Presence Of Biomaterials Research Articles

Optimizing combination of feature extraction and classifiers in supervised classification of cells images

Developments in the medical field have opened the opportunity to conduct analyses on a personalized patient level. One of the important analyses that can be conducted is the cellular response to engineered materials, and the most appropriate non-invasive methods are imaging. These images of the cells are unstained brightfield images, as they are acquired from multiparametric microfluidic chambers in the presence of biomaterials and fluids that can change the optical path length over time as the cells’ health state is monitored. These experimental conditions lead to an image dataset with unique illumination, texture, and noise spectrum. This study explores the optimization of supervised cell classification by combining feature extraction architectures and machine learning classifiers, with a focus on applications in biomaterial risk assessment. Brightfield microscopy images of three cell types (A549, BALB 3T3, and THP1) were analyzed to evaluate the impact of Inception V3, Squeeze Net, and VGG16 architectures paired with classifiers including KNN, Decision Tree, Random Forest, AdaBoost, Neural Networks, and Naïve Bayes. Dimensionality reduction using Information Gain was applied to improve computational efficiency and accuracy. Butterworth filters with varying parameters were used to balance the enhancement of image features and noise removal, improving classification performance in certain cases. Experimental results demonstrate that the VGG16 architecture, when paired with Neural Networks, achieves higher classification accuracy as measured by different metrics. The improved accuracy when using Butterworth filters compared to the unfiltered dataset and the differences between various Butterworth filters indicate the importance of optimizing filter parameters for these types of images.

Efficiency of cavitary varnishes containing experimental bioglass particles in the occlusion of dentinal tubules.

This research aims to evaluate the efficiency of cavitary varnishes containing experimental bioglasses in the occlusion of dentinal tubules. One hundred and sixty-eight cervical buccal dentin samples were obtained from bovine teeth. Samples were randomized into the following groups: I. Distilled Water (DW); II. Cavity Varnish (CV); III. Colgate® Sensitive Pro-Relief™ (CS); IV. 45S5 Bioglass (45S5); V. KSr Bioglass strontium potassium (KSr); VI. P Bioglass phosphorus (P); and VII. PSi Bioglass phosphorus silica (PSi). The treatments were applied to the surfaces of the samples, which were then subjected to simulated brushing. The samples were analyzed for a) characterization of bioactive glasses; b) surface roughness; c) descriptive analysis of the dentin surface; d) total versus occluded number of dentinal tubules; e) diameter of the dentinal tubules; f) chemical composition of the dentin surfaces, and g) dentin permeability. All groups treated with biomaterials without the brushing challenge showed an increase in roughness and (total or partial) occlusion of the dentinal tubules. The PSi group had the best values for occlusion, while the KSr group had the highest calcium and phosphorus concentrations. After the brushing challenge the roughness was controlled by the presence of biomaterials; 45S5, KSr, and PSi showed occlusion of the dentin tubules. All bioactive glasses showed reduced tooth permeability compared to distilled water. The PSi group had the smallest tubule diameter and highest phosphorus concentration. KSr and PSi bioglasses are promising materials for dentin occlusion and remineralization and are promising new biomaterials for the treatment of dentin hypersensitivity.

Clinical and demographic study of non-tuberculous mycobacterial ocular infections in South India

PurposeTo describe demographics, risk factors, antibiotic susceptibility, management and outcomes of ocular infections caused by non-tuberculous mycobacteria (NTM). MethodsA retrospective review of medical case records and microbiology records of patients with ocular infections that were culture positive for non-tuberculous Mycobacteria from January 2014 to December 2018 was done. Antibiotic susceptibility profile was done based on the CLSI guidelines. Laboratory diagnosis for the NTM Species was done by conventional microbiological methods. The species identification was done for stored isolated utilizing polymerase chain reaction targeting 16S rDNA and rpoB gene, followed by DNA sequencing and phylogenetic analysis. ResultsTwenty patients with NTM ocular infections were identified during the study period. A majority of cases presented as 12 infectious keratitis (60%) and three suture-related corneal infiltrates (15%). Common risk factors were history of trauma in 9 (45%) patients and history of ocular surgery in 5 (25%) patients. Patients were treated with combination of amikacin and flouroquinolones/chloramphenicol (70%) and surgical interventions were performed in 25% cases. Only twelve isolates were stored and ten isolates were identified as the M. abscessus subsp. abscessus and two isolates as M. abscessus subsp. massiliense by sequencing and phylogenetic analysis. Majority of the NTM were sensitive to amikacin (75%) followed by moxifloxacin, ciprofloxacin, cephotaxime and tobramycin (35%). ConclusionHigh degree of clinical suspicion, multidrug antibiotic therapy and timely surgical intervention in patients with NTM infections, are advised for better clinical outcomes. Prior ocular trauma, prior ocular surgery and presence of biomaterials were the major predisposing factors. Earlier surgical intervention in cases where abscesses or biomaterials are involved, is necessary for rapid recovery.

