Novel inorganic ion exchange materials CsTreat®, CoTreat, CsFloc and CoFloc were tested as precoat filter materials for the removal of radiocobalt and radiocesium from simulated radioactive waste liquids. Experiments were carried out in laboratory scale (120 cm2 Millipore filter unit) and in pilot-scale (10 in. precoat cartridge). The decontamination factors for 134Cs and 57Co tracers was found to increase with increasing tracer feed activities, exceeding a value of 1000 at high feed activities. Kinetic analysis indicated that the kinetic mechanism of the radionuclide uptake in the powdered precoat materials was controlled by film-diffusion. Radiocesium removal was rather insensitive to solution chemistry but radiocobalt uptake was clearly decreased by increasing calcium content of solution. In addition, radiocobalt uptake had a maximum in neutral solution pH. Application of the inorganic ion exchangers as precoat materials looks to be a promising technique for the treatment of nuclear waste effluents (e.g., pond waters and nuclear power plant floor drain waters), enabling much faster flow rates than conventional column operation with granular materials.
The synthesis and characterization of new radiolabeled 75Se-silica nanoparticles are described. These particles have been prepared by dispersion polymerization of tetraethylorthosilicate in ethanol in presence of radiolabeled 75selenium-colloids. The amount of Se-colloids encapsulated within the silica matrix was then increased by two successive seeded polymerizations of tetraethylorthosilicate on the previously formed particles. Kinetic studies and the effect of various factors, i.e. sodium selenite, water and ammonium hydroxide concentrations, on the diameter of these nanoparticles have been elucidated. The Se-silica nanoparticles have been covalently coated by the self-assembled technique with a variety of ω-functionalized alkylsilane compounds. Characterization of these coatings has been performed by Fourier transform-infrared spectroscopy, elemental analysis and floatability studies. The potential use of these varieties of ω-functionalized radiolabeled nanoparticles for drug delivery purposes has been demonstrated in a separate article.
Several bioerodible polymers and one hydrogel were studied as potential bioadhesive materials. A microbalance-based method was used to measure bioadhesive interactions between individual polymer microspheres and rat intestinal tissue. In addition, surface and bulk properties of these microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and contact angle measurements. Polyanhydride microspheres composed of copolymers of fumaric and sebacic acid, produced bioadhesive fracture strengths greater than 50 mN/cm2 with rat small intestinal mucosa in vitro. We suggest that bioadhesion in these bioerodible materials is not attributable to chain entanglement, but instead to hydrogen bonding between hydrophilic functional groups (COOH) and mucus glycoproteins. We also believe that continuous degradation of these materials may enhance their bioadhesive properties by changing surface energy, and increasing both carboxylic acid concentration and surface roughness.
Cisplatin (CDDP), a most powerful anticancer agent, was complexed to a polycarboxylic carrier carboxymethyldextran to form a platinum(II) multicomplex. Complexing occurs by displacement of the chlorine atoms of the platinum coordination complex by hydrogen of polymer side-chains to form mono- or bifunctional anchoring to adjacent carboxyls on the carrier. The carrier-complexed drug interacted with DNA and was pharmacologically active against tumor cells. The drug-carrier complex was immunotargeted to human epidermoid carcinoma (KB) tumors, using the monoclonal antibody (mAb) 108 directed against the epidermal growth factor receptor that is overexpressed on KB cells. Biotinyl-monoclonal antibody was bound to a platinum(II)-carboxymethyldextran-avidin conjugate and the immune complex was administered into established subcutaneous KB tumors to evaluate its effects upon intratumor treatment. The results showed that the immune complex was specifically effective in inhibiting tumor growth. The antibody in the complex must be tumor-specific to anchor the drug-carrier multicomplex to the tumor site since an unbiotinylated antibody, or replacing the anti-KB antibody by a biotinylated antibody of a different specificity, resulted in reduced or abolished inhibitory effects.
Poly(vinyl acetate) (PVAc) has been transformed into a polymer having the structure of PVAcSOMe via hydrolysis, 3-methylthiopropionylation and oxidation. The obtained PVAcSOMe copolymers have been shown to have the property of accelerating the penetration of triphenylphosphite through parchment paper.
Heparin is the gold standard growth inhibitor for vascular smooth muscle cells, with chemistry and bioactivity similar to endogenous reparative compounds, such as heparan sulfate. Thus, heparin should be especially effective against proliferative arterial diseases that involve smooth muscle cells. Yet, at the systemic doses tolerated intermittent subcutaneous injections or intravenous infusion have, if anything, exacerbated rather than alleviated disease. We have demonstrated that far more beneficial effects are observed if one matches the delivery of heparin to the natural release of endogenous growth regulators; namely in a continuous manner, administered directly to specific injured segments of the blood vessel wall. Local, perivascular controlled release of heparin from polymeric matrices inhibited smooth muscle cell proliferation following injury to vascular endothelium: for anticoagulant heparin without the need for systemic anticoagulation; for anticoagulant heparin when administered from a site distant from the injured vessel; and in a manner more efficient than in systemic administration. Some heparin compounds only achieved a therapeutic response when delivered from polymeric devices in the perivascular position.These results lay the groundwork for examining the local control of the vascular response to injury and for investigating site specific means of modulating these processes. Polymeric drug delivery systems offer the potential for novel therapies and a means of investigating complex disease states. Future work on materials, formulations, and pharmacokinetics will aid immensely in these regards.
