Inclusion of calcium phosphate does not further improve in vitro and in vivo osteogenesis in a novel, highly biocompatible, mechanically stable and 3D printable polymer.

At a time of unpredictable challenges for health, one trend is certain: there is an exceedingly high demand for functional implants, particularly bone grafts. This has encouraged the emergence of bone tissue engineering substitutes as an alternative method to conventional bone grafts. However, the current approaches in the field face several limitations that have prevented the ultimate translation into clinical settings. As a result, many attempts have been made to fabricate synthetic bone implants that can offer suitable biological and mechanical properties.Light curable methacrylate-based polymers have ideal properties for bone repair. These materials are also suitable for 3D printing which can be applicable for restoration of both function and aesthetics. The main objective of this research was to investigate the role of calcium phosphate (CaP) incorporation in a mechanically stable, biologically functional and 3D printable polymer for the reconstruction of complex craniofacial defects. The experimental work initially involved the synthesis of (((((((((((3R,3aR,6S,6aR)- hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1- 48 diyl))bis(oxy))bis(carbonyl))bis(azanediyl))bis(3,3,5-trimethylcyclohexane-5,1- 49 diyl))bis(azanediyl))bis(carbonyl))bis(oxy))bis(ethane-2,1-diyl) bis(2-methylacrylate) referred to as CSMA and fabrication of composite discs via a Digital Light Printing (DLP) method. The flow behaviour of the polymer as a function of CaP addition, surface remineralisation potential, in vitro cell culture, using MC3T3 and Adipose-Derived Mesenchymal Stem Cells (ADSCs) and ex ovo angiogenic response was assessed. Finally, in vivo studies were carried out to investigate neo-bone formation at 4- and 8-weeks post-implantation. Quantitative micro-CT and histological evaluation did not show a higher rate of bone formation in CaP filled CSMA composites compared to CSMA itself. Therefore, such polymeric systems hold promising features by allowing more flexibility in designing a 3D printed scaffold targeted at the reconstruction of maxillofacial defects.

Trimethyl chitosan postoperative irrigation solution modulates inflammatory cytokines related to adhesion formation.

Lavage or irrigation has been instilled in surgical practice for wound clearance and surgical site infection prevention during and after surgery. Herein, we developed a new irrigation solution using trimethyl chitosan (TMC), a quaternized chitosan derivative. The TMC-saline irrigation solution developed in the study possesses highly effective bactericidal properties with hemostatic and anti-adhesion properties. The anti-adhesion property of TMC was investigated in relation to inflammatory cytokine response and wound healing. TMC-saline irrigation solution showed reduced pro-inflammatory cytokine protein and gene expressions relevant in the cascade of wound healing and cytokine-related orchestration of postoperative adhesion formation. Further development of this multifunctional TMC-saline irrigation solution can be beneficial for surgical applications and postoperative wound management.

Evaluation of bone regeneration potential of injectable extracellular matrix (ECM) from porcine dermis loaded with biphasic calcium phosphate (BCP) powder.

Extracellular matrix (ECM) contains a wide array of complex proteins, growth factors and cytokines that regulate cell behavior and tissue development. ECM harvested from non-homologous ECM sources still provide a structural support and biochemical cues to cells for effective tissue remodeling. The aim of this study is to evaluate the effect of non-tissue specific decellularized ECM from porcine dermis loaded with biphasic calcium phosphate powder (BCP) in bone regeneration. Thermosensitive ECM hydrogels with BCP powder exhibited a porous morphology with a suitable injectability and increased mechanical stability. In-vitro studies using MC3T3-E1 pre osteoblast cells showed that the injectable ECM hydrogels were biocompatible and supported the osteogenic differentiation. The bone regeneration capacity of the injectable ECM hydrogels was evaluated in-vivo by implanting in rat femoral head for 4 and 8 weeks. Micro-CT and histological staining results indicated that the injectable ECM hydrogels loaded with BCP powder showed higher and improved bone formation compared with the unfilled defect. Injectable ECM loaded with BCP powder is a good potential biomaterial for non-load bearing bone regeneration application.