Utilizing eco-friendly kaolinite-biochar composite adsorbent for removal of ivermectin in aqueous media

Several emerging contaminants are currently used in an unregulated manner worldwide, resulting in their increasing stringent limits in water by regulatory bodies. Thus, more viable and cheap treatment technologies are required. Recently, synergistic combinations of low-cost adsorbents have shown huge potential for aqueous toxic metals adsorption in water treatment processes. However, there is dearth of data on their potential for emerging contaminant removal. Here, low-cost kaolinite (KAC) clay was synergistically combined with blended Carica papaya or pine cone seeds, and calcined to obtain composites of KAC-Carica papaya seeds (KPA) and KAC-pine cone seeds (KPC). These adsorbents were characterized and evaluated for ivermectin adsorption at varying operating times (15–1440 min), pH (3–11), concentration (100–600 μg/L), and temperature (19.5–39.5 °C), as well as testing adsorbents’ reusability. The composites exhibited marked property differences including over 250% cation exchange capacity increases and ≥50% surface area decreases, but unchanged KAC clay primary lattice structure. Ivermectin adsorption data were explained using kinetics and adsorption isotherm models. The rate of adsorption on KAC decreased over time, while rates for KPA and KPC increased until equilibrium at 180 min; the presence of biomaterials in the composites conferred better ivermectin adsorption and retention under continuous agitation. The adsorbents exhibited dual adsorption peaks one each at the acidic and alkaline pH regions as solution pH changed from 3 to 11. The rate data fitted (≥0.9232) the homogeneous fractal Pseudo-Second Order (FPSO) better than any other kinetics model, as well as the Freundlich adsorption isotherm model (≥0.9887); these indicate complex interactions between ivermectin and the adsorption sites of both composites. Ambient temperature increase up to ≈30 °C caused higher ivermectin adsorption but beyond this temperature there was drastic drop in adsorption. The KPA and KPC adsorption capacities are 105.3 and 115.8 μg/g, respectively. The KPC was better at reducing ivermecitn in low-concentration solution (≈75 μg/L) to less than 5.0 μg/L compared with KPA with ≈20.0 μg/L. Though KPC showed better efficiency in adsorption capacity and lowering concentration in low-concentration solutions, KPA exhibited better reusability with 83.5 and 67.5% initial adsorption strengths remaining in the second and third adsorption cycles, respectively, compared to the 73.8 and 58.8% for the KPC. These results indicate that KPA and KPC composites have the economic potential for application in water treatment processes.

Synthesis of thermogel modified with biomaterials as carrier for hUSSCs differentiation into cardiac cells: Physicomechanical and biological assessment

One of the major challenges in cardiac cell therapy is cell death and low rate of cardiac differentiation. In this regard, a series of thermosensitive and injectable hydrogels with similar physicomechanical properties of cardiac tissue can be an ideal candidate for delivering human unrestricted somatic stem cells (hUSSCs) and improve the quality of cell therapy. Here, we designed N-isopropylacrylamide/acrylic acid/N-acryloxysuccinimide/2-hydroxyethyl methacrylate-poly lactide (NIPAAm/AAc/NAS/HEMAPLA) hydrogel via ring-opening polymerization for encapsulation of the cells. To improve biological activities, biomaterials like hyaluronic acid (HA), Aloe vera (AV), and silk fibroin (SF) were added with pure hydrogel (Pgel). The modulus of hydrogels was estimated between 68.1 and 74.63 kPa that was similar to the normal cardiac modulus. Moreover, the elastic region increased by adding biomaterials to Pgel. The results of RT-PCR and ICC demonstrated that the most expression of early genes (GATA4, NKX2.5) was related to Pgel/AV/SF group. In contrast, the highest expression of other genes (GJA1, TNNI3, MYH6) was observed in Pgel/HA/SF. The presence of biomaterials in the structure of hydrogel can play a key role in cell fate and the induction of cell differentiation as a factor influencing mechanotransduction. These hydrogels hold an excellent promise to deliver hUSSCs into damaged tissue for cardiac regeneration.

