Biomimetic, Osteoconductive Non-mulberry Silk Fiber Reinforced Tricomposite Scaffolds for Bone Tissue Engineering

Bioresorbable silk grafts for small diameter vascular tissue engineering applications: In vitro and in vivo functional analysis

The success of tissue-engineered vascular graft (TEVG) predominantly relies on the selection of a suitable biomaterial and graft design. Natural biopolymer silk has shown great promise for various tissue-engineering applications. This study is the first to investigate Indian endemic non-mulberry silk (Antheraea assama-AA) - which inherits naturally superior mechanical and biological traits (e.g., RGD motifs) compared to Bombyx mori-BM silk, for TEVG applications. We designed bi-layered biomimetic small diameter AA-BM silk TEVGs adopting a new fabrication methodology. The inner layer showed ideally sized (~40 µm) pores with interconnectivity to allow cellular infiltration, and an outer dense electrospun layer that confers mechanical resilience. Biodegradation of silk TEVGs into amino acids as resorbable byproducts corroborates their in vivo remodeling ability. Following our previous reports, we surgically implanted human adipose tissue-derived stromal vascular fraction (SVF) seeded silk TEVGs in Lewis rats as abdominal aortic interposition grafts for 8 weeks. Adequate suture retention strength (0.45 ± 0.1 N) without any blood seepage post-implantation substantiate the grafts' viability. AA silk-based TEVGs showed superior animal survival and graft patency compared to BM silk TEVGs. Histological analysis revealed neo-tissue formation, host cell infiltration and graft remodeling in terms of extracellular matrix turnover. Altogether, this study demonstrates promising aspects of AA silk TEVGs for vascular tissue engineering applications. STATEMENT OF SIGNIFICANCE: Clinical 'off the shelf' implementation of tissue-engineered vascular grafts (TEVGs) remains a challenge. Achieving optimal blood vessel regeneration requires the use of bioresorbable materials having suitable degradation rates while producing minimal or no toxic byproducts. Host cell recruitment and preventing acute thrombosis are other pre-requisites for successful graft remodeling. In this study, for the first time we explored the use of naturally derived Indian endemic non-mulberry Antheraea assama silk in combination with Bombyx mori silk for TEVG applications by adopting a new biomimetic approach. Our bi-layered silk TEVGs were optimally porous, mechanically resilient and biodegradable. In vivo implantation in rat aorta showed long-term patency and graft remodeling by host cell infiltration and extracellular matrix deposition corroborating their clinical feasibility.

In Vitro Culture of Human Corneal Endothelium on Non-Mulberry Silk Fibroin Films for Tissue Regeneration

Purpose

The purpose of this study was to determine if non-mulberry varieties of silk are suitable for the culture of corneal endothelium (CE).

Methods

Aqueous silk fibroin derived from Philosamia ricini (PR), Antheraea assamensis (AA), and Bombyx mori (BM) were cast as approximately 15 µm films with and without pores on which human CE cells were cultured. Tensile strength, elasticity, transmittance in visible range, and degradation properties of the films were characterised. Adhesion of CE to the silk films was quantified using MTT assay in addition to quantifying the number and area of focal adhesions using paxillin. Expression of CE markers was determined at the gene and protein levels using PCR and immunostaining, respectively. Barrier integrity of the cultured cells was measured as permeability to FITC dextran (10 kDa) in the presence or absence of thrombin.

Results

The films exhibited robust tensile strength, >95% transmittance and a refractive index comparable to the native cornea. BM degraded significantly faster when compared to PR and AA. A comparison between the three varieties of silk showed that significantly more cells were adhered to PR and AA than to BM. This was also reflected in the expression of stable focal adhesions on PR and AA, thus enabling the formation of intact monolayers of cells on these varieties unlike on BM. Treatment with thrombin significantly increased cellular permeability to dextran.

Conclusions

Our data shows that PR and AA varieties sufficiently support the growth and function of CE cells. This could be attributed to the presence of natural cell binding motifs (RGD) in these varieties.

Translational Relevance

Development of a suitable carrier for engineering the CE to address a major clinical requirement of healthy donor tissues for transplantation.

Biomimetic hydroxyapatite/silkfibre/methylcellulose composites for bone tissue engineering applications

Hydroxyapatite (HAP)/silk fibre (SF)/methylcellulose (MC) composites were developed by an electrospinning (E-Spin) method.

A facile strategy to construct silk fibroin based GTR membranes with appropriate mechanical performance and enhanced osteogenic capacity

A facile method to modify electrospun silk fibroin nanofibrous membranes for enhanced mechanical properties and osteogenic function via polyphenol chemistry.

