|Articles about Biomaterials|
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| Use of sterile adhesive film and polypropylene mesh in the construction of a temporary silo in the treatment of omphalocele
Ozbey, H. (2005), Surg Today 35(8): 700-2.
Abstract: When a primary closure is not feasible, a synthetic material must be used in patients with congenital abdominal wall defects. Sterile adhesive film (drape) is reinforced with polypropylene mesh, and then it is used as a prosthesis for constructing a temporary silo. The drape surface is applied to the herniated viscera, which provides a smooth surface that does not adhere to the bowel loops. The adhesive film (drape) is a sterile, impermeable, transparent, and flexible material, which is readily available in all operating rooms. When combined with polypropylene mesh, an effective prosthesis can be created for the staged surgical treatment of congenital abdominal defects such as omphalocele and gastroschisis.
| Use of vascular explants for ex vivo neovascularization of biomaterials
Iurlaro, M., J. E. Sanders, et al. (2002), Microvasc Res 64(3): 398-404.
Abstract: Biomaterial polymers have been proposed as scaffolds for cell assembly in vascular bioengineering. We describe here a new method for the neovascularization of polyurethane meshes from explants of rat aorta. Aortic rings embedded in collagen-permeated polyurethane meshes and cultured in medium supplemented with fetal bovine serum and vascular endothelial growth factor generated florid microvascular outgrowths that efficiently vascularized the available spaces between polyurethane fibers. The neovessels could be identified in the live cultures by phase-contrast microscopy, and in formalin-fixed preparations by the ABC peroxidase procedure, using the endothelial-specific Griffonia isolectin B4. The aortic outgrowths were successfully labeled with the intravital fluorescent dyes Calcein AM or SPDiOC(18), which are nontoxic and can be used for tracking studies. This study shows that artificial biomaterial meshes can be colonized ex vivo with histotypic microvascular networks, and provides the proof of concept for the future development of stably vascularized devices for in vivo implantation.
| Use of water to evaluate hydrophobicity of organically-modified xerogel enzyme supports
Clifford, J. S. and R. L. Legge (2005), Biotechnol Bioeng 92(2): 231-7.
Abstract: Silica xerogels are a new class of materials suitable for the immobilization of enzymes for various applications including biotransformations and biosensors. The physicochemical properties of xerogels, such as hydrophobicity, can be manipulated by the introduction of organically-modified silicates. This allows the immobilization matrix to be engineered to suit the enzyme and its application. Interfacial activation of lipase is a phenomenon in which the enzyme displays increased activity when it is bound to a hydrophobic interface. Lipase was entrapped in organically-modified xerogels in which the hydrophobicity of the enzyme support was modulated by the selection of different alkyltrimethoxysilane co-precursors and the ratio in which they were combined with tetramethyl orthosilicate. Interaction between the enzyme support and water was investigated with two methods to quantitatively assess the hydrophobicity of the entrapment matrix. The contact angle formed between the xerogel and water was used to determine hydrophobicity on a macroscopic level. Temperature-controlled water desorption was used to determine hydrophobicity on a microscopic level. Both methods were suitable for quantitatively discriminating between hydrophobic and hydrophilic materials. Further, the hydrophobicity of the enzyme support influenced the hydrolytic activity of the entrapped lipase under non-aqueous conditions. The specific activity of lipase increased only when entrapped in xerogels which could be classified as hydrophobic materials, that is with contact angles greater than 90 degrees or hydrophobicity values as determined by water desorption greater than 0.65.
| Using an adhesive retention tape on split skin graft donor areas
McPhee, H. (2005), Nurs Times 101(16): 57-8.
Abstract: Donor split skin graft areas are often painful, a problem that can be exacerbated when dressings that have been applied slip, particularly when they are on the patient's thigh. Helen McPhee carried out a small trial to assess whether Mefix, an adhesive retention tape, could help to reduce these problems
| Using computer-based systems for biomaterial evaluation
Hunt, J. A. (1999), Med Device Technol 10(7): 20-3.
