BMP-2 plasmid loaded PLGA/HAp composite scaffolds for treatment of bone defects in nude mice

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Driving Osteocytogenesis from Mesenchymal Stem Cells in Osteon-like Biomimetic Nanofibrous Scaffolds

The treatment of critical-sized bone defects caused by tumor removal, skeletal injuries, or infections continues to pose a major clinical challenge. A popular potential alternative solution to autologous bone grafts is a tissue-engineered approach that utilizes the combination of mesenchymal stromal/stem cells (MSCs) with synthetic biomaterial scaffolds. This approach aims to support new bone formation by mimicking many of the biochemical and biophysical cues present within native bone. Regrettably, osteocyte cells, crucial for bone maturation and homeostasis, are rarely produced within MSC-seeded scaffolds, thereby restricting the development of fully mature cortical bone from these synthetic implants. In this work, we have constructed a multimodal scaffold by combining electrospun poly(lactic-co-glycolic acid) (PLGA) fibrous scaffolds with poly(ethylene glycol) (PEG)-based hydrogels that mimic the functional unit of cortical bone, osteon (osteon-mimetic) scaffolds. These scaffolds were decorated with a novel bone morphogenic protein-6 (BMP6) peptide (BMP6p) after our findings revealed that the BMP6p drives higher levels of Smad signaling than the full-length protein counterpart, soluble or when bound to the PEG hydrogel backbone. We show that our osteon-mimetic scaffolds, in presenting concentric layers of BMP6p-PEG hydrogel overlaid on MSC-seeded PLGA nanofibers, promoted the rapid formation of osteocyte-like cells with a phenotypic dendritic morphology, producing early osteocyte markers, including E11/gp38 (E11). Maturation of these osteocyte-like cells was further confirmed by the observation of significant dentin matrix protein 1 (DMP1) throughout our bilayered scaffolds after 3 weeks, even when cultured in a medium without dexamethasone (DEX) or any other osteogenic supplements. These results demonstrate that these osteon-mimetic scaffolds, in presenting biochemical and topographical cues reminiscent of the forming osteon, can drive the formation of osteocyte-like cells in vitro from hBMSCs without the need for any osteogenic factor media supplementation.

Harnessing DNA origami's therapeutic potential for revolutionizing cardiovascular disease treatment: A comprehensive review

DNA origami is a cutting-edge nanotechnology approach that creates precise and detailed 2D and 3D nanostructures. The crucial feature of DNA origami is how it is created, which enables precise control over its size and shape. Biocompatibility, targetability, programmability, and stability are further advantages that make it a potentially beneficial technique for a variety of applications. The preclinical studies of sophisticated programmable nanomedicines and nanodevices that can precisely respond to particular disease-associated triggers and microenvironments have been made possible by recent developments in DNA origami. These stimuli, which are endogenous to the targeted disorders, include protein upregulation, pH, redox status, and small chemicals. Oncology has traditionally been the focus of the majority of past and current research on this subject. Therefore, in this comprehensive review, we delve into the intricate world of DNA origami, exploring its defining features and capabilities. This review covers the fundamental characteristics of DNA origami, targeting DNA origami to cells, cellular uptake, and subcellular localization. Throughout the review, we emphasised on elucidating the imperative for such a therapeutic platform, especially in addressing the complexities of cardiovascular disease (CVD). Moreover, we explore the vast potential inherent in DNA origami technology, envisioning its promising role in the realm of CVD treatment and beyond.

Nanofibers in Ocular Drug Targeting and Tissue Engineering: Their Importance, Advantages, Advances, and Future Perspectives

Nanofibers are frequently encountered in daily life as a modern material with a wide range of applications. The important advantages of production techniques, such as being easy, cost effective, and industrially applicable are important factors in the preference for nanofibers. Nanofibers, which have a broad scope of use in the field of health, are preferred both in drug delivery systems and tissue engineering. Due to the biocompatible materials used in their construction, they are also frequently preferred in ocular applications. The fact that they have a long drug release time as a drug delivery system and have been used in corneal tissue studies, which have been successfully developed in tissue engineering, stand out as important advantages of nanofibers. This review examines nanofibers, their production techniques and general information, nanofiber-based ocular drug delivery systems, and tissue engineering concepts in detail.

Electrospun-Fibrous-Architecture-Mediated Non-Viral Gene Therapy Drug Delivery in Regenerative Medicine

Gene-based therapy represents the latest advancement in medical biotechnology. The principle behind this innovative approach is to introduce genetic material into specific cells and tissues to stimulate or inhibit key signaling pathways. Although enormous progress has been achieved in the field of gene-based therapy, challenges connected to some physiological impediments (e.g., low stability or the inability to pass the cell membrane and to transport to the desired intracellular compartments) still obstruct the exploitation of its full potential in clinical practices. The integration of gene delivery technologies with electrospun fibrous architectures represents a potent strategy that may tackle the problems of stability and local gene delivery, being capable to promote a controlled and proficient release and expression of therapeutic genes in the targeted cells, improving the therapeutic outcomes. This review aims to outline the impact of electrospun-fibrous-architecture-mediated gene therapy drug delivery, and it emphatically discusses the latest advancements in their formulation and the therapeutic outcomes of these systems in different fields of regenerative medicine, along with the main challenges faced towards the translation of promising academic results into tangible products with clinical application.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Electrospun Nanofibers for Cancer Therapy