Trabecular architecture during the healing process of a tibial diaphysis defect

The adaptation of trabecular bone microstructure to mechanical loads has been intensively investigated. However, loading-unrelated aspects of trabecular architecture remain unclear. We used synchrotron radiation-based X-ray microtomography to study the 3D microarchitecture of newly formed trabecular tissue in a defect produced in the cortical region of the rat tibia diaphysis, in the absence (7, 14, and 21 days) or the presence (21 days) of carbonated hydroxyapatite/alginate (cHA) microspheres. This work provides the first evidence that the woven bone trabecular network, formed during the healing process, displays a well-organized 3D microarchitecture consisting of nodes with 3 (3-N), 4 (4-N) and 5 (5-N) connecting trabeculae, with a mean relative abundance of (3-N)/(4-N)/(5-N) = 66/24/7, for the analyzed periods. The measured inter-trabecular angles (ITA) distribution presented a Gaussian profile, with mean value at 115° for 3-N nodes, and 105° for 4-N nodes, close to the angles of idealized 3D regular structures (120° and 109.5°, respectively). Changes in the dispersion of ITA distribution suggested that a highly symmetric trabecular fabric organized under tensegrity principles is formed early during the bone healing process. Post-implantation, cHA disaggregated into multiple fragments (~20–400 μm), stimulating osteoconduction and bone growth toward the interior of the medullary cavity. The presence of biomaterials in bone defects affected the trabecular dimensions; however, it did not interfere with the formation of geometrical motifs with topological parameters similar to those found in the sham-defects. Statement of SignificanceThe trabecular bone microstructure enables the tissue to meet the necessary mechanical and functional demands. However, the process of trabecular microarchitecture formation during healing, in the absence or presence of a bone graft, is not yet well understood. This work demonstrated that, from the beginning of its formation in cortical bone defects, the woven-bone trabecular network is spatially organized according to the principle of tensegrity. This microarchitecture is comprised of highly symmetric geometric motifs and is an intrinsic characteristic of trabecular growth, regardless of hierarchical scale or mechanical stimulation. The addition of a biodegradable nanostructured calcium phosphate graft did not disrupt trabecular microarchitecture; however, graft biodegradation should be controlled to optimize the reproduction of intrinsic trabecular motifs throughout the defect.

Transient Receptor Potential Vanilloid 4 Is Required for Foreign Body Response and Giant Cell Formation

The presence of biomaterials and devices implanted into soft tissue is associated with development of a foreign body response (FBR), a chronic inflammatory condition that can ultimately lead to implant failure, which may cause harm to or death of the patient. Development of FBR includes activation of macrophages at the tissue-implant interface, generation of destructive foreign body giant cells (FBGCs), and generation of fibrous tissue that encapsulates the implant. However, the mechanisms underlying the FBR remain poorly understood, as neither the materials composing the implants nor their chemical properties can explain triggering of the FBR. Herein, we report that genetic ablation of transient receptor potential vanilloid 4 (TRPV4), a Ca2+-permeable mechanosensitive cation channel in the transient receptor potential vanilloid family, protects TRPV4 knockout mice from FBR-related events. The mice showed diminished collagen deposition along with reduced macrophage accumulation and FBGC formation compared with wild-type mice in a s.c. implantation model. Analysis of macrophage markers in spleen tissues and peritoneal cavity showed that the TRPV4 deficiency did not impair basal macrophage maturation. Furthermore, genetic deficiency or pharmacologic antagonism of TRPV4 blocked cytokine-induced FBGC formation, which was restored by lentivirus-mediated TRPV4 reintroduction. Taken together, these results suggest an important, previously unknown, role for TRPV4 in FBR.

Western blot analysis of cells encapsulated in self-assembling peptide hydrogels.

Continuous optimization of in vitro analytical techniques is ever more important, especially given the development of new materials for tissue engineering studies. In particular, isolation of cellular components for downstream applications is often hindered by the presence of biomaterials, presenting a major obstacle in understanding how cell-matrix interactions influence cell behavior. Here, we describe an approach for western blot analysis of cells that have been encapsulated in self-assembling peptide hydrogels (SAPHs), which highlights the need for complete solubilization of the hydrogel construct. We demonstrate that both the choice of buffer and multiple cycles of sonication are vital in obtaining complete solubilization, thereby enabling the detection of proteins otherwise lost to SAP aggregation. Moreover, we show that the presence of self-assembling peptides (SAPs) does not interfere with the standard immunoblotting technique, offering the potential for use in more full-scale proteomic studies.

