Preparation, characterization, degradation and biocompatibility of different silk fibroin based composite scaffolds prepared by freeze-drying method for tissue engineering application

Effect of surfactants on the interfacial viscoelasticity and stability of silk fibroin at different oil-water interfaces

BACKGROUND

The biocompatible amphiphilic silk fibroin, extracted from domesticated silkworms, can adsorb at the oil-water interface and form elastic interfacial layers. In this study, three surfactants (cationic cetyltrimethylammonium bromide, the nonionic polyoxyethylene sorbitan monolaurate, and the anionic sodium dodecyl sulfate) were selected to investigate, through interfacial shear rheology, the influences of surfactants on the interfacial viscoelasticity and stability of silk fibroin at the interfaces between water and two different oils.

RESULTS

The presence of surfactant prolongs the equilibration time and enhances the interfacial elastic modulus and toughness of the interfacial silk fibroin layers, especially at the nonpolar dodecane-water interface. However, when the surfactant exceeds a critical concentration, the shear modulus and stability of interfacial silk fibroin layers begin to decrease due to the competitive adsorption of surfactant molecules and the weakening of the protein network. Owing to electrostatic interactions, the ionic surfactants cetyltrimethylammonium bromide and sodium dodecyl sulfate can form more hydrophobic complexes with silk fibroin, which results in higher shear moduli than for silk fibroin and silk fibroin-polyoxyethylene sorbitan monolaurate mixture.

CONCLUSION

Both the surfactant type and oil polarity play important roles in the adsorption, shear viscoelasticity, and stability of silk fibroin at the oil-water interface. Enhanced interactions between a silk fibroin-surfactant mixture and the oil phase delay the equilibration of the adsorption layers but strengthen the stability of interfacial layers. © 2023 Society of Chemical Industry.

Ca-AlN MOFs-loaded chitosan/gelatin scaffolds; a dual-delivery system for bone tissue engineering applications

Creating a scaffold for bone tissue engineering that is bioactive and capable of acting as a local-dual delivery system, releasing bioactive molecules and regulating the bone remodeling process to achieve balanced bone resorption and formation, is a significant challenge. The objective of this research is to create a composite scaffold using chitosan/gelatin (CHS/Gel) and the calcium (Ca)-alendronate (ALN) metal-organic frameworks (MOFs). The scaffold will act as a dual-delivery system, releasing Ca ions and ALN to regulate bone formation. Ca-ALN MOF nanoparticles (NPs) were prepared in mild conditions and studied by FTIR, XRD, FESEM, and TGA. Ca-ALN NPs-loaded CHS/Gel scaffolds were opportunely fabricated through freeze-drying approach. Physicochemical features of the scaffolds after incorporating NPs equated by CHS/Gel scaffold changed, therefore, the attendance of NPs caused a decreasing porosity, decreased swelling, and low rate of degradation. The release profile results showed that the NPs-loaded CHS/Gel scaffolds were able to simultaneously release ALN and Ca ions due to the decomposition of NPs. Additionally, the loading of NPs in the CHS/Gel scaffold led to an increment in alkaline phosphatase (ALP) activity and the quantity of deposited Ca along with osteogenesis gene markers. These findings suggest that the NPs-loaded CHS/Gel scaffold has the potential to enhance the differentiation of human adipose tissue-derived mesenchymal stem cells, making it a promising approach for bone repair.

Chitosan scaffolds: Expanding horizons in biomedical applications

Chitosan, a natural polysaccharide from chitin, shows promise as a biomaterial for various biomedical applications due to its biocompatibility, biodegradability, antibacterial activity, and ease of modification. This review overviews "chitosan scaffolds" use in diverse biomedical applications. It emphasizes chitosan's structural and biological properties and explores fabrication methods like gelation, electrospinning, and 3D printing, which influence scaffold architecture and mechanical properties. The review focuses on chitosan scaffolds in tissue engineering and regenerative medicine, highlighting their role in bone, cartilage, skin, nerve, and vascular tissue regeneration, supporting cell adhesion, proliferation, and differentiation. Investigations into incorporating bioactive compounds, growth factors, and nanoparticles for improved therapeutic effects are discussed. The review also examines chitosan scaffolds in drug delivery systems, leveraging their prolonged release capabilities and ability to encapsulate medicines for targeted and controlled drug delivery. Moreover, it explores chitosan's antibacterial activity and potential for wound healing and infection management in biomedical contexts. Lastly, the review discusses challenges and future objectives, emphasizing the need for improved scaffold design, mechanical qualities, and understanding of interactions with host tissues. In summary, chitosan scaffolds hold significant potential in various biological applications, and this review underscores their promising role in advancing biomedical science.

