Combined delivery of BMP-2 and bFGF from nanostructured colloidal gelatin gels and its effect on bone regeneration in vivo

Electrophoretic Deposition of Bioadaptive Drug Delivery Coatings on Magnesium Alloy for Bone Repair

Biodegradable polymer coatings on magnesium alloys are attractive, as they can provide corrosion resistance as well as additional functions for biomedical applications, e.g., drug delivery. A gelatin nanospheres/chitosan (GNs/CTS) composite coating on WE43 substrate was fabricated by electrophoretic deposition with simvastatin (SIM) loaded into the GNs. Apart from a sustained drug release over 28 days, an anticorrosion behavior of the coated WE43 substrates was confirmed by electrochemical tests. Both the degradation and corrosion rates of the coated substrate were significantly minimized in contrast to bare WE43. The cytocompatibility of the coated samples was analyzed  both quantitatively and qualitatively. Additionally, the osteogenic differentiation of MC3T3-E1 cells on SIM-containing coatings was assessed by measuring the expression of osteogenic genes and related proteins, alkaline phosphatase (ALP) activity, and extracellular matrix mineralization, showing that the SIM-loaded composite coating could upregulate the expression of osteogenic genes and related proteins, promote ALP activity, and enhance extracellular matrix mineralization. In summary, the SIM-loaded GNs/CTS composite coatings were able to enhance the corrosion resistance of the WE43 substrate and promote osteogenic activity, thus demonstrating a promising coating system for modifying the surface of magnesium alloys targeted for orthopedic applications.

Monitoring local delivery of vancomycin from gelatin nanospheres in zebrafish larvae

Background

Infections such as biomaterial-associated infection and osteomyelitis are often associated with intracellular survival of bacteria (eg, Staphylococcus aureus). Treatment of these infections remains a major challenge due to the low intracellular efficacy of many antibiotics. Therefore, local delivery systems are urgently required to improve the therapeutic efficacy of antibiotics by enabling their intracellular delivery.

Purpose

To assess the potential of gelatin nanospheres as carriers for local delivery of vancomycin into macrophages of zebrafish larvae in vivo and into THP-1-derived macrophages in vitro using fluorescence microscopy.

Materials and methods

Fluorescently labeled gelatin nanospheres were prepared and injected into transgenic zebrafish larvae with fluorescent macrophages. Both the biodistribution of gelatin nanospheres in zebrafish larvae and the co-localization of vancomycin-loaded gelatin nanospheres with zebrafish macrophages in vivo and uptake by THP-1-derived macrophages in vitro were studied. In addition, the effect of treatment with vancomycin-loaded gelatin nanospheres on survival of S. aureus-infected zebrafish larvae was investigated.

Results

Internalization of vancomycin-loaded gelatin nanospheres by macrophages was observed qualitatively both in vivo and in vitro. Systemically delivered vancomycin, on the other hand, was hardly internalized by macrophages without the use of gelatin nanospheres. Treatment with a single dose of vancomycin-loaded gelatin nanospheres delayed the mortality of S. aureus-infected zebrafish larvae, indicating the improved therapeutic efficacy of vancomycin against (intracellular) S. aureus infection in vivo.

Conclusion

The present study demonstrates that gelatin nanospheres can be used to facilitate local and intracellular delivery of vancomycin.

Stiffness modification of photopolymerizable gelatin-methacrylate hydrogels influences endothelial differentiation of human mesenchymal stem cells

For stem cell differentiation, the microenvironment can play an important role, and hydrogels can provide a three-dimensional microenvironment to allow native cell growth in vitro. A challenge is that the stem cell's differentiation can be influenced by the matrix stiffness. We demonstrate a low-toxicity method to create different stiffness matrices, by using a photopolymerizable gelatin methacrylate (GelMA) hydrogel cross-linked by blue light (440 nm). The stiffness and porosity of GelMA hydrogel is easily modified by altering its concentration. We used human bone marrow mesenchymal stem cells (MSCs) as a cell source and cultured the GelMA-encapsulated cells with EGM-2 medium to induce endothelial differentiation. In our GelMA blue light hydrogel system, we found that MSCs can be differentiated into both endothelial-like and osteogenic-like cells. The mRNA expressions of endothelial cell markers CD31, von Willebrand factor, vascular endothelial growth factor receptor-2, and CD34 were significantly increased in softer GelMA hydrogels (7.5% and 10%) compared with stiffer matrices (15% GelMA). On the other hand, the enhancements of osteogenic markers mRNA expressions (Alkaline phosphatase (ALP), Runx2, osteocalcin, and osteopontin) were highest in 10% GelMA. We also found that 10% GelMA hydrogel offered optimal conditions for MSCs to form capillary-like structures. These results suggest that the mechanical properties of the GelMA hydrogel can influence both endothelial and osteogenic differentiation of MSCs and sequent capillary-like formation.

