Synergistic control of mechanics and microarchitecture of 3D bioactive hydrogel platform to promote the regenerative potential of engineered hepatic tissue

3D printing incorporating gold nanozymes with mesenchymal stem cell-derived hepatic spheroids for acute liver failure treatment

Acute liver failure (ALF) is a highly fatal disease, necessitating the advancement and optimization of alternative therapeutic strategies to benefit patients awaiting liver transplantation. In this study, we innovatively established the antioxidant nanozyme-hepatocyte-like cells (HLCs) microtissue sheets (HS/N-Au@composite) for ALF therapy. We first prepared a 3D-printed hyaluronic acid/gelatin/sodium alginate scaffold with N-acetylcysteine (NAC)-capped gold nanoclusters (NAC-Au NCs), forming the N-Au@hydrogel. For the encapsulation of HLC spheroids, we used a biocompatible hybrid hydrogel composed of decellularized extracellular matrix (dECM), thrombin, and fibrinogen, resulting in the HS@dECM hydrogel. Utilizing 3D printing technology, we integrated the N-Au@hydrogel with the HS@dECM hydrogel to create the HS/N-Au@composite for in situ transplantation to treat ALF. Our results demonstrated that NAC-Au NCs effectively mitigated reactive oxygen species (ROS)-induced liver necrosis in ALF. Additionally, the N-Au@hydrogel provided mechanical support, ensuring the proper landing and effective functioning of the transplanted HLC spheroids. The HS/N-Au@composite synergistically decreased serum transaminase levels, reduced the accumulation of pro-inflammatory cytokines, accelerated liver function recovery, and promoted liver regeneration in ALF treatment. This combination of HLC spheroids and NAC-Au NCs nanozymes via 3D-printed composite scaffolds represents a promising strategy for enhancing hepatocyte transplantation and advancing stem cell regenerative medicine in ALF therapy.

Bioactive Microgels with Tunable Microenvironment as a 3D Platform to Guide the Complex Physiology of Hepatocellular Carcinoma Spheroids

Miniaturized three-dimensional tissue models, such as spheroids, have become a highly useful and efficient platform to investigate tumor physiology and explore the effect of chemotherapeutic efficacy over traditional two-dimensional monolayer culture, since they can provide more in-depth analysis, especially in regards to intercellular interactions and diffusion. The development of most tumor spheroids relies on the high proliferative capacity and self-aggregation behavior of tumor cells. However, it often disregards the effect of microenvironmental factors mediated by extracellular matrix, which are indispensable components of tissue structure. In this study, hepatocellular carcinoma (HCC) cells are encapsulated in bioactive microgels consisting of gelatin and hyaluronic acid designed to emulate tumor microenvironment in order to induce hepatic tumor spheroid formation. Two different subtypes of HCC's, HepG2 and Hep3B cell lines, are explored. The physicomechanical and biochemical properties of the microgels, controlled by changing the crosslinking density and polymer composition, are clearly shown to have substantial influence over the formation and spheroid formation. Moreover, the spheroids made from different cells and microgel properties display highly variable chemoresistance effects, further highlighting the importance of microenvironmental factors guiding tumor spheroid physiology.

Multiscale Control of Nanofiber-Composite Hydrogel for Complex 3D Cell Culture by Extracellular Matrix Composition and Nanofiber Alignment

In order to manipulate the complex behavior of cells in a 3-dimensional (3D) environment, it is important to provide the microenvironment that can accurately portray the complexity of highly anisotropic tissue structures. However, it is technically challenging to generate a complex microenvironment using conventional biomaterials that are mostly isotropic with limited bioactivity. In this study, the gelatin-hyaluronic acid hydrogel incorporated with aqueous-dispersible, short nanofibers capable of in situ alignment is developed to emulate the native heterogeneous extracellular matrix consisting of fibrous and non-fibrous components. The gelatin nanofibers containing magnetic nanoparticles, which could be aligned by external magnetic field, are dispersed and embedded in gelatin-hyaluronic acid hydrogel encapsulated with dermal fibroblasts. The aligned nanofibers via magnetic field could be safely integrated into the hydrogel, and the process could be repeated to generate larger 3D hydrogels with variable nanofiber alignments. The aligned nanofibers in the hydrogel can more effectively guide the anisotropic morphology (e.g., elongation) of dermal fibroblasts than random nanofibers, whereas myofibroblastic differentiation is more prominent in random nanofibers. At a given nanofiber configuration, the hydrogel composition having intermediate hyaluronic acid content induces myofibroblastic differentiation. These results indicate that modulating the degree of nanofiber alignment and the hyaluronic acid content of the hydrogel are crucial factors that critically influence the fibroblast phenotypes. The nanofiber-composite hydrogel capable of directional nanofiber alignment and tunable material composition can effectively induce a wide array of phenotypic plasticity in 3D cell culture.

