Injectable and degradable hydrogel: in vitro drug release behavior and evaluation in a brain repair context.

True regeneration of the pulp-dentine complex is the ultimate goal of regenerative endodontic procedures (REPs). Despite favourable clinical outcomes, such as resolution of apical periodontitis, continued root elongation and apical closure, histological evidence suggests that most clinical cases result in tissue repair rather than true regeneration. This discrepancy arises from the intricate requirements for optimising the microenvironment, which encompasses two essential stages: disinfection and regeneration. These two stages are not necessarily sequential; they can overlap and be highly interconnected, influencing each other. Current REPs protocols have limitations in both disinfection and regeneration. Endodontic biofilms exhibit a notable tolerance to disinfectants and have the capability of recovery, which negatively affects the odontogenic potential of stem cells. Additionally, immune cells, particularly M1 and M2 macrophages, interact with stem cells and affect their regenerative capacity. Standard irrigants and intracanal medicaments often fail to eliminate biofilms, compromising stem cell viability and differentiation potential. On the regeneration side, age-related decline in stem cell function reduces cell survival and differentiation capacity, while insufficient delivery and lack of control over signalling molecules limit odontogenesis, angiogenesis, and neurogenesis. Commonly used scaffolds for REPs lack the structural, biochemical and biological precision required to guide regeneration of well-organised tissue. Furthermore, a microenvironment characterised by hypoxia, restricted nutrients and limited neurovascular ingrowth further constrains regenerative outcomes. This review will focus on the limitations of the current regenerative microenvironment in REPs and discuss emerging strategies aimed at integrating infection control with tissue engineering design. It also highlights the need for novel antimicrobial approaches and advanced tissue engineering strategies in REPs. Multifunctional biomaterials, such as chitosan nanoparticles, antimicrobial peptides and hierarchically structured scaffolds, may ultimately facilitate true biological regeneration of the pulp-dentine complex.

Artificial intelligence in biomaterials for oral oncology.

Hollow Fiber Membrane Bioreactors (HFMBs) support mammalian cell culture at high cell density by enabling effective transport of nutrients, gases and metabolites to/from cells and by offering high membrane surface area-to-bioreactor volume ratios, scalability and flexibility in design. A recent study showed that shell-and-tube HFMBs with cells in the extracapillary space (ECS) for medicine may be designed to mimic the bone architecture for bone tissue engineering (TE). A more transport-efficient HFMB, the BRx-HFMB, consists of a 3D stack of alternating cross-woven mats of microporous and gas-permeable hollow fiber membranes with cells in the ECS and medium flowing inside the membranes. This design was shown to support the culture of a large mass of densely packed cells with high oxygen and nutrient metabolic demands similar to bone cells. Its biomimicry and rationale for good performance are poorly characterized, hindering exploitation of its characteristics for bone TE. Herein, we report the architectural and biomimetic characterization of pore/void distribution in the ECS of laboratory BRx-HFMBs using non-invasive non-destructive micro-computed tomography and advanced image analysis to minimize artifacts. The results suggest that the ECS pore architecture and specific surface area of BRx-HFMBs mimic those of bone tissue, favoring cell migration around, and adhesion on, membranes at clinical cell densities. The membrane network architecture enables cell perfusion with medium, and membranes act as spatially distributed oxygen sources promoting oxygen transport through the cell construct over longer distances than in static bioreactors. This supports the use of BRx-HFMBs to develop cellular models of bone tissue for drug testing and precision medicine.

Female infertility, which affects millions of couples globally, has been a highly focused research field owing to the importance of reproduction in humans. Emerging bioengineering technologies, including tissue engineering, microfluidic chips, imaging techniques, personalized medicine, gene editing tools, and artificial intelligence, have the potential to revolutionize the existing assisted reproductive technology. These technologies have enabled creating artificial biomimetic systems for the culture of oocytes and embryos; changed the way they develop; and enhanced their competence evaluation in an automatic manner. However, the implementation and potential integration of these technologies have been a long-entrenched challenge due to the lack of standardized protocols and precise control over reproductive cycles. This review article summarizes recent advances in these innovative approaches, with an emphasis on tissue engineering and microfluidic technology. Their convergence is discussed as a potential pathway toward more integrated, precise, and personalized reproductive systems for next-generation assisted reproductive technology. In this context, key challenges related to ethics, standardization, cross-technology integration, and clinical translation are further discussed.

