Role of calcium phosphate and bioactive glass coating on in vivo bone healing of new Mg-Zn-Ca implant

Present investigation focuses on development and detailed characterization of a new Mg alloy sample (BM) with and without coating of hydroxyapatite (BMH) and bioactive glass (BMG) by air plasma spray method. After detailed mechano-physico-chemical characterization of powders and coated samples, electrochemical corrosion and SBF immersion tests were carried out. Detailed in vitro characterizations for cell viability were undertaken using MG-63 cell line followed by in vivo tests in rabbit model for studying bone healing up to 60 days. Starting current density increases from BM to BMH to BMG indicating highest resistance towards corrosion in case of BMG samples, however BMH also showed highest i(corr) value suggesting slowest rate of corrosion than BM and BMG samples. Dissolution of calcium ion in case of BMH and BMG control formation of apatite phases on surface. Ca2+ ions of coatings and from SBF solution underwent reduction reaction simultaneously with conversion of Mg to MgCl2 releasing OH- in the solution, which increases pH. Viability and propagation of human osteoblast-like cells was verified using confocal microscopy observations and from expression of bone specific genes. Alkaline phosphatase assay and ARS staining indicate cell proliferation and production of neo-osseous tissue matrix. In vivo, based on histology of heart, kidney and liver, and immune response of IL-2, IL-6 and TNF alpha, all the materials show no adverse effects in body system. The bone creation was observed to be more for BMH. Although both BMH and BMG show rays of possibilities in early new bone formation and tough bone-implant bonding at interface as compared to bare Mg alloy, however, BMG showed better well-sprayed coating covering on substrate and resistance against corrosion prior implanting in vivo. Also, better apatite formation on this sample makes it more favourable implant. GRAPHICS]

Evaluation of new porous beta-tri-calcium phosphate ceramic as bone substitute in goat model

The present study was carried out to evaluate the porous beta-tri-calcium phosphate (TCP) (prepared by aqueous solution combustion technique) as bone substitute and compared with normal healing in 12 adult Black. Bengal goats on the basis of clinical and radiographic findings, histological studies, oxytetracycline labeling, angiography studies (on day 90). Bone defects created in the diaphysis of radius were left unfilled in control animals (group I); while in treated (group II) animals the defects were filled with porous TCP blocks. The three months study showed no marked acute inflammatory reactions in all animals, wound healing was uneventful and the implants were clinically stable in the bone. Radiological studies showed presence of unabsorbed implants which acted as a scaffold for new bone growth across the defect whereas in control animals the defect was more or less same except that the newly formed bony tissue was less organized. Histological section showed moderately differentiated lamellar bone in the cortical part with presence of woven bone at peripheral cortex whereas control animals showed moderate fibro-collagenisation and good amount of marrow material, fat cells and blood vessels. Oxytetracycline labeling study showed crossing over of new bony trabeculae along with presence of resorption cavities within the new osteoid tissues whereas in group I, the process of new bone formation was active from both the ends; the defect site appeared as a homogenous non-fluorescent area. Angiogram of the animals in control showed uniform angiogenesis in the defect site with establishment of trans transplant angiogenesis, whereas in group II there was complete trans transplant shunting of blood vessels communication. The results of this study pointed out that the porous TCP promoted extensive bone formation over the entire extension of the defect in comparison to control group, thus conforming their biological osteoconductive property. (c) 2007 Elsevier B.V. All rights reserved

The repair of segmental bone defects with porous bioglass: An experimental study in goat

This study was exclusively conducted to evaluate healing of surgically created defects on the radius of adult Black Bengal goat after implantation of porous bioglass blocks and compare the process kinetics with normal healing. Twelve Black Bengal goats were divided randomly into two groups: control and experimental group implanted with bioglass blocks. Unicortical bone defects in radius were generated in all animals under aseptic condition. Local inflammatory reaction and healing of wound, radiological investigations, histological studies, oxytetracycline leveling and angiographic studies were performed up to 90th day post-operatively and compared with normal healing. It has been found that extensive new bone formation originating from host bone towards the implant whereas in control, the process was active from both the ends; the defect site appeared as homogenous nonfluorescent area. Thus, porous bioglass promoted bone formation over the entire extension of the defect independent of size of block in comparison to control group. (c) 2008 Elsevier Ltd. All rights reserved

