Enriched mesoporous bioactive glass scaffolds as bone substitutes in critical diaphyseal bone defects in rabbits.

In the field of orthopedic surgery, there is an increasing need for the development of bone replacement materials for the treatment of bone defects. One of the main focuses of biomaterials engineering are advanced bioceramics like mesoporous bioactive glasses (MBG´s). The present study compared the new bone formation after 12 weeks of implantation of MBG scaffolds with composition 82,5SiO2-10CaO-5P2O5-x 2.5SrO alone (MBGA), enriched with osteostatin, an osteoinductive peptide, (MBGO) or enriched with bone marrow aspirate (MBGB) in a long bone critical defect in radius bone of adult New Zealand rabbits. New bone formation from the MBG scaffold groups was compared to the gold standard defect filled with iliac crest autograft and to the unfilled defect. Radiographic follow-up was performed at 2, 6, and 12 weeks, and microCT and histologic examination were performed at 12 weeks. X-Ray study showed the highest bone formation scores in the group with the defect filled with autograft, followed by the MBGB group, in addition, the microCT study showed that bone within defect scores (BV/TV) were higher in the MBGO group. This difference could be explained by the higher density of newly formed bone in the osteostatin enriched MBG scaffold group. Therefore, MBG scaffold alone and enriched with osteostatin or bone marrow aspirate increase bone formation compared to defect unfilled, being higher in the osteostatin group. The present results showed the potential to treat critical bone defects by combining MBGs with osteogenic peptides such as osteostatin, with good prospects for translation into clinical practice. STATEMENT OF SIGNIFICANCE: Treatment of bone defects without the capacity for self-repair is a global problem in the field of Orthopedic Surgery, as evidenced by the fact that in the U.S alone it affects approximately 100,000 patients per year. The gold standard of treatment in these cases is the autograft, but its use has limitations both in the amount of graft to be obtained and in the morbidity produced in the donor site. In the field of materials engineering, there is a growing interest in the development of a bone substitute equivalent. Mesoporous bioactive glass (MBG´s) scaffolds with three-dimensional architecture have shown great potential for use as a bone substitutes. The osteostatin-enriched Sr-MBG used in this long bone defect in rabbit radius bone in vivo study showed an increase in bone formation close to autograft, which makes us think that it may be an option to consider as bone substitute.

In vivo behavior in rabbit radius bone defect of scaffolds based on nanocarbonate hydroxyapatite.

Bone defects treatment may require the use of biomaterials that behave as a support and promote bone regeneration. Limitations associated with the use of autografts and allografts make it necessary to design new synthetic bone substitutes. Some of the most promising biomaterials currently under investigation are based on nanocarbonate hydroxyapatite (nCHA). In this study, we studied the bone-inducing capacity of nCHA-based scaffolds alone (SAG) and enriched with osteostatin (SAGO) or with bone marrow aspirate(SAGB) after implantation for 12 weeks in a 15-mm long critical defect performed in the radius of New Zealand rabbits. Bone formation obtained was compared with a group with the unfilled defect (CE), as control group, and other with the defect filed with iliac crest autograft (GS), as gold standard. X-ray follow-up was performed at 2, 4, 6 and 12 weeks and µCT and histological studies at 12 weeks. The radiological results showed a greater increment in bone formation in the GS group (75%-100%), followed by the SAG and SAGB groups (50%-75%). µCT results showed an increase of bone volume/tissue volume values in GS group followed by SAG and SAGB groups (0.53, 0.40, and 0.31 respectively) compared with CE group (0.26). Histological results showed limited resorption of the nCHA scaffolds and partial osseointegration in the SAG and SAGB groups. However, in the SAGO group, the presence of connective tissue encapsulating the scaffold was detected. In SAG, SAGB, and increase of bone formation were observed compared with CE group, but less than the GS group. Thus, the investigated materials represent a significant advance in the design of synthetic materials for bone grafting, but further studies are needed to bring their in vivo behavior closer to autograft, the gold standard.

