Carrier For Growth Factors Research Articles

Heparin-modified graphene oxide loading anti-cancer drug and growth factor with heat stability, long-term release property and lower cytotoxicity

Heparin-modified graphene oxide was prepared as the carrier of anti-cancer drugs and growth factor with long-term release property, reduced cytotoxicity and improved heat stability.

Ceramic and non-ceramic hydroxyapatite as a bone graft material: a brief review.

Treatment of dental, craniofacial and orthopedic defects with bone graft substitutes has shown promising result achieving almost complete bone regeneration depending on product resorption similar to human bone's physicochemical and crystallographic characteristics. Among these, non-ceramic and ceramic hydroxyapatite being the main inorganic salt of bone is the most studied calcium phosphate material in clinical practices ever since 1970s and non-ceramic since 1985. Its "chemical similarity" with the mineralized phase of biologic bone makes it unique. Hydroxyapatite as an excellent carrier of osteoinductive growth factors and osteogenic cell populations is also useful as drug delivery vehicle regardless of its density. Porous ceramic and non-ceramic hydroxyapatite is osteoconductive, biocompatible and very inert. The need for bone graft material keeps on increasing with increased age of the population and the increased conditions of trauma. Recent advances in genetic engineering and doping techniques have made it possible to use non-ceramic hydroxyapatite in larger non-ceramic crystals and cluster forms as a successful bone graft substitute to treat various types of bone defects. In this paper we have mentioned some recently studied properties of hydroxyapatite and its various uses through a brief review of the literatures available to date.

Pharmacologically active microcarriers associated with thermosensitive hydrogel as a growth factor releasing biomimetic 3D scaffold for cardiac tissue-engineering

The challenge of tissue engineering of the infarcted heart is how to improve stem cell engraftment, survival, homing, and differentiation for myocardial repair. We here propose to integrate human adipose-derived stem cells (ADSCs) and pharmacologically active microcarriers (PAMs), a three-dimensional (3D) carrier of cells and growth factors, into an injectable hydrogel (HG), to obtain a system that stimulates the survival and/or differentiation of the grafted cells toward a cardiac phenotype. PAMs are biodegradable and non-cytotoxic poly(lactic-co-glycolic acid) (PLGA) microspheres conveying cells on their 3D surface that deliver continuously and in a controlled manner a growth factor (GF) acting on the transported cells and on the microenvironment to improve engraftment. The choice of the appropriate GF and its protection during the formulation process and delivery are essential. In this study two GFs, hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-1), have been encapsulated under a solid state in order to limit their interaction with the polymer and conserve their integrity. GF precipitation conditions and release profile from PAMs have been first investigated before combining them to ADSCs. The released IGF-1 and HGF induced the protein synthesis of cardiac differentiation markers GATA4, Nkx2.5, cTnI and CX43 after 1week in vitro. Moreover, the GFs accelerated cell cycle progression, as suggested by the increased expression of Cyclin D1 mRNA and the widespread distribution of Ki67 protein. Integrating PAMs within the thermosensitive P407 hydrogel increased their elastic properties but decreased the transcription of most cardiac markers. In contrast, CX43 expression increased in ADSC-PAM-GF complexes embedded within the hydrogel compared to the ADSCs cultured alone in the absence of P407. These results suggest that particulate scaffolds releasing HGF and IGF-1 may be beneficial for applications in tissue-engineering strategies for myocardial repair and the association with a P407 hydrogel can increase substrate elasticity and junction connections in ADSCs.

In vitro evaluation of photo‐crosslinkable chitosan‐lactide hydrogels for bone tissue engineering

Here we report the development and characterization of novel photo-crosslinkable chitosan-lactide (Ch-LA) hydrogels for bone tissue engineering. We synthesized the hydrogels based on Ch, LA, and methacrylic anhydride (MA), and examined their chemical structures, degradation rates, compressive moduli, and protein release kinetics. We also evaluated the cytotoxicity of the hydrogels and delivery efficacy of bone morphogenetic protein-2 (BMP-2) on osteoblast differentiation and mineralization using W-20-17 preosteoblast mouse bone marrow stromal cells and C2C12 mouse myoblast cells. NMR and FTIR revealed that the hydrogels were formed via amidation and esterification between Ch and LA, and methacrylation for photo-crosslinkable networks. Addition of a hydrophobic LA moiety to a hydrophilic Ch chain increased swellability, softness, and degradation rate of the photo-crosslinkable Ch-LA hydrogels. Changes in Ch/LA ratio and UV exposure time significantly affected compressive modulus and protein release kinetics. The photo-crosslinkable Ch-LA hydrogels were not cytotoxic regardless of the composition and UV crosslinking time. Higher alkaline phosphatase activities of both W-20-17 and C2C12 cells were observed in the less-crosslinked hydrogels at day 5. Mineralization was enhanced by sustained BMP-2 release from the hydrogels, but was cell type dependent. This photo-crosslinkable Ch-LA hydrogel is a promising carrier for growth factors.

