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PubMed2007

A preliminary report on a novel electrospray technique for nanoparticle based biomedical implants coating: precision electrospraying.

The compatibility and biological efficacy of biomedical implants can be enhanced by coating their surface with appropriate agents. For predictable functioning of implants in situ, it is often desirable to obtain an extremely uniform coating thickness without effects on component dimensions or functions. Conventional coating techniques require rigorous processing conditions and often have limited adhesion and composition properties. In the present study, the authors report a novel precision electrospraying technique that allows both degradable and nondegradable coatings to be placed. Thin metallic slabs, springs, and biodegradable sintered microsphere scaffolds were coated with poly(lactide-co-glycolide) (PLAGA) using this technique. The effects of process parameters such as coating material concentration and applied voltage were studied using PLAGA and poly(ethylene glycol) coatings. Morphologies of coated surfaces were qualitatively characterized by scanning electron microscopy. Qualitative observations suggested that the coatings were composed of particles of various size/shape and agglomerates with different porous architectures. PLAGA coatings of uniform thickness were observed on all surfaces. Spherical nanoparticle poly(ethylene glycol) coatings (462-930 nm) were observed at all concentrations studied. This study found that the precision electrospraying technique is elegant, rapid, and reproducible with precise control over coating thickness (mum to mm) and is a useful alternative method for surface modification of biomedical implants.

Coated Materials, Biocompatible↗

PubMed2007

Fibroblast cell attachment and growth on nanoengineered sculptured thin films.

Nanoengineered parylene-C sculptured thin films (STFs) are deposited on glass and silicon substrates using a direct one-step growth technique. The deposited STFs support fibroblast cell attachment and proliferation in vitro, which is an early indication of biocompatibility and bioactivity of this emerging class of biomaterials. Surface modification of endoprostheses of the small joints of the hand, which heal with fibrous stabilization, may be greatly enhanced by such nanoengineered biomaterials.

Animals↗

PubMed2004

Application of scanning probe microscopy to the characterization and fabrication of hybrid nanomaterials.

Scanning probe microscopy (SPM) is a widely used experimental technique for characterizing and fabricating nanostructures on surfaces. In particular, due to its ability to spatially map variations in materials properties with nanometer spatial resolution, SPM is particularly well suited to probe the subcomponents and interfaces of hybrid nanomaterials, i.e., materials that are made up of distinct nanometer scale components with distinguishable properties. In addition, the interaction of the SPM tip with materials can be intentionally tuned such that local surface modification is achieved. In this manner, hybrid nanostructures can also be fabricated on solid substrates using SPM. This report reviews recent developments in the characterization and fabrication of hybrid nanomaterials with SPM. Specific attention is given to nanomaterials that consist of both organic and inorganic components including individual biomolecules mounted on inorganic substrates. SPM techniques that are particularly well suited for characterizing the mechanical and electrical properties of such hybrid systems in atmospheric pressure environments are highlighted, and specific illustrative examples are provided. This review concludes with a brief discussion of the remaining challenges and promising future prospects for this field.

Animals↗

PubMed1976

Cytological observations of the ovarian epithelium in mammals during the reproductive cycle.

We have studied the ovarian epithelijm at various stages of the reproductive cycle in a number of mammalian species utilizing light microscopy, scanning microscopy, the freeze-fracture technique, transmission microscopy and by employing specialized tracers that use lanthanum and horseradish peroxidase. We found that the epithelial cells are joined by incomplete tight junctions, gap junctions, and desmosomes. The cytoplasmic matrix contains a large irregularly shaped nucleus, few microtubules, microfilaments, mitochondria, endoplasmic reticulum and a host of coated and non-coated vesicles of varying diameters. The saccules comprising the large Golgi complex and its companion vesicles are associated with a basal body-centriole complex: some of these saccules and affiliated vesicles are acid phosphatase positive. Surface modifications of ovarian epithelial cells include numerous microvilli, some of which have a bulbous tip, and plications of the lateral plasma membrane which are thought to accomodate volume changes of the ovary during follicular development. Many coated and non-coated endocytotic caveolae were found on these cells, particularly in the basal area. These caveolae internalized exogeneously administered horseradish peroxidase. We view the marked endocytotic activity as an efficient transport mechanism for partially removing substances from the interstitium of the ovary and the peritoneum.

