Self-assembly Process Research Articles

Co-assembly-Directed Enhancement of the Thermochromic Reversibility and Solvatochromic Selectivity of Supramolecular Polydiacetylene.

The construction of functional materials via the co-assembly of multimolecular systems has recently emerged as a fascinating topic. The co-assembled multicomponent could promote the evolution of supramolecular assemblies into a high-order nanoarchitecture with improved functional properties. We report the successful preparation of a dual-functional polydiacetylene (MCPDA-Tz-CA) having thermochromic and solvatochromic properties via facile co-assembly of MCDA-Tz and cyanuric acid (MCDA-Tz-CA) followed by ultraviolet-induced polymerization. Molecular packing patterns from powder X-ray diffraction and density functional theory calculations of molecular self-assembly processes confirm highly ordered co-assembled lamellar structures. MCPDA-Tz-CA showed excellent reversible thermochromism properties when the temperature was increased from 30 to 150 °C with a reversible blue-to-red color transition that could be detected by the naked eye. Also, MCPDA-Tz-CA displayed selective blue-to-red solvatochromism against dimethylformamide and dimethyl sulfoxide. Detailed investigations revealed that the enhanced thermochromic reversibility and solvatochromic selectivity could be attributed to the hydrogen-bonding interactions and the formation of a network structure in the MCDA-Tz/cyanuric acid co-assembly. Our research opens a promising route for improving the performance of functional materials via noncovalent multicomponent arrangements at the molecular level.

Investigating micelle formation in systems with benzethonium chloride and n-lauroyl sarcosine sodium salt: The impact of thermal effects and ethyl lactate concentration using volumetric, statistical, acoustic, and molecular dynamic methods

Surface active agents (SAAs) are versatile molecules that possess the ability to serve as multifunctional ingredients in a wide range of consumer products across various industrial sectors. These molecules can act as wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, and more. The objective of this study was to evaluate the effect of temperature, and ethyl lactate concentration on micelle formation in systems containing benzethonium chloride (BC) and N-lauroyl sarcosine sodium salt (NLSS). The experimental measurements were conducted at three equidistant temperatures i.e., 298.15 K to 318.15 K and pressure, P=0.1 MPa. Several volumetric as well as compressibility parameters including apparent molar properties (Vϕ,Kϕ,S), partial molar properties (Vϕ°,Kϕ,S°), transport properties (ΔtrVϕ°,ΔtrKϕ,S°), hydration number, etc. have been evaluated. A Bayesian two-factor design with uninformative priors was used to analyze the values of Vϕ°,and Kϕ,S°. It was possible to determine that the temperature factors, and the ethyl lactate (EL) addition significantly influence the results for Vϕ° while for Kϕ,S°it is not appreciable at 5 and 10 % in EL concentration when BC and NLSS systems is compared. The simulations of the micellization process show the impact of temperature, particularly in the presence of ethyl lactate, is evident in the structural and dynamic changes observed in the micelles. Specifically, as the temperature rises from 298.15 K to 318.15 K, the self-assembly process becomes more spontaneous and accelerated, leading to larger and more spherical micelles. These alterations in micelle size, shape, and orientation enhance their capacity to effectively solubilize hydrophobic substances. The computational simulations demonstrated that BC molecules exhibit spontaneous aggregation at the interface of polar-nonpolar systems, resulting in the formation of a monolayer. In this monolayer, the heads of the molecules are oriented towards the polar phase, while the hydrophobic tails are in the nonpolar phase. Similarly, the NLSS system exhibits a continuous and gradual process of self-organization over a period of 120 ns, where NLSS molecules naturally come together to create a single layer arrangement at the zigzag-shaped boundary.