Comparative study on biodegradation and biocompatibility of multichannel calcium phosphate based bone substitutes.

The objective of this study was to fabricate multichannel biphasic calcium phosphate (BCP) and ß-tricalcium phosphate (TCP) bone substitutes and compare their long-term biodegradation and bone regeneration potentials. Multi-channel BCP and TCP scaffolds were fabricated by multi-pass extrusion process. Both scaffolds were cylindrical with a diameter of 1-mm, a length of 1-mm, and seven interconnected channels. Morphology, chemical composition, phase, porosity, compressive strength, ion release behavior, and in-vitro biocompatibility of both scaffolds were studied. In-vivo biodegradation and bone regeneration efficacies of BCP and TCP were also evaluated using a rabbit model for 1 week, 1 month, and 6 months. BCP exhibited superior compressive strength compared to TCP scaffold. TCP showed higher release of both calcium ions and phosphorous ions than BCP in SBF solution. Both scaffolds showed excellent in-vitro biocompatibility and upregulated the expression of osteogenic markers of MC3T3-E1 cells. In-vivo studies revealed that both cylindrical TCP and BCP scaffolds were osteoconductive and supported new bone formation. Micro-CT data showed that the bone-regeneration efficacy of TCP was higher at one month and at six months after implantation. Histological examination confirmed that TCP degraded faster and had better bone regeneration than BCP after 6 months.

Enhanced decellularization technique of porcine dermal ECM for tissue engineering applications.

Effective removal of cellular components while retaining extracellular matrix (ECM) proteins is the ultimate goal of decellularization. The aim of this study is to produce a decellularized ECM with highly preserved ECM proteins and to determine the effect of isopropanol as a decellularization solvent on the characteristics of the decellularized porcine skin. Two different protocols were used for porcine skin decellularization. Protocol 1 consisted of Triton-X and sodium dodecyl sulfate (SDS) in water while protocol 2 consisted of Triton-X and SDS in 70% isopropanol. After decellularization, DNA components decreased significantly in protocol 2 with lower amount of lipid content and higher ECM proteins such as collagen (92.91 ±â€¯9.02 µg/mg sample), α-elastin (142.32 ±â€¯6.74 µg/mg sample) and sulfated glycosaminoglycan (sGAG; 7.44 ±â€¯1.30 µg/mg sample) compared with protocol 1 ECM. Higher amount of vascular endothelial growth factor (VEGF; 11.26 ±â€¯0.44 pg/mg sample) content was quantified in protocol 2 compared with protocol 1 while higher trace amount of bone morphogenic protein 2 (BMP-2; 0.28 ±â€¯0.04 pg/mg sample) was also observed in protocol 2 compared with protocol 1. Protocol 2 ECM did not significantly affect the cell viability and exhibited no cytotoxicity when exposed to three different cell lines: L929 fibroblast cells, MC3T3-E1 pre-osteoblast cells, and rat mesenchymal stem cells (BMSC). Subcutaneous implantation after 7 and 21 days revealed higher cell infiltration in protocol 2 ECM and enhanced neovascularization. Isopropanol/surfactants proved to be effective in cell and lipid removal during decellularization while preserving the higher amount of ECM proteins.

In vitro and in vivo evaluation of bioglass microspheres incorporated brushite cement for bone regeneration.

