Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface.

With good contrast in T1 and T2 weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH2CH2O segments of Tween 80, a two spins system is found and modeled well by the equation IZ-I0= S0((1-X) e-tD1 -(1+X) e-tT1) which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions (Iz - I0)t=0 = -2XS0 and (Sz - S0)t=0 = -2S0. For the two spins system, D1 and T1 are corresponding to longitudinal relaxation times of the bound water and the CH2CH2O respectively. Concerning the transverse relaxation experiments of the CH2CH2O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole-dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH2CH2O's nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH2CH2O's longitudinal relaxation experiments and the intermolecular dipole-dipole interactions of the CH2CH2O's transverse relaxation experiments.

Poly(ε-caprolactone)/keratin/heparin/VEGF biocomposite mats for vascular tissue engineering.

Vascular endothelial growth factor (VEGF) is an effective growth and angiogenic cytokine, which stimulates proliferation and survival of endothelial cells, and promotes angiogenesis and vascular permeability. Binding VEGF with heparin could protect it from rapid degradation, subsequently allowing it to be controlled release. Primarily, poly(ε-caprolactone) (PCL) and keratin were coelectrospun, followed by conjugating with heparin and subsequently binding VEGF. The loaded heparin and VEGF on these mats were quantified, respectively. The surface characteristics of mats were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The VEGF delivery results indicated these mats could sustainably release VEGF for 2 weeks. Cell viability assays suggested these mats were valid to accelerate human umbilical vein endothelial cells (HUVECs) proliferation, while inhibit human umbilical arterial smooth muscle cells (HUASMCs) growth under the combined actions of VEGF and heparin. The results tested by blood clotting times (APTT, PT, and TT), hemolysis, and platelet adhesion indicated the mats were blood compatible. To sum up, these biocomposite mats are ideal scaffolds for vascular tissue engineering.

One-step fabrication and characterization of Fe3O4/HBPE-DDSA/INH nanoparticles with controlled drug release for treatment of tuberculosis.

In this study, Fe3O4/hyperbranched polyester-(2-dodecen-1-yl)succinic anhydride2-Dodecen-1-/isoniazid magnetic nanoparticles (Fe3O4/HBPE-DDSA/INH MNPs) with controlled drug release characteristics were synthesized successfully by a simple one-step method. Orthogonal experiments were performed to optimize the loading capacity and encapsulation efficiency of the MNPs. The structure of the Fe3O4/HBPE-DDSA/INH MNPs was characterized by 1H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization mass spectrometry, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, and superconducting quantum interference device measurements, while their properties were characterized based on swelling behavior observations, in-vitro release experiments, and cytotoxicity analysis. The results indicated that the fabricated Fe3O4/HBPE-DDSA/INH MNPs had a high drug-loading capacity and encapsulation efficiency. Further, the drug-release rate of the MNPs was higher in an acidic buffer, indicating that the MNPs were pH-responsive. Swelling studies revealed that the MNPs exhibited diffusion-controlled drug release, while in-vitro release studies revealed that the drug-release properties could be controlled readily, owing to the high encapsulation efficiency of the MNPs and the uniform dispersion of the drug in them. These results collectively suggest that this multifunctional nontoxic drug delivery system, which exhibits good magnetic properties and pH-triggered drug-release characteristics, should be suitable for the treatment of tuberculosis.

Transport of stavudine, delavirdine, and saquinavir across the blood-brain barrier by polybutylcyanoacrylate, methylmethacrylate-sulfopropylmethacrylate, and solid lipid nanoparticles.

Permeability of the anti-human immunodeficiency virus (HIV) agents, including stavudine (D4T), delavirdine (DLV), and saquinavir (SQV), across the in vitro blood-brain barrier (BBB) was studied. Here, the anti-HIV agents were incorporated with polybutylcyanoacrylate (PBCA) nanoparticles (NPs), methylmethacrylate-sulfopropylmethacrylate (MMA-SPM) NPs, and solid lipid nanoparticles (SLNs). Transport of the anti-HIV agents across BBB is a key factor in their applications to the therapy of the acquired immunodeficiency syndrome (AIDS). Experimental results revealed that the drug order of the loading efficiency (LE) on PBCA and MMA-SPM was D4T>DLV>SQV. For the entrapment efficiency (EE) in SLNs, this order was reversed. Also, LE of D4T on MMA-SPM was larger than that on PBCA; however, the reverse was true for DLV and SQV. As the particle size increased, LE decreased and EE increased. For a fixed drug carrier, an increase in the particle size yielded a decrease in the BBB permeability coefficient of the anti-HIV agents. Moreover, enhancement in the BBB permeability was on the carrier order of PBCA>MMA-SPM>SLNs for D4T, and for DLV and SQV, the order became PBCA>SLNs>MMA-SPM. PBCA, MMA-SPM, and SLNs were efficacious carriers of D4T, DLV, and SQV to meliorate BBB permeability by 3-16 folds, indicating the clinical potential of the present NP formulations for the AIDS treatment.

Structure-property investigations with dielectric study on phosphorylcholine-based polyurethane.

Polyurethane with zwitterionic phosphorylcholine on the main chain was synthesized and the structures were defined with FTIR and (1)HNMR. The mechanical (tensile strength, elastic modulus) and biological (platelet adhesion) evaluations of its blend films with polyurethane were of satisfactory results, which were in accordance with the requirements of the medical devices, showing their potential applications as anticoagulant biomaterials. The dielectric spectroscopy was recorded with solid films and with films in water. The dielectric dispersion of the solid films demonstrated the existence of condensed ionic structures, which lead to the rigidity enhancement of the soft segment of the phosphorylcholine-based polyurethane, so that its elastic modulus increased. The dielectric measurement with films in water, providing a measurement for the surface properties in the aqueous environment, offered a semiquantitative description of the interface dynamics of the material with a double-layer model, based on which a new hypothesis on the mechanism of blood or bio-compatibility was proposed that the hydrated surface of the satisfactory biomaterials can response to the outside electromagnetic stimuli with slight strength and prompt relaxation.