Animals↗

PubMedDate not supplied

Patterns of lingual tissue deformation associated with bolus containment and propulsion during deglutition as determined by echo-planar MRI.

Disordered lingual function is a common clinical attribute of patients with oropharyngeal dysphagia. To determine physiologic patterns of lingual tissue motion during swallowing, we imaged the actively deforming tongue during water bolus swallows with sequential single-slice sagittal orientation echo-planar imaging. At rest, with the bolus contained in the oral cavity before swallow initiation, the tongue displayed a characteristic curved configuration consisting of a convex surface (anterior to the bolus) in continuity with a concave surface (containing the bolus) and a posterior-located convex surface (comprising the tongue base). With swallow initiation, the previously deformed tongue underwent rapid biphasic displacement: (a) superior displacement of the anterior tongue and deepening of the midposterior-located bolus-containing concavity, resulting in a laterally beveled surface encompassing the bolus; and (b) retrograde displacement of the configured tissue, resulting in clearance of the bolus from the oral cavity to the oropharynx. These findings indicate that deglutitive tongue action can be depicted by echo-planar imaging as a series of deformative surface modifications, which are related to the activity of intrinsic and extrinsic lingual muscles.

Adult↗

PubMed2004

Mechanistic study of the uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells.

The purpose of this study was to evaluate the extent and mechanism of uptake of wheat germ agglutinin-conjugated PLGA nanoparticles by A549 cells. PLGA nanoparticles of 150 nm were prepared by a solvent diffusion method and covalently conjugated to FITC-WGA (fWGA) or FITC-bovine serum albumin (fBSA) by a two-step carbodiimide method. Uptake of fWGA-PLGA and fBSA-PLGA nanoparticles by confluent A549 cells was quantified by fluorometry. A549 cellular uptake of fWGA-PLGA nanoparticles at 2 h, 37 degrees C was 5.02-fold that of fBSA-PLGA nanoparticles at a loading concentration of 2.65 mg/mL. The difference in uptake between the two types of nanoparticles was increased to 7.84-fold at a higher loading concentration of 5.3 mg/mL, but was reduced to 2.07-fold by lowering the uptake temperature to 4 degrees C. Coincubation with 5 mg/mL of unlabeled WGA negated the differential uptake of fWGA-PLGA nanoparticles at 4 degrees C, suggesting that the nanoparticles interacted with a specific WGA-binding receptor on the cell membrane. Internalization of the fWGA-PLGA nanoparticles by the A549 cells was confirmed by confocal microscopy. Filipin (1 microg/mL), a known inhibitor of caveolae, reduced the 1-h uptake of the nanoparticles by 75%. Surface modification of PLGA nanoparticles with WGA significantly enhanced its endocytosis by A549 cells by a receptor-mediated, caveola-dependent pathway.

Biomechanical Phenomena↗

PubMed2004

Biodegradable polyesters reinforced with surface-modified vegetable fibers.

Flax fibers are investigated as reinforcing agents for biodegradable polyesters (Bionolle and poly(lactic acid) plasticized with 15 wt.-% of acetyltributyl citrate, p-PLLA). The composites are obtained either by high temperature compression molding fiber mats sandwiched between polymer films, or by batch mixing fibers with the molten polymer. Fibers in composites obtained by the latter method are much shorter (140-200 microm) than those of the mats (5,000 microm). Flax fibers are found to reinforce both p-PLLA and Bionolle (i.e. tensile modulus and strength increase) when composites based on fiber mats are investigated. Conversely, analogous composites obtained by batch mixing show poor mechanical properties. The observed behavior is attributed to the combined effect of fiber length and fiber-matrix adhesion. If flax fibers with a modified surface chemistry are used, the strength of short fiber composites is seen to improve significantly because the interface strengthens and load is more efficiently transferred. Appropriate surface modifications are performed by heterogeneous acylation reactions or by grafting poly(ethylene glycol) chains (PEG, molecular weight 350 and 750). The highest tensile strength of p-PLLA composites is reached when PEG-grafted flax fibers are used, whereas in the case of Bionolle the best performance is observed with acylated fibers.

