The Translational Application of Hydrogel for Organoid Technology: Challenges and Future Perspectives

A bioactive calcium silicate nanowire-containing hydrogel for organoid formation and functionalization

Organoids, which are 3D multicellular constructs, have garnered significant attention in recent years. Existing organoid culture methods predominantly utilize natural and synthetic polymeric hydrogels. This study explored the potential of a composite hydrogel mainly consisting of calcium silicate (CS) nanowires and methacrylated gelatin (GelMA) as a substrate for organoid formation and functionalization, specifically for intestinal and liver organoids. Furthermore, the research delved into the mechanisms by which CS nanowires promote the structure formation and development of organoids. It was discovered that CS nanowires can influence the stiffness of the hydrogel, thereby regulating the expression of the mechanosensory factor yes-associated protein (YAP). Additionally, the bioactive ions released by CS nanowires in the culture medium could accelerate Wnt/β-catenin signaling, further stimulating organoid development. Moreover, bioactive ions were found to enhance the nutrient absorption and ATP metabolic activity of intestinal organoids. Overall, the CS/GelMA composite hydrogel proves to be a promising substrate for organoid formation and development. This research suggested that inorganic biomaterials hold significant potential in organoid research, offering bioactivities, biosafety, and cost-effectiveness.

Artificial tumor matrices and bioengineered tools for tumoroid generation

The tumor microenvironment (TME) is critical for tumor growth and metastasis. The TME contains cancer-associated cells, tumor matrix, and tumor secretory factors. The fabrication of artificial tumors, so-called tumoroids, is of great significance for the understanding of tumorigenesis and clinical cancer therapy. The assembly of multiple tumor cells and matrix components through interdisciplinary techniques is necessary for the preparation of various tumoroids. This article discusses current methods for constructing tumoroids (tumor tissue slices and tumor cell co-culture) for pre-clinical use. This article focuses on the artificial matrix materials (natural and synthetic materials) and biofabrication techniques (cell assembly, bioengineered tools, bioprinting, and microfluidic devices) used in tumoroids. This article also points out the shortcomings of current tumoroids and potential solutions. This article aims to promotes the next-generation tumoroids and the potential of them in basic research and clinical application.

Engineered hydrogel reveals contribution of matrix mechanics to esophageal adenocarcinoma and identifies matrix-activated therapeutic targets

Increased extracellular matrix (ECM) stiffness has been implicated in esophageal adenocarcinoma (EAC) progression, metastasis, and resistance to therapy. However, the underlying protumorigenic pathways are yet to be defined. Additional work is needed to develop physiologically relevant in vitro 3D culture models that better recapitulate the human tumor microenvironment and can be used to dissect the contributions of matrix stiffness to EAC pathogenesis. Here, we describe a modular, tumor ECM-mimetic hydrogel platform with tunable mechanical properties, defined presentation of cell-adhesive ligands, and protease-dependent degradation that supports robust in vitro growth and expansion of patient-derived EAC 3D organoids (EAC PDOs). Hydrogel mechanical properties control EAC PDO formation, growth, proliferation, and activation of tumor-associated pathways that elicit stem-like properties in the cancer cells, as highlighted through in vitro and in vivo environments. We also demonstrate that the engineered hydrogel serves as a platform for identifying potential therapeutic targets to disrupt the contribution of protumorigenic matrix mechanics in EAC. Together, these studies show that an engineered PDO culture platform can be used to elucidate underlying matrix-mediated mechanisms of EAC and inform the development of therapeutics that target ECM stiffness in EAC.

Breast cancer organoids derived from patients: A platform for tailored drug screening

Breast cancer stands as the most prevalent and heterogeneous malignancy affecting women globally, posing a substantial health concern. Enhanced comprehension of tumor pathology and the development of novel therapeutics are pivotal for advancing breast cancer treatment. Contemporary breast cancer investigation heavily leans on in vivo models and conventional cell culture techniques. Nonetheless, these approaches often encounter high failure rates in clinical trials due to species disparities and tissue structure variations. To address this, three-dimensional cultivation of organoids, resembling organ-like structures, has emerged as a promising alternative. Organoids represent innovative in vitro models that mirror in vivo tissue microenvironments. They retain the original tumor's diversity and facilitate the expansion of tumor samples from diverse origins, facilitating the representation of varying tumor stages. Optimized breast cancer organoid models, under precise culture conditions, offer benefits including convenient sample acquisition, abbreviated cultivation durations, and genetic stability. These attributes ensure a faithful replication of in vivo traits of breast cancer cells. As intricate cellular entities boasting spatial arrangements, breast cancer organoid models harbor substantial potential in precision medicine, organ transplantation, modeling intricate diseases, gene therapy, and drug innovation. This review delivers an overview of organoid culture techniques and outlines future prospects for organoid modeling.

Lung cancer organoids: models for preclinical research and precision medicine

Lung cancer is a malignancy with high incidence and mortality rates globally, and it has a 5-year survival rate of only 10%-20%. The significant heterogeneity in clinical presentation, histological features, multi-omics findings, and drug sensitivity among different lung cancer patients necessitate the development of personalized treatment strategies. The current precision medicine for lung cancer, primarily based on pathological and genomic multi-omics testing, fails to meet the needs of patients with clinically refractory lung cancer. Lung cancer organoids (LCOs) are derived from tumor cells within tumor tissues and are generated through three-dimensional tissue culture, enabling them to faithfully recapitulate in vivo tumor characteristics and heterogeneity. The establishment of a series of LCOs biobanks offers promising platforms for efficient screening and identification of novel targets for anti-tumor drug discovery. Moreover, LCOs provide supplementary decision-making factors to enhance the current precision medicine for lung cancer, thereby addressing the limitations associated with pathology-guided approaches in managing refractory lung cancer. This article presents a comprehensive review on the construction methods and potential applications of LCOs in both preclinical and clinical research. It highlights the significance of LCOs in biomarker exploration, drug resistance investigation, target identification, clinical precision drug screening, as well as microfluidic technology-based high-throughput drug screening strategies. Additionally, it discusses the current limitations and future prospects of this field.