Salivary Gland Bioengineering

Salivary gland dysfunction affects millions globally, and tissue engineering may provide a promising therapeutic avenue. This review delves into the current state of salivary gland tissue engineering research, starting with a study of normal salivary gland development and function. It discusses the impact of fibrosis and cellular senescence on salivary gland pathologies. A diverse range of cells suitable for tissue engineering including cell lines, primary salivary gland cells, and stem cells are examined. Moreover, the paper explores various supportive biomaterials and scaffold fabrication methodologies that enhance salivary gland cell survival, differentiation, and engraftment. Innovative engineering strategies for the improvement of vascularization, innervation, and engraftment of engineered salivary gland tissue, including bioprinting, microfluidic hydrogels, mesh electronics, and nanoparticles, are also evaluated. This review underscores the promising potential of this research field for the treatment of salivary gland dysfunction and suggests directions for future exploration.

The practical process of manufacturing poly(methyl methacrylate)-based scaffolds having high porosity and high strength

Poly(methyl methacrylate) (PMMA)-based scaffolds have been produced using the granule casting method with grain sizes M80-100 and M100-140. The novelty of this study was the application of the cold-cutting method (CCm) to reduce the PMMA granule size. PMMA granule shape, granule size (mesh), and sintering temperature were the primary variables in manufacturing PMMA scaffolds. CCm was applied to reduce the granule size of commercial PMMA, which was originally solid cylindrical, by lowering the temperature to 3.5 °C, 0 °C, and-8.3 °C. PMMA granules that had been reduced were sieved with mesh sizes M80-100 and M100-140. Green bodies were made by the granule casting method using an aluminum mold measuring 8 × 8 × 8 mm³. The sintering process was carried out at temperatures varying from 115 °C to 140 °C, a heating rate of 5 °C/min, and a holding time of 2 h, the cooling process was carried out in a furnace. The characterization of the PMMA-based scaffolds' properties was carried out by observing the microstructure with SEM, analyzing the distribution of pore sizes with ImageJ software, and testing the porosity, the phase, with XRD, and the compressive strength. The best results from the overall analysis were the M80-100 PMMA scaffold treated at a sintering temperature of 130 °C with compressive strength, porosity, and pore size distribution values of 8.2 MPa, 62.0%, and 121-399 μm, respectively, and the M100-140 one treated at a sintering temperature of 135 °C with compressive strength, porosity, and pore size distribution values of 12.1 MPa, 61.2%, and 140-366 μm, respectively. There were interconnected pores in the PMMA scaffolds, as evidenced by the SEM images. There was no PMMA phase change between before and after the sintering process.

Well-aligned three-dimensional silk fibroin protein scaffold for orientation regulation of cells

The similar characteristics of biomaterials to the extracellular matrix are essential for efficient tissue repair through dictating cell behaviors. But the scaffold fabrication with complex shapes and controlled alignment have proven to be a difficult task. Herein, a well-designed three-dimensional silk fibroin scaffold is fabricated through ice template technology. The effect of the silk fibroin protein concentration and the freezing temperature on the microstructure and mechanical properties of scaffolds are investigated systematically. Cells behavior mediated by the obtained silk fibroin scaffolds is detected. The results show that the protein concentration plays a vital role in microstructure and scaffold strength. A well-aligned scaffold can be obtained when silk fibroin solution is kept at 12 wt%, which holds the highest mechanical properties. The pore size can be further adjusted in the range of 5-80 µm by changing the freezing temperature from -60 to -196 °C. The well-oriented scaffold with the appropriate pore size of 10-20 µm has the best ability to guide cell alignment. The resulting scaffolds provide an excellent matrix to guide cells behaviors and have a potential application in tissue engineering.

