Chen-Yu Kao

A liposomal nanoscale contrast agent for preclinical CT in mice

OBJECTIVE The goal of this study was to determine if an iodinated, liposomal contrast agent could be used for high-resolution, micro-CT of low-contrast, small-size vessels in a murine model. MATERIALS AND METHODS A second-generation, liposomal blood pool contrast agent encapsulating a high concentration of iodine (83-105 mg I/mL) was evaluated. A total of five mice weighing between 20 and 28 g were infused with equivalent volume doses (500 microL of contrast agent/25 g of mouse weight) and imaged with our micro-CT system for intervals of up to 240 min postinfusion. The animals were anesthetized, mechanically ventilated, and vital signs monitored allowing for simultaneous cardiac and respiratory gating of image acquisition. RESULTS Initial enhancement of about 900 H in the aorta was obtained, which decreased to a plateau level of approximately 800 H after 2 hr. Excellent contrast discrimination was shown between the myocardium and cardiac blood pool (650-700 H). No significant nephrogram was identified, indicating the absence of renal clearance of the agent. CONCLUSION The liposomal-based iodinated contrast agent shows long residence time in the blood pool, very high attenuation within submillimeter vessels, and no significant renal clearance rendering it an effective contrast agent for murine vascular imaging using a micro-CT scanner.

Plasma-induced grafted polymerization of acrylic acid and subsequent grafting of collagen onto polymer film as biomaterials

Polyacrylic acid (pAA) was introduced onto Ar-plasma treatment silicone rubber (SR) membrane surfaces by plasma-induced grafted polymerization. Collagen (type III) was also linked with the carboxylic group of pAA grafted onto the SR surface via a carbodiimine agent to obtain a secondary structure of SR. The SR surface properties were characterized by ATR-FTIR, ESCA, contact angle, and SEM. The biocompatibility of the SR surface was evaluated by a culture of cornea epithelial (CE) cells. Subsequently, 75-450 micrograms cm-2 of pAA were obtained on the SR surfaces under different reactive conditions; 3-12 micrograms cm-2 of collagen were linked on modified surfaces of SR. Moreover, ATR-FTIR and ESCA were utilized to confirm the proceedings of these reactions. The hydrophility of the modified SR was measured by a contact angle meter. The values of contact angle for SR grafted with pAA were approximately 45-50 degrees; a 50-55 degrees contact angle on pAA-g-SR to be further linked with collagen was subsequently obtained. Moreover, the influence of surface properties toward migration, growth and attachment of CE cells on the modified surfaces was also examined. Here, untreated SR was used as a control. Experimental results indicated that the number of CE cells attached onto the controlled SR was negligible. The attachment of cells onto pAA-grafted surfaces was clearly observed and peusopoda occurred; however, cell growth was depressed. This depression may have been caused by the acid environment of the pAA-grafted membrane. Nevertheless, both cell attachment and growth onto collagen-linked surfaces were significant. In addition, the morphology of the cells attached onto this surface was considered normal for primary cells. Collagen introduced on the SR surface was not denatured, i.e the natural properties of collagen were maintained. The results obtained in this study will hopefully lead to the successful development of modified SR for clinical applications.

Long-residence-time nano-scale liposomal iohexol for X-ray-based blood pool imaging.

RATIONALE AND OBJECTIVES Although soluble nonionic iodine compounds with low systemic toxic effects have been developed for use in computed tomography (CT), they have short residence times of a few minutes or mere seconds-insufficient time for blood pool imaging, even with high-speed multi-detector row spiral CT. Moreover, potential renal toxic effects preclude repeated administration of these contrast agents during imaging, as well as their use in patients with compromised renal function. The objective of this study was to develop and evaluate a CT contrast agent for blood pool imaging that remains in the blood for more than 3 hours and that is relatively nontoxic to the kidneys. MATERIALS AND METHODS The authors assessed a liposomal iohexol formulation for its encapsulation efficiency in terms of milligrams of iodine per milliliter of lipid formulation and for its stability in phosphate buffer solution and in human plasma in vitro. Using a rabbit model, they also assessed the formulations in vivo stability, residence time, and enhancement of contrast on images of various organ systems. RESULTS The formulation, which contained 34.8 mg of iodine per milliliter of liposomal iohexol solution, remained stable in blood plasma both in vitro and in vivo, after injection into rabbit vasculature. An intravenous dose of 475 mg of iodine per kilogram of body weight produced contrast enhancement in the rabbit model of approximately 130 HU in the aorta and liver cortex and approximately 100 HU in the kidney cortex. Contrast enhancement was maintained for 3 hours after injection, and minimal clearance of the contrast agent via the kidneys was observed. CONCLUSION The liposomal iohexol formulation tested in this study had a sufficient residence time for blood pool imaging in a rabbit model. Future experiments with long-residence-time iohexol formulations may lead eventually to applications in cardiac imaging and in early tumor detection.

Artificial cornea: surface modification of silicone rubber membrane by graft polymerization of pHEMA via glow discharge.