Derivatives of protected phenols with chiral aminoalcohol or aminoether-containing substituents in the 4-position of the aromatic ring were prepared and shown to react readily, after deprotection, with chloromethylated styrene-divinylbenzene polymers. The chirality in the substituents originated either from the use of a chiral monomeric aminoalcohol derivative or from the introduction of a chiral epoxide, which in turn was ring opened by a chiral amine. The chiral epoxides were obtained by either asymmetric synthesis or starting from a chiral glycidyl derivative.
The preparation and properties of 8 N-phenylsubstituted polyacrylohydroxamic acids as ion exchange resins are described. These were synthesized by the reaction of polyacryloyl chloride with N-aryl hydroxylamines in etherial medium. The chelating properties of the resins were determined and compared with each other. The extraction of divalent metal ions as a function of pH and kinetics of their sorption were studied. The chromatographic separation of metal ions from the mixtures is also described.
Fiber chromatography is prominent among the novel systems being developed for downstream processing. In this research, a polymer based anion-exchange support with fiber geometry has been developed. The fiber support has an asymmetric structure, with a dense skin and a porous substructure. Equilibrium adsorption capacities of this support for bovine serum albumin and β-lactoglobulin were measured. Isotherms were obtained at different pH and salt concentrations, and were found to be Langmuirian. It was also found that ion-exchange is the dominant adsorption mechanism, and, due to a large internal surface area, the support has a high adsorption capacity. The fiber support was packed in a bed, and tested for its applicability in the isolation of proteins from dilute solutions. The fiber column is shown to have a significantly lower pressure drop than columns packed with commercial, spherical supports. The frontal throughout for this column was evaluated at different conditions. The throughput was found to increase with flow rate and protein concentration, but the yield dropped with an increase in flow rate. However, the throughput and yield were high when a high concentration of protein was loaded at a low flow rate and washed at a very high flow rate.
Studies have been conducted on the sorption of several heavy metal ions Cu(II), Ni(II), Zn(II), Cd(II) and Al(III) from aqueous solutions on the new chelating exchangers of sporopollenin (Lycopodium clavatum) as a function of pH at several temperatures between 20 and 50°C. The novel metal-ligand exchange resins possessing oxime and carboxylic acid side arm functionality were prepared through the reaction of diaminosporopollenin with dichloroantiglyoxime and bromoacetic acid. The sorption of all metals increased considerably in the range of pH 6–10 and was observed in sequence as: Cu ≥ Ni > Zn > Cd > Al for carboxylated-diaminoethyl-sporopollenin (DAEC) and Ni ≥ Cu > Zn > Cd > Al for bis-diaminoethyl-glyoxime-sporopollenin (bDAEG). The level of pH of the aqueous medium had a large influence on the sorption capacity, and the uptake of metals, except Al(III), was found to be 90% or more. The metal-form resins afforded complete recovery of the sorbed species by acid stripping. Both resins also showed high stability towards concentrated acids and bases and retained their high capacity for heavy metals.
A new process has been developed for gel-coating a weak-base resin polyethyleneimine (PEI) as a thin layer on high surface area silica using preloaded Cu(II) as the host ion on silica and glutaraldehyde as the cross-linking agent, followed by removal of the host ion by leaching with acid. The >NCH(OH) group introduced by the reaction with glutaraldehyde is found to enhance both U and Fe sorption, the effect, however, being relatively more pronounced on the latter. An ON mole ratio ∼0.70 of the gel-coated PEI resin is found to be optimum for U sorption. In U sorption from dilute (0.1–0.4 mM) aqueous solutions of UO2SO4 at pH 4–5, the gel-coated resin exhibits several times higher capacity than a conventional bead-form resin Dowex-1X8. However, the capacity of the resin-coated silica sorbent, containing a large percentage of low-capacity silica, is only comparable to that of the bead-form Dowex resin at low solution concentrations. The gel-coated resin also exhibits a significantly faster rate of attainment of equilibrium sorption as compared to the bead-form Dowex resin, the sorption kinetics being diffusion-controlled with a high value of 8.4 × 10−6 cm2/s for the product of distribution coefficient and effective diffusivity. The stripping of the sorbed U from the gel-coated sorbent with 2 N H2SO4 is nearly instantaneous.
