Highly Ordered Polypeptide with UCST Phase Separation Behavior

Liquid-liquid separation in gut immunity

Gut immunity is essential for maintaining intestinal health. Recent studies have identified that intracellular liquid-liquid phase separation (LLPS) may play a significant role in regulating gut immunity, however, the underlying mechanisms remain unclear. LLPS refers to droplet condensates formed through intracellular molecular interactions, which are crucial for the formation of membraneless organelles and biomolecules. LLPS can contribute to the formation of tight junctions between intestinal epithelial cells and influence the colonization of probiotics in the intestine, thereby protecting the intestinal immune system by maintaining the integrity of the intestinal barrier and the stability of the microbiota. Additionally, LLPS can affect the microclusters on the plasma membrane of T cells, resulting in increased density and reduced mobility, which in turn influences T cell functionality. The occurrence of intracellular LLPS is intricately associated with the initiation and progression of gut immunity. This review introduces the mechanism of LLPS in gut immunity and analyzes future research directions and potential applications of this phenomenon.

Understanding Polyproline's Unusual Thermoresponsive Properties Using a Polyproline-Based Double Hydrophilic Block Copolymer

Polyproline is a unique thermoresponsive polymer characterized by large thermal and conformational hysteresis. This article employs polyproline-based double hydrophilic block copolymers (PNIPAMn-b-PLPm) to gain insight into polyproline's thermoresponsive mechanism. The amine-terminated poly(N-isopropylacrylamide) (NH2-PNIPAMm) was used as the macroinitiator for ring-opening polymerization of proline-NCA monomers, resulting in various block copolymers (PNIPAMn-b-PLPm) with varying PLP block lengths. Block copolymers' thermal phase transitions were compared with their homopolymer counterparts using turbidimetry, variable-temperature NMR, dynamic light scattering, and circular dichroism spectroscopy. These experiments revealed that regardless of their compositions, all block copolymers exhibited a two-stage collapse (TCP(PLP) > TCP(PNIPAM)) during the heating cycle. In contrast, only one clearing temperature (TCL) was observed during cooling. The observed clearing temperature is closely correlated to the clearing temperature of PNIPAM blocks, suggesting the role of water-soluble PNIPAM blocks in resolving the PLP blocks. Moreover, thermal and conformational hysteresis related to the polyproline block is significantly suppressed in the presence of a PNIPAM block. Linking PNIPAM blocks has two significant effects on PLP segments' thermoresponsive behavior. For example, during the heating cycle, the precollapsed PNIPAM chains (as TCP(PNIPAM) < TCP(PLP)) prevent orderly aggregation within the PLP block. Meanwhile, during the cooling cycle below the clearing temperature of the PNIPAM block, the PNIPAM chains impart water solubility (as TCL(PNIPAM) > TCL(PLP)) to the collapsed PLP chains. Overall, the PNIPAM block imparts water solubility and perturbs PLP chains to form the native aggregate structure, suppressing the hysteresis effect. Accordingly, the large thermal and conformational hysteresis associated with native PLP chains appears to result from a noninterfering aggregation above the critical temperature.

The role of liquid-liquid phase separation in the disease pathogenesis and drug development

Misfolding and aggregation of specific proteins are associated with liquid-liquid phase separation (LLPS), and these protein aggregates can interfere with normal cellular functions and even lead to cell death, possibly affecting gene expression regulation and cell proliferation. Therefore, understanding the role of LLPS in disease may help to identify new mechanisms or therapeutic targets and provide new strategies for disease treatment. There are several ways to disrupt LLPS, including screening small molecules or small molecule drugs to target the upstream signaling pathways that regulate the LLPS process, selectively dissolve and destroy RNA droplets or protein aggregates, regulate the conformation of mutant protein, activate the protein degradation pathway to remove harmful protein aggregates. Furthermore, harnessing the mechanism of LLPS can improve drug development, including preparing different kinds of drug delivery carriers (microneedles, nanodrugs, imprints), regulating drug internalization and penetration behaviors, screening more drugs to overcome drug resistance and enhance receptor signaling. This review initially explores the correlation between aberrant LLPS and disease, highlighting the pivotal role of LLPS in preparing drug development. Ultimately, a comprehensive investigation into drug-mediated regulation of LLPS processes holds significant scientific promise for disease management.