Peptide Hydrogels and Nanostructures Controlling Biological Machinery

Peptides are versatile building blocks for the fabrication of various nanostructures that result in the formation of hydrogels and nanoparticles. Precise chemical functionalization promotes discrete structure formation, causing controlled bioactivity and physical properties for functional materials development. The conjugation of small molecules on amino acid side chains determines their intermolecular interactions in addition to their intrinsic peptide characteristics. Molecular information affects the peptide structure, formation, and activity. In this Perspective, peptide building blocks, nanostructure formation mechanisms, and the properties of these peptide materials are discussed with the results of recent publications. Bioinstructive and stimuli-responsive peptide materials have immense impacts on the nanomedicine field including drug delivery, cellular engineering, regenerative medicine, and biomedicine.

Hydrogels for Oral Tissue Engineering: Challenges and Opportunities

Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a two-fold approach: fighting bacterial infections and promoting tissue growth. Hydrogels are promising tissue engineering biomaterials that show great potential for oral tissue regeneration and drug delivery. In this review, we present a classification of hydrogels commonly used in dental research, including natural and synthetic hydrogels. Furthermore, recent applications of these hydrogels in endodontic restorations, periodontal tissues, mandibular and oral soft tissue restorations, and related clinical studies are also discussed, including various antimicrobial and tissue growth promotion strategies used in the dental applications of hydrogels. While hydrogels have been increasingly studied in oral tissue engineering, there are still some challenges that need to be addressed for satisfactory clinical outcomes. This paper summarizes the current issues in the abovementioned application areas and discusses possible future developments.

A Nanoclay-Enhanced Hydrogel for Self-Adhesive Wearable Electrophysiology Electrodes with High Sensitivity and Stability

Hydrogel-based wet electrodes are the most important biosensors for electromyography (EMG), electrocardiogram (ECG), and electroencephalography (EEG); but, are limited by poor strength and weak adhesion. Herein, a new nanoclay-enhanced hydrogel (NEH) has been reported, which can be fabricated simply by dispersing nanoclay sheets (Laponite XLS) into the precursor solution (containing acrylamide, N, N'-Methylenebisacrylamide, ammonium persulfate, sodium chloride, glycerin) and then thermo-polymerizing at 40 °C for 2 h. This NEH, with a double-crosslinked network, has nanoclay-enhanced strength and self-adhesion for wet electrodes with excellent long-term stability of electrophysiology signals. First of all, among existing hydrogels for biological electrodes, this NEH has outstanding mechanical performance (93 kPa of tensile strength and 1326% of breaking elongation) and adhesion (14 kPa of adhesive force), owing to the double-crosslinked network of the NEH and the composited nanoclay, respectively. Furthermore, this NEH can still maintain a good water-retaining property (it can remain at 65.4% of its weight after 24 h at 40 °C and 10% humidity) for excellent long-term stability of signals, on account of the glycerin in the NEH. In the stability test of skin-electrode impedance at the forearm, the impedance of the NEH electrode can be stably kept at about 100 kΩ for more than 6 h. As a result, this hydrogel-based electrode can be applied for a wearable self-adhesive monitor to highly sensitively and stably acquire EEG/ECG electrophysiology signals of the human body over a relatively long time. This work provides a promising wearable self-adhesive hydrogel-based electrode for electrophysiology sensing; which, will also inspire the development of new strategies to improve electrophysiological sensors.

Newly developed 3D in vitro models to study tumor-immune interaction

Immunotherapy as a rapidly developing therapeutic approach has revolutionized cancer treatment and revitalized the field of tumor immunology research. 3D in vitro models are emerging as powerful tools considering their feature to maintain tumor cells in a near-native state and have been widely applied in oncology research. The novel 3D culture methods including the co-culture of organoids and immune cells, ALI culture, 3D-microfluidic culture and 3D-bioprinting offer new approaches for tumor immunology study and can be applied in many fields such as personalized treatment, immunotherapy optimizing and adoptive cell therapy. In this review, we introduce commonly used 3D in vitro models and summarize their applications in different aspects of tumor immunology research. We also provide a preliminary analysis of the current shortcomings of these models and the outlook of future development.

Bone tumors effective therapy through functionalized hydrogels: current developments and future expectations

Primary bone tumors especially, sarcomas affect adolescents the most because it originates from osteoblasts cells responsible for bone growth. Chemotherapy, surgery, and radiation therapy are the most often used clinical treatments. Regrettably, surgical resection frequently fails to entirely eradicate the tumor, which is the primary cause of metastasis and postoperative recurrence, leading to a high death rate. Additionally, bone tumors frequently penetrate significant regions of bone, rendering them incapable of self-repair, and impairing patients' quality of life. As a result, treating bone tumors and regenerating bone in the clinic is difficult. In recent decades, numerous sorts of alternative therapy approaches have been investigated due to a lack of approved treatments. Among the novel therapeutic approaches, hydrogel-based anticancer therapy has cleared the way for the development of new targeted techniques for treating bone cancer and bone regeneration. They include strategies such as co-delivery of several drug payloads, enhancing their biodistribution and transport capabilities, normalizing accumulation, and optimizing drug release profiles to decrease the limitations of current therapy. This review discusses current advances in functionalized hydrogels to develop a new technique for treating bone tumors by reducing postoperative tumor recurrence and promoting tissue repair.