Abstract: Computer-based image analysis techniques can be combined with immunohistochemistry to harness the full potential of computer technology. They can be used to quantitatively and reproducibly analyse cellular responses to materials and can play a significant role in medical device development and material selection. The benefits and pitfalls of the techniques are examined.
| Using electrical impedance detection to evaluate the viability of biomaterials subject to freezing or thermal injury
Yu, T. H., J. Liu, et al. (2004), Anal Bioanal Chem 378(7): 1793-800.
Abstract: This paper is aimed at comprehensively investigating the dynamic low-frequency electrical impedance (DLFI) of biological materials during the processes of freezing, thawing and heating, and combinations of them. Electrical impedance detection (EID) was proposed as a means of rapidly evaluating the viability of biological materials subject to freezing or thermal injury (processes expected to be significant in the practices of cryobiology and hyperthermia). Using two experimental setups, the DLFI for selected biological materials (fresh pork and fish) under various freezing and heating conditions was systematically measured and analyzed. Preliminary results demonstrate that damage that occurs to a biological material due to freezing or heating could result in a significant deviation in its electric impedance value from that of undamaged biomaterials. Monitoring impedance change ratios under various freezing and heating conditions may offer an alternative strategy for assessing the amount of damage sustained by biomaterials subject to cryosurgery, cryo-preservation and hyperthermia. Implementation of the present method in order to develop a new micro-analysis or biochip system is also suggested.
| Using silver to reduce catheter-associated urinary tract infections
Gentry, H. and S. Cope (2005), Nurs Stand 19(50): 51-4.
Abstract: Many thousands of urinary tract infections (UTIs) are linked to the insertion of an indwelling urethral catheter (Saint et al 2000). Catheterisation is often prolonged unnecessarily (Saint et al 2002), thereby increasing the infection risk. In this audit of 133 medical and surgical patients who were catheterised in an acute NHS hospital trust, the potential of a new silver alloy hydrogel-coated catheter to reduce the rate of infection was demonstrated. Benefits were indicated in terms of reducing clinical risk to the patient and the financial costs associated with treating catheter-associated UTIs, representing a substantial cost saving for the NHS.
| Using the chorions of fertilized zebrafish eggs as a biomaterial for the attachment and differentiation of mouse stem cells
Lee, J. W., D. S. Na, et al. (2005), Langmuir 21(17): 7615-20.
Abstract: The development of proper biomaterials is critical for the success of cell therapy and modern tissue engineering. Here, we extruded the yolk and remaining inner mass from fertilized zebrafish eggs and used the resulting chorions as a biomaterial for the differentiation and attachment of mouse P19 embryonic carcinoma (EC) cells. Cells inserted into the chorion showed the spontaneous formation of embryoid body due to the repulsive cell adhesion of the chorion and differentiated specifically into neural cells and cardiomyocytes. In contrast, dissolved chorion extracellular matrix (ECM) conferred enhanced cell attachment on it, suggesting that a unique property of the zebrafish chorion with nanoporous structure appears to be responsible for the simple and controllable embryoid formation for stem cell differentiation. These results indicate that chorions from fertilized zebrafish eggs may be used as an extracellular matrix alternative and applied for stem cell differentiation to specific cell lineages.
| Uterine compression suture without hysterotomy--why a non-absorbable suture should be avoided
Cotzias, C. and J. Girling (2005), J Obstet Gynaecol 25(2): 150-2.
Abstract: We describe 2 cases of uterine compression suture without hysterotomy, only described once in the literature previously (Hayman et al. 2002). We consider in detail the suture material used for this technique and show photos of the compression suture at laparoscopy 4 weeks after insertion to demonstrate why it is inappropriate to use a non-absorbable suture. Modified compression sutures are being used increasingly and a wide variety of suture materials are being chosen, including vicryl, PDS and nylon (verbal communications). We feel it important to report our findings so that others can avoid the use of non or slowly absorbable sutures.
| UV-induced graft copolymerization of monoacrylate-poly(ethylene glycol) onto poly(3-hydroxyoctanoate) to reduce protein adsorption and platelet adhesion
Kim, H. W., C. W. Chung, et al. (2005), Int J Biol Macromol 35(1-2): 47-53.
