Development of an infection-resistant, bioactive wound dressing surface

Trauma, whether caused by an accident or in an intentional manner, results in significant morbidity and mortality. The goal of this study was to develop a novel biomaterial surface in vitro and ex vivo that provides both localized infection resistance nd hemostatic properties. Our hypothesis is that a combination of specific surface characteristics can be successfully incorporated into a single biomaterial. Functional groups were created with woven Dacron (Cntrl) material via exposure to ethylenediamine (C-EDA). The antibiotic ciprofloxacin (Cipro) was then applied to the C-EDA material using pad/autoclave technique (C-EDA-AB) followed by surface immobilization of the coagulation cascade enzyme thrombin (C-EDA-AB-Thrombin). Antimicrobial activity by the C-EDA-AB surface persisted for 5 days compared with Cntrl and dipped controls, which lasted <1 h. C-EDA-AB-Thrombin surfaces had 2.6- and 105-fold greater surface thrombin activity compared with nonspecifically bound thrombin and Cipro-dyed surfaces, respectively. Surface thrombus formation ex vivo was evident after 1 min of exposure, with thrombus organization evident by 2.5 min. In contrast, C-EDA-AB and Cntrl segments showed only blood protein adsorption on the fibers. Thus, this study demonstrated that Cipro and thrombin can be simultaneously incorporated onto a biomaterial surface while maintaining their respective biological activities.     

Development of an artificial vertebral body using a novel biomaterial,hydroxyapatite/collagen composite

Hydroxyapatite/collagen (HAp/Col) composites having a bone-like nanostructure were synthesized and shaped into implants. This study was designed to develop an artificial vertebra system using this novel implant for anterior fusion of the cervical spine. Anterior fusion was carried out on 6 beagle dogs with the implants adsorbing rhBMP-2 (400 microg/ml). and 9 dogs with the implants without rhBMP-2. In 3 dogs of the rhBMP-treated group, as well as 6 dogs of the non-rhBMP-treated group, the implant was fixed with a poly-L-lactide plate and 2 titanium screws. Implants were taken out after 13 weeks from each 3 dogs in the rhBMP(-):plate(-). rhBMP(-):plate(+) and rhBMP(+):plate(+) groups. Also, the implants were removed from each 3 dogs in the rhBMP(-):plate(+) and rhBMP(+):plate(+) groups after 24 weeks. Histological and radiographical analysis suggested that since the larger part of the composite material was absorbed within 13 weeks, reduction of the intervertebral distance was caused, and that enhancement of callus formation and bone bridging by rhBMP-treatment was effective to prevent collapse of the implant, even though an effect of anterior plate-fixation was not obvious. The HAp/Col implant adsorbing rhBMP-2 may be a suitable replacement for the existing ceramics in anterior interbody fusion of the cervical spine.     

Development of an indirect stereolithography technology for scaffold fabrication with a wide range of biomaterial selectivity

Tissue engineering, which is the study of generating biological substitutes to restore or replace tissues or organs, has the potential to meet current needs for organ transplantation and medical interventions. Various approaches have been attempted to apply three-dimensional (3D) solid freeform fabrication technologies to tissue engineering for scaffold fabrication. Among these, the stereolithography (SL) technology not only has the highest resolution, but also offers quick fabrication. However, a lack of suitable biomaterials is a barrier to applying the SL technology to tissue engineering. In this study, an indirect SL method that combines the SL technology and a sacrificial molding process was developed to address this challenge. A sacrificial mold with an inverse porous shape was fabricated from an alkali-soluble photopolymer by the SL technology. A sacrificial molding process was then developed for scaffold construction using a variety of biomaterials. The results indicated a wide range of biomaterial selectivity and a high resolution. Achievable minimum pore and strut sizes were as large as 50 and 65?μm, respectively. This technology can also be used to fabricate three-dimensional organ shapes, and combined with traditional fabrication methods to construct a new type of scaffold with a dual-pore size. Cytotoxicity tests, as well as nuclear magnetic resonance and gel permeation chromatography analyses, showed that this technology has great potential for tissue engineering applications.     