Lately, a remarkable progress has been recorded in the field of electrospinning for the preparation of numerous types of nanofiber scaffolds. These scaffolds present some remarkable features including high loading capacity and encapsulation efficiency, superficial area and porosity, potential for modification, structure for the co-delivery of various therapies, and cost-effectiveness. Their present and future applications for cancer diagnosis and treatment are promising and pioneering. In this chapter we provide a comprehensive overview of electrospun nanofibers (ESNFs) applications in cancer diagnosis and treatment, covering diverse types of drug-loaded electrospun nanofibers.

BMP and TGFβ use and release in bone regeneration

A fracture that does not unite in nine months is defined as nonunion. Nonunion is common in fragmented fractures and large bone defects where vascularization is impaired. The distal third of the tibia, the scaphoid bone or the talus fractures are furthermore prone to nonunion. Open fractures and spinal fusion cases also need special monitoring for healing. Bone tissue regeneration can be attained by autografts, allografts, xenografts and synthetic materials, however their limited availability and the increased surgical time as well as the donor site morbidity of autograft use, and lower probability of success, increased costs and disease transmission and immunological reaction probability of allografts oblige us to find better solutions and new grafts to overcome the cons. A proper biomaterial for regeneration should be osteoinductive, osteoconductive, biocompatible and mechanically suitable. Cytokine therapy, where growth factors are introduced either exogenously or triggered endogenously, is one of the commonly used method in bone tissue engineering. Transforming growth factor β (TGFβ) superfamily, which can be divided structurally into two groups as bone morphogenetic proteins (BMPs), growth differentiation factors (GDFs) and TGFβ, activin, Nodal branch, Mullerian hormone, are known to be produced by osteoblasts and other bone cells and present already in bone matrix abundantly, to take roles in bone homeostasis. BMP family, as the biggest subfamily of TGFβ superfamily, is also reported to be the most effective growth factors in bone and development, which makes them one of the most popular cytokines used in bone regeneration. Complications depending on the excess use of growth factors, and pleiotropic functions of BMPs are however the main reasons of why they should be approached with care. In this review, the Smad dependent signaling pathways of TGFβ and BMP families and their relations and the applications in preclinical and clinical studies will be briefly summarized.

Dexamethasone-loaded β-cyclodextrin for osteogenic induction of mesenchymal stem/progenitor cells and bone regeneration

Dexamethasone (DEX) is a glucocorticoid commonly used as an in vitro osteogenic inducer of mesenchymal stem/progenitor cells (abbreviated MSCs). However, several studies investigating the effects of glucocorticoids on bone regeneration through systemic injections have demonstrated negative impacts of the drugs at high concentration on the healing of hard tissues. These contrasting evidences suggest that application of glucocorticoids should be limited to low dosages but at the same time a long enough treatment period is preferred, which prompted us to evaluate the effects of different local release systems of DEX on MSC differentiation and bone repair. Two types of DEX-loaded β-cyclodextrin (CD) complexes, including CD/DEX and CD/AD-DEX, were fabricated via host-guest interactions and characterized by FTIR, 1H-NMR, MS-ESI, and UV-vis. The results demonstrated that these CD-based assemblies released DEX in differentiated profiles, with CD/DEX releasing significantly faster than CD/AD-DEX. Although CD/DEX were slightly more powerful than CD/AD-DEX in inducing rat bone marrow MSCs (rBMSCs) into osteogenic lineage in vitro, CD/AD-DEX was advantageous over CD/DEX in accelerating bone regeneration over a time period of 4 weeks in a rat tibia defect model. The results suggest that DEX-loaded assemblies via host-guest interactions are flexible in modulating DEX release patterns and have great potential in bone tissue engineering.

Meniscal tissue repair with nanofibers: future perspectives

The knee menisci are critical to the long-term health of the knee joint. Because of the high incidence of injury and degeneration, replacing damaged or lost meniscal tissue is extremely clinically relevant. The multiscale architecture of the meniscus results in unique biomechanical properties. Nanofibrous scaffolds are extremely attractive to replicate the biochemical composition and ultrastructural features in engineered meniscus tissue. We review recent advances in electrospinning to generate nanofibrous scaffolds and the current state-of-the-art of electrospun materials for meniscal regeneration. We discuss the importance of cellular function for meniscal tissue engineering and the application of cells derived from multiple sources. We compare experimental models necessary for proof of concept and to support translation. Finally, we discuss future directions and potential for technological innovations.

Osteogenic inducer sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surface

OBJECTIVE

Biomaterial can be locally applied to promote the osseointegration of dental implants. This study aimed to fabricate an osteogenic inducer (OI) sustained-release system and to evaluate its effects on the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces.

