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To evaluate the performance of a prototype flexible transbronchial cryoprobe compared with that of percutaneous transthoracic cryoablation and to define cone-beam computed tomography (CT) imaging and pathology cryolesion features in an in vivo swine model. Transbronchial cryoablation was performed with a prototype flexible cryoprobe (3 central and 3 peripheral lung ablations in 3 swine) and compared with transthoracic cryoablation performed with a commercially available rigid cryoprobe (2 peripheral lung ablations in 1 swine). Procedural time and cryoablation success rates for endobronchial navigation and cryoneedle deployment were measured. Intraoperative cone-beam CT imaging features of cryolesions were characterized and correlated with gross pathology and hematoxylin and eosin–stained sections of the explanted cryolesions. The flexible cryoprobe was successfully navigated and delivered to each target through a steerable guiding sheath (6/6). At 4 minutes after ablation, 5 of 6 transbronchial and 2 of 2 transthoracic cryolesions were visible on cone-beam CT. The volumes on cone-beam CT images were 55.5 cm3 (SE ± 8.0) for central transbronchial ablations (n = 2), 72.5 cm3 (SE ± 8.1) for peripheral transbronchial ablations (n = 3), and 79.5 cm3 (SE ±11.6) for peripheral transthoracic ablations (n = 2). Pneumothorax developed in 1 animal after transbronchial ablation and during ablation in the transthoracic cryoablation. Images of cryoablation zones on cone-beam CT correlated well with the matched gross pathology and histopathology sections of the cryolesions. Transbronchial cryoablation with a flexible cryoprobe, delivered through a steerable guiding sheath, is feasible. Transbronchial cryoablation zones are imageable with cone-beam CT, with gross pathology and histopathology similar to those of transthoracic cryoablation. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose: To determine the true distribution of radiopaque beads (ROBs) after hepatic embolization in swine as imaged by micro-computed tomography (microCT) compared with in vivo cone-beam computerized tomography (CT) imaged at different kVp settings.Materials and Methods: Swine (n = 3) underwent hepatic transarterial embolization (n = 6) with the use of 70-150-μm ROBs under fluoroscopic guidance. After stasis, in vivo cone-beam CT was performed at 120, 100, and 80 kVp. The animal was euthanized, the liver resected, and microCT with 17 μm resolution performed on embolized tissue samples. The resulting cone-beam CT and microCT data were segmented and registered. Total vessel length, minimum volume-enclosing ellipsoid (MVEE), and number of independent volumes were measured. Maximum-intensity projections (MIPs) were generated for each cone-beam CT.Results: Metrics for all cone-beam CT segmentations differed significantly from microCT segmentations. Segmentations at 80 kVp presented significantly greater vessel length, MVEE, and number of independent volumes compared with 100 kVp and 120 kVp. In addition, 100 kVp segmentations presented significantly greater vessel length than 120 kVp. MIPs presented greater visualization than cone-beam CT segmentations and improved as kVp decreased.Conclusions: The full ROB distribution was more extensive than was apparent on cone-beam CT. Quantitative measures of embolic distribution demonstrated significantly better correlation with microCT with decreasing kVp. Similarly, qualitative analysis of MIPs showed improved visualization of beads with decreasing kVp. These findings demonstrate the clinical value of 80 kVp and 100 kVp protocols in the imaging of radiopaque embolizations compared with 120 kVp. However, considerations on X-ray penetration and dose may favor use of 100 kVp imaging over 80 kVp. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate LC Bead LUMI™ (40–90 µm and 70–150 µm) in order to determine if their increased resistance to compression influences microsphere penetration and distribution compared to more compressible commercial microspheres. LC Bead LUMI™ 40–90 µm and 70–150 µm, LC Bead M1 ® 70–150 µm, Embozene™ 40 µm and Embozene™ 100 µm size and distributions were measured using optical microscopy. Penetration in vitro was evaluated using an established ‘plate model’, consisting of a calibrated tapered gap between a glass plate and plastic housing to allow visual observation of microsphere penetration depth. Behaviour in vivo was assessed using a rabbit renal embolization model with histopathologic confirmation of vessel penetration depth. Penetration behaviour in vitro was reproducible and commensurate with the measured microsphere size, the smaller the microsphere the deeper the penetration. Comparison of the microsphere diameter measured on the 2D plate model versus the corresponding average microsphere size measured by histopathology in the kidney showed no significant differences ( p = > 0.05 Mann-Whitney, demonstrating good in vitro - in vivo predictive capabilities of the plate model) confirming predictable performance for LC Bead LUMI™ (40–90 µm and 70–150 µm) based on microsphere size, their increased rigidity having no bearing on their depth of penetration and distribution. An assessment of a LC Bead LUMI™ (40–90 µm and 70–150 µm) has shown that despite having greater resistance to compression, these microspheres behave in a predictable manner within in vitro and in vivo models comparable with more compressible microspheres of similar sizes. [ABSTRACT FROM AUTHOR]