Injectable Gel Constructs with Regenerative and Anti-Infective Dual Effects Based on Assembled Chitosan Microspheres

There is increasing demand for biomaterials that both assist with bone regeneration and have anti-infection qualities in clinical applications. To achieve this goal, chitosan microspheres with either positive or negative charges were fabricated and then assembled as a gel for bone healing. The positively charged chitosan microspheres (CSM; ∼35.5 μm) and negatively charged O-carboxymethyl chitosan microspheres (CMCSM; ∼13.5 μm) were loaded, respectively, with bone morphogenetic protein (BMP-2) and berberine (Bbr) via swollen encapsulation and physical adsorption without a significant change in the electric charges. The release kinetics of BMP-2 and Bbr from the microspheres were also studied in vitro. The results showed that the Bbr/CMCSM microsphere group possessed high antibacterial activity against Staphylococcus aureus; the BMP-2/CSM microsphere group also had excellent cytocompatibility and improved osteoinductivity with the assistance of BMP-2. The assembled gel group consisting of Bbr/CMCSM and BMP-2/CSM had a porous structure that allowed biological signal transfer and tissue infiltration and exhibited significantly enhanced bone reconstruction compared with that of the respective microsphere groups, which should result from the osteoconductivity of the porous structure and the osteoinduction of the BMP-2 growth factor. The oppositely charged microspheres and their assembled gel provide a promising prospect for making injectable tissue-engineered constructs with regenerative and anti-infective dual effects for biomedical applications.

Porous Silk Fibroin Microspheres Sustainably Releasing Bioactive Basic Fibroblast Growth Factor

Basic fibroblast growth factor (bFGF) plays a significant role in stimulating cell proliferation. It remains a challenge in the field of biomaterials to develop a carrier with the capacity of continuously releasing bioactive bFGF. In this study, porous bFGF-loaded silk fibroin (SF) microspheres, with inside-out channels, were fabricated by high-voltage electrostatic differentiation, and followed by lyophilization. The embedded bFGF exhibited a slow release mode for over 13 days without suffering burst release. SEM observations showed that incubated L929 cells could fully spread and produce collagen-like fibrous matrix on the surface of SF microspheres. CLSM observations and the results of cell viability assay indicated that bFGF-loaded microspheres could significantly promote cell proliferation during five to nine days of culture, compared to bFGF-unloaded microspheres. This reveals that the bFGF released from SF microspheres retained obvious bioactivity to stimulate cell growth. Such microspheres sustainably releasing bioactive bFGF might be applied to massive cell culture and tissue engineering as a matrix directly, or after being combined with three-dimensional scaffolds.

Electrophoretic deposition of dexamethasone-loaded gelatin nanospheres/chitosan coating and its dual function in anti-inflammation and osteogenesis

Surface modification of metallic implants with bioactive and biodegradable coatings could be a promising approach for bone regeneration. The objective of this study was to prepare chitosan/gelatin nanospheres (GNs) composite coating for the delivery of dexamethasone (DEX). GNs with narrow size distribution and negative surface charge were firstly prepared by a two-step desolvation method. Homogeneous and stable gelatin nanospheres/chitosan (GNs/CTS) composite coatings were formed by electrophoretic deposition (EPD). Drug loading, encapsulation efficiency and in vitro release of DEX were estimated using high performance liquid chromatography (HPLC). The anti-inflammatory effect of DEX-loaded coatings on macrophage RAW 264.7 cells was assessed by the secretion of tumour necrosis factor (TNF) and inducible nitric oxide synthase (iNOS). Osteogenic differentiation of MC3T3-E1 osteoblasts on DEX-loaded coatings was investigated by osteogenic gene expression and mineralization. The DEX in GNs/CTS composite coating showed a two-stage release pattern could not only suppress inflammation during the burst release period, but also promote osteogenic differentiation in the sustained release period. This study might offer a feasible method for modifying the surface of metallic implants in bone regeneration.

