Bioactive apatite incorporated alginate microspheres with sustained drug-delivery for bone regeneration application

Hydrogel Microparticles for Bone Regeneration

Hydrogel microparticles (HMPs) stand out as promising entities in the realm of bone tissue regeneration, primarily due to their versatile capabilities in delivering cells and bioactive molecules/drugs. Their significance is underscored by distinct attributes such as injectability, biodegradability, high porosity, and mechanical tunability. These characteristics play a pivotal role in fostering vasculature formation, facilitating mineral deposition, and contributing to the overall regeneration of bone tissue. Fabricated through diverse techniques (batch emulsion, microfluidics, lithography, and electrohydrodynamic spraying), HMPs exhibit multifunctionality, serving as vehicles for drug and cell delivery, providing structural scaffolding, and functioning as bioinks for advanced 3D-printing applications. Distinguishing themselves from other scaffolds like bulk hydrogels, cryogels, foams, meshes, and fibers, HMPs provide a higher surface-area-to-volume ratio, promoting improved interactions with the surrounding tissues and facilitating the efficient delivery of cells and bioactive molecules. Notably, their minimally invasive injectability and modular properties, offering various designs and configurations, contribute to their attractiveness for biomedical applications. This comprehensive review aims to delve into the progressive advancements in HMPs, specifically for bone regeneration. The exploration encompasses synthesis and functionalization techniques, providing an understanding of their diverse applications, as documented in the existing literature. The overarching goal is to shed light on the advantages and potential of HMPs within the field of engineering bone tissue.

Recent developments in natural biopolymer based drug delivery systems

Targeted delivery of drug molecules to diseased sites is a great challenge in pharmaceutical and biomedical sciences. Fabrication of drug delivery systems (DDS) to target and/or diagnose sick cells is an effective means to achieve good therapeutic results along with a minimal toxicological impact on healthy cells. Biopolymers are becoming an important class of materials owing to their biodegradability, good compatibility, non-toxicity, non-immunogenicity, and long blood circulation time and high drug loading ratio for both macros as well as micro-sized drug molecules. This review summarizes the recent trends in biopolymer-based DDS, forecasting their broad future clinical applications. Cellulose chitosan, starch, silk fibroins, collagen, albumin, gelatin, alginate, agar, proteins and peptides have shown potential applications in DDS. A range of synthetic techniques have been reported to design the DDS and are discussed in the current study which is being successfully employed in ocular, dental, transdermal and intranasal delivery systems. Different formulations of DDS are also overviewed in this review article along with synthesis techniques employed for designing the DDS. The possibility of these biopolymer applications points to a new route for creating unique DDS with enhanced therapeutic qualities for scaling up creative formulations up to the clinical level.

Casein-Coated Molybdenum Disulfide Nanosheets Augment the Bioactivity of Alginate Microspheres for Orthopedic Applications

Defects and disorders of the bone due to disease, trauma, or abnormalities substantially affect a person's life quality. Research in bone tissue engineering is motivated to address these clinical needs. The present study demonstrates casein-mediated liquid exfoliation of molybdenum disulfide (MoS₂) and its coupling with alginate to create microspheres to engineer bone graft substitutes. Casein-exfoliated nano-MoS₂ was chemically characterized using different analytical techniques. The UV-visible spectrum of nano-MoS₂-2 displayed strong absorption peaks at 610 and 668 nm. In addition, the XPS spectra confirmed the presence of the molybdenum (Mo, 3d), sulfur (S, 2p), carbon (C, 1s), oxygen (O, 1s), and nitrogen (N, 1s) elements. The exfoliated MoS₂ nanosheets were biocompatible with the MG-63, MC3T3-E1, and C2C12 cells at 250 μg/mL concentration. Further, microspheres were created using alginate, and they were characterized physiochemically and biologically. Stereomicroscopic images showed that the microspheres were spherical with an average diameter of 1 ± 0.2 mm. The dispersion of MoS₂ in the alginate matrix was uniform. The alginate-MoS₂ microspheres promoted apatite formation in the SBF (simulated body fluid) solution. Moreover, the alginate-MoS₂ was biocompatible with MG-63 cells and promoted cell proliferation. Higher alkaline phosphatase activity and mineralization were observed on the alginate-MoS₂ with the MG-63 cells. Hence, the developed alginate-MoS₂ microsphere could be a potential candidate for a bone graft substitute.

