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PubMed2006

Platelet adsorption and hemolytic properties of liquid crystal/composite polymers.

The aim of this study is to investigate how the presence of liquid crystal, cholesteryl oleyl carbonate, embedded into polymers (PMMA, Eb270, PU) affects the biocompatibility of composite membranes with human blood. The effects of different surface textures of composite membranes on platelet adhesion and platelet activation were evaluated as well. The adhesion and geometric deformation of platelets were demonstrated by SEM. The quantitative assay of platelet activation was determined by measuring the production of P-Selectin, and by measurement of the blood clotting index when PRP blood was incubated with pure polymer films and composite membranes. Moreover, the hemolysis studies on the damage to red blood cells were performed to gain information on the hemocompatibility of these biomaterials. The results showed that inclusion of cholesteryl oleyl carbonate (COC) embedded in composite membranes, improves their biocompatibility with respect to a substantial reduction of platelet adhesion and the controlled decrease of platelet activation. As the COC content of composite membranes was increased, the value of the blood clotting index increased and the production of P-Selectin decreased. The results also showed that the presence of COC resulted in a decrease of hemolysis ratios. Comparing among three different composite membranes, the best biocompatibility is achieved when PU/COC> or ==Eb270/COC>PMMA/COC. The in vitro studies performed in this work suggest that it may be reasonable to use liquid crystal COC as a mean of surface modification to improve the blood compatibility of biopolymers.

Acrylic Resins↗

PubMed2004

Evaluation and comparison of tailor-made stationary phases based on spherical silica-based beads for capillary electrochromatography via peptide separation analysis.

Small cyclic peptides have been employed to elucidate the performance of novel sorbents as stationary phases in capillary electrochromatography (CEC). In this paper chain length dependencies for ordinary liquid chromatographic sorbents are reported together with findings acquired on beads specifically designed to suit CEC. The latter, tailor-made, spherical, porous silica exhibits a distinguished surface modification to meet the criteria anticipated to enhance performance profiles in CEC. With well-characterised peptides resembling the analytes, probing of the CEC system in a systematic manner (predominantly via the organic modifier content of the background electrolyte (BE)) reveals insight into the complex interplay occurring in such analytical systems at the molecular and sub-molecular level in particular upon various modes of interaction.

Amino Acid Sequence↗

PubMed2004

Selective separation of arsenopyrite from pyrite by biomodulation in the presence of Acidithiobacillus ferrooxidans.

Effective methods for selective separation using flotation or flocculation of arsenopyrite from pyrite by biomodulation using Acidithiobacillus ferrooxidans are presented here. Adhesion of the bacterium to the surface of arsenopyrite was very slow compared to that to pyrite, resulting in a difference in surface modification of the minerals subsequent to interaction with cells. The cells were able to effectively depress pyrite flotation in presence of collectors like potassium isopropyl xanthate and potassium amyl xanthate. On the other hand the flotability of arsenopyrite after conditioning with the cells was not significantly affected. The activation of pyrite by copper sulfate was reduced when the minerals were conditioned together, resulting in better selectivity. Selective separation could also be achieved by flocculation of biomodulated samples.

Absorption↗

PubMed2005

Silica coating of silver nanoparticles using a modified Stober method.

Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory.

Journal Article↗

PubMed2005

Superhydrophobicity of 2D ZnO ordered pore arrays formed by solution-dipping template method.