Bioglass-calcium phosphate cement (CPC) composite materials have recently received increased attention for bone regeneration purposes, owing to their improved properties in term of biocompatibility and bone ingrowths. In this study, an injectable bone substitute (IBS) system which utilizes bioglass microspheres incorporated into brushite based cement, was evaluated. The microspheres were synthesized with a simple and low sintering temperature process; there was no significant phase difference shown from the powder and good interactivity with cells was obtained. Furthermore, physical properties were optimized in microsphere incorporated brushite cement in order to investigate in vitro and in vivo performance. Accordingly, setting time and compressive strength were hardly altered until a microsphere content of 40% (v/v) was reached. The brushite (BR)/bioglass microsphere (BM) system showed excellent bioactivity to the in-vitro simulated body fluid test: dissolution ions from composite materials influenced apatite growth, countered acidic pH, and increased material degradation. In an in-vitro study with preosteoblasts (MC3T3-E1), BR/BM supported cell adhesion and proliferation, while cell differentiation experiments without osteogenic supplements, demonstrated that BR/BM induced osteogenic differentiation. A post-implantation study conducted in femoral defects showed higher materials degradation and bone formation in BR/BM than in BR. The faster dissolution of bioglass microspheres increased BR/BM composite resorption and hence facilitated bone tissue integration. Our findings suggest that bioglass microspheres incorporated in cement could potentially be used as an injectable bone substitute for bone regeneration applications.

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

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

Hemostasis and Bone Regeneration Using Chitosan/Gelatin-BCP Bi-layer Composite Material.

The aim of the study was to determine the hemostatic activity of a composite bi-layered topical hemostat composed of electrospun gelatin loaded with bi-phasic calcium phosphate and chitosan layer and its effect on bone formation. Morphology of the composite hemostat and its individual components were observed using scanning electron microscopy. In vitro biocompatibility of the topical hemostat tested using preosteoblasts cells (MC3t3-E1) showed no adverse toxicity. Confocal microscopy of seeded cells showed good cell adhesion while 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated 15% increased cell proliferation at the end of 1 week culture period. The material's efficiency as a hemostatic agent was tested by testing blood adsorption capacity and in vivo bone bleeding models. Blood absorption indicates that test sample measuring 14.14 mm becomes fully saturated within 5 minutes of blood contact. Bone bleeding was induced on the frontal plates of rat skulls and samples were applied as either removable topical hemostat or actual degradable hemostat. The effect of the bi-layered hemostat on bone formation was determined through analysis of micro-computed tomography (microCT) and observation of histological sections of extracted bone tissue samples. Results indicate that the bi-layer hemostat was able to halt bleeding within 3 minutes of application on the bleeding site and significantly enhanced bone regeneration. Using the bi-layer material as a degradable hemostat also drastically improved bone regeneration of the 3 mm defect.

Incorporation of chitosan-alginate complex into injectable calcium phosphate cement system as a bone graft material.

Calcium phosphate brushite type of cements have been used to replace bone graft materials because of their biocompatibility and other attractive features. Especially, injectability of cement allows easy handling of minimally invasive surgical techniques. New calcium phosphate cement (CPC) system, brushite based cement incorporated into polyelectrolyte complex, was developed in this study. Chitosan-alginate complex produced by an interaction between a cationic polymer (chitosan) and an anionic polymer (alginate) was loaded in the cement. This improved the functional properties and biocompatibility of the final cement. We optimized the liquid/solid (L/S) ratio of the cement components and investigated the compressive strength, setting time, pH change of CPC0 (with only citric acid) and CPC0.5, 1, and 1.5 (0.5, 1, and 1.5 v/v % chitosan-alginate complex in citric acid solution, respectively). The L/S ratio did not affect structural formation, while the addition of polymer complex showed new formation of macro-pores within CPC. However, a lower L/S ratio and higher amount of added polymer complex shortened the setting time and improved the compressive strength. The appropriate conditions for the injectable bone substitute were CPC1 with an L/S ratio of 0.45. To investigate the effect of the chitosan-alginate complex on CPC system in physiological conditions, CPC0 and CPC1 were implanted in a rabbit femoral head defect model for 1 and 3 months. Micro-computed tomography revealed improved bone formation in CPC1 compared to CPC0 3 months after implantation. Histological analysis revealed newly formed bone tissues around the peripheral sides of CPC0 and CPC1. The results indicate the potential value of the CPC system containing polymer complex as an injectable bone substitute. The study of the CPC-polymer complex system incorporating drugs or cells can be further developed into a controlled release system for faster bone regeneration.

In vitro and in vivo assessment of biomedical Mg-Ca alloys for bone implant applications.