NIR-triggered and Thermoresponsive Core-shell nanoparticles for synergistic anticancer therapy

Recent advancements in cancer treatment have underscored the inadequacy of conventional monotherapies in addressing complex malignant tumors. Consequently, there is a growing interest in synergistic therapies capable of overcoming the limitations of monotherapies, leading to more personalized and effective approaches. Among these, the combination of photothermal therapy (PTT) and chemotherapy has emerged as a promising avenue for tumor management. In this study, we present a novel approach utilizing thermoresponsive mesoporous silica nanoparticles (MSN) as a delivery system for the chemotherapeutic drug doxorubicin. By incorporating photothermal agent copper sulfide (CuS) nanoparticles into the MSN, the resulting composite material exhibits potent photothermal properties. Furthermore, the integration of an upper critical solution temperature (UCST) polymer within the silica outer layer serves as a "gatekeeper", enabling precise control over drug release kinetics. This innovative nanomaterial effectively merges thermoresponsive behavior with PTT, thereby minimizing the collateral damage associated with traditional chemotherapy on healthy tissues. Moreover, in both in vitro studies using mouse breast carcinoma cells (4 T1) and in vivo experiments utilizing a 4 T1 tumor-bearing mouse model, our nanomaterials demonstrated synergistic effects, enhancing the anti-tumor efficacy of combined PTT and chemotherapy. With its remarkable photothermal conversion efficiency, robust stability, and biocompatibility, the UCST-responsive nanoplatform holds immense potential for clinical applications.

Genetically Fused Resilin-like Polypeptide-Coiled Coil Bundlemer Conjugates Exhibit Tunable Multistimuli-Responsiveness and Undergo Nanofibrillar Assembly

Peptide-based materials are diverse candidates for self-assembly into modularly designed and stimuli-responsive nanostructures with precisely tunable compositions. Here, we genetically fused computationally designed coiled coil-forming peptides to the N- and C-termini of compositionally distinct multistimuli-responsive resilin-like polypeptides (RLPs) of various lengths. The successful expression of these hybrid polypeptides in bacterial hosts was confirmed through techniques such as gel electrophoresis, mass spectrometry, and amino acid analysis. Circular dichroism spectroscopy and ultraviolet-visible turbidimetry demonstrated that despite the fusion of disparate structural and responsive units, the coiled coils remained stable in the hybrid polypeptides, and the sequence-encoded differences in thermoresponsive phase separation of the RLPs were preserved. Cryogenic transmission electron microscopy and coarse-grained modeling showed that after thermal annealing in solution, the hybrid polypeptides adopted a closed loop conformation and assembled into nanofibrils capable of further hierarchically organizing into cluster structures and ribbon-like structures mediated by the self-association tendency of the RLPs.

Spontaneous Liquid Droplet-to-Gel Transition of Citrulline Polypeptide Complexed with Nucleic Acids

Inside cells, proteins complex with nucleic acids to form liquid droplets resulting from liquid-liquid phase separation. The presence of mutated proteins can change the state of these liquid droplets to solids or gels, triggering neurodegenerative diseases. The mechanism of the liquid to solid or gel transition is still unclear. Solutions of poly(l-ornithine-co-l-citrulline) (PLOC) copolymers, which exhibit upper critical solution temperature-type behavior, change state upon cooling. In this study, we evaluated the effect of nucleic acids complexed with PLOC on phase changes. In the presence of nucleic acids, such as polyC and polyU, PLOC formed liquid droplets at low temperatures. The droplets dissolved at temperatures above the phase separation temperature. The phase separation temperature depended on the chemical structure of the nucleobase, implying that electrostatic and hydrogen bonding interactions between the nucleic acid and PLOC influenced phase separation. Furthermore, the liquid droplets spontaneously changed to gel-like precipitates due to spontaneous release of nucleic acids from the complex. The rate of the liquid droplet-to-gel transition depended on the magnitude of electrostatic and hydrogen bonding interactions between PLOC and nucleic acid. PLOC complexed with mRNA also underwent a liquid droplet-to-gel transition upon the release of mRNA. This work provides insights into the mechanism of pathogenic transitions of the cellular droplets.

Synergistic Approaches in the Design and Applications of UCST Polymers

This review summarizes recent progress in the synergistic design strategy for thermoresponsive polymers possessing an upper critical solution temperature (UCST) in aqueous systems. To achieve precise control of the responsive behavior of the UCST polymers, their molecular design can benefit from a synergistic effect of hydrogen bonding with other interactions or modification of the chemical structures. The combination of UCST behavior with other stimuli-responsive properties of the polymers may yield new functional materials with potential applications such as sensors, actuators, and controlled release devices. The advances in this area provide insight or inspiration into the understanding and design of functional UCST polymers for a wide range of applications.