Electrical stimulation as a novel tool for regulating cell behavior in tissue engineering

Recently, electrical stimulation as a physical stimulus draws lots of attention. It shows great potential in disease treatment, wound healing, and mechanism study because of significant experimental performance. Electrical stimulation can activate many intracellular signaling pathways, and influence intracellular microenvironment, as a result, affect cell migration, cell proliferation, and cell differentiation. Electrical stimulation is using in tissue engineering as a novel type of tool in regeneration medicine. Besides, with the advantages of biocompatible conductive materials coming into view, the combination of electrical stimulation with suitable tissue engineered scaffolds can well combine the benefits of both and is ideal for the field of regenerative medicine. In this review, we summarize the various materials and latest technologies to deliver electrical stimulation. The influences of electrical stimulation on cell alignment, migration and its underlying mechanisms are discussed. Then the effect of electrical stimulation on cell proliferation and differentiation are also discussed.

Enhanced osseointegration of double network hydrogels via calcium polyphosphate incorporation for bone regeneration

To overcome the low mechanical strength and difficult bonding of hydrogels to bones which are the major limitations of hydrogels used in bone-regeneration, a new type of calcium polyphosphate incorporated into bioinspired alginate/polyacrylic acid (CPP/PAA-Alg) hybrid double network (DN) hydrogel with both high strength and enhanced osseointergration was prepared by a two-step polymerization with alginate and polyacrylic acid for bone regeneration. The morphology, mechanical properties, swelling, biocompatibility, osseointegration and osteogenic ability of this CPP/PAA-Alg DN hydrogel were investigated. The results show that CPP/PAA-Alg DN hydrogel with highly porous microstructure possesses high water absorption capacity and highly strength properties which meet the requirements of bone repairing. The results of in vitro studies revealed that the CPP/PAA-Alg DN hydrogels can support the spread of cells and promote the cell proliferation. Animal studies demonstrated that the CPP incorporated would enhance the osseointegration of DN hydrogel with host bone at an early stage after implantation to accelerate the regeneration of bone. This research may provide a new way to develop biocompatible biomaterials with high mechanical strength and good osseointegration to meet the needs of bone regeneration.

Highly biodegradable and bioactive Fe-Pd-bredigite biocomposites prepared by selective laser melting

Iron (Fe) has been highly anticipated as a bone implant material owing to the biodegradability and excellent mechanical properties, but limited by the slow degradation and poor bioactivity. In this study, novel Fe-palladium (Pd)-bredigite biocomposites were developed by selective laser melting aiming to improve both the degradation behavior and bioactivity of Fe. The results showed that most Pd formed Pd-rich intermetallic phases (IMPs) with a nearly continuous network while the bredigite phase was distributed at the grain boundaries. In addition, a large amount of much nobler IMPs formed micro-galvanic pairs with the Fe matrix, inducing tremendous micro-galvanic corrosion. The IMPs contained a high amount of Pd2+ with a high reduction potential, which further promoted the efficiency of micro-galvanic corrosion. Moreover, the rapid degradation of bredigite also facilitated the penetration of the corrosion medium. As a result, the Fe-4Pd-5bredigite biocomposite showed a uniform degradation with a rate that is 6 times that of Fe. Furthermore, the developed Fe-Pd-bredigite biocomposites also featured excellent bioactivity, cytocompatibility, and suitable mechanical properties as characterized by the rapid apatite deposition, normal proliferation of human osteoblast-like cells (MG-63), and comparable strength and microhardness with the native bone. Overall, this study opens a new avenue for improving both the degradation and bioactivity of Fe-based composites and may facilitate their applications as biodegradable implants for tissue/organ repair.

A three-dimensional printed silk-based biomimetic tri-layered meniscus for potential patient-specific implantation

Employing tissue engineering principles aided by three-dimensional (3D) printing strategies to fabricate meniscus tissue constructs could help patients with meniscus injury regain mobility, improve pain management and reduce the risk of development of knee osteoarthritis. Here we report a 3D printed meniscus scaffold that biomimics the internal and bulk architecture of the menisci. A shear-thinning novel silk fibroin-gelatin-based bioink with high print fidelity was optimized for the fabrication of scaffolds to serve as potential meniscus implants. Physicochemical characterization of the fabricated scaffolds shows optimum swelling, degradation and mechanical properties. Further, the scaffolds were seeded with meniscus fibrochondrocytes to validate their bioactivity. Fibrochondrocytes seeded on the scaffolds maintained their phenotype and proliferation, and enhanced glycosaminoglycan and total collagen synthesis was observed. Gene expression profile, biochemical quantification and histological studies confirmed the ability of the scaffolds to form meniscus-like tissue constructs. The scaffolds were found to possess amenable immunocompatibility in vitro as well as in vivo. Due to their excellent biological and physicochemical characteristics, these 3D printed scaffolds may be fine-tuned into viable alternatives to the present clinical treatment approaches to meniscus repair.