Protein-inorganic hybrid porous scaffolds for bone tissue engineering

Porous scaffolds hold promise in the treatment of bone defects for bone tissue engineering due to their interconnected porous structure and suitable mechanical properties. Herein, LAPONITE® (LAP), which is able to promote osteogenic differentiation, was introduced into regenerated silk fibroin (RSF) porous scaffolds. Due to hydrogen bonding and electrostatic interactions between RSF and LAP, RSF/LAP 3D porous scaffolds were successfully prepared. The pore size, porosity, and mechanical properties of the RSF/LAP 3D porous scaffolds were modulated during the preparation process. Evaluation of the proliferation of bone marrow mesenchymal stem cells (BMSCs) on the RSF/LAP 3D porous scaffolds in vitro indicated that the addition of LAP improved the adhesion and proliferation of cells. Additionally, alkaline phosphatase activity and osteospecific gene expression analysis showed that the RSF/LAP 3D porous scaffolds enhanced the osteogenic differentiation of BMSCs compared to the pristine RSF porous scaffolds, especially with a higher LAP content. The subcutaneous implantation of the RSF/LAP 3D porous scaffolds in rats demonstrated good histocompatibility in vivo. Therefore, RSF/LAP 3D porous scaffolds with good biocompatibility and biodegradability have good application prospects in the field of bone tissue engineering.

Adsorption, Surface Viscoelasticity, and Foaming Properties of Silk Fibroin at the Air/Water Interface

Like other proteins, the natural silk fibroin (SF) extracted from domesticated silkworms can adsorb at the air/water interface and stabilize foam due to its amphiphilic character and surface activity. At the interface, the adsorbed SF molecules experience structural reorganization and form water-insoluble viscoelastic films, which protect foam bubbles from coalescence and rupture. The solution conditions, such as protein concentration, pH, and additives, have significant influences on the molecular adsorption, layer thickness, interfacial mechanical strength, and, thus, on the foaming properties of SF. The understanding of the relationship between the interfacial adsorption, surface viscoelasticity, and foaming properties of SF is very important for the design, preparation, and application of SF foams in different fields.

Silk fibroin/cholinium gallate-based architectures as therapeutic tools

The combination of natural resources with biologically active biocompatible ionic liquids (Bio-IL) is presented as a combinatorial approach for developing tools to manage inflammatory diseases. Innovative biomedical solutions were constructed combining silk fibroin (SF) and Ch[Gallate], a Bio-IL with antioxidant and anti-inflammatory features, as freeze-dried 3D-based sponges. An evaluation of the effect of the Ch[Gallate] concentration (≤3% w/v) on the SF/Ch[Gallate] sponges was studied. Structural changes observed on the sponges revealed that the Ch[Gallate] presence positively affected the β-sheet formation while not influencing the silk native structure, which was suggested by the FTIR and solid-state NMR results, respectively. Also, it was possible to modulate their mechanical properties, antioxidant activity and stability/degradation in an aqueous environment, by changing the Ch[Gallate] concentration. The architectures showed high water uptake ability and a weight loss that follows the controlled Ch[Gallate] release rate studied for 7 days. Furthermore, the sponges supported human adipose stem cells growth and proliferation, up to 7 days. TNF-α, IL-6 (pro-inflammatory) and IL-10 (anti-inflammatory) release quantification from a human monocyte cell line revealed a decrease in the pro-inflammatory cytokines concentrations in samples containing Ch[Gallate]. These outcomes encourage the use of the developed architectures as tissue engineering solutions, potentially targeting inflammation processes. STATEMENT OF SIGNIFICANCE: Combining natural resources with active biocompatible ionic liquids (Bio-IL) is herein presented as a combinatorial approach for the development of tools to manage inflammatory diseases. We propose using silk fibroin (SF), a natural protein, with cholinium gallate, a Bio-IL, with antioxidant and anti-inflammatory properties, to construct 3D-porous sponges through a sustainable methodology. The morphological features, swelling, and stability of the architectures were controlled by Bio-IL content in the matrices. The sponges were able to support human adipose stem cells growth and proliferation, and their therapeutic effect was proved by the blockage of TNF-α from activated and differentiated THP-1 monocytes. We believe that these bio-friendly and bioactive SF/Bio-IL-based sponges are effective for targeting pathologies with associated inflammatory processes.

