Silk fibroin/collagen/hyaluronic acid scaffold incorporating pilose antler polypeptides microspheres for cartilage tissue engineering

Osteochondral tissue engineering in translational practice: histological assessments and scoring systems

Osteochondral lesions are common pathological alterations in synovial joints. Different techniques have been designed to achieve osteochondral repair, and tissue-engineered osteochondral grafts have shown the most promise. Histological assessments and related scoring systems are crucial for evaluating the quality of regenerated tissue, and the interpretation and comparison of various repair techniques require the establishment of a reliable and widely accepted histological method. To date, there is still no consensus on the type of histological assessment and scoring system that should be used for osteochondral repair. In this review, we summarize common osteochondral staining methods, discuss the criteria regarding high-quality histological images, and assess the current histological scoring systems for osteochondral regeneration. Safranin O/Fast green is the most widely used staining method for the cartilage layer, whereas Gomori and Van Gieson staining detect new bone formation. We suggest including the graft-host interface and more sections together with the basic histological information for images. An ideal scoring system should analyze both the cartilage and bone regions, especially for the subchondral bone plate. Furthermore, histological assessments should be performed over a longer period of time to minimize discrepancies caused by defect size and animal species.

Silk-Based 3D Porous Scaffolds for Tissue Engineering

Silk fibroin, extracted from the silk of the Bombyx mori silkworm, stands out as a biomaterial due to its nontoxic nature, excellent biocompatibility, and adjustable biodegradability. Porous scaffolds, a type of biomaterial, are crucial for creating an optimal microenvironment that supports cell adhesion and proliferation, thereby playing an essential role in tissue remodeling and repair. Therefore, this review focuses on 3D porous silk fibroin-based scaffolds, first summarizing their preparation methods and then detailing their regenerative effects on bone, cartilage, tendon, vascular, neural, skin, hepatic, and tracheal epithelial tissue engineering in recent years.

Advanced Synthetic Scaffolds Based on 1D Inorganic Micro-/Nanomaterials for Bone Regeneration

Inorganic nanoparticulate biomaterials, such as calcium phosphate and bioglass particles, with chemical compositions similar to that of the inorganic component of natural bone, and hence having excellent biocompatibility and bioactivity, are widely used for the fabrication of synthetic bone graft substitutes. Growing evidence suggests that structurally anisotropic, or 1D inorganic micro-/nanobiomaterials are superior to inorganic nanoparticulate biomaterials in the context of mechanical reinforcement and construction of self-supporting 3D network structures. Therefore, in the past decades, efforts have been devoted to developing advanced synthetic scaffolds for bone regeneration using 1D micro-/nanobiomaterials as building blocks. These scaffolds feature extraordinary physical and biological properties, such as enhanced mechanical properties, super elasticity, multiscale hierarchical architecture, extracellular matrix-like fibrous microstructure, and desirable biocompatibility and bioactivity, etc. In this review, an overview of recent progress in the development of advanced scaffolds for bone regeneration is provided based on 1D inorganic micro-/nanobiomaterials with a focus on their structural design, mechanical properties, and bioactivity. The promising perspectives for future research directions are also highlighted.

Well-known polypeptides of deer antler velvet with key actives: modern pharmacological advances

Deer antler velvet, with kidney tonifying, promoting the production of essence and blood, strengthening tendons and bones, not only has a thousand-year medicinal history but also its modern pharmacology mainly focuses on its active polypeptides on motor, nerve, and immune systems. The purpose of this report is to fill the gap in the comprehensive, systematic, and detailed review of polypeptides during the recent 30 years (1992-2023). The research method was to review 53 pharmacological articles from the Public Medicine, Web of science, ACS, and Science Direct database sources by searching the keywords "pilose antler," "deer velvet," "Pilose Antler Peptide (PAP) and Velvet Antler Polypeptide (VAP)." The results showed that deer antler polypeptides (DAPs), by regulating EGF, EGFR, MAPK, P38, ERK, NF-κB, Wnt, PI3K, Akt, MMP, AMPK, Stir1, NLRP3, HO-1, Nrf, Rho, TLR, TGF-β, Smad, Ang II, etc., revealed their effects on seven system-related diseases and their mechanisms, including osteoarthritis, intervertebral disc degeneration, osteoporosis, Alzheimer's, Parkinson's, triple-negative breast cancer, liver injury, liver fibrosis, cardiovascular disease, acute lung injury, and late-onset hypogonadism. In conclusion, DAPs have good effects on motor and other system-related diseases, but the secondary and tertiary structures of DAPs (0.5-1800 KDa) need to be further elucidated, and the structure-activity relationship study is still unavailable and needs to be covered. It is expected that this review may provide the necessary literature support for further research. The activities and mechanisms of polypeptides from the past 30 years (1992-2023) are summarized covering seven systems, related diseases, and its regulatory genes and proteins.

