<p>Poly(3-hydroxi-butyrate-co-3-hydroxy-valerate) (PHB-HV) microparticles loaded with holmium acetylacetonate as potential contrast agents for magnetic resonance images</p>

Abstract

Introduction Biodegradable polymers that contain radioactive isotopes such as Holmium 166 have potential applications as beta particle emitters in tumor tissues. Also, Ho(III) is paramagnetic, which makes it suitable as a contrast agent for magnetic resonance (MR) images. Methods Holmium acetylacetonate (Ho(acac) 3 ) loaded poly(3-hydroxy-butyrate-co-3-hydroxy-valerate) microspheres, with 5% or 8% of 3-hydroxy-valerate (HV), were prepared by emulsification/evaporation process within 20–53 μm size. Microspheres characterization was done using scanning electron microscopy, energy-dispersive X-ray, and infrared spectroscopies. The release of holmium(III) in sodium phosphate buffer (pH 7.4) was followed for 9 days with inductively coupled plasma. Finally, T 2 and T 2 * magnetic resonance images (MRI) were acquired and compared with the MRI of the inclusion complex of holmium acetylacetonate in some β-cyclodextrins. Results Holmium acetylacetonate loading, evaluated by thermogravimetry, was up to 20 times higher for copolymer with 5% of HV. It was shown that microspheres loaded with Ho(acac) 3 exhibited an accumulation of Ho(III) on their surfaces but were stable over time, as no expressive release of holmium(III) was detected in 9-day exposition to sodium phosphate buffer. Holmium acetylacetonate in both microspheres or inclusion complexes was very efficient in obtaining T 2 and T 2 * weighted images in magnetic resonance, thus, might be used as contrast agents. Conclusion This is the first description of the use of inclusion complexes of holmium acetylacetonate in biodegradable polymers as contrast agents. New investigations are underway to evaluate the resistance of PHB-HV polymer microparticles to nuclear activation to assess their potential for use as radiopharmaceuticals for the treatment of liver cancer.

Methods of Granulocyte Isolation from Human Blood and Labeling with Multimodal Superparamagnetic Iron Oxide Nanoparticles

“…The corresponding T2 values were 56.6 ms for the control, 47.5 ms (labeling with 10 µg Fe/mL), 36.8 ms (labeling with 30 µg Fe/mL) and 23.2 ms (labeling with 50 µg Fe/mL). These results show adequate internalization and, due to the M-SPIONs, a high r2/r1 ratio of 165.8 (r2 = (19.9 ± 0.9) × 10 −4 ms −1 µg Fe −1 mL and r1 = (1.2 ± 0.5) × 10 −5 ms −1 µg Fe −1 mL), indicating a strong contrast in T2-weighted images [95][96][97][98][99]. In relation to the NIRF qualitative analysis, the NIRF intensity signal was possible due to the M-SPIONs used for granulocyte-labeling having a fluorophore coupled to the infrared wavelength.…”

Microbial Production of Biopolymer Polyhydroxybutyrate (PHB): Current Challenges and its Application

“…It is demonstrated as a valuable nutraceutical compound and acts as a prebiotic by increasing the number of beneficial microbes in the gut flora [114]. The PHB-HV microspheres loaded with Ho(acac)3 (holmium acetylacetonate) accumulated Ho(III) on their surfaces but remained stable over time, as no expressive release of Ho(III) was found after a 9 day exposure to sodium phosphate buffer, which makes it suitable contrast agent for the magnetic resonance (MR) images by emitting beta-particles in tumor tissues [115]. The electrostatic interaction of negatively charged survivin antisense oligonucleotide (Sur-ASON) and positively charged PHB-b-PDMAEMA (PHB-P) co-polymer, followed by the induction of thermosensitive PF127 hydrogel, resulted in the development of a gene delivery platform.…”