Alginate-based Composites Microspheres: Preparations and Applications for Bone Tissue Engineering

Alginate-based biomaterials have been extensively studied for bone tissue engineering. Scaffolds, microspheres, and hydrogels can be developed using alginate, which is biocompatible, biodegradable, and able to deliver growth factors and drugs. Alginate microspheres can be produced using crosslinking, microfluidic, three-dimensional printing, extrusion, and emulsion methods. The sizes of the alginate microspheres range from 10 µm to 4 mm. This review describes the chemical characterization and mechanical assessment of alginate-based microspheres. Combinations of alginate with hydroxyapatite, chitosan, collagen, polylactic acid, polycaprolactone, and bioglass were discussed for bone tissue repair and regeneration. In addition, alginate combinations with bone morphogenetic proteins, vascular endothelial growth factor, transforming growth factor beta-3, other growth factors, cells, proteins, drugs, and osteoinductive drugs were analyzed for tissue engineering applications. Furthermore, the biocompatibility of developed alginate microspheres was discussed for different cell lines. Finally, alginate microsphere-based composites with stem cell interaction for bone tissue regeneration were presented. In the present review, we have assessed the preclinical research on in vivo models of alginate-based microspheres for bone tissue repair and regeneration. Overall, alginate-based microspheres are potential candidates for graft substitutes and the treatment of various bone-related diseases.

Porous Composite Granules with Potential Function of Bone Substitute and Simvastatin Releasing System: A Preliminary Study

In this work, 3D porous granules based on Zn and Se-containing calcium phosphates (CaPs) were fabricated using a droplet-extrusion technique. The composite beads varied in composition and contained two different natural polymers: sodium alginate (SA) and gelatin (GEL). To analyse and compare their physicochemical properties, such as porosity and morphology, different techniques were applied, including scanning electron microscopy (SEM), sorption of N2 and mercury porosimetry. Prior to the fabrication of the granules, the properties of CaPs materials, (the bioceramic base of the beads), selenium (IV)-substituted hydroxyapatite (Se-HA) and zinc-substituted dicalcium phosphate dihydrate (Zn-DCPD), were also investigated. The results of cell viability assessment showed that Se-HA powder was non-toxic to human osteoblasts (hFOB 1.19) and simultaneously exhibited high toxicity to tumour cells (Saos-2). Once the cytotoxicity assay was completed, Se-HA and Zn-DCPD were used to prepare 3D materials. The prepared porous granules were used as matrices to deliver simvastatin to bones. Simvastatin was applied in either the lipophilic form or hydrophilic form. The release kinetics of simvastatin from granules of different composition was then assessed and compared.

Degradation-Dependent Controlled Delivery of Doxorubicin by Glyoxal Cross-Linked Magnetic and Porous Chitosan Microspheres

Glyoxal cross-linked porous magnetic chitosan microspheres, GMS (∼170 μm size), with a tunable degradation profile were synthesized by a water-in-oil emulsion technique to accomplish controlled delivery of doxorubicin (DOX), a chemotherapeutic drug, to ensure prolonged chemotherapeutic effects. The GMS exhibit superparamagnetism with saturation magnetization, M s = 7.2 emu g-1. The in vitro swelling and degradation results demonstrate that a swelling plateau of GMS is reached at 24 h, while degradation can be modulated to begin at 96-120 h by formulating the cross-linked network using glyoxal. MTT assay, live/dead staining, and F-actin staining (actin/DAPI) validated the cytocompatibility of GMS, which further assured good drug loading capacity (35.8%). The release mechanism has two stages, initiated by diffusion-inspired release of DOX through the swollen polymer network (72 h), which is followed by a disintegration-tuned release profile (>96 h) conferring GMS a potential candidate for DOX delivery.

Nanofiber-Mâché Hollow Ball Mimicking the Three-Dimensional Structure of a Cyst

The occasional malignant transformation of intracranial epidermoid cysts into squamous cell carcinomas remains poorly understood; the development of an in vitro cyst model is urgently needed. For this purpose, we designed a hollow nanofiber sphere, the "nanofiber-mâché ball." This hollow structure was fabricated by electrospinning nanofiber onto alginate hydrogel beads followed by dissolving the beads. A ball with approximately 230 mm3 inner volume provided a fibrous geometry mimicking the topography of the extracellular matrix. Two ducts located on opposite sides provided a route to exchange nutrients and waste. This resulted in a concentration gradient that induced oriented migration, in which seeded cells adhered randomly to the inner surface, formed a highly oriented structure, and then secreted a dense web of collagen fibrils. Circumferentially aligned fibers on the internal interface between the duct and hollow ball inhibited cells from migrating out of the interior, similar to a fish bottle trap. This structure helped to form an adepithelial layer on the inner surface. The novel nanofiber-mâché technique, using a millimeter-sized hollow fibrous scaffold, is excellently suited to investigating cyst physiology.