Self-assembled silk fibroin cross-linked with genipin supplements microbial carbonate precipitation in building material

The process of microbially induced carbonate precipitation (MICP) is known to effectively improve engineering properties of building materials and so does silk fibroin (SF). Thus, in this study, an attempt was taken to see the improvement in sand, that is, basic building material coupled with MICP and SF. Urease producing Bacillus megaterium was utilized for MICP in Nutri-Calci medium. To improve the strength of SF itself in bacterial solution, it was cross-linked with genipin at the optimized concentration of 3.12 mg/mL. The Fourier transform infrared (FTIR) spectra confirmed the crosslinking of SF with genipin in bacterial solution. In order to understand how such cross-linking can improve engineering properties, sand moulds of 50 mm3 dimension were prepared that resulted in 35% and 55% more compressive strength than the one prepared with bacterial solution with SF and bacterial solution only, respectively with higher calcite content in former one. The FTIR, SEM, x-ray powder diffraction spectrometry and x-ray photoelectron spectroscopy analyses confirmed higher biomineral precipitation in bacterial solution coupled with genipin cross-linked SF. As the process of MICP is proven to replace cement partially from concrete without negatively influence mechanical properties, SF cross-linked with genipin can provide additional significance in developing low-carbon cement-based composites.

Synthesis, Characterization, and Induced Osteogenic Differentiation Effect of Collagen Membranes Functionalized by Polydopamine/Graphene Oxide for Bone Tissue Engineering

Collagen is one of the most common natural absorbable polymers, which is widely used as a barrier membrane in biomedical fields due to its many desirable biological properties. However, absorbable membranes such as collagen have their own disadvantages such as unpredictable degradation rates, poor rigidity leading to tissue collapse, and limited osteogenic properties and cell adhesion. In this study, a modified collagen membrane with a polydopamine-graphene oxide (PDA/GO) complex was synthesized to improve the characteristics of collagen for bone tissue engineering. The successful synthesis of PDA/GO on collagen membranes was verified using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The wettability of PDA/GO-modified collagen membranes was considerably improved based on the characterization by water contact angle compared to the uncoated membranes and surface coatings solely by either PDA or GO. The modified PDA/GO coating also enhanced the mechanical properties such as tensile strength and biodegradation rate of collagen membranes. In addition, the PDA/GO coating effectively enhanced the biocompatibility of collagen membranes as verified by the enhanced proliferation and adhesion of human bone marrow stem cells (hBMSCs). Additionally, the effects of PDA/GO coating on the osteogenic differentiation of hBMSCs on collagen membranes were investigated through alkaline phosphatase (ALP) activity and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The PDA/GO coating on collagen membranes resulted in a significant increase in osteogenic properties compared with the uncoated collagen membranes. According to the results of the current study, the combination of PDA and GO-modified collagen membranes could be used for bone tissue engineering and biomedical applications.

Progress in microsphere-based scaffolds in bone/cartilage tissue engineering

Bone/cartilage repair and regeneration have been popular and difficult issues in medical research. Tissue engineering is rapidly evolving to provide new solutions to this problem, and the key point is to design the appropriate scaffold biomaterial. In recent years, microsphere-based scaffolds have been considered suitable scaffold materials for bone/cartilage injury repair because microporous structures can form more internal space for better cell proliferation and other cellular activities, and these composite scaffolds can provide physical/chemical signals for neotissue formation with higher efficiency. This paper reviews the research progress of microsphere-based scaffolds in bone/chondral tissue engineering, briefly introduces types of microspheres made from polymer, inorganic and composite materials, discusses the preparation methods of microspheres and the exploration of suitable microsphere pore size in bone and cartilage tissue engineering, and finally details the application of microsphere-based scaffolds in biomimetic scaffolds, cell proliferation and drug delivery systems.

A sonication-induced silk-collagen hydrogel for functional cartilage regeneration

Cartilage tissue has limited self-regeneration capacity and current treatment methods often result in fibrocartilage formation. Although collagen has shown the ability to induce chondrogenesis of mesenchymal stem cells (MSCs) and regenerate hyaline cartilage, the application of a pure collagen hydrogel is inherently limited by its fast degradation, poor mechanical properties and excessive cell-mediated shrinkage. To overcome this challenge, we developed a sonication-induced silk-collagen composite hydrogel (COL + SF(S)) and investigated its physicochemical and biological properties compared with a collagen hydrogel (COL) and a non-sonicated silk-collagen composite hydrogel (COL + SF(NS)). The results showed that the sonication treatment of silk fibroin induced antiparallel β-sheet formation and a stronger negative charge on the silk fibroin molecule, which resulted in improved mechanical properties of the COL + SF(S) hydrogel. The COL + SF(S) hydrogel exhibited superior stability during cell culture and promoted the gene expression of SOX9 at the early stage and sulfated glycosaminoglycan (sGAG) deposition without any exogenous growth factor. Moreover, the cartilage regeneration capacity of the COL + SF(S) group was evaluated in rabbit knee defects. The COL + SF(S) group exhibited well-integrated articular hyaline cartilage closely resembling native articular cartilage after 6 months. Overall, the COL + SF(S) hydrogel holds great potential as a scaffold material to regenerate functional hyaline cartilage.

