An injectable shear-thinning biomaterial for endovascular embolization

Innovative liquid embolic agents based on deep eutectic solvent: Rapid gelation in situ via solvent exchange with water for endovascular embolization

Current liquid embolic agents face several challenges, including poor biocompatibility and vascular recanalization. Herein, we propose an innovative liquid embolic agent composed of a coenzyme-based polymer (poly lipoic acid, PLA) and a biocompatible solvent (deep eutectic solvent, DES). The agent undergoes phase transformation to form a stable hydrogel in situ through solvent exchange with water, thereby enabling safe and effective embolization. First, DES is obtained by heating a mixture of choline chloride (ChCl) and glycerol (Gly). Subsequently, lipoic acid (LA) is incorporated into the DES and heated to produce the PLA/DES complex. Owing to the strong hydrogen bonding between the DES and PLA, the DES acts as a solvent while also inhibiting PLA depolymerization. Upon contact with blood, most of the DES exchange with water, whereas some amount of ChCl integrates within the PLA via strong hydrogen bonding. This hydrogen bonding not only prevents PLA depolymerization but also reinforces the PLA network, resulting in a stable PLA hydrogel rather than depolymerized LA monomers. Furthermore, liquid-metal (LM) nanoparticles are incorporated to fabricate radiopaque PLA/LM/DES. PLA/LM/DES shows better in vitro hemocompatibility and cytocompatibility, milder inflammatory response in a rat model, and more effective and safer embolization in a rabbit model than a commercial embolic agent (Onyx). Thus, this work provides an innovative liquid embolic agent and broadens the biomedical applications of DES.

Rapid closure and hemostasis of ruptured soft tissues using a modified human tropoelastin-based sealant in preclinical models

Treatment of injuries to soft elastic organs is often hindered by challenging anatomical features and limitations of existing sealant materials, which may lack adequate tissue adhesion, elasticity, biocompatibility, and effective hemostatic properties. To address these clinical challenges, we developed an injectable elastic sealant formulated with methacryloyl-modified human recombinant tropoelastin (MeTro) and Laponite silicate nanoplatelets (SNs). We optimized the hydrogel formulation for mechanical properties, adhesion, biocompatibility, and hemostatic properties and used visible light for cross-linking to improve safety. MeTro/SN hydrogels had increased tissue adhesion strength and burst pressure in vitro and ex vivo compared with MeTro alone or commercial sealants. The addition of SNs to the hydrogels facilitated faster blood clotting in vitro without increasing hemolysis. Applied to incisional injuries on rat lungs or aortas, MeTro/SN had burst pressures comparable to those of native tissue and greater than those of MeTro after a 7-day in vivo application. On porcine lungs, MeTro/SN also supported effective lung sealing and burst pressure similar to native lung 14 days after injury sealing. In a rodent tail hemostasis model, MeTro/SN reduced bleeding compared with MeTro. In an injured porcine lung model, early hemostasis was better than the tested commercial sealants. The results demonstrated that MeTro/SN provided effective tissue sealing and promoted hemostasis in a time frame that minimized blood loss without causing a major inflammatory response. These findings highlight the translational potential of our engineered sealant with biomimetic mechanics, durable tissue adhesion, and rapid hemostasis as a multipronged approach for the sealing and repair of traumatic injuries to soft organs.

Catheter Injectable Multifunctional Biomaterial for the Treatment of Infected Enterocutaneous Fistulas

Enterocutaneous fistulas (ECF) are challenging to treat contributing to high morbidity and high mortality rates, significantly impacting the quality of life of the patients. Its susceptibility to antibiotic-resistant infections often leads to chronic inflammation, complicating treatment with conventional methods. Here, 18NC75-10P-1IL is reported, which is a multi-functional shear-thinning hydrogel comprised of gelatin and nanosilicates for injectability, an ionic liquid for bactericidal effects, and platelet rich fibrin fraction for pro-healing properties; this biomaterial is engineered for the treatment of ECFs. Through rigorous testing, the mechanical properties of 18NC75-10P-1IL were tailored for catheter injection to achieve durable occlusion of fistulous tracts under external pressures simulating clinical scenarios. 18NC75-10P-1IL demonstrated pro-healing effects and anti-microbial activity against highly resistant patient-derived bacteria known to be associated with ECF. Subcutaneous implantation and anorectal fistula models confirmed its biocompatibility, pro-healing, anti-inflammatory, and anti-microbial properties compared to control materials, suggesting promising potential for clinical translation in the treatment of human ECFs.

Real-world clinical experience with Obsidio Conformable Embolic

BACKGROUND

Obsidio Conformable Embolic (Obsidio) is a ready-made hydrogel with unique shear-thinning properties, used for occlusion of blood flow to control bleeding or hemorrhage in the peripheral vasculature and embolization of hypervascular tumors. While pre-clinical and clinical data have demonstrated successful embolizations using Obsidio, clinical experience overall is still limited, prompting a multi-institutional field assessment survey to collect additional data on the clinical utility and procedural details from a variety of Obsidio users. The field survey collected data from 131 embolization procedures performed using Obsidio between May and November 2023 at 27 institutions within the United States. Data collection included embolization site, vessel size, any adjunctive embolics used. The primary objective of the survey was to evaluate technical success, defined as complete embolization of the target vasculature immediately following the index procedure, as confirmed by angiography.

RESULTS

Of the 131 embolization procedures performed, 69% (n = 90) were for hemorrhage control, 15% (n = 19) were for hypervascular tumors, and 17% (n = 22) were for other indications. Embolization of the gastroduodenal artery was the most common indication (n = 19/131; 15%). A single syringe (1 mL) or less of Obsidio was used for most cases (93%). In 33/131 cases (25%), Obsidio was combined with other embolization devices including coils (n = 25; 19%), particle-based embolics (n = 6; 4.6%), or plugs (n = 2; 1.5%). Technical success was achieved in 100% of Obsidio embolization cases (131/131 procedures).

CONCLUSION

Initial clinical experience demonstrated successful embolization of end-organ bleeds and hypervascular tumors utilizing Obsidio, thus making it an effective embolic agent alone or in conjunction with other embolic devices.

Self-assembling chemodrug fiber-hydrogel for transarterial chemoembolization and radiotherapy-enhanced antitumor immunity

Hydrogel, as a promising embolic material for hepatocellular carcinoma (HCC), may fully embolize both major vessels and peripheral microvessels. A self-assembling hydrogel composed of chemotherapeutic drugs offers significant clinical benefits without carrier introduction. Herein, we developed a sustained drug-releasing complex hydrogel (RKT@gel), which was fabricated by the self-assembly of raltitrexed chemotherapeutic drugs (R@gel), along with the incorporation of kaempferol and tantalum nanoparticles (Ta NPs). Kaempferol enhances the mechanical strength of R@gel and inhibits hypoxia-induced angiogenesis post-embolization, improving embolization effectiveness. In addition to enabling X-ray-guided transarterial chemoembolization (TACE), Ta NPs enhance radiation sensitivity. These synergistic effects of RKT@gel not only significantly induce immunogenic cell death, thereby enhancing the activation of dendritic cells, but also activate major histocompatibility complex class I (MHC-I)-mediated antitumor immune recognition and cytotoxicity. In vivo, RKT@gel achieves enhanced tumor deposition and sustained drug release, effectively suppressing tumor progression. Additionally, when combined with radiotherapy, RKT@gel achieves efficient antitumor immunoactivation. Overall, this versatile composite hydrogel not only achieves effective embolization therapy but also substantially triggers antitumor immune responses with good biocompatibility. This multifunctional design provides a TACE-based multidisciplinary strategy for HCC.

A Single Institution Experience with a Shear-Thinning Conformable Embolic for Endovascular Embolization

PURPOSE

To assess the safety and efficacy of Obsidio™ conformable embolic (CE) for embolization in the peripheral vasculature.