A review of the biomaterials technologies for infection-resistant surfaces

Anti-infective biomaterials need to be tailored according to the specific clinical application. All their properties have to be tuned to achieve the best anti-infective performance together with safe biocompatibility and appropriate tissue interactions. Innovative technologies are developing new biomaterials and surfaces endowed with anti-infective properties, relying either on antifouling, or bactericidal, or antibiofilm activities. This review aims at thoroughly surveying the numerous classes of antibacterial biomaterials and the underlying strategies behind them. Bacteria repelling and antiadhesive surfaces, materials with intrinsic antibacterial properties, antibacterial coatings, nanostructured materials, and molecules interfering with bacterial biofilm are considered. Among the new strategies, the use of phages or of antisense peptide nucleic acids are discussed, as well as the possibility to modulate the local immune response by active cytokines. Overall, there is a wealth of technical solutions to contrast the establishment of an implant infection. Many of them exhibit a great potential in preclinical models. The lack of well-structured prospective multicenter clinical trials hinders the achievement of conclusive data on the efficacy and comparative performance of anti-infective biomaterials.     

Successful repair of esophageal injury using an elastin based biomaterial patch

An esophageal injury with significant tissue loss is very difficult to repair. We conducted an in vivo study to test our elastin based acellular biomaterial patch to repair such defect. The patch was made from porcine aorta, by decellularization and sterilization. Collagen fibers were preserved to retain mechanical strength and enhance cellular in-growth. Ten domestic pigs underwent right thoracotomy. A 2 cm circular defect was made on the distal esophagus, excising half its circumference, and was repaired using the biomaterial patch and sutures. Soon after the procedure, the animals resumed oral feeding. They were followed for clinical status, weight gain, barium studies, and endoscopic studies, and were killed after 6 weeks to 4 months. All ten animals survived long term, with a procedure success rate of 100% (10 of 10). With the exception of one pneumothorax, no complications occurred, and all animals resumed oral feeding and gained weight. Endoscopic studies showed mucosal coverage by 6 weeks, with minimal stricture at the repair site. Excised specimens showed complete mucosal coverage with regeneration of all three layers. Our biomaterial patch can be used safely and reliably for repair of esophageal injury with significant tissue loss when repaired immediately as in our experiment.     

The selection of appropriate bacterial strains in preclinical evaluation of infection-resistant biomaterials

Implant-related infections are broadly recognized as one of the most serious and devastating complications associated with the use of biomaterials in medical practice. The growing interest and need for the development of implant materials with reduced susceptibility to microbial colonization and biofilm formation has necessitated the development of a series of in vitro and in vivo models for evaluation and preclinical testing. Current technologies provide these investigations with an ample choice of qualitative and quantitative techniques for an accurate assessment of the bioactivity and anti-infective efficacy of any new compound or device. These tests are typically performed using a reference bacterial strain designated as the test or reference strain. Recent molecular epidemiological studies have identified the complex clonal nature of most prevalent etiological agents implicated in implant-associated infections. New information which is continually emerging on the identity and the characteristics of both sporadic and epidemic clones must be considered when selecting a reference. A new emerging requirement is that the strain should be representative of the clones causing clinically relevant infections; they should, therefore, belong to the most prevalent epidemic clones rather than to sporadic ones, which may occur in only 1 out of 200 infections or even fewer. The correct choice of reference strain for preclinical tests is of crucial importance for the clinical significance of the achieved results. In this paper we report our experience and recommendations regarding this issue.     

可注射性UPPE/β-TCP复合材料的制备及其细胞相容性实验研究

目的：探讨可注射性UPPE／β-TCP（不饱和聚磷酸酯邝一磷酸钙）复合材料的制备及其细胞生物相容性。方法：制备UPPE／β-TCP复合材料并测量其理化性质；原代培养小鼠骨髓基质细胞（MSCs），采用浸提法制备UPPE／β-TCP培养基浸提液，用MTr法测定细胞增值率并进行细胞毒性分级；将MSCs与复合材料混合培养并用扫描电镜观察。结果：UPPE／β-TCP复合材料的最大压缩强度和压缩模量分别为94．36±6．96MPa、2096．93±92．86MPa，水接触角为27°；培养的细胞大量增殖，细胞形态良好，UPPE／β—TCP复合材料的毒性分级为0级或者1级，通过扫描电镜观察MSCs与复合材料混合培养的情况，发现MSCs可以黏附生长。结论：制备的可注射性UPPE／β-TCP复合材料有良好的理化性质；体外生物相容性良好。     