Hydrogel microspheres with the capability to interact with charged species such as various drugs by ion-exchange processes are useful in a variety of biomedical applications. Such systems have been developed to allow active loading of the microsphere with chemotherapeutic agents in the hospital pharmacy for subsequent locoregional therapy of tumours in the liver by drug-eluting bead chemoembolization (DEB-TACE). A variety of microspherical embolisation systems have been described, all based upon hydrogels bearing anionic functionalities to allow interaction with cationically charged drugs. We have recently prepared a series of microspheres bearing cationic functionality and have observed some unusual behaviour induced by phase-separation that occurs during the synthesis of the microspheres. The phase-separation results in the core of the microsphere being enriched in cationic polymer component compared to the outer polyvinyl alcohol (PVA)-based phase. For certain formulations, subsequent swelling in water results in the PVA-rich skins separating from the charged cores. Ion-exchange interactions with model compounds bearing multi-anionic groups create differential contraction of the charged core relative to the skin, resulting in an unusual “golf-ball” appearance to the surface of the microspheres. Statement of Significance The authors believe that the unusual behaviour of the microspheres reported in this paper is the first observation of its kind resulting from phase-separation during synthesis. This could have novel applications in drug delivery for systems that can respond by shedding their skin or altering the surface area to volume ratio upon loading a drug. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of embolic diameter on achievement of hypoxia after embolization in an animal model of liver tumors.Materials and Methods: Inoculation of VX2 tumors in the left liver lobe was performed successfully in 12 New Zealand white rabbits weighing 3.7 kg ± 0.5 (mean ± SD). Tumors were deemed eligible for oxygen measurements when the maximum transverse diameter measured 15 mm or more by ultrasound examination. Direct monitoring of oxygenation of implanted rabbit hepatic VX2 tumors was performed with a fiberoptic electrode during and after transarterial embolization of the proper hepatic artery to angiographic flow stasis with microspheres measuring 70-150 μm, 100-300 μm, or 300-500 μm in diameter.Results: Failure to achieve tumor hypoxia as defined despite angiographic flow stasis was observed in 10 of 11 animals. Embolization microsphere size effect failed to demonstrate a significant trend on hypoxia outcome among the diameters tested, and pair-wise comparisons of different embolic diameter treatment groups showed no difference in hypoxia outcome. All microsphere diameters tested resulted in similar absolute reduction (24.3 mm Hg ± 18.3, 29.1 mm Hg ± 1.8, and 19.9 mm Hg ± 9.3, P = .66) and percentage decrease in oxygen (56.0 mm Hg ± 23.9, 56.0 mm Hg ± 6.4, and 35.8 mm Hg ± 20.6, P = .65). Pair-wise comparisons for percent tumor area occupied by embolic agents showed a significantly reduced fraction for 300-500 μm diameters compared with 70-150 μm diameters (P < .05).Conclusions: In the rabbit VX2 liver tumor model, three tested microsphere diameters failed to cause tumor hypoxia as measured by a fiberoptic probe sensor according to the adopted hypoxia definitions. [ABSTRACT FROM AUTHOR]

Purpose: To develop and characterize radiopaque embolization microspheres capable of in vivo detection with intraprocedural fluoroscopy and computed tomography (CT) imaging and to evaluate their spatial distribution inside target tissues during and after transcatheter embolization. Materials and Methods: Polyvinyl alcohol hydrogel microspheres were loaded with Lipiodol and examined for iodine content, stability of loading, and conspicuity with fluoroscopy and CT in vitro. Transcatheter embolization of swine liver and kidney was performed with the radiopaque microspheres and spatial distribution was evaluated with intraprocedural fluoroscopy and CT. Ex vivo evaluation was performed with light microscopy and micro-CT. Results: In vitro analyses demonstrated that radiopaque microspheres could be loaded with sufficient iodine content to be detected with routine fluoroscopy and CT imaging and that such loading was relatively stable. Radiopaque microspheres were visible in vivo with fluoroscopy and CT during transcatheter embolization. CT imaging during embolization procedures demonstrated a dose-dependent relationship in the number and size of visualized embolized arteries. Imaging features of radiopaque microsphere distribution inside target tissues correlated well with ex vivo light microscopic and micro-CT evaluation of microsphere distribution. Conclusions: Radiopaque embolization microspheres are visualized during transcatheter embolization with routine intraprocedural fluoroscopy and CT. These radiopaque microspheres provided the three-dimensional spatial distribution of embolic material inside target organs during the procedure, and therefore can provide real-time intraprocedural feedback for the interventional radiologist. These microspheres may be useful for demonstrating the influence of material and technical variability in transcatheter embolization in addition to providing intraprocedural identification of tissue at risk of undertreatment. [Copyright &y& Elsevier]

Purpose: To evaluate the local tissue concentrations of the antineoplastic agent doxorubicin and the amount of drug still present inside drug delivery embolization beads at different time points after embolization and to compare doxorubicin levels with histologic modifications around the beads in a pig liver model. It was hypothesized that doxorubicin-eluting beads maintain cytotoxic concentrations of drug locally over a period of several weeks, as suggested by in vitro elution tests. Materials and Methods: Left lobe hepatic artery embolization was performed in 10 pigs with 100–300-μm or 700–900-μm beads loaded with 37.5 mg doxorubicin/mL. Control unloaded 100–300-μm beads were injected in five pigs. Livers were sampled 28 days or 90 days after embolization. The amount of drug retained inside the beads was assessed with infrared microspectroscopy. Doxorubicin concentration and distribution in the tissue around the beads were determined with microspectrofluorimetry and compared with tissue modifications on hematein eosin saffron–stained sections. Results: Doxorubicin-eluting beads eluted 43% of their initial drug load after 28 days and 89% after 90 days. Doxorubicin was present in tissues around the beads at both time points, with a significant decrease over time (P = .0004). The drug was detected at distances as far as 600 μm from the bead edge. Doxorubicin tissue concentrations ranged from 0.55 M to 6.80 M, which are cytotoxic levels in hepatocyte cell cultures. High concentrations of drug were associated with coagulative necrosis of liver parenchyma. Doxorubicin-eluting beads 100–300 μm in size induced more necrosis than 700–900-μm beads (P = .0036). Conclusions: Doxorubicin-eluting beads deliver high concentrations of the drug over a period of at least 3 months at several hundred micrometers from the bead, leading to significant cytotoxic effects. [Copyright &y& Elsevier]