Evaluation of osteogenic markers in the differentiation of murine preosteoblasts during the interaction with polyurethane/nanohydroxyapatite biomaterials

Event Abstract Back to Event Evaluation of osteogenic markers in the differentiation of murine preosteoblasts during the interaction with polyurethane/nanohydroxyapatite biomaterials Georgina Carbajal-De La Torre1, Ana Edith A. Higareda-Mendoza2, Ana Beatriz A. Martinez-Valencia1, Marco Aurelio Pardo Galvan3, Tania Saluen Gaytan Compean2, Lucia Marquez-Perez1 and Marco Antonio Espinosa-Medina1 1 Universidad Michoacana de San Nicolas de Hidalgo, Bioengineering, Mexico 2 Universidad Michoacana de San Nicolás de Hidalgo, Division of Graduate Studies, Faculty of Medical and Biological Sciences Dr. Ignacio Chavez, Mexico 3 Universidad Michoacana de San Nicolás de Hidalgo, Institute of Chemical Biology Research, Mexico In humans, the regenerative capacity of tissues is limited; consequently, there are bone structural damages for which it is appropriate to devise therapeutics that promote regeneration. The materials used currently as bone grafts have the main purpose of replacing the bone to fulfill a support function and not for tissue regeneration. The most common are organic, polymeric and metallic implants, each with advantages and disadvantages; among the latter, the main thing is that most are not biocompatible and resorbable, generating an immune rejection response in the body[1]. Tissue engineering has the challenge of developing bone substitutes that, besides serving as a support, promote bone regeneration; for this, the material must promote cell adhesion, proliferation and differentiation, have a temporary function, and gradually be resorbed and replaced by newly formed bone tissue[2]. For this purpose, the use of polyurethane/nano-hydroxyapatite hybrids (PU/nHAp) was proposed in this project[3]-[5]. Objective: To determine in vitro the optimal composition of the PU/nHAp hybrid that presents the best cell differentiation and bone mineralization stimulus. Methodology: PU/nHAp hybrid with compositions of 5, 10, and 20 weight% nHAp were evaluated. A murine preosteoblast cell line, MC3T3-E1 subclone 4, was used as the cellular model. To evaluate cell viability, trypan blue and alamar blue assays were used. Scanning Electron Microscopy (SEM) was used to analyze the surface of biomaterial samples. Expression of osteogenic markers was evaluated by RT-PCR and gel electrophoresis in 1% agarose. Results: None of the PU/nHAp biomaterials are cytotoxic, and neither have inhibitory effects on cell growth. Cell viability and the degree of mineralization are directly linked to the percentage of nHAp in the biomaterial composition. SEM micrographs at 0, 7, 10 and 14 days show cell adhesion and proliferation on the surface of biomaterial with PU-20%nHAp. The data suggests that the PU/20%nHAp composite might stimulate the osteogenic process in a greater degree, compared to the other composites tested. In control cultures, MC3T3-E1 in osteogenic medium and without the presence of biomaterials, the obtained osteocalcin, osterix and type I collagen gene expression profiles agree with previous reports using these genes as osteogenic markers; in cell cultures contacting biomaterials, the osteoinductive capability and bioactivity of PU/nHAp biomaterials was evident, without the need for an external osteogenic stimulus. Conclusions: The working hypothesis is confirmed: Biomaterials compounds of polyurethane and nano-hydroxyapatite, with compositions 20 weight % or lower of hydroxyapatite, stimulate cell differentiation and mineralization of newly formed bone tissue. This work was supported by CONACYT for the project financing Number: 243236 “, CB-2014-02, I0017 Fund.