MATERIALS AND METHODS

A retrospective review of the first 21 patients treated with CE was performed. Eighteen (85.7%) patients were male, and median age was 61.5 years (range, 12-89 years). Technical success was defined as stasis as assessed by a static contrast column for at least 5 heartbeats on post-embolization angiography. For procedures of peripheral vascular hemorrhage, clinical success was defined as hemorrhage resolution without reintervention within 30-day follow-up.

RESULTS

Indications for embolization were peripheral arterial hemorrhage (n = 13), preoperative tumor embolization (n = 4), preoperative embolization of renal cell carcinoma prior to cryoablation (n = 2), redistribution of flow prior to Yttrium-90 radioembolization to prevent nontarget radiation delivery (n = 1), and parastomal variceal embolization (n = 1). Embolization was performed via 2.4 or 2.8 French microcatheters flushed with saline prior to embolization. Most procedures (20/21) utilized < 1 cc of embolic, with the quantity used ranging between 0.1 and 1.4 cc. The amount of embolic injected was determined by the embolization endpoint, i.e., filling of the vessel intended for embolization. CE was used in combination with coils placed prior to CE in 4 procedures. Follow-up was a median of 57 days (range 0-244 days). Complete stasis was achieved in 100% (n = 21/21) of procedures. There were no post-procedure adverse events or rebleeding.

CONCLUSION

CE resulted in reliable vessel occlusion with no cases of rebleeding or reintervention and with no procedure-related adverse events in this series.

LEVEL OF EVIDENCE

Level 4, Case Series.

Hydrogel-based nanoparticles: revolutionizing brain tumor treatment and paving the way for future innovations

Brain tumor treatment remains a significant challenge due to their high mortality and resistance to current therapies. This paper discusses the promising potential of hydrogel-based nanoparticles as innovative drug delivery systems for brain tumor therapy. Extensive characterization techniques reveal the ability of these Nano-systems to demonstrate prolonged blood circulation and targeted delivery, leading to improved survival rates. Designed with optimized physicochemical characteristics, these nanoparticles effectively cross the blood-brain barrier, circumventing a major impediment to drug delivery to the brain. By delivering drugs directly to the tumor bed, these nanoparticles enhance therapeutic outcomes and minimize adverse effects. In addition, this review investigates the techniques for characterizing, visualizing, and modifying these nanoparticles, as well as the standing challenges and promising research avenues for their clinical application. Further investigations are encouraged by this review to investigate potential advancements in hydrogel-based nanoparticle therapeutic approaches for brain tumors. This includes investigating tailored hydrogels, hybrid systems, computational modeling, and the integration of gene therapy and immunotherapy techniques. The study also addresses the need for enhanced synthesis techniques, stability, scalability, and cost-cutting measures to overcome obstacles and advance the clinical use of hydrogel-based nanoparticles in treating brain tumors.

Advancements in Nanomedicine for the Diagnosis and Treatment of Kidney Stones

Kidney stones constitute a common condition impacting the urinary system. In clinical diagnosis and management, traditional surgical interventions and pharmacological treatments are primarily utilized; however, these methods possess inherent limitations. Presently, the field of nanomedicine is undergoing significant advancements. The application of nanomaterials in biosensors enables the accurate assessment of urinary ion composition. Furthermore, contrast agents developed from these materials can improve the signal-to-noise ratio and enhance image clarity. By mitigating oxidative stress-induced cellular damage, nanomaterials can inhibit the formation of kidney stones and enhance the efficacy of drug delivery as effective carriers. Additionally, by modifying the physical and chemical properties of bacteria, nanomaterials can effectively eliminate bacterial presence, thereby preventing severe complications. This review explores the advancements in nanomaterials technology related to the early detection of risk factors, clinical diagnosis, and treatment of kidney stones and their associated complications.

Intelligent Generic High-Throughput Oscillatory Shear Technology Fabricates Programmable Microrobots for Real-Time Visual Guidance During Embolization

Microrobots for endovascular embolization face challenges in precise delivery within dynamic blood vessels. Here, an intelligent generic high-throughput oscillatory shear technology (iGHOST) is proposed to fabricate diversely programmable, multifunctional microrobots capable of real-time visual guidance for in vivo endovascular embolization. Leveraging machine learning (ML), key synthesis parameters affecting the success and sphericity of the microrobots are identified. Therefore, the ML-optimized iGHOST enables continuous production of uniform microrobots with programmable sizes (400-1000 µm) at an ultrahigh rate exceeding 240 mL h-1 by oscillatory segmenting fluid into droplets before ionic cross-linking, and without requiring purification. Particularly, the iGHOST-fabricated magnetically responsive lipiodol-calcium alginate (MagLiCA) microrobots are highly distinguishable under X-ray imaging, which allows for precise navigation in fluid flows of up to 4 mL min-1 and accurate embolization in liver and kidney blood vessels, thus addressing the current issues. Crucially, MagLiCA microrobots possess drug-loading capabilities, enabling simultaneous embolization and site-specific treatment. The iGHOST process is an intelligent, rapid, and green manufacturing method, which can produce size-controllable, multifunctional microrobots with the potential for precise drug delivery and treatment under real-time imaging across various medical applications.

Enhanced sclerotherapy for vascular malformations: A dual-mechanism approach using in-situ forming PATDs gel

Vascular malformations are common vascular lesions in infants and seriously affect their health and quality of life. Vascular sclerotherapy is an effective treatment for vascular malformations. However, current sclerosants have difficulty achieving both high efficiency and low toxicity, and their dosing forms make it difficult to achieve long-term retention in the affected blood vessels. Therefore, exploring a safe and effective sclerosant and its delivery strategy is the key to clinical sclerotherapy. To address the above issues, this study developed sclerosants that could form an in-situ gel based on a dual mechanism of vascular injury and plasmin (PLA) inhibition. By linking the non-ionic surfactant sclerosant polyoxyethylene alkyl ether (PAs) and the PLA inhibitor tranexamic acid (TA) through an ester bond, a cationic surfactant sclerosant polyoxyethylene alkylether tranexamate derivatives (PATDs) were constructed. The cationic charge of PATDs enhanced its cytotoxicity to HUVEC-TIE2-L914F cells, and the ester bond of PATDs could be degraded by esterase in the blood, reducing its systemic toxicity. The degradation product TA inhibited the activation of the PLA-matrix metalloproteinase (MMPs) system induced by vascular injury, thereby promoting the deposition of collagen and the proliferation and differentiation of fibroblasts to promote vascular fibrosis. In addition, an injectable solution (PATDs/GA) was prepared by mixing PATDs with glycerol formaldehyde (GA), and PATDs/GA could form a low-molecular-weight gel automatically in an aqueous solution, which was beneficial to increase its retention in the affected blood vessels and reduce the risk of drug entering non-targeted sites. At the same time, this gel automatically dissolved, reducing the risk of immune rejection caused by long-term retention. This study provided a new and precise approach for the treatment of vascular sclerosis with high efficiency and low toxicity.

Protecting Against Postsurgery Oral Cancer Recurrence with an Implantable Hydrogel Vaccine for In Situ Photoimmunotherapy

Oral squamous cell carcinoma (OSCC) often recurs aggressively and metastasizes despite surgery and adjuvant therapy, driven by postoperative residual cancer cells near the primary tumor site. An implantable in situ vaccine hydrogel was designed to target residual OSCC cells post-tumor removal. This hydrogel serves as a reservoir for the sustained localized release of δ-aminolevulinic acid (δ-ALA), enhancing protoporphyrin IX-mediated photodynamic therapy (PDT), and a polydopamine-hyaluronic acid composite for photothermal therapy (PTT). Additionally, immune adjuvants, including anti-CD47 antibodies (aCD47) and CaCO3 nanoparticles, are directly released into the resected tumor bed. This approach induces apoptosis of residual OSCC cells through sequential near-infrared irradiation, promoting calcium interference therapy (CIT). The hydrogel further stimulates immunogenic cell death (ICD), facilitating the polarization of tumor-associated macrophages from the M2 to the M1 phenotype. This facilitates phagocytosis, dendritic cell activation, robust antigen presentation, and cytotoxic T lymphocyte-mediated cytotoxicity. In murine OSCC models, the in situ vaccine effectively prevents local recurrence, inhibits orthotopic OSCC growth and pulmonary metastases, and provides long-term protective immunity against tumor rechalle nge. These findings support postoperative in situ vaccination with a biocompatible hydrogel implant as a promising strategy to minimize residual tumor burden and reduce recurrence risk after OSCC resection.