Injectable network biomaterials via molecular or colloidal self-assembly

Self-assembly is a powerful tool to create functional materials. A specific application for which self-assembled materials are ideally suited is in creating injectable biomaterials. Contrasting with traditional biomaterials that are implanted through surgical means, injecting biomaterials through the skin offers numerous advantages, expanding the scope and impact for biomaterials in medicine. In particular, self-assembled biomaterials prepared from molecular or colloidal interactions have been frequently explored. The strategies to create these materials are varied, taking advantage of engineered oligopeptides, proteins, and nanoparticles as well as affinity-mediated crosslinking of synthetic precursors. Self-assembled materials typically facilitate injectability through two different mechanisms: i) in situ self-assembly, whereby materials would be administered in a monomeric or oligomeric form and self-assemble in response to some physiologic stimulus, or ii) self-assembled materials that, by virtue of their dynamic, non-covalent interactions, shear-thin to facilitate flow within a syringe and subsequently self-heal into its reassembled material form at the injection site. Indeed, many classes of materials are capable of being injected using a combination of these two mechanisms. Particular utility has been noted for self-assembled biomaterials in the context of tissue engineering, regenerative medicine, drug delivery, and immunoengineering. Given the controlled and multifunctional nature of many self-assembled materials demonstrated to date, we project a future where injectable self-assembled biomaterials afford improved practice in advancing healthcare.

Antioxidant N-Acetylcysteine and Glutathione Increase the Viability and Proliferation of MG63 Cells Encapsulated in the Gelatin Methacrylate/VA-086/Blue Light Hydrogel System

Photoencapsulation of cells inside a hydrogel system can provide a suitable path to establish a gel in situ for soft tissue regeneration applications. However, the presence of photoinitiators and blue or UV light irradiation can result in cell damage and an increase of reactive oxygen species. We here evaluate the benefits of an antioxidant pretreatment on the photoencapsulated cells. We study this by evaluating proliferation and viability of MG63 cells, which we combined with a gelatin methacrylate (GelMA) hydrogel system, using the photoinitiator, VA-086, cured with 440 nm blue light. We found that blue light irradiation as well as the presence of 1% VA-086 reduced MG63 cell proliferation rates. Adding a short pretreatment step to the MG63 cells, consisting of the antioxidant molecules N-acetylcysteine (NAC) and reduced glutathione (GSH), and optimizing the GelMA encapsulation steps, we found that both NAC and GSH pretreatments of MG63 cells significantly increased both proliferation and viability of the cells, when using a 15% GelMA hydrogel, 1% VA-086, and 1-min blue light exposure. These findings suggest that the use of antioxidant pretreatment can counteract the negative presence of the photoinitiators and blue light exposure and result in a suitable environment for photoencapsulating cells in situ for tissue engineering and soft tissue applications.

* Calvarial Bone Regeneration Is Enhanced by Sequential Delivery of FGF-2 and BMP-2 from Layer-by-Layer Coatings with a Biomimetic Calcium Phosphate Barrier Layer

