Silk fibroin-based biomaterials for disc tissue engineering

Baicalein-loaded porous silk fibroin microspheres modulate the senescence of nucleus pulposus cells through the NF-κB signaling pathway

Intervertebral disc degeneration (IVDD), an age-associated degenerative condition, significantly contributes to low back pain, thereby adversely affecting individual health and quality of life, while also imposing a substantial societal burden. Baicalein, a natural flavonoid derived from Scutellaria baicalensis Georgi, demonstrates a range of pharmacological activities, including antioxidant, anti-inflammatory, anti-tumor, and antibacterial properties. This positions it as a promising candidate for the treatment of IVDD through intradiscal drug delivery. However, local degenerative processes and the inherently low fluid exchange within the intervertebral disk are likely to affect drug retention. In this study, we developed baicalein-loaded porous silk fibroin microspheres to extend the drug release profile. Baicalein-loaded porous silk fibroin microspheres were prepared by electrostatic spraying. Subsequent characterization and evaluation of their intrinsic properties were conducted using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy(TEM), and fourier transform infrared spectroscopy (FTIR). The findings of our study demonstrated that baicalein-loaded porous silk fibroin microspheres exhibited a sustained drug release profile. Consequently, these microspheres effectively inhibited the senescence of nucleus pulposus cells (NPCs), which induced by Tert-butyl hydroperoxide (TBHP). Mechanistic investigation utilizing transcriptome sequencing revealed that the NF-κB signaling pathway is involved in the effects of baicalein-loaded porous silk fibroin microspheres. Furthermore, our findings demonstrated that the microspheres exhibited excellent biocompatibility in rats subcutaneous implantation model. Collectively, we developed a promising biomaterial for the treatment of IVDD, warranting further systematic preclinical investigation.

Recent advances of bioaerogels in medicine: Preparation, property and application

Bioaerogels represent a type of three-dimensional porous materials fabricated from natural biopolymers, and show a significant potential for medical application due to their characteristics of extremely low density, high specific surface area, excellent biocompatibility and biodegradability. The preparation method and parameters of bioaerogels are focused on, and their influence on the structure and properties of bioaerogels are discussed in detail. Then, to match the properties of bioaerogels with the medical applications, this work emphasizes the main properties (including biocompatibility, degradability, and mechanical properties), structural parameters (such as suitable porosity, pore size and high specific surface area), and further summarizes the influence of single-component and composite bioaerogels on their properties. Moreover, according to the different applications (wound healing, drug delivery, and tissue engineering and other fields), the function method, mechanism and practical effect of bioaerogels are comprehensively analyzed. Finally, the challenges, future research directions, and solutions for the practical application of bioaerogels in medicine are discussed.

pH-Responsive Modified HAMA Microspheres Regulate the Inflammatory Microenvironment of Intervertebral Discs

Currently, intervertebral disc (IVD) degeneration is believed to lead to local accumulation of lactic acid in the IVD, a decrease in pH, activation of the inflammatory pathway, and continued destruction of homeostasis of the IVD. To address these issues, the intelligent and accurate release of drugs is particularly important. In this study, acid-sensitive release methacrylated hyaluronic acid (HAMA) microspheres were constructed by using microfluidic technology, which can be used as a targeted drug delivery system for intervertebral disc degeneration (IVDD) through Schiff base chemical bonding on the surface of the microspheres to achieve intelligent drug release. Interleukin-1 receptor antagonist (IL-1 Ra) is a naturally occurring anti-inflammatory antagonist of the interleukin-1 family of pro-inflammatory cytokines. Despite its outstanding broad-spectrum anti-inflammatory effects, IL-1 Ra has a short biological half-life (4-6 h). The slow-release performance of IL-1 Ra can be greatly improved using bovine serum albumin nanoparticles (BNP). In addition, the modified HAMA microspheres exhibited good injectability and porosity, and efficient and uniform loading of nanoparticles was achieved via the Schiff base bond. The inflammatory microenvironment can be significantly reversed by transporting the modified HAMA microspheres-BNPs (Modified MS) to the degenerative nucleus pulposus.

Visible-Light-Induced Silk Fibroin Hydrogels with Carbon Quantum Dots as Initiators for 3D Bioprinting Applications

Digital light processing (DLP) 3D bioprinting technology has attracted increasing attention in tissue engineering in recent years. However, it still faces significant technical and operational challenges such as cell carcinogenesis caused by prolonged exposure to ultraviolet light and the presence of heavy metal ions in complex photoinitiator systems. In this study, a novel strategy is designed to introduce carbon quantum dots into visible-light-induced silk fibroin bioink as initiators (CDs/SilMA) applied for DLP 3D bioprinting technology. The incorporation of carbon quantum dots facilitates the formation of precise hydrogel structures at 415 nm visible wavelength, enabling the creation of brain, bronchus, spine, and ear models. Replacing heavy metal photoinitiators with carbon quantum dots imparts fluorescence properties to the bioink and enhances its mechanical properties. Meanwhile, the fibroin protein-based hydrogel exhibits favorable properties, such as drug loading, slow release, degradability, and biocompatibility. This is the first study to propose the application of carbon quantum dots in silk fibroin-based bioink. Moreover, the resulting product demonstrates excellent compatibility with the DLP printing process, making it promising for practical applications in various tissue engineering scenarios with specific requirements.