A novel conformable embolic for selective transarterial embolization of acute hemorrhages: a technical note

BACKGROUND

Obsidio conformable embolic (OCE, Boston Scientific, MA) is a novel, radiopaque and conformable embolic. The purpose of this report is to describe its use for treatment of acute intra-abdominal hemorrhages.

METHODS AND RESULTS

Three patients presented with acute hemorrhage and were treated with OCE, including post-paracentesis hemorrhage, penetrating trauma to the liver, and blunt trauma in the spleen. All cases were performed under moderate sedation, with hemostasis achieved by end of procedure using less than 1 vial of OCE (0.2-0.4 ml). No severe adverse events occurred. None required repeated treatment.

SHORT CONCLUSION

OCE is a safe and effective embolic agent for treatment of intra-abdominal or visceral hemorrhage. Future studies with larger sample sizes and longer follow-up are warranted.

Percutaneous Delivery of Oncogel for Targeted Liver Tumor Ablation and Controlled Release of Therapeutics

Advanced-stage liver cancers are associated with poor prognosis and have limited treatment options, often leading the patient to hospice care. Percutaneous intratumoral injection of anticancer agents has emerged as a potential alternative to systemic therapy to overcome tumor barriers, increase bioavailability, potentiate immunotherapy, and avoid systemic toxicity, which advanced-stage cancer patients cannot tolerate. Here, an injectable OncoGel (OG) comprising of a nanocomposite hydrogel loaded with an ionic liquid (IL) is developed for achieving a predictable and uniform tumor ablation and long-term slow release of anticancer agents into the ablation zone. Rigorous mechanical, physiochemical, drug release, cytotoxicity experiments, and ex vivo human tissue testing identify an injectable version of the OG with bactericidal properties against highly resistant bacteria. Intratumoral injection of OG loaded with Nivolumab (Nivo) and doxorubicin (Dox) into highly malignant tumor models in mice, rats, and rabbits demonstrates enhanced survival and tumor regression associated with robust tissue ablation and drug distribution throughout the tumor. Mass cytometry and proteomic studies in a mouse model of colorectal cancer that often metastasizes to the liver indicate an enhanced anticancer immune response following the intratumoral injection of OG. OG may augment immunotherapy and potentially improve outcomes in liver cancer patients.

Intravascular elimination of circulating tumor cells and cascaded embolization with multifunctional 3D tubular scaffolds

The primary tumor ("root") and circulating tumor cells (CTCs; "seeds") are vital factors in tumor progression. However, current treatment strategies mainly focus on inhibiting the tumor while ignoring CTCs, resulting in tumor metastasis. Here, we design a multifunctional 3D scaffold with interconnected macropores, excellent photothermal ability and perfect bioaffinity as a blood vessel implantable device. When implanted upstream of the primary tumor, the scaffold intercepts CTCs fleeing back to the primary tumor and then forms "micro-thrombi" to block the supply of nutrients and oxygen to the tumor for embolization therapy. The scaffold implanted downstream of the tumor efficiently captures and photothermally kills the CTCs that escape from the tumor, thereby preventing metastasis. Experiments using rabbits demonstrated excellent biosafety of this scaffold with 86% of the CTC scavenging rate, 99% of the tumor inhibition rate and 100% of CTC killing efficiency. The multifunctional 3D scaffold synergistically inhibits the "root" and eliminates the "seeds" of the tumor, demonstrating its potential for localized cancer therapy with few side effects and high antitumor efficacy.

Functionalized hydrogels as smart gene delivery systems to treat musculoskeletal disorders

Despite critical advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy based on the delivery of therapeutic genetic sequences has strong value to offer effective, durable options to decisively manage such disorders. Furthermore, scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy, allowing for the spatiotemporal delivery of candidate genes to sites of injury. Among the many scaffolds for musculoskeletal research, hydrogels raised increasing attention in addition to other potent systems (solid, hybrid scaffolds) due to their versatility and competence as drug and cell carriers in tissue engineering and wound dressing. Attractive functionalities of hydrogels for musculoskeletal therapy include their injectability, stimuli-responsiveness, self-healing, and nanocomposition that may further allow to upgrade of them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. Such functionalized hydrogels may also be tuned to successfully transfer therapeutic genes in a minimally invasive manner in order to protect their cargos and allow for their long-term effects. In light of such features, this review focuses on functionalized hydrogels and demonstrates their competence for the treatment of musculoskeletal disorders using gene therapy procedures, from gene therapy principles to hydrogel functionalization methods and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are being discussed in the perspective of translation in patients. STATEMENT OF SIGNIFICANCE: Despite advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy has strong value in offering effective, durable options to decisively manage such disorders. Scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy. Among many scaffolds for musculoskeletal research, hydrogels raised increasing attention. Functionalities including injectability, stimuli-responsiveness, and self-healing, tune them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. This review introduces functionalized hydrogels for musculoskeletal disorder treatment using gene therapy procedures, from gene therapy principles to functionalized hydrogels and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are discussed from the perspective of translation in patients.

Biocompatible Liquid Embolic for the Treatment of Microvascular Hemorrhage

Persistent or recurrent bleeding from microvessels inaccessible for direct endovascular intervention is a major problem in medicine today. Here, an innovative catheter-directed liquid embolic (P-LE) is bioengineered for rapid microvessel embolization to treat small vessel hemorrhage. Tested in rodent, porcine, and canine animal models under normal and coagulopathic conditions, P-LE outperformed clinically used embolic materials in both survival and non-survival experiments, effectively occluding vessels as small as 40 microns with no signs of recanalization. P-LE occlusion is independent of the coagulation cascade, and its resistance to displacement is ≈ 8 times greater than systolic blood pressure. P-LE is also found to be biocompatible and x-ray visible and does not require polymerization or a chemical reaction to embolize. To simulate the clinical scenario, acute microvascular hemorrhage is created in the pig kidney, liver, or stomach; these are successfully treated with P-LE achieving immediate hemostasis. Furthermore, P-LE is found to be bactericidal to highly resistant patient-derived bacteria, suggesting that P-LE may also protect against infectious complications that may occur following embolization procedures. P-LE is safe, easy to use, and effective in treating -microvessel hemorrhage.

Development of an Injectable, ECM-Derivative Embolic for the Treatment of Cerebral Saccular Aneurysms

Cerebral aneurysms are a source of neurological morbidity and mortality, most often as a result of rupture. The most common approach for treating aneurysms involves endovascular embolization using nonbiodegradable medical devices, such as platinum coils. However, the need for retreatment due to the recanalization of coil-treated aneurysms highlights the importance of exploring alternative solutions. In this study, we propose an injectable extracellular matrix-derived embolic formed in situ by Michael addition of gelatin-thiol (Gel-SH) and hyaluronic acid vinyl sulfone (HA-VS) that may be delivered with a therapeutic agent (here, RADA-SP) to fill and remodel aneurysmal tissue without leaving behind permanent foreign bodies. The injectable embolic material demonstrated rapid gelation under physiological conditions, forming a highly porous structure and allowing for cellular infiltration. The injectable embolic exhibited thrombogenic behavior in vitro that was comparable to that of alginate injectables. Furthermore, in vivo studies in a murine carotid aneurysm model demonstrated the successful embolization of a saccular aneurysm and extensive cellular infiltration both with and without RADA-SP at 3 weeks, with some evidence of increased vascular or fibrosis markers with RADA-SP incorporation. The results indicate that the developed embolic has inherent potential for acutely filling cerebrovascular aneurysms and encouraging the cellular infiltration that would be necessary for stable, chronic remodeling.

