|Articles about Biomaterials|
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| Reinnervation of muscular targets by nerve regeneration through guidance conduits
Chiang, H. Y., H. F. Chien, et al. (2005), J Neuropathol Exp Neurol 64(7): 576-87.
Abstract: We established histopathologic and neurophysiologic approaches to examine whether different designs of polycaprolactone-engineered nerve conduits (hollow vs. laminated) could promote nerve regeneration as autologous grafts after transection of sciatic nerves. The assessments included morphometric analysis at the level of sciatic nerve, neuromuscular junction (NMJ) and gastrocnemius muscle, and nerve conduction studies on sciatic nerves. Six months after nerve grafting, the nerve fiber density in the hollow-conduit group was similar to that in the autologous-graft group; the laminated-conduit group only achieved approximately 20% of these values. The consequences of these differences were reflected in nerve growth into muscular targets; this was demonstrated by combined cholinesterase histochemistry for NMJ and immunohistochemistry for nerve fibers innervating NMJ with an axonal marker, protein gene product 9.5. Hollow conduits had similar index of NMJ innervation as autologous grafts; the values were higher than those of laminated conduits. Among the 3 groups there were same patterns of differences in the cross-sectional area of muscle fibers and amplitudes of compound muscle action potential. These results indicate that hollow conduits were as efficient as autologous grafts to facilitate nerve regeneration, and provide a multidisciplinary approach to quantitatively evaluate muscular reinnervation after nerve injury.
| Relationship between chemotaxis and complement activation by ceramic biomaterials
Remes, A. and D. F. Williams (1991), Biomaterials 12(7): 661-7.
Abstract: This paper examines the relationship between complement activation by ceramic biomaterials and chemotaxis. Complement activation was examined by both neutrophil polarization (a technique which has previously been used to examine chemotaxis) and immunoelectrophoresis assays. The results suggest that at increasing serum concentrations of both calcium hydrogen phosphate and coral (calcium carbonate) powder, the quantity of C3 activation increased, as did the quantity of serum-derived chemotactic factors. In the case of tricalcium phosphate powder, the quantity of C3 activation and the neutrophil polarization response to serum were similar for serum levels between 20 and 80 mg/ml. Complement C3 was not activated in serum incubated with calcium hydrogen phosphate powder and serum incubated with this material was not chemotactic for neutrophils.
| Relationship between intraocular lens biomaterials and posterior capsule opacification
Ursell, P. G., D. J. Spalton, et al. (1998), J Cataract Refract Surg 24(3): 352-60.
Abstract: PURPOSE: To determine whether posterior capsule opacification (PCO) is influenced by intraocular lens (IOL) material. SETTING: A British teaching hospital eye department. METHODS: Ninety eyes were prospectively randomized to receive a poly(methyl methacrylate) (PMMA), silicone, or AcrySof IOL. All lenses had 6.0 mm optics and PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis. Patients having surgical complications were excluded and all patients had standardized medication and follow-up. Posterior capsule opacification was assessed by a digital retroillumination camera using a dedicated software program based on the analysis of texture in the image and calculated as the percentage area of opacified capsule. Data were analyzed 2 years postoperatively. RESULTS: There was a significant difference in percentage of PCO at 2 years among the three lens types (P <.0001). The AcrySof lenses were associated with less PCO (median 11.75%) than PMMA (43.65%) and silicone (33.50%) lenses (P <.001 and P =.025, respectively). The difference between PMMA and silicone lenses was not statistically significant. CONCLUSION: Intraocular lenses made from AcrySof were associated with a significantly reduced degree of PCO.
| Relationship between tissue ingrowth and mesh contraction
Gonzalez, R., K. Fugate, et al. (2005), World J Surg 29(8): 1038-43.