A novel photopolymerized hydrogel material has been developed for use as a drug delivery vehicle for bioactive materials. The hydrogel precursor consists of polyethylene glycol copolymerized with an α-hydroxy acid and with acrylate termini at each end. The precursor is water-soluble and non-toxic. The precursor polymerization conditions are very mild, and polymerization can be carried out in direct contact with cells and tissues. The degradation rate and permeability of the hydrogel can be altered by changing the composition of the precursors, allowing use of this class of materials for a variety of applications. In vitro release of proteins and oligonucleotides is reported.
Resin (RPPBD) prepared by Friedel-Craft's polycondensation of 2,4-dihydroxypropiophenone with 1,4-butane diol in the presence of polyphosphoric acid catalyst proved to be a selective ion-exchange resin and indicates coordination tendency for some metal ions. The resin was characterized by elemental analysis, IR spectra, viscosity study and its number average molecular mass (Mn) was determined by non-aqueous titration and found to be 2475 g/mol. Chelation ion-exchange properties of this resin have also been studied employing batch equilibration method. It was employed to study selectivity of metal ion uptake over a wide ph range and in media of various ionic strength. The overall rate of metal uptake follows the order: UO22+ > Fe2+ > Cu2+ > Ni2+
A newly available, macroporous anion-exchange resin Reillex™ HPQ, which has about 70% of the pyridine rings quaternized by the addition of methyl groups, has been used in the chloride form for the sorption of sulfide from alkaline aqueous medium. Comparative data on sulfide sorption capacity and kinetics in alkaline media are presented for this new resin and a common anion exchange resin Dowex-1-X8, both used in chloride form. The sulfide sorption capacities of HPQ(Cl−1) and Dowex-1(Cl−1), activated by treatment with mixed NaCl/HCl solution, are found to be 4.8 and 2.5 mmol S/g (dry), respectively, compared to the respective total exchange capacities of 4.6 and 5.6 mEq/g (dry), indicating that sulfide is predominantly sorbed as univalent HS− on HPQ(Cl−) and as bivalent S2− on Dowex-1(Cl−) this is attributed to the occurrence of nearly 30% of the pyridine sites in HPQ(Cl−) in protonated form, contributing to lower pH inside the resin phase as compared to external medium. The chloride/sulfide exchange kinetics, in conditions of particle diffusion control and infinite solution volume, are predicted with good approximation by the Nernst-Planck model. Both the chloride and sulfide counterions taking part in the exchange process diffuse very slowly in the resin, the diffusion coefficients being in the order of 10−10 cm2/s, though chloride ions have relatively higher diffusivity than the sulfide ions.
Immobilized catalysts were prepared from silica gel and montmorillonite functionalized by silane coupling reagents. Complexes with metal ions were easily formed. The dioxygen oxidation of hydrocarbon using the immobilized catalyst was investigated. Cyclohexanol (mainly) and some cyclohexanone were produced by the oxidation of cyclohexane at ordinary temperature, under atmospheric pressure. Dioxygen oxidation of the non-activated β-position of the ethyl group in ethylbenzene was observed in the presence of cobalt ion-immobilized montmorillonite catalyst in the presence of lithium ion.
The design of drug-carrying elastomers based on poly(phosphoester-urethanes) (PPUs) is presented. Bis(2-hydroxyethyl)phosphite and bis(6-hydroxyhexyl)phosphite were used as the chain extenders and 1,4-butane diisocyanate was the basis of the hard segment. The labile phosphoester linkage in the backbone of the PPU confers biodegradability on the polymer. Using the reactive phosphite side chain in the PPUs, p -aminosalicylic acid and benzocaine were attached pendantly to the polymer with or without a spacer. In vitro release of both drugs was complete in several hours. In contrast, ethambutol incorporated into the backbone of the polymer was released in over 10 days. Preliminary cytotoxicity of the drug-carrier to a macrophage cell line was also assessed.
An approach to enhance the immunogenicity of peptide-based vaccines for malaria and the immunoregulatory activity of recombinant human interleukin-1α (IL-1) is described. The approach involves the encapsulation of these molecules in, and their controlled release from, biodegradable polyester microspheres of lactic and glycolic acids (PLGA). The microspheres are prepared by the modified solvent evaporation method based on a double emulsion. Two types of microspheres composed of PLGA (75:25 lactic/glycolic acid) and of different MW were constructed for each molecule. The release characteristics of these molecules from these microspheres were evaluated using spectroscopy and bioactivity assays. In vivo studies established the feasibility of PLGA carriers as an immunization vehicle for malaria peptide-based vaccines; the induced immune responses in mice were stronger than those obtained with peptide in complete Freund's adjuvant. In addition, these studies provide preliminary evidence that PLGA microspheres with encapsulated IL-1 can be used as a new strategy for the efficient delivery of this cytokine to tumor sites in immunotherapy.
