Organic Compound with Potential for X-ray Imaging Applications

A radiopaque compound, namely, 4,4-bis(4-hydroxy-3,5-diiodophenyl)pentanoic acid, was synthesized by the electrophilic aromatic iodination of 4,4-bis(4-hydroxyphenyl)pentanoic acid using sodium iodide and sodium hypochlorite. The active iodines created by hypochlorite were selectively bound to the ortho positions of the diphenolic acid and obtained a tetraiodo compound. Characterization of this iodinated compound was accomplished by routine methods such as Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (NMR) spectroscopy, energy-dispersive X-ray spectroscopy, mass spectroscopy, UV-Vis spectroscopy, and thermogravimetry. The iodine content in the compound was as high as 64% by weight and therefore expected to possess substantial radiopacity. A 5% solution of the compound in dimethyl sulfoxide exhibited radiopacity of 885 ± 7 Hounsfield Units when tested with computed tomography (CT) scanner. In vitro cytotoxicity test performed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated that the compound was noncytotoxic to L929 fibroblast cells up to the level of 0.8 mg/mL concentration. Overall results indicate that this highly radiopaque compound has the potential to be used for X-ray imaging in the clinical scenario.

X-ray visible and doxorubicin-loaded beads based on inherently radiopaque poly(lactic acid)-polyurethane for chemoembolization therapy

The aim of current study was to develop drug-loaded polymeric beads with intrinsic X-ray visibility as embolic agents, targeting for noninvasive intraoperative location and postoperative examination during chemoembolization therapy. To endow polymer with inherent radiopacity, 4,4'-isopropylidinedi-(2,6-diiodophenol) (IBPA) was firstly synthesized and employed as a contrast agent, and then a set of radiopaque iodinated poly(lactic acid)-polyurethanes (I-PLAUs) via chain extender method were synthesized and characterized. These I-PLAU copolymers possessed sufficient radiopacity, in vitro non-cytotoxicity with human adipose-derived stem cells, and in vivo biocompatibility and degradability in rabbit model via intramuscular implantation. Doxorubicin (DOX), as a chemotherapeutic agent, was further incorporated into I-PLAU beads via a double emulsification (W/O/W) method. For drug release, two ratios of DOX-loaded I-PLAU beads exhibited calibrated size (200-550μm), porous internal structure, good X-ray visibility, evenly drug loading as well as tunable drug release. A preliminary test on in vitro tumor cell toxicity demonstrated that the DOX-loaded I-PLAU beads performed efficient anti-tumor effect. This study highlights novel X-ray visible drug-loaded I-PLAU beads used as promising embolic agents for non-invasive in situ X-ray tracking and efficient chemotherapy, which could bring opportunities to the next generation of multifunctional embolic agents.

Intrinsically radiopaque polyurethanes with chain extender 4,4'-isopropylidenebis [2-(2,6-diiodophenoxy)ethanol] for biomedical applications

Radiopaque polyurethanes are used for medical applications as it allows post-operative assessment of the biomaterial devices using X-ray. Inherently, radiopaque polyurethanes based on polytetramethylene glycol (PTMG), polypropylene glycol, 4,4'-methylenebis(phenyl isocyanate), and a new iodinated chain extender 4,4'-isopropylidenebis[2-(2,6-diiodophenoxy)ethanol] with flexible spacers were synthesized and characterized. The iodinated polyurethanes were clear, optically transparent, and had high molecular weights. The polyurethanes also possessed excellent radiopacity and high thermal stability. The biocompatibility of the most promising iodinated polyurethane was evaluated both in vitro (cytotoxicity evaluation by direct contact and MTT assay, using L929 mouse fibroblast cells) and in vivo (toxicology studies in rabbits and subcutaneous implantation in rats). The material was nontoxic and well tolerated by the animals. Thus, these radiopaque and transparent polyurethanes are expected to have potential for various biomedical applications.

Biodegradable radiopaque iodinated poly(ester urethane)s containing poly(ε-caprolactone) blocks: synthesis, characterization, and biocompatibility

Biodegradable radiopaque iodinated poly(ester-urethane) (I-PU), consisting of poly(ε-caprolactone) (PCL) diol and iodinated bisphenol A (IBPA), has been successfully synthesized via a coupling reaction of PCL-diisocyanate and IBPA with varying compositions. The IBPA with four iodine atoms per molecule was applied as a chain extender to endow the I-PUs with intrinsic X-ray visibility. The chemical structure and molecular weights of I-PUs were characterized by Fourier transform infrared spectroscopy (FT-IR), proton-nuclear magnetic resonance, and gel permeation chromatography (GPC). The effects of IBPA on the physical properties of I-PUs were systematically studied by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and wide-angle X-ray diffraction (WAXD). The DSC results showed that the crystallization of PCL segments in I-PUs was restrained with increasing amount of IBPA, which was also confirmed by WAXD. In the X-radiography analysis, all the synthesized I-PUs exhibited high radiopacity compared with an aluminum wedge of equivalent thickness. Enzymatic degradation tests showed that the incorporation of IBPA prolonged the degradation of I-PUs and distinct mass loss and degradation happened in the third month. Basic cytocompatibility conducted using rat adipose-derived cells proved that all the I-PUs and their biodegradation products were nontoxic. The radiopaque I-PUs is expected to possess a significant advantage over the traditional polymer counterparts in some related biomedical fields.