Abstract: Contraction is a well-documented phenomenon occurring within two months of mesh implantation. Its etiology is unknown, but it is suggested to occur as a result of inadequate tissue ingrowth into the mesh and has been associated with hernia recurrence. In continuation of our previous studies, we compared tissue ingrowth characteristics of large patches of polyester (PE) and heavyweight polypropylene (PP) and their effect on mesh contraction. The materials used were eight PE and eight PP meshes measuring 10 x 10 cm2. After random assignment to the implantation sites, the meshes were fixed to the abdominal wall fascia of swine using interrupted polypropylene sutures. A necropsy was performed three months after surgery for evaluation of mesh contraction/shrinkage. Using a tensiometer, tissue ingrowth was assessed by measuring the force necessary to detach the mesh from the fascia. Histologic analysis included inflammatory and fibroblastic reactions, scored on a 0-4 point scale. One swine developed a severe wound infection that involved two PP meshes and was therefore excluded from the study. The mean area covered by the PE meshes (87 +/- 7 cm2) was significantly larger than the area covered by the PP meshes (67 +/- 14 cm2) (p = 0.006). Tissue ingrowth force of the PE meshes (194 +/- 37 N) had a trend toward being higher than that of the PP meshes (159 +/- 43 N), although it did not reach statistical significance. There was no difference in histologic inflammatory and fibroblastic reactions between mesh types. There was a significant correlation between tissue ingrowth force and mesh size (p = 0.03, 95% CI: 0.05-0.84). Our results confirm those from previous studies in that mesh materials undergo significant contraction after suture fixation to the fascia. PE resulted in less contraction than polypropylene. A strong integration of the mesh into the tissue helps prevent this phenomenon, which is evidenced by a significant correlation between tissue ingrowth force and mesh size.
| Relaxivity of liposomal paramagnetic MRI contrast agents
Strijkers, G. J., W. J. Mulder, et al. (2005), Magma 18(4): 186-92.
Abstract: Paramagnetic liposomes, spherical particles formed by a lipid bilayer, are able to accommodate a high payload of Gd-containing lipid and therefore can serve as a highly potent magnetic resonance imaging contrast agent. In this paper the relaxation properties of paramagnetic liposomes were studied as a function of composition, temperature and magnetic field strength. The pegylated liposomes with a diameter of approximately 100 nm were designed for favorable pharmacokinetic properties in vivo. The proton relaxivity, i.e. the T1 relaxation rate per mmol of Gd(III) ions, of liposomes with unsaturated DOPC phospholipids was higher than those with saturated DSPC lipids. Addition of cholesterol was essential to obtain monodisperse liposomes and led to a further, although smaller, increase of the relaxivity. Nuclear magnetic relaxation dispersion measurements showed that the relaxivity was limited by water exchange. These results show that these paramagnetic liposomes are very effective contrast agents, making them excellent candidates for many applications in magnetic resonance imaging.
| Release and retention of biomolecules in collagen deposited on orthopedic biomaterials
Puleo, D. A. (1999), Artif Cells Blood Substit Immobil Biotechnol 27(1): 65-75.
Abstract: Delivery of osteotropic biomolecules directly to the bone-implant interface can alter initial interactions between tissue and biomaterial. To this end, type I collagen coatings containing a model biomolecule, lysozyme, were deposited on Co-Cr-Mo and Ti-6Al-4V. Two deposition methods were examined. In the first, lysozyme was deposited concurrently with collagen, while in the second, protein was impregnated into previously deposited collagen coatings. The amount of collagen and the amount of lysozyme loaded into collagen were varied to provide different amounts of weakly and strongly bound protein. Release and retention of lysozyme were monitored over a 7 d period of incubation in physiological saline. For both methods, larger amounts of collagen in the coatings allowed incorporation of more lysozyme. Additionally, loading collagen coatings with greater amounts of lysozyme resulted in release of more protein. During the first 24-96 h of incubation, loosely bound protein was eluted, resulting in release of 2 micrograms to 55 mg (5-75% of the amount available) of enzymatically active lysozyme. This left 25-95% of the protein bound to the collagen-coated biomaterials and, thus, available for later release during degradation of the collagen.
| Release characteristics and bioactivity of gelatin-tricalcium phosphate membranes covalently immobilized with nerve growth factors
Chen, P. R., M. H. Chen, et al. (2005), Biomaterials 26(33): 6579-87.