A method for producing various surfaces of silicone rubber membrane (SR) was developed in this study by grafting various amounts of poly(2-hydroxy ethyl methacrylate) (pHEMA) onto SR by plasma-induced grafted polymerization (PIP) as a homobifunctional membrane. The elemental composition and different carbon bindings on the surface of SR were examined by electron spectroscopy for chemical analysis with the amount of O1s/C1s being approximately 0.7 at 1 min, 60 W, 200 mTorr of Ar-plasma treatment. The peroxide group introduced on SR was measured via 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the amount of 6.85 x 10(-8) mol cm-2 reached optimum value at 1 min of Ar-plasma treatment. After Ar-plasma treated SR, the peroxide group (33D peak) was introduced on the surface of SR by negative spectra of secondary ion mass spectroscopy analysis, whereas ester groups (72D peak) were observed for pHEMA-grafted SR. For the in vitro test, the influence of various surfaces of SR on attachment and growth of rabbit corneal epithelial cells (CEC) was studied by cell culture assay. These results indicated that 56-150 micrograms cm-2 of pHEMA grafted onto SR were suitable values for attachment and growth of CEC. On the contrary, the large grafted amounts (500-1650 micrograms cm-2) of pHEMA on SR were insufficient for attachment and growth of CEC. For the in vivo test, the migration of CEC from host cornea to implant was investigated by slit lamp microscopy. The experimental results indicated that SRs grafted with pHEMA were completely covered with CEC 3 weeks after implantation of the membranes into the host cornea. These results provide a valuable reference for developing an artificial cornea.

Surface characterization and biological properties study of silicone rubber membrane grafted with phospholipid as biomaterial via plasma induced graft copolymerization

Poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) was grafted onto the surface of a silicon rubber (SR) membrane (pMPC-SR) by plasma induced grafted copolymerization (PIP). Argon plasma was used to activate the SR surfaces. Determination was also made of the influences of grafted copolymerization reaction time, reaction temperature, and monomer concentration on polymerization yield. The surface properties of SR were characterized by ATR-FTIR, ESCA, and SEM. In those analyses the ATR-FTIR spectra indicated that the pMPC grafted onto the SR surface at 1720 and 3300 cm(-1). The elemental composition and different carbon bindings on the surface of the SR were examined by ESCA. An increasing P1s/C1s value g was obtained in the grafted polymerization yield with a concentration of 0.05-0.5M of MPC in the isolated ethanol solution. The surface morphologies of pMPC-SR differed more than those of control and Ar plasma treated surfaces. The difference could have been caused by the homogeneous graft polymerization of pMPC onto the SR membrane. In the biological analyses, protein adsorption on pMPC-SR surfaces was reduced. The reduced level increased with an increase in the pMPC grafted amount. The epithelial cell attachment and growth onto these samples were suppressed. The blood compatibility for a series of pMPC-SR surfaces was examined by platelet adhesion. Blood platelet morphologies in contact with the high ratio of pMPC-SR surfaces were maintained, meaning that in this case the release reaction for platelets never occurred. Consequently, the high amount of pMPC-SR surface had excellent blood compatibility, further suggesting that prevention of adhesion, activation of platelets, and adsorption of blood protein could be achieved.

Preparation and characterization of a homobifunctional silicone rubber membrane grafted with acrylic acid via plasma‐induced graft copolymerization

Polyacrylic acid (PAA) was grafted onto the surface of silicone rubber membrane (SR) by plasma-induced graft copolymerization (PIP). Ar-plasma was used to activate the surface of SR. Also, a determination was made of the influences of plasma treatment power, pressure, time, grafted copolymerization reaction time, and monomer concentration on polymerization yield. The surface properties of SR were measured by ATR-FTIR, ESCA, and SIMS. In those analyses, the elemental composition and different carbon bindings on the surface of SR were examined by ESCA with the amount of O1s/C1s being approximately 0.7 at 60 s by Ar-plasma treatment (60 W, 200 mtorr). The peroxide group introduced on SR was measured via 1,1-diphenyl-2-picryhydrazyl (DPPH). The optimum amount of peroxide groups was 6.85 × 10−8 mol/cm2 at 60 s of Ar-plasma treatment. The peroxide group (33D peak) was introduced onto the surface of SR by negative spectra of SIMS analysis after SR treatment by Ar-plasma. An increase was obtained in grafted polymerization yield with a region of 5 to 50% (v/v) of acrylic acid aqueous solution. Both sites of polyacrylic acid were detected after staining by toluidine blue O. That is, a homobifunctional membrane was developed via this surface modification method.

Solid polymeric microparticles enhance the delivery of siRNA to macrophages in vivo.

Therapeutics based on small interfering RNA (siRNA) have a great clinical potential; however, delivery problems have limited their clinical efficacy, and new siRNA delivery vehicles are greatly needed. In this report, we demonstrate that submicron particles (800–900 nm) composed of the polyketal PK3 and chloroquine, termed as the PKCNs, can deliver tumor necrosis factor-α (TNF-α) siRNA in vivo to Kupffer cells efficiently and inhibit gene expression in the liver at concentrations as low as 3.5 μg/kg. The high delivery efficiency of the PKCNs arises from the unique properties of PK3, which can protect siRNA from serum nucleases, stimulate cell uptake and trigger a colloid osmotic disruption of the phagosome and release encapsulated siRNA into the cell cytoplasm. We anticipate numerous applications of the PKCNs for siRNA delivery to macrophages, given their high delivery efficiency, and the central role of macrophages in causing diseases such as hepatitis, liver cirrhosis and chronic renal disease.

Novel Biomaterials as Artificial Cornea via Plasma Induced Grafted Polymerization

The primary objective of this study is to prepare a highly biocompatible polymer membrane by surface modification and to further develop an artificial cornea. Novel heterobifunctional membranes prepared by grafting different functional polymers onto silicone rubber membranes were achieved. In this work, we report preparation and surface characterization of the heterobifunctional membranes, and their biological analysis (in vitro and in vivo studies). Based on the biological analysis, the heterobifunctional membrane exhibits high potential to be used as artificial cornea.