Large-scale 2-dimensional ZnO ordered pore arrays (films) were fabricated by a solution-dipping colloidal monolayer method. The morphologies of the films are precursor-concentration-dependent. Higher concentration leads to rougher morphology. The wettability of such ordered porous films was studied. It was shown that the ordered pore structure of as-prepared samples can effectively enhance the hydrophobicity of ZnO and the water contact angle (CA) on the film surface increases from 125 degrees to 143 degrees with the rise of precursor concentration from 0.3 to 1.0 M, indicating concentration-controlled hydrophobicity. Meanwhile, a photoinduced reversal transition of wettability between hydrophobicity and hydrophilicity was observed on these films. The difference between hydrophobic and hydrophilic CAs can be tuned from 89 degrees to 138 degrees by precursor concentration. After surface modification by fluoroalkylsilane, these ordered pore arrays demonstrate superhydrophobicity with water CAs from 152 degrees to 165 degrees, depending on the precursor concentration. Especially for the ordered porous film fabricated by high precursor concentration (1.0 M), the large water CA (165 degrees) and small sliding angle (less than 5 degrees) were obtained. This work has demonstrated that if such ordered pore arrays are used for some micro- or nanodevices, they will be waterproof and even self-cleaning.

Journal Article↗

PubMed2005

Photophysics and charge dynamics of Q-PbS based mixed ZnS/PbS and PbS/ZnS semiconductor nanoparticles.

The surface of ZnS and PbS has been modified by interfacing PbS on ZnS and ZnS on PbS nanoparticles. This produced core-shell nanocomposites ZnS/PbS and PbS/ZnS with tunable electronic properties. In both structures PbS particles are present in cubic form with an average diameter of about 6 nm. The addition of Pb2+ (3 x 10(-4) mol dm(-3)) to Q-ZnS (1.5 x 10(-4) mol dm(-3)) in the basic pH range produces size-quantized fluorescent PbS particles coated by metal hydroxides. In these particles the relaxation kinetics of charge carriers has been followed using a picosecond single-photon counting technique. At 1.5 x 10(-4) mol dm(-3) Pb2+ an interfacial relaxation of charge from ZnS to PbS phase could be observed in subnanosecond time domain. An increase in [Pb2+] from 2 x 10(-4) to 1 x 10(-3) mol dm(-3) enhanced the average emission lifetime from 9.4 to 19.4 ns. Composite PbS/ZnS particles are produced at high [ZnS] only. These particles had emission lifetime in mus time range. The extent of charge separation and the dynamics of charge carriers could be manipulated by the surface modification of these nanostructures.

Journal Article↗

PubMed2006

Adsorption of methyl mercaptan on surface modified activated carbon.

The influence of surface modification of activated carbon on the adsorption of methyl mercaptan in N(2) was investigated. The modification of the activated carbon was carried out by treatment with HNO(3)/H(2)SO(4) solutions, heat-treatment in Ar, and adsorption of cetylamine. Acid-treatment increased the adsorption of methyl mercaptan compared with the original activated carbon, and the adsorbed amounts increased with ratio of H(2)SO(4) in HNO(3)/H(2)SO(4) solutions. This result suggests that hydrogen bonding between acidic groups formed by acid-treatment and thiol groups of methyl mercaptan plays a role in adsorption of methyl mercaptan on activated carbon.

Journal Article↗

PubMed2004

WGA-grafted PLGA-nanospheres: preparation and association with Caco-2 single cells.

Biotech drugs are poorly absorbed, highly susceptible to loss of activity, and require formulations with protective effects. Their incorporation into nanospheres is a promising approach since colloidal formulations were shown to be absorbed. Due to rather low absorption rates the surface engineering with absorption enhancing agents is a current challenge. Thus, an optimized protocol relying on carbodiimide-mediated covalent binding of biorecognitive ligands to the surface of biodegradable and biocompatible poly(D,L-lactic-co-glycolic)acid (PLGA) nanospheres was established. Important parameters such as retainment of particle size distribution and biorecognitive characteristics of the ligand as well as storage stability were considered. As exemplified by nanoparticles grafted with wheat germ agglutinin (WGA) as a carbohydrate binding ligand and Caco-2 single cells, flow cytometry as well as confocal laser scanning microscopy revealed improved cytoassociation of the nanoscaled carriers as compared to the unmodified ones. As detected by flow cytometry, the binding of WGA-decorated nanospheres considerably increases the roughness of the cell surface with increasing ligand density. Additionally, the biorecognitive nanoparticles were not toxic in the Caco-2 model. The protocol presented for surface modification of nanospheres promises high versatility of application in search for biorecognitive ligands enhancing the cytoadhesion, cytoinvasion as well as transcellular transport of colloidal carriers.