Abstract: The gelatin-tricalcium phosphate membranes were cross-linking with low concentration glutaraldehyde solution (GTG). This material has good mechanical property, biocompatibility, and is feasible for surgical manipulation. For axonal regeneration, nerve growth factors (NGF) were immobilized onto the composite (GTG) with carbodiimide. The purpose of this study was to evaluate the release characteristics and bioactivity of NGF after covalent immobilization onto the GTG membranes (GEN). NGF immobilized onto and released from the composite was quantified using ELISA method. PC 12 cells were cultured on the GTG and GEN composites. Cell survival, cytotoxicity, and cellular activity were evaluated by total protein content, LDH activity, and MTT assay respectively. Neurite outgrowth assay was used to evaluate the biological activity of NGF released from GEN composite. From ELISA measurement, the releasing curve for NGF showing two distinctive parts with different slopes indicated that NGF were released from the composite in diffusion-controlled mechanism and degradation-controlled mechanism respectively. While culturing with PC 12 cells, LDH leakage results implied that whether GTG composite cross-linked with NGF or not showed little cytotoxicity. The total protein content and cellular activity of PC 12 cells were lower on GTG and GEN membranes than control group. However, 56%+/-3.98 of PC 12 cells showed significant neurite outgrowth on GEN membranes which was statistically higher than GTG without NGF immobilization. In addition, sustained release of bioactive NGF for two months had been demonstrated by neurite outgrowth assay. From these experiments, it can be concluded that the technique used in the present study is capable of immobilizing NGF onto GTG membranes covalently and remaining the bioactivity of NGF. Therefore, GEN composite can be materials for sustained release of bioactive NGF and a candidate for future therapeutic application in nerve repair.
| Release kinetics from bio-polymeric nanoparticles encapsulating protein synthesis inhibitor- cycloheximide, for possible therapeutic applications
Verma, A. K., K. Sachin, et al. (2005), Curr Pharm Biotechnol 6(2): 121-30.
Abstract: Cycloheximide, a protein synthesis inhibitor, was encapsulated in cross-linked gelatin nanoparticles (Type B, Bovine skin, 75 Bloom) of 168 nm diameter with 26% entrapment efficiency. In-vitro release kinetics of the drug from the nanoparticles was done in phosphate buffer saline (PBS) at pH 7.4 and pH 5.8. The release kinetics showed a bi-phasic curve. Interestingly, the release of drug is approx 90% in acidic pH as compared to 50% release in neutral pH. The particle size was determined by Dynamic Light Scattering (DLS) technique, and size distribution spectra at different pH were observed to vary inversely with increase in pH. These drug loaded nanoparticles were found to be stable in whole blood showing negligible haemolysis. Cytotoxicity in HBL-100 and MCF-7, breast cancer cell lines was done in a 24-72 hrs assay, showing increased anti-tumour activity over a period of time indicating slow release. Dose dependent cytotoxicity was observed after 24 hours upto 72 hours of incubation of nanoparticles while the drug per se (<4 microg) showed 93% toxicity within 24 hours. Phase contrast microscopy of nanoparticle-cell interaction, clearly indicated aggregation along the lipid cell-membrane. Electron Microscopy (TEM, SEM) studies revealed its size and spherical shape. The stability of the particle, the slow and controlled release of drug from the gelatin nanoparticles indicate that it is a good candidate to deliver bio-pharmaceuticals. These behave as "intelligent" carriers for drug delivery, and can be exploited to empty their drug load in acidic medium. The paper focuses on the release kinetics of the gelatin nanoparticles that can be successfully exploited to treat solid tumors.
| Release of bioactive BMP from dextran-derived microspheres: A novel delivery concept
Chen, F. M., Z. F. Wu, et al. (2006), Int J Pharm 307(1): 23-32.