METHODS

First of all, different contents of OI solution were added to the poly (lactic-co-glycolic acid) (PLGA) gel individually to investigate the best physical properties and drug-release rate. Moreover, osteoblasts were isolated from the calvaria of two-month-old New Zealand rabbits through sequential enzymatic digestion. Osteoblasts were seeded onto the surface of Ti disks (control group), Ti coated with PLGA gel (PLGA group), and Ti coated with the OI sustained-release system (PLGA+OI group). Cell adhesion was observed by scanning electron microscopy. Cell proliferation was analyzed by cell counting kit-8. Cell differentiation was tested by alizarin red staining, alkaline phosphatase (ALP) activity and osteogenic-related gene expression.

RESULTS

The OI sustained-release system contained 15% OI solution had appropriate physical properties and drug-release rate. The osteoblasts in the PLGA+OI group were in a typical spindle shape with a considerable number indicating the promotion of adhesion and proliferation. The expression of early and late stage osteoblast differentiation genes in the PLGA+OI group were significantly higher than that of the control group and PLGA group at each time point. The PLGA group showed accelerated adhesion and differentiation but reduced proliferation compared with the control.

CONCLUSION

The OI sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces. This system is a cost-effective osteoconductive biomaterial that might be promising for use in dental implantation.

In situ bone tissue engineering using gene delivery nanocomplexes

Gene delivery offers promising outcomes for functional recovery or regeneration of lost tissues at cellular and tissue levels. However, more efficient carriers are needed to safely and locally delivery of genetic materials. Herein, we demonstrate microfluidic-assisted synthesis of plasmid DNA (pDNA)-based nanocomplexe (NC) platforms for bone tissue regeneration. pDNA encoding human bone morphogenesis protein-2 (BMP-2) was used as a gene of interest. Formation and fine-tuning of nanocomplexes (NCs) between pDNA and chitosan (CS) as carriers were performed using a micromixer platform. Flow characteristics were adjusted to tune mixing time and consequently size, zeta potential, and compactness of assembled NCs. Subsequently, NCs were immobilized on a nanofibrous Poly(ε-caprolactone) (PCL) scaffold functionalized with metalloprotease-sensitive peptide (MMP-sensitive). This construct can provide an environmental-sensitive and localized gene delivery platform. Osteogenic differentiation of bone marrow-derived mesenchymal stem cells (MSCs) was studied using chemical and biological assays. The presented results converge to indicate a great potential of the developed methodology for in situ bone tissue engineering using immobilized microfluidic-synthesized gene delivery nanocomplexes, which is readily expandable in the field of regenerative nanomedicine. STATEMENT OF SIGNIFICANCE: In this study, we demonstrate microfluidic-assisted synthesis of plasmid DNA (pDNA)-based nanocomplexes (NCs) platforms for bone tissue regeneration. We used pDNA encoding human bone morphogenesis protein-2 (BMP-2) as the gene of interest. Using micromixer platform nanocomplexes (NCs) between pDNA and chitosan (CS) were fabricated and optimized. NCs were immobilized on a nanofibrous polycaprolactone scaffold functionalized with metalloprotease-sensitive peptide. In vitro and in vivo assays confirmed the osteogenic differentiation of mesenchymal stem cells (MSCs). The obtained data indicated great potential of the developed methodology for in situ bone tissue engineering using immobilized microfluidic-synthesized gene delivery nanocomplexes, which is readily expandable in the field of regenerative nanomedicine.

Hybrid polymer/porous silicon nanofibers for loading and sustained release of synthetic DNA-based responsive devices

Synthetic DNA-based oligonucleotides are loaded into porous silicon nanoparticles (pSiNPs) and incorporated into nanofibers of poly(lactide-co-glycolide) (PLGA), poly-l-lactic acid (PLA), or polycaprolactone (PCL). The resulting hybrid nanofibers are characterized for their ability to release the functional oligonucleotide payload under physiologic conditions. Under temperature and pH conditions mimicking physiological values, the PLGA-based nanofibers release >80% of their DNA cargo within 5 days, whereas the PLA and PCL-based fibers require 15 days to release >80% of their cargo. The quantity of DNA released scales with the quantity of DNA-loaded pSiNPs embedded in the nanofibers; mass loadings of between 2.4 and 9.1% (based on mass of DNA-pSiNP construct relative to mass of polymer composite) are investigated. When a responsive DNA-based nanodevice (i.e. molecular beacon) is used as a payload, it retains its functionality during the release period, independent of the polymer used for the formation of the nanofibers.

Myoglobin- and Hydroxyapatite-Doped Carbon Nanofiber-Modified Electrodes for Electrochemistry and Electrocatalysis

In this paper, a hydroxyapatite (HAp)-doped carbon nanofiber (CNF)-modified carbon ionic liquid electrode (CILE) was prepared and used for the investigation on the direct electrochemistry and electrocatalysis of myoglobin (Mb). HAp nanoparticles were mixed within a polyacrylonitrile (PAN) solution, and a HAp@PAN nanofiber was synthesized by electrospinning process, which was further controlled by carbonization at 800 °C for 2 h in a nitrogen atmosphere to get a HAp@CNF nanocomposite. Various techniques were used to check the physicochemical properties of HAp@CNF. Mb was mixed with a HAp@CNF dispersion solution and casted on the surface of CILE to obtain an electrochemical sensing platform. The direct electrochemistry of Mb on the modified electrode was checked when a pair of enhanced redox waves appeared, indicating the direct electron transfer of Mb. HAp@CNF exhibited high conductivity, good biocompatibility, and large surface area, which was beneficial for Mb immobilization. The modified electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid and sodium nitrite, which was further used to establish a new electroanalytical method. Real samples were analyzed by the proposed method with satisfactory results.

