RESUMO
In this tutorial review we present the process of the development of functional implants using mesoporous silica. The different steps from chemical synthesis and physicochemical characterization followed by in vitro testing in cell culture assays to clinically relevant in vivo animal studies are examined. Since the end of the 1990s, mesoporous silicas have been considered as biomaterials. Numerous investigations have demonstrated their non-toxic and biocompatible properties. These qualities in combination with the unique properties of high surface area and pore volume, uniform and tunable pore sizes and chemical modifiability are the reasons for the great scientific interest in this field. Here we show that besides bulk materials or mesoporous silica nanoparticles, mesoporous silica films are highly promising as coatings on medical prostheses or implants. We report on the development of functionalized mesoporous silica materials specifically for middle ear applications. Middle ear prostheses are used to restore the sound transmission through this air-filled cavity when the small bones of the middle air (the ossicular chain) have been destroyed by disease or by accidents. In addition to optimal restoration of sound transmission, this technique bears several challenges, e.g. an ongoing bacterial infection or the displacement of the prosthesis due to insufficient fixation. To improve the healing process, a mesoporous silica coating was established on ceramic middle ear prostheses, which then served as a base for further functionalizations. For example, the bone growth factor BMP2 was locally attached to the coating in order to improve the fixation of the prosthesis by forming a bony connection to the remainder of the ear bones. Further, an implant-based local drug delivery system for the antibiotic ciprofloxacin was developed with the aim of fighting bacterial infections. Further possibilities using mesoporous silica nanoparticles as part of a composite on an implant are briefly discussed.
Assuntos
Materiais Biocompatíveis/química , Dióxido de Silício/química , Orelha Média , Tamanho da Partícula , Porosidade , Propriedades de SuperfícieRESUMO
Biocompatibility and degradation of magnesium sponges (alloy AX30) with a fluoride (MgF(2) sponge, n = 24, porosity 63 ± 6 %, pore size 394 ± 26 µm) and with a fluoride and additional calcium-phosphate coating (CaP sponge, n = 24, porosity 6 ± 4 %, pore size 109 ± 37 µm) were evaluated over 6, 12 and 24 weeks in rabbit femurs. Empty drill holes (n = 12) served as controls. Clinical and radiological examinations, in vivo and ex vivo µ-computed tomographies and histological examinations were performed. Clinically both sponge types were tolerated well. Radiographs and XtremeCT evaluations showed bone changes comparable to controls and mild gas formation. The µCT80 depicted a higher and more inhomogeneous degradation of the CaP sponges. Histomorphometrically, the MgF(2) sponges resulted in the highest bone and osteoid fractions and were integrated superiorly into the bone. Histologically, the CaP sponges showed more inflammation and lower vascularization. MgF(2) sponges turned out to be better biocompatible and promising, biodegradable bone replacements.
Assuntos
Substitutos Ósseos , Transplante Ósseo/instrumentação , Fosfatos de Cálcio/química , Materiais Revestidos Biocompatíveis , Fluoretos/química , Magnésio/química , Implantes Absorvíveis , Ligas/síntese química , Ligas/química , Ligas/farmacologia , Animais , Substitutos Ósseos/síntese química , Substitutos Ósseos/química , Substitutos Ósseos/farmacologia , Materiais Revestidos Biocompatíveis/síntese química , Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/farmacologia , Feminino , Fêmur/diagnóstico por imagem , Fêmur/efeitos dos fármacos , Fêmur/cirurgia , Implantes Experimentais , Teste de Materiais , Coelhos , RadiografiaRESUMO
The performance of biomaterials is often compromised by bacterial infections and subsequent inflammation. So far, the conventional analysis of inflammatory processes in vivo involves time-consuming histology and biochemical assays. The present study employed a mouse model where interferon beta (IFN-ß) is monitored as a marker for non-invasive rapid detection of inflammation in implant-related infections. The mouse model comprises subcutaneous implantation of morphologically modified titanium, followed by experimental infections with four taxonomically diverse oral bacteria: Streptococcus oralis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Treponema denticola (as mono culture or selected mixed-culture). IFN-ß expression increased upon infections depending on the type of pathogen and was prolonged by the presence of the implant. IFN-ß expression kinetics reduced with two mixed species infections when compared with the single species. Histological and confocal microscopy confirmed pathogen-specific infiltration of inflammatory cells at the implant-tissue interface. This was observed mainly in the vicinity of infected implants and was, in contrast to interferon expression, higher in infections with dual species. In summary, this non-invasive mouse model can be used to quantify longitudinally host inflammation in real time and suggests that the polymicrobial character of infection, highly relevant to clinical situations, has complex effects on host immunity.