Abstract: Recent developments of biotechnology have produced a great variety of protein and bioactive drugs. For these drugs to be used therapeutically, suitable drug delivery systems have become increasingly essential. Dextran-derived biomaterials have been considered to be compatible matrices for protein and bioactive drugs because of their hydrophilic properties and ability to control drug dissolution and permeability. A novel class of dextran-glycidylmethacrylate (Dex-GMA)/poly(ethylene glycol) (PEG) microspheres were designed and synthesized by polymerization of Dex-GMA emulsified in an aqueous PEG solution. Dex-GMA was prepared by substituting the hydroxyl groups in Dex by GMA. The drug loading and in vitro drug release was evaluated by routine procedure and the biological activity of BMP-loaded microspheres was studied by experimental cytology methods. Recombinant human bone morphogenetic protein-2 (rhBMP-2) were entrapped in dextran-derived microspheres quantitatively and with full preservation of their biological activity. In vitro release kinetics indicated that dextran-derived microspheres could retain rhBMP-2 in a variable manner depending on the preparation and degradation of the microspheres. The release profiles of rhBMP-2 from microspheres as a function of time showed that rhBMP-2 releasing kinetics in vitro fitted to first-order and Higuchi equations. The release profile in vitro was in accord with two phases kinetics law and more than 60% drug were released during 20 days. Cytology studies showed rhBMP-2 microspheres have good biological effects on cultured periodontal ligament cells, and could achieve a longer action time than concentration of rhBMP-2 solution. These properties make those microspheres interesting osteo-conductive BMP carriers, allowing to decrease the amount of implanted factor required for tissue regeneration.
| Release of DNA from dendriplexes encapsulated in PLGA nanoparticles
Ribeiro, S., N. Hussain, et al. (2005), Int J Pharm 298(2): 354-60.
Abstract: Biodegradable PLGA particles of less than 1 microm can encapsulate DNA and DNA-dendron complexes (dendriplexes) providing sustained DNA release for transfecting cells in gene delivery. Two polylysine-based dendrons prepared by solid state peptide synthesis were used to condense pRedN-1 DNA (7.5 kbp), a fluorescent protein vector. The dendrons had 16 free surface amino groups attached to seven lysine groups, bound to a lipid core, one containing three C18 chains and the other a single C10 chain. Increased lipophilicity and molar charge ratios are key factors in producing compact and reproducible dendriplexes, shown by the hydrodynamic diameter which is of the order of 800 nm (p.d.>0.5) at a 2:1 molar charge ratio, a value which decreases to around 200 nm at a 5:1 charge ratio. At lower charge ratios the dendriplexes are negative and have a zeta potential in order of -18 mV. As the ratio increases (5:1, 10:1) the complexes bear a positive potential (13+/-2 mV). This suggests that at the 2:1 ratio the DNA is not fully condensed. The DNA was radiolabelled with 35S dCTP (deoxycytidinetriphosphate) with the removal of the un-incorporated radiolabelled nucleotides. The encapsulation efficiency of dendriplexes in PLGA particles is higher than that for uncomplexed DNA. When the results are normalised for DNA content and particle surface area, complexation of the DNA was found to decrease release rate.
| Remediation of soil contaminated with the heavy metal (Cd2+)
Lin, C. C. and H. L. Lin (2005), J Hazard Mater 122(1-2): 7-15.
Abstract: Soil contamination by heavy metals is increasing. The biosorption process for removal of the heavy metal Cd(2+) from contaminated soil is chosen for this study due to its economy, commercial applications, and because it acts without destroying soil structure. The study is divided into four parts (1) soil leaching: the relationships between the soil leaching effect and agitation rates, solvent concentrations, ratios of soil to solvent, leaching time and pH were studied to identify their optimum conditions; (2) adsorption Cd(2+) tests of immobilized Saccharomycetes pombe beads: different weight percentages of chitosan and polyvinyl alcohol (PVAL) were added to alginate (10 wt.%) and then blended or cross-linked by epichlorohydrin (ECH) to increase their mechanical strength. Next, before blending or cross-linking, different weight percentages of S. pombe 806 or S. pombe ATCC 2476 were added to increase Cd(2+) adsorption. Thus, the optimum beads (blending or cross-linking, the percentages of chitosan, PVAL and S. pombe 806 or S. pombe ATCC 2476) and the optimum adsorption conditions (agitation rate, equilibrium adsorption time, and pH in the aqueous solution) were ascertained; (3) regeneration tests of the optimum beads: the optimum beads adsorbing Cd(2+) were regenerated by various concentrations of aqueous HCl solutions. The results indicate that the reuse of immobilized pombe beads was feasible; and (4) adsorption model/kinetic model/thermodynamic property: the equilibrium adsorption, kinetics, change in Gibbs free energy of adsorption of Cd(2+) on optimum beads were also investigated.