Adipates↗

PubMed2000

Zooarchaeological and taphonomic analysis of the Die Kelders Cave 1 layers 10 and 11 Middle Stone Age larger mammal fauna.

Middle Stone Age (MSA) and Middle Paleolithic (MP) faunal assemblages have gained widespread attention due to their relevance to the debate over the modernity of hominid behavior during the MSA/MP. A recent critique of the scavenging argument for MSA/MP behavior drew on a summary presentation of the skeletal abundance and surface modification data from Die Kelders Cave 1 Layer 10 (Marean, 1998). This paper provides a more complete presentation of those data, adds the smaller Layer 11 sample, and provides a detailed analysis of the taphonomic history of both samples.Bone fragment density is higher in Layer 10 than in Layer 11. Bone densities vary horizontally as well, with Layer 10 showing greater deposition in the exposed areas of the cave. An analysis of long bone breakage patterns indicates that non-nutritive breakage on the Layers 10 and 11 samples was present but not intense. Size 1 mammals were predominantly accumulated by owls and/or other large raptors, not hominids, in Layer 10. Hominids were the predominant accumulator of Sizes 2-4 mammals in Layers 10 and 11 as indicated by the frequency of hammer-stone percussion marks and carnivore toothmarks. After discard by hominids, a significant portion of these remains were discovered and scavenged by carnivores. Overall, the larger mammal fauna of Layer 10 is dominated by Sizes 3 and 4 bovids, mostly young and adult eland, and thus hominids were focusing on the high-ranked prey items. Shaft portions of long bones, the portions with the most flesh, have the highest frequencies of cutmarks. A comparison of the Layers 10 and 11 cutmark frequencies to Selvaggio's (1998) scavenging model shows that the frequencies are significantly outside the range of variation documented in Selavaggio's scavenging sample.

Animals↗

PubMed1998

Altered response of oyster hemocytes to Haplosporidium nelsoni (MSX) plasmodia treated with enzymes or metabolic inhibitors.

To avoid phagocytosis, parasites may mask themselves with host-like molecules that prevent recognition as nonself or they may produce substances that interfere with host cellular defenses. The protozoan parasite Haplosporidium nelsoni, which causes MSX disease in the eastern oyster Crassostrea virginica, is not ingested by host hemocytes. To assess potential avoidance mechanisms, oyster hemocytes were incubated with plasmodial stages of the parasite that had been pretreated with one of a variety of enzymes (proteases and carbohydrases) to alter surface molecules or with metabolic inhibitors to prevent the synthesis or active uptake of "masking" molecules, as well as the production and discharge of inhibitory substances. The maximum increase in phagocytosis resulting from treatment with carbohydrases was 12.5% (beta-galactosidase) and with proteases was 18% (Proteinase K). Inhibitors of aerobic metabolism resulted in a similar level of enhancement. In contrast, treatment of parasites with the glycolysis inhibitor iodoacetate enhanced phagocytosis by up to 66%. Thus, the process that obstructs phagocytosis involves aerobic and, especially, anaerobic pathways. The greater effect of a metabolic inhibitor compared to enzymes suggests that the mechanism involves more than just surface modification and may include the production of interference molecules.

Animals↗

PubMed1993

Adhesion and motility of polymorphonuclear leukocytes isolated from the blood of rats exposed to ozone: potential biomarkers of toxicity.