Purpose: To compare standard embolization microspheres (SMS) with microspheres of very narrow size distribution in terms of physical properties and relative distribution within sheep kidney and uterine artery models of embolization. Materials and Methods: Standard microspheres (SMS; 500–700 μm and 700–900 μm) were compared with narrow microspheres (NMS) of the same material made with a microfluidic method that produced a much narrower size distribution (600 μm and 800 μm). Characterization of both microspheres was performed in vitro (ie, bead size, water content, and compressive modulus). In the sheep model of kidney and uterus embolization, histopathologic analysis was performed to determine the average vessel size occluded, the number of microspheres per vessel, and the deformation in vivo, with a focus on the localization of the products within the different vascular zones of the organ tissues. Results: In vitro testing showed the physical properties of NMS to be similar to those of SMS. SMS and NMS also possessed the same degree of deformation in vivo. In both embolization models, there were no major differences in the localization of SMS compared with NMS of equivalent mean bead diameters. Conclusions: Compared with SMS with a normal distribution in size range, NMS with a narrow size distribution did not exhibit a very different distribution within the vasculature of the sheep kidney or uterus. [Copyright &y& Elsevier]

Abstract: Supercritical CO2 has the potential to be an excellent environment within which controlled release polymers and dry composites may be formed. The low temperature and dry conditions within the fluid offer obvious advantages in the processing of water, solvent or heat labile molecules. The low viscosity and high diffusivity of scCO2 offer the possibility of novel processing routes for polymer drug composites, but there are still technical challenges to overcome. Moreover, the low solubility of most drug molecules in scCO2 presents both challenges and advantages. This review explores the current methods that use high pressure and scCO2 for the production of drug delivery systems and the more specialized application of the fluid in the formation of highly porous tissue engineering scaffolds. [Copyright &y& Elsevier]

PURPOSE: To present the pathologic and pharmacokinetic findings from hepatic embolization in a porcine model comparing doxorubicin-eluting beads with bland embolization and to correlate these findings with in vitro release kinetics. MATERIALS AND METHODS: Drug-eluting beads (DEB; 100–300 μm and 700–900 μm) loaded with 37.5 mg doxorubicin per milliliter hydrated beads were used to embolize the hepatic artery feeding the left lobe of the liver in young adult Yucatan pigs (n = 5 per group). Control animals underwent embolization with bland beads (100–300 m; n = 5). Systemic plasma levels of doxorubicin were measured and correlated to in vitro drug release. Blood sampling and histopathologic examination were performed during the 90-day follow-up. RESULTS: All animals underwent successful embolization, and the treatment was well tolerated. Mean volumes of beads administered were 2.0–3.4 mL, with mean doses of 127.5 mg and 78.7 mg of doxorubicin for the 100- to 300-μm and 700- to 900-μm DEB groups, respectively. Gross pathologic examination revealed no effects on organs other than the liver. There was a transient increase in liver enzyme levels, particularly in the groups of animals who underwent embolization with 100- to 300-μm DEB. Histopathologic study showed mostly nonnecrotic changes with bland beads, whereas the effects of DEB were more severe, with large areas of pannecrosis evident with the 100- to 300-μm DEB. Maximum plasma concentrations were 651 ng/mL and 42.8 ng/mL for the 100- to 300-μm and 700- to 900-μm DEB groups, respectively, observed at 1 minute for both groups. Correlation with in vitro data showed a strong linear relationship. CONCLUSIONS: Hepatic arterial embolization with DEB was shown to be safe and well tolerated. The locoregional delivery of doxorubicin from DEB caused targeted tissue damage with minimal systemic impact and could be a promising new approach to transarterial chemoembolization of solid tumors. [Copyright &y& Elsevier]

PURPOSE: The purpose of this investigation is to present the in vitro characterization and detailed drug-loading procedure for DC Bead, a microsphere product that can be loaded with chemotherapeutic agents for embolization. MATERIALS AND METHODS: DC Bead is an embolic microsphere product that is capable of being loaded with anthracycline drugs such as doxorubicin just before administration in a transarterial chemoembolization (TACE) procedure. Beads can be loaded from solutions prepared from doxorubicin powder or the doxorubicin HCl formulation. In this evaluation, bead sizes were measured by optical microscopy with video imaging. Gravimetric analysis demonstrated the effect of drug loading on bead water content, and its consequent impact on bead compressibility was determined. The subsequent deliverability of the beads was assessed by mixing the beads with contrast medium and saline solution and passing the beads through an appropriately sized microcatheter. A T-cell apparatus was used to monitor the in vitro elution of the drug from the beads over a period of 24 hours in various elution media. RESULTS: DC Bead spheres could be easily loaded with doxorubicin to a recommended level of 25 mg/mL of hydrated beads by immersion of the beads in the drug solution for 10–120 minutes depending on microsphere size. Other commercial embolic microspheres were shown not to load doxorubicin to the same extent or release it in the same fashion and were considered unsuitable for local drug delivery. Maximum theoretic capacity for DC Bead was approximately 45 mg/mL. Increase in doxorubicin loading resulted in a concomitant decrease in water content and consequential increase in bead resistance to compression force. Drug loading also resulted in a decrease in the average size of the beads, which was dependent on bead size and drug dose. This did not impact bead delivery at any drug loading level to a maximum of 37.5 mg/mL. Beads 100–700 μm in size could be delivered through 2.7-F microcatheters, whereas the 700–900-μm range required 3-F catheters. Modeling of the kinetics of drug elution from the beads in vitro at a loading dose of 25 mg/mL yielded calculated half-lives of 150 hours for the 100–300-μm range to a maximum of 1,730 hours for the 700–900-μm size range, which was dependent on the ionic strength of the elution medium. For comparison, there was a rapid loss of drug from an unstable Lipiodol emulsion with a half-life of approximately 1 hour. CONCLUSIONS: DC Bead can be loaded with doxorubicin to provide an accurate dosage of drug per unit volume of beads. Drug elution is dependent on ion exchange with the surrounding environment and is controlled and sustained, unlike the rapid separation of the drug from Lipiodol. Drug loading has no impact on the handling and deliverability of the beads, making them suitable for superselective TACE. [Copyright &y& Elsevier]