RESUMO
The objective of this study is to evaluate the suitability of a mouse middle ear model for testing ossicular replacement materials. Twenty-four BALB/c mice are implanted with the bioglass-ceramic Bioverit II which is coated with a silica-nanostructure or with plain Bioverit II as a control. After 2, 6, and 12 weeks, 4 mice per group are sacrificed and both complete petrous bones are analyzed histologically. All implants revealed in situ an incipient growth of thin connective tissue layers over the surface, followed by a spreading of epithelial cells. The osseogenic response which is increasing with time is more intense in the coated Bioverit II specimens. The absence of inflammatory cells suggests an excellent biocompatibility of the silica nano structure. As the results are comparable to a study with the same materials in rabbits, the mouse model described is highly suitable for evaluation of new ossicular replacement materials. Additionally, by gene expression analysis a more detailed insight into cellular interactions of the middle ear is offered.
Assuntos
Cerâmica/química , Materiais Revestidos Biocompatíveis/química , Orelha Média/transplante , Prótese Ossicular , Dióxido de Silício/química , Animais , Orelha Média/ultraestrutura , Feminino , Camundongos , Camundongos Endogâmicos BALB C , Modelos Animais , Nanoestruturas/química , Osteogênese , Porosidade , Coelhos , Fatores de TempoRESUMO
Magnesium alloys have promising mechanical and biological properties for the development of degradable implants. However, rapid implant corrosion and gas accumulations in tissue impede clinical applications. With time, the implant degradation rate is reduced by a highly biocompatible, phosphate-containing corrosion layer. To circumvent initial side effects after implantation it was attempted to develop a simple in vitro procedure to generate a similarly protective phosphate corrosion layer. To this end magnesium samples were pre-incubated in phosphate solutions. The resulting coating was well adherent during routine handling procedures. It completely suppressed the initial burst of corrosion and it reduced the average in vitro magnesium degradation rate over 56 days almost two-fold. In a small animal model phosphate coatings on magnesium implants were highly biocompatible and abrogated the appearance of gas cavities in the tissue. After implantation, the phosphate coating was replaced by a layer with an elemental composition that was highly similar to the corrosion layer that had formed on plain magnesium implants. The data demonstrate that a simple pre-treatment could improve clinically relevant properties of magnesium-based implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1622-1635, 2017.
Assuntos
Materiais Revestidos Biocompatíveis , Implantes Experimentais , Magnésio , Teste de Materiais , Fosfatos , Animais , Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/farmacologia , Corrosão , Feminino , Magnésio/química , Magnésio/farmacologia , Camundongos , Camundongos Endogâmicos BALB C , Fosfatos/química , Fosfatos/farmacologiaRESUMO
To evaluate the inflammatory potential of implants a bioluminescent imaging assay was developed using luciferase-expressing bone marrow cells that were injected into the blood circulation of wild-type mice. After subcutaneous implantation of titanium discs as an example for a clinically established biocompatible material, the luminosity was modest. Similarly, low luminosity signals were generated by pure magnesium implants that were used to represent metallic alloys that are presently under investigation as novel degradable implant materials. Increased luminosity was observed in response to degradable polymeric PLGA implants. Surgical wounds induced a basic luminescent response even in the absence of an implant. However, the material-independent response to injury could be minimized using injectable microparticle suspensions. In parallel with the resorption of biodegradable microparticles, the signal induced by PLGA declined faster when compared to non-degradable polystyrene suspensions. By using an interferon type I inducible Mx2 promoter construct to drive luciferase gene expression, the highest luminosity was observed in response to bacteria, indicating that the system could also be employed to monitor implant infections. Overall, labeled bone marrow cells yielded specific, well-defined localized signals that correlated with the inflammatory responses to implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2149-2158, 2016.