Promoted Osteoconduction of Polyurethane-Urea Based 3D Nanohybrid Scaffold through Nanohydroxyapatite Adorned Hierarchical Titanium Phosphate

The lack of optimal physiological properties, bacterial colonization, and auto-osteoinduction, are the foremost issues of orthopedic implantations. In terms of bone healing, many researchers have reported the release of additional growth factors of the implanted biomaterials to accelerate the bone regeneration process. However, the additional growth factor may cause side effects such as contagion, nerve pain, and the formation of ectopic bone. Thus, the design of an osteoconductive scaffold having excellent biocompatibility, appropriate physicomechanical properties, and promoted auto osteoinductivity with antibacterial activity is greatly desired. In this study, 2D rodlike nanohydroxyapatite (nHA) adorned titanium phosphate (TP) with a flowerlike morphology was synthesized by a hydrothermal precipitation reaction. The nanohybrid material (nHA-TP) was incorporated into the synthesized polycaprolactone diol and spermine based thermoplastic polyurethane-urea (PUU) via in situ technique followed by salt leaching to fabricate the macroporous 3D polymer nanohybrid scaffold (PUU/nHA-TP). Structure explication of PUU was performed by NMR spectroscopy. The synthesized nanohybrid scaffold with 1% nHA-TP showed 67% increase of tensile strength and 18% improved modulus compared to the pristine PUU via formation of H-bonding or dative bonds between the metal and the amide linkage of the polyurethane or polyurea. In vitro study showing improved cell viability and proliferation of the seeded cell revealed the superior osteoconductivity of the nanohybrid scaffold. Most importantly, the in vivo experiments revealed a significant amount of bone regeneration in the nanohybrid scaffold implanted tibial site compared to the pristine scaffold without any toxic effect. Introduction of the minute amount of titanium phosphate within the adorned nHA promotes the osteoconductivity significantly by the capability of forming coordinate bonds of the titanium ion. Depending on the mechanical, physicochemical, in vitro characteristics, and in vivo osteoconductivity, the PUU/nHA-TP nanohybrid scaffold has great potential as an alternative biomaterial in bone tissue regeneration application.

Interactions at scaffold interfaces: Effect of surface chemistry, structural attributes and bioaffinity

Effective regenerative medicine relies on understanding the interplay between biomaterial implants and the adjoining cells. Scaffolds contribute by presenting sites for cellular adhesion, growth, proliferation, migration, and differentiation which lead to regeneration of tissues over desired periods of time. The fabrication and recruitment of scaffolds often fail to consider the interactions that occur at the interfaces, thereby risking rejection. This lack of knowledge on interfacial microenvironments and related exchanges often causes reduced cellular interactions, poor cell survival and intervention failure. Successful regenerative therapy requires scaffolds with bespoke biocompatibility, optimum pore structure, and cues for cell attachments. These factors determine the development of cellular affinity in scaffolds. For biomedical applications, a detailed understanding of scaffolds and their interfaces is required for better tuning of biomaterials to suit the microenvironments. In this review, we discuss the role of biointerfaces with a focus on surface chemistry, pore structure, scaffold hydro-affinity and their biointeractions. An understanding of the effect of scaffold interfacial properties is crucial for enhancing the progress of tissue engineering towards clinical applications.

Biological evaluation of porous nanocomposite scaffolds based on strontium substituted β-TCP and bioactive glass: An in vitro and in vivo study

In the current study, in vitro analysis of the osteogenic potential of different scaffolds based on strontium-substituted β-TCP (Sr-TCP) and bioactive glass (BG) ceramics was conducted using rabbit bone marrow-derived mesenchymal stem cells (rBMSCs) and the osteogenic ability of the prepared Sr-TCP and BG scaffold was evaluated through alkaline phosphatase activity, mineral deposition by Alizarin red staining, and osteoblastic gene expression experiments. The obtained in vitro results revealed that among experimental Sr-TCP/BG nanocomposite scaffold samples with the composition of Sr-TCP/BG: 100/0, 50/50, 75/25, and 25/75, the 50Sr-TCP/50BG sample presented better osteoinductive properties. Therefore, the optimized 50Sr-TCP/50BG nanocomposite scaffold was chosen for further in vivo experiments. In vivo implantation of 50Sr-TCP/50BG scaffold and hydroxyapatite (HA)/TCP granules in a rabbit calvarial defect model showed slow degradation of 50Sr-TCP/50BG scaffold and high resorption rate of HA/TCP granules at 5 months' post-surgery. However, the 50Sr-TCP/50BG scaffolds loaded by mesenchymal stem cells (MSCs) were mainly replaced with new bone even at 2 months post-implantation. Based on the obtained engineering and biological results, 50Sr-TCP/50BG nanocomposite scaffold containing MSCs could be considered as a promising alternative substitute even for load-bearing bone tissue engineering applications.