Osteogenic Potential of a Biomaterial Enriched with Osteostatin and Mesenchymal Stem Cells in Osteoporotic Rabbits.

Mesoporous bioactive glasses (MBGs) of the SiO2-CaO-P2O5 system are biocompatible materials with a quick and effective in vitro and in vivo bioactive response. MBGs can be enhanced by including therapeutically active ions in their composition, by hosting osteogenic molecules within their mesopores, or by decorating their surfaces with mesenchymal stem cells (MSCs). In previous studies, our group showed that MBGs, ZnO-enriched and loaded with the osteogenic peptide osteostatin (OST), and MSCs exhibited osteogenic features under in vitro conditions. The aim of the present study was to evaluate bone repair capability after large bone defect treatment in distal femur osteoporotic rabbits using MBGs (76%SiO2-15%CaO-5%P2O5-4%ZnO (mol-%)) before and after loading with OST and MSCs from a donor rabbit. MSCs presence and/or OST in scaffolds significantly improved bone repair capacity at 6 and 12 weeks, as confirmed by variations observed in trabecular and cortical bone parameters obtained by micro-CT as well as histological analysis results. A greater effect was observed when OST and MSCs were combined. These findings may indicate the great potential for treating critical bone defects by combining MBGs with MSCs and osteogenic peptides such as OST, with good prospects for translation to clinical practice.

Enhancing Osteoblastic Cell Cultures with Gelatin Methacryloyl, Bovine Lactoferrin, and Bioactive Mesoporous Glass Scaffolds Loaded with Distinct Parsley Extracts.

The increasing interest in innovative solutions for addressing bone defects has driven research into the use of Bioactive Mesoporous Glasses (MBGs). These materials, distinguished by their well-ordered mesoporous structure, possess the capability to accommodate plant extracts with well-established osteogenic properties, including bovine lactoferrin (bLF), as part of their 3D scaffold composition. This harmonizes seamlessly with the ongoing advancements in the field of biomedicine. In this study, we fabricated 3D scaffolds utilizing MBGs loaded with extracts from parsley leaves (PL) and embryogenic cultures (EC), rich in bioactive compounds such as apigenin and kaempferol, which hold potential benefits for bone metabolism. Gelatin Methacryloyl (GelMa) served as the polymer, and bLF was included in the formulation. Cytocompatibility, Runx2 gene expression, ALP enzyme activity, and biomineralization were assessed in preosteoblastic MC3T3-E1 cell cultures. MBGs effectively integrated PL and EC extracts with loadings between 22.6 ± 0.1 and 43.6 ± 0.3 µM for PL and 26.3 ± 0.3 and 46.8 ± 0.4 µM for EC, ensuring cell viability through a release percentage between 28.3% and 59.9%. The incorporation of bLF in the 3D scaffold formulation showed significant differences compared to the control in all assays, even at concentrations below 0.2 µM. Combinations, especially PL + bLF at 0.19 µM, demonstrated additive potential, with superior biomineralization compared to EC. In summary, this study highlights the effectiveness of MBGs in incorporating PL and EC extracts, along with bLF, into 3D scaffolds. The results underscore cytocompatibility, osteogenic activity, and biomineralization, offering exciting potential for future in vivo applications.

Nanodevices based on mesoporous glass nanoparticles enhanced with zinc and curcumin to fight infection and regenerate bone.

