementation of these materials as tissue engineering scaffolds may be hindered by the orders of magnitude larger stiffness than most soft tissue. Accordingly, this report prepares liquid crystalline hydrogels (LCHs) that synergize the anisotropic mechanical properties intrinsic to LCNs with the cytocompatibility and soft mechanics of PEG hydrogels. LCH are prepared via sequential oligomerization and photopolymerization reactions between liquid crystalline (LC) monomers and poly(ethylene glycol) (PEG)-dithiol. Despite their low liquid crystalline content, swollen LCH oligomers are amenable to rheological alignment via direct ink write 3D printing. Mechanically anisotropic LCHs support C2C12 myoblast culture on their surface and direct their alignment in the stiffest direction. Further, C2C12s can be encapsulated within LCH oligomers and 3D-printed, whereby mechanical anisotropy of the LCH directs myoblast polarization in 3D.

We demonstrate that 14-helical beta-peptides can self-assemble to form lyotropic liquid crystalline (LC) phases in water. beta-Peptides 1-4 were designed to form globally amphiphilic 14-helices of increasing length. Optical microscopy showed that several of these beta-peptides formed LC phases in aqueous solutions at concentrations as low as 2.5 wt % (15 mM). Liquid crystallinity appears to require the adoption of a globally amphiphilic conformation because a scrambled sequence, 5, does not display LC behavior. Thermal stability and reversibility of LC phase formation were assessed by variable temperature 2H NMR spectroscopy and optical microscopy. The LC phase formed by beta-peptide 3 at 10 wt % is disrupted above 40 degrees C in D2O and re-forms within minutes upon cooling. LC phase behavior for solutions of 3 is influenced by concentration and net charge. These studies demonstrate that highly folded 14-helical beta-peptides can produce LC phases at shorter lengths than do alpha-helical alpha-peptide mesogens and can provide a basis for tailoring properties of LC phases for future applications.

Liquid crystalline hydrogel (LCH) is synthesized through simultaneous polymerization of hydrophobic and hydrophilic monomers in an oil-in-water emulsion, resulting in phase-separated liquid crystalline network (LCN) embedded in a hydrogel matrix. This material features some properties and functions of both LCN and hydrogel, displaying stable LC phase over repeated hydration and dehydration cycles of the hydrogel matrix. Using mechanically stretched and photocrosslinked LCH, the thermally induced LC-isotropic phase transition in LCN domains can be translated into reversible macroscopic deformation of the LCH. Moreover, the LCH exhibits water absorption-controlled shape memory effect.

ABSTRACTResearch in the field of liquid crystalline polymers has recently witnessed the introduction of liquid crystalline hydrogels. Here, we report the synthesis and characterization of a new liquid crystalline network featuring elastomeric softness, water‐swelling and shape memory characteristics. By comparing with a nonmesogenic network prepared using the same procedure, we reveal structure–property relationships of the liquid crystalline and crystalline polymer networks. Wide angle and small angle X‐ray scattering studies were used to examine the liquid crystalline ordering in both dry and hydrated states. Such ordering was found to be related to the observed shape memory and actuation (two‐way shape memory) properties and these phenomena are highlighted with demonstrations of shape change in response to heat and water stimuli. This study provides insight into the mechanisms affecting the shape evolution of water activated anisotropic liquid crystalline hydrogels and enables the future design of materials or devices for a variety of applications such as biomaterials interacting with body fluids in a hydrated state. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2016,54, 38–52