Collagen—A biomaterial for delivery of growth factors and tissue regeneration

Research on collagen as a carrier for growth factors and cells is an actual field in modern tissue engineering. The progress in this field of research will make possible approaching the problem of regeneration of injured organs and large tissue fragments.

Alkali-Treated Collagen Hydrogels Incorporating Basic Fibroblast Growth Factor for Enhanced Angiogenesis

Collagen extracted from tissues by alkaline treatment has a di erent isoelectric point (pI≈5) than the commonly-used acidor pepsin-treated collagen (pI≈9). In this study, the feasibility of using the alkali-treated collagen (AC) as a carrier of basic broblast growth factor (bFGF) for enhancement of angiogenesis was examined. AC hydrogels were prepared by chemically crosslinking AC molecules using glutaraldehyde (GA). We investigated the e ects of GA concentration in AC gels on the degree of swelling of the gels in an aqueous environment and on the in vivo degradation rate of the gels. Horse cytochrome c (pI: 9.6), a model for bFGF (pI: 9.6), electrostatically adsorbed to the AC gels. Subcutaneously-implanted AC gels incorporating bFGF led to enhanced angiogenesis compared with bFGF-free gels. Thus, AC gels incorporating bFGF appear to be useful materials for (i) the enhancement of angiogenesis and (ii) tissue engineering sca olds.

Calcium Orthophosphate-Based Bioceramics.

Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In principle, bioceramics can be prepared from diverse materials but this review is limited to calcium orthophosphate-based formulations only, which possess the specific advantages due to the chemical similarity to mammalian bones and teeth. During the past 40 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the calcium orthophosphate-based implants remain biologically stable once incorporated into the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed and such formulations became an integrated part of the tissue engineering approach. Now calcium orthophosphate scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous and harbor different biomolecules and/or cells. Therefore, current biomedical applications of calcium orthophosphate bioceramics include bone augmentations, artificial bone grafts, maxillofacial reconstruction, spinal fusion, periodontal disease repairs and bone fillers after tumor surgery. Perspective future applications comprise drug delivery and tissue engineering purposes because calcium orthophosphates appear to be promising carriers of growth factors, bioactive peptides and various types of cells.

Hollow hydroxyapatite microspheres: A novel bioactive and osteoconductive carrier for controlled release of bone morphogenetic protein-2 in bone regeneration

The regeneration of large bone defects is a common and significant clinical problem. Limitations associated with existing treatments such as autologous bone grafts and allografts have increased the need for synthetic bone graft substitutes. The objective of this study was to evaluate the capacity of novel hollow hydroxyapatite (HA) microspheres to serve as a carrier for controlled release of bone morphogenetic-2 (BMP2) in bone regeneration. Hollow HA microspheres (106–150μm) with a high surface area (>100m2g−1) and a mesoporous shell wall (pore size 10–20nm) were created using a glass conversion technique. The release of BMP2 from the microspheres into a medium composed of diluted fetal bovine serum in vitro was slow, but it occurred continuously for over 2weeks. When implanted in rat calvarial defects for 3 or 6weeks, the microspheres loaded with BMP2 (1μg per defect) showed a significantly better capacity to regenerate bone than those without BMP2. The amount of new bone in the defects implanted with the BMP2-loaded microspheres was 40% and 43%, respectively, at 3 and 6weeks, compared to 13% and 17%, respectively, for the microspheres without BMP2. Coating the BMP2-loaded microspheres with a biodegradable polymer, poly(lactic-co-glycolic acid), reduced the amount of BMP2 released in vitro and, above a certain coating thickness, significantly reduced bone regeneration in vivo. The results indicate that these hollow HA microspheres could provide a bioactive and osteoconductive carrier for growth factors in bone regeneration.