Enhancing the function of PLGA-collagen scaffold by incorporating TGF-β1-loaded PLGA-PEG-PLGA nanoparticles for cartilage tissue engineering using human dental pulp stem cells

Since cartilage has a limited capacity for self-regeneration, treating cartilage degenerative disorders is a long-standing difficulty in orthopedic medicine. Researchers have scrutinized cartilage tissue regeneration to handle the deficiency of cartilage restoration capacity. This investigation proposed to compose an innovative nanocomposite biomaterial that enhances growth factor delivery to the injured cartilage site. Here, we describe the design and development of the biocompatible poly(lactide-co-glycolide) acid-collagen/poly(lactide-co-glycolide)-poly(ethylene glycol)-poly(lactide-co-glycolide) (PLGA-collagen/PLGA-PEG-PLGA) nanocomposite hydrogel containing transforming growth factor-β1 (TGF-β1). PLGA-PEG-PLGA nanoparticles were employed as a delivery system embedding TGF-β1 as an articular cartilage repair therapeutic agent. This study evaluates various physicochemical aspects of fabricated scaffolds by ¹HNMR, FT-IR, SEM, BET, and DLS methods. The physicochemical features of the developed scaffolds, including porosity, density, degradation, swelling ratio, mechanical properties, morphologies, BET, ELISA, and cytotoxicity were assessed. The cell viability was investigated with the MTT test. Chondrogenic differentiation was assessed via Alcian blue staining and RT-PCR. In real-time PCR testing, the expression of Sox-9, collagen type II, and aggrecan genes was monitored. According to the results, human dental pulp stem cells (hDPSCs) exhibited high adhesion, proliferation, and differentiation on PLGA-collagen/PLGA-PEG-PLGA-TGFβ1 nanocomposite scaffolds compared to the control groups. SEM images displayed suitable cell adhesion and distribution of hDPSCs throughout the scaffolds. RT-PCR assay data displayed that TGF-β1 loaded PLGA-PEG-PLGA nanoparticles puts forward chondroblast differentiation in hDPSCs through the expression of chondrogenic genes. The findings revealed that PLGA-collagen/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogel can be utilized as a supportive platform to support hDPSCs differentiation by implementing specific physio-chemical features.

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

The Protective Effect of Pilose Antler Peptide on CUMS-Induced Depression Through AMPK/Sirt1/NF-κB/NLRP3-Mediated Pyroptosis

Background: Pilose antler peptide (PAP), prepared from the pilose antler of Cervus nippon Temminck, is widely used in traditional Chinese medicine (TCM) against various inflammatory disorders. TCM prescriptions containing pilose antler are often prescribed clinically to treat depression. However, the pharmacological mechanisms of how PAP, against inflammation, prevents and treats depression remain poorly understood.

Methods: PAP was identified by de novo sequencing and database searching. Then, behavioral tests were conducted to investigate the effect of PAP on CUMS-exposed mice. In parallel, Nissl staining and Golgi-Cox staining were used for exploring the effect of PAP on neural cells and dendritic spine density. Additionally, the expression of key proteins of the AMPK/Sirt1/NF-κB/NLRP3 pathway was analyzed by Western blot. Finally, the CUMS procedure was conducted for 6 weeks. At the 5th week, PAP and fluoxetine (Flu) were intragastrically treated for 2 weeks. The silencing information regulator-related enzyme 1 (Sirt1) inhibitor EX-527 and the AMP-activated protein kinase (AMPK) inhibitor dorsomorphin were employed to investigate the effects of Sirt1 and AMPK on PAP-mediated depression.

Results: PAP attenuated the behavior alteration caused by CUMS stimulation, decreased the number of neurons, and restored the dendritic spine density. PAP treatment effectively upregulated the expressions of p-AMPK and Sirt1 and suppressed the expressions of Ac-NF-κB, NLRP3, Ac-Caspase-1, GSDMD-N, Cleaved-IL-1β, and Cleaved-IL-18. Moreover, selectively inhibited Sirt1 and AMPK were able to compromise the therapeutic effect of PAP on depression.

Conclusion: The present work indicated that PAP has a protective effect on CUMS-induced depression. In addition, AMPK and Sirt1 played critical roles in the PAP-relieved depression. PAP might be a potential therapeutic option for treating depression.

Biodegradable Microparticles for Regenerative Medicine: A State of the Art and Trends to Clinical Application

Tissue engineering and cell therapy are very attractive in terms of potential applications but remain quite challenging regarding the clinical aspects. Amongst the different strategies proposed to facilitate their implementation in clinical practices, biodegradable microparticles have shown promising outcomes with several advantages and potentialities. This critical review aims to establish a survey of the most relevant materials and processing techniques to prepare these micro vehicles. Special attention will be paid to their main potential applications, considering the regulatory constraints and the relative easiness to implement their production at an industrial level to better evaluate their application in clinical practices.

Recent advances of 3D hydrogel culture systems for mesenchymal stem cell-based therapy and cell behavior regulation

Mesenchymal stem cells (MSCs) have been increasingly recognized as resources for disease treatments and regenerative medicine. Meanwhile, the unique chemical and physical properties of hydrogels provide innate advantages to achieve...

Long-term stability, high strength, and 3D printable alginate hydrogel for cartilage tissue engineering application

Cartilage damage is one of the main causes of disability, and 3D bioprinting technology can produce complex structures that are particularly suitable for constructing a customized and irregular tissue engineering scaffold for cartilage repair. Alginate is an attractive biomaterial for bioinks because of its good biological safety profile and fast ionic gelation. However, ionically crosslinked alginate hydrogels are recognized as lacking enough mechanical property and long-term stability due to ion exchange. Here, we developed a double crosslinked alginate (DC-Alg) hydrogel for 3D bioprinting, and human umbilical cord mesenchymal stem cells (huMSCs) could differentiate into chondrocytes on its printed 3D scaffold after 4 weeks' culture. We performed sequential modification of alginate with L-cysteine and 5-norbornene-2-methylamine, and the DC-Alg hydrogels were obtained in the presence of CaCl₂and ultraviolet light with stronger mechanical properties than those of the single ionic crosslinked alginate hydrogels, which was similar to natural cartilage. They also had better stability and could be maintained in DMEM medium for over 1 month, as well good viability for huMSCs. Moreover, the DC-Alg as 3D printing inks demonstrated a better printing accuracy (∼200 µm). After 4 weeks culture of huMSCs in the 3D printed DC-Alg scaffolds, the expressions of chondrogenic genes such asaggrecan (agg), collagen II (col II), and SRY-box transcription factor9(sox-9) were obviously observed, indicating the differentiation of huMSCs into cartilage. Immumohistochemical staining analysis further exhibited cartilage tissue developed well in the 3D printed scaffolds. Our study is the first demonstration of DC-Alg in 3D printing for MSC differentiation into cartilage, which shows a potential application in cartilage defect repair.