Synergistic enhancement of oil-water separation and flame retardant properties of melamine sponges based on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and perfluorinated compounds

Facing the escalating issue of industrial wastewater discharge and its profound environmental repercussions, the creation of novel sponge materials that excel in oil-water separation while incorporating flame retardancy becomes critically urgent. Despite their superior absorption capabilities, conventional oil-water separation sponges typically overlook flame retardant features, a limitation that curtails their applicability. To address this gap, we have developed a multifunctional hydrophobic sponge through a sophisticated multi-step chemical self-assembly process. This method grafts 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and perfluorinated compounds onto melamine foam (MF), yielding a composite material designated as DOPO-PF@MF. DOPO-PF@MF boasts a dual functionality of hydrophobicity and flame retardance. Its modified surface exhibits a pronounced hydrophobic-lipophilic balance, with a static water contact angle of 134°. It also displays favorable wetting characteristics towards various organic solvents, such as methanol, ethanol, dimethylformamide, dichloromethane, and hexane. This material demonstrates an impressive adsorption capacity for these solvents, with the adsorption-desorption capacity for ethanol remaining consistent over ten cycles. Furthermore, DOPO-PF@MF efficiently separates emulsions of methylene chloride and water, showcasing its versatility. Moreover, DOPO-PF@MF exhibits commendable chemical resilience under extreme temperatures, ranging from 0 °C to 100 °C, and withstands both acidic and alkaline conditions (pH 1–14), preserving its structural integrity against corrosive substances. Most notably, it surpasses unmodified melamine foam in flame retardancy. The incorporation of DOPO fortifies the material's resistance to high-temperature ignition, effectively inhibiting flame propagation and reducing burn rate, enhancing safety measures.

Refining Mn(III) Active Sites in MnO2-Based Self-Assembled Electrodes Via Oxygen Vacancy Induction to Enhance Oxygen Reaction Performance in Zinc-Air Batteries

Rechargeable zinc-air batteries are considered as a promising candidate for next-generation electrochemical energy conversion devices due to their safety, low cost, and high theoretical capacity/ energy density. Over the past few decades, α-MnO2-based electrodes have demonstrated their excellent performance and competitiveness in oxygen catalytic reactions. (1) According to eg filling theory, Mn(III) (t2g3eg1) sites in [MnO6] octahedral unit deliver superior bifunctional activity compared to Mn(II) (t2g3eg2) and Mn(IV) (t2g3eg0) sites.(2) However, the presence of unpaired single electrons of the Mn(III) site leads to low thermodynamic stability. Introducing oxygen vacancies to promote the electron rearrangement of the [MnO6] unit is a promising approach for enhancing the durability of Mn(III) active sites. Herein, we construct an oxygen-vacancy-enhanced MnO2-based electrode via a self-assembly process (NiCo2O4-MnO2@Ni foam). The intrinsic oxygen catalytic activity of NiCo2O4-MnO2@Ni foam is significantly improved by forming abundant highly stable Mn(III) active sites, which accelerate the mass transfer ability. As expected, the NiCo2O4-MnO2@Ni foam shows good bifunctional activity with a low overpotential of 0.69 V. The zinc-air battery assembled by NiCo2O4-MnO2@Ni foam exhibits a high peak power density of 576 mW cm-2, surpassing that of the Pt/C-Ir/C electrode. Additionally, benefiting from its stable flower-shaped hierarchical structure, the self-assembled electrode demonstrates long-term charge-discharge cycling stability, which lasts over 800 hours. This work provides innovative insights into enhancing MnO2-based electrodes by oxygen vacancy introduction.References N. Xu, Q. Nie, L. Luo, C. Z. Yao, Q. Gong, Y. Liu, X. Zhou, and J. Qiao, ACS applied materials & interfaces (2018).Z. Yin, R. He, H. Xue, J.-M. Chen, Y. Wang, X. Ye, N. Xu, J. Qiao and H. Huang, Energy Materials (2022).