Gelatin gel as a carrier of platelet-derived growth factors

Currently, patient's own growth factors from platelet-rich plasma and platelet-rich fibrin have been clinically used for repair and regeneration of defective tissues. In platelet-rich plasma and platelet-rich fibrin, fibrin gel is formed from blood fibrinogen and functions as a carrier for growth factors. In this study, the growth factors were extracted from the platelet-rich fibrin and incorporated into a gelatin gel by mixing the platelet-rich fibrin extract and gelatin solution before cross-linking with glutaraldehyde. About 70% of TGF-β1 was found to be released in vitro from the gelatin gel containing the platelet-rich fibrin extract into phosphate-buffered saline (-) in 7 days. The gelatin gel containing basic fibroblast growth factor, prepared as a comparison, showed a similar release profile. The gelatin gels were slowly degraded with time after subcutaneous implantation on the back of rats, and the gel containing the platelet-rich fibrin extract strongly induced neovascularization and granulation tissue formation around the implantation site compared to the gel only and the gel containing basic fibroblast growth factor, platelet-rich plasma, or platelet-rich fibrin. The gelatin gel containing the platelet-rich fibrin extract was attempted as wound dressing on a full-thickness skin defect model. After 2 weeks of application, the gel was found to be more effective in acceleration of wound healing than the commonly used platelet-rich plasma.

Tooth-derived bone graft material

With successful extraction of growth factors and bone morphogenic proteins (BMPs) from mammalian teeth, many researchers have supported development of a bone substitute using tooth-derived substances. Some studies have also expanded the potential use of teeth as a carrier for growth factors and stem cells. A broad overview of the published findings with regard to tooth-derived regenerative tissue engineering technique is outlined. Considering more than 100 published papers, our team has developed the protocols and techniques for processing of bone graft material using extracted teeth. Based on current studies and studies that will be needed in the future, we can anticipate development of scaffolds, homogenous and xenogenous tooth bone grafts, and dental restorative materials using extracted teeth.

The Need for Thorough in Vitro Testing of Biomaterial Scaffolds: Two Case Studies

Tissue engineered scaffolds are an integral part of future regenerative efforts, whether as carriers for stem cells and growth factors, or as acellular supports on their own. These scaffolds will be inserted at the site of injury, aim to provide temporary mechanical support and promote appropriate cell attachment and growth. Millions of dollars are spent on the development of biomaterial scaffolds, with many put into animal studies and clinical use without proper evaluation, often leading to unfavourable outcomes and associated patient morbidity.We exposed two novel scaffolds designed for use in tendon regeneration to a series of in vitro tests, the first a decellularised extracellular matrix (ECM), the second a silk-like material. SEM images were taken to evaluate scaffold nanostructure. Primary human dendritic cells were exposed to scaffolds, with FACS analysis of cell-surface activation markers determining scaffold immunogenicity. Growth of primary tenocytes was analysed using live-dead staining and alamarBlue® fluorescence, for cytocompatability. While, phenotypic retention was assessed through real-time PCR analysis of tenocytic genes.The decellularised ECM demonstrated low activation in the dendritic cell assay, suggesting low immunogenicity. The cytocompatability assays and real-time PCR analyses suggested that the material was indeed suitable for cell growth and differentiation. However, during the third biological repeat, no cells grew on the material, nor did they on the fourth and fifth repeat. In retrospect it appears that following the second repeat a new batch was tested, with very different properties to the first, which accounted for the reduced cytocompatability.The silk-like material produced some of the most repeatable and promising results with the cytocompatability and real-time PCR analyses, while the SEM demonstrated intertwined fibres suitable for cell alignment. However, the immunogenicity assay demonstrated that this material invoked high activation of the primary human dendritic cells, suggesting the material would be unsuitable for in vivo implantation.These studies have highlighted that without stringent testing in vitro, great time and expense would have been spent taking these materials forward for animal studies and potentially clinical studies, when clearly they are not suitable for these in their current incarnation.

A nanoparticulate injectable hydrogel as a tissue engineering scaffold for multiple growth factor delivery for bone regeneration

Gellan xanthan gels have been shown to be excellent carriers for growth factors and as matrices for several tissue engineering applications. Gellan xanthan gels along with chitosan nanoparticles of 297 ± 61 nm diameter, basic fibroblast growth factor (bFGF), and bone morphogenetic protein 7 (BMP7) were employed in a dual growth factor delivery system to promote the differentiation of human fetal osteoblasts. An injectable system with ionic and temperature gelation was optimized and characterized. The nanoparticle loaded gels showed significantly improved cell proliferation and differentiation due to the sustained release of growth factors. A differentiation marker study was conducted, analyzed, and compared to understand the effect of single vs dual growth factors and free vs encapsulated growth factors. Dual growth factor loaded gels showed a higher alkaline phosphatase and calcium deposition compared to single growth factor loaded gels. The results suggest that encapsulation and stabilization of growth factors within nanoparticles and gels are promising for bone regeneration. Gellan xanthan gels also showed antibacterial effects against Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis, the common pathogens in implant failure.