A microparticle approach for non-viral gene delivery within 3D human mesenchymal stromal cell aggregates

Three-dimensional (3D) multicellular aggregates, in comparison to two-dimensional monolayer culture, can provide tissue culture models that better recapitulate the abundant cell-cell and cell-matrix interactions found in vivo. In addition, aggregates are potentially useful building blocks for tissue engineering. However, control over the interior aggregate microenvironment is challenging due to inherent barriers for diffusion of biological mediators (e.g. growth factors) throughout the multicellular aggregates. Previous studies have shown that incorporation of biomaterials into multicellular aggregates can support cell survival and control differentiation of stem cell aggregates by delivering morphogens from within the 3D construct. In this study, we developed a highly efficient microparticle-based gene delivery approach to uniformly transfect human mesenchymal stromal cells (hMSC) within multicellular aggregates and cell sheets. We hypothesized that release of plasmid DNA (pDNA) lipoplexes from mineral-coated microparticles (MCMs) within 3D hMSC constructs would improve transfection in comparison to standard free pDNA lipoplex delivery in the media. Our approach increased transfection efficiency 5-fold over delivery of free pDNA lipoplexes in the media and resulted in homogenous distribution of transfected cells throughout the 3D constructs. Additionally, we found that MCMs improved hMSC transfection by specifically increasing macropinocytosis-mediated uptake of pDNA. Finally, we showed up to a three-fold increase of bone morphogenetic protein-2 (BMP-2) expression and enhanced calcium deposition within 3D hMSC constructs following MCM-mediated delivery of a BMP-2 encoding plasmid and culture in osteogenic medium. The technology described here provides a valuable tool for achieving efficient and homogenous transfection of 3D cell constructs and is therefore of particular value in tissue engineering and regenerative medicine applications. STATEMENT OF SIGNIFICANCE: This original research describes a materials-based approach, whereby use of mineral-coated microparticles improves the efficiency of non-viral gene delivery in three-dimensional human mesenchymal stromal cell constructs. Specifically, it demonstrates the use of mineral-coated microparticles to enable highly efficient transfection of human mesenchymal stromal cells in large, 3D culture formats. The manuscript also identifies specific endocytosis pathways that interact with the mineral coating to afford the improved transfection efficiency, as well as demonstrates the utility of this approach toward improving differentiation of large cell constructs. We feel that this manuscript will impact the current understanding and near-term development of materials for non-viral gene delivery in broad tissue engineering and biofabrication applications, and therefore be of interest to a diverse biomaterials audience.

Electrospinning Nanofibers for Therapeutics Delivery

The limitations of conventional therapeutic drugs necessitate the importance of developing novel therapeutics to treat diverse diseases. Conventional drugs have poor blood circulation time and are not stable or compatible with the biological system. Nanomaterials, with their exceptional structural properties, have gained significance as promising materials for the development of novel therapeutics. Nanofibers with unique physiochemical and biological properties have gained significant attention in the field of health care and biomedical research. The choice of a wide variety of materials for nanofiber fabrication, along with the release of therapeutic payload in sustained and controlled release patterns, make nanofibers an ideal material for drug delivery research. Electrospinning is the conventional method for fabricating nanofibers with different morphologies and is often used for the mass production of nanofibers. This review highlights the recent advancements in the use of nanofibers for the delivery of therapeutic drugs, nucleic acids and growth factors. A detailed mechanism for fabricating different types of nanofiber produced from electrospinning, and factors influencing nanofiber generation, are discussed. The insights from this review can provide a thorough understanding of the precise selection of materials used for fabricating nanofibers for specific therapeutic applications and also the importance of nanofibers for drug delivery applications.

Correlating diameter, mechanical and structural properties of poly(l-lactide) fibres from needleless electrospinning