(Invited) Single-Walled Carbon Nanotube Functionalization Strategies for Monitoring Enzymatic Activity and Inhibition

Semiconducting single-walled carbon nanotubes (SWCNTs) fluoresce in the near-infrared range, which overlaps with the transparency window of biological samples, and they do not photobleach or blink. Moreover, they benefit from biocompatibility and the large surface area available for functionalization. Using tailored surface functionalization, SWCNTs can be rendered optical nanosensors, such that surface binding events or changes in the local proximity of the nanotubes translate to a modulation of the emitted fluorescence. This approach was successfully used to demonstrate the detection of small molecules, volatiles, bacteria, microRNA, proteins, metals, self-assembly processes, and active processes in vivo. We will discuss different strategies for monitoring enzymatic activity and inhibition using SWCNT-based sensors, including the incorporation of the enzyme’s target bond within a synthetic molecular complex used for suspending the SWCNTs, or by the detection of the product of the enzyme hydrolytic activity. We will also highlight recent applications of these techniques in clinically relevant samples. These findings not only showcase the potential of near-infrared fluorescent SWCNT in tracking enzymatic activity but also underscore their promising role in advancing biomedical research and applications.

Unsuspected Organometallic Fibers Used As Potential Separators for Supercapacitors Device

Since the last decade, the interest of organic frameworks for electrochemical application the been more studied.1 In general, very few works have been found in the literature. We can mainly mention the use of these derivatives in the presence of inorganic materials both to form solid electrolytes or to protect electrodes. For example, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (H4DOTA) has been used to functionalize PVA to coat the surface of the negative electrode in order to suppress its degradation.2 This resulted in the improvement of the electrochemical properties of the LMNO/graphite cell. Recently, Kim et al. reported the addition of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane to a carbonate-based electrolyte intended to stabilize the Li metal-electrolyte interface by improving the solid electrolyte interphase.3 More recently, Liu et al. reported a novel carbonyl network polymer NP4 used as a cathode material for organic lithium batteries.4 Very few examples of fully organic frameworks used as separators have been reported.Therefore, our investigation to develop new supramolecular metal-based objects via a self-assembly process of molecular bricks will be presented. The work on cyclen derivatives allows to obtain metal complexes very stable able to pack in a well oriented dimension. Cyclen derivatives, in the presence of metal salts such as copper or zinc chlorides and polar solvents such as aliphatic alcohols, have a strong affinity for metals and spontaneously assemble in some conditions.5 In terms of applications, these self-assembled "organometallic" fibers represent an original and relatively easy to access substrate for fabricating 1D organic objects. Moreover, taking advantage of the properties and potentialities of these materials, we format an adequate shape to handle it as a potential separator for application in Energy Storage Systems (ESS).After a presentation of their synthesis and their formatting as potential separators for supercapacitors, preliminary electrochemical studies will be discussed. 1. J. Mater.Chem. A 2016, 4, 16812; ACS Energy let., 2022, 7, 885.2. ACS Appl. Energy Mater., 2021, 4, 128.3. ACS Appl. Matter. Interface, 2022, 14, 35645.4. J. Electoanalytical. Chem. 2023, 117251.5. Chem. Commun. 2010, 46, 1464. Figure 1

Disorder and demixing in bidisperse particle systems assembling bcc crystals.

Colloidal and nanoparticle self-assembly enables the creation of ordered structures with a variety of electronic and photonic functionalities. The outcomes of the self-assembly processes used to synthesize such structures, however, strongly depend on the uniformity of the individual nanoparticles. Here, we explore the simplest form of particle size dispersity-bidispersity-and its impact on the self-assembly process. We investigate the robustness of self-assembling bcc-type crystals via isotropic interaction potentials in binary systems with increasingly disparate particle sizes by determining their terminal size ratio-the most extreme size ratio at which a mixed binary bcc crystal forms. Our findings show that two-well pair potentials produce bcc crystals that are more robust with respect to particle size ratio than one-well pair potentials. This suggests that an improved self-assembly process is accomplished with a second attractive length scale encoded in the particle-particle interaction, which stabilizes the second-nearest neighbor shell. In addition, we document qualitative differences in the process of ordering and disordering: in bidisperse systems of particles interacting via one-well potentials, we observe a breakdown of order prior to demixing, while in systems interacting via two-well potentials, demixing occurs first and bcc continues to form in parts of the droplet down to low size ratios.