Phosphorylcholine (PC)-based polymers have been used in a variety of medical device applications to improve biocompatibility. The use of PC-based materials for biomaterials is associated with low protein adsorption, reduced complement activation, low inflammatory response and cell adhesion. For some medical device applications however, materials that support cell adhesion are also beneficial, allowing host interaction and encouraging full incorporation within the body. As previous studies have suggested that cell adhesion to materials is enhanced by the addition of charge, PC-based polymers have therefore been modified to incorporate various concentrations of cationic charge. In this study, the affect of cationic charge on a range of biological responses was investigated. In vitro assays have been used to assess the adsorption of protein onto the materials surface, the adhesion of mouse fibroblasts and rabbit corneal epithelial cells and the adhesion of human mononuclear cells and granulocytes. The results corroborate previous work showing that PC without charge significantly reduces protein adsorption, cell adhesion and inflammatory cell activation. The addition of cationic charge to PC polymers however, resulted in an increase in all of the above responses. This increase did not however, increase linearly with cationic monomer concentration. The differences in cell adhesion are discussed in terms of differences in protein adsorption, cytotoxicity and/or stability of the different cationic polymer coatings. [Copyright &y& Elsevier]

Phospholipid-like polymers based on 2-methacryloyloxyethyl phosphorylcholine containing varying amounts of the cationically charged monomer choline methacrylate (CMA) from 0 to 30 wt% have been prepared. Substrates coated with these materials were shown to bind significantly lower amounts of specific proteins compared to the uncoated control. ELISA assays demonstrated that fibrinogen did not bind appreciably to coatings containing 0–30% CMA, whereas albumin binding was seen to increase significantly as the CMA content of the coating increased. Platelet activation assays, measurement of plasma coagulation time and whole blood contact scanning electron micrography demonstrated that the haemocompatibility of the coatings was shown to be unaffected by the CMA component. The CMA polymer coatings have been shown to absorb/adsorb many different drug compounds covering a wide range of molecular weights and release these in a controlled fashion. The range of cationic polymers assessed can interact with the net negative charge found in many large therapeutic biomolecules, such as DNA fragments used in gene therapy, that may be of interest in the preventative treatment of conditions such as restenosis. Coronary stents coated with 6% or 20% CMA-containing polymers have been shown to load and release this type of genetic material irrespective of molecular weight of the biomolecule. Ex vivo and in vivo studies have shown that these compounds can be delivered to the stented section of the vessel with very low quantities delivered outside the vessel target area. [Copyright &y& Elsevier]

Phospholipid-like copolymers based on 2-(methacryloyloxyethyl) phosphorylcholine were synthesised using monomer-starved free radical polymerisation methods and incorporating cationic charge in the form of the choline methacrylate monomer in amounts varying from 0 to 30 wt%, together with a 5 wt% silyl cross-linking agent in order to render them water-insoluble once thermally cured. Characterisation using a variety of techniques including nuclear magnetic resonance spectroscopy, high-pressure liquid chromatography and gel permeation chromatography showed the cationic monomer did not interfere with the polymerisation and that the desired amount of charge had been incorporated. Gravimetric and differential scanning calorimetry methods were used to evaluate the water contents of polymer membranes cured at 70°C, which was seen to increase with increasing cation content, producing materials with water contents ranging from 50% to 98%. Surface plasmon resonance indicated that the coatings swelled rapidly in water, the rate and extent of swelling increasing with increasing cation level. Dynamic contact angle showed that coatings of all the polymers possessed a hydrophobic surface when dry in air, characteristic of the alkyl chains expressed at the surface (>100° advancing angle). Rearrangement of the hydrophilic groups to the surface occurred once wet, to produce highly wettable surfaces with a decrease in advancing angle with increasing cation content. Atomic force microscopy showed all polymer films to be smooth with no features in topographical or phase imaging. Mechanical properties of the dry films were also unaffected by the increase in cation content. [Copyright &y& Elsevier]

Purpose: To investigate material density, flow, and viscosity effects on microsphere distribution within an in vitro model designed to simulate hepatic arteries.Materials and Methods: A vascular flow model was used to compare distribution of glass and resin surrogates in a clinically derived flow range (60-120 mL/min). Blood-mimicking fluid (BMF) composed of glycerol and water (20%-50% vol/vol) was used to simulate a range of blood viscosities. Microsphere distribution was quantified gravimetrically, and injectate solution was dyed to enable quantification by UV spectrophotometry. Microsphere injection rate (5-30 mL/min) and the influence of contrast agent dilution of injection solution (0%-60% vol/vol) were also investigated.Results: No significant differences in behavior were observed between the glass and resin surrogate materials under any tested flow conditions (P = .182; n = 144 injections). Microspheres tend to align more consistently with the saline injection solution (r2 = 0.5712; n = 144) compared with total BMF flow distribution (r2 = 0.0104; n = 144). The most predictable injectate distribution (ie, greatest alignment with BMF flow, < 5% variation) was demonstrated with > 10-mL/min injection rates of pure saline solution, although < 20% variation with glass microsphere distribution was observed with injection solution containing as much as 30% contrast medium when injected at > 20 mL/min.Conclusions: Glass and resin yttrium-90 surrogates demonstrated similar distribution in a range of clinically relevant flow conditions, suggesting that microsphere density does not have a significant influence on microsphere distribution. Injection parameters that enhanced the mixing of the spheres with the BMF resulted in the most predictable distribution. [ABSTRACT FROM AUTHOR]