Hydrogels are frequently utilized as three-dimensional matrices for the culture and regeneration of soft tissues, but one challenge with the existing hydrogels is that, though the natural extracellular matrix of tissues may be ordered, there are few biocompatible ways to incorporate anisotropy within hydrogels. Liquid crystalline (LC) polymers are well suited for this because of their combination of molecular ordering and polymer elasticity; however, the hydrophobic nature of LC monomers has hindered their polymerization into hydrogels under cytocompatible conditions. This work reports on the generation of main-chain LC hydrogels in aqueous media and the ability of LC phases to affect mesenchymal stem cell behavior. The synthesis results in high gel fraction materials, and calorimetry, thermomechanical analysis, and X-ray scattering show that the networks organize into LC phases in the dry and hydrogel states. Human mesenchymal stem cells (hMSCs) cultured within the hydrogels show excellent viability, and hMSC proliferation proceeds at a faster rate in LC hydrogels compared to non-LC hydrogels. TThe result is a new synthetic approach for calamitic liquid crystalline hydrogels, which support the encapsulation and culture of human stem cells and are expected to enable applications as anisotropic and responsive substrates for tissue engineering and regenerative medicine.

In this chapter, we present hierarchically organized nanostructures formed from lyotropic liquid crystalline (LC) phases. The nano-, micro-, and macroscopic structural hierarchy arises from the kinetic stability of various lyotropic phases dispersed in oilin-water (O/W) or water-in-oil (W/O) emulsions. When an O/W emulsion consists of a dispersion of LC nanoparticles stabilized by certain stabilizers, it is called an ISAsome, that is, an internally self-assembled particle. In contrast, when the water droplets are dispersed in a continuous film of LC nanostructures, they are called W/O-nanostructured emulsions, which do not require a stabilizing agent. Both emulsions exhibit fascinating properties that can be tuned to a great extent. Such tunability proliferates their performance in various applications. Herein, we discuss the formation, multiscale structure, properties, and their modulation for the aforementioned superstructures formed from LC phases. Focusing further on ISAsomes we present Pickering emulsions stabilized by using various nanoparticles, including synthetic clay Laponite and silica nanoparticles. The transfer of hydrophobic components among several differently nanostructured ISAsomes was studied by time-resolved X-ray scattering; the effects of Isasome-forming components are also illustrated. The continuous aqueous region of ISAsome dispersions can be loaded with water-soluble polymers that form thermoreversible hydrogels. This enables the entrapment of ISAsome systems into such hydrogel networks. Subsequent drying of these loaded systems facilitates immobilization of ISAsomes, which can be easily restored by rehydration of the loaded dry films. The formation of hydrogels in the aqueous reservoirs of W/O-nanostructured emulsions also proved advantageous in terms of tuning their viscosity and, in some cases, enhancing their stability. The current contribution covers systems with diverse structural hierarchy, ranging from equilibrium liquid crystalline nanostructures to the systems with multiple orders of length scales in their structure.

Self-Assembly in a Mixture of Two Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) Copolymers in Water

X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been combined to study the modifications and growth of alumina thin films on NiAl(001) induced by exposure to water vapor at low pressure (10−6 mbar) and by immersion in ultrapure liquid water at room temperature. The film thickness and stoichiometry, as well as the alloy composition changes, were analyzed by angle-resolved XPS measurements. Ultrathin (∼0.7 nm) hydroxylated native oxide films were compared to thicker (∼4 nm) anhydrous and oxygen-deficient thermal oxide films grown at 900 °C under low air pressure (10−4 mbar). The results show that immersion in liquid water causes the formation of one to two equivalent additional monolayers of aluminum oxide at the interface between the native oxide film and the alloy, suggesting anion transport along the oxide/alloy interface after entry at intergranular oxide sites. The hydroxylated oxide surface remains unchanged. In contrast, immersion of the thicker thermal oxide films in li...