Understanding the Stiff-to-Compliant Transition of the Meniscal Attachments by Spatial Correlation of Composition, Structure, and Mechanics

Recently, the scientific community has shown considerable interest in engineering tissues with organized compositional and structural gradients to mimic hard-to-soft tissue interfaces. This effort is hindered by an incomplete understanding of the construction of native tissue interfaces. In this work, we combined Raman microscopy and confocal elastography to map compositional, structural, and mechanical features across the stiff-to-compliant interface of the attachments of the meniscus in the knee. This study provides new insight into the methods by which biology mediates multiple orders of magnitude changes in stiffness over tens of microns. We identified how the nano- to mesoscale architecture mediates complex microscale transitional regions across the interface: two regions defined by chemical composition, five distinguished by structural features, and three mechanically distinct regions. We identified three major components that lead to a robust interface between a soft tissue and bone: mobile collagen fiber units, a continuous interfacial region, and a local stiffness gradient. This tissue architecture allows for large displacements of collagen fibers in the attachments, enabling meniscal movement without localizing strains to the soft tissue-to-bone interface. The interplay of these regions reveals a method relying on hierarchical structuring across multiple length scales to minimize stress concentrators between highly dissimilar materials. These insights inspire new design strategies for synthetic soft tissue-to-bone attachments and biomimetic material interfaces.

Indirect 3D printing technology for the fabrication of customised β-TCP/chitosan scaffold with the shape of rabbit radial head-an in vitro study

Background

With the development of indirect three-dimensional (3D) printing technology, it is possible to customise individual scaffolds to be used in bone transplantation and regeneration. In addition, materials previously limited to the 3D printing (3DP) process due to their own characteristics can also be used well in indirect 3DP. In this study, customised β-TCP/chitosan scaffolds with the shape of rabbit radial head were produced by indirect 3D printing technology.

Methods

Swelling ability, porosity, mechanical characterisation, and degradation rate analysis were performed, and in vitro studies were also implemented to evaluate the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (MSCs) on the scaffolds. CCK8 cell proliferation assay kit and alkaline phosphatase (ALP) staining solution were used to study cell proliferation and early ALP content at the scaffold surface. Moreover, the osteogenic differentiation of MSCs on scaffolds was also evaluated through the scanning electron microscopy analysis.

Results

β-TCP/chitosan scaffold has good performance and degradation rate, and in vitro cell experiments also confirm that the scaffold has adequate cytocompatibility and bioactivity.

Conclusion

This study provides a promising new strategy for the design of customised scaffolds for the repair of complex damaged tissues.

Chitosan-based composite bilayer scaffold as an in vitro osteochondral defect regeneration model

Prolonged osteochondral tissue damage can result in osteoarthritis and decreased quality of life. Multiphasic scaffolds, where different layers model different microenvironments, are a promising treatment approach, yet stable joining between layers during fabrication remains challenging. Here, a bilayer scaffold for osteochondral tissue regeneration was fabricated using thermally-induced phase separation (TIPS). Two distinct polymer solutions were layered before TIPS, and the resulting porous, bilayer scaffold was characterized by seamless interfacial integration and a mechanical stiffness gradient reflecting the native osteochondral microenvironment. Chitosan is a critical component of both scaffold layers to facilitate cell attachment and the formation of polyelectrolyte complexes with other biologically relevant natural polymers. The articular cartilage region was optimized for hyaluronic acid content and stiffness, while the subchondral bone region was defined by higher stiffness and osteoconductive hydroxyapatite content. Following co-culture with chondrocyte-like (SW-1353 or mesenchymal stem cells) and osteoblast-like cells (MG63), cell proliferation and migration to the interface along with increased gene expression associated with relevant markers of osteogenesis and chondrogenesis indicates the potential of this bilayer scaffold for osteochondral tissue regeneration.