Purpose: To quantify changes in tumor microvascular (< 1 mm) perfusion relative to commonly used angiographic endpoints.Materials and Methods: Rabbit Vx2 liver tumors were embolized with 100-300-μm LC Bead particles to endpoints of substasis or complete stasis (controls were not embolized). Microvascular perfusion was evaluated by delivering two different fluorophore-conjugated perfusion markers (ie, lectins) through the catheter before embolization and 5 min after reaching the desired angiographic endpoint. Tumor microvasculature was labeled with an anti-CD31 antibody and analyzed with fluorescence microscopy for perfusion marker overlap/mismatch. Data were analyzed by analysis of variance and post hoc test (n = 3-5 per group; 18 total).Results: Mean microvascular density was 70 vessels/mm(2) ± 17 (standard error of the mean), and 81% ± 1 of microvasculature (ie, CD31(+) structures) was functionally perfused within viable Vx2 tumor regions. Embolization to the extent of substasis eliminated perfusion in 37% ± 9 of perfused microvessels (P > .05 vs baseline), whereas embolization to the extent of angiographic stasis eliminated perfusion in 56% ± 8 of perfused microvessels. Persistent microvascular perfusion following embolization was predominantly found in the tumor periphery, adjacent to normal tissue. Newly perfused microvasculature was evident following embolization to substasis but not when embolization was performed to complete angiographic stasis.Conclusions: Nearly half of tumor microvasculature remained patent despite embolization to complete angiographic stasis. The observed preservation of tumor microvasculature perfusion with angiographic endpoints of substasis and stasis may have implications for tumor response to embolotherapy. [ABSTRACT FROM AUTHOR]

Purpose: To develop a simple method to produce radiopaque drug-eluting microspheres (drug-eluting beads [DEBs]) that could be incorporated into the current clinical transcatheter arterial chemoembolization workflow and evaluate their performance in vitro and in vivo.Materials and Methods: An ethiodized oil (Lipiodol; Guerbet, Villepinte, France) and ethanol solution was added to a lyophilized 100-300 µm bead before loading with doxorubicin. These radiopaque drug-eluting beads (DEBs; Biocompatibles UK Ltd, Farnham, United Kingdom) were evaluated in vitro for x-ray attenuation, composition, size, drug loading and elution, and correlation between attenuation and doxorubicin concentration. In vivo conspicuity was evaluated in a VX2 tumor model.Results: Lipiodol was loaded into lyophilized beads using two glass syringes and a three-way stopcock. Maximum bead attenuation was achieved within 30 minutes. X-ray attenuation of radiopaque beads increased linearly (21-867 HU) with the amount of beads (0.4-12.5 vol%; R(2) = 0.9989). Doxorubicin loading efficiency and total amount eluted were similar to DC Bead (Biocompatibles UK Ltd); however, the elution rate was slower for radiopaque DEBs (P < .05). Doxorubicin concentration linearly correlated with x-ray attenuation of radiopaque DEBs (R(2) = 0. 99). Radiopaque DEBs were seen in tumor feeding arteries after administration by fluoroscopy, computed tomography, and micro-computed tomography, and their location was confirmed by histology.Conclusions: A simple, rapid method to produce radiopaque DEBs was developed. These radiopaque DEBs provided sufficient conspicuity to be visualized with x-ray imaging techniques. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To determine local doxorubicin levels surrounding radiopaque drug-eluting beads (DEBs) in normal swine liver and kidney following transcatheter arterial chemoembolization. The influence of bead size (70–150 μm or 100–300 μm) was compared with regard to tissue penetration and spatial distribution of the bead, as well as eventual drug coverage (ie, amount of tissue exposed to drug). Materials and Methods: Radiopaque DEBs were synthesized by suspension polymerization followed by incorporation of iodized oil and doxorubicin. Chemoembolization of swine liver and kidney was performed under fluoroscopic guidance. Three-dimensional tissue penetration of “imageable” DEBs was investigated ex vivo with micro–computed tomography (microCT). Drug penetration from the bead surface and drug coverage was evaluated with epifluorescence microscopy, and cellular localization of doxorubicin was evaluated with confocal microscopy. Necrosis was evaluated with hematoxylin and eosin staining. Results: MicroCT demonstrated that 70–150-μm DEBs were present in more distal arteries and located in a more frequent and homogeneous spatial distribution. Tissue penetration of doxorubicin from the bead appeared similar (∼300 μm) for both DEBs, with a maximum tissue drug concentration at 1 hour coinciding with nuclear localization of doxorubicin. The greater spatial frequency of the 70–150-μm DEBs resulted in approximately twofold improved drug coverage in kidney. Cellular death is predominantly observed around the DEBs beginning at 8 hours, but increased at 24 and 168 hours. Conclusions: Smaller DEBs penetrated further into targeted tissue (ie, macroscopic) with a higher spatial density, resulting in greater and more uniform drug coverage (ie, microscopic) in swine. [Copyright &y& Elsevier]

Abstract: Phosphorylcholine (PC) moieties were chemically attached to surfaces of polymer microparticles by addition of 2-methylacryloyloxyethyl phosphorylcholine monomer to the seeded, semi-continuous polymerisations of methyl methacrylate (MMA) and butyl acrylate (BA). The surface of the bio-functionalised polymer microparticles was principally characterised using X-ray photoelectron spectroscopy (XPS), dynamic nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), photon correlation spectroscopy (PCS), acoustophoresis and enzyme-linked immunosorbent assays (ELISA). It was found that the persulphate initiating species are concealed behind the phosphorylcholine containing monomer sequence located on the surface of the microparticles. The combination of analytical techniques showed that the surfaces of the polymer microparticles are extremely mobile above the glass transition temperature of the co-polymer and able to rearrange depending on the environment in which they are placed. This allows the phosphorylcholine moiety to be preferentially expressed at the surface in aqueous media, but not so in the dry state or conditions of ultra-high vacuum. In terms of the nature of the biocompatibility of phosphorylcholine containing polymers, no evidence was found for the irreversible structuring of water molecules around the phosphorylcholine moiety in the wet state. The results of this work suggest that a more likely contributory reason for the protein-resistant nature of phosphorylcholine containing polymers is the mobility of the phosphorylcholine moiety. Increases in biocompatibility correspond with increases in the hydrophilicity of a polymer surface when phosphorylcholine is preferentially expressed. A large free water fraction may be present in the phosphorylcholine containing monomer sequence, as part of a hydrogel structure located at the surface of the polymer microparticles. This, coupled with concomitant modification of the local electrical double-layer very close to the surface may also play a critical role in reducing protein–surface interactions. [Copyright &y& Elsevier]