Nanotechnology-based approaches are emerging as promising strategies to treat different bone pathologies such as infection, osteoporosis or cancer. To this end, several types of nanoparticles are being investigated, including those based on mesoporous bioactive glasses (MGN) which exhibit exceptional structural and textural properties and whose biological behaviour can be improved by including therapeutic ions in their composition and loading them with biologically active substances. In this study, the bone regeneration capacity and antibacterial properties of MGNs in the SiO2-CaO-P2O5 system were evaluated before and after being supplemented with 2.5% or 4% ZnO and loaded with curcumin. in vitro studies with preosteoblastic cells and mesenchymal stem cells allowed determining the biocompatible MGNs concentrations range. Moreover, the bactericidal effect of MGNs with zinc and curcumin against S. aureus was demonstrated, as a significant reduction of bacterial growth was detected in both planktonic and sessile states and the degradation of a pre-formed bacterial biofilm in the presence of the nanoparticles also occurred. Finally, MC3T3-E1 preosteoblastic cells and S. aureus were co-cultured to investigate competitive colonisation between bacteria and cells in the presence of the MGNs. Preferential colonisation and survival of osteoblasts and effective inhibition of both bacterial adhesion and biofilm formation of S. aureus in the co-culture system were detected. Our study demonstrated the synergistic antibacterial effect of zinc ions combined with curcumin and the enhancement of the bone regeneration characteristics of MGNs containing zinc and curcumin to obtain systems capable of simultaneously promoting bone regeneration and controlling infection. STATEMENT OF SIGNIFICANCE: In search of a new approach to regenerate bone and fight infections, a nanodevice based on mesoporous SiO2-CaO-P2O5 glass nanoparticles enriched with Zn2+ ions and loaded with curcumin was designed. This study demonstrates the synergistic effect of the simultaneous presence of zinc ions and curcumin in the nanoparticles that significantly reduces the bacterial growth in planktonic state and is capable to degrade pre-formed S. aureus biofilms whereas the nanosystem exhibits a cytocompatible behaviour in the presence of preosteoblasts and mesenchymal stem cells. Based on these results, the designed nanocarrier represents a promising alternative for the treatment of acute and chronic infections in bone tissues, while avoiding the significant current problem of bacterial resistance to antibiotics.

Antibacterial effect of 3D printed mesoporous bioactive glass scaffolds doped with metallic silver nanoparticles.

The development of new biomaterials for bone tissue regeneration with high bioactivity abilities and antibacterial properties is being intensively investigated. We have synthesized nanocomposites formed by mesoporous bioactive glasses (MBGs) in the ternary SiO2, CaO and P2O5 system doped with metallic silver nanoparticles (AgNPs) that were homogenously embedded in the MBG matrices. Ag/MBG nanocomposites have been directly synthesized and silver species were spontaneously reduced to metallic AgNPs by high temperatures (700 °C) obtained of last MBG synthesis step. Three-dimensional silver-containing mesoporous bioactive glass scaffolds were fabricated showing uniformly interconnected ultrapores, macropores and mesopores. The manufacture method consisted of a combination of a single-step sol-gel route in the mesostructure directing agent (P123) presence and a biomacromolecular polymer such as (hydroxypropyl)methyl cellulose (HPMC) as the macrostructure template, followed by rapid prototyping (RP) technique. Biological properties of Ag/MBG nanocomposites were evaluated by MC3T3-E1 preosteoblastic cells culture tests and bacterial (E. coli and S. aureus) assays. The results showed that the MC3T3-E1 cells morphology was not affected while preosteoblastic proliferation decreased when the presence of silver increased. Antimicrobial assays indicated that bacterial growth inhibition and biofilm destruction were directly proportional to the increased presence of AgNPs in the MBG matrices. Furthermore, in vitro co-culture of MC3T3-E1 cells and S. aureus bacteria confirmed that AgNPs presence was necessary for antibacterial activity, and AgNPs slightly affected cell proliferation parameters. Therefore, 3D printed scaffolds with hierarchical pore structure and high antimicrobial capacity have potential applications in bone tissue regeneration. STATEMENT OF SIGNIFICANCE: This study combines three key scientific aspects for bone tissue engineering: (i) materials with high bioactivity to repair and regenerate bone tissue that (ii) contain antibacterial agents to reduce the infection risk (iii) in the form of three-dimensional scaffolds with hierarchical porosity. Innovative methodology is described here: sol-gel method, which is employed to obtain mesoporous bioactive glass matrices doped with metallic silver nanoparticles where different polymer templates facilitate the different size scales presence, and rapid prototyping technique that provides ultra-large macroporosity according to computer-aided design. The dual scaffolds obtained are biocompatible and deliver active doses of silver capable of combating bone infections, which represent one of the most serious complications associated to surgical treatments of bone diseases and fractures.