| Removal of aqueous phenol using immobilized enzymes in a bench scale and pilot scale three-phase fluidized bed reactor
Ensuncho, L., M. Alvarez-Cuenca, et al. (2005), Bioprocess Biosyst Eng 27(3): 185-91.
Abstract: The main objective of this work was to investigate the removal of aqueous phenol using immobilized enzymes in both bench scale and pilot scale three-phase fluidized bed reactors. The enzyme used in this application was a fungal tyrosinase [E.C. 220.127.116.11] immobilized in a system of chitosan and alginate. The immobilization matrix consisted of a chitosan matrix cross-linked with glutaraldehyde with an aliginate-filled pore space. This support matrix showed superior mechanical properties along with retaining the unique adsorptive characteristics of the chitosan. Adsorption of the o-quinone product by the chitosan reduced tyrosinase inactivation that is normally observed for this enzyme under these conditions. This approach allowed reuse of the enzyme in repeated batch applications. For the bench scale reactor (1.2-l capacity) more than 92% of the phenol could be removed from the feed water using an immobilized enzyme volume of 18.5% and a residence time of the liquid phase of 150 min. Removal rates decreased with subsequent batch runs. For the pilot scale fluidized bed (60 l), 60% phenol removal was observed with an immobilized enzyme volume of 5% and a residence time of the liquid phase of 7 h. Removal decreased to 45% with a repeat batch run with the same immobilized enzyme.
| Removal of arsenic from groundwater by granular titanium dioxide adsorbent
Bang, S., M. Patel, et al. (2005), Chemosphere 60(3): 389-97.
Abstract: A novel granular titanium dioxide (TiO2) was evaluated for the removal of arsenic from groundwater. Laboratory experiments were carried out to investigate the adsorption capacity of the adsorbent and the effect of anions on arsenic removal. Batch experimental results showed that more arsenate [As(V)] was adsorbed on TiO2 than arsenite [As(III)] in US groundwater at pH 7.0. The adsorption capacities for As(V) and As(III) were 41.4 and 32.4 mgg(-1) TiO2, respectively. However, the adsorbent had a similar adsorption capacity for As(V) and As(III) (approximately 40 mgg(-1)) when simulated Bangladesh groundwater was used. Silica (20 mgl(-1)) and phosphate (5.8 mgl(-1)) had no obvious effect on the removal of As(V) and As(III) by TiO2 at neutral pH. Point-of-entry (POE) filters containing 3 l of the granular adsorbent were tested for the removal of arsenic from groundwater in central New Jersey, USA. Groundwater was continuously passed through the filters at an empty bed contact time (EBCT) of 3 min. Approximately 45,000 bed volumes of groundwater containing an average of 39 microgl(-1) of As(V) was treated by the POE filter before the effluent arsenic concentration increased to 10 microgl(-1). The total treated water volumes per weight of adsorbent were about 60,000 l per 1 kg of adsorbent. The field filtration results demonstrated that the granular TiO2 adsorbent was very effective for the removal of arsenic in groundwater.
| Removal of chromium from industrial waste by using eucalyptus bark
Sarin, V. and K. K. Pant (2006), Bioresour Technol 97(1): 15-20.
Abstract: Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879kJmol(-1) for Cr(VI) and -3.885kJmol(-1) for Cr(III) for removal from industrial effluent. The negative value of DeltaG(0) indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH2. Adsorption capacity was found to be 45mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.
| Removal of copper (VI) from aqueous solution by Ag/TiO2 photocatalysis
Liu, S. X. (2005), Bull Environ Contam Toxicol 74(4): 706-14.
| Removal of estrone and 17beta-estradiol from water by adsorption
Zhang, Y. and J. L. Zhou (2005), Water Res 39(16): 3991-4003.