Nano-hydroxyapatite incorporated quince seed mucilage bioscaffolds for osteogenic differentiation of human adipose-derived mesenchymal stem cells

In this study, the therapeutic hydrocolloid quince seed mucilage (QSM) from Cydonia oblonga Miller fruit is enriched with needle-like nano-hydroxyapatite (nHAp) crystals to fabricate a novel biomimetic osteogenic bioscaffold. The molecular weight (M_w) of water-based extracted QSM was measured with GPC (8.67 × 10⁵ g/mol), and the composite blend was prepared at a ratio of 1:1 (w/w) QSM_aq and nHAp. The porous bioscaffolds were manufactured by the freeze-drying method, and evaluated in-depth with advanced analyses. The XRD, ATR-FTIR, SEM-EDX, and elemental mapping analyses revealed a uniform coated semi-crystalline structure with no covalent bindings between QSM and nHAp. Moreover, due to the hydrocolloid backbone, a supreme swelling ratio (w/w, 6523 ± 190%) with suitable pore size (208.12 ± 99.22 μm) for osteogenic development was obtained. Further, the cytocompatible bioscaffolds were evaluated for osteogenic differentiation in vitro using human adipose-derived mesenchymal stem cells (hAMSCs). The immuno/histochemical (I/HC) staining revealed that the cells with the spherical morphology invaded the pores of the prepared bioscaffolds. Also, relatively early up-regulated osteogenic markers were observed by the qRT-PCR analyses. Overall, it is believed that the QSM-nHAp bioscaffolds might be favorable in non-load bearing applications, especially in the cranio-maxillofacial region, due to their regenerative, bendable, and durable features.

A new cancellous bone material of silk fibroin/cellulose dual network composite aerogel reinforced by nano-hydroxyapatite filler

Composites materials comprised of biopolymeric aerogel matrices and inorganic nano-hydroxyapatite (n-HA) fillers have received considerable attention in bone engineering. Although with significant progress in aerogel-based biomaterials, the brittleness and low strengths limit the application. The improvements in toughness and mechanical strength of aerogel-based biomaterials are in great need. In this work, an alkali urea system was used to dissolve, regenerate and gelate cellulose and silk fibroin (SF) to prepare composite aerosol. A dual network structure was shaped in the composite aerosol materials interlaced by sheet-like SF and reticular cellulose wrapping n-HA on the surface. Through uniaxial compression, the density of the composite aerogel material was close to the one of natural bone, and mechanical strength and toughness were high. Our work indicates that the composite aerogel has the same mechanical strength range as cancellous bone when the ratio of cellulose, n-HA and SF being 8:1:1. In vitro cell culture showed HEK-293T cells cultured on composite aerogels had high ability of adhesion, proliferation and differentiation. Totally, the presented biodegradable composite aerogel has application potential in bone tissue engineering.

Investigation on hydrogen bonds and conformational changes in protein/polysaccharide/ceramic based tri-component system

The main attention of present work is to study the molecular level interactions in the interface of biocomposite to increase their applicability. A specific kind of molecular interaction namely, hydrogen bonds play a vital role in deciding composite property. In this study, we construct a tri-component system based on silk fibroin/sodium alginate/hydroxyapatite by varying protein and polysaccharide proportions using in-situ co-precipitation method. The Fourier Transfer Infrared (FTIR) prediction state that prepared composite exhibit inter-(OH⋯N, OH⋯O, OH⋯π) and intra-(OH⋯OH) molecular hydrogen bonds and their strength are varied in accordance with composition of composite. During composite preparation, conformational changes from the random coil to β-sheet structure through intermediate β-turns exist within the protein molecule that is confirmed by vibrational spectra. The crystallographic profile and morphology of HAP were greatly influenced by virtue of polymer matrix. Simulated body fluid (SBF) immersion study shows that biodegradation and swelling ratio are correlated with type of hydrogen bond and secondary structure of protein. Moreover, the in-vitro biomineralization, cytotoxicity and antibacterial activity of composite were analysed in detail.

3D printing of biomedically relevant polymer materials and biocompatibility

ABSTRACT

Research on polymer materials for additive manufacturing technology in biomedical applications is as promising as it is numerous, but biocompatibility of printable materials still remains a big challenge. Changes occurring during the 3D-printing processes itself may have adverse effects on the compatibility of the completed print. This prospective will put emphasis on the different additives and processes that can have a direct impact on biocompatibility during and after 3D printing of polymer materials.