The development and application of nanofibres requires a thorough understanding of the mechanical properties on a single fibre level including respective modelling tools for precise fibre analysis. This work presents a mechanical and morphological study of poly-l-lactide nanofibres developed by needleless electrospinning. Atomic force microscopy (AFM) and micromechanical testing (MMT) were used to characterise the mechanical response of the fibres within a diameter range of 200-1400 nm. Young's moduli E determined by means of both methods are in sound agreement and show a strong increase for thinner fibres below a critical diameter of 800 nm. Similar increasing trends for yield stress and hardening modulus were measured by MMT. Finite element analyses show that the common practice of modelling three-point bending tests with either double supported or double clamped beams is prone to significant bias in the determined elastic properties, and that the latter is a good approximation only for small diameters. Therefore, an analytical formula based on intermediate boundary conditions is proposed that is valid for the whole tested range of fibre diameters, providing a consistently low error in axial Young's modulus below 10%. The analysis of fibre morphology by differential scanning calorimetry and 2D wide-angle X-ray scattering revealed increasing polymer chains alignment in the amorphous phase and higher crystallinity of fibres for decreasing diameter. The combination of these observations with the mechanical characterisation suggests a linear relationship between Young's modulus and both crystallinity and molecular orientation in the amorphous phase. STATEMENT OF SIGNIFICANCE: Fibrous membranes have rapidly growing use in various applications, each of which comes with specific property requirements. However, the development and production of nanofibre membranes with dedicated mechanical properties is challenging, in particular with techniques suitable for industrial scales such as needleless electrospinning. It is therefore a key step to understand the mechanical and structural characteristics of single nanofibres developed in this process, and to this end, the present work presents changes of internal fibre structure and mechanical properties with diameter, based on dedicated models. Special attention was given to the commonly used models for analyzing Young's modulus of single nanofibers in three-point bending tests, which are shown to be prone to large errors, and an improved robust approach is proposed.

Biomimetic Scaffolds for Bone Tissue Engineering

The use of biomimetic scaffolds for bone tissue engineering has been studied for a long time. Biomimetic scaffolds can assist and accelerate bone regeneration that is similar to that of authentic tissue, which represents the environment of cells in a living organism. Currently, numerous biomaterials have been reported for use as a biomimetic scaffold. This review focuses on the design of biomimetic scaffolds, kinds of biomaterials and methods used to fabricate biomimetic scaffolds, growth factors used with biomimetic scaffold for bone regeneration, mobilization of biological agents into biomimetic scaffolds, and studies on (pre)clinical bone regeneration from biomimetic scaffolds. Then, future prospects for biomimetic scaffolds are discussed.

Photoacoustic stimulation promotes the osteogenic differentiation of bone mesenchymal stem cells to enhance the repair of bone defect

The aim of this study was to evaluate the direct photoacoustic (PA) effect on bone marrow mesenchymal stem cells (BMSCs) which is a key cell source for osteogenesis. As scaffold is also an indispensable element for tissue regeneration, here we firstly fabricated a composited sheet using polylactic-co-glycolic acid (PLGA) mixing with graphene oxide (GO). BMSCs were seeded on the PLGA-GO sheets and received PA treatment in vitro for 3, 9 and 15 days, respectively. Then the BMSCs were harvested and subjected to assess alkaline phosphatase (ALP) activity, calcium content and osteopontin (OPN) on 3, 9 and 15 days. For in vivo study, PLGA-GO sheet seeded with BMSCs after in vitro PA stimulation for 9 days were implanted to repair the bone defect established in the femoral mid-shaft of Sprague-Dawley rat. PLGA-GO group with PA pretreatment showed promising outcomes in terms of the expression of ALP, OPN, and calcium content, thus enhanced the repair of bone defect. In conclusion, we have developed an alternative approach to enhance the repair of bone defect by making good use of the beneficial effect of PA.

Engineering Photocrosslinkable Bicomponent Hydrogel Constructs for Creating 3D Vascularized Bone

Engineering bone tissue requires the generation of a highly organized vasculature. Cellular behavior is affected by the respective niche. Directing cellular behavior and differentiation for creating mineralized regions surrounded by vasculature can be achieved by controlling the pattern of osteogenic and angiogenic niches. This manuscript reports on engineering vascularized bone tissues by incorporating osteogenic and angiogenic cell-laden niches in a photocrosslinkable hydrogel construct. Two-step photolithography process is used to control the stiffness of the hydrogel and distribution of cells in the patterned hydrogel. In addittion, osteoinductive nanoparticles are utilized to induce osteogenesis. The size of microfabricated constructs has a pronounced effect on cellular organization and function. It is shown that the simultaneous presence of both osteogenic and angiogenic niches in one construct results in formation of mineralized regions surrounded by organized vasculature. In addition, the presence of angiogenic niche improves bone formation. This approach can be used for engineered constructs that can be used for treatment of bone defects.

Reconstruction of Large-scale Defects with a Novel Hybrid Scaffold Made from Poly(L-lactic acid)/Nanohydroxyapatite/Alendronate-loaded Chitosan Microsphere: in vitro and in vivo Studies

A chitosan-based microsphere delivery system has been fabricated for controlled release of alendronate (AL). The present study aimed to incorporate the chitosan/hydroxyapatite microspheres-loaded with AL (CH/nHA-AL) into poly(L-lactic acid)/nanohydroxyapatite (PLLA/nHA) matrix to prepare a novel microspheres-scaffold hybrid system (CM-ALs) for drug delivery and bone tissue engineering application. The characteristics of CM-ALs scaffolds containing 10% and 20% CH/nHA-AL were evaluated in vitro, including surface morphology and porosity, mechanical properties, drug release, degradation, and osteogenic differentiation. The in vivo bone repair for large segmental radius defects (1.5 cm) in a rabbit model was evaluated by radiography and histology. In vitro study showed more sustained drug release of CM-AL-containing scaffolds than these of CM/nHA-AL and PLLA/nHA/AL scaffolds, and the mechanical and degradation properties of CM-ALs (10%) scaffolds were comparable to that of PLLA/nHA control. The osteogenic differentiation of adipose-derived stem cells (ASCs) was significantly enhanced as indicated by increased alkaline phosphates (ALP) activity and calcium deposition. In vivo study further showed better performance of CM-ALs (10%) scaffolds with complete repair of large-sized bone defects within 8 weeks. A microspheres-scaffold-based release system containing AL-encapsulated chitosan microspheres was successfully fabricated in this study. Our results suggested the promising application of CM-ALs (10%) scaffolds for drug delivery and bone tissue engineering.