Abstract Isothermal titration calorimetry was used to investigate thermodynamic and kinetic binding interactions between 4 clinically relevant drugs: doxorubicin (Dox), irinotecan (Iri), mitoxantrone (Mitox), and topotecan (Topo) and a range of commercially available embolization microspheres. Five drug-eluting beads were chosen to consider the effect of bead size (ranging from 70-150 μm to 500-700 μm) and bead type (sulfonate-modified polyvinylalcohol hydrogel, known commercially as DC Bead M1 ™, and a sulfonate-modified polyethylene glycol hydrogel bead, known commercially as LifePearl™). The molar ratio of drug to SO 3 − was found to be 0.9:1, 0.8:1, 0.4:1, and 0.9:1 for Dox, Iri, Mitox, and Topo, respectively. These findings indicate the steric effects of drug shape, charge, and size on binding ability. Four distinct bead sizes all produced drug:bead binding ratios of >0.9:1 doxorubicin:SO 3 −, thus indicating that bead size does not affect binding stoichiometry. Interestingly, bead size did affect the rate of binding as bead size was found to be indirectly proportional to binding rate. Finally, it was found for the sulfonate-modified polyethylene glycol hydrogel beads that doxorubicin binding was faster (at certain ratios of drug to bead) than that for the sulfonate-modified polyvinylalcohol hydrogel yet was maximal at a drug to bead ratio of only 0.7:1. [ABSTRACT FROM AUTHOR]

Osteoporosis treatment with PTH 1–34 injections significantly reduces the incidence of bone fracture. Potential further reductions in fracture rate should be observed through nasal spray delivery to address the poor compliance associated with patient dislike of repeated PTH 1–34 subcutaneous injections. In vitro human osteoblast-like Saos-2 cell intracellular cAMP levels were used to define PTH 1–34 nasal spray formulation bioactivity. The chemically synthesised PTH 1–34 had an EC 50 of 0.76 nM. Absorption enhancers polyethylene glycol (15)-hydroxystearate (Solutol ® HS15), poloxamer 407, chitosan or sodium hyaluronate did not diminish the bioactivity of PTH 1–34 within an in vitro cell culture model (p > 0.05). We also demonstrated the effectiveness of the transmucosal absorption enhancer Solutol ® HS15 in a nasal spray formulation using a preclinical pharmacokinetic model. In Sprague-Dawley rats without the absorption enhancer the uptake of PTH 1–34 into the blood via intranasal delivery produced a Cmax of 2.1 ± 0.5 ng/ml compared to 13.7 ± 1.6 ng/ml with Solutol ® HS15 enhancer (p = 0.016) and a Cmax14.8 ± 8 ng/ml in subcutaneous injections. Together these data illustrate that the nasal spray formulation bioactivity in vitro is not affected by the nasal spray absorption enhancers investigated, and the Solutol ® HS15 nasal spray formulation had an equivalent pharmacokinetic profile to subcutaneous injection in the rat model. The Solutol ® HS15 formulation therefore demonstrated potential as a PTH 1–34 nasal spray formulation for the treatment of osteoporosis. [ABSTRACT FROM AUTHOR]

Drug release from chemoembolization microspheres stimulated by the presence of a chemically reducing environment may provide benefits for targeting drug resistant and metastatic hypoxic tumours. A water-soluble disulfide-based bifunctional cross-linker bis(acryloyl)-(l)-cystine (BALC) was synthesised, characterised and incorporated into a modified poly(vinyl) alcohol (PVA) hydrogel beads at varying concentrations using reverse suspension polymerisation. The beads were characterised to confirm the amount of cross-linker within each formulation and its effects on the bead properties. Elemental and UV/visible spectroscopic analysis confirmed the incorporation of BALC within the beads and sizing studies showed that in the presence of a reducing agent, all bead formulations increased in mean diameter. The BALC beads could be loaded with doxorubicin hydrochloride and amounts in excess of 300 mg of drug per mL of hydrated beads could be achieved but required conversion of the carboxylic acid groups of the BALC to their sodium carboxylate salt forms. Elution of doxorubicin from the beads demonstrated a controlled release via ionic exchange. Some formulations exhibited an increase in size and release of drug in the presence of a reducing agent, and therefore demonstrated the ability to respond to an in vitro reducing environment. [ABSTRACT FROM AUTHOR]

The diffusion of a polyzwitterion, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), in aqueous solution containing different alkali halides was studied by fluorescence correlation spectroscopy at single molecule level. It was found that the halide anion has a greater effect on the radius of zwitterionic PMPC molecules than alkali cations, which is due to the mechanism by which PMPC molecules interact with the surrounding hydrogen bond network of water molecules and adsorbed ions. With the addition of salt, the size of PMPC remains constant while its diffusion coefficient is reduced slightly, although larger cations (e.g. K + ) result in slightly increased diffusion coefficient for 1 M potassium chloride-based solutions. This enhanced diffusion coefficient is attributed to the decrease in the viscosity of the aqueous solution on the addition of salt. When the counter-ion was varied in potassium-based salts, different effects were observed for different anions, resulting a reduction in the diffusion coefficient as a function of salt concentration. This reduction was modest for KBr, but significant for KI. Overall, no discernible changes were observed as the size of the PMPC coil was varied, except in case of KI for which a significant increase was observed at higher ionic strength. Divalent cations (Ca 2+ and Mg 2+ ), produced similar effects to those found for monovalent cations. These effects are explained by the interaction of PMPC with the hydrogen bond network of water molecules and with the adsorbed ions. [ABSTRACT FROM AUTHOR]