Towards an ideal biomaterial for vitreous replacement: Historical overview and future trends

Removal of the natural vitreous body from the eye and its substitution with a tamponade agent may be necessary in cases of complicated retinal detachment. Many materials have been variously proposed and tested over the years in an attempt to find an ideal vitreous substitute. This review highlights the evolution of research in the field of vitreous replacement and chronicles the main advances that have been made in such a context. The suitability and limitations of vitreous tamponade agents and substitutes in current clinical use are examined, and the future promise of experimentally tested biomaterials are described and discussed. Future trends in research are also considered and, specifically, the great potential of polymeric hydrogels is emphasized, as they seem to be very effective in closely mimicking the features of the natural vitreous and they could successfully act as long-term vitreous substitutes without inducing clinical complications in the patient's eye.     

A review of the clinical implications of anti-infective biomaterials and infection-resistant surfaces

Infection is currently regarded as the most severe and devastating complication associated to the use of biomaterials. The important social, clinical and economic impacts of implant-related infections are promoting the efforts to obviate these severe diseases. In this context, the development of anti-infective biomaterials and of infection-resistant surfaces is being regarded as the main strategy to prevent the establishment of implant colonisation and biofilm formation by bacteria. In this review, the attention is focused on the biomaterial-associated infections, from which the need for anti-infective biomaterials originates. Biomaterial-associated infections differ markedly for epidemiology, aetiology and severity, depending mainly on the anatomic site, on the time of biomaterial application, and on the depth of the tissues harbouring the prosthesis. Here, the diversity and complexity of the different scenarios where medical devices are currently utilised are explored, providing an overview of the emblematic applicative fields and of the requirements for anti-infective biomaterials.     

Degradable thiol-acrylate photopolymers: polymerization and degradation behavior of an in situ forming biomaterial

Degradable thiol-acrylate photopolymers are a new class of biomaterials capable of rapidly polymerizing under physiological conditions upon exposure to UV light, with or without added photoinitiators, and to depths exceeding 10 cm. These materials are formed in situ, and the versatility of their chemistry affords a high degree of control over the final material properties. For example, variations in monomer mole fractions directly affect the final network molecular structure, varying the time required to achieve complete mass loss from 25 to 100 days, the molecular weight distributions of the degradation products, and the swelling ratios and compressive moduli throughout degradation. Additionally, varying the mole fraction of multifunctional thiol monomer in the initial reaction mixture controls the concentration of reactive sites in the network available for post-polymerization modification of the polymer.     

Comparison of the thrombogenicity of four types of knitted Dacron arterial graft in an artificial circulation

The thrombogenicity of four types of knitted Dacron arterial graft was compared by measuring the effect of each prosthetic graft on human platelet function in an artificial circulation. The grafts examined were plain knitted (Meadox 'Cooley'), knitted double velour (Meadox 'Microvel'), filamentous external velour (U.S.C.I. 'Sauvage Filamentous') and a plain knitted graft with a pyrolytic carbon coating (Meadox 'Carboknit'). Platelet count, adhesion and percentage aggregation were all decreased during perfusion. The greatest changes in these parameters were produced by the filamentous velour graft and the least by the carbon coated graft. Electron microscopy demonstrated significantly more platelets adherent to the filamentous graft (rho less than 0.01) with changes in platelet morphology indicating activation. These results suggest that the filamentous graft is more thrombogenic than the other grafts.     