A Single-Center Experience with a Shear-Thinning Conformable Embolic

The purpose of this study was to evaluate the technical success, effectiveness, and safety of transarterial embolization for acute bleeding management with a shear-thinning conformable embolic. This single-center retrospective study evaluated outcomes after embolization using Obsidio conformable embolic (OCE). Technical success was defined as performing transarterial embolization within the target vessel to complete stasis of antegrade flow. Treatment effectiveness was defined as cessation of bleeding for patients. Eleven patients underwent 11 embolization procedures. A total of 16 arteries were embolized. Indications for embolization were spontaneous tumor bleeding (6/11), hematuria (2/11), active duodenal bleeding (1/11), portal hypertensive bleeding (1/11), and rectus sheath hematoma (1/11). The technical success rate was 100%. The median vessel diameter was 2 mm (range, 1-3 mm). There were no adverse events or off-target embolization. OCE demonstrated technical success and treatment effectiveness with a short-term safety profile for transarterial embolization interventions.

Injectable Biodegradable Chitosan-PEG/PEG-Dialdehyde Hydrogel for Stem Cell Delivery and Cartilage Regeneration

Stem cell-based therapy holds promise for cartilage regeneration in treating knee osteoarthritis (KOA). Injectable hydrogels have been developed to mimic the extracellular matrix (ECM) and facilitate stem cell growth, proliferation, and differentiation. However, these hydrogels face limitations such as poor mechanical strength, inadequate biocompatibility, and suboptimal biodegradability, collectively hindering their effectiveness in cartilage regeneration. This study introduces an injectable, biodegradable, and self-healing hydrogel composed of chitosan-PEG and PEG-dialdehyde for stem cell delivery. This hydrogel can form in situ by blending two polymer solutions through injection at physiological temperature, encapsulating human adipose-derived stem cells (hADSCs) during the gelation process. Featuring a 3D porous structure with large pore size, optimal mechanical properties, biodegradability, easy injectability, and rapid self-healing capability, the hydrogel supports the growth, proliferation, and differentiation of hADSCs. Notably, encapsulated hADSCs form 3D spheroids during proliferation, with their sizes increasing over time alongside hydrogel degradation while maintaining high viability for at least 10 days. Additionally, hADSCs encapsulated in this hydrogel exhibit upregulated expression of chondrogenic differentiation genes and proteins compared to those cultured on 2D surfaces. These characteristics make the chitosan-PEG/PEG-dialdehyde hydrogel-stem cell construct suitable for direct implantation through minimally invasive injection, enhancing stem cell-based therapy for KOA and other cell-based treatments.

Chemically Programmed Hydrogels for Spatiotemporal Modulation of the Cardiac Pathological Microenvironment

After myocardial infarction (MI), sustained ischemic events induce pathological microenvironments characterized by ischemia-hypoxia, oxidative stress, inflammatory responses, matrix remodeling, and fibrous scarring. Conventional clinical therapies lack spatially targeted and temporally responsive modulation of the infarct microenvironment, leading to limited myocardial repair. Engineered hydrogels have a chemically programmed toolbox for minimally invasive localization of the pathological microenvironment and personalized responsive modulation over different pathological periods. Chemically programmed strategies for crosslinking interactions, interfacial binding, and topological microstructures in hydrogels enable minimally invasive implantation and in situ integration tailored to the myocardium. This enhances substance exchange and signal interactions within the infarcted microenvironment. Programmed responsive polymer networks, intelligent micro/nanoplatforms, and biological therapeutic cues contribute to the formation of microenvironment-modulated hydrogels with precise targeting, spatiotemporal control, and on-demand feedback. Therefore, this review summarizes the features of the MI microenvironment and chemically programmed schemes for hydrogels to conform, integrate, and modulate the cardiac pathological microenvironment. Chemically programmed strategies for oxygen-generating, antioxidant, anti-inflammatory, provascular, and electrointegrated hydrogels to stimulate iterative and translational cardiac tissue engineering are discussed.

Advanced Hydrogels in Breast Cancer Therapy

Breast cancer is the most common malignancy among women and is the second leading cause of cancer-related death for women. Depending on the tumor grade and stage, breast cancer is primarily treated with surgery and antineoplastic therapy. Direct or indirect side effects, emotional trauma, and unpredictable outcomes accompany these traditional therapies, calling for therapies that could improve the overall treatment and recovery experiences of patients. Hydrogels, biomimetic materials with 3D network structures, have shown great promise for augmenting breast cancer therapy. Hydrogel implants can be made with adipogenic and angiogenic properties for tissue integration. 3D organoids of malignant breast tumors grown in hydrogels retain the physical and genetic characteristics of the native tumors, allowing for post-surgery recapitulation of the diseased tissues for precision medicine assessment of the responsiveness of patient-specific cancers to antineoplastic treatment. Hydrogels can also be used as carrier matrices for delivering chemotherapeutics and immunotherapeutics or as post-surgery prosthetic scaffolds. The hydrogel delivery systems could achieve localized and controlled medication release targeting the tumor site, enhancing efficacy and minimizing the adverse effects of therapeutic agents delivered by traditional procedures. This review aims to summarize the most recent advancements in hydrogel utilization for breast cancer post-surgery tissue reconstruction, tumor modeling, and therapy and discuss their limitations in clinical translation.

An artificial liquid-liquid phase separation-driven silk fibroin-based adhesive for rapid hemostasis and wound sealing

The powerful adhesion systems of marine organisms have inspired the development of artificial protein-based bioadhesives. However, achieving robust wet adhesion using artificial bioadhesives remains technically challenging because the key element of liquid-liquid phase separation (LLPS)-driven complex coacervation in natural adhesion systems is often ignored. In this study, mimicking the complex coacervation phenomenon of marine organisms, an artificial protein-based adhesive hydrogel (SFG hydrogel) was developed by adopting the LLPS-mediated coacervation of the natural protein silk fibroin (SF) and the anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SF/SDBS complex coacervate enabled precise spatial positioning and easy self-adjustable deposition on irregular substrate surfaces, allowing for tight contact. Spontaneous liquid-to-solid maturation promoted the phase transition of the SF/SDBS complex coacervate to form the SFG hydrogel in situ, enhancing its bulk cohesiveness and interfacial adhesion. The formed SFG hydrogel exhibited intrinsic advantages as a new type of artificial protein-based adhesive, including good biocompatibility, robust wet adhesion, rapid blood-clotting capacity, and easy operation. In vitro and in vivo experiments demonstrated that the SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, thus advancing its clinical applications. STATEMENT OF SIGNIFICANCE: Marine mussels utilize the liquid-liquid phase separation (LLPS) strategy to induce the supramolecular assembly of mussel foot proteins, which plays a critical role in strong underwater adhesion of mussel foot proteins. Herein, an artificial protein-based adhesive hydrogel (named SFG hydrogel) was reported by adopting the LLPS-mediated coacervation of natural protein silk fibroin (SF) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SFG hydrogel enabled the precise spatial positioning and easy self-adjustable deposition on substrate surfaces with irregularities, allowing tight interfacial adhesion and cohesiveness. The SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, exhibiting intrinsic advantages as a new type of artificial protein-based bioadhesives.