Preparation and biological properties of silk fibroin/nano-hydroxyapatite/hyaluronic acid composite scaffold

In this study, the silk fibroin/nano-hydroxyapatite/hyaluronic acid (SF/nHAp/HA) composite scaffolds with different HA contents were developed by blending, cross-linking and freeze-drying, and their physicochemical properties and cell biocompatibilityin vitrowere subsequently studied. It was observed that the molecular conformation of the composite scaffolds was mainly composed of silk I and a small amount of theβ-sheets structure. On enhancing the HA content, the pore size of the scaffold decreased, while the porosity, water absorption, swelling ratio and mechanical properties were observed to increase. In particular, the SF/nHAp/HA scaffold with a 5.0 wt% ratio exhibited the highest water absorption and mechanical properties among the developed materials. In addition, thein vitrocytocompatibility analysis showed that the bone marrow mesenchymal stem cells exhibited excellent cell proliferation and osteogenic differentiation ability on the SF/nHAp/5.0 wt%HA scaffolds, as compared with the other scaffolds. It can be concluded that the developed composite scaffolds represent a promising class of materials for the bone tissue repair and regeneration.

Effects of different aperture-sized type I collagen/silk fibroin scaffolds on the proliferation and differentiation of human dental pulp cells

This study aimed at evaluate the effects of different aperture-sized type I collagen/silk fibroin (CSF) scaffolds on the proliferation and differentiation of human dental pulp cells (HDPCs). The CSF scaffolds were designed with 3D mapping software Solidworks. Three different aperture-sized scaffolds (CSF1-CSF3) were prepared by low-temperature deposition 3D printing technology. The morphology was observed by scanning electron microscope (SEM) and optical coherence tomography. The porosity, hydrophilicity and mechanical capacity of the scaffold were detected, respectively. HDPCs (third passage, 1 × 10⁵ cells) were seeded into each scaffold and investigated by SEM, CCK-8, alkaline phosphatase (ALP) activity and HE staining. The CSF scaffolds had porous structures with macropores and micropores. The macropore size of CSF1 to CSF3 was 421 ± 27 μm, 579 ± 36 μm and 707 ± 43 μm, respectively. The porosity was 69.8 ± 2.2%, 80.1 ± 2.8% and 86.5 ± 3.3%, respectively. All these scaffolds enhanced the adhesion and proliferation of HDPCs. The ALP activity in the CSF1 group was higher than that in the CSF3 groups (P < 0.01). HE staining showed HDPCs grew in multilayer within the scaffolds. CSF scaffolds significantly improved the adhesion and ALP activity of HDPCs. CSF scaffolds were promising candidates in dentine-pulp complex regeneration.

Digital Light Processing Bioprinted Human Chondrocyte-Laden Poly (γ-Glutamic Acid)/Hyaluronic Acid Bio-Ink towards Cartilage Tissue Engineering

Cartilage injury is the main cause of disability in the United States, and it has been projected that cartilage injury caused by osteoarthritis will affect 30% of the entire United States population by the year 2030. In this study, we modified hyaluronic acid (HA) with γ-poly(glutamic) acid (γ-PGA), both of which are common biomaterials used in cartilage engineering, in an attempt to evaluate them for their potential in promoting cartilage regeneration. As seen from the results, γ-PGA-GMA and HA, with glycidyl methacrylate (GMA) as the photo-crosslinker, could be successfully fabricated while retaining the structural characteristics of γ-PGA and HA. In addition, the storage moduli and loss moduli of the hydrogels were consistent throughout the curing durations. However, it was noted that the modification enhanced the mechanical properties, the swelling equilibrium rate, and cellular proliferation, and significantly improved secretion of cartilage regeneration-related proteins such as glycosaminoglycan (GAG) and type II collagen (Col II). The cartilage tissue proof with Alcian blue further demonstrated that the modification of γ-PGA with HA exhibited suitability for cartilage tissue regeneration and displayed potential for future cartilage tissue engineering applications. This study built on the previous works involving HA and further showed that there are unlimited ways to modify various biomaterials in order to further bring cartilage tissue engineering to the next level.