The objective of this study was to undertake a comprehensive long-term biocompatibility and imaging assessment of a new intrinsically radiopaque bead (LC Bead LUMI™) for use in transarterial embolization. The sterilized device and its extracts were subjected to the raft of ISO10993 biocompatibility tests that demonstrated safety with respect to cytotoxicity, mutagenicity, blood contact, irritation, sensitization, systemic toxicity and tissue reaction. Intra-arterial administration was performed in a swine model of hepatic arterial embolization in which 0.22–1 mL of sedimented bead volume was administered to the targeted lobe(s) of the liver. The beads could be visualized during the embolization procedure with fluoroscopy, DSA and single X-ray snapshot imaging modalities. CT imaging was performed before and 1 h after embolization and then again at 7, 14, 30 and 90 days. LC Bead LUMI™ could be clearly visualized in the hepatic arteries with or without administration of IV contrast and appeared more dense than soluble contrast agent. The CT density of the beads did not deteriorate during the 90 day evaluation period. The beads embolized predictably and effectively, resulting in areas devoid of contrast enhancement on CT imaging suggesting ischaemia-induced necrosis nearby the sites of occlusion. Instances of off target embolization were easily detected on imaging and confirmed pathologically. Histopathology revealed a classic foreign body response at 14 days, which resolved over time leading to fibrosis and eventual integration of the beads into the tissue, demonstrating excellent long-term tissue compatibility. [ABSTRACT FROM AUTHOR]

[Display omitted] Cancer immunotherapy has yet to reach its full potential due in part to limited response rates and side effects inherent to systemic delivery of immune-modulating drugs. Local administration of immunotherapy using drug-eluting embolic (DEE) microspheres as drug delivery vehicles for direct infusion into tumor-feeding arteries might increase and prolong tumor drug concentrations and reduce systemic drug exposure, potentially improving the risk-to-benefit ratio of these agents. The purpose of this study was to evaluate the ability of four immune modulators affecting two different immune pathways to potentiate replication of immune cells from a woodchuck model of hepatocellular carcinoma. DSR 6434, a Toll-like receptor agonist, and BMS-202, a PD-L1 checkpoint inhibitor, induced immune cell replication and were successfully loaded into radiopaque DEE microspheres in high concentrations. Release of DSR 6434 from the DEE microspheres was rapid (t 99% = 0.4 h) upon submersion in a physiologic saline solution while BMS-202 demonstrated a more sustained release profile (t 99% = 17.9 h). These findings demonstrate the feasibility of controlled delivery of immune-modulating drugs via a local DEE microsphere delivery paradigm. [ABSTRACT FROM AUTHOR]

The instability of human growth hormone (hGH) to temperature and interfaces makes its formulation into injectable, sustained-release drug delivery systems challenging. A novel method of encapsulating hGH in polymeric microparticles has been developed using supercritical CO2(scCO2) technology, but there is limited understanding of the stability of hGH within this system. The aim of this study was to evaluate the stability of hGH in scCO2 processing. The integrity of the protein was assessed following exposure to scCO2 using a range of different analytical techniques. Mass spectrometry showed that no peptide cleavage occurred as a result of processing or exposure to scCO2. Size-exclusion chromatography detected formation of aggregates at high temperatures, but not as a result of the encapsulation process. Reverse-phase chromatography demonstrated that the production of deamidation products occurred as a function of temperature, but only at temperatures higher than those used for the encapsulation process. Circular dichroism and infrared spectroscopy demonstrated that the use of scCO2 was not detrimental to the secondary molecular structure of hGH. Together, these results show that the structural integrity of hGH is unaffected by scCO2 processing and that hGH can be successfully encapsulated in polymer microparticles using this technique. © 2011 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:56-67, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Drug eluting beads that release irinotecan in a controlled manner may be useful for application in the chemoembolization of colorectal cancer metastases to the liver. In this study, irinotecan drug eluting beads were prepared with loadings up to 50mg drug/mL hydrated beads. Drug loading was via an ion-exchange mechanism with sulfonate binding sites in the bead. Release in vitro was shown to be sustained and dependent upon the presence of ions in the elution medium, drug loading and bead size. Drug elution in PBS was controlled by solute diffusion within the beads and gave rise to values for the diffusion coefficient, D, of between 2.4×10−9and 1.4×10−7 cm2 s−1. The beads were shown to decrease in size (by a maximum 25–30%), and concomitantly their modulus of compression increased (from ∼27kPa to a maximum of about 49kPa), with increasing drug loading. This did not however, influence their ability to be suspended homogeneously in contrast agent or delivered through a microcatheter. Following porcine hepatic artery embolization, maximum plasma levels were 70–75% lower for both irinotecan and SN-38 compared to intraarterial bolus administration, with peak levels observed at 2 and 5min after completion of the embolization procedure. The in vivo data were shown to correlate well with the in vitro release measured using a T-apparatus model of embolization. [Copyright &y& Elsevier]

Abstract: A variable temperature ATR–FTIR study of the gelation behaviour of a thermo-responsive ABA triblock copolymer (A=poly(N-isopropylacrylamide) and B=poly[2-(methacryloyloxy)ethyl phosphorylcholine]) is reported. Close inspection of selected copolymer and water bands in the temperature resolved spectra provides evidence for the dehydration of the poly(N-isopropylacrylamide) chains above a critical gelation temperature of approximately 37°C, while the central poly[2-(methacryoyloxy)ethyl phosphorylcholine]) chains remain hydrated. A blue shift in the amide I peak and a red shift in the amide II band indicate a reduction in the hydrogen bonding between the PNIPAM amide functional group and the solvent water. This is corroborated by a decrease in the intensity of the amide I peak above the gel point. Evidence of hydrophobic interactions and an indication of the source of the gelation mechanism were observed in the form of a red shift in the antisymmetric CH vibration with increasing temperature. These findings are consistent with the formation of a micellar gel network by the copolymer chains. [Copyright &y& Elsevier]