Supramolecular J- and H-Aggregation of Naphthalimide-Conjugated Dipeptide in Mixed-Solvent Systems and its Application in Cell Imaging.

In this work, a core-substituted NMI-conjugated dipeptide (4MNLV) was extensively studied in mixed solvent systems to explore the polarity effect on the self-assembly pattern and their photophysical property. 4MNLV adopted J- or H- type aggregation pattern depending upon the polarity index of the solvent system chosen. The self-assembly process was achieved through the anti-solvent effect. UV-vis study suggested that if the stock solution of 4MNLV was diluted with a relatively more polar solvent (compared to the stock solvent), then the system acquired J- type of aggregation pattern by showing a red-shift in their absorption maxima (λmax). Conversely, when the stock was diluted by a relatively less polar solvent, H-type of aggregation was observed, where blue shift of λmax was noticed. The emission spectra and the lifetime of the self-assembled materials were also influenced by the chosen solvent system. The chirotopic behaviour of these self-assembled materials was studied through CD spectroscopy. Morphological study indicated the formation of helical nanofibrillar structures. The bright green fluorescence of these highly biocompatible naphthalimide-peptide conjugate was used for cell imaging application, indicating its futuristic scope.

Structural Simplification of Podophyllotoxin: Discovery of γ-Butyrolactone Derivatives as Novel Antiviral Agents for Plant Protection.

Natural products are a valuable resource for the discovery of novel crop protection agents. A series of γ-butyrolactone derivatives, derived from the simplification of podophyllotoxin's structure, were synthesized and assessed for their efficacy against tobacco mosaic virus (TMV). Several derivatives exhibited notable antiviral properties, with compound 3g demonstrating the most potent in vivo anti-TMV activity. At 500 μg/mL, compound 3g achieved an inactivation effect of 87.8%, a protective effect of 71.7%, and a curative effect of 67.7%, surpassing the effectiveness of the commercial plant virucides ningnanmycin and ribavirin. Notably, the syn-diastereomer (syn-3g) exhibited superior antiviral activity compared to the anti-diastereomer (anti-3g). Mechanistic studies revealed that syn-3g could bind to the TMV coat protein and interfere with the self-assembly process of TMV particles. These findings indicate that compound 3g, with its simple chemical structure, could be a potential candidate for the development of novel antiviral agents for crop protection.

Ultra-Tough Graphene Oxide/DNA 2D Hydrogel with Intrinsic Sensing and Actuation Functions.

Hydrogel devices with mechanical toughness and tunable functionalities are highly desirable for practical long-term applications such as sensing and actuation elements for soft robotics. However, existing hydrogels have poor mechanical properties, slow rates of response, and low functionality. In this work, two-dimensional hydrogel actuators are proposed and formed on the self-assembly of graphene oxide (GO) and deoxynucleic acid (DNA). The self-assembly process is driven by the GO-induced transition of double stranded DNA (dsDNA) into single stranded DNA (ssDNA). Thus, the hydrogel's structural unit consists of two layers of GO covered by ssDNA and a layer of dsDNA in between. Such heterogeneous architectures stabilized by multiple hydrogen bondings have Young's modulus of up to 10GPa and rapid swelling rates of 4.0×10-3 to 1.1×10-2 s-1, which surpasses most types of conventional hydrogels. It is demonstrated that the GO/DNA hydrogel actuators leverage the unique properties of these two materials, making them excellent candidates for various applications requiring sensing and actuation functions, such as artificial skin, wearable electronics, bioelectronics, and drug delivery systems.