Extended culture of macrophages from different sources and maturation results in a common M2 phenotype

Inflammatory responses to biomaterials heavily influence the environment surrounding implanted devices, often producing foreign-body reactions. The macrophage is a key immunomodulatory cell type consistently associated with implanted biomaterials and routinely used in short-term in vitro cell studies of biomaterials aiming to reproduce host responses. Inconsistencies within these studies, including differently sourced cells, different durations of culture, and assessment of different activation markers, lead to many conflicting results in vitro that confound consistency and conclusions. We hypothesize that different experimentally popular monocyte-macrophage cell types have intrinsic in vitro culture-specific differences that yield conflicting results. Recent studies demonstrate changes in cultured macrophage cytokine expression over time, leading to the hypothesis that changes in macrophage phenotype also occur in response to extended culture. Here, macrophage cells of different transformed and primary-derived origins were cultured for 21 days on model polymer biomaterials. Cell type-based differences in morphology and cytokine/chemokine expression as well as changes in cell surface biomarkers associated with differentiation stage, activation state, and adhesion were compared. Results reflect consistent macrophage development toward an M2 phenotype via up-regulation of the macrophage mannose receptor for all cell types following 21-day extended culture. Significantly, implanted biomaterials experiencing the foreign-body response and encapsulation in vivo often elicit a shift toward an analogous M2 macrophage phenotype. In vitro "default" of macrophage cultures, regardless of lineage, to this M2 state in the presence of biomaterials at long culture periods is not recognized, but has important implications to in vitro modeling of in vivo host response.

Ocular infections caused by non‐tuberculous mycobacteria: update on epidemiology and management

To provide an update on the frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria. Retrospective study of university clinic patients. One hundred thirty-nine patients with culture confirmed non-tuberculous mycobacteria infections seen at Bascom Palmer Eye Institute from January 1980 to July 2007. Chart review of data collected included patients' demographics, risk factors, microbiological profiles and clinical outcomes. Frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria. A total of 183 non-tuberculous mycobacteria isolates from 142 eyes were identified, with a fourfold increase in the number of eyes infected with non-tuberculous mycobacteria from 1980-1989 (13.4%) to 2000-2007 (56.3%). Eighty-three percent of non-tuberculous mycobacteria isolates were identified as M. abscessus/chelonae. The majority (91%) of isolates were recovered within 10 days. Common diagnoses included keratitis (36.6%), scleral buckle infections (14.8%) and socket/implant infections (14.8%). Identifiable risk factors were presence of biomaterials (63.1%), ocular surgery (24.1%) and steroid exposure (77%). The median time from diagnosis of culture positive non-tuberculous mycobacteria infection to resolution was 13 to 24 weeks. Combination therapy was used to treat 80% of infected eyes. In vitro susceptibility of non-tuberculous mycobacteria isolates were: amikacin, 81%; clarithromycin, 93%; and moxifloxacin, 21%. The incidence of ocular infections caused by non-tuberculous mycobacteria has increased within the last 8 years, with a high number of biomaterial associated infections among this group. Clinical diagnosis and microbiological confirmation of non-tuberculous mycobacteria infections remains challenging. Patient outcomes may be improved by early diagnosis, appropriate therapy and removal of biomaterials.

Cells Behaviour in Presence of Nano-Scaffolds

Nanomaterials are being made for use in various fields in biology from sensors to clutches. Nanomaterials may be perceived, in bizarre ways by the cells. Starting from the membrane to the nucleus, each component of the cell could have a new response. Mesenchymal Stem Cells (MSC) isolated from human placenta, Wharton's jelly, cord blood, fetal bone marrow and adipose tissue, cultured in the presence of biomaterials were monitored for differentiation in to the osteogenic phenotype. On the basis of osteogenic marker expression analysis, placental cells exhibited the best osteogenic potential among the different MSC. There is some cell death initially but the cells that remain viable show uptake of nanoparticles. The viable cells both divide and show differentiation into osteogenic cell type. The placental MSC in conjunction with the biomaterials were implanted in the injured femur of Wistar rats showed complete regeneration of the damaged region.

Extended interaction of β1 integrin subunit-deficient cells (GD25) with surfaces modified with fibronectin-derived peptides: Culture optimization, adhesion and cytokine panel studies