Advancements and Challenges in Hydrogel Engineering for Regenerative Medicine

This manuscript covers the latest advancements and persisting challenges in the domain of tissue engineering, with a focus on the development and engineering of hydrogel scaffolds. It highlights the critical role of these scaffolds in emulating the native tissue environment, thereby providing a supportive matrix for cell growth, tissue integration, and reducing adverse reactions. Despite significant progress, this manuscript emphasizes the ongoing struggle to achieve an optimal balance between biocompatibility, biodegradability, and mechanical stability, crucial for clinical success. It also explores the integration of cutting-edge technologies like 3D bioprinting and biofabrication in constructing complex tissue structures, alongside innovative materials and techniques aimed at enhancing tissue growth and functionality. Through a detailed examination of these efforts, the manuscript sheds light on the potential of hydrogels in advancing regenerative medicine and the necessity for multidisciplinary collaboration to navigate the challenges ahead.

Emerging Technology of Nanofiber-Composite Hydrogels for Biomedical Applications

Hydrogels and nanofibers have been firmly established as go-to materials for various biomedical applications. They have been mostly utilized separately, rarely together, because of their distinctive attributes and shortcomings. However, the potential benefits of integrating nanofibers with hydrogels to synergistically combine their functionalities while attenuating their drawbacks are increasingly recognized. Compared to other nanocomposite materials, incorporating nanofibers into hydrogel has the distinct advantage of emulating the hierarchical structure of natural extracellular environment needed for cell and tissue culture. The most important technological aspect of developing "nanofiber-composite hydrogel" is generating nanofibers made of various polymers that are cross-linked and short enough to maintain stable dispersion in hydrated environment. In this review, recent research efforts to develop nanofiber-composite hydrogels are presented, with added emphasis on nanofiber processing techniques. Several notable examples of implementing nanofiber-composite hydrogels for biomedical applications are also introduced.

Manipulating Physicochemical Properties of Biosensor Platform with Polysuccinimide-Silica Nanocomposite for Enhanced Protein Detection

As point-of-care testing (POCT) is becoming the new paradigm of medical diagnostics, there is a growing need to develop reliable POCT devices that can be conveniently operated in a minimally invasive manner. However, the clinical potential of POCT diagnostics is yet to be realized, mainly due to the limited and inconsistent amount of collected samples on these devices, undermining their accuracy. This study proposes a new biosensing platform modified with a functional polysuccinimide (PSI)-silica nanoparticle (SNP) composite system that can substantially increase the protein conjugation efficiency by modulating physicochemical interaction with proteins by several hundred percent from an unmodified device. The efficacy of this PSI-SNP system is further validated by applying it on the surface of a microneedle array (MN), which has emerged as a promising POCT device capable of accessing interstitial fluid through minimal penetration of the skin. This PSI-SNP MN is demonstrated to detect a wide array of proteins with high sensitivity on par with conventional whole serum analysis, validated by in vivo animal testing, effectively displaying broad applicability in biomedical engineering.

