Biomedical subjects

T Alan Hatton

Publications and source records attributed to T Alan Hatton.

24 records · Page 2Linked to original sources

PubMed2004

Structure of polymer-stabilized magnetic fluids: small-angle neutron scattering and mean-field lattice modeling.

Small-angle neutron scattering and mean-field lattice modeling were used to characterize a class of water-based magnetic fluids tailored specifically to extract soluble organic compounds from water. The fluids consist of a suspension of approximately 7 nm magnetite (Fe3O4) nanoparticles coated with a bifunctional polymer layer comprised of an outer hydrophilic poly(ethylene oxide) (PEO) region for colloidal stability and an inner hydrophobic poly(propylene oxide) (PPO) region for solubilization of organic compounds. The inner region of the polymer shell is increasingly depleted of water as the fraction of PPO side chains increases. The incorporation of PPO side chains also leads to a small increase in interparticle attraction. The lattice model predicted a shell structure similar to that of a PEO-PPO-PEO triblock copolymer (Pluronic) micelle, with equivalent levels of hydration but with more PEO present in the PPO-rich regions, as the side chains grafted to the surface are less able to segregate than when in free micellar systems.

Journal Article↗

PubMed2004

Polyelectrolyte multilayer films of different charge density copolymers with synergistic nonelectrostatic interactions prepared by the layer-by-layer technique.

Random copolymers composed of diallyldimethylammonium chloride (DADMAC) and acrylamide with varying contents (8-100 mol %) of the cationic DADMAC component were alternated with polyanionic, fully charged poly(styrenesulfonate) to form multilayer thin films. UV-vis spectrophotometry, FTIR spectroscopy, and quartz-crystal microgravimetry (QCM) were employed to follow multilayer buildup. Atomic force microscopy was used to obtain structural information. Layer thicknesses have been determined with small-angle X-ray scattering and ellipsometry, in addition to values calculated from QCM. While in previous work, a critical charge density limit could be observed, below which no layer growth is possible; in this system, multilayer formation takes place with copolymers with charge densities as low as 8 mol %. Instead of a continuous increase of adsorbed amounts with decreasing charge density above the critical charge density, as found in previous work, similar layer thicknesses for films with 100 and 8 mol % charged polyelectrolytes and maximally adsorbed amounts for copolymers in an intermediate charge density region have been found. This adsorption behavior is explained in terms of synergistic nonelectrostatic interactions between the polyelectrolytes used.

Journal Article↗

PubMed2004

Pluronic block copolymers and Pluronic poly(acrylic acid) microgels in oral delivery of megestrol acetate.

Several Pluronic-based formulations were studied in-vitro and in a rat model with respect to the release and bioavailability of megestrol acetate (MA) after oral administration. It was demonstrated that an aqueous, micellar formulation comprising a mixture of a hydrophobic (L61) and a hydrophilic (F127) Pluronic copolymer, significantly enhanced the bioavailability of MA administered orally at relatively low doses (1-7 mg kg(-1)). Pluronic-based microgels (spherical gel particles of sub-millimetre size) were introduced as MA vehicles. The microgels comprised a cross-linked network of poly(acrylic acid) onto which the Pluronic chains were covalently attached. Microgels of Pluronic L92 and poly(acrylic acid) fabricated into tablet dosage forms exhibited dramatically lowered MA initial burst release. The MA release was pH-dependent owing to the pH sensitivity of the microgel swelling, with the drug retained by the microgel at pH 1.8 and released slowly at pH 6.8. In the rat model, a significant increase in MA bioavailability was observed when the microgel-formulated MA was administered orally at a high dose of 10 mg kg(-1), owing to the enhanced retention of the microgel. The study of the microgel passage through the gastrointestinal tract demonstrated the microgel retention characteristic of a very high molecular weight polymer and the absence of any systemic absorption of the polymer.

Acrylates↗

PubMedDate not supplied

Polycationic block copolymers of poly(ethylene oxide) and poly(propylene oxide) for cell transfection.

A facile, one-step synthesis of cationic block copolymers of poly(2-N-(dimethylaminoethyl) methacrylate) (pDMAEMA) and copolymers of poly(propylene oxide) (PPO) and poly(ethylene oxide) (PEO) has been developed. The PEO-PPO-PEO-pDMAEMA (L92-pDMAEMA) and PEO-pDMAEMA copolymers were obtained via free radical polymerization of DMAEMA initiated by polyether radicals generated by cerium(IV). Over 95% of the copolymer fraction was of molecular mass ranging from 6.9 to 7.1 kDa in size, indicating the prevalence of the polyether-monoradical initiation mechanism. The L92-pDMAEMA copolymers possess parent surfactant-like surface activity. In contrast, the PEO-pDMAEMA copolymers lack significant surface activity. Both copolymers can complex with DNA. Hydrodynamic radii of the complexes of the L92-pDMAEMA and PEO-pDMAEMA with plasmid DNA ranged in size from 60 to 400 nm, depending on the copolymer/DNA ratio. Addition of Pluronic P123 to the L92-pDMAEMA complexes with DNA masked charges and decreased the tendency of the complex to aggregate, even at stoichiometric polycation/DNA ratios. The transfection efficiency of the L92-pDMAEMA copolymer was by far greater than that of the PEO-pDMAEMA copolymer. An extra added Pluronic P123 further increased the transfecton efficacy of L92-pDMAEMA, but did not affect that of PEO-pDMAEMA.

Animals↗

PubMedDate not supplied

Protein separations using colloidal magnetic nanoparticles.

Phospholipid-coated colloidal magnetic nanoparticles with mean magnetite core size of 8 nm are shown to be effective ion exchange media for the recovery and separation of proteins from protein mixtures. These particles have high adsorptive capacities (up to 1200 mg protein/mL adsorbent, an order of magnitude larger than the best commercially available adsorbents) and exhibit none of the diffusional resistances offered by conventional porous ion exchange media. Protein-laden particles are readily recovered from the feed solution using high-gradient magnetic filtration.

Adsorption↗

PubMedDate not supplied

Ion-exchange purification of proteins using magnetic nanoclusters.

Polymer-coated magnetic nanoclusters were used for recovery and purification of proteins from both model systems and cell-free Pichia pastoris fermentation broth. The nanoclusters exhibited extremely high capacity for proteins, up to 900 mg/mL adsorbent, and were recovered by high gradient magnetic separation (HGMS) at flow rates of up to 3,600 cm(3)/cm(2) h (flow rates up to 15,000 cm(3)/cm(2) h are possible). The nanoclusters were coated with a primary coating of poly(acrylic acid-co-styrenesulfonic acid-co-vinylsulfonic acid), which allowed both electrostatic and hydrophobic interactions with the protein to be used to enhance specificity for targeted products. With this dual mode separation, nearly pure protein could be recovered from complex mixtures, such as fermentation broth, in a few quick steps.

Culture Media, Conditioned↗