BACKGROUND: Magnesium (Mg)-based alloys are considered to be promising materials for implant application due to their excellent biocompatibility, biodegradability, and mechanical properties close to bone. However, low corrosion resistance and fast degradation are limiting their application. Mg-Ca alloys have huge potential owing to a similar density to bone, good corrosion resistance, and as Mg is essential for Ca incorporation into bone. The objective of the present work is to determine the in vitro degradation and in vivo performance of binary Mg- xCa alloy ( x = 0.5 or 5.0 wt%) to assess its usability for degradable implant applications. METHODS: Microstructural evolutions for Mg- xCa alloys were characterized by optical, SEM, EDX, and XRD. In vitro degradation tests were conducted via immersion test in phosphate buffer saline solution. In vivo performance in terms of interface, biocompatibility, and biodegradability of Mg- xCa alloys was examined by implanting samples into rabbit femoral condyle for 2 and 4 weeks. RESULTS: Microstructural results showed the enhancement in intermetallic Mg2Ca phase with increase in Ca content. Immersion tests revealed that the dissolution rate varies linearly, with Ca content exhibiting more hydrogen gas evolution, increased pH, and higher degradation for Mg-5.0Ca alloy. In vivo studies showed good biocompatibility with enhanced bone formation for Mg-0.5Ca after 4 weeks of implantation compared with Mg-5.0Ca alloy. Higher initial corrosion rate with prolonged inflammation and rapid degradation was noticed in Mg-5.0Ca compared with Mg-0.5Ca alloy. CONCLUSIONS: The results suggest that Mg-0.5Ca alloy could be used as a temporary biodegradable implant material for clinical applications owing to its controlled in vivo degradation, reduced inflammation, and high bone-formation capability.

Development and properties of duplex MgF2/PCL coatings on biodegradable magnesium alloy for biomedical applications.

The present work addresses the performance of polycaprolactone (PCL) coating on fluoride treated (MgF2) biodegradable ZK60 magnesium alloy (Mg) for biomedical application. MgF2 conversion layer was first produced by immersing Mg alloy substrate in hydrofluoric acid solution. The outer PCL coating was then prepared using dip coating technique. Morphology, elements profile, phase structure, roughness, mechanical properties, invitro corrosion, and biocompatibility of duplex MgF2/PCL coating were then characterized and compared to those of fluoride coated and uncoated Mg samples. The invivo degradation behavior and biocompatibility of duplex MgF2/PCL coating with respect to ZK60 Mg alloy were also studied using rabbit model for 2 weeks. SEM and TEM analysis showed that the duplex coating was uniform and comprised of porous PCL film (~3.3 µm) as upper layer with compact MgF2 (~2.2 µm) as inner layer. No significant change in microhardness was found on duplex coating compared with uncoated ZK60 Mg alloy. The duplex coating showed improved invitro corrosion resistance than single layered MgF2 or uncoated alloy samples. The duplex coating also resulted in better cell viability, cell adhesion, and cell proliferation compared to fluoride coated or uncoated alloy. Preliminary invivo studies indicated that duplex MgF2/PCL coating reduced the degradation rate of ZK60 Mg alloy and exhibited good biocompatibility. These results suggested that duplex MgF2/PCL coating on magnesium alloy might have great potential for orthopedic applications.

Streamlined System for Conducting In Vitro Studies Using Decellularized Kidney Scaffolds.

Kidney regeneration is a complex process that can only be studied in vitro at a limited capacity due to the inherent structural and functional complexity of its tissues. Thus, a suitable platform for conducting cellular response and development should be established from decellularized tissues with intact microarchitecture. In this study, a modular streamlined system was developed to allow manageable handling and setup of in vitro studies using decellularized rat kidneys. The system is composed of commercially available parts that can be reused, interchanged, and reconfigured based on the desired experimental stage and process. Decellularization was confirmed through time-lapse observation, stained tissue sections, genetic material quantification, and protein analysis. The capacity of the bioreactor design to support cell-seeded decellularized kidney constructs was tested by determining viability of seeded podocytes and endothelial cells. Based on the results, decellularized kidneys with renal proteins and intact microstructures can be achieved in relatively shorter periods compared (12 h) to established protocols (96-120 h). The minimalistic kidney bioreactor design not only maintained sterility of decellularized kidney without cells but also permitted manageable maintenance of cell-immobilized constructs for up to 1 week. Through this streamlined system, sustainable and reproducible in vitro experiments for kidney regeneration can be designed and conducted using decellularized kidney as a platform for cell growth and development.