Synergistic Effects of Silicon/Zinc Doped Brushite and Silk Scaffolding in Augmenting the Osteogenic and Angiogenic Potential of Composite Biomimetic Bone Grafts

Cell instructive scaffolding platforms displaying synergistic effects by virtue of their chemical and physical cues have tremendous scope in modulating cell phenotype and thus improving the success of any graft. In this regard, we report here the development of Si- and Zn-doped brushite cement composited with silk scaffolding that hierarchically emulated the cancellous bone. The composite scaffolds fabricated exhibited an open porous network capable of enhanced osteoblast survival as attested by increased alkaline phosphatase activity and also sustaining osteoclast activity affirmed by tartrate resistant acid phosphatase staining. Moreover, the chemical cues presented by dissolutions products from the composite scaffold enabled the osteoblasts to secrete proangiogenic factors which favored better endothelial cell survival, confirmed through in vitro experiments. Moreover, the efficacy of these composite biomimetic scaffolds was validated in vivo in volumetric femur defects in rabbits, which revealed that these matrices influenced vascular cell infiltration and favored the formation of matured bony plate. Fluorochrome labeling studies and microtomography analysis revealed that at the end of three months, the implanted composite scaffolds had completely resorbed, leaving behind neo-osseous tissue and vouching for clinical translation of these composite matrices as viable and affordable bone-graft substitutes.

Conductive regenerated silk-fibroin-based hydrogels with integrated high mechanical performances

Strong and tough RSF-based hydrogels that could be used as a strain sensor, a touch screen pen and an electronic skin were developed.

Hydroxyapatite nanowire/collagen elastic porous nanocomposite and its enhanced performance in bone defect repair

The synthetic bone grafts that mimic the composition and structure of human natural bone exhibit great potential for application in bone defect repair. In this study, a biomimetic porous nanocomposite consisting of ultralong hydroxyapatite nanowires (UHANWs) and collagen (Col) with 66.7 wt% UHANWs has been prepared by the freeze drying process and subsequent chemical crosslinking. Compared with the pure collagen as a control sample, the biomimetic UHANWs/Col porous nanocomposite exhibits significantly improved mechanical properties. More significantly, the rehydrated UHANWs/Col nanocomposite exhibits an excellent elastic behavior. Moreover, the biomimetic UHANWs/Col porous nanocomposite has a good degradable performance with a sustained release of Ca and P elements, and can promote the adhesion and spreading of mesenchymal stem cells. The in vivo evaluation reveals that the biomimetic UHANWs/Col porous nanocomposite can significantly enhance bone regeneration compared with the pure collagen sample. After 12 weeks implantation, the woven bone and lamellar bone are formed throughout the entire UHANWs/Col porous nanocomposite, and connect directly with the host bone to construct a relatively normal bone marrow cavity, leading to successful osteointegration and bone reconstruction. The as-prepared biomimetic UHANWs/Col porous nanocomposite is promising for applications in various fields such as bone defect repair.

Fabrication of in vitro 3D mineralized tissue by fusion of composite spheroids incorporating biomineral-coated nanofibers and human adipose-derived stem cells

Development of a bone-like 3D microenvironment with stem cells has always been intriguing in bone tissue engineering. In this study, we fabricated composite spheroids by combining functionalized fibers and human adipose-derived stem cells (hADSCs), which were fused to form a 3D mineralized tissue construct. We prepared fragmented poly (ι-lactic acid) (PLLA) fibers approximately 100 μm long by partial aminolysis of electrospun fibrous mesh. PLLA fibers were then biomineralized with various concentrations of NaHCO₃ (0.005, 0.01, and 0.04 M) to form mineralized fragmented fibers (mFF1, mFF2, and mFF3, respectively). SEM analysis showed that the minerals in mFF2 and mFF3 completely covered the fiber surface, and surface chemistry analysis confirmed the presence of hydroxyapatite peaks. Additionally, mFFs formed composite spheroids with hADSCs, demonstrating that the cells were strongly attached to mFFs and homogeneously distributed throughout the spheroid. In vitro culture of spheroids in the media without osteogenic supplements showed significantly enhanced expression of osteogenic genes including Runx2 (20.83 ± 2.83 and 22.36 ± 2.18 fold increase), OPN (14.24 ± 1.71 and 15.076 ± 1.38 fold increase), and OCN (4.36 ± 0.41 and 5.63 ± 0.51 fold increase) in mFF2 and mFF3, respectively, compared to the no mineral fiber group. In addition, mineral contents were significantly increased at day 7. Blocking the biomineral-mediated signaling by PSB 603 significantly down regulated the expression of these genes in mFF3 at day 7. Finally, we fused composite spheroids to form a mineralized 3D tissue construct, which maintained the viability of cells and showed pervasively distributed minerals within the structure. Our composite spheroids could be used as an alternative platform for the development of in vitro bone models, in vivo cell carriers, and as building blocks for bioprinting 3D bone tissue.