Effects of HAp and TCP in constructing tissue engineering scaffolds for bone repair

TCP possesses superior long-term effects in structuring tissue engineering scaffold for bone repair compared to HAp, though TCP lags behind HAp in the early repair period.

Investigation of angiogenesis in bioactive 3-dimensional poly(d,l-lactide-co-glycolide)/nano-hydroxyapatite scaffolds by in vivo multiphoton microscopy in murine calvarial critical bone defect

Reconstruction of critical size bone defects remains a major clinical challenge because of poor bone regeneration, which is usually due to poor angiogenesis during repair. Satisfactory vascularization is a prerequisite for the survival of grafts and the integration of new tissue with existing tissue. In this work, we investigated angiogenesis in 3D scaffolds by in vivo multiphoton microscopy during bone formation in a murine calvarial critical bone defect model and evaluated bone regeneration 8weeks post-implantation. The continuous release of bioactive lentiviral vectors (LV-pdgfb) from the scaffolds could be detected for 5days in vitro. In vivo, the released LV-pdgfb transfected adjacent cells and expressed PDGF-BB, facilitating angiogenesis and enhancing bone regeneration. The expression of both pdgfb and the angiogenesis-related genes vWF and VEGFR2 was significantly increased in the pdgfb gene-carrying scaffold (PHp) group. In addition, microCT scanning and histomorphology results proved that there was more new bone ingrowth in the PHp group than in the PLGA/nHA (PH) and control groups. MicroCT parameters, including BMD, BV/TV, Tb.Sp, and Tb.N indicated that there was significantly more new bone formation in the PHp group than in the other groups. With regard to neovascularization, 8weeks post-implantation, blood vessel areas (BVAs) were 9428±944μm(2), 4090±680.3μm(2), and none in the PHp, PH, and control groups, respectively. At each time point, BVAs in the PHp scaffolds were significantly higher than in the PH scaffolds. To our knowledge, this is the first use of multiphoton microscopy in bone tissue-engineering to investigate angiogenesis in scaffolds in vivo. This method represents a valuable tool for investigating neovascularization in bone scaffolds to determine if a certain scaffold is beneficial to neovascularization. We also proved that delivery of the pdgfb gene alone can improve both angiogenesis and bone regeneration Acronyms.

STATEMENT OF SIGNIFICANCE

Reconstruction of critical size bone defects remains a major clinical challenge because of poor bone regeneration, which is usually due to poor angiogenesis during repair. Satisfactory vascularization is a prerequisite for the survival of grafts and the integration of new tissue with existing tissue. In this work, we investigated angiogenesis in 3D scaffolds by in vivo multiphoton microscopy during bone formation in a murine calvarial critical bone defect model and evaluated bone regeneration 8weeks post-implantation. To verify that pdgfb-expressing vectors carried by the scaffolds can promote angiogenesis in 3D-printed scaffolds in vivo, we monitored angiogenesis within the implants by multiphoton microscopy. To our knowledge, this is the first study to dynamically investigate angiogenesis in bone tissue engineering scaffolds in vivo.

PELA microspheres with encapsulated arginine-chitosan/pBMP-2 nanoparticles induce pBMP-2 controlled-release, transfected osteoblastic progenitor cells, and promoted osteogenic differentiation

Repair of the bone injury remains a challenge in clinical practices. Recent progress in tissue engineering and therapeutic gene delivery systems have led to promising new strategies for successful acceleration of bone repair process. The aim of this study was to create a controlled-release system to slowly release the arginine-chitosan/plasmid DNA nanoparticles encoding BMP-2 gene (Arg-CS/pBMP-2 NPs), efficiently transfect osteoblastic progenitor cells, secrete functional BMP-2 protein, and promote osteogenic differentiation. In this study, chitosan was conjugated with arginine to generate arginine-chitosan polymer (Arg-CS) for gene delivery. Mix the Arg-CS with pBMP-2 to condense pBMP-2 into nano-sized particles. In vitro transfection assays demonstrated that the transfection efficiency of Arg-CS/pBMP-2 nanoparticles and the expression level of BMP-2 was obviously exceed control groups. Further, PELA microspheres as the controlled-release carrier for the nanoparticles were used to encapsulate Arg-CS/pBMP-2 NPs. We demonstrated that the Arg-CS/pBMP-2 NPs could slowly release from the PELA microspheres at least for 42 d. During the co-culture with the PELA microspheres, the content of BMP-2 protein secreted by MC3T3-E1 reached the peak at 7 d. After 21d, the secretion of BMP-2 protein still maintain a higher level. The alkaline phosphatase activity, alizarin red staining, and osteogenesis-related gene expression by real-time quantitative PCR analysis all showed the PELA microspheres entrapping with Arg-CS/pBMP-2 NPs can obviously induce the osteogenic differentiation. The results indicated that the Arg-CS is a suitable gene vector which can promote the gene transfection. And the novel PELA microspheres-nanoparticle controlled-release system has potential clinical application in the future after further research.