A hybrid composite system of biphasic calcium phosphate granules loaded with hyaluronic acid-gelatin hydrogel for bone regeneration.

An ideal bone substitute should be made of biocompatible materials that mimic the structure, characteristics, and functions of natural bone. Many researchers have worked on the fabrication of different bone scaffold systems including ceramic-polymer hybrid system. In the present study, we incorporated hyaluronic acid-gelatin hydrogel to micro-channeled biphasic calcium phosphate granules as a carrier to improve cell attachment and proliferation through highly interconnected porous structure. This hybrid system is composed of ceramic biphasic calcium phosphate granules measuring 1 mm in diameter with seven holes and hyaluronic acid-gelatin hydrogel. This combination of biphasic calcium phosphate and hyaluronic acid-gelatin retained suitable characteristics for bone regeneration. The resulting scaffold had a porosity of 56% with a suitable pore sizes. The mechanical strength of biphasic calcium phosphate granule increased after loading hyaluronic acid-gelatin from 4.26 ± 0.43 to 6.57 ± 0.25 MPa, which is highly recommended for cancellous bone substitution. Swelling and degradation rates decreased in the hybrid scaffold compared to hydrogel due to the presence of granules in hybrid scaffold. In vitro cytocompatibility studies were observed by preosteoblasts (MC3T3-E1) cell line and the result revealed that biphasic calcium phosphate/hyaluronic acid-gelatin significantly increased cell growth and proliferation compared to biphasic calcium phosphate granules. Analysis of micro-computed tomography data and stained tissue sections from the implanted samples showed that the hybrid scaffold had good osseointegration and better bone formation in the scaffold one and two months postimplantation. Histological section confirmed the formation of dense collagenous tissue and new bone in biphasic calcium phosphate/hyaluronic acid-gelatin scaffolds at two months. Our study demonstrated that such hybrid biphasic calcium phosphate/hyaluronic acid-gelatin scaffold is a promising system for bone regeneration.

Evaluation of egg white ovomucin-based porous scaffold as an implantable biomaterial for tissue engineering.

Studies have shown the technological and functional properties of ovomucin (OVN) in the food-agricultural industry. But research has yet to explore its potential as an implantable biomaterial for tissue engineering and regenerative medicine. In this study we isolated OVN from egg white by isoelectric precipitation and fabricated scaffolds with tunable porosity by utilizing its foaming property. Gelatin a known biocompatible material was introduced to stabilize the foams, wherein different ratios of OVN and gelatin had a significant effect on the degree of porosity, pore size and stability of the formed hydrogels. The porous scaffolds were crosslinked with EDC resulting in stable scaffolds with prolonged degradation. Improved cell proliferation and adhesion of rat bone marrow-derived mesenchymal stem cells were observed for OVN containing scaffolds. Although, scaffolds with 75% OVN showed decrease in cell proliferation for L929 fibroblast type of cells. Further biocompatibility assessment as implant material was determined by subcutaneous implantation in rats of selected scaffold. H&E staining showed reasonable vascularization over time and little evidence of severe fibrosis at the implant site. Persistent polarization of classically activated macrophage was not observed, potentially reducing inflammatory response, and showed increased expression of alternatively activated macrophage cells that is favorable for tissue repair. Analysis of IgE levels in rat serum after implantation indicated minimal and resolvable allergic response to the OVN implants. The results demonstrate OVN as an acceptable implant scaffold that could provide new opportunities as an alternative natural biocompatible and functional biomaterial in various biomedical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2107-2117, 2017.