STATEMENT OF SIGNIFICANCE

This manuscript described our recent work for the preparation of biomimeral-coated fibers that can be assembled with mesenchymal stem cells and provide bone-like environment for directed control over osteogenic differentiation. Biomineral coating onto synthetic, biodegradable single fibers was successfully carried out using multiple steps, combination of template protein coating inspired from mussel adhesion and charge-charge interactions between template proteins and mineral ions. The biomineral-coated single micro-scale fibers (1-2.5 μm in diameter) were then assembled with human adipose tissue derived stem cells (hADSCs). The assembled structure exhibited spheroidal architecture with few hundred micrometers. hADSCs within the spheroids were differentiated into osteogenic lineage in vitro and mineralized in the growth media. These spheroids were fused to form in vitro 3D mineralized tissue with larger size.

Hierarchically structured seamless silk scaffolds for osteochondral interface tissue engineering

The osteochondral healthcare market is driven by the increasing demand for affordable and biomimetic scaffolds. To meet this demand, silk fibroin (SF) from Bombyx mori and Antheraea assamensis is used to fabricate a biphasic scaffold, with fiber-free and fiber-reinforced phases, stimulating cartilage and bone revival. The fabrication is a facile reproducible process using single polymer (SF), for both phases, designed in a continuous and integrated manner. Physicochemical and mechanical scaffold characterization, display interconnected pores with differential swelling and tunable degradation. The compressive modulus values, extend to 40 kPa and 25%, for tensile strain, at elongation. The scaffold support, for growth and proliferation of chondrocytes and osteoblasts, for respective cartilage and bone regeneration, is verified from in vitro assessment. Up-regulation of alkaline phosphatase (ALP) activity, extracellular matrix secretion and gene expression are significant; with acceptable in vitro immune response. Upon implantation in rabbit osteochondral defects for 8 weeks, the histological and micro-CT examinations show biphasic scaffolds significantly enhance regeneration of cartilage and subchondral bone tissues, as compared to monophasic scaffolds. The regenerated bone mineral density (BMD) ranges from 600-700 mg hydroxyapatite (HA) per cm³. The results, therefore, showcase the critically positive characteristics of in vitro ECM deposition, and in vivo regeneration of osteochondral tissue by this hierarchically structured biphasic scaffold.

Characterizations of hyaluronate-based terpolymeric hydrogel synthesized via free radical polymerization mechanism for biomedical applications

In the present study, a novel terpolymeric hydrogel was developed using sodium hyaluronate (HA), 2-hydroxyethyl acrylate (2-HEA), and poly(ethylene glycol) diacrylate (PEGDA) via free radical polymerization for biomedical applications. To achieve elasticity, swelling ability, porous architecture and sufficient gel strength, hyaluronate was chemically modified by grafting and crosslinking methods using 2-HEA and PEGDA, respectively. The structure and compositions of the fabricated terpolymer (HA-g-p(2-HEA)-x-PEGDA) were verified by FTIR, ¹H HR-MAS-NMR, and TGA analyses. The surface morphology and cross-section of the hydrogel was detected by SEM analysis. The gel nature of terpolymer in aqueous medium at 37 °C was confirmed from swelling study, and rheological experiment. Non-cytotoxicity and biocompatibility of the HA-g-p(2-HEA)-x-PEGDA hydrogel were ascertained by in vitro mouse osteoblastic cells (MC3T3) proliferation, and viability studies. Hematoxylin and eosin Y, and Masson's trichrome stainings were performed to show tissue regeneration ability on the prepared hydrogel. In vitro release results of proangiogenic drug-dimethyloxalylglycine (DMOG), and antibiotics-tetracycline (TCN) showed sustained release behaviour from the prepared hydrogel under different pHs at 37 °C. The mathematical models fitted data imply that both DMOG and TCN release follow first order kinetics, while, the release mechanism is primarily controlled by diffusion as well as erosion process. Finally, the novel biocompatible HA-g-p(2-HEA)-x-PEGDA gel, which showed sustained drugs release, and regeneration ability of extracellular matrix and collagen, could be employed in biomedical applications, especially, for the delivery of DMOG/TCN, and in tissue engineering.