Redox-active polyoxovanadates as cofactors in the development of functional protein assemblies

The interactions of polyoxovanadates (POVs) with proteins have increasingly attracted interest in recent years due to their potential biomedical applications. This is especially the case because of their redox and catalytic properties, which make them interesting for developing artificial metalloenzymes. Organic-inorganic hybrid hexavanadates in particular offer several advantages over all-inorganic POVs. However, they have been scarcely investigated in biological systems even though, as shown in this work, hybrid hexavanadates are highly stable in aqueous solutions up to relatively high pH. Therefore, a novel bis-biotinylated hexavanadate was synthesized and shown to selectively interact with two biotin-binding proteins, avidin and streptavidin. Bridging interactions between multiple proteins led to their self-assembly into supramolecular bio-inorganic hybrid systems that have potential as artificial enzymes with the hexavanadate core as a redox-active cofactor. Moreover, the structure and charge of the hexavanadate core were determined to enhance the binding affinity and slightly alter the secondary structure of the proteins, which affected the size and speed of formation of the assemblies. Hence, tuning the polyoxometalate (POM) core of hybrid POMs (HPOMs) with protein-binding ligands has been demonstrated to be a potential strategy for controlling the self-assembly process while also enabling the formation of novel POM-based biomaterials that could be of interest in biomedicine.

Self-assembled Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O2-δ composite for solid oxide electrolysis cells

The anode is the key material that constrains the performance of solid oxide electrolysis cells (SOECs). Here, we have developed self-assembled Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O2-δ (SSC-SDC) composite by the co-synthesis strategy and studied its electrochemical performance as the anode for SOECs. The surface and interface properties of the self-assembled SSC-SDC composite were systematically studied. The SDC lattice expansion and the SSC lattice contraction of the SSC-SDC composite have been shown by XRD analysis, ascribed to the strong cation interdiffusion during the self-assembly process. The self-assembled SSC-SDC also exhibits superior oxygen evolution activity and displays a larger oxygen desorption peak than the physically mixed SSC&SDC. A higher proportion of adsorbed oxygen species on the surface of the self-assembled SSC-SDC than the physically mixed SSC&SDC also have been shown by XPS results. The cell with the self-assembled SSC-SDC as anode exhibits ca. 2.1 times higher current density than the physically mixed SSC&SDC as anode. Meanwhile, the polarization resistance of the cell with self-assembled SSC-SDC as the anode is 0.0957 Ω cm2, which is only 40 % of that observed in the cell where SSC and SDC are physically mixed as the anode. This novel self-assembly strategy shows great potential for preparing high-performance oxygen electrodes.

A multi-stimuli-responsive fluorescence material based on 1,8-naphthalimide.

A pair of 1,8-naphthalimides (NPIs) were designed and successfully synthesized through embellishing amino-containing NPI with 4-diethylaminosalicyladehyde and 4-diethylaminobenzaldehyde, respectively. Their structures were fully confirmed by 1H/13C NMR, HR-MS and FT-IR spectroscopic studies. Their photophysical properties were systematically investigated in different solvents of varied polarity, in THF/water mixtures with varying water fractions (fw), and in THF solvent with varying concentrations of NPIs. It inferred that the distinct differences in emission between two NPIs during self-assembled process could be ascribed that the hydroxyl-containing NPI allowed the excited-state intramolecular proton transfer process between -OH and CH=N units in the aggregation state. Interestingly, the solid of 4-diethylaminosalicyladehyde-functionalized NPI exhibited multi-stimuli-responsive fluorescence changes involving mechanofluorochromism and HCl/NH3 vapor stimulus-induced conversion. However, no remarkable change was observed in the photoluminescence (PL) spectra for the solid of 4-diethylaminobenzaldehyde-functionalized NPI under the stimuli of mechanical force and organic solvent.

A biomimetic branching signal-passing tile assembly model with dynamic growth and disassembly.

Natural biological branching processes can form tree-like structures at all scales and, moreover, can perform various functions to achieve specific goals; these include receiving stimuli, performing two-way communication along their branches, and dynamically reforming (extending or retracting branches). They underlie many biological systems with considerable diversity, frequency, and geometric complexity; these include networks of neurons, organ tissue, mycorrhizal fungal networks, plant growth, foraging networks, etc. This paper presents a biomimetic DNA tile assembly model (Y-STAM) to implement dynamic branching processes. The Y-STAM is a relatively compact mathematical model providing a design space where complex, biomimetic branch-like growth and behaviour can emerge from the appropriate parametrization of the model. We also introduce a class of augmented models (Y-STAM+) that provide time- and space-dependent modulations of tile glue strengths, which enable further diverse behaviours that are not possible in the Y-STAM; these additional behaviours include refinement of network assemblies, obstacle avoidance, and programmable growth patterns. We perform and discuss extensive simulations of the Y-STAM and the Y-STAM+. We envision that these models could be applied at the mesoscale and the molecular scale to dynamically assemble branching DNA nanostructures and offer insights into complex biological self-assembly processes.

