Sol-gel Phase Transition Research Articles

RNA G-quadruplexes and calcium ions synergistically induce Tau phase transition in vitro

Tau aggregation is a defining feature of neurodegenerative tauopathies, including Alzheimer’s disease, corticobasal degeneration, and frontotemporal dementia. This aggregation involves the liquid–liquid phase separation (LLPS) of Tau, followed by its sol–gel phase transition, representing a crucial step in aggregate formation both in vitro and in vivo. However, the precise cofactors influencing Tau phase transition and aggregation under physiological conditions (e.g., ion concentration and temperature) remain unclear. In this study, we unveil that nucleic acid secondary structures, specifically RNA G-quadruplexes (rG4s), and calcium ions (Ca2+) synergistically facilitated the sol–gel phase transition of human Tau under mimic intracellular ion conditions (140 mM KCl, 15 mM NaCl, and 10 mM MgCl2) at 37°C in vitro. In the presence of molecular crowding reagents, Tau formed stable liquid droplets through LLPS, maintaining fluidity for 24 h under physiological conditions. Notably, cell-derived RNA promoted Tau sol–gel phase transition, with rG4s emerging as a crucial factor. Surprisingly, polyanion heparin did not elicit a similar response, indicating a distinct mechanism not rooted in electrostatic interactions. Further exploration underscored the significance of Ca2+, which accumulate intracellularly during neurodegeneration, as additional cofactors in promoting Tau phase transition after 24 h. Importantly, our findings demonstrate that rG4s and Ca2+ synergistically enhance Tau phase transition within 1 h when introduced to Tau droplets. Moreover, rG4-Tau aggregates showed seeding ability in cells. In conclusion, our study illuminates the pivotal roles of rG4s and Ca2+ in promoting Tau aggregation under physiological conditions in vitro, offering insights into potential triggers for tauopathy.

Physically crosslinked chitosan/αβ–glycerophosphate hydrogels enhanced by surface-modified cyclodextrin: An efficient strategy for controlled drug release

This study reports physically crosslinked chitosan/αβ–glycerophosphate (CS/GP) hydrogels containing surface-modified cyclodextrin for efficient controlled drug release. Highly water-soluble β–cyclodextrin-grafted L–serine (CD–g–Ser) compounds were synthesized, and employed as an effective carrier of berberine hydrochloride (Ber) for CS/GP hydrogels. Various characterizations, including gelation time determination, scanning electron microscopy, and viscosity measurement, indicated that the introduction of CD–g–Ser led to increased crosslinking degree, improved temperature sensitivity, and shortened sol–gel phase transition time of the hydrogel. Meanwhile, the sustained release ability for Ber was achieved due to the hydrophobic association between cyclodextrin and Ber. It was observed that within 4 h, the hydrogel containing CD–g–Ser released 40 % of Ber, while the CS/GP hydrogel without CD–g–Ser released 65 % of Ber. Furthermore, in vitro bacteriostasis experiments confirmed the drug-loaded hydrogel had an excellent antibacterial effect against E. coli and S. aureus (diameter of the inhibition zone up to (16.4 and 34.7) mm, respectively), low hemolysis rate (<2 %), and high cell viability (>90 %). The findings indicate that the physical crosslinked CS hydrogel can be used as a new drug delivery system, and its excellent antibacterial effect makes it a potential wound dressing candidate.

RNA G-quadruplexes form scaffolds that promote neuropathological α-synuclein aggregation.

Synucleinopathies, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are triggered by α-synuclein aggregation, triggering progressive neurodegeneration. However, the intracellular α-synuclein aggregation mechanism remains unclear. Herein, we demonstrate that RNA G-quadruplex assembly forms scaffolds for α-synuclein aggregation, contributing to neurodegeneration. Purified α-synuclein binds RNA G-quadruplexes directly through the N terminus. RNA G-quadruplexes undergo Ca2+-induced phase separation and assembly, accelerating α-synuclein sol-gel phase transition. In α-synuclein preformed fibril-treated neurons, RNA G-quadruplex assembly comprising synaptic mRNAs co-aggregates with α-synuclein upon excess cytoplasmic Ca2+ influx, eliciting synaptic dysfunction. Forced RNA G-quadruplex assembly using an optogenetic approach evokes α-synuclein aggregation, causing neuronal dysfunction and neurodegeneration. The administration of 5-aminolevulinic acid, a protoporphyrin IX prodrug, prevents RNA G-quadruplex phase separation, thereby attenuating α-synuclein aggregation, neurodegeneration, and progressive motor deficits in α-synuclein preformed fibril-injected synucleinopathic mice. Therefore, Ca2+ influx-induced RNA G-quadruplex assembly accelerates α-synuclein phase transition and aggregation, potentially contributing to synucleinopathies.