Crosslinked Silk Fibroin/Gelatin/Hyaluronan Blends as Scaffolds for Cell-Based Tissue Engineering

3D porous scaffolds fabricated from binary and ternary blends of silk fibroin (SF), gelatin (G), and hyaluronan (HA) and crosslinked by the carbodiimide coupling reaction were developed. Water-stable scaffolds can be obtained after crosslinking, and the SFG and SFGHA samples were stable in cell culture medium up to 10 days. The presence of HA in the scaffolds with appropriate crosslinking conditions greatly enhanced the swellability. The microarchitecture of the freeze-dried scaffolds showed high porosity and interconnectivity. In particular, the pore size was significantly larger with an addition of HA. Biological activities of NIH/3T3 fibroblasts seeded on SFG and SFGHA scaffolds revealed that both scaffolds were able to support cell adhesion and proliferation of a 7-day culture. Furthermore, cell penetration into the scaffolds can be observed due to the interconnected porous structure of the scaffolds and the presence of bioactive materials which could attract the cells and support cell functions. The higher cell number was noticed in the SFGHA samples, possibly due to the HA component and the larger pore size which could improve the microenvironment for fibroblast adhesion, proliferation, and motility. The developed scaffolds from ternary blends showed potential in their application as 3D cell culture substrates in fibroblast-based tissue engineering.

TCP/PLGA composite scaffold loaded rapamycin in situ enhances lumbar fusion by regulating osteoblast and osteoclast activity

The purpose of this study was to develop a novel β-tricalcium phosphate (TCP)/poly (D,L-lactic-co-glycolic acid) (PLGA) composite scaffold loaded with rapamycin that can regulate the activity of osteoblasts and osteoclasts for lumbar fusion. The TCP/PLGA composite scaffold was fabricated by cryogenic three-dimensional printing techniques and then loaded with rapamycin in situ. The structural surface morphology of the composite scaffold was tested with scanning electron microscope. To evaluate the biocompatibility of the composite scaffold in vitro, bone marrow mesenchymal stem cells (BMSCs) were cultured on the TCP/PLGA composite scaffold slide and tested with Live/Dead Viability Kit. The effect of rapamycin on osteoclast and osteoblast was studied with staining and Western blotting. The in vitro results showed that the rapamycin-loaded TCP/PLGA composite scaffold showed good biocompatibility with BMSC and released rapamycin obviously promoted the osteoblast differentiation and mineralization. In vivo study, the TCP/PLGA composite scaffold loaded with rapamycin were implanted in lumbar fusion model and study with micro-computed tomography scanning, hematoxylin-eosin, Masson, and immune-histological staining, to evaluate the effect of rapamycin on bone fusion. The in vivo results demonstrated that rapamycin-loaded TCP/PLGA composite scaffold could enhance bone formation by regulating osteoblast and osteoclast activity, respectively. In this study, the TCP/PLGA composite scaffold loaded with rapamycin was confirmed to provide great compatibility and improved performance in lumbar fusion by regulating osteoblastic and osteoclastic activity and would be a promising composite biomaterial for bone tissue engineering.

3D Printed Poly(ε-Caprolactone)/Meniscus Extracellular Matrix Composite Scaffold Functionalized With Kartogenin-Releasing PLGA Microspheres for Meniscus Tissue Engineering

Meniscus tissue engineering (MTE) aims to fabricate ideal scaffolds to stimulate the microenvironment for recreating the damaged meniscal tissue. Indeed, favorable mechanical properties, suitable biocompatibility, and inherent chondrogenic capability are crucial in MTE. In this study, we present a composite scaffold by 3D printing a poly(ε-caprolactone) (PCL) scaffold as backbone, followed by injection with the meniscus extracellular matrix (MECM), and modification with kartogenin (KGN)-loaded poly(lactic-co-glycolic) acid (PLGA) microsphere (μS), which serves as a drug delivery system. Therefore, we propose a plan to improve meniscus regeneration via KGN released from the 3D porous PCL/MECM scaffold. The final results showed that the hydrophilicity and bioactivity of the resulting PCL/MECM scaffold were remarkably enhanced. In vitro synovium-derived mesenchymal stem cells (SMSCs) experiments suggested that introducing MECM components helped cell adhesion and proliferation and maintained promising ability to induce cell migration. Moreover, KGN-incorporating PLGA microspheres, which were loaded on scaffolds, showed a prolonged release profile and improved the chondrogenic differentiation of SMSCs during the 14-day culture. Particularly, the PCL/MECM-KGN μS seeded by SMSCs showed the highest secretion of total collagen and aggrecan. More importantly, the synergistic effect of the MECM and sustained release of KGN can endow the PCL/MECM-KGN μS scaffolds with not only excellent cell affinity and cell vitality preservation but also chondrogenic activity. Thus, the PCL/MECM-KGN μS scaffolds are expected to have good application prospects in the field of MTE.

Decellularization of caprine esophagus using fruit pericarp extract of Sapindus mukorossi

Biological detergents like sodium deoxycholate, sodium dodecyl sulphate and Triton X-100 impairs the collagenous and non-collagenous proteins, glycosaminoglycans and growth factors. Further, certain chemical and enzymes are responsible for residual cytotoxicity in the decellularized extracellular matrix. The main focus of this study was to explore the decellularization property of soap nut pericarp extract (SPE) for development of decellularized tubular esophageal scaffold. For this 2.5, 5.0 and 10% concentrations of SPE were used for decellularization of caprine esophageal tissues. Histological analysis of hematoxylin and eosin and Masson's trichrome stained tissue samples confirmed decellularization with preservation of extracellular matrix microarchitecture. Scanning electron microscopic images of luminal surface of decellularized esophageal matrix showed randomly oriented collagen fibres with large interconnected pores and cells were absent. However, the external surface was more textured with fibrous structures and collagen fibres were well preserved. DAPI stained decellularized tissues revealed complete removal of nuclear components, verified by DNA content measurement and SDS-PAGE. The FTIR spectra of decellularized esophagus shows absorption peaks of amide A, B, I, II and III. Elastic modulus of the decellularized esophagus scaffolds increased (P > 0.05) as compared to native tissues. Histological and scanning electron microscopic evaluation of in vitro seeded scaffolds showed attachment and growth of primary chicken embryo fibroblasts over and within the decellularized scaffolds. It was concluded that 5% SPE is ideal for preparation of cytocompatible decellularized caprine esophageal scaffold with well-preserved extracellular matrix architecture and, may be used as an alternative to biological detergents and other chemicals.