Polysaccharide-protein based scaffolds for cartilage repair and regeneration

Cartilage repair and regeneration have become a global issue that millions of patients from all over the world need surgical intervention to repair the articular cartilage annually due to the limited self-healing capability of the cartilage tissues. Cartilage tissue engineering has gained significant attention in cartilage repair and regeneration by integration of the chondrocytes (or stem cells) and the artificial scaffolds. Recently, polysaccharide-protein based scaffolds have demonstrated unique and promising mechanical and biological properties as the artificial extracellular matrix of natural cartilage. In this review, we summarize the modification methods for polysaccharides and proteins. The preparation strategies for the polysaccharide-protein based hydrogel scaffolds are presented. We discuss the mechanical, physical and biological properties of the polysaccharide-protein based scaffolds. Potential clinical translation and challenges on the artificial scaffolds are also discussed.

Silk-based intelligent fibers and textiles: structures, properties, and applications

Multifunctional fibers represent a cornerstone of human civilization, playing a pivotal role in numerous aspects of societal development. Natural biomaterials, in contrast to synthetic alternatives, offer environmental sustainability, biocompatibility, and biodegradability. Among these biomaterials, natural silk is favored in biomedical applications and smart fiber technology due to its accessibility, superior mechanical properties, diverse functional groups, controllable structure, and exceptional biocompatibility. This review delves into the intricate structure and properties of natural silk fibers and their extensive applications in biomedicine and smart fiber technology. It highlights the critical significance of silk fibers in the development of multifunctional materials, emphasizing their mechanical strength, biocompatibility, and biodegradability. A detailed analysis of the hierarchical structure of silk fibers elucidates how these structural features contribute to their unique properties. The review also encompasses the biomedical applications of silk fibers, including surgical sutures, tissue engineering, and drug delivery systems, along with recent advancements in smart fiber applications such as sensing, optical technologies, and energy storage. The enhancement of functional properties of silk fibers through chemical or physical modifications is discussed, suggesting broader high-end applications. Additionally, the review addresses current challenges and future directions in the application of silk fibers in biomedicine and smart fiber technologies, underscoring silk's potential in driving contemporary technological innovations. The versatility and sustainability of silk fibers position them as pivotal elements in contemporary materials science and technology, fostering the development of next-generation smart materials.

Cutting-Edge Biomaterials in Intervertebral Disc Degeneration Tissue Engineering

Intervertebral disc degeneration (IVDD) stands as the foremost contributor to low back pain (LBP), imposing a substantial weight on the world economy. Traditional treatment modalities encompass both conservative approaches and surgical interventions; however, the former falls short in halting IVDD progression, while the latter carries inherent risks. Hence, the quest for an efficacious method to reverse IVDD onset is paramount. Biomaterial delivery systems, exemplified by hydrogels, microspheres, and microneedles, renowned for their exceptional biocompatibility, biodegradability, biological efficacy, and mechanical attributes, have found widespread application in bone, cartilage, and various tissue engineering endeavors. Consequently, IVD tissue engineering has emerged as a burgeoning field of interest. This paper succinctly introduces the intervertebral disc (IVD) structure and the pathophysiology of IVDD, meticulously classifies biomaterials for IVD repair, and reviews recent advances in the field. Particularly, the strengths and weaknesses of biomaterials in IVD tissue engineering are emphasized, and potential avenues for future research are suggested.

Ag2 O-TiO2 -NTs enhance osteogenic activity in vitro by modulating TNF-α/β-catenin signaling in bone marrow-derived mesenchymal stem cells

The toxic effects of nanoparticles-silver oxide (Ag2 O) limited its use. However, loading Ag2 O nanoparticles into titanium dioxide (TiO2 ) nanotubes (Ag2 O-TiO2 -NTs) has more efficient biological activity and safety. The aim of this study was to observe the effect of Ag2 O-TiO2 -NTs on osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) and its mechanism. The enzyme activity of lactate dehydrogenase (LDH) and the expression of RUNX family transcription factor 2 (Runx2), OPN, OCN in BMSCs were detected by quantitative real time polymerase chain reaction. At 14 days of induction, the mineralization ability and alkaline phosphatase (ALP) activity of cells in each group were observed by Alizarin Red S staining and ALP staining. In addition, the protein levels of tumor necrosis factor-α (TNF-α) and β-catenin in BMSCs of each group were observed by western blot. After 14 days of the induction, the mineralization ability and ALP activity of BMSCs in the Ag2 O-TiO2 -NTs group were significantly enhanced compared with those in the Ag2 O and TiO2 groups. Western blot analysis showed that the BMSCs in the Ag2 O-TiO2 -NTs group exhibited much lower protein level of TNF-α and higher protein level of β-catenin than those in the Ag2 O and TiO2 groups.Ag2 O-TiO2 -NTs enhance the osteogenic activity of BMSCs by modulating TNF-α/β-catenin signaling.

Research progress of biomaterials and innovative technologies in urinary tissue engineering

Substantial interests have been attracted to multiple bioactive and biomimetic biomaterials in recent decades because of their ability in presenting a structural and functional reconstruction of urinary tissues. Some innovative technologies have also been surging in urinary tissue engineering and urological regeneration by providing insights into the physiological behavior of the urinary system. As such, the hierarchical structure and tissue function of the bladder, urethra, and ureter can be reproduced similarly to the native urinary tissues. This review aims to summarize recent advances in functional biomaterials and biomimetic technologies toward urological reconstruction. Various nanofirous biomaterials derived from decellularized natural tissues, synthetic biopolymers, and hybrid scaffolds were developed with desired microstructure, surface chemistry, and mechanical properties. Some growth factors, drugs, as well as inorganic nanomaterials were also utilized to enhance the biological activity and functionality of scaffolds. Notably, it is emphasized that advanced approaches, such as 3D (bio) printing and organoids, have also been developed to facilitate structural and functional regeneration of the urological system. So in this review, we discussed the fabrication strategies, physiochemical properties, and biofunctional modification of regenerative biomaterials and their potential clinical application of fast-evolving technologies. In addition, future prospective and commercial products are further proposed and discussed.