Nanohydroxyapatite/cellulose nanocrystals/silk fibroin ternary scaffolds for rat calvarial defect regeneration

The purpose of this study was to design and characterise a novel biomimetic scaffold for the repair of critical size calvarial defects.

Highly porous ceramics based on ultralong hydroxyapatite nanowires

Highly porous ceramics with high biocompatibility are prepared using ultralong hydroxyapatite nanowires and palmitic acid spheres.

A renewable resource based carbon dot decorated hydroxyapatite nanohybrid and its fabrication with waterborne hyperbranched polyurethane for bone tissue engineering

Carbon dot decorated hydroxyapatite/water borne hyperbranched polyurethane nanocomposite.

Facile preparation of biphasic-induced magnetic icariin-loaded composite microcapsules by automated in situ click technology

This research aims to prepare the biphasic-induced magnetic composite microcapsules (BIMCM) as a promising environmental stimuli-responsive delivery vehicle to dispose the problem of drug burst effect. The paper presented a novel automated in situ click technology of magnetic chitosan/nano hydroxyapatite (CS/nHA) microcapsules. Fe3O4 magnetic nanoparticles (MNP) and nHA were simultaneously in situ crystallized by one-step process. Icariin (ICA), a plant-derived flavonol glycoside, was combined to study drug release properties of BIMCM. BIMCM were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Thermal gravimetric analysis/Differential Scanning Calorimetry(TGA/DSC) in order to reveal their component and surface morphology as well as the role of the in situ generated Fe3O4 MNP and nHA. The magnetic test showed the BIMCM were super-paramagnetic. Both in situ generated Fe3O4 MNP and nHA serve as stable inorganic crosslinkers in BIMCM to form many intermolecular crosslinkages for the movability of the CS chains. This makes ICA loaded microcapsules take on a sustained release behavior and results in the self-adjusting of surface morphology, decreasing of swelling and degradation rates. In addition, in vitro tests were systematically carried out to examine the biocompatibility of the microcapsules by MTT test, Wright-Giemsa dying assay and AO/EB fluorescent staining method. These results demonstrated that successful introduction of the in situ click Fe3O4 MNP provided an alternative strategy because of magnetic sensitivity and sustained release. As such, the novel ICA loaded biphasic-induced magnetic CS/nHA/MNP microcapsules are expected to find potential applications in drug delivery system for bone repair.

Nanostructured hydroxyapatite surfaces-mediated adsorption alters recognition of BMP receptor IA and bioactivity of bone morphogenetic protein-2

Highly efficient loading of bone morphogenetic protein-2 (BMP-2) onto carriers with desirable performance is still a major challenge in the field of bone regeneration. Till now, the nanoscaled surface-induced changes of the structure and bioactivity of BMP-2 remains poorly understood. Here, the effect of nanoscaled surface on the adsorption and bioactivity of BMP-2 was investigated with a series of hydroxyapatite surfaces (HAPs): HAP crystal-coated surface (HAP), HAP crystal-coated polished surface (HAP-Pol), and sintered HAP crystal-coated surface (HAP-Sin). The adsorption dynamics of recombinant human BMP-2 (rhBMP-2) and the accessibility of the binding epitopes of adsorbed rhBMP-2 for BMP receptors (BMPRs) were examined by a quartz crystal microbalance with dissipation. Moreover, the bioactivity of adsorbed rhBMP-2 and the BMP-induced Smad signaling were investigated with C2C12 model cells. A noticeably high mass-uptake of rhBMP-2 and enhanced recognition of BMPR-IA to adsorbed rhBMP-2 were found on the HAP-Pol surface. For the rhBMP-2-adsorbed HAPs, both ALP activity and Smad signaling increased in the order of HAP-Sin<HAP<HAP-Pol. Furthermore, hybrid molecular dynamics and steered molecular dynamics simulations validated that BMP-2 tightly anchored on the HAP-Pol surface with a relative loosened conformation, but the HAP-Sin surface induced a compact conformation of BMP-2. In conclusion, the nanostructured HAPs can modulate the way of adsorption of rhBMP-2, and thus the recognition of BMPR-IA and the bioactivity of rhBMP-2. These findings can provide insightful suggestions for the future design and fabrication of rhBMP-2-based scaffolds/implants.