Is Dialdehyde Chitosan a Good Substance to Modify Physicochemical Properties of Biopolymeric Materials?

The aim of this work was to compare physicochemical properties of three dimensional scaffolds based on silk fibroin, collagen and chitosan blends, cross-linked with dialdehyde starch (DAS) and dialdehyde chitosan (DAC). DAS was commercially available, while DAC was obtained by one-step synthesis. Structure and physicochemical properties of the materials were characterized using Fourier transfer infrared spectroscopy with attenuated total reflectance device (FTIR-ATR), swelling behavior and water content measurements, porosity and density observations, scanning electron microscopy imaging (SEM), mechanical properties evaluation and thermogravimetric analysis. Metabolic activity with AlamarBlue assay and live/dead fluorescence staining were performed to evaluate the cytocompatibility of the obtained materials with MG-63 osteoblast-like cells. The results showed that the properties of the scaffolds based on silk fibroin, collagen and chitosan can be modified by chemical cross-linking with DAS and DAC. It was found that DAS and DAC have different influence on the properties of biopolymeric scaffolds. Materials cross-linked with DAS were characterized by higher swelling ability (~4000% for DAS cross-linked materials; ~2500% for DAC cross-linked materials), they had lower density (Coll/CTS/30SF scaffold cross-linked with DAS: 21.8 ± 2.4 g/cm3; cross-linked with DAC: 14.6 ± 0.7 g/cm3) and lower mechanical properties (maximum deformation for DAC cross-linked scaffolds was about 69%; for DAS cross-linked scaffolds it was in the range of 12.67 ± 1.51% and 19.83 ± 1.30%) in comparison to materials cross-linked with DAC. Additionally, scaffolds cross-linked with DAS exhibited higher biocompatibility than those cross-linked with DAC. However, the obtained results showed that both types of scaffolds can provide the support required in regenerative medicine and tissue engineering. The scaffolds presented in the present work can be potentially used in bone tissue engineering to facilitate healing of small bone defects.

Development of Gelatin-Silk Sericin Incorporated with Poly(vinyl alcohol) Hydrogel-Based Nanocomposite for Articular Cartilage Defects in Rat Knee Joint Repair

Sericin, a silk protein, has a high potential for use as an extracellular matrix in tissue engineering applications. In this study, novel gelatin (GEL) and silk sericin (SS) were incorporated with a polyvinyl alcohol) PVA hydrogel nanocomposite (GEL-SS-PVA) scaffold that can be applied to repair cartilage. Glutaraldehyde was used as a cross-linking agent, with hydrochloric acid acting as an initiator. The microstructure characteristics of the obtained GEL-SS and GEL-SS-PVA scaffolds were also examined using FTIR and XRD spectra and their enhanced thermal stability was assessed by TGA. The blended GEL-SS and GEL-SS-PVA scaffolds were confirmed by SEM analysis to be highly porous with optimum pore sizes of 172 and 58 µm, respectively. Smaller pore sizes and improved uniformity were observed as the concentration of PVA in the GEL-SS-PVA scaffold increased. PVA decreased the tensile strength and elongation of the membranes but increased the modulus. Swelling studies showed high swellability and complete degradation in the presence of phosphate-buffered saline. Cytocompatibility of the GEL-SS-PVA scaffolds showed that these had the highest potential to promote cell proliferation as evaluated with standard microscopy using L929 fibroblasts. The prepared GEL-SS composite scaffold incorporated with the PVA hydrogel was implanted in full-thickness articular cartilage defects in rats. The repair effect of cartilage defects was observed and evaluated among the GEL-SS-PVA, GEL-SS, and control operation groups. The defects were almost completely repaired after 14 weeks in the GEL-SS-PVA group, thereby indicating that the GEL-SS-PVA composite had a favorable effect on articular cartilage defects in rat knee joint repair.

Biomaterials with Potential Use in Bone Tissue Regeneration-Collagen/Chitosan/Silk Fibroin Scaffolds Cross-Linked by EDC/NHS

Blending of different biopolymers, e.g., collagen, chitosan, silk fibroin and cross-linking modifications of these mixtures can lead to new materials with improved physico-chemical properties, compared to single-component scaffolds. Three-dimensional scaffolds based on three-component mixtures of silk fibroin, collagen and chitosan, chemically cross-linked, were prepared and their physico-chemical and biological properties were evaluated. A mixture of EDC (N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride) and NHS (N-hydroxysuccinimide) was used as a cross-linking agent. FTIR was used to observe the position of the peaks characteristic for collagen, chitosan and silk fibroin. The following properties depending on the scaffold structure were studied: swelling behavior, liquid uptake, moisture content, porosity, density, and mechanical parameters. Scanning Electron Microscopy imaging was performed. Additionally, the biological properties of these materials were assessed, by metabolic activity assay. The results showed that the three-component mixtures, cross-linked by EDC/NHS and prepared by lyophilization method, presented porous structures. They were characterized by a high swelling degree. The composition of scaffolds has an influence on mechanical properties. All of the studied materials were cytocompatible with MG-63 osteoblast-like cells.