Cu-Doped Hollow Bioactive Glass Nanoparticles for Bone Infection Treatment.

In search of new approaches to treat bone infection and prevent drug resistance development, a nanosystem based on hollow bioactive glass nanoparticles (HBGN) of composition 79.5SiO2-(18-x)CaO-2.5P2O5-xCuO (x = 0, 2.5 or 5 mol-% CuO) was developed. The objective of the study was to evaluate the capacity of the HBGN to be used as a nanocarrier of the broad-spectrum antibiotic danofloxacin and source of bactericidal Cu2+ ions. Core-shell nanoparticles with specific surface areas close to 800 m2/g and pore volumes around 1 cm3/g were obtained by using hexadecyltrimethylammonium bromide (CTAB) and poly(styrene)-block-poly(acrylic acid) (PS-b-PAA) as structure-directing agents. Flow cytometry studies showed the cytocompatibility of the nanoparticles in MC3T3-E1 pre-osteoblastic cell cultures. Ion release studies confirmed the release of non-cytotoxic concentrations of Cu2+ ions within the therapeutic range. Moreover, it was shown that the inclusion of copper in the system resulted in a more gradual release of danofloxacin that was extended over one week. The bactericidal activity of the nanosystem was evaluated with E. coli and S. aureus strains. Nanoparticles with copper were not able to reduce bacterial viability by themselves and Cu-free HBGN failed to reduce bacterial growth, despite releasing higher antibiotic concentrations. However, HBGN enriched with copper and danofloxacin drastically reduced bacterial growth in sessile, planktonic and biofilm states, which was attributed to a synergistic effect between the action of Cu2+ ions and danofloxacin. Therefore, the nanosystem here investigated is a promising candidate as an alternative for the local treatment of bone infections.

Design of 3D Scaffolds for Hard Tissue Engineering: From Apatites to Silicon Mesoporous Materials.

Advanced bioceramics for bone regeneration constitutes one of the pivotal interests in the multidisciplinary and far-sighted scientific trajectory of Prof. Vallet Regí. The different pathologies that affect osseous tissue substitution are considered to be one of the most important challenges from the health, social and economic point of view. 3D scaffolds based on bioceramics that mimic the composition, environment, microstructure and pore architecture of hard tissues is a consolidated response to such concerns. This review describes not only the different types of materials utilized: from apatite-type to silicon mesoporous materials, but also the fabrication techniques employed to design and adequate microstructure, a hierarchical porosity (from nano to macro scale), a cell-friendly surface; the inclusion of different type of biomolecules, drugs or cells within these scaffolds and the influence on their successful performance is thoughtfully reviewed.

Strontium-Modified Scaffolds Based on Mesoporous Bioactive Glasses/Polyvinyl Alcohol Composites for Bone Regeneration.

In the search of a new biomaterial for the treatment of bone defects resulting from traumatic events, an osteoporosis scenario with bone fractures, tumor removal, congenital pathologies or implant revisions for infection, we developed 3D scaffolds based on mesoporous bioactive glasses (MBGs) (85-x)SiO2-5P2O5-10CaO-xSrO (x = 0, 2.5 and 5 mol.%). The scaffolds with meso-macroporosity were fabricated by pouring a suspension of MBG powders in polyvinyl alcohol (PVA) into a negative template of polylactic acid (PLA), followed by removal of the template by extraction at low temperature. SrO-containing MBGs exhibited excellent properties for bone substitution including ordered mesoporous structure, high textural properties, quick in vitro bioactive response in simulated body fluid (SBF) and the ability of releasing concentrations of strontium ions able to stimulate expression of early markers of osteoblastic differentiation. Moreover, the direct contact of MC3T3-E1 pre-osteoblastic cells with the scaffolds confirmed the cytocompatibility of the three compositions investigated. Nevertheless, the scaffold containing 2.5% of SrO induced the best cellular proliferation showing the potential of this scaffold as a candidate to be further investigated in vitro and in vivo, aiming to be clinically used for bone regeneration applications in non-load bearing sites.