Assuntos
Implantes Absorvíveis , Células da Medula Óssea , Transplante de Medula Óssea , Rastreamento de Células/métodos , Aloenxertos , Animais , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Inflamação/metabolismo , Inflamação/patologia , Camundongos , Modelos Biológicos , Poliestirenos/efeitos adversos , Poliestirenos/farmacologiaRESUMO
As an alternative to degradable organic coatings the possibility of using layered double hydroxides (LDHs) to generate implant coatings for controlled drug delivery was evaluated in vivo and in vitro. Coatings prepared from LDH suspensions dissolved slowly and appeared compatible with cultured cells. LDH coatings loaded with an antibiotic resulted in antibacterial effects in vitro. The LDH coating prolonged the drug release period and improved the proliferation of adherent cells in comparison to pure drug coatings. However, during incubation in physiological solutions the LDH coatings became brittle and pieces occasionally detached from the surface. For stress protection porous titanium implants were investigated as a substrate for the coatings. The pores prevented premature detachment of the coatings. To evaluate the coated porous implants in vivo a mouse model was established. To monitor bacterial infection of implants noninvasive in vivo imaging was used to monitor luminescently labeled Pseudomonas aeruginosa. In this model porous implants with antibiotic-loaded LDH coatings could antagonize bacterial infections for over 1 week. The findings provide evidence that delayed drug delivery from LDH coatings could be feasible in combination with structured implant surfaces.
Assuntos
Antibacterianos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Hidróxidos/farmacologia , Titânio/farmacologia , Animais , Ciprofloxacina/farmacologia , Preparações de Ação Retardada/farmacologia , Feminino , Camundongos , Camundongos Endogâmicos BALB C , Modelos Animais , Células NIH 3T3 , Porosidade , VolatilizaçãoRESUMO
Due to constant competition conditions, track cycling can be accurately modeled through physiological and biomechanical means. Mathematical modeling predicts an average workload of 520 W for every team member for a new team pursuit world record. Performance in team pursuit racing is highly dependent on aerobic capacity, anaerobic skills, and aerodynamic factors. The training concept of the 2000 record-breaking team pursuit team was based on unspecific training of these qualities and periodical, short-term recall of previously acquired track specific skills. Aerobic performance was trained through high overall training mileage (29,000-35,000 km.yr-1) with workload peaks during road stage races. Before major track events, anaerobic performance, and track-specific technical and motor skills were improved through discipline-specific track training. Training intensities were monitored through heart rate and lactate field tests during defined track-training bouts, based on previously performed laboratory exercise tests. During pursuit competition, analysis of half-lap split times allowed an estimation of the individual contribution of each rider to the team's performance and thereby facilitated modifications in team composition to optimize race speed. The theoretically predicted performance necessary for a new world record was achieved through careful planning of training and competition schedules based on a concise theoretical concept and the high physiological capacities of the participating athletes.
Assuntos
Ciclismo/fisiologia , Comportamento Competitivo/fisiologia , Educação Física e Treinamento/métodos , Antropometria , Humanos , Modelos Biológicos , Valor Preditivo dos Testes , Medicina Esportiva/métodos , Análise e Desempenho de TarefasRESUMO
A small animal model was established to evaluate the potential of iron as a degradable implant material. After insertion into the tail of mice, the implants gradually degraded over a clinically relevant time period of several months. Histological analysis and gene expression data from whole-genome microarray analyses indicated a limited inflammatory reaction. No evidence of cellular responses to excess iron ions was detected, suggesting that the iron degradation products were metabolically inactive. Iron-rich compounds could be detected in the vicinity of the implant and in individual cells distant from the implantation site. These results demonstrate that the mouse model could be useful for the primary in vivo evaluation of novel implant materials and that iron degradation products can accumulate in diverse organs of the body.
