Publicação
Dextrin injectable hydrogel for tissue healing and regeneration
| Resumo: | The worldwide incidence of bone disorders is increasing, mainly due to ageing population. The lack of effective treatments stimulates the development of novel synthetic bone substitutes (SBSs). Ceramic based-SBSs commercially available display poor handling properties. Attempting to overcome this shortcoming improving the acceptance of these formulations, granular ceramics have been associated with hydrogels. Hydrogels, particularly, in situ gelling hydrogels, allow the production of injectable formulations which may be administrated using minimally invasive procedures, able of perfect fitting to the irregularities of bone tissue defects. Moreover, hydrogels mimic the native extracellular matrix and can act as cell/drug delivery systems. Dextrin is a low-molecular-weight carbohydrate obtained from starch. It is a low cost, broadly available raw material widely used in many industrial applications, such as adhesives in the manufacture of gummed tapes, textiles and paper, as moisturiser in cosmetics. However, as yet it is quite unexplored in the biomedical field. An injectable and in situ gelation hydrogel based on dextrin (HG) was developed aiming to act as a multifuctional, biocompatible and injectable matrix able to carry and stabilize other materials and/or cells in medical procedures. To obtain the HG, dextrin was firstly oxidized with sodium periodate and then cross-linked with adipic acid dihydrazide (ADH). In order to demonstrate the biocompatibility and safety and of the newly produced hydrogel, a combination of in vitro and in vivo tests, many of them in compliance with international standard guidelines (ISO and OECD), were performed. Thus, this work aimed to assess the biocompatibility and safety of the HG for clinical utilization and its ability to act as a carrier and stabilizer for Bonelike® (BL) granules, a SBS produced by Bioskin, SA, in order to obtain a formulation with improved handling properties, such as mouldability and injectability, and bioactivity. Since the HG is intended for usage as a vehicle for medical application, a sterilization protocol for oxidized dextrin (ODEX) by gamma irradiation was investigated. The potential structural changes of the material were analysed using mass spectrometry-based techniques. The results showed that gamma irradiation did not promote changes on the chemical structure of ODEX and can be used as suitable terminal sterilization method for ODEX. In vitro cytotoxicity assays performed in human lymphoblastoid TK6 cells revealed that HG display concentration dependent cytotoxicity, which was assigned to ODEX. The genotoxic potential of the HG and its isolated components (ODEX and ADH) were assessed in eukaryotic and prokaryotic cells. The results revealed that HG, as well as ODEX and ADH, did not induce DNA or chromosomal damage. The in vivo biocompatibility and safety of the HG was further assessed by subacute systemic toxicity and skin sensitization tests, using rodent models. The results showed that the HG did not induce any systemic toxic effect, DNA damage in blood cells or skin reactions, neither impaired the natural bone repair/regeneration process. Then, the HG was successfully combined with BL granules (250-500 μm) to obtain a mouldable/injectable SBS and was implanted in two different bone defects: critical-sized calvarial defect (14 mm) and tibial fractures (4 mm) in goats. The results showed that HG allowed the stabilization of the granules into the defect, ensuring effective handling and moulding properties of the formulation and without affecting Bonelike® granules’ osteoconductive properties neither impairing the bone repair/regeneration process. Peptides obtained by hydrolysis of extracellular matrix from small intestinal submucosa (SIS), LLKKK18, a pro-angiogenic peptide, and human mesenchymal stem cells (hMSCs) from umbilical cord were also combined with the HG and BL granules to improve the bioactivity of the formulations. |
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| Autores principais: | Pereira, Isabel Sofia Melo |
| Assunto: | Engenharia e Tecnologia::Engenharia Médica |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The worldwide incidence of bone disorders is increasing, mainly due to ageing population. The lack of effective treatments stimulates the development of novel synthetic bone substitutes (SBSs). Ceramic based-SBSs commercially available display poor handling properties. Attempting to overcome this shortcoming improving the acceptance of these formulations, granular ceramics have been associated with hydrogels. Hydrogels, particularly, in situ gelling hydrogels, allow the production of injectable formulations which may be administrated using minimally invasive procedures, able of perfect fitting to the irregularities of bone tissue defects. Moreover, hydrogels mimic the native extracellular matrix and can act as cell/drug delivery systems. Dextrin is a low-molecular-weight carbohydrate obtained from starch. It is a low cost, broadly available raw material widely used in many industrial applications, such as adhesives in the manufacture of gummed tapes, textiles and paper, as moisturiser in cosmetics. However, as yet it is quite unexplored in the biomedical field. An injectable and in situ gelation hydrogel based on dextrin (HG) was developed aiming to act as a multifuctional, biocompatible and injectable matrix able to carry and stabilize other materials and/or cells in medical procedures. To obtain the HG, dextrin was firstly oxidized with sodium periodate and then cross-linked with adipic acid dihydrazide (ADH). In order to demonstrate the biocompatibility and safety and of the newly produced hydrogel, a combination of in vitro and in vivo tests, many of them in compliance with international standard guidelines (ISO and OECD), were performed. Thus, this work aimed to assess the biocompatibility and safety of the HG for clinical utilization and its ability to act as a carrier and stabilizer for Bonelike® (BL) granules, a SBS produced by Bioskin, SA, in order to obtain a formulation with improved handling properties, such as mouldability and injectability, and bioactivity. Since the HG is intended for usage as a vehicle for medical application, a sterilization protocol for oxidized dextrin (ODEX) by gamma irradiation was investigated. The potential structural changes of the material were analysed using mass spectrometry-based techniques. The results showed that gamma irradiation did not promote changes on the chemical structure of ODEX and can be used as suitable terminal sterilization method for ODEX. In vitro cytotoxicity assays performed in human lymphoblastoid TK6 cells revealed that HG display concentration dependent cytotoxicity, which was assigned to ODEX. The genotoxic potential of the HG and its isolated components (ODEX and ADH) were assessed in eukaryotic and prokaryotic cells. The results revealed that HG, as well as ODEX and ADH, did not induce DNA or chromosomal damage. The in vivo biocompatibility and safety of the HG was further assessed by subacute systemic toxicity and skin sensitization tests, using rodent models. The results showed that the HG did not induce any systemic toxic effect, DNA damage in blood cells or skin reactions, neither impaired the natural bone repair/regeneration process. Then, the HG was successfully combined with BL granules (250-500 μm) to obtain a mouldable/injectable SBS and was implanted in two different bone defects: critical-sized calvarial defect (14 mm) and tibial fractures (4 mm) in goats. The results showed that HG allowed the stabilization of the granules into the defect, ensuring effective handling and moulding properties of the formulation and without affecting Bonelike® granules’ osteoconductive properties neither impairing the bone repair/regeneration process. Peptides obtained by hydrolysis of extracellular matrix from small intestinal submucosa (SIS), LLKKK18, a pro-angiogenic peptide, and human mesenchymal stem cells (hMSCs) from umbilical cord were also combined with the HG and BL granules to improve the bioactivity of the formulations. |
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