Osteogenic Effect of ZnO-Mesoporous Glasses Loaded with Osteostatin.

Mesoporous Bioactive Glasses (MBGs) are a family of bioceramics widely investigated for their putative clinical use as scaffolds for bone regeneration. Their outstanding textural properties allow for high bioactivity when compared with other bioactive materials. Moreover, their great pore volumes allow these glasses to be loaded with a wide range of biomolecules to stimulate new bone formation. In this study, an MBG with a composition, in mol%, of 80% SiO2⁻15% CaO⁻5% P2O5 (Blank, BL) was compared with two analogous glasses containing 4% and 5% of ZnO (4ZN and 5ZN) before and after impregnation with osteostatin, a C-terminal peptide from a parathyroid hormone-related protein (PTHrP107-111). Zn2+ ions were included in the glass for their bone growth stimulator properties, whereas osteostatin was added for its osteogenic properties. Glasses were characterized, and their cytocompatibility investigated, in pre-osteoblastic MC3T3-E1 cell cultures. The simultaneous additions of osteostatin and Zn2+ ions provoked enhanced MC3T3-E1 cell viability and a higher differentiation capacity, compared with either raw BL or MBGs supplemented only with osteostatin or Zn2+. These in vitro results show that osteostatin enhances the osteogenic effect of Zn2+-enriched glasses, suggesting the potential of this combined approach in bone tissue engineering applications.

Highly-Bioreactive Silica-Based Mesoporous Bioactive Glasses Enriched with Gallium(III).

Beneficial effects in bone cell growth and antibacterial action are currently attributed to Ga3+ ions. Thus, they can be used to upgrade mesoporous bioactive glasses (MBGs), investigated for tissue engineering, whenever they released therapeutic amounts of gallium ions to the surrounding medium. Three gallium-enriched MBGs with composition (in mol %) xSiO2-yCaO-zP2O5-5Ga2O3, being x = 70, y = 15, z = 10 for Ga_1; x = 80, y = 12, z = 3 for Ga_2; and x = 80, y = 15, z = 0 for Ga_3, were investigated and compared with the gallium-free 80SiO2-15CaO-5P2O5 MBG (B). 29Si and 31P MAS NMR analyses indicated that Ga3+ acts as network modifier in the glass regions with higher polymerization degree and as network former in the zones with high concentration of classical modifiers (Ca2+ ions). Ga_1 and Ga_2 exhibited a quick in vitro bioactive response because they were coated by an apatite-like layer after 1 and 3 days in simulated body fluid. Although we have not conducted biological tests in this paper (cells or bacteria), Ga_1 released high but non-cytotoxic amounts of Ga3+ ions in Todd Hewitt Broth culture medium that were 140 times higher than the IC90 of Pseudomonas aeruginosa bacteria, demonstrating its potential for tissue engineering applications.

Prevention of bacterial adhesion to zwitterionic biocompatible mesoporous glasses.