A drug delivery coating for synthetic bone grafts has been developed to provide sequential delivery of multiple osteoinductive factors to better mimic aspects of the natural regenerative process. The coating is composed of a biomimetic calcium phosphate (bCaP) layer that is applied to a synthetic bone graft and then covered with a poly-l-Lysine/poly-l-Glutamic acid polyelectrolyte multilayer (PEM) film. Bone morphogenetic protein-2 (BMP-2) was applied before the coating process directly on the synthetic bone graft and then, bCaP-PEM was deposited followed by adsorption of fibroblast growth factor-2 (FGF-2) into the PEM layer. Cells access the FGF-2 immediately, while the bCaP-PEM temporally delays the cell access to BMP-2. In vitro studies with cells derived from mouse calvarial bones demonstrated that Sca-1 and CD-166 positive osteoblast progenitor cells proliferated in response to media dosing with FGF-2. Coated scaffolds with BMP-2 and FGF-2 were implanted in mouse calvarial bone defects and harvested at 1 and 3 weeks. After 1 week in vivo, proliferation of cells, including Sca-1+ progenitors, was observed with low dose FGF-2 and BMP-2 compared to BMP-2 alone, indicating that in vivo delivery of FGF-2 activated a similar population of cells as shown by in vitro testing. At 3 weeks, FGF-2 and BMP-2 delivery increased bone formation more than BMP-2 alone, particularly in the center of the defect, confirming that the proliferation of the Sca-1 positive osteoprogenitors by FGF-2 was associated with increased bone healing. Areas of bone mineralization were positive for double fluorochrome labeling of calcium and alkaline phosphatase staining of osteoblasts, along with increased TRAP+ osteoclasts, demonstrating active bone formation distinct from the bone-like collagen/hydroxyapatite scaffold. In conclusion, the addition of a bCaP layer to PEM delayed access to BMP-2 and allowed the FGF-2 stimulated progenitors to populate the scaffold before differentiating in response to BMP-2, leading to improved bone defect healing.

Smart Carriers and Nanohealers: A Nanomedical Insight on Natural Polymers

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer biodegradable systems are a promising arena of research for targeted and site-specific controlled drug delivery, for developing artificial limbs, 3D porous scaffolds for cellular regeneration or tissue engineering and biosensing applications. Several natural polymers have been identified, blended, functionalized and applied for designing nanoscaffolds and drug carriers as a prerequisite for enumerable bionano technological applications. Apart from these, natural polymers have been well studied and are widely used in material science and industrial fields. The present review explains the prominent features of commonly used natural polymers (polysaccharides and proteins) in various nanomedical applications and reveals the current status of the polymer research in bionanotechnology and science sectors.

Synergistic effects of fibroblast growth factor-2 and bone morphogenetic protein-2 on bone induction

The present study investigated the synergistic effect of co-administering fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2) on osteoblastic differentiation in C2C12 cells and in rats. C2C12 murine myoblast cells represent a well-accepted in vitro model system to study the ability of BMP-2 to alter cell lineage from the myogenic to the osteogenic phenotype. The osteoblastic differentiation potency was determined by alkaline phosphatase (ALP) and Alizarin red S staining. ALP activity and calcium concentrations were colorimetrically measured. Simultaneous administration of 4 µg/ml recombinant human BMP-2 with 2 ng/ml FGF-2 markedly enhanced ALP activity (an early marker of osteogenesis) of C2C12 cells. This combination also increased extracellular signal-regulated kinase1/2 mitogen activated protein kinase signaling that is involved in the promoting effect of FGF-2 on BMP-2-induced osteoblastic differentiation in C2C12 cells. Calcium deposition (a late marker of osteogenesis) and the expression of CD34 (a marker of new vessels) were promoted optimally by simultaneous local sustained administration of FGF-2 and BMP-2 using collagen and chitosan-coated antigen-extracted porcine cancellous implants in a rat ectopic implantation model. The synergistic effects of a combination of BMP-2 and FGF-2 may have potential for bone regenerative therapeutics.

Electrospun Nanofibrous Silk Fibroin Membranes Containing Gelatin Nanospheres for Controlled Delivery of Biomolecules

Development of novel and effective drug delivery systems for controlled release of bioactive molecules is of critical importance in the field of regenerative medicine. Here, oppositely charged gelatin nanospheres are incorporated into silk fibroin nanofibers through a colloidal electrospinning technique. A novel fibrous nano-in-nano drug delivery system is fabricated without the use of any organic solvent. The distribution of fluorescently labeled gelatin A and B nanospheres inside the nanofibers can be fine-tuned by simple adjustment of the weight ratio between the nanospheres and the relative feeding rate of core and shell solutions containing nanospheres by using single and coaxial nozzle electrospinning, respectively. Incorporation of vancomycin-loaded gelatin B nanospheres into the silk fibroin nanofibrous membranes results in a more sustained release of vancomycin, compared to the gelatin nanospheres free membranes. In addition, these membranes exhibit excellent and prolonged antibacterial effects against Staphylococcus aureus. Moreover, these membranes support the attachment, spreading, and proliferation of periodontal ligament cells. These results suggest that the beneficial properties of gelatin nanospheres can be exploited to improve the biological functionality of electrospun nanofibrous silk fibroin membranes.