Abstract: Endocrine disrupting chemicals (EDCs) are the focus of current environment concern, as they can cause adverse health effects in an intact organism, or its progeny, subsequent to endocrine function. The paper reports on the removal of estrone (E1) and 17beta-estradiol (E2) from water through the use of various adsorbents including granular activated carbon (GAC), chitin, chitosan, ion exchange resin and a carbonaceous adsorbent prepared from industrial waste. The results show that the kinetics of adsorption were adsorbent and compound-dependent, with equilibration being reached within 2 h for a waste-derived carbonaceous adsorbent to 71 h for an ion-exchange resin for E1, and within 7 h for the waste-derived carbonaceous adsorbent to 125 h for GAC for E2. Of all the adsorbents tested, the carbonaceous adsorbent showed the highest adsorption capacity, with a maximum adsorption constant of 87500 ml/g for E1 and 116000 ml/g for E2. The GAC also had a very high adsorption capacity for the two compounds, with a maximum adsorption constant of 9290 ml/g for E1 and 12200 ml/g for E2. The effects of some fundamental environmental parameters including adsorbent concentration, pH, salinity and the presence of humic acid and surfactant on adsorption were studied. The results show that adsorption capacity of activated carbon was decreased with an increase in adsorbent concentration and by the presence of surfactant and humic acid. The results have demonstrated excellent performance of a waste derived adsorbent in removing E1 and E2 from water, and indicated the potential of converting certain solid waste into useful adsorbents for pollution-control purposes.
| Removal of hepatitis C virus by G-1 beads in sera from patients with chronic hepatitis C
Moriyama, M., M. Kaneko, et al. (2005), Intervirology 48(2-3): 84-8.
Abstract: Recently, a new method of extracorporeal granulocyte depletion apheresis has been developed to treat inflammatory systemic diseases using an Adacolumn (Japan Immunoresearch Laboratories, Takasaki, Japan) that is filled with acetate cellulose beads (G-1 beads) to adsorb the granulocytes. We examined whether hepatitis C virus (HCV) is adsorbed after incubation of the Adacolumn with the sera from patients with HCV-RNA-positive chronic hepatitis C. PATIENTS AND METHODS: A total of 10 patients with chronic hepatitis C, whose levels of HCV RNA were greater than 800 kIU/ml were examined. The serum was incubated with 500 G-1 beads in a syringe at 37 degrees C for 1 h. After removal of the serum, the beads were washed with RNase-free water. The G-1 beads were removed from the syringe after centrifugation. RNA was extracted from 200 microl of the wash waste and from 10, 50, 100 and 200 beads, respectively, using TRIZol regent. Detection of HCV RNA was performed using the nested PCR method. RESULTS: HCV RNA was detected from as few as 10 G-1 beads. HCV RNA was not detected from waste fluid collected after the last wash from any of the patients. Further, HCV RNA was detected in the initial waste fluid after the 37 degrees C incubation with serum in all of the patients. Since HCV RNA was detected on the G-1 beads, but not from the last washing solution in the current examination, these results suggest that the G-1 beads adsorbed HCV RNA. CONCLUSIONS: Our in vitro study confirmed that G-1 beads adsorbed HCV; therefore, apheresis using a column filled with G-1 beads may reduce the HCV RNA load in the blood of patients with chronic hepatitis C.
| Removal of humic acid foulant from ultrafiltration membrane surface using photocatalytic oxidation process
Fang, H., D. D. Sun, et al. (2005), Water Sci Technol 51(6-7): 373-80.