Photobiomodulation (PBM) has gained recognition as a promising, non-invasive strategy to enhance the differentiation of adipose-derived stem cells (ADSCs) into smooth muscle cells (SMCs), particularly when used together with a three-dimensional (3D) hydrogel culture system. This review explores the key mechanisms by which PBM modulates cellular behavior, along with its role in the promotion of SMCs lineage commitment in ADSCs. We investigate the influence of various light parameters including wavelength, intensity, energy density, exposure time and duration on cell responses such as proliferation, metabolic activity, gene expression and functional maturation. Moreover, we scrutinize the different hydrogel scaffolds, their compositions and the respective effects on PBM efficacy and consequential cellular outcomes. We also highlight the importance of scaffold design in mimicking the native extracellular matrix and how along with certain mechanical cues, they play a vital role in supporting stem cell behavior. By identifying current challenges, gaps in the literature and proposing future recommendations; this review aims to provide insights into the optimization of PBM protocols to improve SMCs differentiation of ADSCs, ultimately with the intention of integrating PBM to optimize regenerative therapies for use in regenerative medicine and tissue engineering (TE) strategies for vascular conditions and other smooth muscle-related diseases.

Gelatin Methacryloyl (GelMA) hydrogels are widely utilized in biomedical applications due to their biocompatibility and tenable mechanical properties. Traditional methods for measuring stiffness are often destructive, which limits real-time monitoring of critical processes such as swelling and cell growth. Here, Surface Acoustic Wave (SAW) sensing is employed to characterize the mechanical properties of GelMA hydrogels with varying concentrations and degrees of functionalization. GelMA samples were fabricated and subjected to compression testing alongside SAW measurements to assess stiffness via wave attenuation. While mass load affects wave reflection linearly, wave attenuation is an exponential response and the primary influence on stiffness measurements, with SAW sensing yielding greater reproducibility than compression testing. This indicates enhanced reliability and sensitivity in measuring dynamic property changes. Rayleigh-SAW technology has been successfully applied to 3D hydrogels, enabling real-time monitoring of cellular behavior and supporting advances in tissue engineering and other biomedical applications. Overall, SAW sensing offers a promising alternative to traditional mechanical testing, enhancing our ability to analyze complex biological systems.

Hydrogels are high-water-content polymer networks similar to those of soft tissues and have shown immense potential in fields such as tissue engineering, flexible electronics, and intelligent sensors. However, traditional hydrogels still face challenges such as low mechanical strength, poor toughness, and susceptibility to fatigue. Inspired by tough natural soft tissues (such as muscles and tendons), the introduction of a robust fibrous network into hydrogels enables effective stress transfer, crack bridging, and energy dissipation, thus overcoming the mechanical limitations of traditional hydrogels. This paper reviews fiber-reinforced hydrogels prepared from different reinforcing fibers (e.g., natural, synthetic, inorganic, and carbon-based), as well as the interfacial interactions between the fibers and the matrix (including physical entanglement, dynamic noncovalent bonds, and covalent bonds), and summarizes the preparation methods, such as in situ infiltration, directional freezing, and 3D printing. It also discusses their applications in the fields of medicine, sensing, and wearable devices and finally provides an outlook on current challenges such as precise interface regulation and large-scale intelligent manufacturing.

Hydrogels are cross-linked polymeric networks with wide applications in drug delivery, tissue engineering, biosensing, and environmental remediation. These hydrogels additionally host living cells, small molecules, and biological propagules, which further expand the applications of these materials. However, most, if not all, fabrication methods require covalent modifications. In this work, by deliberately selecting polymers with a known propensity to phase separate and formulating compositions far from the binodal boundary, we demonstrate the propensity of the system to transition directly into viscoelastic liquids or gels. This behavior is demonstrated using a model system of poly(ethylene glycol) (PEG) and dextran (DEX). We carried out rheological studies to provide insights into the viscoelastic behavior of these gels. We systematically characterized the gels through colorimetric assays, FTIR, MALDI-TOF, and thermogravimetric analysis (TGA) to discern the molecular compositions and solvent content of the gels. These experimental findings are supplemented with coarse-grained (CG) simulation insights to investigate the mechanistic origins of phase separation propensity with varying molecular weights of DEX. We utilized coexisting densities in the two phases using CG simulations to predict the role of DEX molecular weight in the partitioning of PEG and DEX in the two phases. Finally, we exploit the fabricated gel's ability to encapsulate live cells, antibiotics, and plant seeds. We anticipate that this ATPS-based fabrication technique will provide a scalable, cross-linker-free route to multifunctional gels, enabling advanced applications in drug delivery and responsive materials.

