Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering

PEG grafted chitosan scaffold for dual growth factor delivery for enhanced wound healing

Application of growth factors at wound site has improved the efficiency and quality of healing. Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) induce proliferation of various cells in wound healing. Delivery of growth factor from controlled release systems protect it from degradation and also result in sustained delivery of it at the site of injury. The goal of the study was to develop a Polyethylene glycol (PEG) cross-linked cotton-like chitosan scaffold (CS-PEG-H) by freeze-drying method and chemically conjugate heparin to the scaffold to which the growth factors can be electrostatically bound and evaluate its wound healing properties in vitro and in vivo. The growth factor containing scaffolds induced increased proliferation of HaCaT cells, increased neovascularization and collagen formation seen by H and E and Masson’s trichrome staining. Immunohistochemistry was performed using the Ki67 marker which increased proliferation of cells in growth factor containing scaffold treated group. Frequent dressing changes are a major deterrent to proper wound healing. Our system was found to release both VEGF and bFGF in a continuous manner and attained stability after 7 days. Thus our system can maintain therapeutic levels of growth factor at the wound bed thereby avoiding the need for daily applications and frequent dressing changes. Thus, it can be a promising candidate for wound healing

PEG grafted chitosan scaffold for dual growth factor delivery for enhanced wound healing

AbstractApplication of growth factors at wound site has improved the efficiency and quality of healing. Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) induce proliferation of various cells in wound healing. Delivery of growth factor from controlled release systems protect it from degradation and also result in sustained delivery of it at the site of injury. The goal of the study was to develop a Polyethylene glycol (PEG) cross-linked cotton-like chitosan scaffold (CS-PEG-H) by freeze-drying method and chemically conjugate heparin to the scaffold to which the growth factors can be electrostatically bound and evaluate its wound healing properties in vitro and in vivo. The growth factor containing scaffolds induced increased proliferation of HaCaT cells, increased neovascularization and collagen formation seen by H and E and Masson’s trichrome staining. Immunohistochemistry was performed using the Ki67 marker which increased proliferation of cells in growth factor containing scaffold treated group. Frequent dressing changes are a major deterrent to proper wound healing. Our system was found to release both VEGF and bFGF in a continuous manner and attained stability after 7 days. Thus our system can maintain therapeutic levels of growth factor at the wound bed thereby avoiding the need for daily applications and frequent dressing changes. Thus, it can be a promising candidate for wound healing.</jats:p

Biocompatibility property of 100% strontium-substituted SiO2-Al2O3-P2O5-CaO-CaF2 glass ceramics over 26 weeks implantation in rabbit model: Histology and micro-Computed Tomography analysis

One of the desired properties for any new biomaterial composition is its long-term stability in a suitable animal model and such property cannot be appropriately assessed by performing short-term implantation studies. While hydroxyapatite (HA) or bioglass coated metallic biomaterials are being investigated for in vivo biocompatibility properties, such study is not extensively being pursued for bulk glass ceramics. In view of their inherent brittle nature, the implant stability as well as impact of long-term release of metallic ions on bone regeneration have been a major concern. In this perspective, the present article reports the results of the in vivo implantation experiments carried out using 100% strontium (Sr)-substituted glass ceramics with the nominal composition of 4.5 SiO2-3Al(2)O(3)-1.5P(2)O(5)-3SrO-2SrF(2) for 26 weeks in cylindrical bone defects in rabbit model. The combination of histological and micro-computed tomography analysis provided a qualitative and quantitative understanding of the bone regeneration around the glass ceramic implants in comparison to the highly bioactive HA bioglass implants (control). The sequential polychrome labeling of bone during in vivo osseointegration using three fluorochromes followed by fluorescence microscopy observation confirmed homogeneous bone formation around the test implants. The results of the present study unequivocally confirm the long-term implant stability as well as osteoconductive property of 100% Sr-substituted glass ceramics, which is comparable to that of a known bioactive implant, that is, HA-based bioglass. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1168-1179, 2015

Induction of oxidative stress and lymphocyte proliferation by nanohydroxyapatite in mice