Non-invasive optical characterization of biomaterial mineralization

Current approaches to study biomaterial mineralization are invasive and prevent dynamic characterization of this process within the same sample. Polarized light scattering spectroscopy (LSS) may offer a non-invasive alternative for assessing the levels of mineralization as well as some aspects of the organization of the mineral deposits. Specifically, we used LSS to characterize the formation of hydroxyapatite deposits on three types of silk films (water-annealed, methanol-treated and polyaspartic acid (PAA)-mixed) following 1, 3, 5 and 7 cycles of mineralization. We found that the total light scattering intensity provided a quantitative measure of the degree of mineralization as confirmed by thermal gravimetric analysis (TGA). The PAA-mixed silk films yielded the highest level of mineral deposition and the water-annealed ones the least, consistent with the beta sheet content of the films prior to the onset of mineralization. The wavelength dependence of the singly backscattered light was consistent with a self-affine fractal morphology of the deposited films within scales in the range of 150-300nm; this was confirmed by Fourier analysis of scanning electron microscopy (SEM) images of the corresponding films. The deposits of minerals in the water-annealed films were predominantly flake-like, with positively correlated density fluctuations (Hurst parameter, H>0.5), whereas methanol-treated and PAA-mixed silk films resulted in densely-packed, bulk mineral deposits with negatively correlated density fluctuations (H<0.5). Therefore, LSS could serve as a valuable tool for understanding the role of biomaterial properties in mineral formation, and, ultimately, for optimizing biomaterial designs that yield mineral deposits with the desired organization.     

Condensed cellular seeded collagen gel as an improved biomaterial for tissue engineering of articular cartilage

Three-dimensional autologous chondrocyte implantation based on collagen gel as matrix scaffold has become a clinically applied treatment for focal defects of articular cartilage. However, the low biomechanical properties of collagen gel makes intraoperative handling difficult and creates the risk of early damages to the vulnerable implant. The aim of the study was to create a stabilized form of collagen gel and to evaluate its biomechanical and biochemical properties.Collagen type-I gel was seeded with human articular chondrocytes. 20 samples were subject to condensation which was achieved mechanically by compression and filtration. Control samples were left uncondensed. From both types of gels 10 samples were used for initial biomechanical evaluation by means of unconfined compression and 10 samples were cultivated under standard conditions in vitro. Following cultivation the samples were evaluated by conventional histology and immunohistochemistry. The proliferation rate was calculated and matrix gene expression was quantified by real-time PCR.The biomechanical tests revealed a higher force carrying capacity of the condensed specimens. Strain rate dependency and relaxation was seen in both types of collagen gel representing viscoelastic material properties. Cells embedded within the condensed collagen gel were able to produce extracellular matrix proteins and showed proliferation.Condensed collagen gel represents a mechanically improved type of biomaterial which is suitable for three-dimensional autologous chondrocyte implantation.     

Demineralized bone matrix as an osteoinductive biomaterial and in vitro predictors of its biological potential

The osteoinductivity of demineralized bone matrix (DBM) varies from donor to donor as a result of varying levels of multiple growth factors, matrix integrity, and artifacts from material processing. Many in vitro assays are currently used for screening the osteoinductivity of DBM. The objectives of this study were to determine the correlation of specific growth factors and in vitro mitotic stimulation to in vivo ectopic bone formation capacity with a large number of DBM samples. Samples were assayed using ELISA methods for BMP-2/4 and TGF-beta1 (n = 304) and cell proliferation using SAOS-2 osteoblasts (n = 239). All samples were then implanted intramuscularly in the abdomen of nude rats. All in vitro assays showed significant variability for any particular level of ostoinductivity determined by in vivo model. A significant, but only very weak, positive correlation to in vivo results was found for TGF-beta1 (r(2) = 0.016), BMP 2/4 (r(2) = 0.065), and SAOS-2 cell proliferation (r(2) = 0.053). The results of this study amplify the notion that a multitude of factors and their relative interplay, rather than a single factor are likely to determine the potency of any particular lot of DBM.     

Quantification of vascular ingrowth into Dacron velour.

Evaluation of vascular ingrowth into Dacron velour was performed to compare methods and to determine the amount of vascular ingrowth. Microcasting and direct measurement were compared based on their ability to quantify ingrowth, the type of information obtainable, and the time required for data acquisition. Microcasting did not produce results indicative of the actual vascular ingrowth; however, direct measurement of histological slides gave quantifiable data for comparing vascular ingrowth.     