The modification of biomaterials with extracellular matrix-mimicking factors is a common technique used to influence the cellular response through integrin-mediated signaling. The inherent limitations of antibody-inhibition studies necessitate the use of complementary methods to block integrin function to confirm cell–surface interaction. In this study, we employed a β1 integrin-deficient cell line, GD25, to investigate the role of β1 subunit in cell adhesion and subsequent cytokine (granulocyte macrophage colony stimulating factor; interleukin (IL)-1α; IL-1β; IL-6; monocyte chemoattractant protein-1; regulated upon activation, normal T-cell expressed, and secreted; tumor necrosis factor-α) release kinetics in the presence of tissue culture polystyrene (TCPS) and semi-interpenetrating polymer networks (sIPN) modified with fibronectin (FN)-mimic peptides (RGD, PHSRN). Culture conditions (i.e. seeding density, medium, serum supplementation) were optimized for long-term observation. Differences in cell adhesion, cell viability and cytokine release behavior were dependent on the presence of the β1 integrin subunit, FN, sIPN cast method and peptide identity. By comparing two complementary techniques for assaying integrin function, we observed both similarities (i.e. decreased adhesion to FN-absorbed TCPS and increased IL-1β release at 96 h) and differences (i.e. no difference in adhesion or IL-1β release in the presence of different sIPN surfaces) when the function of the β1 subunit was blocked in cell adhesion and signaling in the presence of biomaterials.

Biological glass coating on ceramic materials:: in vitro evaluation using primary osteoblast cultures from healthy and osteopenic rat bone

ZrO 2 and Al 2O 3 substrates were successfully coated by a double layer of a silica-based glass named RKKP, using a low-cost firing technique. RKKP is a glass well known for its bioactivity; therefore, a RKKP coating on Al 2O 3 or ZrO 2, allows to combine the excellent mechanical properties of these strong ceramic substrates with its bioactivity. ZrO 2 samples were easily coated using a double layer of RKKP by a simple enamelling technique. To accommodate the thermal expansion coefficient mismatch between Al 2O 3 and RKKP, this substrate was coated using a multilayered composite approach. All of the coatings were characterised from a morphological and compositional point of view, and an extensive biological evaluation was performed using fresh rat osteoblasts. Osteoblast primary cultures were derived from the trabecular bone of femoral condyles harvested from intact (NB) and osteopenic (OB) rats. After characterisation of their phenotype, osteoblasts were seeded on material samples of ZrO 2 or Al 2O 3 coated with RKKP, and cultured for 7 days. Cell proliferation (MTT test) and cell differentiation (alkaline phosphatase activity) were evaluated at the end of the experiment, to assess osteoblast behaviour in the presence of biomaterials and determine if the results were related to the host bone quality. Results of both materials showed a good level of biocompatibility. In particular, MTT significant higher values were detected in NB cultures on ZrO 2–RKKP samples; ALP activity significantly increased in NB cultures on Al 2O 3–RKKP and in OB cultures on both coated samples.

Selected aspects of the microencapsulation of mammalian cells in HEMA-MMA.

Microencapsulation of live mammalian cells is one means of creating hybrid artificial organs, like an artificial pancreas or an artificial liver. In addition to creating and developing the methodologies for enclosing cells within the appropriate semipermeable and biocompatible membranes, novel techniques are needed to assess the various features of the resulting capsules. The small size of a capsule or its heterogeneity can lead to additional complexities that go beyond the problem of examining cell behavior in the presence of biomaterials. These problems are illustrated here by comparison of protein release by microencapsulated HepG2 cells within large and small HEMA-MMA (hydroxyethyl methacrylate-methyl methacrylate) capsules, by assessment of the effect of processing conditions on HEMA-MMA microcapsule permeability to horseradish peroxidase at the individual capsule level, and by a confocal microscopy technique for assessing intracapsule cell viability.

Biomaterial-neutrophil interactions: dysregulation of oxidative functions of fresh neutrophils induced by prior neutrophil-biomaterial interaction.

Biomaterial-associated infection results in increased morbidity and mortality, and may occur because of nonproductive premature activation of neutrophils resulting in impaired phagocyte function at the biomaterial surface in the event of bacterial challenge. To further explore the effects of this premature activation, we evaluated the supernatants of biomaterial associated neutrophils to determine whether soluble mediators were released, and the likely role of these mediators. We show that these supernatants contain a chemoattractant and thereby induce chemotaxis by fresh neutrophils. No evidence of enhanced oxidative free radical production by either unstimulated neutrophils or a primed response to other mediators occurs when neutrophils were incubated with these supernatants. We also examined the effect of adding fresh neutrophils to a biomaterial surface containing a previous inoculum of neutrophils, and observed that the fresh cells did not become stimulated to release reactive oxygen intermediates (ROI) and also exhibited impaired killing of staphylococci. These studies suggest that not only does the biomaterial surface activate the initial wave of neutrophils but that subsequent waves of neutrophils exhibit an impaired host-defense function. These results are consistent with the known impairment of host defense in the presence of biomaterials, and provide evidence for a long-term down-regulation of neutrophil function at biomaterial surfaces.