Biodegradable Multifunctional Bioactive Glass-Based Nanocomposite Elastomers with Controlled Biomineralization Activity, Real-Time Bioimaging Tracking, and Decreased Inflammatory Response

Controlled biomineralization activity of biomaterials is rather important in bone regeneration and osseointegration avoiding the formation of fibrous capsule. However, most of conventional biodegradable elastomeric biomaterials for bone regeneration do not possess biomineralization ability and inherent multifunctional properties. Herein, we report a multifunctional bioactive glass (BG)-based hybrid poly(citrate-siloxane) (PCS) elastomer with intrinsical biomineralization activity and photoluminescent properties for potential bone tissue regeneration. Monodispersed BG nanoparticles (BGNs) were used to control the elastomeric behavior, biomineralization activity, photoluminescent ability, and osteogenic cellular response of PCS elastomers. BGNs significantly enhanced the elastomeric modulus of PCS from 20 to 200 MPa (10 times improvement) and the hydrophilicity (from 82° to 28° in water contact angle). The photoluminescent properties of PCS elastomers were also tailored through the incorporation of BGNs. The in vivo degradation of PCS-BGN nanocomposites could be efficiently tracked through noninvasively monitoring their fluorescent change. PCS-BGN nanocomposites enhanced the proliferation and osteoblastic differentiation of osteoblasts (MC3T3-E1) and decreased the in vivo inflammatory response. This study provided a novel tactics for designing the bioactive elastomeric biomaterials with multifunctional properties for bone regeneration medicine.

Biomimetic Composite Scaffold Containing Small Intestinal Submucosa and Mesoporous Bioactive Glass Exhibits High Osteogenic and Angiogenic Capacity

Biomaterials with excellent osteogenic and angiogenic activities are desirable to repair massive bone defects. Decellularized matrix from porcine small intestinal submucosa (SIS) has attracted particular attention for tissue regeneration because it has strong angiogenic effects and retains plentiful bioactive components. However, it has inferior osteoinductivity and osteoconductivity. In this study, we developed porous composite of SIS combined with mesoporous bioactive glass (SIS/MBG) with the goal of improving the mechanical and biological properties. SIS/MBG scaffolds showed uniform interconnected macropores (∼150 μm), high porosity (∼76%), and enhanced compressive strength (∼0.87 MPa). The proliferation and osteogenic gene expression (Runx2, ALP, Ocn, and Col-Iα) of rat bone marrow stromal cells (rBMSCs) as well as the proliferation, angiogenic gene expression (VEGF, bFGF, and KDR), and tube formation capacity of human umbilical vein endothelial cells (HUVECs) in SIS/MBG scaffolds were significantly upregulated compared with nonmesoporous bioactive glass (BG)-modified SIS (SIS/BG) and SIS-only scaffolds. Western blot analysis revealed that SIS/MBG induced rBMSCs to osteogenic differentiation through the activation of Wnt/β-Catenin signaling pathway, and SIS/MBG enhanced angiogenic activity of HUVEC through the activation of PI3k/Akt pathways. The in vivo results demonstrated that SIS/MBG scaffolds significantly enhanced new bone formation and neovascularization simultaneously in critical-sized rat calvarial defects as compared with SIS/BG and SIS. Collectively, the osteostimulative and angiostimulative biomimetic composite scaffold SIS/MBG represents an exciting biomaterial option for bone regeneration.

Action of a deproteinized xenogenic biomaterial in the process of bone repair in rats submitted to inhalation of cigarette smoke

PURPOSE

To investigate if the inorganic bovine bone matrix changes the bone formation in rats submitted to inhalation of cigarette smoke.

METHODS

Twenty Wistar rats were divided into two groups: Cigarette Clot Group (CCG), which in the inhalation chamber received the smoke of 10 cigarettes, 3 times a day, 10 minutes, for 30 days and had the surgical cavity filled by clot; Cigarette Biomaterial Group (CBG), submitted to the same inhalation technique but with the cavity filled by biomaterial.

RESULTS

In CCG there was a significant difference of new bone tissue in the analyzed periods (15 and 45 days), and in 15 days, there was 4.8 ± 0.42 of bone formed and 11.73 ± 0.59 (p <0.05) in 45 days. The CBG also showed a significant difference between the periods of 15 to 45 days, being respectively 6.16 ± 0.30 and 11.60 ± 0.61. However, when the groups were compared, within the same analyzed periods, a significant difference was observed only in the period of 15 days, with the new bone percentage being greater in the CBG.

CONCLUSION

The bone matrix acted as an osteoinductive biomaterial, biocompatible and aided in the repair process, mainly in the initial period of recovery.