Mechanisms of fibrinogen domains : biomaterial interactions

Spontaneous adsorption of fibrinogen is critical to the pathogenesis of biomaterial-mediated inflammatory responses. However, the mechanism by which adsorbed fibrinogen affects phagocyte responses is still not clear. To investigate the molecular interaction between fibrinogen and biomaterials, fibrinogen fragments (D 100 and E50) were generated and used in the present study. The results indicate that biomaterial : D100 interaction is essential to fibrinogen-mediated inflammatory responses, because biomaterials precoated with D100, but not E50, prompt strong inflammatory responses. Furthermore, the results from in vitro studies show that whole molecule fibrinogen and D100 exhibit very similar protein:surface interactions. Specifically: (1) both D100 and fibrinogen have high affinity for biomaterial surfaces; and (2) the retention rates of adsorbed D 100 in both in vivo and in vitro environments are as high as that for adsorbed fibrinogen. On the other hand, E50 does bind to biomaterials but with low affinity because, once bound, it is not tightly adherent to the biomaterial surfaces. Taken together, the results suggest that the mechanism of fibrinogen-mediated inflammatory responses may involve the following three consecutive events: (1) after contact with blood or tissue fluid, the D domain tends to interact with biomaterial surfaces and is important in the tight binding of fibrinogen to implant surfaces; (2) the biomaterial surface then promotes conformational changes within the D domain, exposing P1 epitope (y 190-202, which interacts with phagocyte Mac-1 integrin); and (3) the engagement of Mac-1 integrin with P1 epitope then triggers subsequent phagocyte adherence and reactions.     

多孔钽应用于骨科的生物材料特性研究进展

骨科传统植入材料的发展经过从不锈钢,钴铬合金,到钛合金的过程。许多关于材料表面涂层和多孔结构的设计被用来提高植入材料与宿主骨之间的生物固定作用。虽然这些材料体现了较好的临床结果,但是它们具有一些与生俱来的局限,比如:低的容积孔隙率、相对高的弹性模量和低的摩擦系数。为了突破了以上     

生物材料修复半月板运动损伤

背景：目前运用人工生物材料干预软骨损伤后愈合与康复的手段日趋成熟与多样,为半月板康复提供了崭新的研究方向。 目的：对半月板运动损伤机制进行探讨,分析生物材料在半月板损伤修复中的作用。 方法：由第一作者检索 1990/2010 PubMed数据及CNKI数据库,选择文章内容与半月板损伤、人工材料治疗措施等相关的文献。 结果与结论：人工生物材料在具体实践运用过程中,由于必须考虑其与人体的生物相容性、形状的匹配、附着性、韧性、强度等,选择理想的植入物较为困难。目前修复半月板应用较多的生物材料主要有透明质酸、胶原、明胶、聚羟乙酸、聚乳酸、聚磷酸钙、不可吸收的聚四氟乙烯、碳素纤维聚合物等。将干细胞定向诱导或经转化生长因子β1基因修饰,通过调节多种细胞的生长和分化,诱导骨髓间充质干细胞向软骨细胞方向分化,并接种于生物支架材料上,为半月板的损伤康复提供了崭新的研究方向。     

Coating of Dacron vascular grafts with an ionic polyurethane: a novel sealant with protein binding properties

The purpose of this study was to develop a novel sealant that would seal prosthetic vascular graft interstices and be accessible for protein binding. Crimped knitted Dacron vascular grafts were cleaned (CNTRL) and hydrolyzed in boiling sodium hydroxide (HYD). These HYD grafts were sealed using an 11% solids solution of a polyether-based urethane with carboxylic acid groups (PEU-D) via a novel technique that employs both trans-wall and luminal perfusion. Carboxylic acid content, determined via methylene blue dye uptake, was 2.3- and 4.2-fold greater in PEU-D segments (1.0+/-0.27 nmol/mg) as compared to HYD and CNTRL segments, respectively. Water permeation through PEU-D graft (1.1+/-2 ml/cm2 min(-1)) was comparable to collagen-impregnated Dacron (9.8+/-10 ml/cm2 min(-1)). Non-specific 125I-albumin (125I-Alb) binding to PEU-D segments (18+/-3 ng/mg) was significantly lower than HYD and CNTRL segments. 125I-Alb linkage to PEU-D using the crosslinker EDC resulted in 5.7-fold greater binding (103+/-2 ng/mg) than non-specific PEU-D controls. However, covalent linkage of 125I-Alb to PEU-D was 4.9- and 5.9-fold less than CNTRL and HYD segments with EDC, respectively. Thus, ionic polyurethane can be applied to a pre-formed vascular graft, seal the interstices and create "anchor" sites for protein attachment.