Novel materials, based on Mesoporous Bioactive Glasses (MBGs) in the ternary system SiO2-CaO-P2O5, decorated with (3-aminopropyl)triethoxysilane (APTES) and subsequently with amino acid Lysine (Lys), by post-grafting method on the external surface of the glasses (named MBG-NH2 and MBG-Lys), are reported. The surface functionalization with organic groups did not damage the mesoporous network and their structural and textural properties were also preserved despite the high solubility of MBG matrices. The incorporation of Lys confers a zwitterionic nature to these MBG materials due to the presence of adjacent amine and carboxylic groups in the external surface. At physiologic pH, this coexistence of basic amine and carboxilic acid groups from anchored Lys provided zero surface charge named zwitterionic effect. This behaviour could give rise to potential applications of antibacterial adhesion. Therefore, in order to assess the influence of zwitterionic nature in in vitro bacterial adhesion, studies were carried out with Staphylococcus aureus. It was demonstrated that the efficient interaction of these zwitterionic pairs onto the MBG surfaces reduced bacterial adhesion up to 99.9% compared to bare MBGs. In order to test the suitability of zwitterionic MBGs materials as bone grafts, their cytocompatibility was investigated in vitro with MC3T3-E1 preosteoblasts. These findings suggested that the proposed surface functionalization strategy provided MBG materials with notable antibacterial adhesion properties, hence making these materials promising candidates for local bone infection therapy. STATEMENT OF SIGNIFICANCE: The present research work is focused in finding a preventive treatment of bone infection based on Mesoporous Bioactive Glasses (MBGs) with antibacterial adhesion properties obtained by zwitterionic surface modification. MBGs exhibit unique nanostructural, textural and bioactive characteristics. The novelty and originality of this manuscript is based on the design and optimization of a straightforward functionalization method capable of providing MBGs with zwitterionic surfaces that are able to inhibit bacterial adhesion without affecting their cytocompatibility. This new characteristic enhanced the MBG properties to avoid the bacterial adherence onto the implant surfaces for bone tissue engineering applications. Subsequently, it could help to decrease the infection rates after implantation surgery, which represents one of the most serious complications associated to surgical treatments of bone diseases and fractures.

Nanocrystallinity effects on osteoblast and osteoclast response to silicon substituted hydroxyapatite.

HYPOTHESIS: Silicon substituted hydroxyapatites (SiHA) are highly crystalline bioceramics treated at high temperatures (about 1200°C) which have been approved for clinical use with spinal, orthopedic, periodontal, oral and craniomaxillofacial applications. The preparation of SiHA with lower temperature methods (about 700°C) provides nanocrystalline SiHA (nano-SiHA) with enhanced bioreactivity due to higher surface area and smaller crystal size. The aim of this study has been to know the nanocrystallinity effects on the response of both osteoblasts and osteoclasts (the two main cell types involved in bone remodelling) to silicon substituted hydroxyapatite. EXPERIMENTS: Saos-2 osteoblasts and osteoclast-like cells (differentiated from RAW-264.7 macrophages) have been cultured on the surface of nano-SiHA and SiHA disks and different cell parameters have been evaluated: cell adhesion, proliferation, viability, intracellular content of reactive oxygen species, cell cycle phases, apoptosis, cell morphology, osteoclast-like cell differentiation and resorptive activity. FINDINGS: This comparative in vitro study evidences that nanocrystallinity of SiHA affects the cell/biomaterial interface inducing bone cell apoptosis by loss of cell anchorage (anoikis), delaying osteoclast-like cell differentiation and decreasing the resorptive activity of this cell type. These results suggest the potential use of nano-SiHA biomaterial for preventing bone resorption in treatment of osteoporotic bone.

Local delivery of parathyroid hormone-related protein-derived peptides coated onto a hydroxyapatite-based implant enhances bone regeneration in old and diabetic rats.