Shape Self-Adaptive Liquid Embolic Agent for Ultrafast and Durable Vascular Embolization

Minimally invasive embolization greatly decreases the mortality resulting from vascular injuries while still suffering from a high risk of recanalization and systematic thrombosis due to the intrinsic hydrophobicity and poor adhesion of the clinically used liquid embolic agent of Lipiodol. In this study, a shape self-adaptive liquid embolic agent was developed by mixing biocompatible poly(acrylic acid) (PAA), two-dimensional magnesium-aluminum layered double hydroxide (LDH), and poly(ethylene glycol)200 (PEG200). Upon contact with blood, the injectable PAA-LDH@PEG200 would quickly absorb water to form an adhesive and mechanically strong PAA-LDH thin hydrogel within 5 s, which could firmly adhere to the blood vessel wall for ultrafast and durable embolization. In addition, benefiting from the "positively charged nucleic center effect" of LDH nanosheets, the liquid PAA-LDH@PEG200 could avoid vascular distension by PAA overexpansion and possess high shock-resistant mechanical strength from the blood flow. Furthermore, both in vitro and in vivo embolization experiments demonstrated the complete embolic capacity of liquid PAA-LDH@PEG200 without the occurrence of recanalization for 28 days and also the great potential to act as a platform to couple with chemotherapeutic drugs for the minimized transcatheter arterial chemoembolization (TACE) treatment of VX2 tumors without recurrence for 18 days. Thus, liquid PAA-LDH@PEG200 developed here possesses great potential to act as a shape self-adaptive liquid embolic agent for ultrafast and durable vascular embolization.

Minimally Invasive Delivery of Percutaneous Ablation Agent via Magnetic Colloidal Hydrogel Injection for Treatment of Hepatocellular Carcinoma

Percutaneous thermotherapy, a minimally invasive operational procedure, is employed in the ablation of deep tumor lesions by means of target-delivering heat. Conventional thermal ablation methods, such as radiofrequency or microwave ablation, to a certain extent, are subjected to extended ablation time as well as biosafety risks of unwanted overheating. Given its effectiveness and safety, percutaneous thermotherapy gains a fresh perspective, thanks to magnetic hyperthermia. In this respect, an injectable- and magnetic-hydrogel-construct-based thermal ablation agent is likely to be a candidate for the aforementioned clinical translation. Adopting a simple and environment-friendly strategy, a magnetic colloidal hydrogel injection is introduced by a binary system comprising super-paramagnetic Fe3O4 nanoparticles and gelatin nanoparticles. The colloidal hydrogel constructs, unlike conventional bulk hydrogel, can be easily extruded through a percutaneous needle and then self-heal in a reversible manner owing to the unique electrostatic cross-linking. The introduction of magnetic building blocks is exhibited with a rapid magnetothermal response to an alternating magnetic field. Such hydrogel injection is capable of generating heat without limitation of deep penetration. The materials achieve outstanding therapeutic results in mouse and rabbit models. These findings constitute a new class of locoregional interventional thermal therapies with minimal collateral damages.

Chitosan-nanoclay embolic material for catheter-directed arterial embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology. It is used for the deliberate occlusion of blood vessels for the treatment of disease or injured vasculature, including vascular malformation and malignant/benign tumors. Here, we introduce a gel embolic agent comprising chitosan nanofibers and nanoclay with excellent catheter injectability and tunable mechanical properties for embolization. The properties of the gel were optimized by varying the ratio between each individual component and also adjusting the total solid content. The rheological studies confirm the shear thinning property and gel nature of the developed gel as well as their recoverability. Injection force was measured to record the force required to pass the embolic gel through a clinically relevant catheter, evaluating for practicality of hand-injection. Theoretical predicted injection force was calculated to reduce the development time and to enhance the physician's experience. The stability of occlusion was also tested in vitro by monitoring the pressure required to displace the gel. The engineered gels exhibited sterility, hemocompatibility and cell biocompatibility, highlighting their potential for transcatheter embolization.

OnyxTMGel or Coil versus Hydrogel as Embolic Agents in Endovascular Applications: Review of the Literature and Case Series

This review focuses on the use of conventional gel or coil and "new" generation hydrogel used as an embolic agent in endovascular applications. In general, embolic agents have deep or multidistrict vascular penetration properties as they ensure complete occlusion of vessels by exploiting the patient's coagulation system, which recognises them as substances foreign to the body, thus triggering the coagulation cascade. This is why they are widely used in the treatment of endovascular corrections (EV repair), arteriovenous malformations (AVM), endoleaks (E), visceral aneurysms or pseudo-aneurysms, and embolisation of pre-surgical or post-surgical (iatrogenic) lesions. Conventional gels such as Onyx or coils are now commercially available, both of which are frequently used in endovascular interventional procedures, as they are minimally invasive and have numerous advantages over conventional open repair (OR) surgery. Recently, these agents have been modified and optimised to develop new embolic substances in the form of hydrogels based on alginate, chitosan, fibroin and other polymers to ensure embolisation through phase transition phenomena. The main aim of this work was to expand on the data already known in the literature concerning the application of these devices in the endovascular field, focusing on the advantages, disadvantages and safety profiles of conventional and innovative embolic agents and also through some clinical cases reported. The clinical case series concerns the correction and exclusion of endoleak type I or type II appeared after an endovascular procedure of exclusion of aneurysmal abdominal aortic (EVAR) with a coil (coil penumbra released by a LANTERN microcatheter), the exclusion of renal arterial malformation (MAV) with a coil (penumbra coil released by a LANTERN microcatheter) and the correction of endoleak through the application of Onyx 18 in the arteries where sealing by the endoprosthesis was not guaranteed.

Injectable Hydrogel Mucosal Vaccine Elicits Protective Immunity against Respiratory Viruses

Intranasal vaccines, eliciting mucosal immune responses, can prevent early invasion, replication, and transmission of pathogens in the respiratory tract. However, the effective delivery of antigens through the nasal barrier and boosting of a robust systematic and mucosal immune remain challenges in intranasal vaccine development. Here, we describe an intranasally administered self-healing hydrogel vaccine with a reversible strain-dependent sol-gel transition by precisely modulating the self-assembly processes between the natural drug rhein and aluminum ions. The highly bioadhesive hydrogel vaccine enhances antigen stability and prolongs residence time in the nasal cavity and lungs by confining the antigen to the surface of the nasal mucosa, acting as a "mucosal mask". The hydrogel also stimulates superior immunoenhancing properties, including antigen internalization, cross-presentation, and dendritic cell maturation. Furthermore, the formulation recruits immunocytes to the nasal mucosa and nasal-associated lymphoid tissue (NALT) while enhancing antigen-specific humoral, cellular, and mucosal immune responses. Our findings present a promising strategy for preparing intranasal vaccines for infectious diseases or cancer.

Construction of an Injectable Composite Double-Network Hydrogel as a Liquid Embolic Agent

Conventional embolists disreputably tend to recanalization arising from the low filling ratio due to their rigidity or instability. As a result, intelligent hydrogels with a tunable modulus may meaningfully improve the therapeutic efficacy. Herein, an injectable composite double-network (CDN) hydrogel with high shear responsibility was prepared as a liquid embolic agent by cross-linking poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMC) via dynamic covalent bonding of borate ester and benzoic-imine. A two-dimensional nanosheet, i.e., layered double hydroxide (LDH), was incorporated into the network through physical interactions which led to serious reduction of yield stress for the injection of the hydrogel and the capacity for loading therapeutic agents like indocyanine green (ICG) and doxorubicin (DOX) for the functions of photothermal therapy (PTT) and chemotherapy. The CDN hydrogel could thus be transported through a thin catheter and further in situ strengthened under physiological conditions, like in blood, by secondarily cross-linking with phosphate ions for longer degradation duration and better mechanical property. These characteristics met the requirements of arterial interventional embolization, which was demonstrated by renal embolism operation on rabbits, and meanwhile favored the inhibition of subcutaneous tumor growth on an animal model. Therefore, this work makes a breakthrough in the case of largely reducing the embolism risks, thus affording a novel generation for interventional embolization.

Advances and Challenges in Interventional Immuno-Oncology Locoregional Therapies

Interventional immuno-oncology is making strides in locoregional therapies to address complex tumor microenvironments. Long-standing interventional radiology cancer therapies, such as tumor ablation and embolization, are being recharacterized in the context of immunotherapy. Intratumoral injections, such as those of genetically engineered or unaltered viruses, and the delivery of immune cells, antibodies, proteins, or cytokines into targeted tumors, along with advancements in delivery techniques, have produced promising results in preliminary studies, indicating their antitumor effectiveness. Emerging strategies using DNA scaffolding, polysaccharides, glycan, chitosan, and natural products are also showing promise in targeted cancer therapy. The future of interventional immuno-oncology lies in personalized immunotherapies that capitalize on individual immune profiles and tumor characteristics, along with the exploration of combination therapies. This study will review various interventional immuno-oncology strategies and emerging technologies to enhance delivery of therapeutics and response to immunotherapy.