The aim of this study is to evaluate the potential impact of intraperitoneally administered nanohydroxyapatite on the liver oxidative status and also to study the immunogenicity of the administered nanohydroxyapatite in Swiss albino mice. Biochemical estimation of the lipid peroxidation, reduced glutathione and the activities of the Glutathione peroxidase, Glutathione reductase and the Superoxide dismutase in the liver were carried out following 7, 14 and 21 days post-treatment with nanohydroxyapatite. Tritiated thymidine uptake studies were done with the splenic lymphocytes for studying the immunogenic potential. Histopathological evaluation of the liver, spleen and the kidney was also carried out. There was marked reduction in the reduced glutathione levels and in the activities of the antioxidant enzymes GPX, GR and SOD at 7 and 14 day and further showed an increase by the 21 day. The LPO levels showed a significant increase by the 21 day. The T lymphocytes proliferated by two-fold by the 7 day and returned to normal levels by the 14 day and an increase was seen by the 21 days. There was no histopathological lesion observed in the treated groups. The nanohydroxyapatite treatment lead to a marked reduction in the levels of the antioxidant enzyme activities which however increases by the 21 day indicating that the body is able to defend against the oxidative stress mounted by the nanohydroxyapatite. Nanohydroxyapatite has immunogenic potential as it was able to elicit proliferation of the T lymphocytes up to 21 days

Raman spectroscopy for the detection of organ distribution and clearance of PEGylated reduced graphene oxide and biological consequences

Graphene, a 2D carbon material has found vast application in biomedical field because of its exciting physico-chemical properties. The large planar sheet like structure helps graphene to act as an effective carrier of drug or biomolecules in enormous amount. However, limited data available on the biocompatibility of graphene upon interaction with the biological system prompts us to evaluate their toxicity in animal model. In this study organ distribution, clearance and toxicity of PEGylated reduced nanographene (PrGO) on Swiss Albino mice was investigated after intraperitoneal and intravenous administration. Biodistribution and blood clearance was monitored using confocal Raman mapping and indicated that PrGO was distributed on major organs such as brain, liver, kidney, spleen and bone marrow. Presence of PrGO in brain tissue suggests that it has the potential to cross blood brain barrier. Small amount of injected PrGO was found to excrete via urine. Repeated administration of PrGO induced acute liver injury, congestion in kidney and increased splenocytes proliferation in days following exposure. Hence the result of the study recommended that PrGO should undergo intensive safety assessment before clinical application or validated to be safe for medical use

In vitro and In vivo toxicity analysis of zinc selenium/zinc sulfide (ZnSe/ ZnS) quantum dots

Despite the versatility of quantum dots (QDs) in optoelectronics and biomedical field, their toxicity risks remain a considerable hindrance for clinical applications. Cytotoxicity of Cadmium containing QDs is well documented and reveals that they are toxic to cells. Reports suggest that the presence of toxic elements at the QD core (e.g., cadmium, selenium) is responsible for its toxicity in in vivo and in vitro levels. Hence, here the toxicity of heavy metal free ZnSe/ZnS QDs on two scenarios were assessed, (i) HEK cells as in vitro system and (ii) Swiss Albino mice as in vivo model. Before toxicity analysis, QDs subjected to various optical and physico-chemical characterization methods such as absorption and emission spectra analysis, observation under U.V light, TEM, DLS, Zeta potential, FTIR, Raman and XPS spectra, ICP-OES, TGA and DTG curve. It is very necessary to characterize the synthesized QDs because their toxicity greatly influenced by the physico-chemical properties. On checking the vulnerability of HEK cells on exposure to ZnSe/ZnS QDs, the obtained results disclose that ZnSe/ZnS QDs showed merest impact on cellular viability at a concentration less than 100 μg/ml. Acute toxicity of 10 mg/kg ZnSe/ZnS QDs was studied in mice and no clinical or behavioural changes were observed. It did not induce any changes in haematological parameters and any loss of body or organ weight. Moderate pathological changes were evident only in the liver, all others organs like kidney, spleen and brain did not show any manifestations of toxicity. Current work lays substantial bedrock for safe biomedical and environmental application of ZnSe/ZnS QDs in near future