Synthesis and rheological analyzes of temperature and light sensitive gels comprising amphiphilic azobenzene polymers, chitosan and pluronic F127

AbstractThis study investigates the reinforcement of pluronic (PF127) based temperature responsive hydrogels with photosensitive functionalities to create smart and injectable materials. For this purpose, 4‐[4‐[(4‐phenyl)azo]phenoxy] methacrylate (PAzPMA) was synthesized and further polymerized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The structures of the copolymers were characterized by several techniques such as Fourier‐transform infrared (FT‐IR), nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The azobenzene‐functionalized copolymer was combined with P127 solid polymer in micelle form and with P127 micelles in solid form to obtain PF127‐AzoMx and PF127‐AzoPx gels, respectively. When the temperature profiles of the PF127‐AzoMx and PF127‐AzoPx systems were compared with PF127, sol–gel phase transition were shifted to lower temperatures due to stronger hydrophobic interactions. Additionally, different concentrations of N,N,N‐trimethyl chitosan (f‐chitosan) were added to the gel systems and their rheological properties were investigated by exposing them to UV light. It has been observed that the presence and concentration of f‐chitosan are important for the variation of the interactions' strength between the micelles. The study highlights the potential of multifunctional hydrogels for specific biomedical applications that combine sensitivity to both thermal and optical stimuli for controlled drug delivery and tissue engineering purposes.

Biocompatible and nondegradable microcapsules using an ethylamine-bridged EGCG dimer for successful therapeutic cell transplantation

Conventional alginate microcapsules are widely used for encapsulating therapeutic cells to reduce the host immune response. However, the exchange of monovalent cations with divalent cations for crosslinking can lead to a sol-gel phase transition, resulting in gradual degradation and swelling of the microcapsules in the body. To address this limitation, we present a biocompatible and nondegradable epigallocatechin-3-gallate (EGCG)-based microencapsulation with ethylamine-bridged EGCG dimers (EGCG(d)), denoted as ‘Epi-Capsules’. These Epi-Capsules showed increased physical properties and Ca2+ chelating resistance compared to conventional alginate microcapsules. Horseradish peroxidase (HRP) treatment is very effective in increasing the stability of Epi-Capsule((+)HRP) due to the crosslinking between EGCG(d) molecules. Interestingly, the Epi-Capsules(oxi) using a pre-oxidized EGCG(d) can support long-term survival (>90 days) of xenotransplanted insulin-secreting islets in diabetic mice in vivo, which is attributed to its structural stability and reactive oxygen species (ROS) scavenging for lower fibrotic activity. Collectively, this EGCG-based microencapsulation can create Ca2+ chelating-resistance and anti-oxidant activity, which could be a promising strategy for cell therapies for diabetes and other diseases.

Polyurea-urethane Temperature-responsive Hydrogels for Sustained Delivery of Anti-VEGF Therapeutics.

Temperature-responsive hydrogels, or thermogels, have emerged as a leading platform for sustained delivery of both small molecule drugs and macromolecular biologic therapeutics. Although thermogel properties can be modulated by varying the polymer's hydrophilic-hydrophobic balance, molecular weight and degree of branching, varying the supramolecular donor-acceptor interactions on the polymer remains surprisingly overlooked. Herein, to study the influence of enhanced hydrogen bonding on thermogelation, we synthesized a family of amphiphilic polymers containing urea and urethane linkages using quinuclidine as an organocatalyst. Our findings showed that the presence of strongly hydrogen bonding urea linkages significantly enhanced polymer hydration in water, in turn affecting hierarchical polymer self-assembly and macroscopic gel properties such as sol-gel phase transition temperature and gel stiffness. Additionally, analysis of the sustained release profiles of Aflibercept, an FDA-approved protein biologic for anti-angiogenic treatment, showed that urea bonds on the thermogel were able to significantly alter the drug release mechanism and kinetics compared to usage of polyurethane gels of similar composition and molecular weight. Our findings demonstrate the unrealized possibility of modulating gel properties and outcomes of sustained drug delivery through judicious variation of hydrogen bonding motifs on the polymer structure.