Abstract: Homogeneous solutions of poly(3-hydroxyoctanoate) (PHO) and the monoacrylate-poly(ethylene glycol) (PEGMA) monomer in chloroform were irradiated with UV light to obtain PEGMA-grafted PHO (PEGMA-g-PHO) copolymers. Variables affecting the degree of grafting (DG), such as the time of UV irradiation and the concentrations of the PEGMA monomer and initiator, were investigated. The PEGMA-g-PHO copolymers were characterized by measuring the water contact angle, molecular weight, thermal transition temperatures and mechanical properties, as well as by nuclear magnetic resonance spectroscopy. The results from all of these measurements indicate that PEGMA groups were present on the PHO polymer. The protein adsorption and platelet adhesion on the PEGMA-g-PHO surfaces were examined using poly(L-lactide) (PLLA) surfaces as the control. The proteins and platelets had a significantly lower tendency to adhere to the PEGMA-g-PHO copolymers than to PLLA. The graft copolymer with a high DG of PEGMA was very effective in reducing the protein adsorption and platelet adhesion and did not activate the platelets. The results obtained in this study suggest that PEGMA-g-PHO copolymers have the potential to be used as blood-contacting devices in a broad range of biomedical applications.
| UV-vis-infrared optical and AFM study of spin-cast chitosan films
Nosal, W. H., D. W. Thompson, et al. (2005), Colloids Surf B Biointerfaces 43(3-4): 131-7.
Abstract: Optical properties of spin-cast chitosan films have been determined in the infrared, visible, and ultraviolet region of the spectrum using spectroscopic ellipsometry. Optical constants for the UV-vis-near IR spectra from 130 to 1700 nm were determined using Cauchy dispersion forms combined with Lorentzian oscillator models in the absorptive shorter wavelength regions. Infrared index of refraction and extinction coefficients from 750 to 4000 cm(-1) were determined using ellipsometric data fits to dispersion models based on harmonic oscillators. This modeling determined that optical anisotropy was present and measurable over all wavelength regions of ellipsometric data. To obtain information on the micro- and nano-scale surface structure, tapping mode atomic force microscopy (AFM) imaging was employed to determine morphology and roughness information of dry spin-cast chitosan films.
| Validation of predictors of intraprocedural stent thrombosis in the drug-eluting stent era
Biondi-Zoccai, G. G., G. M. Sangiorgi, et al. (2005), Am J Cardiol 95(12): 1466-8.
Abstract: Although predictors of acute intraprocedural stent thrombosis (IPST) in the drug-eluting stent era have been proposed, external validation is lacking. We thus analyzed the occurrence of IPST in the RECIPE study and found that, among 1,320 patients who underwent drug-eluting stent implantation, IPST occurred in 6 (0.5%), with in-hospital major adverse events in 4 (67%). IPST was predicted by number and total length of implanted stents, baseline minimal lumen diameter, and, in a pooled analysis that incorporated values from the present study and a previous study, use of elective glycoprotein IIb/IIIa inhibitors. Such results may provide useful information to guide prevention of this complication.
| Vancomycin release behaviour from amorphous calcium polyphosphate matrices intended for osteomyelitis treatment
Dion, A., M. Langman, et al. (2005), Biomaterials 26(35): 7276-85.