Biological hydrogels play important physiological roles in the body. These hydrogels often contain ordered subdomains that provide mechanical toughness and other tissue-specific functionality. Filamentous bacteriophages are nanofilaments with a high aspect ratio that can self-assemble into liquid crystalline domains that could be designed to mimic ordered biological hydrogels and can thus find applications in biomedical engineering. We have previously reported hydrogels of pure cross-linked liquid crystalline filamentous phage formed at very high concentrations exhibiting a tightly packed microstructure and high stiffness. In this work, we report a method for inducing self-assembly of filamentous phage into liquid crystalline hydrogels at concentrations that are several orders of magnitude below that of lyotropic liquid crystal formation, thus creating structural order but a less densely packed microstructure. Hybrid hydrogels of M13 phage and bovine serum albumin (0.25 w/v%) were formed and shown to adsorb up to 16× their weight in water. Neither component gelled on its own at the low concentrations used, suggesting synergistic action between the two components in the formation of the hydrogel. The hybrid hydrogels exhibited repetitive self-healing under physiological conditions and at room temperature, autofluorescence in three channels, and antibacterial activity toward Escherichia coli host cells. Furthermore, the hybrid hydrogels exhibited a more than 2× higher ability to pack water compared to BSA-only hydrogels and 2× lower compression modulus compared to tightly packed M13-only hydrogels, suggesting that our method could be used to create hydrogels with tunable mechanical properties and pore structure through the addition of globular proteins, while maintaining bioactivity and microscale structural order.

Biological hydrogels play important physiological roles in the body. These hydrogels often contain ordered subdomains that provide mechanical toughness and other tissue-specific functionality. Filamentous bacteriophages are nanofilaments with a high aspect ratio that can self-assemble into liquid crystalline domains that could be designed to mimic ordered biological hydrogels and can thus find application in biomedical engineering. We have previously reported hydrogels of pure crosslinked liquid crystalline filamentous phage formed at very high concentrations exhibiting a tightly packed microstructure and high stiffness. In this work, we report a method for inducing self-assembly of filamentous phage into liquid crystalline hydrogels at concentrations that are several orders of magnitude below that of lyotropic liquid crystal formation, thus creating structural order, but a less densely packed hydrogel. Hybrid hydrogels of M13 phage and bovine serum albumin (0.25 w/v%) were formed and shown to adsorb up to 16 its weight in water. Neither component gelled on its own at the low concentrations used, suggesting synergistic action between the two components in forming the hydrogel. The hybrid hydrogels exhibited repetitive self-healing under physiological conditions and at room temperature, autofluorescence in three channels, and antibacterial activity towards Escherichia coli host cells. Furthermore, the hybrid hydrogels exhibited more than 2 higher ability to pack water compared to BSA-only hydrogels and 2 higher flexibility (lower compression modulus) compared to tightly packed M13-only hydrogels, suggesting that our method could be used to create hydrogels with tunable mechanical properties through the addition of globular proteins, while maintaining structural order at the microscale.

Cross-linked gels of poly(L-glutamic acid) (PGA) possessing cholesteric or nematic liquid-crystalline (LC) order were prepared from the corresponding LC gels of poly(γ-benzyl L-glutamate). Optical anisotropy measured by transmitted light intensity through cholesteric LC hydrogels between crossed polarizers showed reversible changes with the alternation of pH values. Mechanical anisotropy was also found in the nematic LC hydrogels.

Recent studies demonstrated the potential therapeutic use of newly synthesized omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglycerides owing to their beneficial health effects in various disorders including cancer and inflammation diseases. To date, the research was mainly focused on exploring the biological effects of these functional lipids. However, to the best of our knowledge, there is no report on the hydration-mediated self assembly of these lipids that leads to the formation of nanostructures, which are attractive for use as vehicles for the delivery of drugs and functional foods. In the present study, we investigated the temperature-composition phase behaviour of eicosapentaenoic acid monoglyceride (MAG-EPA), which is one of the most investigated ω-3 PUFA monoglycerides, during a heating-cooling cycle in the temperature range of 5-60 °C. Experimental synchrotron small-angle X-ray scattering (SAXS) evidence on the formation of a dominant inverse hexagonal (H2) lyotropic liquid crystalline phase and its temperature-induced transition to an inverse micellar solution (L2 phase) is presented for the fully hydrated bulk MAG-EPA system and its corresponding dispersion. We produced colloidal MAG-EPA hexosomes with an internal inverse hexagonal (H2) lyotropic crystalline phase in the presence of F127, a well-known polymeric stabilizer, or citrem, which is a negatively charged food-grade emulsifier. In this work, we report also on the formation of MAG-EPA hexosomes by vortexing MAG-EPA in excess aqueous medium containing F127 at room temperature. This low-energy emulsification method is different than most reported studies in the literature that have demonstrated the need for using a high-energy input during the emulsification step or adding an organic solvent for the formation of such colloidal nonlamellar liquid crystalline dispersions. The designed nanoparticles hold promise for future drug and functional food delivery applications due to their unique structural properties and the potential health-promoting effects of MAG-EPA.