Visualizing Formation and Dynamics of a Three-Dimensional Sponge-like Network of a Coacervate in Real Time

Coacervates, which are formed by liquid-liquid phase separation, have been extensively explored as models for synthetic cells and membraneless organelles, so their in-depth structural analysis is crucial. However, both the inner structure dynamics and formation mechanism of coacervates remain elusive. Herein, we demonstrate real-time confocal observation of a three-dimensional sponge-like network in a dipeptide-based coacervate. In situ generation of the dipeptide allowed us to capture the emergence of the sponge-like network via unprecedented membrane folding of vesicle-shaped intermediates. We also visualized dynamic fluctuation of the network, including reversible engagement/disengagement of cross-links and a stochastic network kissing event. Photoinduced transient formation of a multiphase coacervate was achieved with a thermally responsive phase transition. Our findings expand the fundamental understanding of synthetic coacervates and provide opportunities to manipulate their physicochemical properties by engineering the inner network for potential applications in development of artificial cells and life-like material fabrication.

Peptide-based coacervates in therapeutic applications

Coacervates are droplets formed by liquid‒liquid phase separation. An increasing number of studies have reported that coacervates play an important role in living cells, such as in the generation of membraneless organelles, and peptides contribute to condensate droplet formation. Peptides with versatile functional groups and special secondary structures, including α-helices, β-sheets and intrinsically disordered regions, provide novel insights into coacervation, such as biomimetic protocells, neurodegenerative diseases, modulations of signal transmission, and drug delivery systems. In this review, we introduce different types of peptide-based coacervates and the principles of their interactions. Additionally, we summarize the thermodynamic and kinetic mechanisms of peptide-based coacervates and the associated factors, including salt, pH, and temperature, affecting the phase separation process. We illustrate recent studies on modulating the functions of peptide-based coacervates applied in biological diseases. Finally, we propose their promising broad applications and describe the challenges of peptide-based coacervates in the future.

An Overview of Coacervates: The Special Disperse State of Amphiphilic and Polymeric Materials in Solution

Individual amphiphiles, polymers, and colloidal dispersions influenced by temperature, pH, and environmental conditions or interactions between their oppositely charged pairs in solvent medium often produce solvent-rich and solvent-poor phases in the system. The solvent-poor denser phase found either on the top or the bottom of the system is called coacervate. Coacervates have immense applications in various technological fields. This review comprises a concise introduction, focusing on the types of coacervates, and the influence of different factors in their formation, structures, and stability. In addition, their physicochemical properties, thermodynamics of formation, and uses and multifarious applications are also concisely presented and discussed.

Molecular bases for temperature sensitivity in supramolecular assemblies and their applications as thermoresponsive soft materials

Thermoresponsive supramolecular assemblies have been extensively explored in diverse formats, from injectable hydrogels to nanoscale carriers, for a variety of applications including drug delivery, tissue engineering and thermo-controlled catalysis. Understanding the molecular bases behind thermal sensitivity of materials is fundamentally important for the rational design of assemblies with optimal combination of properties and predictable tunability for specific applications. In this review, we summarize the recent advances in this area with a specific focus on the parameters and factors that influence thermoresponsive properties of soft materials. We summarize and analyze the effects of structures and architectures of molecules, hydrophilic and lipophilic balance, concentration, components and external additives upon the thermoresponsiveness of the corresponding molecular assemblies.

Rapid Determination of Phase Diagrams for Biomolecular Liquid-Liquid Phase Separation with Microfluidics

Biomolecular phase separation is currently emerging in both the medical and life science fields. Meanwhile, the application of liquid-liquid phase separation has been extended to many fields including drug discovery, fibrous material fabrication, 3D printing, and polymer design. Although more than 8600 proteins and other synthetic macromolecules are capable of phase separation as recently reported, there is still a lack of a high-throughput approach to quantitatively characterize its phase behaviors. To meet this requirement, here, we proposed fast and high-resolution acquisition of biomolecular phase diagrams using microfluidic chips. Using this platform, we demonstrated the phase behavior of polyU/RRASLRRASLRRASL in a quantitative manner. Up to 1750 concentration conditions can be generated in 140 min. The detection limitation of our device to capture the saturation concentration for phase separation is about 5 times lower than that of the traditional turbidity method. Thus, our results provide a basis for the rapid acquisition of phase diagrams with high-throughput and pave the way for its wide application.