Abstract: Calcium polyphosphate (CPP) antibiotic delivery matrices were prepared using a unique processing technique involving the exposure of antibiotic-loaded CPP pastes to high humidity for 0, 5, or 24 h. After the designated gelling period, samples were dried for a minimum of 24 h. At several time points out to 130 h, the elution medium was monitored for vancomycin, Ca2+ ion and ortho and poly phosphate release levels. Vancomycin activity was also assessed after 1, 24 and 130 h, while solution 31P-NMR was used to monitor changes in chain length within a 24 hr gelled VCM disc throughout the elution process. The gelling and drying process significantly reduced the rate of vancomycin release during the initial 2-4 h of elution, while extending the effective antibiotic release period by an additional 80 h. The mild conditions associated with matrix fabrication readily allowed for vancomycin incorporation within an environment that did not disrupt antibiotic activity. Throughout the elution process, all sample groups experienced considerable swelling followed by some apparent bulk erosion. Phosphate chain lysis was clearly observed by the end of the elution period. Generally, no strong or consistent correlation existed between matrix degradation and antibiotic release for the treatment groups investigated. An ability to delay antibiotic release using CPPs in conjunction with this protocol supports further investigations into the potential of this matrix as a localized drug delivery system.
| Vapor-phase photo-oxidation of methanol over nanosize titanium dioxide clusters dispersed in MCM-41 host material part 1: synthesis and characterization
Bhattacharya, K., A. K. Tripathi, et al. (2005), J Nanosci Nanotechnol 5(5): 790-6.
Abstract: Nanosize clusters of titania were dispersed in mesoporous MCM-41 silica matrix with the help of the incipient wet-impregnation route, using an isopropanol solution of titanium isopropoxide as precursor. The clusters thus formed were of pure anatase phase and their size depended upon the titania loading. In the case of low (< 15 wt %) loadings, the TiO2 particles were X-ray and laser-Raman amorphous, confirming very high dispersion. These particles were mostly of < or = 2 nm size. On the other hand, larger size clusters (2-15 nm) were present in a sample with a higher loading of approximately 21 wt %. These particles of titania, irrespective of their size, exhibited an absorbance behavior similar to that of bulk TiO2. Powder X-ray diffraction, N2-adsorption and transmission electron microscopy results showed that while smaller size particles were confined mostly inside the pore system, the larger size particles occupied the external surface of the host matrix. At the same time, the structural integrity of the host was maintained even though some deformation in the pore system was noticed in the case of the sample having highest loading. The core level X-ray photoelectron spectroscopy results revealed a + 4 valence state of Ti in all the samples. A positive binding energy shift and the increase of the width of Ti 2p peaks were observed, however, with the decrease in the particle size of supported titania crystallites, indicative of a microenvironment for surface sites that is different from that of the bulk.
| Vapor-phase photo-oxidation of methanol over nano-size titanium dioxide clusters dispersed in MCM-41 host material part 2: catalytic properties and surface transient species
Bhattacharyya, K., S. Varma, et al. (2005), J Nanosci Nanotechnol 5(5): 797-805.
Abstract: We report in this paper on the ultraviolet-assisted vapor-phase oxidation of methanol at room temperature, with the help of nano-size clusters of titanium dioxide dispersed in an MCM-41 silicate matrix. The surface species formed during the adsorption/oxidation of methanol and the transformation that they undergo as a result of ultraviolet irradiation were monitored using in-situ Fourier transform infrared and thermal desorption spectroscopy techniques. Parallel experiments conducted on TiO2/MCM, bulk titania, and pristine MCM-41 samples helped in identifying the individual role of titanium dioxide and host matrix in these processes. The photo-catalytic oxidation of methanol, at concentrations of 0.1 to 1.1 mol% in air, gave rise to formation of CO2 and H2O as products, for both the TiO2/MCM and bulk TiO2 samples. No such reaction occurred on titania-free MCM. Furthermore, the rate of reaction depended upon the TiO2 content of a sample and also on the concentration of methanol in reaction mixture. Thus, the rate of conversion increased progressively with the increase in TiO2 loading from 5 to 21 wt% in TiO2/MCM samples, particularly for the experiments with high concentration of methanol. For low methanol concentration (0.1 mol%) in air, the effect of titania content in MCM was very small. The specific activity (per g of titania) of a sample, on the other hand, showed an inverse relationship with the loading of titanium dioxide in a sample. Infrared and temperature-programmed desorption results revealed that the mode of CH3OH adsorption and the reactivity of the transient species formed during the oxidation process were independent of the size of dispersed titania particles. Thus, the particles of approximately 2-6 nm size, present in TiO2/MCM, exhibited a chemisorption behavior similar to that of the bulk titania. The results of the present study provide strong evidence that the hydroxyl groups, both on the host matrix and at the titania sites, participate independently in the formation of methoxyl groups and at the same time promote the heterogeneous photo-catalytic oxidation of methanol molecules via formation of transient formate groups. Our results also show that the effect of titania crystallite size in the photo-catalytic properties relate mainly to the larger surface area and hence to the enhanced number of chemisorption sites, rather than to the changes in electronic properties.