Alginate and alginate composites for biomedical applications

Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as Azotobacter sp. and Pseudomonas sp. Owing to alginate gel forming capability, it is widely used in food, textile and paper industries; and to a lesser extent in biomedical applications as biomaterial to promote wound healing and tissue regeneration. This is evident from the rising use of alginate-based dressing for heavily exuding wound and their mass availability in the market nowadays. However, alginate also has limitation. When in contact with physiological environment, alginate could gelate into softer structure, consequently limits its potential in the soft tissue regeneration and becomes inappropriate for the usage related to load bearing body parts. To cater this problem, wide range of materials have been added to alginate structure, producing sturdy composite materials. For instance, the incorporation of adhesive peptide and natural polymer or synthetic polymer to alginate moieties creates an improved composite material, which not only possesses better mechanical properties compared to native alginate, but also grants additional healing capability and promote better tissue regeneration. In addition, drug release kinetic and cell viability can be further improved when alginate composite is used as encapsulating agent. In this review, preparation of alginate and alginate composite in various forms (fibre, bead, hydrogel, and 3D-printed matrices) used for biomedical application is described first, followed by the discussion of latest trend related to alginate composite utilization in wound dressing, drug delivery, and tissue engineering applications.

Assessment of the Release of Vascular Endothelial Growth Factor from 3D-Printed Poly-ε-Caprolactone/Hydroxyapatite/Calcium Sulfate Scaffold with Enhanced Osteogenic Capacity

Vascular endothelial growth factor (VEGF) is one of the most crucial growth factors and an assistant for the adjustment of bone regeneration. In this study, a 3D scaffold is fabricated using the method of fused deposition modeling. Such a fabricated method allows us to fabricate scaffolds with consistent pore sizes, which could promote cellular ingrowth into scaffolds. Therefore, we drafted a plan to accelerate bone regeneration via VEGF released from the hydroxyapatite/calcium sulfate (HACS) scaffold. Herein, HACS will gradually degrade and provide a suitable environment for cell growth and differentiation. In addition, HACS scaffolds have higher mechanical properties and drug release compared with HA scaffolds. The drug release profile of the VEGF-loaded scaffolds showed that VEGF could be loaded and released in a stable manner. Furthermore, initial results showed that VEGF-loaded scaffolds could significantly enhance the proliferation of human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVEC). In addition, angiogenic- and osteogenic-related proteins were substantially increased in the HACS/VEGF group. Moreover, in vivo results revealed that HACS/VEGF improved the regeneration of the rabbit’s femur bone defect, and VEGF loading improved bone tissue regeneration and remineralization after implantation for 8 weeks. All these results strongly imply that the strategy of VEGF loading onto scaffolds could be a potential candidate for future bone tissue engineering.

Zr(IV) Coordination Chemistry for Cell-Repellent Alginate Coatings: The Effect of Surface Functional Groups

Surface modification using alginic acid and its salt, alginate (Alg), has attracted much attention owing to its potential applications in various fields, including tissue engineering, drug delivery, antiplatelet surface preparation, and energy-storage technologies. In these applications, efficient immobilization of Alg on the solid surface is required because the delamination of the surface-bound Alg eventually leads to a significant decrease in its function. Therefore, much effort has been made to introduce Alg onto solid surfaces in a stable manner. Despite recent advances, existing methods for immobilizing Alg on surfaces have some limitations: (i) derivatization of Alg is typically also required and (ii) these methods only function under specific reaction conditions. Herein, we report a Zr(IV)-mediated strategy to immobilize Alg on solid surfaces. We demonstrate efficient Alg grafting onto carboxyl-, catechol-, polydopamine-, and tannic acid-functionalized surfaces via Zr(IV)-mediated cross-linking reactions. This strategy yields Alg multilayers that suppress fibroblast and platelet adhesion onto the solid surfaces. Furthermore, we show that the Alg multilayers can be selectively constructed on specific sites of solid surfaces. Given its ease of use and the wide selection of available carboxyl polymers, the current strategy is expected to be a useful tool for preparing functional polymer films for various applications.