Binding Sites↗

PubMed2005

Targeted nanoparticles for drug delivery through the blood-brain barrier for Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia among the elderly, affecting 5% of Americans over age 65, and 20% over age 80. An excess of senile plaques (beta-amyloid protein) and neurofibrillary tangles (tau protein), ventricular enlargement, and cortical atrophy characterizes it. Unfortunately, targeted drug delivery to the central nervous system (CNS), for the therapeutic advancement of neurodegenerative disorders such as Alzheimer's, is complicated by restrictive mechanisms imposed at the blood-brain barrier (BBB). Opsonization by plasma proteins in the systemic circulation is an additional impediment to cerebral drug delivery. This review gives an account of the BBB and discusses the literature on biodegradable polymeric nanoparticles (NPs) with appropriate surface modifications that can deliver drugs of interest beyond the BBB for diagnostic and therapeutic applications in neurological disorders, such as AD. The physicochemical properties of the NPs at different surfactant concentrations, stabilizers, and amyloid-affinity agents could influence the transport mechanism.

Alzheimer Disease↗

PubMed2004

Disentangling Early Stone Age palimpsests: determining the functional independence of hominid- and carnivore-derived portions of archaeofaunas.

Determining the extent to which hominid- and carnivore-derived components of fossil bone palimpsests formed independently of each other can provide valuable information to paleoanthropologists interested in reconstructing the foraging adaptations of hominids. Because stone tool cutmarks, hammerstone percussion marks, and carnivore tooth marks are usually only imparted on bone during nutrient extraction from a carcass, these bone surface modifications are particularly amenable to the types of analyses that might meet this goal. This study compares the percentage of limb bone specimens that preserve evidence of both hominid- and carnivore-imparted bone damage from actualistic control samples and several Plio-Pleistocene archaeofaunas, including new data from Swartkrans Member 3 (South Africa). We argue that this procedure, which elucidates the degree of hominid-carnivore independence in assemblage formation, will allow researchers to extract for focused analyses high integrity components (hominid and carnivore) from presumably low integrity sites. Comparisons suggest that the hominid- and carnivore-derived components from sites in Olduvai Gorge Bed II (Tanzania), the ST Site Complex at Peninj (Tanzania), and Swartkrans Member 3 formed largely independent of each other, while data from the FLK 22 Zinjanthropus (FLK Zinj) site (Olduvai Gorge Bed I) indicate significant interdependence in assemblage formation. This contrast suggests that some Early Stone Age assemblages (e.g., the Olduvai Gorge Bed II sites, the Peninj ST Site Complex, and Swartkrans Member 3) are probably more useful than others (e.g., FLK Zinj) for assessing the maximal carcass-acquiring abilities of early hominids; in such assemblages as those in the former set, sole hominid-contribution is more confidently discerned and isolated for analysis than in assemblages such as FLK Zinj.

Animals↗

PubMed2006

Faunal remains from Porc-Epic: paleoecological and zooarchaeological investigations from a Middle Stone Age site in southeastern Ethiopia.

The Middle Stone Age (MSA) sediments of Porc-Epic Cave near Dire Dawa, Ethiopia, have produced a large assemblage of archaeofaunal remains dating to the later periods of the Late Pleistocene. As one of the few MSA faunal assemblages from East Africa subject to detailed analysis, it provides rare insight into the foraging behavior of the early modern humans in this region. The MSA fauna include taxa that were not historically present in the area, with the occurrence of reduncines and alcelaphines indicating widespread grasslands and proximity to a perennial source of water. The faunal analysis examined several lines of evidence, including breakage patterns, surface modification, and skeletal-element representation. By incorporating comparisons with multiple actualistic data sets, the analysis of the assemblage demonstrates that, while the influence of carnivores and other biotic agents was evident, the faunal remains were accumulated primarily by hominid activity. The skeletal-element representation at Porc-Epic includes an abundance of high utility bones, in contrast to the predominance of "head-and-foot" elements documented at other MSA and Middle Paleolithic (MP) sites. The MSA occupants of Porc-Epic effectively exploited a wide range of prey with more emphasis on small- and medium-sized mammals.