| Variation in human salivary pellicle formation on biomaterials during the day
Morge, S., E. Adamczak, et al. (1989), Arch Oral Biol 34(8): 669-74.
Abstract: Contact angle measurements were used to study the effects of pellicle formation on polymethyl-methacrylate, dental amalgam and gold. Samples were exposed to saliva in vivo for periods of 5-20 min at three separate occasions during the day. Pellicle drastically increased the wettability of all the materials and effectively sealed off the effect of the original surface activity. Variation in pellicle formation during the day was demonstrated. Pellicles formed at midday showed the least reduction in contact angles compared to those formed during the morning and afternoon. This difference coincided with an increased concentration of inorganic phosphate in saliva at midday. The method enables comparative studies of pellicle formation on hard biosurfaces. The findings indicate differences in the physical behaviour of saliva during the day, and illustrate the importance of making adhesion studies with this variation in mind.
| Variation in pediatric aerosol delivery: importance of facemask
Smaldone, G. C., E. Berg, et al. (2005), J Aerosol Med 18(3): 354-63.
Abstract: We have quantified in vitro the influence of the facemask on the amount of drug delivered (e.g., inhaled mass) by jet nebulizer and pressurized metered dose inhaler (pMDI) valved holding chamber (VHC) combinations (non-detergent-coated and detergent-coated). Pediatric breathing patterns were used with a breathing simulator, which was connected to a face onto which each device was positioned. An inhaled mass filter interposed between the simulator and the face captured the aerosolized drug. Budesonide inhalation suspension (0.25 mg) was used with the jet nebulizers and fluticasone propionate (220 microg) pMDI with the VHCs. Maximal drug delivery was measured using constant flow through each device. Breathing pattern effects were assessed for sealed devices (no leaks) and with facemasks (possible leaks at the facemask). Inhaled mass from both nebulizers and pMDI VHCs was affected by breathing pattern, but compared to nebulizers the pMDI VHCs were significantly more variable and sensitive to several factors. The influence of VHC conditioning combined with effects of breathing pattern resulted in the inhaled mass ranging from 0.7 +/- 0.5 to 53.3 +/- 6.2%. Nebulizers were less variable (9.6 +/- 0.7 to 24.3 +/- 3.1%). Detergent coating of VHC markedly increased the inhaled mass and reproducibility of drug delivery (27.2 +/- 1.4 to 53.3 +/- 6.2%) for pMDI VHC combinations, but these effects were lost in the presence of facemasks. Using pediatric patterns of breathing, nebulizer/facemask combinations delivered 4.1 +/- 0.8 to 19.3 +/- 2.3% of the label dose while pMDI and detergent-coated VHC delivered 4.0 +/- 1.6 to 28.6 +/- 2.5%. Facemask seal is a key factor in drug delivery. Leaks around the facemask reduce drug delivery and for pMDI VHCs can negate effects of detergent coating.
| Various approaches to modify biomaterial surfaces for improving hemocompatibility
Mao, C., Y. Qiu, et al. (2004), Adv Colloid Interface Sci 110(1-2): 5-17.