Abstract: The experimental results indicated that without the TiO2 particles and PCO treatment, the permeate flux of ultrafiltration (UF) membrane declined to 40% of the initial permeate flux after 8 hours filtration. Feeding the humic acid solution with TiO2 particles dosage of 1 g/L with calcium ions into UF membrane, after the same filtration time and PCO reaction at 120 minutes, the permeate flux was increased to about 90% of the initial permeate flux. At longer PCO reaction times, a better water quality of UF permeate was observed. It has been found that with the coexistence of calcium ions in humic acid solution, the smaller molecular fragments of humic acid (HA) generated by PCO reaction may be transferred to the surface of TiO2 by means of adsorption. The humic acid adsorption by TiO2 in the presence of Ca2+ is also pH dependent. The adsorption rates were 21.0, 14.9 and 10.8 ppmTOC/gTiO2 for pH value of 4, 7 and 10 respectively. The combination of effects of PCO mineralization of humic acid into CO2 and adsorption of humic acid by TiO2 through the forming of HA-Ca(2+)-TiO2 aggregate particles were responsible for the removal of humic acid foulant from UF membrane surface.
| Removal of lead from aqueous solutions using an immobilized biomaterial derived from a plant biomass
Chandra Sekhar, K., C. T. Kamala, et al. (2004), J Hazard Mater 108(1-2): 111-7.
Abstract: Because of the severity of heavy metal contamination and potential adverse health impact on the public, a tremendous effort has taken place to purify waters containing toxic metal ions. Traditional methods which have been employed prove to be costly and prohibitive for low level waste remediation. Biosorption is presented as an alternative to traditional physicochemical means for removing toxic metals from ground and wastewaters. Most recently, plant based biomaterials have been of interest. The bark of Hemidesmus indicus, an extensively available plant biomass commonly called as Indian sarsaparilla was used as biomaterial for removal of lead from aqueous streams. Batch experiments were carried out with immobilized biomass of H. indicus (IPBFIX) to optimize the experimental parameters like effect of contact time, initial metal concentration, initial IPBFIX concentration and co-metal ion effect on biosorption of lead from contaminated waters. Column experiments were performed under flow conditions for regeneration and recycle efficiency of IPBFIX and was found to be effective for three cycles. Elution experiments were carried out to remove lead ions from loaded IPBFIX and 100% elution was achieved with a 0.1M HNO(3) solution. The effectiveness of the IPBFIX for biosorption of lead ions was demonstrated using the wastewater samples emanating from a non-ferrous metal industry and the results are presented in this paper. The results from these studies will be useful for a novel phytofiltration technology to remove and recover lead from wastewaters and this can also be well adapted for secondary treatment or polishing of wastewaters. An attempt has been made to remove lead from the lead polluted waters (both ground and surface) from an industrially contaminated sites.
| Renal epithelia in long term gradient culture for biomaterial testing and tissue engineering
Minuth, W. W., K. Schumacher, et al. (2005), Biomed Mater Eng 15(1-2): 51-63.
Abstract: In the organism epithelia perform perfect barrier functions. Strong rheological and mechanical influences constitute the normal environment of this tissue throughout life. Most epithelia are exposed to different fluids at the luminal and basal sides. To obtain realistic information about tissue development in modern biomaterial testing and tissue engineering it is necessary to mimick the natural environment of epithelia. Cultured cells are brought in contact with an artificial extracellular matrix to determine whether proper development into a functional epithelium occurs. As under natural conditions the cultures have to withstand mechanical and fluid stress over a prolonged period of time in close contact to a selected biomaterial. However, development of tissue-specific features such as polarization, tightness and transport under in vitro conditions will only occur, if the biomaterial and the culture conditions support tissue development. Leakage, edge damage and pressure differences during culture have to be avoided so that the natural functions of the growing epithelium can develop. Our aim is to generate functional epithelia derived from renal explants containing stem cells, which are microsurgically isolated and placed into specific O-ring carriers for optimal handling. The cells develop in combination with a collagenous matrix from an embryonic into a functional collecting duct (rCD) epithelium. To achieve optimal culture conditions the tissue is placed in a gradient culture container. A typical environment can be simulated by superfusing different culture media at the luminal and basal sides. Within days epithelia growing inside the gradient container build up a physiological barrier, which is maintained during the whole culture period. The described method allows to investigate the influence of new biomaterials over prolonged periods of time.
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