A Study of BMP-2-Loaded Bipotential Electrolytic Complex around a Biphasic Calcium Phosphate-Derived (BCP) Scaffold for Repair of Large Segmental Bone Defect.

A bipotential polyelectrolyte complex with biphasic calcium phosphate (BCP) powder dispersion provides an excellent option for protein adsorption and cell attachment and can facilitate enhanced bone regeneration. Application of the bipotential polyelectrolyte complex embedded in a spongy scaffold for faster healing of large segmental bone defects (LSBD) can be a promising endeavor in tissue engineering application. In the present study, a hollow scaffold suitable for segmental long bone replacement was fabricated by the sponge replica method applying the microwave sintering process. The fabricated scaffold was coated with calcium alginate at the shell surface, and genipin-crosslinked chitosan with biphasic calcium phosphate (BCP) dispersion was loaded at the central hollow core. The chitosan core was subsequently loaded with BMP-2. The electrolytic complex was characterized using SEM, porosity measurement, FTIR spectroscopy and BMP-2 release for 30 days. In vitro studies such as MTT, live/dead, cell proliferation and cell differentiation were performed. The scaffold was implanted into a 12 mm critical size defect of a rabbit radius. The efficacy of this complex is evaluated through an in vivo study, one and two month post implantation. BV/TV ratio for BMP-2 loaded sample was (42±1.76) higher compared with hollow BCP scaffold (32±0.225).

Preformed chitosan cryogel-biphasic calcium phosphate: a potential injectable biocomposite for pathologic fracture.

The increasing interest in chitosan-based biomaterials stems from its desirable physicochemical properties. Although calcium phosphates have been mixed with chitosan to form injectable scaffolds, its application for bone tissue engineering has been limited and is still being explored to improve its clinical translatability. We report a biocomposite comprised of preformed chitosan cryogel with dispersed biphasic calcium phosphate that can flow under moderate pressure allowing passage through a small gauge needle, while maintaining sufficient integrity and strength during injection for gel recovery. The formed samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction analysis and protein adsorption measurements. Composite with 1% w/v biphasic calcium phosphate (CSG1) resulted in a homogeneous and rigid final structure. Injectable composite cryogel CSG1 (2.5 ± 0.2 N, 23G needle) exhibited good protein adsorption and biocompatibility. Results of subcutaneous implantation in rats reveal relatively high presence of polymorphonuclear cells but with no fibrous encapsulation with the composites, allowing further infiltration of cells within the sample implants. The biocomposite system presents a less-invasive delivery of bone filling material for stabilizing pathologic fractures.

Platelet-rich plasma encapsulation in hyaluronic acid/gelatin-BCP hydrogel for growth factor delivery in BCP sponge scaffold for bone regeneration.

Microporous calcium phosphate based synthetic bone substitutes are used for bone defect healing. Different growth factor loading has been investigated for enhanced bone regeneration. The platelet is a cellular component of blood which naturally contains a pool of necessary growth factors that mediate initiation, continuation, and completion of cellular mechanism of healing. In this work, we have investigated the encapsulation and immobilization of platelet-rich plasma (PRP) with natural polymers like hyaluronic acid (HA) and gelatin (Gel) and loading them in a biphasic calcium phosphate (BCP) scaffold, for a synthetic-allologous hybrid scaffold. Effect of PRP addition in small doses was evaluated for osteogenic potential in vitro and in vivo. BCP (10%) mixed HA-Gel hydrogel with or without PRP, was loaded into a BCP sponge scaffold. We investigated the hydrogel-induced improvement in mechanical property and PRP-mediated enhancement in biocompatibility. In vitro studies for cytotoxicity, cell attachment, and proliferation were carried out using MC3T3-E1 pre-osteoblast cells. In in vitro studies, the cell count, cell proliferation, and cell survival were higher in the scaffold with PRP loading than without PRP. However, in the in vivo studies using a rat model, the PRP scaffold was not superior to the scaffold without PRP. This discrepancy was investigated in terms of the interaction of PRP in the in vivo environment.