Celery-derived scaffolds with liver lobule-mimicking structures for tissue engineering transplantation

Decellularized scaffolds have a demonstrated value in liver tissue engineering. Challenges in this area are focused on effectively eliminating the biological rejection of scaffolds and finding a suitable liver cell source. Here, inspired by the natural microstructure of hepatic lobules, we present a novel decellularized celery-derived scaffold cultured with human-induced pluripotent stem cell-derived hepatocytes (hiPSC-Heps) bioengineering liver tissue construction. Because of the natural hollow channels, interconnected porous structures, and excellent physicochemical characterization of the decellularized celery-derived scaffold, the resultant bioengineering liver tissue can maintain the hiPSC-Heps viability and the hepatic functions in the in vitro cultures. Based on this bioengineering liver tissue, we have demonstrated its good biocompatibility and the significantly higher expressions of albumin (ALB) and periodic acid-schiff stain (PAS) when it was implanted in nude mice. These remarkable properties endow the hiPSC-Heps integrated decellularized celery scaffolds system with promising prospects in the field of liver transplantation and other regeneration medicine.

Automatic Multi-functional Integration Program (AMFIP) towards all-optical mechano-electrophysiology interrogation

Automatic operations of multi-functional and time-lapse live-cell imaging are necessary for the biomedical science community to study active, multi-faceted, and long-term biological phenomena. To achieve automatic control, most existing solutions often require the purchase of extra software programs and hardware that rely on the manufacturers’ own specifications. However, these software programs are usually non-user-programmable and unaffordable for many laboratories. To address this unmet need, we have developed a novel open-source software program, titled Automatic Multi-functional Integration Program (AMFIP), as a new Java-based and hardware-independent system that provides proven advantages over existing alternatives to the scientific community. Without extra hardware, AMFIP enables the functional synchronization of the μManager software platform, the Nikon NIS-Elements platform, and other 3rd party software to achieve automatic operations of most commercially available microscopy systems, including but not limited to those from Nikon. AMFIP provides a user-friendly and programmable graphical user interface (GUI), opening the door to expanding the customizability for myriad hardware and software systems according to user-specific experimental requirements and environments. To validate the intended purposes of developing AMFIP, we applied it to elucidate the question whether single cells, prior to their full spreading, can sense and respond to a soft solid substrate, and if so, how does the interaction depend on the cell spreading time and the stiffness of the substrate. Using a CRISPR/Cas9-engineered human epithelial Beas2B (B2B) cell line that expresses mNeonGreen2-tagged mechanosensitive Yes-associated protein (YAP), we show that single B2B cells develop distinct substrate-stiffness-dependent YAP expressions within 10 hours at most on the substrate, suggesting that cells are able to sense, distinguish, and respond to mechanical cues prior to the establishment of full cell spreading. In summary, AMFIP provides a reliable, open-source, and cost-free solution that has the validated long-term utility to satisfy the need of automatic imaging operations in the scientific community.

Induced Endothelial Cell-Integrated Liver Assembloids Promote Hepatic Maturation and Therapeutic Effect on Cholestatic Liver Fibrosis

The transplantation of pluripotent stem cell (PSC)-derived liver organoids has been studied to solve the current donor shortage. However, the differentiation of unintended cell populations, difficulty in generating multi-lineage organoids, and tumorigenicity of PSC-derived organoids are challenges. However, direct conversion technology has allowed for the generation lineage-restricted induced stem cells from somatic cells bypassing the pluripotent state, thereby eliminating tumorigenic risks. Here, liver assembloids (iHEAs) were generated by integrating induced endothelial cells (iECs) into the liver organoids (iHLOs) generated with induced hepatic stem cells (iHepSCs). Liver assembloids showed enhanced functional maturity compared to iHLOs in vitro and improved therapeutic effects on cholestatic liver fibrosis animals in vivo. Mechanistically, FN1 expressed from iECs led to the upregulation of Itgα5/β1 and Hnf4α in iHEAs and were correlated to the decreased expression of genes related to hepatic stellate cell activation such as Lox and Spp1 in the cholestatic liver fibrosis animals. In conclusion, our study demonstrates the possibility of generating transplantable iHEAs with directly converted cells, and our results evidence that integrating iECs allows iHEAs to have enhanced hepatic maturation compared to iHLOs.