Protein based therapeutic delivery agents: Contemporary developments and challenges

As unique biopolymers, proteins can be employed for therapeutic delivery. They bear important features such as bioavailability, biocompatibility, and biodegradability with low toxicity serving as a platform for delivery of various small molecule therapeutics, gene therapies, protein biologics and cells. Depending on size and characteristic of the therapeutic, a variety of natural and engineered proteins or peptides have been developed. This, coupled to recent advances in synthetic and chemical biology, has led to the creation of tailor-made protein materials for delivery. This review highlights strategies employing proteins to facilitate the delivery of therapeutic matter, addressing the challenges for small molecule, gene, protein and cell transport.

Multifunctional Nanocomposite Films for Synergistic Delivery of bFGF and BMP-2

The development of novel materials capable of delivering multiple growth factors is urgent and essential for rapid and effective tissue regeneration. In this study, a kind of composite film composed of poly-l-lysine (PLL), heparin (Hep), and Au nanoparitcles (Au nps) has been fabricated to deliver the basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) simultaneously. The films have been found to show enhanced mechanical property due to the incorporation of Au nps. They have also shown good anticoagulation activity with long activated partial thromboplastin time because of the contribution of Hep molecules. Moreover, the osteogenesis studies reveal that the loaded bFGF and BMP-2 in the composite films have a synergistic differentiation effect on mesenchymal stem cells, as indicated by alkaline phosphatase (ALP) activity assay and collagen type I (Col-I) gene expression. In contrast to the (PLL/Hep)6/BMP-2/(PLL/Au nps)6/(PLL/Hep)6 and (PLL/Hep)6/(PLL/Au nps)6/(PLL/Hep)6/bFGF films, the (PLL/Hep)6/BMP-2/(PLL/Au nps)6/(PLL/Hep)6/bFGF films have shown higher ALP activity and higher Col-I expression level. Therefore, the developed multifunctional films could be potentially used as osteoinductive coatings of biomaterials. Particularly, this simple and convenient strategy provides an effective approach for the immobilization of multiple growth factors, which may be extended to other bioactive systems for the development of novel multifunctional bioactive surfaces.

Hyaluronic-Acid-Hydroxyapatite Colloidal Gels Combined with Micronized Native ECM as Potential Bone Defect Fillers

One of the grand challenges in translational regenerative medicine is the surgical placement of biomaterials. For bone regeneration in particular, malleable and injectable colloidal gelsare frequently designed to exhibit self-assembling and shear-response behavior which facilitates biomaterial placement in tissue defects. The current study demonstrated that by combining native extracellular matrix (ECM) microparticles, i.e., demineralized bone matrix (DBM) and decellularized cartilage (DCC), with hyaluronic acid (HA) and hydroxyapatite (HAP) nanoparticles, a viscoelastic colloidal gel consisting exclusively of natural materials was achieved. Rheological testing of HA-ECM suspensions and HA-HAP-ECM colloidal gels concluded either equivalent or substantially higher storage moduli (G' ≈ 100-10 000 Pa), yield stresses (τ_y ≈ 100-1000 Pa), and viscoelastic recoveries (G'_recovery ≥ 87%) in comparison with controls formulated without ECM, which indicated a previously unexplored synergy in fluid properties between ECM microparticles and HA-HAP colloidal networks. Notable rheological differences were observed between respective DBM and DCC formulations, specifically in HA-HAP-DBM mixtures, which displayed a mean 3-fold increase in G' and a mean 4-fold increase in τ_y from corresponding DCC mixtures. An initial in vitro assessment of these potential tissue fillers as substrates for cell growth revealed that all formulations of HA-ECM and HA-HAP-ECM showed no signs of cytotoxicity and appeared to promote cell viability. Both DBM and DCC colloidal gels represent promising platforms for future studies in bone and cartilage tissue engineering. Overall, the current study identified colloidal gels constructed exclusively of natural materials, with viscoelastic properties that may facilitate surgical placement for a wide variety of therapeutic applications.