Diabetes mellitus (DM) and aging are associated with bone fragility and increased fracture risk. Both (1-37) N- and (107-111) C-terminal parathyroid hormone-related protein (PTHrP) exhibit osteogenic properties. We here aimed to evaluate and compare the efficacy of either PTHrP (1-37) or PTHrP (107-111) loaded into gelatin-glutaraldehyde-coated hydroxyapatite (HA-Gel) foams to improve bone repair of a transcortical tibial defect in aging rats with or without DM, induced by streptozotocin injection at birth. Diabetic old rats showed bone structural deterioration compared to their age-matched controls. Histological and µ-computerized tomography studies showed incomplete bone repair at 4 weeks after implantation of unloaded Ha-Gel foams in the transcortical tibial defects, mainly in old rats with DM. However, enhanced defect healing, as shown by an increase of bone volume/tissue volume and trabecular and cortical thickness and decreased trabecular separation, occurred in the presence of either PTHrP peptide in the implants in old rats with or without DM. This was accompanied by newly formed bone tissue around the osteointegrated HA-Gel implant and increased gene expression of osteocalcin and vascular endothelial growth factor (bone formation and angiogenic markers, respectively), and decreased expression of Sost gene, a negative regulator of bone formation, in the healing bone area. Our findings suggest that local delivery of PTHrP (1-37) or PTHrP (107-111) from a degradable implant is an attractive strategy to improve bone regeneration in aged and diabetic subjects. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2060-2070, 2016.

Response of osteoblasts and preosteoblasts to calcium deficient and Si substituted hydroxyapatites treated at different temperatures.

Hydroxyapatite (HA) is a calcium phosphate bioceramic widely used for bone grafting and augmentation purposes. The biological response of HA can be improved through chemical and microstructural modifications, as well as by manufacturing it as macroporous implants. In the present study, calcium deficient hydroxyapatite (CDHA) and Si substituted hydroxyapatite (SiHA) macroporous scaffolds have been prepared by robocasting. In order to obtain different microstructural properties, the scaffolds have been treated at 700°C and 1250°C. The scaffolds have been characterized and tested as supports for both osteoblast growth and pre-osteoblast differentiation, as fundamental requisite for their potential use in bone tissue engineering. Morphology, viability, adhesion, proliferation, cell cycle, apoptosis, intracellular content of reactive oxygen species and interleukin-6 production were evaluated after contact of osteoblasts-like cells with CDHA and SiHA materials. An adequate interaction of osteoblasts-like cells and preosteoblasts-like cells with all these scaffolds was observed. However, the higher bone cell proliferation and differentiation on CDHA and SiHA scaffolds treated at 1250°C and the lower adsorption of albumin and fibrinogen on these materials in comparison to those treated at 700°C, suggest a better tissue response to CDHA and SiHA materials treated at high temperature.

Towards the Development of Smart 3D "gated scaffolds" for on-command delivery.

A new approach towards the design of "gated scaffolds" based on the combination of capped mesoporous silica nanoparticles (MSNs) with porous biomaterials is reported. Using this approach, a 3D gelatin-based scaffold able to selectively deliver cargo in the presence of an APase enzyme is prepared and tested. This new design opens up the possibility of developing new smart biomaterials with advanced drug-delivery features.

Parathyroid hormone-related protein (107-111) improves the bone regeneration potential of gelatin-glutaraldehyde biopolymer-coated hydroxyapatite.

Biopolymer-coated nanocrystalline hydroxyapatite (HA) made as macroporous foams which are degradable and flexible are promising candidates as orthopaedic implants. The C-terminal (107-111) epitope of parathyroid hormone-related protein (PTHrP) exhibits osteogenic properties. The main aim of this study was to evaluate whether PTHrP (107-111) loading into gelatin-glutaraldehyde biopolymer-coated HA (HAGlu) scaffolds would produce an optimal biomaterial for tissue engineering applications. HAGlu scaffolds with and without PTHrP (107-111) were implanted into a cavitary defect performed in both distal tibial metaphysis of adult rats. Animals were sacrificed after 4 weeks for histological, microcomputerized tomography and gene expression analysis of the callus. At this time, bone healing occurred only in the presence of PTHrP (107-111)-containing HAGlu implant, related to an increase in bone volume/tissue volume and trabecular thickness, cortical thickness and gene expression of osteocalcin and vascular cell adhesion molecule 1, but a decreased gene expression of Wnt inhibitors, SOST and dickkopf homolog 1. The autonomous osteogenic effect of the PTHrP (107-111)-loaded HAGlu scaffolds was confirmed in mouse and human osteoblastic cell cultures. Our findings demonstrate the advantage of loading PTHrP (107-111) into degradable HAGlu scaffolds for achieving an optimal biomaterial that is promising for low load bearing clinical applications.