Interpretable neural basis approximation for periodic cellular surfaces through analytic primitive mixtures

Mechanically tunable double-network (DN) hydrogels are emerging as versatile biomaterials for soft tissue engineering, yet achieving precise control over their architecture and mechanics remains challenging. Here, we develop soft ionically crosslinked double-network hydrogels composed of sodium alginate (Alg) and gelatin (Gel) for three-dimensional (3D) skeletal muscle tissue engineering. Calcium ion (Ca2+) crosslinking of the Alg generated entrapped Gel microphases, producing mechanically reinforced hydrogels with interconnected microporous structures. Three compositions of Alg/Gel (Alg:Gel=1:0, 1:0.25, and 1:0.50 w/w) were fabricated, in which increasing Gel content significantly modulated hydrogel properties. The compressive modulus increased from 14.8kPa to 23.7kPa, while the Alg:Gel (1:0.25) formulation exhibited the highest tensile strength of 194kPa. The storage (G') and loss (G") moduli also increase with gelatin incorporation and exhibit maxima of 43.5kPa (G'), and 9.6kPa (G") for Alg/Gel (1:0.50). Developed Alg/Gel hydrogels were explored as bioinks for 3D bioprinting, enabling fabrication of mechanically stable 3D complex structures with high shape fidelity. C2C12 myoblasts encapsulated in 3D bioprinted Alg/Gel hydrogels exhibited robust metabolic activity, cell viability (>90%), and enhanced proliferation. Furthermore, the Alg/Gel hydrogels supported enhanced expression of MyoD, MyoG, myosin heavy chain (MYH), driving efficient myogenic differentiation and formation of multinucleated myotubes. Together, the tunable mechanics, microporosity, viscoelastic relaxation, and gelatin-mediated bioactivity position Alg/Gel double-network hydrogels as a promising bioink platform for 3D bioprinted skeletal muscle regeneration.

Assessing apparent cell stiffness on fibrous substrates: A comparison of numerical-analytical and in silico models with a novel thermo-contraction approach.

A review of functional rare earth metal oxides: synthesis strategies, properties, and emerging applications

Hierarchical scaffolds amalgamating bFGF-immobilized fibrous yarn bundles with cryogel tube for tendon tissue engineering.

The development of biomimetic scaffolds capable of promoting both cartilage and subchondral bone regeneration remains a major challenge in osteochondral tissue engineering. In this study, type I acid-soluble collagen (ASC) was successfully extracted from black flounder (Paralichthys olivaceus) skin and systematically characterized. The purified ASC retained its native triple-helical structure, as confirmed by SDS-PAGE, FTIR, CD, and XRD analyses, and exhibited favorable self-assembly behavior near physiological pH. Based on this natural matrix, photocrosslinkable methacrylated chondroitin sulfate (CSMA) was synthesized and combined with ASC or mineralized collagen (MC) to fabricate injectable composite hydrogels via UV-initiated polymerization. The resulting CSMA/COL and CSMA/MC hydrogels demonstrated tunable gelation times (90-120 s), high porosity, excellent swelling capacity, and superior mechanical strength (compressive modulus up to ∼40 kPa). Rheological analysis revealed stable viscoelastic properties with G' consistently exceeding G″. The composites also exhibited remarkable self-healing ability. In vitro, all hydrogel extracts displayed outstanding cytocompatibility, promoting primary chondrocyte adhesion, proliferation, and migration. Hydrogels containing collagen and MC (especially CS5M1) significantly enhanced the alkaline phosphatase (ALP) activity and upregulated chondrogenic gene expression (COL II, Acan, and Sox9). In vivo implantation in a rat full-thickness cartilage defect model demonstrated that CSMA-based composite hydrogels facilitated seamless defect filling, enhanced proteoglycan and glycosaminoglycan deposition, and promoted subchondral bone remodeling. Among all formulations, CS5M1 achieved the most complete repair, regenerating hyaline-like cartilage integrated with surrounding tissue after 12 weeks. Collectively, these results demonstrate that the composite hydrogels provide a biomimetic, injectable, and photo-curable platform with excellent osteochondral regenerative potential.

The p75NTR/Mdm2 signaling axis promotes odontogenic differentiation and mineralization in ectomesenchymal stem cells.

Iron overload cardiomyopathy (IOC) is caused by elevated systemic iron, and it is characterized by systolic and diastolic dysfunction as well as arrhythmias. Isolating the cardiac-specific cellular and molecular mechanisms driving IOC has been challenging because it affects multiple interconnected organ systems. Here, we leverage stem cells, cardiac tissue engineering, and protein reconstitution to model key contractile aspects of human IOC in vitro and probe the cellular and molecular mechanisms driving cardiac dysfunction. Human-engineered heart tissues consisting of both cardiomyocytes and cardiac fibroblasts faithfully recapitulate key aspects of the human disease, including reduced contractile function, impaired relaxation, and increased prevalence of arrhythmogenic events. While both cardiomyocytes and cardiac fibroblasts show increased intracellular iron levels, cardiomyocytes show higher iron accumulation and reactive oxygen species production. Moreover, iron overload has little effect on the action potential kinetics in engineered heart tissues; however, it impacts the kinetics of the calcium transient, potentially driving arrhythmogenesis. Finally, iron overload decreases force production, in part, through oxidative damage of sarcomeric proteins and iron-based inhibition of myosin. Our results reveal insights into the cellular and molecular mechanisms of human IOC pathogenesis and establish in vitro models that can be harnessed for mechanistic and translational studies.