STATEMENT OF SIGNIFICANCE

This study provides strong evidences that nanoscaled HAPs yield extraordinary influence on the adsorption behaviors and bioactivity of rhBMP-2. It has been found that the surface roughness and crystallinity played a crucial role in governing the way of rhBMP-2 binding to HAPs, and thus the conformation, recognition of BMPR-IA and bioactivity of adsorbed rhBMP-2. It is also for the first time to correlate numerical modeling and experimental results of the bioactivity of rhBMP-2 on nanostructured HAPs. This work can pave an avenue for the wider uses of rhBMP-2 in clinical applications and arouse broad interests among researchers in the fields of nano-biotechnology, biomaterials and bone tissue engineering.

Bone Regeneration from PLGA Micro-Nanoparticles

Poly-lactic-co-glycolic acid (PLGA) is one of the most widely used synthetic polymers for development of delivery systems for drugs and therapeutic biomolecules and as component of tissue engineering applications. Its properties and versatility allow it to be a reference polymer in manufacturing of nano- and microparticles to encapsulate and deliver a wide variety of hydrophobic and hydrophilic molecules. It additionally facilitates and extends its use to encapsulate biomolecules such as proteins or nucleic acids that can be released in a controlled way. This review focuses on the use of nano/microparticles of PLGA as a delivery system of one of the most commonly used growth factors in bone tissue engineering, the bone morphogenetic protein 2 (BMP2). Thus, all the needed requirements to reach a controlled delivery of BMP2 using PLGA particles as a main component have been examined. The problems and solutions for the adequate development of this system with a great potential in cell differentiation and proliferation processes under a bone regenerative point of view are discussed.

Emulating native periosteum cell population and subsequent paracrine factor production to promote tissue engineered periosteum-mediated allograft healing

Emulating autograft healing within the context of decellularized bone allografts has immediate clinical applications in the treatment of critical-sized bone defects. The periosteum, a thin, osteogenic tissue that surrounds bone, houses a heterogenous population of stem cells and osteoprogenitors. There is evidence that periosteum-cell derived paracrine factors, specifically vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP2), orchestrate autograft healing through host cell recruitment and subsequent tissue elaboration. In previous work, we demonstrated that the use of poly(ethylene glycol) (PEG) hydrogels as a tissue engineered (T.E.) periosteum to localize mesenchymal stem cells (MSCs) to the surface of decellularized bone enhances allograft healing and integration. Herein, we utilize a mixed population of 50:50 MSCs and osteoprogenitor cells to better mimic native periosteum cell population and paracrine factor production to further promote allograft healing. This mixed cell population was localized to the surface of decellularized allografts within degradable hydrogels and shown to expedite allograft healing. Specifically, bone callus formation and biomechanical graft-host integration are increased as compared to unmodified allografts. These results demonstrate the dual importance of periosteum-mediated paracrine factors orchestrating host cell recruitment as well as new bone formation while developing clinically translatable strategies for allograft healing and integration.

An insight on electrospun-nanofibers-inspired modern drug delivery system in the treatment of deadly cancers

This review gives an insight into the process of electrospinning, its essential parameters, the types of drug incorporation and the works reported on common dreadful cancers.

Effects of fiber alignment on stem cells–fibrous scaffold interactions

Fiber alignment-induced enhancement of cell adhesion and scaffold remodelling, and alignment of secreted ECM in differentiation.

Core–shell microspheres delivering FGF-2 and BMP-2 in different release patterns for bone regeneration

Sequential delivery of FGF-2 and BMP-2 efficiently bridged the bone defects and remodeled the bone graft.

Achieving accelerated osteogenic differentiation via novel magnesium silicate hollow spheres

Novel MgSiO₃ hollow spheres have been rationally designed and applied as promising candidates for osteogenic differentiation in vitro.

Gene delivery in tissue engineering and regenerative medicine

As a promising strategy to aid or replace tissue/organ transplantation, gene delivery has been used for regenerative medicine applications to create or restore normal function at the cell and tissue levels. Gene delivery has been successfully performed ex vivo and in vivo in these applications. Excellent proliferation capabilities and differentiation potentials render certain cells as excellent candidates for ex vivo gene delivery for regenerative medicine applications, which is why multipotent and pluripotent cells have been intensely studied in this vein. In this review, gene delivery is discussed in detail, along with its applications to tissue engineering and regenerative medicine. A definition of a stem cell is compared to a definition of a stem property, and both provide the foundation for an in-depth look at gene delivery investigations from a germ lineage angle.

Electrospun nanofibers as versatile interfaces for efficient gene delivery

The integration of gene delivery technologies with electrospun nanofibers is a versatile strategy to increase the potential of gene therapy as a key platform technology that can be readily utilized for numerous biomedical applications, including cancer therapy, stem cell therapy, and tissue engineering. As a spatial template for gene delivery, electrospun nanofibers possess highly advantageous characteristics, such as their ease of production, their ECM-analogue nature, the broad range of choices for materials, the feasibility of producing structures with varied physical and chemical properties, and their large surface-to-volume ratios. Thus, electrospun fiber-mediated gene delivery exhibits a great capacity to modulate the spatial and temporal release kinetics of gene vectors and enhance gene delivery efficiency. This review discusses the powerful characteristics of electrospun nanofibers, which can function as spatial interfaces capable of promoting controlled and efficient gene delivery.