Potential and recent advances of microcarriers in repairing cartilage defects

Articular cartilage regeneration is one of the challenges faced by orthopedic surgeons. Microcarrier applications have made great advances in cartilage tissue engineering in recent years and enable cost-effective cell expansion, thus providing permissive microenvironments for cells. In addition, microcarriers can be loaded with proteins, factors, and drugs for cartilage regeneration. Some microcarriers also have the advantages of injectability and targeted delivery. The application of microcarriers with these characteristics can overcome the limitations of traditional methods and provide additional advantages. In terms of the transformation potential, microcarriers have not only many advantages, such as providing sufficient and beneficial cells, factors, drugs, and microenvironments for cartilage regeneration, but also many application characteristics; for example, they can be injected to reduce invasiveness, transplanted after microtissue formation to increase efficiency, or combined with other stents to improve mechanical properties. Therefore, this technology has enormous potential for clinical transformation. In this review, we focus on recent advances in microcarriers for cartilage regeneration. We compare the characteristics of microcarriers with other methods for repairing cartilage defects, provide an overview of the advantages of microcarriers, discuss the potential of microcarrier systems, and present an outlook for future development.

Translational potential of this article

We reviewed the advantages and recent advances of microcarriers for cartilage regeneration. This review could give many scholars a better understanding of microcarriers, which can provide doctors with potential methods for treating patients with cartilage injure.

PLLA Porous Microsphere-Reinforced Silk-Based Scaffolds for Auricular Cartilage Regeneration

Microtia, frequently encountered in plastic surgery practice, is usually corrected by auricular reconstruction with prostheses or autologous cartilages. In recent decades, however, cartilage tissue engineering has been emerging as a promising alternative for its minimal invasion and low immunogenicity. As a critical factor for tissue engineering, scaffolds are expected to be sufficiently porous and stiff to facilitate chondrogenesis. In this work, we introduce novel poly-l-lactic acid (PLLA) porous microsphere-reinforced silk-based hybrid (SBH) scaffolds with a multihierarchical porous structure. The scaffolds are fabricated by embedding PLLA porous microspheres (PMs) into a blending matrix of silk fibroin (SF) and gelatin solution, followed by mixing with a degummed silk fiber mesh and freeze-drying process. Through adjusting the amount of PLLA PMs, the mechanical strength approximates to natural cartilage and also balanced physical properties were realized. Biological evaluations of SBH scaffolds, both in vitro and in vivo, were conducted and PM-free plain silk-based (PSB) scaffolds were applied as control. Overall, it suggests that the incorporation of PLLA PMs remarkably improves mechanical properties and the capability to promote chondrogenesis of SBH scaffolds, and that SBH scaffolds appear to be a promising construct for potential applications in auricular cartilage tissue engineering and relevant fields.

Growth Factor and Its Polymer Scaffold-Based Delivery System for Cartilage Tissue Engineering

The development of biomaterials, stem cells and bioactive factors has led to cartilage tissue engineering becoming a promising tactic to repair cartilage defects. Various polymer three-dimensional scaffolds that provide an extracellular matrix (ECM) mimicking environment play an important role in promoting cartilage regeneration. In addition, numerous growth factors have been found in the regenerative process. However, it has been elucidated that the uncontrolled delivery of these factors cannot fully exert regenerative potential and can also elicit undesired side effects. Considering the complexity of the ECM, neither scaffolds nor growth factors can independently obtain successful outcomes in cartilage tissue engineering. Therefore, collectively, an appropriate combination of growth factors and scaffolds have great potential to promote cartilage repair effectively; this approach has become an area of considerable interest in recent investigations. Of late, an increasing trend was observed in cartilage tissue engineering towards this combination to develop a controlled delivery system that provides adequate physical support for neo-cartilage formation and also enables spatiotemporally delivery of growth factors to precisely and fully exert their chondrogenic potential. This review will discuss the role of polymer scaffolds and various growth factors involved in cartilage tissue engineering. Several growth factor delivery strategies based on the polymer scaffolds will also be discussed, with examples from recent studies highlighting the importance of spatiotemporal strategies for the controlled delivery of single or multiple growth factors in cartilage tissue engineering applications.

Hydrosoluble collagen based biodegradable hybrid hydrogel for biomedical scaffold

Hydrogel scaffolds are explored as efficient methods to repair damaged organs or tissues. In this study, we developed a hybrid hydrogel system based on collagen (Col) and PEG-derived polymer (PEGF) for biomedical scaffold. The Col-PEGF hybrid hydrogel, in which different materials were combined and sequential interpenetrating networks were built, achieved significantly enhanced mechanical strength and viscoelasticity compared with the corresponding Col hydrogel or PEGF hydrogel. Degradation test indicated that Col enabled the hybrid hydrogel to be broken down via enzymatic degradation while PEGF contributed to the anti-degradation of the hydrogel. This balanced biodegradability of Col-PEGF hydrogel would be advantageous to the application for tissue engineering and regenerative medicine. Moreover, the Col-PEGF hybrid hydrogel with micron-sized pores and variable moisture performed good biocompatibility to NIH-3T3 cells, and supplied a favorable environment for cell growth and proliferation. Therefore, the Col-PEGF hydrogel will provide a promising biomedical scaffold for the therapy of tissue defects.