Hydrogels are an attractive biomaterial for use in soft tissue engineering applications but fall short when used in large volume applications, exhibiting limited cellular infiltration and exaggerated fibrotic capsule responses. Embedding microgels within bulk hydrogels to generate microporosity enables greater cellular infiltration and provides more control over cell fate. Microgels can be further encapsulated with therapeutics to provide bioactive cues to the surrounding local microenvironment, synergistically complementing their intrinsic physical properties. MCC950, a NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome inhibitor, has been previously shown to selectively halt foreign body driven inflammation while preserving inflammation beneficial to minimizing the fibrotic capsule response and promoting tissue repair within implanted biomaterials. Here, we fabricated a silk fibroin-based hydrogel construct composed of MCC950-encapsulated microgels encased within a bulk hydrogel filler. While the encapsulation of MCC950 into silk constructs resulted in few changes in mechanical properties, the eluted drug retained bioactivity in vitro against human THP-1 cells. In vivo implantation of MCC950-encapsulated microgel-hydrogel constructs in a subcutaneous mouse model over 2 weeks showed synergistic effects between the physical and biological cues, resulting in a decrease in fibrous capsule formation and increase in cellular infiltration, attributed to the decrease in NLRP3 expression around the scaffold. Together, these results demonstrate the potential of MCC950-encapsulated silk microgel-hydrogel constructs for soft tissue engineering applications. Furthermore, these findings highlight a synergistic interplay between targeted NLRP3 inhibition and the microporous scaffold architecture that collectively drives reduced fibrosis and a more pro-regenerative immune microenvironment conducive to positive tissue remodeling. STATEMENT OF SIGNIFICANCE: Hydrogels are promising for soft tissue engineering but often lack cell infiltration at larger volumes. Embedding microgels within bulk hydrogels creates a microporous structure that enhances cellular infiltration. Therapeutics can also be encapsulated to provide bioactive cues to synergistically complement the physical architecture. In this study, silk-based microgel-hydrogel constructs were encapsulated with MCC950, a selective immunomodulatory drug, to minimize the fibrotic response and promoting tissue repair. Scaffolds were optimized for mechanical strength, drug release with eluted MCC950 retaining bioactivity against human THP-1 cells. 2-week mouse subcutaneous implantations demonstrated effects between architectural and bioactive cues, decreasing capsule thickness and increasing cell infiltration. These findings highlight the synergistic between physical and bioactive cues towards creating a pro-regenerative microenvironment conducive to tissue remodeling.

This study aimed to evaluate osteogenesis on the surface of three-dimensional (3D)-printed titanium (Ti). For this reason, mesenchymal stem cells (MSC) and osteoblastic-like cells cultures (Saos-2) were plated on 3D-printed Ti for up to 17 days. The following parameters were evaluated: 1) cell morphology; 2) cell viability and proliferation; 3) runt-related transcription factor-2 (RUNX2), type I collagen (COL I), osteopontin (OPN), bone sialoprotein (BSP), and osteocalcin (OC) gene expression; 4) COL I quantification; 5) alkaline phosphatase (ALP) activity, and 6) extracellular matrix (ECM) mineralization. Machined Ti samples were used as control. The data were analyzed statistically, considering a significant level of 5%. The findings of the study revealed that the surface characteristics of 3D-printed Ti allowed adhesion and proliferation of MSC and Saos-2 similarly as observed for both cultures grown on Machined Ti (p>0.05). However, Saos-2 cultured on 3D-printed Ti exhibited significantly higher ALP activity (p<0.05), whereas no difference was observed for MSC (p>0.05). Additionally, both cell types showed upregulation of osteogenic gene expression (including RUNX2, COL I, OPN, and BSP), increased COL I secretion, and enhanced ECM mineralization compared to those grown on Machined Ti (p<0.05). In conclusion, 3D-printed Ti significantly enhances osteoblastic differentiation in MSC and Saos-2 cultures. It promotes a higher expression of genes linked to bone growth and extracellular matrix mineralization, offering distinct advantages over traditionally Machined Ti. These outcomes highlight the promising potential of 3D-printed Ti for promoting osteogenesis, indicating its suitability for bone tissue engineering applications and advancement in bone regeneration strategies.

Βioprinted tubular structures using a bioactive composite ink for vascular tissue engineering