Injectable Nanoengineered Adhesive Hydrogel for Treating Enterocutaneous Fistulas

Enterocutaneous fistula (ECF) is a severe medical condition where an abnormal connection forms between the gastrointestinal tract and skin. ECFs are, in most cases, a result of surgical complications such as missed enterotomies or anastomotic leaks. The constant leakage of enteric and fecal contents from the fistula site leads to skin breakdown and increases the risk of infection. Despite advances in surgical techniques and postoperative management, ECF accounts for significant mortality rates, estimated between 15-20%, and causes debilitating morbidity. Therefore, there is a critical need for a simple and effective method to seal and heal ECF. Injectable hydrogels with combined properties of robust mechanical properties and cell infiltration/proliferation have the potential to block and heal ECF. Herein, we report the development of an injectable nanoengineered adhesive hydrogel (INAH) composed of a synthetic nanosilicate (Laponite®) and a gelatin-dopamine conjugate for treating ECF. The hydrogel undergoes fast cross-linking using a co-injection method, resulting in a matrix with improved mechanical and adhesive properties. INAH demonstrates appreciable blood clotting abilities and is cytocompatible with fibroblasts. The adhesive properties of the hydrogel are demonstrated in ex vivo adhesion models with skin and arteries, where the volume stability in the hydrated internal environment facilitates maintaining strong adhesion. In vivo assessments reveal that the INAH is biocompatible, supporting cell infiltration and extracellular matrix deposition while not forming fibrotic tissue. These findings suggest that this INAH holds promising translational potential for sealing and healing ECF.

Injectable Shear-Thinning Hydrogels with Sclerosing and Matrix Metalloproteinase Modulatory Properties for the Treatment of Vascular Malformations

Sac embolization of abdominal aortic aneurysms (AAAs) remains clinically limited by endoleak recurrences. These recurrences are correlated with recanalization due to the presence of endothelial lining and matrix metalloproteinases (MMPs)-mediated aneurysm progression. This study incorporated doxycycline (DOX), a well-known sclerosant and MMPs inhibitor, into a shear-thinning biomaterial (STB)-based vascular embolizing hydrogel. The addition of DOX was expected to improve embolizing efficacy while preventing endoleaks by inhibiting MMP activity and promoting endothelial removal. The results showed that STBs containing 4.5% w/w silicate nanoplatelet and 0.3% w/v of DOX were injectable and had a 2-fold increase in storage modulus compared to those without DOX. STB-DOX hydrogels also reduced clotting time by 33% compared to untreated blood. The burst release of DOX from the hydrogels showed sclerosing effects after 6 h in an ex vivo pig aorta model. Sustained release of DOX from hydrogels on endothelial cells showed MMP inhibition (ca. an order of magnitude larger than control groups) after 7 days. The hydrogels successfully occluded a patient-derived abdominal aneurysm model at physiological blood pressures and flow rates. The sclerosing and MMP inhibition characteristics in the engineered multifunctional STB-DOX hydrogels may provide promising opportunities for the efficient embolization of aneurysms in blood vessels.

A Polymeric Hydrogel to Eliminate Programmed Death-Ligand 1 for Enhanced Tumor Radio-Immunotherapy

Programmed death-ligand 1 (PD-L1) is a specialized shield on tumor cells that evades the immune system. Even inhibited by PD-L1 antibodies, a cycling process constantly transports PD-L1 from inside to outside of cells, facilitating the renewal and replenishment of PD-L1 on the cancer cell membrane. Herein, we develop a sodium alginate hydrogel consisting of elesclomol-Cu and galactose to induce persistent cuproptosis, leading to the reduction of PD-L1 for radio-immunotherapy of colon tumors. First, a prefabricated hydrogel is synthesized by immobilizing elesclomol onto a sodium alginate saccharide chain through the coordination with bivalent copper ions (Cu2+), followed by incorporation of galactose. After implantation into the tumors, this prefabricated hydrogel can be further cross-linked in the presence of physiological calcium ions (Ca2+), resulting in the formation of a hydrogel with controlled release of elesclomol-Cu2+ (ES-Cu) and galactose. The hydrogel effectively induces the oligomerization of DLAT and cuproptosis in colorectal cancer cells. Interestingly, radiation-induced PD-L1 upregulation is abrogated in the presence of the hydrogel, releasing ES-Cu and galactose. Consequently, the sensitization of tumor to radiotherapy and immunotherapy is significantly improved, further prolonging the survival of tumor-bearing mice in both local and metastatic tumors. Our study introduces an approach that combines cuproptosis with immunotherapy and radiotherapy.

Preshaped 4D Photocurable Ultratough Organogel Microcoils for Personalized Endovascular Embolization

Endovascular embolization using microcoils can be an effective technique to treat artery aneurysms. However, microcoils with fixed designs are difficult to adapt to all aneurysm types. In this paper, a photocurable ultratough shape memory organogel with a curing time of only 2 s and megapascal-level mechanical properties is proposed. Then, it is used to manufacture the personalized 4D microcoil with a wire diameter of only 0.3 mm. The improved mechanical modulus (511.63 MPa) can reduce the possibility of microcoils' fracture during embolization. Besides, the fast body-temperature-triggering shape memory ability makes the 4D microcoil applicable in vivo. These 4D microcoils are finally delivered into the rabbit, and successfully blocked the blood flow inside different aneurysms, with neoendothelial cells and collagen fibers growing on the microcoil surface snugly, indicating full aneurysm recovery. This 4D organogel microcoil can potentially be used in personalized clinical translation on human beings.

Progress and future prospects of hemostatic materials based on nanostructured clay minerals

The occurrence of uncontrolled hemorrhage is a significant threat to human life and health. Although hemostatic materials have made remarkable advances in the biomaterials field, it remains a challenge to develop safe and effective hemostatic materials for global medical use. Natural clay minerals (CMs) have long been used as traditional inorganic hemostatic agents due to their good hemostatic capability, biocompatibility and easy availability. With the advancement of science, technology and ideology, CM-based hemostatic materials have undergone continuous innovations by integrating new inspirations with conventional concepts. This review systematically summarizes the hemostatic mechanisms of different natural CMs based on their nanostructures. Moreover, it also comprehensively reviews the latest research progress for CM-based hemostatic hybrid and nanocomposite materials, and discusses the challenges and developments in this field.

Alkaline shear-thinning micro-nanocomposite hydrogels initiate endogenous TGFβ signaling for in situ bone regeneration

Recruiting endogenous stem cells to bone defects without stem cell transplantation and exogenous factor delivery represents a promising strategy for bone regeneration. Herein, we develop an alkaline shear-thinning micro-nanocomposite hydrogel (10-MmN), aiming to alkaline-activate endogenous TGFβ1 and achieve in situ bone regeneration. It contains polyethyleneimine (PEI)-modified gelatin, laponite nanoplatelets (LAP), a bicarbonate buffer with a pH of 10, and gelatin microspheres (MSs). PEI-modified gelatin plays a pivotal role in hydrogel fabrication. It endows the system with sufficient positive charges, and forms a shear-thinning nanocomposite matrix in the pH 10 buffer (10-mN) with negatively charged LAP via electrostatic gelation. For biological functions, the pH 10 buffer dominates alkaline activation of endogenous serum TGFβ1 to recruit rat bone marrow stem cells through the Smad pathway, followed by improved osteogenic differentiation. In addition, MSs are incorporated into 10-mN to form 10-MmN, and function as substrates to provide good attachment sites for the recruited stem cells and facilitate further their osteogenic differentiation. In a rat critical-sized calvarial defect model, 10-MmN exhibits excellent biocompatibility, biodegradability, hydrogel infusion and retention in bone defects with flexible shapes and active bleeding. Importantly, it repairs ~95% of the defect areas in 3 months by recruiting TGFβR2+ and CD90+CD146+ stem cells, and promoting cell proliferation, osteogenic differentiation and bone formation. The present study provides a biomaterial-based strategy to regulate alkalinity in bone defects for the initiation of endogenous TGFβ signaling, which can be extended to treat other diseases.