Radiofrequency induced UCST-type gel-sol transition of metformin-conjugated nanogels for precisely synergizing thermal ablation and blood-vessel embolization

Transcatheter arterial chemoembolization (TACE) exhibits an important role in the treatment of some solid tumors. However, incomplete embolization and angiogenesis-induced tumor relapse and metastasis remain the biggest challenges for TACE. Here, we synthesized metformin-conjugated poly(N-acryloyl glycinamide) (pMet) nanogels for precisely synergizing TACE with radiofrequency ablation (RFA) to improve antitumor efficacy. pMet nanogels exhibited RF-heating effect and UCST-type gel-sol phase transition, with high performance of sol syringeability, gel strength and thermal stability. Meanwhile, pMet nanogels showed distinct cytotoxicity and suppression of CD24. By the synergistic efficacy with RF-heating, pMet nanogels exhibited significant tumor regression (0.37 ± 0.5) over 36 d in H22-bearing mice. pMet nanogels further down-regulated the levels of PD-1 and Tim-3 of CD8+ T cells and CD25 and CD38 of CD4+ T cells, suggesting their improvement on tumor immunosuppressive microenvironment. The blood-vessel embolization of pMet nanogels was well validated on rabbit ear vessel model. pMet nanogels provide a new paradigm for constructing RF responsive embolic platform.

Thermosensitive injectable polysaccharide-based hydrogels: Gelation mechanisms, synthetic strategies, biomedical applications, and challenges

In recent years, thermosensitive polysaccharide-based injectable hydrogels have gained increasing attention in biomedical applications, including wound healing, drug delivery, and cartilage repair. These hydrogels have favorable biocompatibility, biodegradability, and tunable physical and chemical properties. Thermosensitive polysaccharide-based injectable hydrogels are a class of intelligent soft matter material. They can undergo a reversible liquid-solid transition when exposed to temperature stimuli. Therefore, their precursor solutions can be accurately inserted into target sites with irregular geometries in a minimally invasive way and then transformed into gels in situ by the organism’s temperature stimulation to deliver biologically active molecules. This review summarizes the recent developments of thermosensitive injectable polysaccharide-based hydrogels. The focus is on the mechanism of sol-gel phase transition, as well as the design and preparation of thermosensitive polysaccharides and their applications in biomedical fields. In addition, the outlook of the challenges in biomedical applications is provided at the end of the paper.

Hydrogel-integrated multimodal biosensor for the detection of glucose and carcinoembryonic antigen

Multimodal biosensors can reduce false negative/positive rates to produce more reliable results. In this study, we report a multimodal biosensor that can achieve the detection of biomarkers by color, temperature and distance signals. The detection of glucose and carcinoembryonic antigen (CEA) is demonstrated as an example. The horseradish peroxidase (HRP), glucose oxidase (GOx) and 3,3′,5,5′-tetramethylbenzidine (TMB) are all entrapped in the gelatin hydrogel. When glucose is present, the final product oxTMB shows the blue signal and photothermal effect that can cause the gel-sol phase transition of the gelatin hydrogel, which enables the detection of glucose based on color, temperature and water flow distance on the pH indicator paper. To further broaden the application of this biosensor, a multimodal immunosensor is constructed to detect CEA using detection antibody-modified MnO2 Nanoflowers (NFs) as detection probe. Based on the oxidase-like activity of MnO2 NFs and the gel-sol transition property of the gelatin hydrogel, the detection of CEA with multiple signals as mentioned above was achieved by the sandwich immunoassay. Additionally, the detection of glucose and CEA is also fulfilled for in real samples. Overall, the hydrogel-integrated multimodal biosensor is simple to operate and the resulting multiple signals can complement each other, providing a versatile method for analysis of biomarkers.

Thermosensitive composite based on agarose and chitosan saturated with carbon dioxide. Preliminary study of requirements for production of new CSAG bioink

This study introduces a method for producing printable, thermosensitive bioink formulated from agarose (AG) and carbon dioxide-saturated chitosan (CS) hydrogels. The research identified medium molecular weight chitosan as optimal for bioink production, with a preferred chitosan hydrogel content of 40–60 %. Rheological analysis reveals the bioink's pseudoplastic behavior and a sol-gel phase transition between 27.0 and 31.5 °C. The MMW chitosan-based bioink showed also the most stable extrusion characteristic. The choice of chitosan for the production of bioink was also based on the assessment of the antimicrobial activity of the polymer as a function of its molecular weight and the degree of deacetylation, noting significant cell reduction rates for E. coli and S. aureus of 1.72 and 0.54 for optimal bioink composition, respectively. Cytotoxicity assessments via MTT and LDH tests confirm the bioink's safety for L929, HaCaT, and 46BR.1 N cell lines. Additionally, XTT proliferation assay proved the stimulating effect of the bioink on the proliferation of 46BR.1 N fibroblasts, comparable to that observed with Fetal Bovine Serum (FBS). FTIR spectroscopy confirms the bioink as a physical polymer blend. In conclusion, the CS/AG bioink demonstrates the promising potential for advanced spatial cell cultures in tissue engineering applications including skin regeneration.