The effects of different amounts of drug microspheres on the vivo and vitro performance of the PLGA/β-TCP scaffold

OIC-A006 (BMPs osteogenesis compounds), can stimulate bone marrow mesenchymal stem cells ALP, OPN, OC, Cbfal expression. To stimulate new bone formation in the body. We postulate different amounts of drug microspheres on the PLGA/β-CPT scaffold can produce the effects on performance and sustained release characteristics. In this paper, through adding different amount of carrier drug microsphere, three concentrations scaffolds which are 12.5, 18.75 and 25 μmol/L are prepared by adding different amounts of drug-loaded microspheres. Hereafter called OICM/CPT-200, OICM/CPT-300, OICM/CPT-400. We implant them in rat femur diameter 3 mm depth of 3 mm hole for eight weeks. The degradation, microsphere, delivery properties, with X-ray, micro-CT and histology are tested. Results show that the contain carrier drug microsphere scaffolds become radiopaque, and the gaps between the scaffold and radial cut ends are often invisible. This preliminary study reveals that different carrier drug microsphere has a corresponding effect the performance of stent body, OICM/CPT – 200 scaffolds induction effect is best. Illustrates that the low concentration load OIC-A006 microspheres can promote bone healing, and high concentration of OIC-A006 micro ball is played a inhibitory effect on bone healing process.

Electrophoretic Deposition of Chitosan Coatings Modified with Gelatin Nanospheres To Tune the Release of Antibiotics

Orthopedic and dental implants are increasingly used in the medical field in view of their high success rates. Implant-associated infections, however, still occur and are difficult to treat. To combat these infections, the application of an active coating to the implant surface is advocated as an effective strategy to facilitate sustained release of antibacterial drugs from implant surfaces. Control over this release is, however, still a major challenge. To overcome this problem, we deposited composite coatings composed of a chitosan matrix containing gelatin nanospheres loaded with antibiotics onto stainless steel plates by means of the electrophoretic deposition technique. The gelatin nanospheres were distributed homogeneously throughout the coatings. The surface roughness and wettability of the coatings could be tuned by a simple adjustment of the weight ratio between the gelatin nanospheres and chitosan. Vancomycin and moxifloxacin were released in sustained and burst-type manners, respectively, while the coatings were highly cytocompatible. The antibacterial efficacy of the coatings containing different amounts of antibiotics was tested using a zone of inhibition test against Staphylococcus aureus, which showed that the coatings containing moxifloxacin exhibited an obvious inhibition zone. The coatings containing a high amount of vancomycin were able to kill bacteria in direct contact with the implant surface. These results suggest that the antibacterial capacity of metallic implants can be tuned by orthogonal control over the release of (multiple) antibiotics from electrophoretically deposited composite coatings, which offers a new strategy to prevent orthopedic implant-associated infections.

Patterning Biomaterials for the Spatiotemporal Delivery of Bioactive Molecules

The aim of tissue engineering is to promote the repair of functional tissues. For decades, the combined use of biomaterials, growth factors (GFs), and stem cells has been the base of several regeneration strategies. Among these, biomimicry emerged as a robust strategy to efficiently address this clinical challenge. Biomimetic materials, able to recapitulate the composition and architecture of the extracellular matrix, are the materials of choice, for their biocompatibility and higher rate of efficacy. In addition, it has become increasingly clear that restoring the complex biochemical environment of the target tissue is crucial for its regeneration. Toward this aim, the combination of scaffolds and GFs is required. The advent of nanotechnology significantly impacted the field of tissue engineering by providing new ways to reproduce the complex spatial and temporal biochemical patterns of tissues. This review will present the most recent approaches to finely control the spatiotemporal release of bioactive molecules for various tissue engineering applications.

Dual-functionalisation of gelatine nanoparticles with an anticancer platinum(ii)–bisphosphonate complex and mineral-binding alendronate

Mineral-binding gelatine nanoparticles can be loaded with tailored amounts of anticancer molecules, which may benefit the development of bone-seeking carriers for targeted delivery of drugs to treat bone tumours.