Nonionic Polymer with Flat Upper Critical Solution Temperature Behavior in Water

We rationally designed a monomer that when polymerized formed a well-defined nonionic polymer [poly(2-(methacryloyloxy) ethylureido glycinamide), PMEGA] by reversible addition fragmentation chain transfer with a flat and tunable upper critical solution temperature (UCST) in water. The monomer was made in one pot from commercially available compounds and with ease of purification. Strong hydrogen-bonding side groups on the polymer produced sharp coil-to-globule transitions upon cooling below its UCST. Ideal random copolymers produced with butyl methacrylate also showed flat UCST profiles, in which the UCST increased with a greater butyl methacrylate copolymer composition from 7 to 65 °C. In the presence of NaCl, the UCST decreased linearly with NaCl concentration due to the "salting-in" effect, and it was found that the slopes from the linear decrease of UCST were nearly identical for all copolymer compositions. This new polymer and its copolymers support the hypothesis that strong hydrogen bonding between the side groups allowed the flat UCST to be readily tuned with a high level of predictability. We postulate that this polymer system may provide wide biological applicability similar to that found for the well-used flat lower critical solution temperature (LCST) of poly(N-isopropylacrylamide).

Remarkable diastereomeric effect on thermoresponsive behavior of polyurethane based on lysine and tartrate ester derivatives

This study describes the long-distance diastereomeric effect on thermoresponsive properties in water-soluble diastereomeric polyurethanes (PUs) composed of an l-lysine ethyl ester diisocyanate and a trimethylene glycol l-/d-tartrate ester, which have differences in spatial arrangements of the ethyl esters in the mirror image. The PUs based on l-lysine and l-/d-tartrate ester, named l-PU and d-PU, were synthesized with various number average molecular weights from 4700 to 13 100. In turbidimetry, l-PU showed a steep phase transition from 100%T to 0%T within about 10 °C at 4 g L⁻¹, whereas d-PU did not change completely to 0%T transmittance even at 80 °C at 4 g L⁻¹. In addition, the thermoresponsive properties of l-PU were less affected by concentration than those of d-PU. This long-distance diastereomeric effect on thermoresponsive behavior between l-PU and d-PU appeared in common among 6 samples with 4700 to 13 100 number average molecular weight. In the dynamic light scattering experiments at each transmittance, the hydrodynamic diameter (D_h) of l-PU increased up to 1000 nm, while the D_h of d-PU remained almost at 200–300 nm. The C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O stretching vibration of FT-IR spectra showed that d-PU has more hydrogen-bonded ester groups than L-PU. Thus, we speculated that the difference in the retention of polymer chains in the micelle to promote intermicellar bridging generates the long-distance diastereomeric effect.

The long-distance diastereomeric effect on thermoresponsive properties in a polyurethane system consisting of chiral monomers was reported.

Upper Critical Solution Temperature-Type Responsive Cyclodextrins with Characteristic Inclusion Abilities

Water-soluble and thermoresponsive macrocycles with stable inclusion toward guests are highly valuable to construct stimuli-responsive supramolecular materials for versatile applications. Here, we develop such macrocycles - ureido-substituted cyclodextrins (CDs) which exhibit unprecedented upper critical solution temperature (UCST) behavior in aqueous media. These novel CD derivatives showed good solubility in water at elevated temperature, but collapsed from water to form large coacervates upon cooling to low temperature. Their cloud points are greatly dependent on concentration and can be mediated through oxidation and chelation with silver ions. Significantly, the amphiphilicity of these CD derivatives is supportive to host-guest binding, which affords them inclusion abilities to guest dyes. The inclusion complexation remained nearly intact during thermally induced phase transitions, which is in contrast to the switchable inclusion behavior of lower critical solution temperature (LCST)-type CDs. Moreover, ureido-substituted CDs were exploited to co-encapsulate a pair of guest dyes whose fluorescence resonance energy transfer process can be switched by the UCST phase transition. We therefore believe these novel thermoresponsive CDs may form a new strategy for developing smart macrocycles and allow for exploring smart supramolecular materials.