Reactive Oxygen Species Scavenging Injectable Hydrogel Potentiates the Therapeutic Potential of Mesenchymal Stem Cells in Skin Flap Regeneration.

Cell-based therapies offer tremendous potential for skin flap regeneration. However, the hostile microenvironment of the injured tissue adversely affects the longevity and paracrine effects of the implanted cells, severely reducing their therapeutic effectiveness. Here, an injectable hydrogel (nGk) with reactive oxygen species (ROS) scavenging capability, which can amplify the cell viability and functions of encapsulated mesenchymal stem cells (MSCs), is employed to promote skin flap repair. nGk is formulated by dispersing manganese dioxide nanoparticles (MnO2 NPs) in a gelatin/κ-carrageenan hydrogel, which exhibits satisfactory injectable properties and undergoes a sol-gel phase transition at around 40 °C, leading to the formation of a solid gel at physiological temperature. MnO2 NPs enhance the mechanical properties of the hydrogel and give it the ability to scavenge ROS, thus providing a cell-protective system for MSCs. Cell culture studies show that nGk can mitigate the oxidative stress, improve cell viability, and boost stem cell paracrine function to promote angiogenesis. Furthermore, MSC-loaded nGk (nGk@MSCs) can improve the survival of skin flaps by promoting angiogenesis, reducing inflammatory reactions, and attenuating necrosis, providing an effective approach for tissue regeneration. Collectively, injectable nGk has substantial potential to enhance the therapeutic benefits of MSCs, making it a valuable delivery system for cell-based therapies.

Ion-interferential cell cycle arrest for melanoma treatment based on magnetocaloric bimetallic-ion sustained release hydrogel

Melanoma treatment has been revolutionized with the development of targeted therapies and immunotherapies, which shows a positive influence on the patients. However, the long-term efficaciousness of such therapy is restricted by side effects, limited clinical effects as well as quick resistance to treatment. In this work, we prepared magnetocaloric carrier-free bimetallic hydrogels, named manganese-iron oxide nanocubes@polyethylene glycol-hydrogels (MFO@PEG-Gels), to realize ion-interferential cell cycle arrest for melanoma treatment. In detail, the tumor site was exposed to alternating magnetic field (AMF) after intratumorally injected MFO@PEG-Gels, which generated hyperthermia and promoted the sol-gel phase transition for MFO sustained release. Under the tumor microenvironment, hydrogen peroxide triggered MFO degradation to induce Mn2+ and Fe3+ release. On one hand, Mn2+ blocked G1/S phase through the activation of p27 pathway. On the other hand, Fe3+ could arrest the G2/M phase by upregulating the polo-like kinase 4 (PLK4) expression as well as inhibiting autolysosome formation to achieve the enhanced cell cycle arrest, thereby promoting the apoptosis of melanoma cells. In summary, this study proposed ion-interferential cell cycle arrest strategy by a multifunctional and injectable magnetic bimetallic hydrogel for melanoma treatment, which provided a secure and sustainable regimen for enhancing anti-tumor efficacy.

Hydrogen bonding regulation on phase change in stimuli responsive copolymer aqueous solution

Hydrogen bonding (HB) is vital for the phase transition and physical properties of stimuli responsive copolymers. However, the governing mechanism remains unclear. Herein, we investigated the HB dynamics in a representative thermo-responsive copolymer (PNIPAM-AM) aqueous solution. Three types of HB were identified: polymer-polymer chain (CO:H–N), polymer chain-water molecule (CO:H–O) and water-water molecules (H–O:H–O) by vibrational spectroscopy. Increasing polymer concentration, the H–O:H–O softened and CO:H–O stiffened, leading to the destruction of HB network in water-water clusters. Upon increasing solution temperature, CO:H–O softened while CO:H–N stiffened, resolving the dehydration and cross-linking of polymer chains. Confinement of water molecules in the “cages” (∼ tens to hundreds of micrometers) after sol-gel phase transition was visualized, disclosing the mechanism of water holding capacity of PNIPAM-AM. The correlation of molecule vibration and copolymer microscopic structure was established, contributing to the fundamental understanding of phase behavior and physical properties regulations in stimuli responsive copolymer aqueous solution.