Ginsenoside Rb1/TGF-β1 loaded biodegradable silk fibroin-gelatin porous scaffolds for inflammation inhibition and cartilage regeneration

Creating a microenvironment with low inflammation and favorable for the chondrogenic differentiation of endogenous stem cells plays an essential role in cartilage repairing. In the present study, we design a novel ginsenoside Rb1/TGF-β1 loaded silk fibroin-gelatin porous scaffold (GSTR) with the function of attenuating inflammation and promoting chondrogenesis. The scaffold has porous microstructure, proper mechanical strength, degradation rate and sustained release of Rb1 and TGF-β1. Rat bone marrow-derived mesenchymal stem cells (rBMSCs) seeded into GSTR scaffolds are homogeneously distributed and display a higher proliferation rate than non-loaded scaffolds (GS). GSTR scaffolds promote the chondrogenic differentiation of rBMSCs and suppress the expression of inflammation genes. Under the stimulation of IL-1β, the inflammation level of the chondrocytes seeded in GSTR scaffolds is also significantly down-regulated. Moreover, GSTR scaffolds implanted into the osteochondral defects in rats effectively promote the regeneration of hyaline cartilage 12 weeks after surgery when compared with other groups. It is demonstrated that this scaffold loaded with Rb1 and TGF-β1 can synergistically create a microenvironment favorable for cartilage regeneration by promoting the chondrogenesis and suppressing the inflammation levels in vivo. These results prove it has a great potential to develop this Rb1/TGF-β1 releasing scaffold into a novel and promising therapeutic for cartilage repair.

Construction and Evaluation of Collagen-Based Corneal Grafts Using Polycaprolactone To Improve Tension Stress

The emergence of innovative surgical procedures using partial thickness corneal transplant has created a need for the development of corneal grafts to replace pathologic corneal tissue. Corneal repair materials have been successfully prepared in the past 10 years, but they were difficult to be used in clinics because of the unbearable tension caused by interrupted suture during routine surgery. However, polycaprolactone (PCL), a medical polymer material, can solve this problem. Therefore, a hierarchical collagen (Col)-based corneal graft with curvature, consisting of a transparent core part composed of collagen in the center and a mechanically robust fixed part containing collagen and polycaprolactone in the edge, was used as a potential corneal graft for corneal repair and regeneration in this study. The hierarchical collagen-based corneal grafts [collagen-polycaprolactone (Col-PCL) membranes] that are capable of mimicking the native cornea were developed based on chemical and thermal crosslinking mechanisms. The water adsorption of Col-PCL membranes could reach over 80% similar to that of human cornea, and its swelling could reach over 400%. More importantly, the formed Col-PCL membranes could resist a larger tensile strength (1.1 ± 0.03 MPa) before rupturing in comparison with pure collagen membranes and polycaprolactone membranes. Furthermore, the biodegradable Col-PCL membranes could facilitate cell adhesion and proliferation as well as cell migration (exhibiting epithelial wound coverage in <5 days), which showed promise as corneal grafts for cornea tissue engineering.

Bionic composite hydrogel with a hybrid covalent/noncovalent network promoting phenotypic maintenance of hyaline cartilage

A novel injectable bionic hydrogel with hybrid covalent/noncovalent network derived from covalent conjugation of HA-SH and noncovalent supramolecular self-assembly of BPAA-AFF-OH short peptide is fabricated.

Cellulose Nanofibers and Other Biopolymers for Biomedical Applications. A Review

Biopolymers are materials synthesised or derived from natural sources, such as plants, animals, microorganisms or any other living organism. The use of these polymers has grown significantly in recent years as industry shifts away from unsustainable fossil fuel resources and looks towards a softer and more sustainable environmental approach. This review article covers the main classes of biopolymers: Polysaccharides, proteins, microbial-derived and lignin. In addition, an overview of the leading biomedical applications of biopolymers is also provided, which includes tissue engineering, medical implants, wound dressings, and the delivery of bioactive molecules. The future clinical applications of biopolymers are vast, due to their inherent biocompatibility, biodegradability and low immunogenicity. All properties which their synthetic counterparts do not share.

Preparation and characterisation of a novel silk fibroin/hyaluronic acid/sodium alginate scaffold for skin repair

To mimic the natural structure of tissue extracellular matrix, a novel silk fibroin (SF)/hyaluronic acid (HA)/sodium alginate (SA) composite scaffold (92% in porosity) was prepared by freeze-drying. Fourier-transform infrared spectroscopy and Raman spectra indicated interactions among SF, HA, and SA molecules. Scanning electron microscopy showed that the prepared SF/HA/SA scaffold had soft, elastic characteristics, with an average pore diameter of 93 μm. Mechanical property, thermogravimetric analyses and degradation results indicated that the SF/HA/SA scaffold had good physical stability in body fluid and mechanical movement-related environments. Cell proliferation, morphological, and live-dead analyses showed that NIH-3T3 fibroblast cells were better able to attach, grow, and proliferate on the SF/HA/SA scaffold compared with SF, SF/HA, and SF/SA scaffolds. We evaluated the wound healing effects in a rat full-thickness burn model. The hematoxylin-eosin (H&E) and Masson's trichrome staining results from SF/HA/SA scaffold showed that improved re-epithelialization, enhanced extracellular matrix remodeling. Our findings showed that the prepared SF/HA/SA scaffold can provide a potential way as a wound dressing for skin repair.