A Drug-Eluting Injectable NanoGel for Localized Delivery of Anticancer Drugs to Solid Tumors

Systemically administered chemotherapy reduces the efficiency of the anticancer agent at the target tumor tissue and results in distributed drug to non-target organs, inducing negative side effects commonly associated with chemotherapy and necessitating repeated administration. Injectable hydrogels present themselves as a potential platform for non-invasive local delivery vehicles that can serve as a slow-releasing drug depot that fills tumor vasculature, tissue, or resection cavities. Herein, we have systematically formulated and tested an injectable shear-thinning hydrogel (STH) with a highly manipulable release profile for delivering doxorubicin, a common chemotherapeutic. By detailed characterization of the STH physical properties and degradation and release dynamics, we selected top candidates for testing in cancer models of increasing biomimicry. Two-dimensional cell culture, tumor-on-a-chip, and small animal models were used to demonstrate the high anticancer potential and reduced systemic toxicity of the STH that exhibits long-term (up to 80 days) doxorubicin release profiles for treatment of breast cancer and glioblastoma. The drug-loaded STH injected into tumor tissue was shown to increase overall survival in breast tumor- and glioblastoma-bearing animal models by 50% for 22 days and 25% for 52 days, respectively, showing high potential for localized, less frequent treatment of oncologic disease with reduced dosage requirements.

Gelatin methacryloyl and Laponite bioink for 3D bioprinted organotypic tumor modeling

Three-dimensional (3D)in vitrotumor models that can capture the pathophysiology of human tumors are essential for cancer biology and drug development. However, simulating the tumor microenvironment is still challenging because it consists of a heterogeneous mixture of various cellular components and biological factors. In this regard, current extracellular matrix (ECM)-mimicking hydrogels used in tumor tissue engineering lack physical interactions that can keep biological factors released by encapsulated cells within the hydrogel and improve paracrine interactions. Here, we developed a nanoengineered ion-covalent cross-linkable bioink to construct 3D bioprinted organotypic tumor models. The bioink was designed to implement the tumor ECM by creating an interpenetrating network composed of gelatin methacryloyl (GelMA), a light cross-linkable polymer, and synthetic nanosilicate (Laponite) that exhibits a unique ionic charge to improve retention of biological factors released by the encapsulated cells and assist in paracrine signals. The physical properties related to printability were evaluated to analyze the effect of Laponite hydrogel on bioink. Low GelMA (5%) with high Laponite (2.5%-3.5%) composite hydrogels and high GelMA (10%) with low Laponite (1.0%-2.0%) composite hydrogels showed acceptable mechanical properties for 3D printing. However, a low GelMA composite hydrogel with a high Laponite content could not provide acceptable cell viability. Fluorescent cell labeling studies showed that as the proportion of Laponite increased, the cells became more aggregated to form larger 3D tumor structures. Reverse transcription-polymerase chain reaction (RT-qPCR) and western blot experiments showed that an increase in the Laponite ratio induces upregulation of growth factor and tissue remodeling-related genes and proteins in tumor cells. In contrast, cell cycle and proliferation-related genes were downregulated. On the other hand, concerning fibroblasts, the increase in the Laponite ratio indicated an overall upregulation of the mesenchymal phenotype-related genes and proteins. Our study may provide a rationale for using Laponite-based hydrogels in 3D cancer modeling.

Swarming self-adhesive microgels enabled aneurysm on-demand embolization in physiological blood flow

The recent rise of swarming microrobotics offers great promise in the revolution of minimally invasive embolization procedure for treating aneurysm. However, targeted embolization treatment of aneurysm using microrobots has significant challenges in the delivery capability and filling controllability. Here, we develop an interventional catheterization-integrated swarming microrobotic platform for aneurysm on-demand embolization in physiological blood flow. A pH-responsive self-healing hydrogel doped with magnetic and imaging agents is developed as the embolic microgels, which enables long-term self-adhesion under biological condition in a controllable manner. The embolization strategy is initiated by catheter-assisted deployment of swarming microgels, followed by the application of external magnetic field for targeted aggregation of microrobots into aneurysm sac under the real-time guidance of ultrasound and fluoroscopy imaging. Mild acidic stimulus is applied to trigger the welding of microgels with satisfactory bio-/hemocompatibility and physical stability and realize complete embolization. Our work presents a promising connection between the design and control of microrobotic swarms toward practical applications in dynamic environments.

Liquid Embolic Agents for Endovascular Embolization: A Review

Endovascular embolization (EE) has been used for the treatment of blood vessel abnormalities, including aneurysms, AVMs, tumors, etc. The aim of this process is to occlude the affected vessel using biocompatible embolic agents. Two types of embolic agents, solid and liquid, are used for endovascular embolization. Liquid embolic agents are usually injectable and delivered into the vascular malformation sites using a catheter guided by X-ray imaging (i.e., angiography). After injection, the liquid embolic agent transforms into a solid implant in situ based on a variety of mechanisms, including polymerization, precipitation, and cross-linking, through ionic or thermal process. Until now, several polymers have been designed successfully for the development of liquid embolic agents. Both natural and synthetic polymers have been used for this purpose. In this review, we discuss embolization procedures with liquid embolic agents in different clinical applications, as well as in pre-clinical research studies.

Photomodulated Extrusion as a Localized Endovascular Hydrogel Deposition Method

Minimally invasive endovascular embolization is used to treat a wide range of diseases in neurology, oncology, and trauma where the vascular morphologies and corresponding hemodynamics vary greatly. Current techniques based on metallic coils, flow diverters, liquid embolics, and suspended microspheres are limited in their ability to address a wide variety of vasculature and can be plagued by complications including distal migration, compaction, and inappropriate vascular remodeling. Further, these endovascular devices currently offer limited therapeutic functions beyond flow control such as drug delivery. Herein, a novel in situ microcatheter-based photomodulated extrusion approach capable of dynamically tuning the physical and morphological properties of injectable hydrogels, optimizing for local hemodynamic environment and vascular morphology, is proposed and demonstrated. A shear thinning and photoactivated poly(ethylene glycol diacrylate)-nanosilicate (PEGDA-nSi) hydrogel is used to demonstrate multiple extrusion modes which are controlled by photokinetics and device configurations. Real-time photomodulation of injected hydrogel viscosity and modulus is successfully used for embolization in various vasculatures, including high-flow large vessels and arterial-to-arterial capillary shunts. Furthermore, a generalizable therapeutic delivery platform is proposed by demonstrating a core-shell structured extrusion encapsulating doxorubicin to achieve a more sustained release compared to unencapsulated payload.

Tissue adhesive hemostatic microneedle arrays for rapid hemorrhage treatment

Blood loss by hemorrhaging wounds accounts for over one-third of ∼5 million trauma fatalities worldwide every year. If not controlled in a timely manner, exsanguination can take lives within a few minutes. Developing new biomaterials that are easy to use by non-expert patients and promote rapid blood coagulation is an unmet medical need. Here, biocompatible, and biodegradable microneedle arrays (MNAs) based on gelatin methacryloyl (GelMA) biomaterial hybridized with silicate nanoplatelets (SNs) are developed for hemorrhage control. The SNs render the MNAs hemostatic, while the needle-shaped structure increases the contact area with blood, synergistically accelerating the clotting time from 11.5 min to 1.3 min in vitro. The engineered MNAs reduce bleeding by ∼92% compared with the untreated injury group in a rat liver bleeding model. SN-containing MNAs outperform the hemostatic effect of needle-free patches and a commercial hemostat in vivo via combining micro- and nanoengineered features. Furthermore, the tissue adhesive properties and mechanical interlocking support the suitability of MNAs for wound closure applications. These hemostatic MNAs may enable rapid hemorrhage control, particularly for patients in developing countries or remote areas with limited or no immediate access to hospitals.