Developing Supramolecular Metallogel Derived from Pd2L4 Cage Molecule for Delivering an Anti-Cancer Drug to Melanoma Cell B16-F10.

Supramolecular gels are an important class of materials that are promising for its wide range of applications including drug delivery. While supramolecular gels are intrinsically porous because of the 3D nano-matrix (gel matrix) that is being formed due to supramolecular self-assembly process involving the gelator molecules during gelation, additional nanopores can be introduced to the overall gel if the gelator molecule itself holds molecular cavity such as metal-organic-cage (MOC) molecules. A MOC having the molecular formula [(Pd2L24).4NO3].3H2O.2DMF.MeOH (Pd-cage) (L2=5-Azido-N,N'-di-pyridin-3-yl-isophthalamide) was successfully synthesized and characterized by FT-IR, 1H NMR, ESI-MS and single crystal X-ray diffraction. Stimuli-reversible supramolecular metallogel PdG could easily be formed from Pd-cage in DMSO/water mixture. The molecular cage of Pd-cage was demonstrated to be available for loading an anti-cancer drug namely doxorubicin (DOX). Subsequently, DOX was also loaded within PdG and delivered to melanoma cell line B16-F10 displaying significant anti-cancer activity as revealed by both MTT and scratch assay. Rheoreversibility of PdG and its ability to load and deliver DOX to cancer cells clearly raised hope for developing this metallogel further as topical anticancer gel.

Fluorescent Nanocable as a Biomedical Tool: Intracellular Self-Assembly Formed by a Natural Product Interconnects and Synchronizes Mitochondria.

Self-assembly processes commonly occur in various biological contexts to form functional biological structures. However, the self-assembly of nanofibers within cells by heterologous molecules showing a biological function is rare. In this work, we reported the intracellular formation of fluorescent nanofibers by a natural small molecule, lycobetaine (LBT), which facilitated the direct physical connection between mitochondria and synchronized their membrane potential oscillations. The luminescent properties of LBT enabled the real-time observation of nanofiber formation, while the semiconductive nature of the LBT nanofiber facilitated electrical signal transduction among the connected mitochondria. This study introduces an approach to modulate mitochondrial connectivity within cells using "nano-cables" which facilitate studies on synchronized mitochondrial operations and the underlying mechanisms of drug action.

A Schottky/Z-Scheme Hybrid for Augmented Photocatalytic H2 and H2O2 Production.

The prodigious employment of fossil fuels to conquer the global energy demand is becoming a dreadful threat to the human society. This predicament is appealing for a potent photocatalyst that can generate alternate energy sources via solar to chemical energy conversion. With this interest, we have fabricated a ternary heterostructure of Ti3C2 nanosheet modified g-C3N4/Bi2O3 (MCNRBO) Z-scheme photocatalyst through self-assembly process. The morphological analysis clearly evidenced the close interfacial interaction between g-C3N4 nanorod, Bi2O3 and Ti3C2 nanosheets. The oxygen vacancy created on Bi2O3 surface, as suggested by XPS and EPR analysis, supported the Z-scheme heterojunction formation between g-C3N4 nanorod and Bi2O3 nanosheets. The collaborative effect of Z-scheme and Schottky junction significantly reduced charge transfer resistance promoting separation efficiency of excitons as indicated from PL and EIS analysis. The potential of MCNRBO towards photocatalytic application was investigated by H2O2 and H2 evolution reaction. A superior photocatalytic H2O2 and H2 production rate for MCNRBO is observed, which are respectively around 5 and 18 folds higher as compared to pristine CNR nanorod. The present work encourages for the development of a noble, eco-benign and immensely efficient dual heterojunction based photocatalyst, which can acts as saviour of human society from energy crisis.