Assuntos
Implantes Absorvíveis , Materiais Biocompatíveis/metabolismo , Ferro/metabolismo , Animais , Materiais Biocompatíveis/química , Corrosão , Feminino , Perfilação da Expressão Gênica , Ferro/química , Teste de Materiais , Camundongos , Camundongos Endogâmicos BALB C , CicatrizaçãoRESUMO
Hydrogel systems based on hydroxyethyl starch-polyethylene glycol methacrylate (HES-P(EG)(6)MA) or hydroxyethyl starch methacrylate (HES-MA) were used to assess the protein release behavior. Here, we analyzed the in vitro release of FITC-anti-human antibodies incorporated in either HES-P(EG)(6)MA or HES-MA hydrogel delivery systems in PBS or human serum. In addition, hydrogel disks and microparticles prepared from the two polymers were subcutaneously implanted in BALB/c mice. The in vivo release of FITC-IgG was non-invasively monitored by an in vivo imaging system (IVIS 200) over a time period of up to 3 months. The imaging system allowed to asses individual animals over time, therefore only a small number of animals was required to obtain high quality data. The reduction in fluorescence intensity at the site of administration was compared to in vitro release profiles. These investigations demonstrated a sustained release from HES-MA hydrogel disks compared to rapidly degrading HES-P(EG)(6)MA disks and microparticles. The sustained release from HES-MA disks could be further optimized by using increased polymer concentrations. Human serum as in vitro release medium reflected better the in vivo release from HES-P(EG)(6)MA systems than PBS, suggesting that the presence of organic substances like proteins or lipids may play a significant role for the release kinetics.
Assuntos
Sistemas de Liberação de Medicamentos/métodos , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Derivados de Hidroxietil Amido/química , Imunoglobulina G/administração & dosagem , Metacrilatos/química , Polietilenoglicóis/química , Implantes Absorvíveis , Animais , Fluoresceína-5-Isotiocianato/análise , Cabras , Humanos , Imunoglobulina G/análise , Masculino , Camundongos , Camundongos Endogâmicos BALB CRESUMO
Infection with hepatitis C virus (HCV) is a major medical problem with over 170 million people infected worldwide. Substantial morbidity and mortality are associated with hepatic manifestations (cirrhosis and hepatocellular carcinoma), which develop with increasing frequency in people infected with HCV for more than 20 years. Less well known is the burden of HCV disease associated with extrahepatic manifestations (diabetes, B-cell proliferative disorders, depression, cognitive disorders, arthritis and Sjögren's syndrome). For patients infected with genotype 1 HCV, treatment with polyethylene glycol decorated interferon (peginterferon) α and ribavirin (PR) is associated with a low (40-50%) success rate, substantial treatment-limiting side effects and a long (48-week) duration of treatment. In the past 15 years, major scientific advances have enabled the development of new classes of HCV therapy, the direct-acting antiviral agents, also known as specifically targeted antiviral therapy for hepatitis C (STAT-C). In combination with PR, the HCV NS3-4A protease inhibitor telaprevir has recently been approved for treatment of genotype 1 chronic HCV in the United States, Canada, European Union and Japan. Compared with PR, telaprevir combination therapy offers significantly improved viral cure rates and the possibility of shortened treatment duration for diverse patient populations. Developers of innovative drugs have to blaze a new path with few validated sign posts to guide the way. Indeed, telaprevir's development was once put on hold because of its performance in a standard IC(50) assay. Data from new hypotheses and novel experiments were required to justify further investment and reduce risk that the drug might fail in the clinic. In addition, the poor drug-like properties of telaprevir were a formidable hurdle, which the manufacturing and formulation teams had to overcome to make the drug. Finally, novel clinical trial designs were developed to improve efficacy and shorten treatment in parallel instead of sequentially. Lessons learned from the development of telaprevir suggest that makers of innovative medicines cannot rely solely on traditional drug discovery metrics, but must develop innovative, scientifically guided pathways for success.