Silicon-calcium phosphate ceramics and silicon-calcium phosphate cements: Substrates to customize the release of antibiotics according to the idiosyncrasies of the patient

Bone substitutes based on calcium phosphates can be classified in two major groups: ceramics and cements. Both are biomaterials with excellent biocompatibility that have been studied as local delivery systems for drugs. This study aims to evaluate drug-release kinetics in silicon beta-tricalcium phosphate ceramics (Si-β-TCP) and in silicon calcium phosphate cements (Si-CPCs). We want to investigate if the differences in composition and in structure of the Si-β-TCP and the Si-CPC may influence for drug loading and in its release kinetics from the biomaterial. The results obtained indicate that all drug-loaded materials were efficient to tailor drug release kinetics and inhibited the growth of Staphylococcus aureus. The cements prepared with high concentrations of silicon (80% Si-CPC) present zero-order release kinetics, independent of the drug concentration loaded. Si-β-TCP and Si-CPC offer a simple technology that could serve to personalize the delivery of bioactive molecules according to each patient's needs in the treatment of bone conditions, not only limited to prophylaxis, but also for the treatment of bone infection.

Pre-Registration Assessment of Bone-Filling Products

The use of bone‐filling material to repair bone defects and fix implanted bone grafts is a developing area in medicine. Investigators can evaluate bone‐filling materials through use of several indices to make comparisons and to determine suitability for application in humans¹. However, it is quite difficult to transform their discovery into practical use, because the viability of the studied material might require examination of all aspects of properties. In addition, for a material to become a product, a complete procedure involving a declaration, registration, and approval is necessary. This article introduces the technical indices that the investigators and reporters should provide in their declaration and registration data to meet the relevant standards in China. The indices include physical and chemical properties, biocompatibility, biosecurity, pre‐clinical animal model tests, sterilization and disinfection, product duration, and packaging. Full consideration of all possible indices is crucial to realize the transformation from a designed product to a commercial medical device, which requires effective interaction between clinicians and engineers.

Sustainable Dual Release of Antibiotic and Growth Factor from pH-Responsive Uniform Alginate Composite Microparticles to Enhance Wound Healing

Hydrogel-based wound dressings provided a moist microenvironment and local release of bioactive molecules. Single drug loading along with fast release rates and usually in hydrogel sheets limited their performance. Hence, uniform alginate/CaCO₃ composite microparticles (∼430 μm) with tunable compositions for sustainable release of drug and pH-sensitivity were successfully fabricated using microfluidic technology. Due to the presence of CaCO₃ and the strong interactions with alginate molecules, lyophilized composite microparticles reverted to hydrogel state after rehydration. Regardless of microparticle states (hydrogel or lyophilized) and pH values (6.4 or 7.4), in vitro release rates of model drug were inversely related with CaCO₃ concentrations and much lower than that for pure alginate microparticles. The release rate at pH 6.4 (simulating wound microenvironment) was always slower than that at pH 7.4 for the same type of microparticles. Rifamycin and basic fibroblast growth factor (bFGF) were independently encapsulated into AD-5-R and AD-40-F to achieve a fast release of rifamycin and a slower, more sustained release of bFGF, respectively; CD-F-R was a mixture of AD-5-R and AD-40-F at weight ratio 1/1. For AD-5-R and CD-F-R, inhibition zones of S. aureus were observed until day 5, showing a sustained antibacterial property. On the basis of in vitro wound healing model of NIH-3T3 cell micropattern on glass coverslips with a hole array, it was found that AD-40-F and CD-F-R significantly promoted cell proliferation and migration rates. In a full-thickness skin wound model of rats, CD-F-R microparticles significantly accelerated wound healing with higher granulation tissue thickness and better bioactivity to stimulate angiogenesis than the control group. Furthermore, CD-F-R microparticles demonstrated a good biocompatibility and biodegradability in vivo. Taken together, CD-F-R composite microparticles may ideally meet the requirements for different stages during wound healing and demonstrated a good potential to be used as dressing materials.