Abstract: The main objective of this study was to synthesize novel folic acid-functionalized diblock copolymer micelles and evaluate their solubilization of two poorly water-soluble anti-tumor drugs, tamoxifen and paclitaxel, which suffer from low water solubility and/or poor hydrolytic stability. The diblock copolymer consisted of a permanently hydrophilic block comprising 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) residues and a pH-sensitive hydrophobic block comprising 2-(diisopropylamino)ethyl methacrylate (DPA) residues. Folic acid (FA) was conjugated to the end of the MPC block so that this group was located on the micelle periphery. Tamoxifen- and paclitaxel-loaded micelles were prepared from FA–MPC–DPA copolymers prepared with two different block compositions that were designed to produce optimal solubilization of each drug. Their drug-loading capacities and aqueous stabilities were determined by high performance liquid chromatography. The hydrodynamic diameters of tamoxifen- and paclitaxel-loaded FA–MPC–DPA micelles ranged from 30 to 60nm, as judged by dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies. Finally, tamoxifen and paclitaxel release profiles were evaluated in phosphate buffer solution at pH 7.4 and 5. These studies demonstrated that FA–MPC–DPA micelles acted as useful drug carriers, leading to relatively slow release of both tamoxifen and paclitaxel into aqueous solution over a period of 7 days. In addition, rapid release can be triggered by lowering the solution pH to 5, which leads to protonation of the DPA block and hence rapid micellar dissociation. [Copyright &y& Elsevier]

Abstract: Major challenges associated with nano-sized drug delivery systems include removal from systemic circulation by phagocytic cells and controlling appropriate drug release at target sites. 2-methacryloyloxyethyl phosphorylcholine (MPC) has been copolymerised in turn with two pH responsive comonomers (2-(diethylamino)ethyl methacrylate (DEA) and 2-(diisopropylamino)ethyl methacrylate (DPA), to develop novel biocompatible drug delivery vehicles. Micelles were prepared from a series of copolymers with varying block compositions and their colloidal stability and dimensions were assessed over a range of solution pH using photon correlation spectroscopy. The drug loading capacities of these micelles were evaluated using Orange OT dye as a model compound. The cytotoxicity of the micelles was assessed using an in vitro assay. The MPC-DEA diblock copolymers formed micelles at around pH 8 and longer DEA block lengths allowed higher drug loadings. However, these micelles were not stable at physiological pH. In contrast, MPC-DPA diblock copolymers formed micelles of circa 30 nm diameter at physiological pH. In vitro assays indicated that these MPC-DPA diblock copolymers had negligible cytotoxicities. Thus novel non-toxic biocompatible micelles of appropriate size and good colloidal stability with pH-modulated drug uptake and release can be readily produced using MPC-DPA diblock copolymers. [Copyright &y& Elsevier]

The comparison of copolymers containing sulfobetaine or phosphobetaine moieties for use as potential biocompatible coatings has been investigated. Two statistical copolymers were produced by a free radical polymerisation technique, one based on a sulfobetaine and the other on a phosphobetaine, both with a silyl group component to allow thermal crosslinking after coating. PMMA and glass discs were dip-coated with the polymers and their properties were compared to the uncoated controls. Bacterial adhesion to these coated materials was assessed using Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa. Human macrophages and granulocytes were used to assess the adhesion and activation of inflammatory cells whilst mouse 3T3 fibroblast cells were used to assess the propensity for the materials to support fibroblast cell adhesion. In all cases the polymer coatings reduced cell adhesion with respect to the base materials. The phosphobetaine-based copolymer coatings were shown to be markedly superior to the sulfobetaine-based copolymer coatings. [Copyright &y& Elsevier]

Understanding the intra-tumoral distribution of chemotherapeutic drugs is extremely important in predicting therapeutic outcome. Tissue mimicking gel phantoms are useful for studying drug distribution in vitro but quantifying distribution is laborious due to the need to section phantoms over the relevant time course and individually quantify drug elution. In this study we compare a bespoke version of the traditional phantom sectioning approach, with a novel confocal microscopy technique that enables dynamic in situ measurements of drug concentration. Release of doxorubicin from Drug-eluting Embolization Beads (DEBs) was measured in phantoms composed of alginate and agarose over comparable time intervals. Drug release from several different types of bead were measured. The non-radiopaque DC Bead™ generated a higher concentration at the boundary between the beads and the phantom and larger drug penetration distance within the release period, compared with the radiopaque DC Bead LUMI™. This is likely due to the difference of compositional and structural characteristics of the hydrogel beads interacting differently with the loaded drug. Comparison of in vitro results against historical in vivo data show good agreement in terms of drug penetration, when confounding factors such as geometry, elimination and bead chemistry were accounted for. Hence these methods have demonstrated potential for both bead and gel phantom validation, and provide opportunities for optimisation of bead design and embolization protocols through in vitro-in vivo comparison. [Display omitted] [ABSTRACT FROM AUTHOR]

Drug-eluting Embolic Bead - Transarterial Chemoembolisation (DEB-TACE) is a minimally invasive embolising treatment for liver tumours that allows local release of chemotherapeutic drugs via ion exchange, following delivery into hepatic arterial vasculature. Thus far, no single in vitro model has been able to accurately predict the complete kinetics of drug release from DEB, due to heterogeneity of rate-controlling mechanisms throughout the process of DEB delivery. In this study, we describe two in vitro models capable of distinguishing between early phase and late phase drug release by mimicking in vivo features of each phase. First, a vascular flow system (VFS) was used to simulate the early phase by delivering DEB into a silicon vascular cast under high pulsatile flow. This yielded a burst release profile of drugs from DEB which related to the dose adjusted C max observed in pharmacokinetic plasma profiles from a preclinical swine model. Second, an open loop flow-through cell system was used to model late phase drug release by packing beads in a column with an ultra-low flow rate. DEB loaded with doxorubicin, irinotecan and vandetanib showed differential drug release rates due to their varying chemical properties and unique drug-bead interactions. Using more representative in vitro models to map discrete phases of DEB drug release will provide a better capability to predict the pharmacokinetics of developmental formulations, which has implications for treatment safety and efficacy. Unlabelled Image [ABSTRACT FROM AUTHOR]