Poly(l-proline)-Stabilized Polypeptide Nanostructures via Ring-Opening Polymerization-Induced Self-Assembly (ROPISA).

Poly(proline) II helical motifs located at the protein-water interface stabilize the three-dimensional structures of natural proteins. Reported here is the first example of synthetic biomimetic poly(proline)-stabilized polypeptide nanostructures obtained by a straightforward ring-opening polymerization-induced self-assembly (ROPISA) process through consecutive N-carboxyanhydride (NCA) polymerization. It was found that the use of multifunctional 8-arm initiators is critical for the formation of nanoparticles. Worm-like micelles as well as spherical morphologies were obtained as confirmed by dynamic light scattering (DLS), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS). The loading of the nanostructures with dyes is demonstrated. This fast and open-vessel procedure gives access to amino acids-based nanomaterials with potential for applications in nanomedicine.

Concentration modulated microstructure and rheological properties of nanofibrous hydrogels derived from decellularized human amniotic membrane for 3D cell culture

Decellularized amnion (dAM)-derived hydrogels have been extensively exploited for versatile medical and therapeutical applications, particularly for soft tissue engineering of skin, vascular graft, and endometrium. In contrast to polyacrylamide-based hydrogels, which have been extensively employed as a 3D cell culture platform, the cell response of dAM hydrogel is yet to be understood. In this study, we have prepared hydrogels containing different concentrations of dAM and systematically investigated their microstructural features, gelation kinetics, and rheological properties. The results show that dAM hydrogels possess a network of fibers with an average diameter of 56 ± 5 nm at 1% dAM, which increases to 110 ± 14 nm at 3% dAM. The enhanced intermolecular crosslinking between the microfibrillar units increases the gelation rate in the growth phase of the self-assembly process. Moreover, increasing the concentration of dAM in the hydrogel formulation (from 1 to 3%w/v) enhances the dynamic mechanical moduli of the derived hydrogels by about two orders of magnitude (from 41.8 ± 2.5 to 896.2 ± 72.3 Pa). It is shown that the variation in the hydrogel stiffness significantly affects the morphology of dermal fibroblast cells cultured in the hydrogels. It is shown that the hydrogels containing up to 2%w/v dAM provide a suitable microenvironment for embedded fibroblast cells with spindle-like morphology. Nevertheless, at the higher concentration, an adverse effect on the proliferation and morphology of fibroblast cells is noticed due to stiffness-induced phenotype transformation of cells. Concentration-modulated properties of dAM hydrogels offer an in vitro platform to study cell-related responses, disease modeling, and drug studies.Graphical abstract

Dimerization and liquid-liquid phase separation of the nonrepetitive domains of pyriform spidroin 1 controls the pyriform silk formation

Spiders spin high performance silks with diverse mechanical properties for specific biological functions. Of these spider silk types, pyriform silk stands out as a unique combination of wet glue and dry fibers. Investigation of self-assembly process of spider silk proteins is necessary for elucidating the silk formation mechanism. However, the functions of nonrepetitive domains in the silk formation of pyriform spidroins from liquid proteins to solid fibers are still unclear, making it difficult to achieve efficient biomimetic preparations of pyriform silk with good mechanical properties. In this study, we investigate the roles of the N-linker repeat (NLR) and both terminal domains of pyriform spidroin 1 (PySp1) in the silk formation. We demonstrate for the first time that the PySp1 NLR alone is sufficient to self-assemble into high strength fibers. Moreover, we showed that the ability to promote the pyriform silk formation by the addition of the NLR. We also found that the pH-sensitive dimerization property for N-terminal domain and the liquid-liquid phase separation (LLPS) coupled with acidification triggers the self-assembly mediated by the C-terminal domain. Overall, our results provide new insight into the role of nonrepetitive domains in the pyriform silk formation mechanism and the basis for producing new protein-based materials derived from spider pyriform silk.