Modifications of Polymeric Membranes Used in Guided Tissue and Bone Regeneration

Guided tissue/bone regeneration (GTR/GBR) is a widely used procedure in contemporary dentistry. To achieve the required results of tissue regeneration, soft tissues that reproduce quickly are separated from the slow-growing bone tissue by membranes. Many types of membranes are currently in use, but none of them fulfil all of the desired features. To address this issue, further research on developing new membranes with better separation characteristics, such as membrane modification, is needed. Many of the current innovative modified materials are still in the phase of in vitro and experimental studies. A collective review on new trends in membrane modification to GTR/GBR is needed due to the widespread use of polymeric membranes and the constant development in the field of dentistry. Therefore, the aim of this review was to present an overview of polymeric membrane modifications to the GTR/GBR reported in the literature. The authors searched databases, including PubMed, SCOPUS, Web of Science, and OVID, for relevant studies that were published during 1999-2019. The following keywords were used: guided tissue regeneration, membranes, coating, and modification. A total of 17 papers were included in this review. Furthermore, the articles were divided into three groups that were based on the type of membrane modification: antibiotic coating, ion-use modifications, and others modifications, thus providing an overview of current existing knowledge in the field and encouraging further research. The results of included studies on modified barrier membranes seem to be promising, both in terms of safety and benefits for patients. However, modifications result in a large spectrum of effects. Further clinical studies are needed on a large group of patients to clearly confirm the effects that were observed in animal and in vitro studies.

Preparation and evaluation of BCP-CSD-agarose composite microsphere for bone tissue engineering

Composite microspheres have been widely investigated over the years in order to achieve a sound scaffold with suitable combinations of biodegradable polymers and bioactive ceramics/glasses for bone tissue engineering. In our present study, composite microspheres were prepared for the first time by agarose (1 wt %) enforcement with combination of biphasic calcium phosphate (BCP; 20 wt %) and calcium sulfate dehydrate (CSD; 20 wt %), and analyzed for use in bone regeneration. The one-step fabrication process revealed spheres of sizes ranging from 50 to 1000 μm of BCP-CSD contents effectively formed by natural solidification of agarose matrix, which is very simple, time and cost-effective, and could allow for large scale production. Furthermore, the BCP-CSD-agarose composite microspheres were tested in in vitro and in vivo for bone-forming properties in order to assess their biocompatibility. The rapid diffusion of Ca ²⁺ ions from CSD of the composite microspheres through agarose matrix potentially increased interactivity with microenvironment and gave support for cell adhesion and proliferation. Moreover, in vivo result demonstrated that fabricated microspheres promoted neovascularization, stimulated fibroblast cell proliferation, and host cell migration occurred throughout the defects and within microspheres, ultimately guided to new bone formation. The developed composite microspheres with novel approach could have potential for bone regeneration application. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2263-2272, 2019.

Emerging Biomedical Applications of Algal Polysaccharides

BACKGROUND

Over the past two decades, there have been substantial progress and a growing body of research on using natural polymeric biomaterials in emerging biomedical applications. Among different natural biopolymers, polysaccharides have gained considerable attraction among biomedical scientists and surgeons due to their biocompatibility, biodegradability, anti-inflammatory, and antimicrobial properties. In recent years, algalbased polysaccharides including agar, alginate, and carrageenan, have been broadly suggested for different biomedical applications.

METHODS

The aim of this paper is discussing various possible applications of algal-based polysaccharides in biomedical engineering particularly in controlled drug delivery systems. The main properties of each algal polysaccharide will be discussed, and particular drug delivery applications will be presented.

RESULTS

Algal polysaccharides can be detected in a group of photosynthetic unite as their key biomass constituents. They provide a range of variety in their size, shape, liquefaction, chemical stability, and crosslinking ability. In addition, algal polysaccharides have shown exceptional gelling properties including stimuli-responsive behavior, softness, and swelling properties.

CONCLUSION

All the mentioned properties of alga polysaccharides lead to their successful usage in biomedical applications specially targeted and controlled drug delivery systems such as particles, capsules, and gels.

Dopamine-assisted fixation of drug-loaded polymeric multilayers to osteoarticular implants for tuberculosis therapy

Currently, the major issues in the treatment of osteoarticular tuberculosis (TB) after implant placement are low drug concentration at the infected focus and drug resistance resulting from the long-term chemotherapy. The application of drug-loaded polymeric multilayers on implantable devices offers a promising solution to the problems. Herein, a poly(ethylene glycol)-based hydrogel film embedded with isoniazid (INH)-loaded alginate microparticles was fixed to Ti implants via adhesive polydopamine, subsequently capped by poly(lactic-co-glycolic acid) membranes for the sustained and localized delivery of the anti-TB drug. The antibacterial efficacy of the released INH was confirmed by a 4.5 ± 0.8 cm inhibition zone formed in the fourth week after inoculation of Mycobacterium tuberculosis. The INH-loaded Ti implants showed no toxicity to the osteoblast cell and provided a consistent drug release for nearly one week in vitro. The release profile in vivo showed a high local concentration and low systemic exposure. The local INH concentration could be kept higher than its minimum inhibitory concentration over a period of 8 weeks, which proves that it is a promising strategy to improve the severe osteoarticular TB treatment.