Recent research progress on tumour-specific responsive hydrogels.

Most existing hydrogels, even recently developed injectable hydrogels that undergo a reversible sol-gel phase transition in response to external stimuli, are designed to gel immediately before or after implantation/injection to prevent the free diffusion of materials and drugs; however, the property of immediate gelation leads to a very weak tumour-targeting ability, limiting their application in anticancer therapy. Therefore, the development of tumour-specific responsive hydrogels for anticancer therapy is imperative because tumour-specific responses improve their tumour-targeting efficacy, increase therapeutic effects, and decrease toxicity and side effects. In this review, we introduce the following three types of tumour-responsive hydrogels: (1) hydrogels that gel specifically at the tumour site; (2) hydrogels that decompose specifically at the tumour site; and (3) hydrogels that react specifically with tumours. For each type, their compositions, the mechanisms of tumour-specific responsiveness and their applications in anticancer treatment are comprehensively discussed.

New features of edge-selectively hydroxylated graphene nanosheets as NIR-II photothermal agent and sonothermal agent for tumor therapy.

Second near-infrared (NIR-II) laser-mediated photothermal therapy and sonothermal therapy using low-intensity focused ultrasound exposure for tumors have attracted increasing attention owing to their ability to penetrate deep tissues and provide noninvasive ablation with high therapeutic efficacy. However, their applications were limited by the shortness of optimal NIR-II photothermal agents and sonothermal agents. In this study, we discovered that the edge-selectively hydroxylated graphene nanosheets (EHG NSs) with excellent water dispersibility and an "intact conjugated plane" were not only an outstanding NIR-II photothermal agent but also an effective sonothermal agent for tumor therapy. EHG NSs were incorporated into an injectable adhesive thermosensitive hydrogel with a characteristic sol-gel phase transition behavior. EHG NSs endowed the injectable hydrogel with an exceptional photothermal effect under the laser irradiation (1064 nm, 1.0 W cm-2) as well as an effective sonothermal effect under ultrasonic exposure (3.0 MHz, 2.1 W cm-2), effectively killing tumor cells in vitro and inhibiting tumor growth after intratumoral injection. Especially, the NIR-II photothermal therapy based on the hybrid hydrogel completely ablated the primary tumors and effectively activated systemic anti-tumor immune responses benefiting from the protein adsorption capacity of the injectable hydrogel, significantly inhibiting the growth of the distal tumors. Collectively, EHG nanosheets loaded in the injectable hydrogel will be a promising "all-rounder" for noninvasive deep penetrating thermotherapy and a potent platform that integrates various therapies.

A suture-free, shape self-adaptive and bioactive PEG-Lysozyme implant for Corneal stroma defect repair and rapid vision restoration.

Corneal transplantation is a prevailing treatment to repair injured cornea and restore vision but faces the limitation of donor tissue shortage clinically. In addition, suturing-needed transplantation potentially causes postoperative complications. Herein, we design a PEG-Lysozyme injective hydrogel as a suture-free, shape self-adaptive, bioactive implant for corneal stroma defect repair. This implant experiences a sol-gel phase transition via an in situ amidation reaction between 4-arm-PEG-NHS and lysozyme. The physicochemical properties of PEG-Lysozyme can be tuned by the components ratio, which confers the implant mimetic corneal modulus and provides tissue adhesion to endure increased intraocular pressure. In vitro tests prove that the implant is beneficial to Human corneal epithelial cells growth and migration due to the bioactivity of lysozyme. Rabbit lamellar keratoplasty experiment demonstrates that the hydrogel can be filled into defect to form a shape-adaptive implant adhered to native stroma. The implant promotes epithelialization and stroma integrity, recovering the topology of injured cornea to normal. A newly established animal forging behavior test prove a rapid visual restoration of rabbits when use implant in a suture free manner. In general, this work provides a promising preclinical practice by applicating a self-curing, shape self-adaptive and bioactive PEG-Lysozyme implant for suture-free stroma repair.

Fabrication of Low-Temperature Fast Gelation β-Cyclodextrin-Based Hydrogel-Loaded Medicine for Wound Dressings.