A. M. N, Halim AS, Kumar USU, Bairwan R, Suriani AB. A Review on Micro- to Nanocellulose Biopolymer Scaffold Forming for Tissue Engineering Applications

Biopolymers have been used as a replacement material for synthetic polymers in scaffold forming due to its biocompatibility and nontoxic properties. Production of scaffold for tissue repair is a major part of tissue engineering. Tissue engineering techniques for scaffold forming with cellulose-based material is at the forefront of present-day research. Micro- and nanocellulose-based materials are at the forefront of scientific development in the areas of biomedical engineering. Cellulose in scaffold forming has attracted a lot of attention because of its availability and toxicity properties. The discovery of nanocellulose has further improved the usability of cellulose as a reinforcement in biopolymers intended for scaffold fabrication. Its unique physical, chemical, mechanical, and biological properties offer some important advantages over synthetic polymer materials. This review presents a critical overview of micro- and nanoscale cellulose-based materials used for scaffold preparation. It also analyses the relationship between the method of fabrication and properties of the fabricated scaffold. The review concludes with future potential research on cellulose micro- and nano-based scaffolds. The review provides an up-to-date summary of the status and future prospective applications of micro- and nanocellulose-based scaffolds for tissue engineering.

Influence of pH on the surface and foaming properties of aqueous silk fibroin solutions

Silk fibroin (SF) adsorbs at the air/water interface, reduces the surface tension, and forms interfacial layers suppressing bubble coalescence and stabilizing foam. Variation of pH alters the inter-molecular interactions of SF in the interfacial layers and thus interfacial network formation, dilatational visco-elasticity and foaming properties. At pH 4, around the isoelectric point, the reduced electrostatic repulsion between the SF molecules results in thicker adsorbed layers, but adsorption rate, foaming rate and foam stability are lower than at pH 3 and pH 7. At the highest pH investigated (pH 7), the small aggregate size and high protein flexibility lead to the formation of more ordered and stable viscoelastic interfacial networks, which are resistant to deformation breakage and generate homogeneous, denser and more stable foams.

Design and fabrication of clinoptilolite-nanohydroxyapatite/chitosan-gelatin composite scaffold and evaluation of its effects on bone tissue engineering

The aim of this study was to synthesize an innovative composite scaffold, which structured of clinoptilolite-nanohydroxyapatite/chitosan-gelatin (CLN-nHA/CS-G) with enhanced attributes for utilization in the bone tissue engineering. This composite scaffold was prepared by blending the CLN, nHA, chitosan, and gelatin solution followed by a freeze-drying step. The fabricated composite scaffolds were studied using BET, FTIR, XRD, and SEM techniques. The highly porous composite scaffolds with a pore size of 200 ± 100 μm were synthesized. Moreover, the effects of CLN and nHA on the physicochemical features of the scaffold such as density, swelling ratio, biomineralization, biodegradation, and mechanical behavior were studied. Compared with CS-G scaffold, the presence of CLN and nHA leads to an increased surface area, increased biomineralization, and low rate of degradation in simulated body fluid solution (SBF) and mechanical strength. Cytotoxicity of the CLN-nHA/CS-G scaffold was studied by MTT assay on human dental pulp stem cells (h-DPSCs). The biological response of h-DPSCs showed no toxicity and studied cells proliferated and attached on the pore surfaces of the scaffold. Results indicated that introducing CLN and nHA to composite improves the scaffold characteristics in a way that makes it suitable for bone tissue engineering.

Silk fibroin/sodium alginate composite porous materials with controllable degradation

In this study, silk fibroin (SF)/sodium alginate (SA) porous materials (PMs) with different blend ratios were generated using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as crosslinking agent by a simple freeze-dried method. Degradation experiment of SF/SA PMs have been systematically investigated up to 18 days in Collagenase IA solution at 37 °C, Phosphate buffer saline (PBS) solution without enzyme was used as a control. The results showed SF/SA 50/50 PMs exhibited a lowest rate of weight loss, about 68% of the weight retained within 18 d in Collagenase IA solution. SEM images indicated Collagenase IA can degrade fibroin leading to collapse of the pure SF PMs, while SF/SA 50/50 PMs still possessed integrity of pore structure during enzyme degradation with increasing exposure time. The crystalline structure of the SF in the SF/SA PMs changed to silk II after degradation for 18 d. Furthermore, the results of the in vivo degradation by subcutaneous implantation in rats showed that all PMs can be degraded at different levels, and exhibited good subcutaneous histocompatibility to the host animals. The degradability was strongly correlated to the blend ratios in a series of SF/SA composite PMs, and insights gained in this study can serve as a guide to match desired degradation behavior with specific applications for the SF/SA composite PMs.