Simulations of the Upper Critical Solution Temperature Behavior of Poly(ornithine-co-citrulline)s Using MARTINI-Based Coarse-Grained Force Fields

Poly(ornithine-co-citrulline)s are ureido-based polymers, which were shown to exhibit tunable upper critical solution temperature (UCST) behavior, a property that can be exploited to develop thermoresponsive nanoparticles for controlled drug delivery systems. To gain insight into the driving forces that govern the formation and dissolution processes of poly(ornithine-co-citrulline) nanoparticles, a molecular dynamics (MD) simulation study has been carried out using MARTINI-based protein coarse-grained models. Multi-microsecond simulations at temperatures ranging from 280 to 370 K show that the fully reparametrized version 3.0 of MARTINI force field is able to capture the dependence on temperature of poly(ornithine-co-citrulline) aggregation and dissolution, while version 2.2 could not account for it. Furthermore, the phase separation observed in these simulations allowed us to extrapolate a phase diagram based on the Flory-Huggins theory of polymer solution, which could help in future rational design of drug delivery nanoparticles based on poly(amino acid)s.

On-Demand Regulation of Dual Thermosensitive Protein Hydrogels

Despite considerable progress having been made in thermosensitive protein hydrogels, regulating their thermal transitions remains a challenge due to the intricate molecular structures and interactions of the underlying protein polymers. Here we report a genetic fusion strategy to tune the unique dual thermal transitions of the C-terminal domain (CTD) of spider major ampullate spidroin 1, and explore the regulation mechanism by biophysical characterization and molecular dynamics simulations. We found that the fusion of elastin-like polypeptides (ELPs) tuned the dual transition temperatures of CTD to a physiologically relevant window, by introducing extra hydrogen bonding at low temperatures and hydrophobic interactions at high temperatures. The resulting hydrogels constructed from the fusion proteins were demonstrated to be a promising vehicle for cell preservation and delivery. This study provides insights on the regulation of the dual thermosensitive protein hydrogels and suggests a potential application of the hydrogels for consolidated cell storage and delivery.

Biological applications of water-soluble polypeptides with ordered secondary structures

Water-soluble polypeptides are a class of synthetic polymers with peptide bond frameworks imitating natural proteins and have broad prospects in biological applications. The regulation and dynamic transition of the secondary structures of water-soluble polypeptides have a great impact on their physio-chemical properties and biological functions. In this review article, we briefly introduce the current strategies to synthesize polypeptides and modulate their secondary structures. We then discuss the factors affecting the conformational stability/transition of polypeptides and the potential impact of side-chain functionalization on the ordered secondary structures, such as α-helix and β-sheet. We then summarize the biological applications of water-soluble polypeptides such as cell penetration, gene delivery, and antimicrobial treatment, highlighting the important roles of ordered secondary structures therein.

Design of an LCST-UCST-Like Thermoresponsive Zwitterionic Copolymer

Thermoresponsive polymers that possess both UCST- and LCST-like behaviors have generally been designed using diblock copolymers that are mostly composed of an LCST-like polymer and a UCST polymer. Herein, we prepared an LCST-UCST-type polymer composed of UCST-like thermoresponsive zwitterionic sulfabetaine methacrylate and nonthermoresponsive PEG methacrylate, ZB-PEG, by reversible addition-fragmentation chain transfer (RAFT) copolymerization. By adjusting the PEG composition, ZB-PEG formed a mesoglobule, a microglobule, and the dissociated states in phosphate-buffered saline (PBS). These states were found to be reversible via temperature control. Moreover, this behavior showed high reversibility and succeeded in stabilizing horseradish peroxidase (HRP) in the dilute condition. Such thermoresponsive ZB-PEG can be applied over a wide range of applications in biotechnology and other fields.

Anion-induced thermoresponsiveness in cationic polycysteine and DNA binding

This study describes the synthesis of an l-cysteine-based water-soluble cationic polypeptide, an investigation of its thermoresponsive behaviour in the presence of added anions and its polyplexation with DNA.

Bundling Process of Citrulline Polypeptides upon UCST-Type Phase Separation

Ureido-modified poly(l-citrulline) (l-ornithine-co-l-citrulline denoted by PlOC) shows UCST-type phase separation behavior even under physiologically relevant conditions, which forms an α-helix structure above its phase separation temperature (T_p) but transforms into a solid-like aggregation composed of regular hexagonal packed cylinders below the T_p. This morphological transformation is characteristic of the phase separation behavior, but the mechanism behind it has remained incompletely understood. Here, we studied the phase separation behavior using small-angle X-ray scattering (SAXS) measurements. To analyze the SAXS data, we employed the modified unified model proposed previously, which decomposes the scattering profile into each structural element, such as the α-helices and their aggregation formed via hydrogen-bonding interactions between the ureido groups. The aggregation level is dependent on the temperature (T) and grouped into three classes: (1) mass-fractal aggregation composed of the α-helix (T > T_p), (2) spherical aggregation composed of the hexagonal packed cylinder (T < T_p), and (3) micro-order agglomeration formed by mutual fusion of the spherical aggregation, which appears as a solid-like aggregation. The SAXS analysis suggested that the transformation from the dispersed state as the α-helix to the agglomeration containing hierarchical structures occurs in a stepwise manner when the temperature falls below the T_p, which might also be transition behavior similar to the process of protein folding through folding intermediates.