Effect of doping in hydroxyapatite as coating material on biomedical implants by plasma spraying method: A review

Hydroxyapatite (HAp) is still one of the most widely used bioactive coating material to metallic implant in orthopedic fields because of its good biocompatibility, chemical and structural resemblance to natural bone, osteoconductivity, coupled with quicker implant fixation and strong bonding between living bone with implants. Many techniques are used to deposit HAp as coating material on metallic implants among which plasma spray coating stands out as this process is cost effective, reliable, and protects surface of metal from wear and corrosion. Although, HAp is a smart choice as implant coating material, however, its medical application has been restricted because of the unfavorable mechanical properties like brittleness, weak fracture toughness and poor tensile strength. Further, HAp coated implants suffer from longer time period for remodeling, slow osseointegration rate and lack of antimicrobial effects/properties. Different methodologies have been adopted as surface modification techniques to increase mechanical as well as biological properties of HAp. Among those approaches use of dopants in HAp is a very efficient way for modification of properties. Therefore, aim of this review paper is to assemble information related to HAp coating by plasma spray technique on implants and discuss their advantages and limitations. The article also reports how addition of various doping ions into HAp can overcome these limitations by effecting structural, compositional, mechanical properties of HAp. Finally, it reports how the single, binary and multi ion dopants incorporation in the HAp structure can affect the properties which ultimately affect implant functionality when coated by plasma spraying method

Converted marine coral hydroxyapatite implants with growth factors: In vivo bone regeneration

Herein we report rabbit model in vivo bone regeneration of hydrothermally converted coralline hydroxyapatite (HCCHAp) scaffolds without (group I) and with growth factors namely insulin like growth factor-1 (IGF-1) (group II) and bone morphogenetic protein-2 (BMP-2) (group III). All HCCHAp scaffolds have been characterized for phase purity and morphology before implantation. Calcined marine coral was hydrothermally converted using a mineralizer/catalyst to phase pure HAp retaining original pore structure and geometry. After sintering at 1250 degrees C, the HCCHAp found to have similar to 87% crystallinity, 70-75% porosity and 2 +/- 0.5 MPa compressive strength. In vitro growth factor release study at day 28 revealed 77 and 98% release for IGF-1 and BMP-2, respectively. The IGF-1 release was more sustained than BMP-2. In vivo bone healing of different groups was compared using chronological radiology, histological evaluations, scanning electron microscopy and fluorochrome labeling up to 90 days of implantation. In vivo studies showed substantial reduction in radiolucent zone and decreased radiodensity of implants in group II followed by group III and group I. These observations clearly suggest ingrowth of osseous tissue, initiation of bone healing and complete union between implants and natural bone in group II implants. A statistical score sheet based on histological observations showed an excellent osseous tissue formation in group II and group III scaffolds and moderate bone regeneration in group I scaffolds. (C) 2015 Elsevier B.V. All rights reserved

In vivo response of porous hydroxyapatite and beta-tricalcium phosphate prepared by aqueous solution combustion method and comparison with bioglass scaffolds