The redox state of recombinant human serum albumin and its optimal concentration for mouse embryo culture

Albumin has multiple physiological functions in embryo culture, such as a chelator of heavy metals, free radical scavenger, pH and osmotic regulator, a stabilizer, growth factor carrier, a surfactant, and a nutrient. However, the commercially available human serum albumin (HSA) products may not be completely safe since they could be contaminated with viruses and prions. Recombinant human serum albumin (rHSA) has been reported to be as efficient as commercial HSA for fertilization and embryo development. Despite the possible benefits of rHSA, it has not been widely used for embryo culture due to its high cost of production. Our objective was to analyze the redox state of different types of HSA products and rHSA to define oxidative status batch variations of HSA and rHSA and to evaluate the optimal concentration of rHSA for mouse embryo culture. The redox state of the HSA and rHSA used in embryo culture media was found to vary widely. Redox variations were found among different HSA batches as well as among rHSA batches. The highest blastocyst development and hatching rates were obtained with rHSA used at a concentration of 0.05 mg/mL. We showed that very low concentrations of rHSA were most favorable for advanced mouse embryo development in culture.

Mesoporous bioactive glass scaffolds for efficient delivery of vascular endothelial growth factor

In this article, we, for the first time, investigated mesoporous bioactive glass scaffolds for the delivery of vascular endothelial growth factor. We have found that mesoporous bioactive glass scaffolds have significantly higher loading efficiency and more sustained release of vascular endothelial growth factor than non-mesoporous bioactive glass scaffolds. In addition, vascular endothelial growth factor delivery from mesoporous bioactive glass scaffolds has improved the viability of endothelial cells. The study has suggested that mesopore structures in mesoporous bioactive glass scaffolds play an important role in improving the loading efficiency, decreasing the burst release, and maintaining the bioactivity of vascular endothelial growth factor, indicating that mesoporous bioactive glass scaffolds are an excellent carrier of vascular endothelial growth factor for potential bone tissue engineering applications.

Enhanced bone regeneration by gelatin-β-tricalcium phosphate composites enabling controlled release of bFGF

The objective of this study was to investigate the feasibility of biodegradable gelatin-β-tricalcium phosphate (β-TCP) composites as a cell scaffold and controlled-release carrier of basic fibroblast growth factor (bFGF) suitable for inducing bone regeneration at a segmental bone defect. The composite of gelatin sponge and β-TCP granules had an interconnected pore structure with an average size of 340 µm. The composite provided the controlled release of bFGF over 2 weeks. Segmental, critical-sized, bone defects of 20 mm length were created in the ulnas of New Zealand white rabbits and the gelatin-β-TCP composites, with or without incorporated bFGF, were implanted into the defects. Bone regeneration and β-TCP resorption profiles were evaluated by microcomputed tomography scanner analysis and haematoxylin and eosin staining. The composites incorporating bFGF promoted significantly higher bone regeneration at the defect site as compared to the bFGF-free composites. The controlled release of biologically active bFGF from the composites may possibly be achieved through the biodegradation of the composites, resulting in the promotion of bone regeneration. We conclude that the biodegradable gelatin-β-TCP composite is a promising scaffold for bone regeneration that enables the controlled release of bFGF.

The effect of Cu(II)‐loaded brushite scaffolds on growth and activity of osteoblastic cells

Bone substitute materials such as calcium phosphate cements (CPC) are frequently used as growth factor carriers for the stimulation of osteoblast-formation around an implant. However, biological modification based on delicate protein factors like extracellular matrix proteins or growth factors is subject to a number of shortcomings like the need for storage below room temperature and cost of production. The aim of this study was to investigate ionic modification as an alternative bioinorganic route for implant modification. Although it is known that Cu(II) plays a role in angiogenesis and bone formation, not all involved processes are well understood yet. In this study the in vitro effect of Cu(II) on growth and activity of osteoblastic cells seeded on brushite (CaHPO(4) · 2 H(2) O) scaffolds as well as on glass discs was investigated. The results show that Cu(II) enhances cell activity and proliferation of osteoblastic cells on CPC and furthermore affects the expression of several bone specific proteins such as bone sialo protein or osteocalcin. Therefore, the modification of CPC with Cu(II) may offer a promising alternative to protein based modification to stimulate cellular activity for an improved bone healing.