Ozone (O3) exposure of rats results in airway epithelial injury and an infiltration of polymorphonuclear leukocytes (PMNs) into the lungs, suggesting alteration of PMN functions. To identify the altered PMN functions and their possible effects on epithelia, rats were exposed to air or 0.8 ppm O3 for 2 hr. PMNs were isolated from the blood and incubated with an epithelial cell line derived from rat lung (ARL-14) or primary alveolar type II cell cultures. The PMNs from the O3-exposed rats exhibited stimulated motility and spontaneous redistribution of actin filaments and adhered in a greater number to the epithelial cells when compared with the PMNs from the air-exposed rats. Actin caps usually formed at the sites of contact between the PMNs and epithelial cells, suggesting a cytoskeletal role in the inflammatory-epithelial cell interaction. By scanning electron microscopy, PMNs from air-exposed rats had features of non-motile cells. In a striking contrast to this, PMNs from O3-exposed rats revealed surface modifications, which were quite prominent at the sites of PMN-epithelial cell contacts. Despite these morphological changes, the PMNs from O3-exposed rats did not alter the epithelial resistance, a measure of paracellular permeability. In contrast to this, PMNs stimulated by phorbol myristate acetate or N-formyl-methionyl-leucyl-phenylalanine not only exhibited greater adhesion to the epithelial cells, but also caused a reduction in epithelial resistance. The changes reflecting altered morphology, motility, and adhesion of PMNs from O3-exposed rats may represent important steps in the O3-induced inflammatory response that precedes barrier disruption in vivo, but they are not associated with increased epithelial permeability in an in vitro system. Besides their mechanistic relevance, the alterations of vascular PMNs may serve as important biomarkers for detecting O3 effects.

Animals↗

PubMed1985

Fine structure of the epithelia of the vomeronasal organ of horse and cattle. A comparative study.

The vomeronasal organ of both horses and cattle is a tubular structure situated bilaterally at the base of the nasal septum. In frontal plane the shape of its lumen is semilunar to crescent. The sensory epithelium lining the medial wall of the lumen contains receptor, supporting and basal cells with some surface modifications in both species. In the horse, a structure similar to a microprocess was observed among the microvilli of receptor cells. In cattle, a large mass of the cytoplasm of the receptor cell occasionally protrudes to form a bleb-like structure. The supranuclear cytoplasm of the receptor cells contain mitochondria, free ribosomes, rough endoplasmic reticula, Golgi apparatus, lysosomes and multivesicular bodies. Some receptor cells were pyknotic. In both species the respiratory epithelia of the lateral wall of the lumen contain ciliated, non-ciliated and basal cells. In the horse, this epithelium differs from that of other species in evidence of prominent secretory function.

Animals↗

PubMed1982

Studies on the development of extra-endothelial and intra-endothelial pigment deposits by means of direct and indirect contact specular microscopy of the cornea.

Retro-corneal pigmentation as a result of primary (degenerative) or secondary (inflammatory, traumatic) pigment dispersion represents one of the most frequent findings in specular microscopy. The analysis of the pigment distribution patterns of dense deposits like those in Krukenberg spindle (KS) permits the postulation of a hypothesis concerning the development of such typical corneal pigmentations and the pigmentation of the posterior surface of the cornea in general, such as diffuse pigment dispersion (Vogt 1930), which is seen frequently. In a particular case of double KS with extreme myopia and cataract, endothelial morphological findings were documented over a period of 1 year, both before and after cataract extraction. This was done by means of contact and non-contact specular microscopy in various spindle areas. The morpho-metric studies (cell density/mm2; cell perimeter; largest smallest and average cell diameter; specific surface; horizontal and vertical cell orientation) were carried out automatically using a computerised video image analyser. The changes in the area of densest pigmentation in the KS centre confirm the histologically proven capacity of pigment phagocytosis by human corneal endothelium. These findings indicate that in specular microscopy, both endothelial cellular surface modifications and intra-cellular changes are documentable. The extracellular pigment deposits can also be shown by means of 'indirect' specular microscopy, the optical principle of which is described.