Nanocrystalline silicon substituted hydroxyapatite effects on osteoclast differentiation and resorptive activity.

In the present study, the effects of nanocrystalline hydroxyapatite (nano-HA) and nanocrystalline Si-substituted hydroxyapatite (nano-SiHA) on osteoclast differentiation and resorptive activity have been evaluated in vitro using osteoclast-like cells. The action of these materials on proinflammatory and reparative macrophage populations was also studied. Nano-SiHA disks delayed the osteoclast differentiation and decreased the resorptive activity of these cells on their surface, as compared to nano-HA samples, without affecting cell viability. Powdered nano-SiHA also induced an increase of the reparative macrophage population. These results along with the beneficial effects on osteoblasts previously observed with powdered nano-SiHA suggest the potential of this biomaterial for modulating the fundamental processes of bone formation and turnover, preventing bone resorption and enhancing bone formation at implantation sites in treatment of osteoporotic bone and in bone repair and regeneration.

In vitro antibacterial capacity and cytocompatibility of SiO2-CaO-P2O5 meso-macroporous glass scaffolds enriched with ZnO.

Zn2+ ions exhibit osteogenic, angiogenic and antimicrobial properties. For this reason, they are often added in small amounts to bioceramics being investigated for bone tissue engineering. In this paper, the cytocompatibility and antibacterial properties of 80% SiO2-15% CaO-5% P2O5 (mol%) mesoporous bioactive glass (MBG) scaffolds substituted with 4.0% and 7.0% of ZnO were studied and compared with the Zn-free scaffold. Cell proliferation, morphology, differentiation and cytotoxic effects of Zn2+ ions released from the samples were examined by culturing human osteoblast-like cells (HOS) osteoblasts both in the presence of sample extracts and on the scaffold surface. The bacterial inhibition capacity of the scaffolds was explored by using Gram-positive Stapylococcus aureus bacteria, responsible for numerous infections in orthopedic surgery, to simulate a severe infection. Our results show that the Zn-MBG scaffolds possess a hierarchical meso-macropore structure suitable for osteoblast growth. Furthermore, the amount of Zn2+ released from the scaffold with 4.0% ZnO was found to be more favorable for HOS cell development than that released from the scaffold including 7.0% ZnO. Zn2+ released to the medium from both scaffolds exhibited antibacterial properties against S. aureus. Thus, the cytocompatibility and the antibacterial ability exhibited by the MBG scaffold containing 4.0% ZnO make it a suitable candidate for bone regeneration applications.

A novel zwitterionic bioceramic with dual antibacterial capability.

A novel zwitterionic SBA-15 type bioceramic with dual antibacterial capability has been synthesized. The co-condensation route has been employed to functionalize SBA-15 with primary and secondary amine groups. The resulting material exhibits textural and nanostructural properties comparable to those of pure silica SBA-15, as confirmed by XRD, HR-TEM and N2 adsorption porosimetry. The presence of -NH3 ⊕/-SiO⊖ and >NH2 ⊕/-SiO⊖zwitterionic pairs on the material surface is evidenced by FTIR and 1H →13C CP/MAS solid state NMR. The homogeneous distribution of this zwitterionic pairs agrees with the results derived from STEM-EDS studies. ζ-Potential measurements indicate that the zwitterionic nature of this material is preserved at the physiological pH of 7.4. In vitro bacterial assays using S. aureus demonstrate that the zwitterionic material is capable of inhibiting 99.9% of the bacterial adhesion compared to pure silica SBA-15. Moreover, cephalexin loading and delivery assays indicate that the zwitterionic sample is capable of releasing antibiotic molecules over long time periods. This dual antibacterial capability, i.e. antibiofouling and bactericidal, opens up promising expectations for the treatment of bone implant infections.