Biomaterial-induced macrophage activation and monokine release.

This study quantifies macrophage acid phosphatase release as a marker of cell activation when cultured with or without biomaterials. Peritoneal macrophages were harvested from six New Zealand White rabbits and cultured in minimum essential media with 10% equine serum. After cell identification by morphology, nonspecific esterase, and RAM 11 immunoperoxidase, cells were passaged twice, and second-passage macrophages were seeded in 96-well plates (5,000 cells/well) and grown to confluence. After collection of day zero media, circular disks of polyglactin 910 and two types of commercially available polyethylene terephthalate with different construction and sterilization characteristics were placed on the cell monolayer. Controls without biomaterials were also established. Media was collected and pooled for each group and time point beginning on day 2 and continuing every other day for 22 days. Conditioned media were quantitatively assayed for acid phosphatase colorimetrically at 402 nm using p-nitrophenylphosphate as the substrate. Acid phosphatase activity increased progressively at late time points for each group but no difference was noted between groups at any time point. These data show that the activation of cultured macrophages with time is not altered differentially by the presence of biomaterials. The previously demonstrated monokine release following biomaterial exposure is therefore a specific event and not simply part of the generalized activation phenomenon.

Neurons behaviour in presence of biomaterials

Neurons behaviour in presence of biomaterials

Bacterial Adherence and the Glycocalyx and Their Role in Musculoskeletal Infection

Bacteria produce a virulence-related polysaccharide exocellular slime (the glycocalyx), which preferentially adheres to the surfaces of biomaterials and compromised tissues. This biofilm resists antibiotic penetration and provides a degree of protection from antibodies and macrophages. Similar adhesive cell-to-substrate phenomena have been noted in natural environments and in bacterial-animal cell disease states. The adherent glycocalyx is one of the fundamental reasons for increased susceptibility to infection in the presence of biomaterials and compromised tissues and a significant factor in the persistence of such infection until the removal of the prosthetic device.

The mechnical behaviors on nonthrombogenecity

Synthetic polymers suitable for use in the cardiovascular system are needed as biomaterials for heart valve prostheses, artificial heart, veins, arteries and extracorporeal circulatory devices as heart-lung and kidney machines. Despite the wide variety of synthetic polymers that are available in the form of plastics or elastomers, none has proven eligible to clinical application for this purpose as a perfectly nonthrombogenic material. Currently, most investigations seem to be directed toward clarification of the blood biomaterial surface interaction, especially the mechanism whereby thrombi are formed in contact with such prosthetic. In many of these studies the surface properties of synthetic materials are being investigated from the angle where the foreign surface: blood interaction is taken as interface reaction, with the attention focused upon hydrophobicity, hydrophilicity and electronegativity of the materials. Findings obtained in our studies aimed at development of antithrombogenic materials have indicated importance of a definite distribution density of hydrophobicity and hydrophilicity for such polymers; namely, it appears unlikely that no surface factor is involved in the biomaterial: blood interface.Supposing, for example, that a synthetic venous prosthesis with a surface of about 15cm2 be introduced into the vascular system, this newly added surface of about 15cm2 undoubtedly would be so slight as to fall within the limits of errors as compared with the entire inner surface of the cardiovascular system and hence as viewed in terms of the concentration of heparin injected for inhibition of the clotting system. Thus it would be rational to introduce into the study the findings on the surface structure of cells exposed to the cardiovacular lumen. Our studies are based on this ground, pursued through physico-chemical analysis of the interface comprised of the prosthetic surface and the circulating plasma surface. By comparative evaluation of various synthetic polymer prostheses in terms of antithrombogencity, the interfacial condition of the vascular inner surface of the organism was determind to consist of γC(Zis.)=20 to 30erg/cm2, γC=68.5erg/cm2 and γSL(H2O)=0erg/cm2, or the surface endowed both with hydrophilicity and it was demonstrated that a synthetic polymer fulfilling the prerequisites of γC(Zis.)=29 to 30erg/cm2, γC=29 to 30erg/cm2 and γSL(H2O)=0erg/cm2 is remarkably antithrombogenic. The results, stress prime importance of the function of interface to protein at a synthetic polymer surface and indicate the presence of biomate rials with minimal bearing upon the clotting system of blood. Further studies aimed at clarification of the interaction with protein will be pursued, using such materials.