Animals↗

PubMed2005

Comparisons of low-cost adsorbents for treating wastewaters laden with heavy metals.

In this article, the removal performance and cost-effectiveness of various low-cost adsorbents derived from agricultural waste, industrial by-product or natural material are evaluated and compared to those of activated carbon for the removal of heavy metals (Cd(II), Cr(III), Cr(VI), Cu(II), Ni(II) and Zn(II)) from metals-contaminated wastewater. To highlight their technical applicability, selected information on pH, dose required, initial metal concentration, adsorption capacity and the price of the adsorbents is presented. It is evident from the survey of 102 published studies (1984-2005) that low cost adsorbents derived from agricultural waste have demonstrated outstanding capabilities for the removal of heavy metal (Cr(VI): 170 mg/g of hazelnut shell activated carbon, Ni(II): 158 mg/g of orange peel, Cu(II): 154.9 mg/g of soybean hull treated with NaOH and citric acid, Cd(II): 52.08 mg/g of jackfruit), compared to activated carbon (Cd(II): 146 mg/g, Cr(VI): 145 mg/g, Cr(III): 30 mg/g, Zn(II): 20 mg/g). Therefore, low-cost adsorbents can be viable alternatives to activated carbon for the treatment of metals-contaminated wastewater. It is important to note that the adsorption capacities presented in this paper vary, depending on the characteristics of the individual adsorbent, the extent of surface modification and the initial concentration of the adsorbate. In general, technical applicability and cost-effectiveness are the key factors that play major roles in the selection of the most suitable adsorbent to treat inorganic effluent.

Adsorption↗

PubMed2006

GM-CSF-surface-modified B16.F10 melanoma cell vaccine.

Through the specific and tight interaction between streptavidin and biotin, a novel platform was developed to allow for rapid (less than 2h), efficient and durable display of streptavidin-tagged bioactive GM-CSF on the surface of biotinylated B16.F10 tumor cells. This technology involved biotinylation of the cell membrane with a biotin derivative and surface modification of the biotinylated cells with the bi-functional fusion protein, streptavidin-tagged GM-CSF. Furthermore, the resultant GM-CSF-modified B16.F10 whole tumor cell vaccine could induce strong and long-lasting systemic protection against the wild-type tumor challenge. Therefore, the platform may represent a fast, efficient and safe approach for the whole tumor cell vaccination.

Animals↗

PubMed2005

Low proliferation and high apoptosis of osteoblastic cells on hydrophobic surface are associated with defective Ras signaling.

The hydrophobic (HPB) nature of most polymeric biomaterials has been a major obstacle in using those materials in vivo due to low compatibility with cells. However, there is little knowledge of the molecular detail to explain how surface hydrophobicity affects cell responses. In this study, we compared the proliferation and apoptosis of human osteoblastic MG63 cells adhered to hydrophilic (HPL) and hydrophobic surfaces. On the hydrophobic surface, less formation of focal contacts and actin stress fibers, a delay in cell cycle progression, and an increase in apoptosis were observed. By using fibroblast growth factor 1 (FGF1) as a model growth factor, we also investigated intracellular signaling pathways on hydrophilic and hydrophobic surfaces. The activation of Ras, Akt, and ERK by FGF1 was impaired in MG63 cells on the hydrophobic surface. The overexpression of constitutively active form of Ras and Akt rescued those cells from apoptosis and recovered cell cycle progression. Furthermore, their overexpression also restored the actin cytoskeletal organization on the hydrophobic surface. Finally, the proliferative, antiapoptotic, and cytoskeletal effects of constitutively active Ras in MG63 cells on the hydrophobic surface were blocked by wortmannin and PD98059 that inhibit Akt and ERK activation, respectively. Therefore, our results suggest that the activation of Ras and its downstream molecules Akt and ERK to an appropriate level is one of crucial elements in the determination of osteoblast cell responses. The Ras pathway may represent a cell biological target that should be considered for successful surface modification of biomaterials to induce adequate cell responses in the bone tissue.