Multifunctional Cell Instructive Silk-Bioactive Glass Composite Reinforced Scaffolds Toward Osteoinductive, Proangiogenic, and Resorbable Bone Grafts

The successful regeneration of large volume bone defects necessitates the use of proangiogenic and resorbable scaffolding matrix. Impaired and slow ingrowth of host vasculature within implanted grafts greatly compromises its effective osseointegration. By addressing this, it is demonstrated that the use of copper doped bioactive glass functionalizes silk microfiber reinforcements to improve the physicochemical and osteoinductive properties of two silk scaffolding matrices (mulberry Bombyx mori and non-mulberry Antheraea assama) employed in the study. The reinforced composite matrices increase the surface area and present an open porous biomimetic micromillieu favoring stem cell and endothelial cell migration within the matrix. Biochemical results indicate the stabilization of hypoxia-inducible factor-1α and expression of C-X-C chemokine receptor type-4 in adipose derived human mesenchymal stem cells, which regulate the downstream proangiogenic signaling and endothelial cell homing, respectively. Osteoinduction, matrix turnover, and resorption effectiveness are favored better in the non-mulberry silk matrices. The composite matrices significantly promote neo-osseous tissue formation in volumetric femur defect in rabbits with periosteal restoration seen in the non-mulberry silk composite matrices. Evidences of total resorption, enhanced vascular-fibrous tissue ingrowth within the scaffold, vouch for the potential clinical translation of these developed composite silk matrices.

Guided osteoporotic bone regeneration with composite scaffolds of mineralized ECM/heparin membrane loaded with BMP2-related peptide

Introduction

At present, the treatment of osteoporotic defects poses a great challenge to clinicians, owing to the lower regeneration capacity of the osteoporotic bone as compared with the normal bone. The guided bone regeneration (GBR) technology provides a promising strategy to cure osteoporotic defects using bioactive membranes. The decellularized matrix from the small intestinal submucosa (SIS) has gained popularity for its natural microenvironment, which induces cell response.

Materials and methods

In this study, we developed heparinized mineralized SIS loaded with bone morphogenetic protein 2 (BMP2)-related peptide P28 (mSIS/P28) as a novel GBR membrane for guided osteoporotic bone regeneration. These mSIS/P28 membranes were obtained through the mineralization of SIS (mSIS), followed by P28 loading onto heparinized mSIS. The heparinized mSIS membrane was designed to improve the immobilization efficacy and facilitate controlled release of P28. P28 release from mSIS-heparin-P28 and its effects on the proliferation, viability, and osteogenic differentiation of bone marrow stromal stem cells from ovariectomized rats (rBMSCs-OVX) were investigated in vitro. Furthermore, a critical-sized OVX calvarial defect model was used to assess the bone regeneration capability of mSIS-heparin-P28 in vivo.

Results

In vitro results showed that P28 release from mSIS-heparin-P28 occurred in a controlled manner, with a long-term release time of 40 days. Moreover, mSIS-heparin-P28 promoted cell proliferation and viability, alkaline phosphatase activity, and mRNA expression of osteogenesis-related genes in rBMSCs-OVX without the addition of extra osteogenic components. In vivo experiments revealed that mSIS-heparin-P28 dramatically stimulated osteoporotic bone regeneration.

Conclusion

The heparinized mSIS loaded with P28 may serve as a potential GBR membrane for repairing osteoporotic defects.

Porous stable poly(lactic acid)/ethyl cellulose/hydroxyapatite composite scaffolds prepared by a combined method for bone regeneration

A major challenge in bone tissue engineering is the development of biomimetic scaffolds which should simultaneously meet mechanical strength and pore structure requirements. Herein, we combined technologies of high concentration solvent casting, particulate leaching, and room temperature compression molding to prepare a novel poly(lactic acid)/ethyl cellulose/hydroxyapatite (PLA/EC/HA) scaffold. The functional, structural and mechanical properties of the obtained porous scaffolds were characterized. The results indicated that the PLA/EC/HA scaffolds at the 20wt% HA loading level showed optimal mechanical properties and desired porous structure. Its porosity, contact angle, compressive yield strength and weight loss after 56days were 84.28±7.04%, 45.13±2.40°, 1.57±0.09MPa and 4.77±0.32%, respectively, which could satisfy the physiological demands to guide bone regeneration. Thus, the developed scaffolds have potential to be used as a bone substitute material for bone tissue engineering application.

In vitro study of novel microparticle based silk fibroin scaffold with osteoblast-like cells for load-bearing osteo-regenerative applications

Silk Fibroin microparticle scaffolds show promise in bone tissue engineering applications.