Phase diagram and surface adsorption behavior of benzyl dimethyl hexadecyl ammonium bromide in a binary surfactant-water system

Looking for the primary rainbow in starlight that is reflected by exoplanets appears to be a promising method to search for liquid water clouds in exoplanetary atmospheres. Ice water clouds, that consist of water crystals instead of water droplets, could potentially mask the rainbow feature in the planetary signal by covering liquid water clouds. Here, we investigate the strength of the rainbow feature for exoplanets that have liquid and icy water clouds in their atmosphere, and calculate the rainbow feature for a realistic cloud coverage of Earth. We calculate flux and polarization signals of starlight that is reflected by horizontally and vertically inhomogeneous Earth--like exoplanets, covered by patchy clouds consisting of liquid water droplets or water ice crystals. The planetary surfaces are black. On a planet with a significant coverage of liquid water clouds only, the total flux signal shows a weak rainbow feature. Any coverage of the liquid water clouds by ice clouds, however, dampens the rainbow feature in the total flux, and thus the discovery of liquid water in the atmosphere. On the other hand, detecting the primary rainbow in the polarization signal of exoplanets appears to be a powerful tool for detecting liquid water in exoplanetary atmospheres, even when these clouds are partially covered by ice clouds. In particular, liquid water clouds covering as little as 10%-20% of the planetary surface, with more than half of these covered by ice clouds, still create a polarized rainbow feature in the planetary signal. Indeed, calculations of flux and polarization signals of an exoplanet with a realistic Earth--like cloud coverage, show a strong polarized rainbow feature.

Diabetes mellitus (DM) significantly impairs wound healing, often leading to chronic wounds with limited effective treatment options. Existing treatments often fail to provide sustained therapeutic effects, underscoring the need for advanced biomaterial-based approaches to enhance tissue regeneration. This study aimed to evaluate the wound healing efficacy of stromal cell-derived factor-1 alpha (SDF-1α)-loaded lipid liquid crystalline (LLC) hydrogel in both in vitro and in vivo models. A scratch wound healing assay was conducted on human dermal fibroblast (HDF) cells treated with allantoin (100 µg), LLC hydrogel, SDF-1α 50 ng/LLC, SDF-1α 25 ng/LLC, SDF-1α 25 ng, and a negative control. In vivo studies utilized diabetic rats (n = 10 per group) with full-thickness wounds, treated with LLC hydrogel, SDF-1α 300 ng/LLC, and polyhexamethylene biguanide (PHMB), compared to a negative control. Wound closure rates were measured on days 3, 7, 14, and 21, and histopathological analysis was performed. The SDF-1α/LLC hydrogel significantly enhanced HDF cell migration, showing a 32.8% improvement over the control (P < 0.001). Diabetic wounds treated with SDF-1α/LLC hydrogel demonstrated 51.4% faster closure by day 14 compared to the control (P < 0.001), with complete closure achieved by day 21. By day 21, SDF-1α/LLC and LLC hydrogels achieved 100% wound closure, while PHMB-treated wounds also exhibited significant healing, reaching 97.86% closure. Histological analysis revealed increased fibroblast proliferation, reduced inflammation, enhanced collagen deposition, and greater epithelial thickness, particularly in the SDF-1α/LLC group. The SDF-1α-loaded LLC hydrogel significantly enhances fibroblast migration, accelerates wound closure, and promotes tissue regeneration, making it a promising candidate for diabetic wound care.