Pure hydroxyapatite (HAp) and a biphasic calcium phosphate [containing 90% of beta-tri-calcium phosphate (beta-TCP) and 10% HAp] were tailored through an aqueous solution combustion synthesis. Porous struts were prepared using all the powders along with bioglass, a known bioactive material, and subsequently characterized. Sterilized struts were implanted to the lateral side of radius bone of 24 black Bengal goats of either sex, in which a blank hole was left unfilled in a group of six specimens to act as control. The bone formation response of the three implanting materials in vivo has been studied using scanning electron microscope and histological analysis in contrast with positive controls. Push-out tests were used to assess the mechanical strength at the bone-biomaterial interface. It was observed that interfacial response was strongly dependent on combinations of different physical and chemical parameters. The surface of beta-TCP exhibited similar characteristics of bone and was distinct from those of intervening apatite layer of bioglass. Lower bone ingrowth and reduced strength was observed with HAp compared to beta-TCP/bioglass-based implants. Bone formation response of the Ca-P material varied according to the composition of the implanting material, which could be tailored through this novel synthesis. (C) 2007 Wiley Periodicals, Inc

Dual growth factor loaded nonmulberry silk fibroin/carbon nanofiber composite 3D scaffolds for in vitro and in vivo bone regeneration

In recent years the potential application of nanocomposite biomaterials in tissue engineering field is gaining importance because of the combined features of all the individual components. A bottom-up approach is acquired in this study to recreate the bone microenvironment. The regenerated silk protein fibroin obtained from nonmulberry tropical tasar Antheraea mylitta species is reinforced with functionalized Carbon Nano Fiber (CNF) and the composite sponges are fabricated using facile green aqueous based method. Biophysical investigations show that the matrices are porous and simultaneously bioactive when incubated in simulated body fluid. The reinforcement of CNF influences the mechanical property of the matrices by increasing the compressive modulus up to 46.54 MPa (∼4.3 times of the control fibroin sponge) in hydrated state, which is higher than the minimum required human trabecular bone modulus (10 MPa). The composite matrices are found to be non-hemolytic as well as cytocompatible. The growth factors (BMP-2 and TGF-β1) loaded composites show sustained release kinetics and an early attachment, growth, proliferation and osteogenic differentiation of the osteoblasts and mesenchymal stem cells. The matrices are immunocompatible as evidenced by minimal release of pro-inflammatory cytokines both in vitro and in vivo. In order to support the in vitro study, in vivo analysis of new bone formation within the implants is performed through radiological, μ-CT, fluorochrome labeling and histological analysis, which show statistically better bone formation on growth factor loaded composite scaffolds. The study clearly shows the potential attributes of these composite matrices as an extra cellular matrix for supporting successful osseointegration process

In vitro and in vivo evaluation of the marine sponge skeleton as a bone mimicking biomaterial

This investigation was carried out to identify and characterize marine sponges as potential bioscaffolds in bone tissue engineering. The marine sponge (Biemna fortis) samples were collected from the rocky intertidal region of Anjuna, Goa, India, freeze-dried and converted to pure cristobalite at low temperature. After thorough evaluation of sponge samples by DTA-TGA thermography, XRD, FTIR, SEM and cell cytotoxicity by MTT assay, bare sponge scaffolds were fabricated by firing at 1190 degrees C. These scaffolds were loaded with growth factors (IGF-1 and BMP-2), checked for quasi-dynamic in vitro release kinetics and finally implanted into femoral bone defects in rabbits for up to 90 days, by keeping an empty defect as a control. The in vivo bone healing process was evaluated and compared using chronological radiology, histology, SEM and fluorochrome labeling studies. SEM revealed that the sponge skeleton possesses a collagenous fibrous network consisting of highly internetworked porosity in the size range of 10-220 mu m. XRD and FTIR analysis showed a cristobalite phase with acicular crystals of high aspect ratio, and crystallinity was found to increase from 725 to 1190 degrees C. MTT assay demonstrated the non-cytotoxicity of the samples. A combination of burst and sustained release profile was noticed for both the growth factors and about 74.3% and 83% total release at day 28. In the radiological, histological, scanning electron microscopy and fluorochrome labeling analysis, the IGF-1 impregnated converted sponge scaffold promoted excellent osseous tissue formation followed by the BMP-2 loaded and bare one. These observations suggest that the marine sponge alone and in combination with growth factors is a promising biomaterial for bone repair and bone augmentation