β-Cyclodextrin (β-CD) is often used as a drug carrier for biomedical materials due to its unique cavity structure. Herein, β-CD was modified by acryloyl chloride and further copolymerized with N-isopropylacrylamide (NIPAM) and acrylic acid (AA) to obtain PNIPAM-co-β-CD-AC. The results showed that the critical phase transition temperature of PNIPAM/β-CD-AC could be controlled at 19 °C, and the fast sol-gel phase transition was realized in 2-10 s. The hydrophobic drug carried in this hydrogel can constantly be released for more than 6 days at pH values (pH 5.5-8), and the duration may match the recovery of the wound. As a dressing hydrogel, its rapid gel formation and inversion as well as shear-thinning behavior prevent secondary wound damage. The β-CD-based hydrogel also has good biocompatibility and antioxidant properties, which provide a good potential choice for wound dressings, especially for exposed wounds in winter.

Characterizing Phase Transitions of Microfibrillated Cellulose Induced by Anionic and Cationic Surfactants.

Rheological modifiers are used to tune rheology or induce phase transitions of products. Microfibrillated cellulose (MFC), a renewable material, has the potential to be used for rheological modification. However, the lack of studies on the evolution in rheological properties and structure during its phase transitions has prevented MFC from being added to consumer, fabric, and home care products. In this work, we characterize surface-oxidized MFC (OMFC), a negatively charged colloidal rod suspension. We measure the rheological properties and structure of OMFC during sol-gel phase transitions induced by either anionic or cationic surfactant using multiple particle tracking microrheology (MPT). MPT tracks the Brownian motion of fluorescent probe particles embedded in a sample, which is related to the sample's rheological properties. Using MPT, we measure that OMFC gelation evolution is dependent on the charge of the surfactant that induces the phase transition. OMFC gelation is gradual in anionic surfactant. In cationic surfactant, gelation is rapid followed by length scale-dependent colloidal fiber rearrangement. Initial OMFC concentration is directly related to how tightly associated the network is at the phase transition, with an increase in concentration resulting in a more tightly associated network with smaller pores. Bulk rheology measures that OMFC forms a stiffer structure but yields at lower strains in cationic surfactant than in anionic surfactant. This study characterizes the role of surfactant in inducing phase transitions, which can be used as a guide for designing future products.

Intravesical chemotherapy synergize with an immune adjuvant by a thermo-sensitive hydrogel system for bladder cancer

Surgical resection remains the prefer option for bladder cancer treatment. However, the effectiveness of surgery is usually limited for the high recurrence rate and poor prognosis. Consequently, intravesical chemotherapy synergize with immunotherapy in situ is an attractive way to improve therapeutic effect. Herein, a combined strategy based on thermo-sensitive PLEL hydrogel drug delivery system was developed. GEM loaded PLEL hydrogel was intravesical instilled to kill tumor cells directly, then PLEL hydrogel incorporated with CpG was injected into both groins subcutaneously to promote immune responses synergize with GEM. The results demonstrated that drug loaded PLEL hydrogel had a sol-gel phase transition behavior in response to physiological temperature and presented sustained drug release, and the PLEL-assisted combination therapy could have better tumor suppression effect and stronger immunostimulating effect in vivo. Hence, this combined treatment with PLEL hydrogel system has great potential and suggests a clinically-relevant and valuable option for bladder cancer.

Gelation of cytoplasmic expanded CAG RNA repeats suppresses global protein synthesis.

RNA molecules with the expanded CAG repeat (eCAGr) may undergo sol-gel phase transitions, but the functional impact of RNA gelation is completely unknown. Here, we demonstrate that the eCAGr RNA may form cytoplasmic gel-like foci that are rapidly degraded by lysosomes. These RNA foci may significantly reduce the global protein synthesis rate, possibly by sequestering the translation elongation factor eEF2. Disrupting the eCAGr RNA gelation restored the global protein synthesis rate, whereas enhanced gelation exacerbated this phenotype. eEF2 puncta were significantly enhanced in brain slices from a knock-in mouse model and from patients with Huntington's disease, which is a CAG expansion disorder expressing eCAGr RNA. Finally, neuronal expression of the eCAGr RNA by adeno-associated virus injection caused significant behavioral deficits in mice. Our study demonstrates the existence of RNA gelation inside the cells and reveals its functional impact, providing insights into repeat expansion diseases and functional impacts of RNA phase transition.