Biomechanical properties of 3D-printed bone models

Bone lesions resulting from large traumas or cancer resections can be successfully treated by directly using synthetic materials or in combination with tissue engineering methods (hybrid). Synthetic or hybrid materials combined with bone tissue's natural ability for regeneration and biological adaptation to the directions of loading, allow for full recovery of its biological functions. Increasing interest in new production methods or various types of regenerative membranes and shaped scaffolds means that methods such as additive manufacturing can significantly accelerate the preparation of constructs used in the further biological adaptation of natural tissue. The porosity that allows not only ingrowth of the natural tissue, but also the ability of the synthetic material to transfer loadings in the skeletal system during the regeneration interval, will have a significant impact on regenerative capacities. This work presents the results of preliminary analyzes of bone models in the field of mechanical strength for monotonically and cyclically loading conditions. The determined material constants, such as ultimate tensile strength, Young modulus, and toughness or fatigue life, can be used in numerical simulations of new membranes for the regeneration of damaged bone tissue.

Optimal biomaterials for tracheal epithelial grafts: An in vitro systematic comparative analysis

Tracheal injury, stenosis, and malignancy demand tracheal reconstruction, which often fails due to the lack of a functioning epithelium. We performed an extensive comparative analysis to determine optimal biomaterials for developing tracheal epithelial grafts with mucociliary function. We screened Hyaluronan-Poly(Ethylene Glycol), Chitosan-Collagen, Collagen Vitrigel Membrane, Fibrin Glue, Silk Fibroin, and Gelatin based on various parameters including mechanical strength, bulk degradation, cell attachment, spreading, metabolic activity, focal adhesion formation, and differentiation into ciliated and goblet cells. Silk Fibroin had significantly higher tensile strength (21.23 ± 4.42 MPa), retained 50% of its mass across 5 weeks, allowed 80-100% cell spreading and increasing metabolic activity across 10 days, focal adhesion formation within 2 h, and differentiation into 5.9 ± 2.6% goblet cells. Silk Fibroin, however, led to poor ciliation, producing 5.5 ± 3.9% ciliated cells, whereas Collagen Vitrigel Membrane promoted excellent ciliation. To capitalize on the mechanical and differentiation benefits of its respective components, we developed a composite biomaterial of Silk Fibroin and Collagen Vitrigel Membrane (SF-CVM), which demonstrated enhanced maturation into 20.6 ± 1.7% ciliated and 5.6 ± 1.0% goblet cells. Development of biomaterials-based airway epithelial grafts that provide desirable mechanics and differentiation is a major step towards treatment of airway disease. STATEMENT OF SIGNIFICANCE: Tracheal blockage, injury, and malignancy greater than 50% of the adult tracheal length cannot be safely resected. Tracheal replacement is one approach, but a major cause of transplant failure is the lack of a functioning epithelium. While tissue engineering for tracheal regeneration using biomaterials is promising, there is currently no gold standard. Therefore, we performed a systematic comparative study to characterize relevant materials for generating a biomaterials-based airway epithelial graft. We developed a composite biomaterial intended for surgical implantation providing tensile strength, slow biodegradation, and optimal support for differentiation of mature epithelia. This is a significant step augmenting current state-of-the-art methods for airway surgeries, laryngeal reconstruction, and tracheal tissue engineering.

Synthesis, characterization and in vitro screening of a nano-hydroxyapatite/chitosan/Euryale ferox nanoensemble – an inimitable approach for bone tissue engineering

In order to explore novel synthetic bone scaffolds, a biomimmetic, osteoinductive, tricomposite scaffold has been synthesized incorporating Euryale ferox (EF) with nano-hydroxyapatite and chitosan.

Increased stem cells delivered using a silk gel/scaffold complex for enhanced bone regeneration

The low in vivo survival rate of scaffold-seeded cells is still a challenge in stem cell-based bone regeneration. This study seeks to use a silk hydrogel to deliver more stem cells into a bone defect area and prolong the viability of these cells after implantation. Rat bone marrow stem cells were mingled with silk hydrogels at the concentrations of 1.0 × 10⁵/mL, 1.0 × 10⁶/mL and 1.0 × 10⁷/mL before gelation, added dropwise to a silk scaffold and applied to a rat calvarial defect. A cell tracing experiment was included to observe the preservation of cell viability and function. The results show that the hydrogel with 1.0 × 10⁷/mL stem cells exhibited the best osteogenic effect both in vitro and in vivo. The cell-tracing experiment shows that cells in the 1.0 × 10⁷ group still survive and actively participate in new bone formation 8 weeks after implantation. The strategy of pre-mingling stem cells with the hydrogel had the effect of delivering more stem cells for bone engineering while preserving the viability and functions of these cells in vivo.