Abstract: In this paper, the mechanism of thrombus formation on the surface of polymeric materials and the various approaches of modifying biomaterial surfaces to improve their hemocompatibility are reviewed. Moreover, the blood compatibility of the cellulose membrane grafted with O-butyrylchitosan (OBCS) by using a radiation grafting technique was studied. Surface analysis of grafted cellulose membrane was verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA), which confirmed that OBCS was successfully grafted onto the cellulose membrane surfaces. Blood compatibility of the grafted cellulose membranes was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank cellulose membranes as the control. The blood compatibility of OBCS grafted cellulose membranes is better than that of blank cellulose membranes. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving in blood-contacting applications in medical use.
| Varying Ti-6Al-4V surface roughness induces different early morphologic and molecular responses in MG63 osteoblast-like cells
Kim, H. J., S. H. Kim, et al. (2005), J Biomed Mater Res A 74(3): 366-73.
Abstract: Osteoblast response to Ti implants depends not only on the chemistry of the implant but also on the physical properties of the implant surface, such as microtopography and roughness. This study was undertaken to examine early changes in cell morphology and gene expression during the early phase of osteoblast interaction with titanium alloy (Ti-6Al-4V) surfaces of two different roughnesses. MG63 osteoblast-like cells were cultured for 2, 6, 24, and 72 h on smooth (Ra=0.18+/-0.03 microm) and rough (Ra=2.95+/-0.23 microm) Ti-6Al-4V surfaces. Changes in cell proliferation were assessed by measuring cell number after 72 h in culture. Morphological characteristics were observed by scanning electron microscopy after 2, 6, and 24 h of culture. Changes in gene expression for extracellular signal-regulated kinase 2 (Erk2), type I collagen (alpha2[I] collagen), phospholipase C-gamma2 (Plc-gamma2), and beta-actin were measured by RT-PCR after 6 and 24 h in culture. Cell number was significantly higher on the smooth surface. In scanning electron micrographs, cells on smooth Ti-6Al-4V were spherical and raised up from the surface after 2 h in culture. In contrast, cells on the rough surface adopted an irregular, elongated shape that spanned across pits in the surface. At 24 h, cells on the smooth surface had flattened, become elongate, and covered the surface. In contrast, cells on the rough surface appeared more differentiated in shape and the margins of the cells were irregular, with many processes extending out, following the contour of the surface. Of the genes examined, only Erk2 and beta-actin showed a change in expression with surface roughness. Both genes were upregulated (p<0.05) on the rough surface at 6 h. These results indicate that Ti-6Al-4V surface roughness affects osteoblast proliferation, morphology, and gene expression, and that these effects can be measured after periods as short as 2-6 h.
| Vascular graft endothelialization: comparative analysis of canine and human endothelial cell migration on natural biomaterials
Dixit, P., D. Hern-Anderson, et al. (2001), J Biomed Mater Res 56(4): 545-55.
Abstract: Canines are typically used as the standard preclinical model to gauge the success of vascular graft materials. However, canines spontaneously re-endothelialize vascular grafts, whereas humans do not, even after years. This raises questions of why there are differences in vascular healing between humans and other species and whether the canine is the appropriate preclinical model. In the present study we evaluated human and canine endothelial cell (EC) migration on the novel cross-linked collagen biomaterial PhotoFix(TM) pericardium. We compared in vitro migration of these cells on PhotoFix alone and on PhotoFix adsorbed with various growth factors (aFGF and bFGF) and adhesion proteins (fibronectin, collagen IV, vitronectin, and laminin). We also compared human and canine ECs in terms of their morphologies and prostacyclin production. We found that human umbilical vein ECs (HUVECs) and canine ECs (CECs) migrated well on PhotoFix, suggesting that this biomaterial may be a good vascular graft candidate. Both cell types responded similarly to different growth factors and adhesive proteins, but HUVEC migration was consistently higher than that for CECs. This suggested that human in vivo graft re-endothelialization is likely not hindered by poor endothelial migration but is hindered by other cellular or graft properties.
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