Assuntos
Descoberta de Drogas , Hepacivirus/genética , Hepatite C Crônica/tratamento farmacológico , Oligopeptídeos/química , Inibidores de Proteases/química , Proteínas não Estruturais Virais/antagonistas & inibidores , Animais , Ensaios Clínicos como Assunto , Genótipo , Hepacivirus/efeitos dos fármacos , História do Século XX , História do Século XXI , Humanos , Interferon-alfa/efeitos adversos , Interferon-alfa/uso terapêutico , Camundongos , Oligopeptídeos/história , Oligopeptídeos/uso terapêutico , Polietilenoglicóis/efeitos adversos , Polietilenoglicóis/uso terapêutico , Inibidores de Proteases/história , Inibidores de Proteases/uso terapêutico , Proteínas Recombinantes/efeitos adversos , Proteínas Recombinantes/uso terapêutico , Ribavirina/efeitos adversos , Ribavirina/uso terapêuticoRESUMO
Due to its ability to induce de novo bone formation the differentiation factor bone morphogenetic protein 2 (BMP2) is often used to enhance the integration of bone implants. With the aim of reducing possible high dose side-effects and to lower the costs, in order to produce affordable implants, we developed a simple and fast method for the immobilization of BMP2 on silica-based surfaces using silane linkers which carry amino or epoxy functions. We put an especial emphasis on the influence of the nanoscale surface topography of the silica layer. Therefore, we chose glass (for control experiments) and Bioverit® II (as a typical implant base material) as support materials and coated these substrates with unstructured or nanoporous amorphous silica layers for comparison. Immobilized BMP2 was quantified by two different methods: by ELISA and by a cell-based assay for active BMP2. These tests probe for immunologically and biologically active BMP2, respectively. The results show that the amino functionalization is better suited for immobilizing the protein. Strikingly, a considerably higher amount of BMP2 could be immobilized on coated Bioverit® II surfaces compared with coated glass substrates, which was presumably due to the macroscopic roughness of the Bioverit® II substrates. In addition, it was found that the nanoporous silica coatings on Bioverit® II substrates were able to bind more BMP2 than the unstructured ones.
Assuntos
Materiais Biocompatíveis/química , Proteína Morfogenética Óssea 2/metabolismo , Proteínas Imobilizadas/metabolismo , Silanos/química , Dióxido de Silício/química , Cerâmica/química , Materiais Revestidos Biocompatíveis , Vidro/química , Humanos , Teste de Materiais , Nanoporos/ultraestrutura , Propriedades de Superfície , Difração de Raios XRESUMO
Cochlear implants (CIs) can restore hearing in deaf patients by electrical stimulation of the auditory nerve. To optimize the electrical stimulation, the number of independent channels must be increased by reduction of connective tissue growth on the electrode surface and selective neuronal cell contact. The femtosecond laser microstructuring of the electrode surfaces was performed to investigate the effect of fibroblast growth on the implant material. A cell culture model system was established to evaluate cell-material interactions on these microstructured CI-electrode materials. Fibroblasts were used as a cell culture model for connective tissue formation, and differentiating neuronal-like cells were employed to represent neuronal cells. For nondestructive microscopic examination of living cells on the structured surfaces, the cells were genetically modified to express green fluorescent protein. To investigate the special interaction between the electrode material and the tissue we used electrode material which is originally used for manufacturing CI for human applications, namely platinum (contact material) and silicone carrier material (LSR 30, HCRP 50). Microstructures of various dimensions (groove width 1-10 microm) were generated by using femtosecond laser ablation. The highest fibroblast growth rate was observed on platinum, but cell growth rates on the silicone carrier material were lower. Microstructuring reduced fibroblast cell growth on platinum significantly. On the microstructured silicone, a trend to lower cell growth rates was observed. In addition, microgrooves on platinum surfaces can direct neurite outgrowth parallel to the grooves. The implications of the results are discussed with respect to the design of a microstructured CI surface.