Molecular Picture of the Transient Nature of Lipid Rafts

In biological membranes, lipid rafts are now thought to be transient and nanoscopic. However, the mechanism responsible for these nanoscopic assemblies remains poorly understood, even in the case of model membranes. As a result, it has proven extremely challenging to probe the physicochemical properties of lipid rafts at the molecular level. Here, we use all-atom molecular dynamics (MD) simulations and inelastic X-ray scattering (IXS), an intrinsically nanoscale technique, to directly probe the energy transfer and collective short-wavelength dynamics (phonons) of biologically relevant model membranes. We show that the nanoscale propagation of stress in lipid rafts takes place in the form of collective motions made up of longitudinal (compression waves) and transverse (shear waves) molecular vibrations. Importantly, we provide a molecular picture for the so-called van der Waals mediated "force from lipid" [Anishkin, A. et al. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 7898], a key parameter for the ionic channel mechano-transduction and the mechanism for the lipid transfer of molecular level stress [Aponte-Santamarı́a, C. et al. J. Am. Chem. Soc. 2017, 139, 13588]. Specifically, we describe how lipid rafts are formed and maintained through the propagation of molecular stress, lipid raft rattling dynamics, and a relaxation process. Eventually, the rafts dissipate through the self-diffusion of lipids making up the rafts. We also show that the molecular stress and viscoelastic properties of transient lipid rafts can be modulated through the use of hydrophobic biomolecules such as melatonin and tryptophan. Ultimately, the herein proposed mechanism describing the molecular interactions for the formation and dissolution of lipid rafts may offer insights as to how lipid rafts enable biological function.

Thermoresponsive properties of poly(acrylamide-co-acrylonitrile)-based diblock copolymers synthesized (by PISA) in water

UCST-type poly(acrylamide-co-acrylonitrile) diblock copolymers synthesized in water (by PISA) can not only undergo reversible temperature-induced chain dissociation, but also temperature-induced morphological transition.

Intrinsically disordered proteins access a range of hysteretic phase separation behaviors

The phase separation behavior of intrinsically disordered proteins (IDPs) is thought of as analogous to that of polymers that undergo equilibrium lower or upper critical solution temperature (LCST and UCST, respectively) phase transition. This view, however, ignores possible nonequilibrium properties of protein assemblies. Here, by studying IDP polymers (IDPPs) composed of repeat motifs that encode LCST or UCST phase behavior, we discovered that IDPs can access a wide spectrum of nonequilibrium, hysteretic phase behaviors. Experimentally and through simulations, we show that hysteresis in IDPPs is tunable and that it emerges through increasingly stable interchain interactions in the insoluble phase. To explore the utility of hysteretic IDPPs, we engineer self-assembling nanostructures with tunable stability. These findings shine light on the rich phase separation behavior of IDPs and illustrate hysteresis as a design parameter to program nonequilibrium phase behavior in self-assembling materials.

Preparation and applications of peptide-based injectable hydrogels

In situ injectable hydrogels have shown tremendous potential application in the biomedical field due to their significant drug accumulation at lesion sites, sustained release and markedly reduced systemic side effects. Specifically, peptide-based hydrogels, with unique biodegradation, biocompatibility, and bioactivity, are attractive molecular skeletons. In addition, peptides play a prominent role in normal metabolism, mimicking the natural tissue microenvironment and responding to stimuli in the lesion environment. Their advantages endow peptide-based hydrogels with great potential for application as biomedical materials. In this review, the fabrication and production of peptide-based hydrogels are presented. Several promising candidates, which are smart and environment-sensitive, are briefly reviewed. Then, the recent developments of these hydrogels for biomedical applications in tissue engineering, as drug/gene vehicles, and anti-bacterial agents are discussed. Finally, the development of peptide-based injectable hydrogels for biomedical applications in the future is surveyed.

Synthesis and UCST-type thermoresponsive properties of polypeptide based single-chain nanoparticles

We present the synthesis and UCST-type thermoresponsive properties of helical polypeptide based single-chain nanoparticles which displayed increased solution phase transition temperature and improved biocompatibility.