Photo-immobilization of bone morphogenic protein 2 on PLGA/HA nanocomposites to enhance the osteogenesis of adipose-derived stem cells

Poly(lactide-co-glycolide) and nano-hydroxyapatite composites are surface-modified with BMP-2 via photo-reactive gelatin to make the composites exhibit excellent bioactivities for the adhesion, proliferation and osteogenic differentiation of ADSCs.

Dual-controlled release system of drugs for bone regeneration

Controlled release systems have been noted to allow drugs to enhance their ability for bone regeneration. To this end, various biomaterials have been used as the release carriers of drugs, such as low-molecular-weight drugs, growth factors, and others. The drugs are released from the release carriers in a controlled fashion to maintain their actions for a long time period. Most research has been focused on the controlled release of single drugs to demonstrate the therapeutic feasibility. Controlled release of two combined drugs, so-called dual release systems, are promising and important for tissue regeneration. This is because the tissue regeneration process of bone formation is generally achieved by multiple bioactive molecules, which are produced from cells by other molecules. If two types of bioactive molecules, (i.e., drugs), are supplied in an appropriate fashion, the regeneration process of living bodies will be efficiently promoted. This review focuses on the bone regeneration induced by dual-controlled release of drugs. In this paper, various dual-controlled release systems of drugs aiming at bone regeneration are overviewed explaining the type of drugs and their release materials.

Continuous delivery of rhBMP2 and rhVEGF165 at a certain ratio enhances bone formation in mandibular defects over the delivery of rhBMP2 alone--An experimental study in rats

The aim of the present study was to test the hypothesis that different amounts of vascular endothelial growth factor and bone morphogenic protein differentially affect bone formation when applied for repair of non-healing defects in the rat mandible. Porous composite PDLLA/CaCO3 carriers were fabricated as slow release carriers and loaded with rhBMP2 and rhVEGF165 in 10 different dosage combinations using gas foaming with supercritical carbon dioxide. They were implanted in non-healing defects of the mandibles of 132 adult Wistar rats with additional lateral augmentation. Bone formation was assessed both radiographically (bone volume) and by histomorphometry (bone density). The use of carriers with a ratio of delivery of VEGF/BMP between 0.7 and 1.2 was significantly related to the occurrence of significant increases in radiographic bone volume and/or histologic bone density compared to the use of carriers with a ratio of delivery of ≤ 0.5 when all intervals and all outcome parameters were considered. Moreover, simultaneous delivery at this ratio helped to "save" rhBMP2 as both bone volume and bone density after 13 weeks were reached/surpassed using half the dosage required for rhBMP2 alone. It is concluded, that the combined delivery of rhVEGF165 and rhBMP2 for repair of critical size mandibular defects can significantly enhance volume and density of bone formation over delivery of rhBMP2 alone. It appears from the present results that continuous simultaneous delivery of rhVEGF165 and rhBMP2 at a ratio of approximately 1 is favourable for the enhancement of bone formation.

Controlled drug release for tissue engineering

Tissue engineering is often referred to as a three-pronged discipline, with each prong corresponding to 1) a 3D material matrix (scaffold), 2) drugs that act on molecular signaling, and 3) regenerative living cells. Herein we focus on reviewing advances in controlled release of drugs from tissue engineering platforms. This review addresses advances in hydrogels and porous scaffolds that are synthesized from natural materials and synthetic polymers for the purposes of controlled release in tissue engineering. We pay special attention to efforts to reduce the burst release effect and to provide sustained and long-term release. Finally, novel approaches to controlled release are described, including devices that allow for pulsatile and sequential delivery. In addition to recent advances, limitations of current approaches and areas of further research are discussed.

Nanoplex-Mediated Codelivery of Fibroblast Growth Factor and Bone Morphogenetic Protein Genes Promotes Osteogenesis in Human Adipocyte-Derived Mesenchymal Stem Cells