Androstadienes↗

PubMed1998

Measures to control blood activation during assisted circulation.

Major improvements in heart assist devices have allowed prolonged mechanical circulatory support with successful subsequent weaning or heart transplantation. The contact of blood with biomaterials used in life-sustaining devices and numerous biomaterial-independent factors elicit a systemic inflammatory response, which involves activation of various plasma protein systems and blood cells. Prolonged mechanical circulatory support elicits a systemic inflammatory response and hemostatic perturbations similar to that reported during cardiopulmonary bypass. However, in the setting of prolonged assistance, time has a complex and ill-known influence on blood activation. Methods to reduce blood activation during prolonged assisted circulation are derived from cardiopulmonary bypass investigations. Improving the biocompatibility of artificial devices can be achieved either by biomaterial surface modifications, by inhibition of biologic cascades leading to blood activation, or by controlling end points of biologic cascades. However, the necessity to respect the integrity of the organism during prolonged assistance precludes most systemic interventions and limits the control of blood activation to the area of the device.

Assisted Circulation↗

PubMed2000

Biomolecular interactions measured by atomic force microscopy.

Atomic force microscopy (AFM) is nowadays frequently applied to determine interaction forces between biological molecules. Starting with the detection of the first discrete unbinding forces between ligands and receptors by AFM only several years ago, measurements have become more and more quantitative. At the same time, theories have been developed to describe and understand the dynamics of the unbinding process and experimental techniques have been refined to verify this theory. In addition, the detection of molecular recognition forces has been exploited to map and image the location of binding sites. In this review we discuss the important contributions that have led to the development of this field. In addition, we emphasize the potential of chemically well-defined surface modification techniques to further improve reproducible measurements by AFM. This increased reproducibility will pave the way for a better understanding of molecular interactions in cell biology.

Biophysics↗

PubMed1999

Characterisation of the binding interaction between poly(L-lysine) and DNA using the fluorescamine assay in the preparation of non-viral gene delivery vectors.

A major factor limiting the development of non-viral gene delivery systems is the poor characterisation of polyelectrolyte complexes formed between cationic polymers and DNA. The present study uses the fluorescamine reagent to improve characterisation of poly(L-lysine) (pLL)/DNA complexes post-modified with a multivalent hydrophilic polymer by determining the availability of free amino groups. The results show that the fluorescamine reagent can be used to monitor the self-assembly reaction between pLL and DNA and the degree of surface modification of the resultant complexes with a hydrophilic polymer. This experimental approach should enable the preparation of fully defined complexes whose properties can be better related to their biological activity.

Animals↗

PubMed1990

Effects of incubation time in serum and capacitation on spermatozoal reactivity with antisperm antibodies.

Sperm reside within the female reproductive tract before the occurrence of fertilization. During this time they undergo surface modifications associated with changes in their functional state. To study their antigenic expression, capacitated and acrosome-reacted sperm were incubated with sera that had previously been tested for antisperm antibodies against fresh washed sperm, as detected by indirect immunobead binding. Forty-eight percent of previously positive and 20% of previously negative sera reacted differently with sperm after an extended time (18 hours) of incubation in serum or after sperm capacitation. These results suggest that current techniques of antisperm antibodies detection be modified to include testing sera after prolonged incubation times with both capacitated as well as fresh sperm.

Acrosome↗