Localized Immunomodulatory Silk Macrocapsules for Islet-like Spheroid Formation and Sustained Insulin Production

Pancreatic islet encapsulation in a 3D scaffolding matrix has achieved limited clinical success due to loss of islet function and cell death, shortly after transplantation. Also, transplant-associated inflammatory responses create an unfavorable microenvironment for islet survival. The current study delineates the development of cell-encapsulating immunomodulatory 3D silk scaffolds as bioartificial pancreas (BAP) systems for sustained insulin release. Insulin producing cells were encapsulated inside silk scaffolds with either alginate or agarose for immunoisolation to augment islet survival and function. The scaffolds were extensively characterized for pore architecture, porosity, swelling index, water uptake, and density. Further, suitability of these scaffolds was assessed through diverse <i>in vitro</i> tests, including cell adherence, viability, proliferation, 3D spheroid like pancreatic structures development, glucose stimulated insulin secretion, and macrophage polarization. Rat insulinoma (RIN-5) cells were metabolically active within the macroencapsulates and proliferated up to 2.5-fold over 5 weeks in culture. Cultured cells formed 3D islet-like spheroids spontaneously. Primary islets maintained their function in macroencapsulates with enhanced glucose stimulation index when compared to nonencapsulated islets, 1.2 vs 1.7. RT-qPCR and immunohistochemistry results supported the results obtained from glucose challenge assay. Controlled release profiles of anti-inflammatory cytokine interleukine-4 (IL-4) and dexamethasone evinced their prospective application in reducing local foreign body response and immunosuppression. Released IL-4 was biologically active and polarized M0 macrophages to the M2 phenotype, advocating immunosuppressive function. Reduced inflammatory responses illustrated the biocompatibility of these scaffolds. In conclusion, this novel biomaterial system was successfully used to encapsulate insulin-producing cells with enhanced cell functions. Further development of the system may have potential BAP applications

In Vitro and In Vivo Bone Regeneration Assessment of Titanium-Doped Waste Eggshell-Derived Hydroxyapatite in the Animal Model

Inthis work, a titanium-doped hydroxyapatite (HAp) scaffold wasproduced from two different sources (natural eggshell and laboratory-gradereagents) to compare the efficacy of natural and synthetic resourcesof HAp materials on new bone regeneration. This comparative studyalso reports the effect of Ti doping on the physical, mechanical,and in vitro as well as in vivo biological properties of the HAp scaffold.Pellets were prepared in the conventional powder metallurgy route,compacted, and sintered at 900 & DEG;C, showing sufficient porosityfor bony ingrowth. The physical-mechanical characterizations wereperformed by density, porosity evaluation, XRD, FTIR, SEM analysis,and hardness measurement. In vitro interactions were evaluated bybactericidal assay, hemolysis, MTT assay, and interaction with simulatedbody fluid. All categories of pellets showed absolute nonhemolyticand nontoxic character. Furthermore, significant apatite formationwas observed on the Ti-doped HAp samples in the simulated body fluidimmersion study. The developed porous pellets were implanted to assessthe bone defect healing in the femoral condyle of healthy rabbits.A 2 month study after implantation showed no marked inflammatory reactionfor any samples. Radiological analysis, histological analysis, SEManalysis, and oxytetracycline labeling studies depicted better invasionof mature osseous tissue in the pores of doped eggshell-derived HApscaffolds as compared to the undoped HAp, and laboratory-made samples.Quantification using oxytetracycline labeling depicted 59.31 & PLUSMN;1.89% new bone formation for Ti-doped eggshell HAp as compared toTi-doped pure HAp (54.41 & PLUSMN; 1.93) and other undoped samples. Histologicalstudies showed the presence of abundant osteoblastic and osteoclasticcells in Ti-doped eggshell HAp in contrast to other samples. Radiologicaland SEM data also showed similar results. The results indicated thatTi-doped biosourced HAp samples have good biocompatibility, new bone-formingability, and could be used as a bone grafting material in orthopedicsurgery