This study highlights the importance of transfection mediated coordinated bone morphogenetic protein 2 (BMP-2) and fibroblast growth factor 2 (FGF-2) signaling in promoting osteogenesis. We employed plasmids independently encoding BMP-2 and FGF-2 complexed with polyethylenimine (PEI) to transfect human adipose derived mesenchymal stem cells (hADMSCs) in vitro. The nanoplexes were characterized for size, surface charge, in vitro cytotoxicity, and transfection ability in hADMSCs. A significant enhancement in BMP-2 protein secretion was observed on day 7 post-transfection of hADMSCs with PEI nanoplexes loaded with both pFGF-2 and pBMP-2 (PEI/(pFGF-2+pBMP-2)) versus transfection with PEI nanoplexes of either pFGF-2 alone or pBMP-2 alone. Osteogenic differentiation of transfected hADMSCs was determined by measuring osteocalcin and Runx-2 gene expression using real time polymerase chain reactions. A significant increase in the expression of Runx-2 and osteocalcin was observed on day 3 and day 7 post-transfection, respectively, by cells transfected with PEI/(pFGF-2+pBMP-2) compared to cells transfected with nanoplexes containing pFGF-2 or pBMP-2 alone. Alizarin Red staining and atomic absorption spectroscopy revealed elevated levels of calcium deposition in hADMSC cultures on day 14 and day 30 post-transfection with PEI/(pFGF-2+pBMP-2) compared to other treatments. We have shown that codelivery of pFGF-2 and pBMP-2 results in a significant enhancement in osteogenic protein synthesis, osteogenic marker expression, and subsequent mineralization. This research points to a new clinically translatable strategy for achieving efficient bone regeneration.

Acceleration of callus formation during fracture healing using basic fibroblast growth factor-kidney disease domain-collagen-binding domain fusion protein combined with allogenic demineralized bone powder

Background

To repair fractures with large bone defects or gaps, demineralized allogenic bone matrix (DBM) is often applied to the fracture site. However, studies have shown that the use of DBM alone has limited efficacy for repairing fractures. In the present study, we developed an allogenic demineralized bone powder (DBP) with basic fibroblast-derived growth factor containing a polycystic kidney disease (PKD) domain and collagen-binding domain (CBD) from Clostridium histolyticum collagenase (ColH) and investigated the stimulatory effects of bFGF-PKD-CBD combined with allogenic DBP on bone growth in a mouse femur fracture model.

Methods

DBP mixed with either phosphate-buffered saline (PBS) (DBP/PBS), 0.58 nmol basic fibroblast growth factor (bFGF) (0.58 nmol DBP/bFGF), 0.058 nmol bFGF-PKD-CBD (0.058 nmol DBP/bFGF-PKD-CBD), or 0.58 nmol bFGF-PKD-CBD (0.58 nmol DBP/bFGF-PKD-CBD) was grafted into fracture sites.

Results

bFGF-PKD-CBD/DBP composite accelerates callus formation in a bone fracture model in mice and clearly showed that the composite also increases bone mineral density at fracture sites compared to bFGF/DBP. In addition, bFGF-PKD-CBD/DBP increased callus volume and bone mineral content to similar levels in fractures treated with a tenfold higher amount of bFGF at 4 weeks.

Conclusions

Our results suggest that bFGF-PKD-CBD/DBP may be useful for promoting fracture healing in the clinical setting.

Influence of the Molecular Weight and Charge of Antibiotics on Their Release Kinetics From Gelatin Nanospheres

In this study, we investigated the fundamental relationship between the physicochemical characteristics of antibiotics and the kinetics of their release from gelatin nanospheres. We observed that antibiotics of high molecular weight (colistin and vancomycin) were released in a sustained manner from oppositely charged gelatin carriers for more than 14 d, as opposed to antibiotics of low molecular weight (gentamicin and moxifloxacin) which were released in a burst-like manner. The release kinetics of positively charged colistin strongly correlated with the rate of the enzymatic degradation of gelatin. To elucidate the differences among release kinetics of antibiotics, we explored the mechanism of interactions between antibiotics and gelatin nanospheres by monitoring the kinetics of release of antibiotics as a function of pH, ionic strength, and detergent concentrations. These studies revealed that the interactions between antibiotics and gelatin nanospheres were mainly dominated by (i) strong electrostatic forces for colistin; (ii) strong hydrophobic and electrostatic forces for vancomycin; (iii) weak electrostatic and hydrophobic forces for gentamicin; and (iv) weak hydrophobic forces for moxifloxacin. These results confirm that release of antibiotics from gelatin nanospheres strongly depends on the physicochemical characteristics of the antibiotics.