Hydroxyapatite-polymer biocomposites for bone regeneration: A review of current trends

Bone tissue engineering has emerged as one of the most indispensable approaches to address bone trauma in the past few decades. This approach offers an efficient and a risk-free alternative to autografts and allografts by employing a combination of biomaterials and cells to promote bone regeneration. Hydroxyapatite (HA) is a ceramic biomaterial that mimics the mineral composition of bones and teeth in vertebrates. HA, commonly produced via several synthetic routes over the years has been found to exhibit good bioactivity, biocompatibility, and osteoconductivity under both in vitro and in vivo conditions. However, the brittle nature of HA restricts its usage for load bearing applications. To address this problem, HA has been used in combination with several polymers in the form of biocomposite implants to primarily improve its mechanical properties and also enhance the implants' overall performance by simultaneously exploiting the positive effects of both HA and the polymer involved in making the biocomposite. This review article summarizes the past and recent developments in the evolution of HA-polymer biocomposite implants as an "ideal" biomaterial scaffold for bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2046-2057, 2018.

Silk Fibroin-Alginate-Hydroxyapatite Composite Particles in Bone Tissue Engineering Applications In Vivo

The aim of this study was to evaluate the in vivo bone regeneration capability of alginate (AL), AL/hydroxyapatite (HA), and AL/HA/silk fibroin (SF) composites. Forty Sprague Dawley rats were used for the animal experiments. Central calvarial bone (diameter: 8.0 mm) defects were grafted with AL, AL/HA, or AL/HA/SF. New bone formation was evaluated by histomorphometric analysis. To demonstrate the immunocompatibility of each group, the level of tumor necrosis factor (TNF)-α expression was studied by immunohistochemistry (IHC) and quantitative reverse transcription polymerase chain reaction (qRT-PCR) at eight weeks post implantation. Additionally, osteogenic markers, such as fibroblast growth factor (FGF)-23, osteoprotegerin (OPG), and Runt-related transcription factor (Runx2) were evaluated by qPCR or IHC at eight weeks post implantation. The AL/HA/SF group showed significantly higher new bone formation than did the control group (p = 0.044) and the AL group (p = 0.035) at four weeks post implantation. Additionally, the AL/HA/SF group showed lower relative TNF-α mRNA levels and higher FGF-23 mRNA levels than the other groups did at eight weeks post implantation. IHC results demonstrated that the AL/HA/SF group had lower TNF-α expression and higher OPG and Runx2 expression at eight weeks post implantation. Additionally, no evidence of the inflammatory reaction or giant cell formation was observed around the residual graft material. We concluded that the AL/HA/SF composite could be effective as a scaffold for bone tissue engineering.

Engineering bone regeneration with novel cell-laden hydrogel microfiber-injectable calcium phosphate scaffold

Cell-based tissue engineering is promising to create living functional tissues for bone regeneration. The implanted cells should be evenly distributed in the scaffold, be fast-released to the defect and maintain high viability in order to actively participate in the regenerative process. Herein, we report an injectable calcium phosphate cement (CPC) scaffold containing cell-encapsulating hydrogel microfibers with desirable degradability that could deliver cells in a timely manner and maintain cell viability. Microfibers were synthesized using partially-oxidized alginate with various concentrations (0-0.8%) of fibrinogen to optimize the degradation rate of the alginate-fibrin microfibers (Alg-Fb MF). A fibrin concentration of 0.4% in Alg-Fb MF resulted in the greatest enhancement of cell migration, release and proliferation. Interestingly, a significant amount of cell-cell contact along the long-axis of the microfibers was established in Alg-0.4%Fb MF as early as day 2. The injectable tissue engineered construct for bone reconstruct was fabricated by mixing the fast-degradable Alg-0.4%Fb MF with CPC paste at 1:1 volume ratio. In vitro study showed that cells re-collected from the construct maintained good viability and osteogenic potentials. In vivo study demonstrated that the hBMSC-encapsulated CPC-MF tissue engineered construct displayed a robust capacity for bone regeneration. At 12weeks after implantation, osseous bridge in the rat mandibular defect was observed in CPC-MF-hBMSCs group with a new bone area fraction of (42.1±7.8) % in the defects, which was >3-fold that of the control group. The novel tissue-engineered construct presents an excellent prospect for a wide range of dental, craniofacial and orthopedic applications.