Aged↗

PubMed1990

Enzyme activities of lung lavage in silicosis.

The cytotoxic effect of quartz on lung cells has been well documented by in vitro and animal studies, but the pertinence of these findings to humans has not yet been documented. We measured lactate dehydrogenase (LDH) activities in the lung lavage of 24 long-term workers in the Québec granite industry and 25 control subjects. We found significant increases in LDH activities in the workers' lung lavage, even in the absence of established silicosis (9 subjects). We looked at a similar observation in the sheep model of early silicosis, measured quartz content of lung lavage, and found significant correlation with LDH levels (R = 0.64, p less than 0.001). All of the quartz particles in human and sheep lung lavage were in the alveolar macrophages. To test further the relationship of macrophage damage (cytotoxicity of quartz) we measured the release of LDH by sheep alveolar macrophage in 24 h cell culture under control conditions, exposure to inert dust, titanium, minusil-5 quartz, or aluminum-treated quartz. The LDH release was at control levels during titanium exposure and showed a significantly dose-related increase during quartz exposure. The latter cytotoxic effect was largely attenuated by aluminum treatment of quartz. These in vitro data agreed with previous reports. This study presents evidence of a cytotoxic effect of quartz inhalation in humans. The effect is related to the intensity of quartz retention in the lung macrophages; it is not a nonspecific dust exposure effect and can be attenuated by surface modification of the quartz.

Adult↗

PubMed2005

Study on the therapeutic mechanism of the active principle of the Chinese drug Paeoniae Radix 801 through affinity biosensors IAsys plus quartz crystal microbalance.

OBJECTIVE: To study the targeted point and mechanism of the function of the blood-activating and stasis-removing Chinese drugs, Paeoniae Radix 801(PR801) in its cardiovascular protective effects and its specific binding with endothelin 1 (ET-1) as well as the dynamics of the two's interactive function by means of using affinity biosensors: IAsys Plus and quartz crystal microbalance (IAQCM). METHODS: ET-1 was immobilized on the surfaces of IAQCM by using the new surface modification methods. The PR801 in the solution was detected by modified substrates and the specific binding between PR801 and ET-1 was studied. RESULTS: The curves went up or down after adding PR801. There is specific binding between PR801 and ET-1. The bound mass were 0.458 ng/mm(2) and 133.54 ng/cm(2), respectively. There exists relatively good stability with these two methods. CONCLUSION: The affinity biosensors: IAQCM can be used to study the interaction mechanism between PR801 and ET-1, providing a new way to study the interaction mechanism of TCM. PR801 can bind ET-1 specifically in the experiments. Therefore, ET-1 is another target that PR801 can bind specifically besides thromboxane A(2).

Biosensing Techniques↗

PubMed2004

[Extracorporeal membrane oxygenation by acute respiratory distress syndrome].

After various observational studies demonstrated a benefit of extracorporeal membrane oxygenation (ECMO) in the therapy of severe acute respiratory distress syndrome (ARDS), ECMO now represents an important contribution for ARDS therapy using clinical algorithms despite a lack of positive controlled studies. In specialized centers patients with severe ARDS and imminent hypoxia despite intensive conventional therapy, are treated with ECMO using blood pumps and artificial membrane lungs (oxygenators) for extracorporeal lung assist. The development of new surface modifications, optimized oxygenators and miniaturized blood pumps should increase hemocompatibility and lead to simplified treatment as well as less complications. New oxygenators with significantly decreased blood resistance allow the clinical application of pumpless arteriovenous extracorporeal lung assist (ECLA). After these new developments indications for ECMO could be extended from use not only as ultimate ratio but to less severe ARDS to enable lung protective, less invasive mechanical ventilation.

Anticoagulants↗

PubMed2000

[In vitro analysis and animal experiment study of surface modified biodegradable polylactide ureteral stents].