Nano‐fibrous microspheres with sustained growth factor delivery for bone regeneration

In this study, we developed a unique scaffolding system in which the biodegradable nano‐fibrous microspheres (NF‐MS) serve both as an injectable scaffold and as a growth factor carrier for bone regeneration. The NF‐MS were fabricated by a novel approach, which integrated an emulsification and a thermally induced phase separation technique. The NF‐MS mimicked the architecture of natural collagen fibers at a nanometer scale and had many unique properties including extraordinarily high surface area and extremely low density. Growth factors were effectively encapsulated (>90%) into the NF‐PLLA microspheres through a simple process without using any organic solvent. In vitro release kinetics indicated that the encapsulated recombinant human bone morphogenetic protein 7 (rhBMP‐7) in the NF‐MS were released in a temporal controlled manner. When used as an injectable scaffold for repairing the rat critical‐size calvarial defects, the rhBMP‐7‐loaded NF‐MS induced a much more significant amount of new bone formation than the rhBMP‐7‐free NF‐MS control. We conclude that the nano‐fibrous architecture combined with the sustained release of bioactive rhBMP‐7 from the NF‐MS are excellent cell carrier for bone regeneration. Support: NIH5P30DE20742Grant Funding Source: NIH 5P30DE20742

Novel Experimental and Clinical Therapeutic Uses of Low-Molecular-Weight Heparin/Protamine Microparticles

Low-molecular-weight heparin/protamine microparticles (LMW-H/P MPs) were produced as a carrier for heparin-binding growth factors (GFs) and for various adhesive cells. A mixture of low-molecular-weight heparin (MW: approximately 5000 Da, 6.4 mg/mL) and protamine (MW: approximately 3000 Da, 10 mg/mL) at a ratio of 7:3 (vol:vol) yields a dispersion of microparticles (0.5–3 µm in diameter). LMW-H/P MPs immobilize, control the release and protect the activity of GFs. LMW-H/P MPs can also bind to cell surfaces, causing these cells to interact with the LMW-H/P MPs, inducing cells/MPs-aggregate formation and substantially promoting cellular viability. Furthermore, LMW-H/P MPs can efficiently bind to tissue culture plates and retain the binding of important GFs, such as fibroblast growth factor (FGF)-2. The LMW-H/P MPs-coated matrix with various GFs or cytokines may provide novel biomaterials that can control cellular activity such as growth and differentiation. Thus, LMW-H/P MPs are an excellent carrier for GFs and various cells and are an efficient coating matrix for cell cultures.

The use of calcium phosphate-based biomaterials in implant dentistry

Since calcium phosphates (CaPs) were first proposed, a wide variety of formulations have been developed and continuously optimized, some of which (e.g. calcium phosphate cements, CPCs) have been successfully commercialized for clinical applications. These CaP-based biomaterials have been shown to be very attractive bone substitutes and efficient drug delivery vehicles across diverse biomedical applications. In this article, CaP biomaterials, principally CPCs, are addressed as alternatives/complements to autogenous bone for grafting in implant dentistry and as coating materials for enhancing the osteoinductivity of titanium implants, highlighting their performance benefits simultaneously as carriers for growth factors and as scaffolds for cell proliferation, differentiation and penetration. Different strategies for employing CaP biomaterials in dental implantology aim to ultimately reach the same goal, namely to enhance the osseointegration process for dental implants in the context of immediate loading and to augment the formation of surrounding bone to guarantee long-term success.

Enhanced Healing of Rat Calvarial Defects with Sulfated Chitosan-Coated Calcium-Deficient Hydroxyapatite/Bone Morphogenetic Protein 2 Scaffolds

Calcium phosphate cements (CPCs), which are widely used in bone regeneration, possess good biocompatibility and osteoconductivity and have been demonstrated to be candidate carriers for bone growth factors. However, limited release of growth factors from CPCs and slow degradation of the materials are not desirable for certain clinical applications. Previous studies have shown that calcium-deficient hydroxyapatite (CDHA) from CPCs presents more rapid degradation rate than CPCs. In this study, a hybrid growth factor delivery system was prepared by using bone morphogenetic protein 2 (BMP-2) loaded CDHA porous scaffold with sulfated chitosan (SCS) coating for improved release profile. We tested the BMP-2 release characteristic of CDHA/BMP-2/SCS composite in vitro and its ability to repair rat calvarial bone defects. A higher percentage of BMP-2 was released when sulfated chitosan coating was present compared with CDHA/BMP-2 group. Eight weeks postoperation, the repaired crania were evaluated by microcomputed tomography, sequential fluorescent labeling, histological analysis, and immunohistochemistry. CDHA/BMP-2/SCS group promoted the most extensive new bone formation than CDHA/BMP-2 and CDHA groups. Our observations suggest that sulfated chitosan coating could enhance the release profile of CDHA/BMP-2 composite in vitro and promote new bone formation in vivo. The hybrid CDHA/BMP-2/SCS system is a promising growth factor delivery strategy for bone regeneration.