Thermoresponsive shear-thinning hydrogel (T-STH) hemostats for minimally invasive treatment of external hemorrhages

Hemorrhage is the leading cause of death following battlefield injuries. Although several hemostats are commercially available, they do not meet all the necessary requirements to stop bleeding in combat injuries. Here, we engineer thermoresponsive shear-thinning hydrogels (T-STH) composed of a thermoresponsive polymer, poly(N-isopropyl acrylamide) (p(NIPAM)), and hemostatic silicate nanodisks, LAPONITE®, as minimally invasive injectable hemostatic agents. Our T-STH is a physiologically stable hydrogel that can be easily injected through a syringe and needle and exhibits rapid mechanical recovery. Additionally, it demonstrates temperature-dependent blood coagulation owing to the phase transition of p(NIPAM). It decreases in vitro blood clotting times over 50% at physiological temperatures compared to room temperature. Furthermore, it significantly prevents blood loss in an ex vivo bleeding model at different blood flow rates (1 mL min^-1 and 5 mL min^-1) by forming a wound plug. More importantly, our T-STH is comparable to a commercially available hemostat, Floseal, in terms of blood loss and blood clotting time in an in vivo rat liver bleeding model. Furthermore, once the hemorrhage is stabilized, our T-STH can be easily removed using a cold saline wash without any rebleeding or leaving any residues. Taken together, our T-STH can be used as a first aid hemostat to treat external hemorrhages in emergency situations.

Material characterization of GPX®: A versatile in situ solidifying embolic platform technology

Endovascular embolization is a minimally invasive procedure during which blood flow to targeted tissues is selectively occluded. The list of clinical indications for embolization continues to expand. Liquid embolic agents are injectable compositions that transition into a solid or semi-solid form when introduced into blood vessels. The mechanism that triggers the liquid-to-solid transition is a key distinguishing feature of liquid embolic agents. GPX is a waterborne liquid embolic agent comprising oppositely charged polyelectrolytes: polyguanidinum and inorganic polyphoshate. In situ solidification is driven by electrostatic condensation of the polyelectrolytes, triggered by ionic strength differentials. We report in vitro characterization of the material properties of GPX, it is in vivo effectiveness in acute animal studies, and its potential for chemoembolization. The viscosity of GPX can be varied over a wide range by adjusting the polyguanidinium MW and/or concentration. Formulation of GPX with either tantalum microparticles (30 wt%) or iodinated radiocontrast agents (300 mgI ml^-1) did not significantly change the flow behavior of GPX; the viscosity was independent of shear rate and remained within a clinically practical range (80-160 cP). Formulation of GPX with doxorubicin substantially increased viscosity at low shear rates and resulted in a power law dependence on shear rate. High contrast and effective vascular occlusion were demonstrated in both swine kidneys and rete mirabile. Contrast from iodinated compounds was temporary, dissipating within hours. The doxorubicin in vitro release profile was linear over 90 days. The results demonstrate that GPX is a versatile liquid embolic platform that can be formulated with a wide range of viscosities injectable at clinically practical flow rates, with either transient or permanent contrast, and that can provide prolonged zero-order delivery of doxorubicin to embolized tissues.

Toxicity and Biocompatibility of Liquid Metals

Recently, room-temperature liquid metals have attracted increasing attention from researchers owing to their excellent material properties. Systematic interpretation of the potential toxicity issues involved is essential for a wide range of applications, especially in the biomedical and healthcare fields. However, even with the exponential growth of related studies, investigation of the toxicological impact and possible hazards of liquid metals to organisms is still in its infancy. This review aims to provide a comprehensive summary of the current frontier of knowledge on liquid metal toxicology and biocompatibility in different environments. Based on recent studies, this review focuses on Ga and Bi-based in different states. It is necessary to evaluate their toxicity considering the rapid increase in research and utilization of such liquid metal composites. Finally, existing challenges are discussed and suggestions are provided for further investigation of liquid metal toxicology to clarify the toxicological mechanisms and strategies are provided to avoid adverse effects. In addition to resolving the doubts of public concern about the toxicity of liquid metals, this review is expected to promote the healthy and sustainable development of liquid metal-based materials and their use in diverse areas, especially those related to health care.

Sodium Phytate-Incorporated Gelatin-Silicate Nanoplatelet Composites for Enhanced Cohesion and Hemostatic Function of Shear-Thinning Biomaterials

Shear-thinning biomaterials (STBs) based on gelatin-silicate nanoplatelets (SNs) are emerging as an alternative to conventional coiling and clipping techniques in the treatment of vascular anomalies. Improvements in the cohesion of STB hydrogels pave the way toward their translational application in minimally invasive therapies such as endovascular embolization repair. In the present study, sodium phytate (Phyt) additives are used to tune the electrostatic network of SNs-gelatin STBs, thereby promoting their mechanical integrity and facilitating injectability through standard catheters. We show that an optimized amount of Phyt enhances storage modulus by approximately one order of magnitude and reduces injection force by ≈58% without compromising biocompatibility and hydrogel wet stability. The Phyt additives are found to decrease the immune responses induced by SNs. In vitro embolization experiments suggest a significantly lower rate of failure in Phyt-incorporated STBs than in control groups. Furthermore, the addition of Phyt leads to accelerated blood coagulation (reduces clotting time by ≈45% compared to controls) due to the contributions of negatively charged phosphate groups, which aid in the prolonged durability of STB in coagulopathic patients. Therefore, the proposed approach is an effective method for the design of robust and injectable STBs for minimally invasive treatment of vascular malformations.

Synthesis of Hydrogels and Their Progress in Environmental Remediation and Antimicrobial Application

As a kind of efficient adsorptive material, hydrogel has a wide application prospect within different fields, owing to its unique 3D network structures composed of polymers. In this paper, different synthetic strategies, crosslinking methods and their corresponding limitations and outstanding contributions of applications in the fields of removing environmental pollutants are reviewed to further provide a prospective view of their applications in water resources sustainability. Furthermore, the applications within the biomedical field, especially in wound dressing, are also reviewed in this paper, mainly due to their unique water retention ability, antibacterial ability, and good biocompatibility. Finally, the development direction of hydrogels in the fields of environmental remediation and biomedicine were summarized and prospected.

Photosensitive Hydrogel-Based Embolic Agent Treatment of Wide-Necked Aneurysms: Preliminary Animal Results

Background: The endovascular treatment of cerebral aneurysms has become widespread but may still be limited by recurrence rates or complications. The discovery of novel embolic strategies may help mitigate these concerns. Methods: We formulated a Photosensitive Hydrogel Polymer (PHP) embolic agent which is low-viscosity, shear-thinning, and radio-opaque. After the filling of an aneurysm with PHP with balloon assistance, we utilized photopolymerization to induce solidification. Different methods of light delivery for photopolymerization were assessed in silicone models of aneurysms and in four acute animal trials with venous anastomosis aneurysms in pigs. Then, balloon-assisted embolization with PHP and photopolymerization was performed in three aneurysms in pigs with a one-month follow-up. Filling volume, recurrence rates, and complications were recorded. Results: The PHP was found to be suitable for the intravascular delivery and treatment of cerebral aneurysms. It was found that light delivery through the balloon catheter, as opposed to light delivery through the injection microcatheter, led to higher rates of filling in the 3D model and acute animal model for cerebral aneurysms. Using the balloon-assisted embolization and light delivery strategy, three wide-necked aneurysms were treated without complication. One-month follow-up showed no recurrence or neck remnants. Conclusions: We demonstrated a novel method of balloon-assisted photosensitive hydrogel polymer embolization and photopolymerization, leading to complete aneurysm filling with no recurrence at 1 month in three wide-necked aneurysms in pigs. This promising methodology will be investigated further with longer-term comparative animal trials.