With the objective of developing a biodegradable ureteric stent, various polylactides were analyzed and grafted with a clinically adapted surface. Stent moulding was performed by CESP technology (Controlled Expansion of Saturated Polymers), which is not based on high temperature but gas-loading under high pressure which induces a foamy bulk structure. The hydrolytically biodegradable, synthetic homo- and copolymers poly(D,L-lactide) (PDLLA), poly(D,L-lactide-co-trimethylene-carbonate) (PDLLA-co-TMC), poly(D,L-lactide-co-glycolide) (PDLLA-co-Gly) as derivatives of lactic acid or glycolic acid and surface modifications with hydroxyethylene-methacrylate (HEMA) and oligoethyleneoxidemonomethacrylate (OEOMA) were analyzed with regard to cytotoxicity and cell adhesion. Methacrylates have minimized protein and cell adhesion and degradation of non-toxic products. All polymers exhibited a high degree of biocompatibility and cell adhesion was markedly reduced following HEMA grafting. A 3 cm and 7 Charrière prototype of the stent was moulded from PDLLA-co-TMC by CESP-technology, and grafted with HEMA by means of plasma-induced polymerization. Finally, the stents were implanted into female sheep, following unilateral ureterotomy. Regular blood and urine analysis as well as ultrasound and the final autopsy revealed no pathological findings. Histopathological analysis exhibited a regular epithelium without any changes being determined by contact to the stent, and a good regeneration of all layers in the area of anastomosis.

Anastomosis, Surgical↗

PubMed2002

[Keratoprostheses. Historical overview, materials and status of current research].

The idea to substitute optically clear material in an opaque cornea is two centuries old and in that time experiments have been carried out in animals and patients without much success. The historical development of and the clinical experiences with keratoprostheses are described. Especially in the last 40 years there have been great efforts concerning design, fixation, material and surgical technique to create a device with long-term success. The best long-term survival rates are achieved with the osteo-odontokeratoprosthesis, as it is the only model with a biological haptic. Due to some disadvantages of this procedure the present research is looking for new, soft materials and surface modifications to create a biointegrable artificial cornea.

Animals↗

PubMed2006

The efficacy of acrylic acid grafting and arginine-glycine-aspartic acid peptide immobilization on fibrovascular ingrowth into porous polyethylene implants in rabbits.

PURPOSE: To determine the effects of acrylic acid (AA) grafting by argon plasma treatment and of immobilization of arginine-glycine-aspartic acid (RGD) peptides on fibrovascular ingrowth rate into high-density porous polyethylene (HPPE) anophthalmic orbital implants. MATERIALS AND METHODS: Sixty rabbits were divided into three groups, with 20 rabbits in each group: (1) control group, rabbits implanted with unmodified HPPE; (2) PAA group, rabbits implanted with HPPE grafted with poly(AA) by argon plasma treatment; (3) RGD group, rabbits implanted with HPPE grafted with AA by argon plasma treatment and subsequently immobilized with RGD peptide. An HPPE spherical implant was put in the abdominal muscles of rabbit. After implantation for 4 weeks, the retrieved implants were sectioned and stained with hematoxylin and eosin (H&E). Blood vessels were counted using CD-31 immunostaining. Cross-sectional areas of fibrovascular ingrowth, blood vessel densities, and host inflammatory response scores were determined for all three groups. RESULTS: The mean cross-sectional areas of fibrovascularization at 2 and 3 weeks after implantation were the greatest in the RGD group, followed by the PAA group. While minimal fibrovascular ingrowths were noted in all implants at 1 week, all the implants showed nearly complete ingrowth at 4 weeks. Blood vessel densities were the highest in the RGD group, followed by the PAA group at 2, 3, and 4 weeks. The mean inflammation scores of the PAA and RGD groups were less than that of the control group. CONCLUSION: Fibrovascularization into HPPE implants was enhanced by surface grafting of AA and further improved by immobilizing RGD peptides onto the grafted AA surfaces. The inflammatory reactions were mild by either technique of surface modification.

Abdominal Muscles↗