Towards an integrative understanding of cancer mechanobiology: calcium, YAP, and microRNA under biophysical forces

An increasing number of studies have demonstrated the significant roles of the interplay between microenvironmental mechanics in tissues and biochemical-genetic activities in resident tumor cells at different stages of tumor progression. Mediated by molecular mechano-sensors or -transducers, biomechanical cues in tissue microenvironments are transmitted into the tumor cells and regulate biochemical responses and gene expression through mechanotransduction processes. However, the molecular interplay between the mechanotransduction processes and intracellular biochemical signaling pathways remains elusive. This paper reviews the recent advances in understanding the crosstalk between biomechanical cues and three critical biochemical effectors during tumor progression: calcium ions (Ca²⁺), yes-associated protein (YAP), and microRNAs (miRNAs). We address the molecular mechanisms underpinning the interplay between the mechanotransduction pathways and each of the three effectors. Furthermore, we discuss the functional interactions among the three effectors in the context of soft matter and mechanobiology. We conclude by proposing future directions on studying the tumor mechanobiology that can employ Ca²⁺, YAP, and miRNAs as novel strategies for cancer mechanotheraputics. This framework has the potential to bring insights into the development of novel next-generation cancer therapies to suppress and treat tumors.

Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity

Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties (e.g., stiffness, pore size, viscoelasticity, microarchitecture, degradability, ligand presentation, stimulus-responsive properties, etc.) and influence cell signaling cascades and fate. In the past few decades, a plethora of pioneering studies have been implemented to explore the cell-hydrogel matrix interactions and figure out the underlying mechanisms, paving the way to the lab-to-clinic translation of hydrogel-based therapies. In this review, we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely. Subsequently, the comprehensive description and deep discussion were elucidated, wherein the influences of different hydrogels properties on cell behaviors and cellular signaling events were highlighted. These behaviors or events included integrin clustering, focal adhesion (FA) complex accumulation and activation, cytoskeleton rearrangement, protein cyto-nuclei shuttling and activation (e.g., Yes-associated protein (YAP), catenin, etc.), cellular compartment reorganization, gene expression, and further cell biology modulation (e.g., spreading, migration, proliferation, lineage commitment, etc.). Based on them, current in vitro and in vivo hydrogel applications that mainly covered diseases models, various cell delivery protocols for tissue regeneration and disease therapy, smart drug carrier, bioimaging, biosensor, and conductive wearable/implantable biodevices, etc. were further summarized and discussed. More significantly, the clinical translation potential and trials of hydrogels were presented, accompanied with which the remaining challenges and future perspectives in this field were emphasized. Collectively, the comprehensive and deep insights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes, which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.

Mechanotopography-Driven Design of Dispersible Nanofiber-Laden Hydrogel as a 3D Cell Culture Platform for Investigating Tissue Fibrosis

Fibrosis is one of the most frequent occurrences during one's lifetime, identified by various physiological changes including, most notably, excessive deposition of extracellular matrix (ECM). Despite its physiological importance, it is still a significant challenge to conduct a systematic investigation of tissue fibrosis, mainly due to the lack of in vitro 3D tissue model that can accurately portray the characteristic features of fibrotic events. Herein, a hybrid hydrogel system incorporating dispersible nanofibers is developed to emulate highly collagenous deposits formed within a fibrotic tissue leading to altered mechanotopographical properties. Micrometer-length, aqueous-stable nanofibers consisting of crosslinked gelatin network embedded with graphene oxide (GO) or reduced graphene (rGO) are infused into hydrogel, resulting in controllable mechanotopographical properties while maintaining permeability sufficiently enough for various cellular activities. Ultimately, the ability to induce fibrotic behavior of fibroblasts cultured in these mechanotopography-controlled, nanofiber-laden hydrogels is investigated in detail.

3D Cell Culture: Recent Development in Materials with Tunable Stiffness

It is widely accepted that three-dimensional cell culture systems simulate physiological conditions better than traditional 2D systems. Although extracellular matrix components strongly modulate cell behavior, several studies underlined the importance of mechanosensing in the control of different cell functions such as growth, proliferation, differentiation, and migration. Human tissues are characterized by different degrees of stiffness, and various pathologies (e.g., tumor or fibrosis) cause changes in the mechanical properties through the alteration of the extracellular matrix structure. Additionally, these modifications have an impact on disease progression and on therapy response. Hence, the development of platforms whose stiffness could be modulated may improve our knowledge of cell behavior under different mechanical stress stimuli. In this review, we have analyzed the mechanical diversity of healthy and diseased tissues, and we have summarized recently developed materials with a wide range of stiffness.