Thermal and Radiation Curing of Phenylethynyl Terminated Macromers

The thermal and gamma-irradiation induced curing of two phenylethynyl terminated composite resin systems, DFB/BPF and PETI5A, was investigated. Thermal curing of these matrix resin samples was performed at a temperature of 360 °C, gamma irradiation of the samples was conducted at 300 °C at a dose rate of 2.2 kGy h−1. The reaction and subsequent loss of ethynyl groups in the resins for both cure methods was demonstrated by observing the decrease of the 2215 cm−1 peak in the Raman spectra of the resins. Fully cured resin samples were found to have glass transition temperatures of 244–246 °C and 278–280 °C for DFB/BPF and PETI5A respectively. Similar relationships between Tg and fractional conversion were observed in both resins. The apparent polymerization rate, Rp, for thermal cure at 360 °C, was found to be 4 :79 × 10−22%s−1 in PETI5A and 3.22 × 10−2%s−1 in DFB/BPF. Catastrophic degradation under nitrogen was observed to commence near 450 °C and 530 °C, with 5% weight losses occurring at 455 °C and 540 °C for DFB/BPF and PETI5A respectively. Gamma radiation induced cure at 300 °C was shown to be feasible, with full cure being reached with doses of 40 kGy for DFB/BPF and 100 kGy for PETI5A.

G -Values for Scission and Crosslinking on γ — Radiolysis of Ultem at 303 K

The radiation chemical yields G( S) and G( X) for H-linking and Y-linking models for Ultem have been calculated from molecular weight analysis by gel permeation chromatography. These G-values have been compared with the G-values obtained from analysis of soluble fractions above the gel dose, which have been reported in previous works. An analysis of the molecular weight data in terms of H-linking and Y-linking mechanisms yielded values of G( S H) = 1.0 × 10−3 and G( H) = 6.0 × 10−3 and G( S Y) = 1.3 × 10−2 and G( Y) = 1.8 × 10−2. The corresponding values obtained from the solubility data were G( S H) = 0.53 × 10−2, G( H) = 1.39 × 10−2, G( S Y) = 4.2 × 10−2 and G( Y) = 4.6 × 10−2. The origin of the disagreement between the molecular weight and solubility values is not clear, but it could arise as a result of observed microgel formation below the reported gel dose of 0.13 MGy. Whether the crosslink mechanism proceeds by an H-linking or Y-linking process is also unclear and will require direct observation of the crosslinking structures.

Bioerodable PLGA-Based Microparticles for Producing Sustained-Release Drug Formulations and Strategies for Improving Drug Loading

Poly(lactic-co-glycolic acid) (PLGA) is the most widely used biomaterial for microencapsulation and prolonged delivery of therapeutic drugs, proteins and antigens. PLGA has excellent biodegradability and biocompatibility and is generally recognized as safe by international regulatory agencies including the United States Food and Drug Administration and the European Medicines Agency. The physicochemical properties of PLGA may be varied systematically by changing the ratio of lactic acid to glycolic acid. This in turn alters the release rate of microencapsulated therapeutic molecules from PLGA microparticle formulations. The obstacles hindering more widespread use of PLGA for producing sustained-release formulations for clinical use include low drug loading, particularly of hydrophilic small molecules, high initial burst release and/or poor formulation stability. In this review, we address strategies aimed at overcoming these challenges. These include use of low-temperature double-emulsion methods to increase drug-loading by producing PLGA particles with a small volume for the inner water phase and a suitable pH of the external phase. Newer strategies for producing PLGA particles with high drug loading and the desired sustained-release profiles include fabrication of multi-layered microparticles, nanoparticles-in-microparticles, use of hydrogel templates, as well as coaxial electrospray, microfluidics, and supercritical carbon dioxide methods. Another recent strategy with promise for producing particles with well-controlled and reproducible sustained-release profiles involves complexation of PLGA with additives such as polyethylene glycol, poly(ortho esters), chitosan, alginate, caffeic acid, hyaluronic acid, and silicon dioxide.

The evolution of gadolinium based contrast agents: from single-modality to multi-modality

Gadolinium-based contrast agents are extensively used as magnetic resonance imaging (MRI) contrast agents due to their outstanding signal enhancement and ease of chemical modification. However, it is increasingly recognized that information obtained from single modal molecular imaging cannot satisfy the higher requirements on the efficiency and accuracy for clinical diagnosis and medical research, due to its limitation and default rooted in single molecular imaging technique itself. To compensate for the deficiencies of single function magnetic resonance imaging contrast agents, the combination of multi-modality imaging has turned to be the research hotpot in recent years. This review presents an overview on the recent developments of the functionalization of gadolinium-based contrast agents, and their application in biomedicine applications.

Spectral normalisation by error minimisation for prediction of conversion in solvent-free catalytic chain transfer polymerisations

This work provides a robust method to determine spectral normalization points in reactions with no known constant responses.

Multifunctional hyperbranched polymers for CT/19F MRI bimodal molecular imaging

Multifunctional hyperbranched polymers containing iodine and fluorine were synthesised by reversible addition–fragmentation chain transfer (RAFT) polymerisation, and evaluated as novel contrast agents for CT/¹⁹F MRI bimodal molecular imaging.

Novel polymeric bioerodable microparticles for prolonged-release intrathecal delivery of analgesic agents for relief of intractable cancer-related pain

Intractable cancer-related pain complicated by a neuropathic component due to nerve impingement is poorly alleviated even by escalating doses of a strong opioid analgesic. To address this unmet medical need, we developed sustained-release, bioerodable, hydromorphone (potent strong opioid)- and ketamine (analgesic adjuvant)-loaded microparticles for intrathecal (i.t.) coadministration. Drug-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles were prepared using a water-in-oil-in-water method with evaporation. Encapsulation efficiency of hydromorphone and ketamine in PLGA (50:50) microparticles was 26% and 56%, respectively. Microparticles had the desired size range (20-60 μm) and in vitro release was prolonged at ≥28 days. Microparticles were stable for ≥6 months when stored refrigerated protected from light in a desiccator. Desirably, i.t. injected fluorescent dye-labeled PLGA microparticles in rats remained in the lumbar region for ≥7 days. In a rat model of neuropathic pain, i.t. coinjection of hydromorphone- and ketamine-loaded microparticles (each 1 mg) produced analgesia for 8 h only. Possible explanations include inadequate release of ketamine and/or hydromorphone into the spinal fluid, and/or insufficient ketamine loading to prevent development of analgesic tolerance to the released hydromorphone. As sub-analgesic doses of i.t. ketamine at 24-48 h intervals restored analgesia on each occasion, insufficient ketamine loading appears problematic. We will investigate these issues in future work.

Tensile properties and in vitro degradation of P(TMC-co-LLA) elastomers

P(TMC-co-LLA) elastomers have shown great potential for various biomaterials applications. This study investigated properties key to such applications. Six statistical copolymers with 16 to 49 mol% TMC were synthesized and it was found that the LLA sequence length changed from 14 to 3 for the copolymer series while the M[combining macron]_n decreased from 63 to 31 kg mol^-1 with increasing TMC content. The thermal properties showed lower T_g values with increasing TMC content which agreed with the Fox equation. Solvent cast films exhibited Young's modulus values between 2.8 and 271 MPa, ultimate tensile strength of 0.6-15.5 MPa and elongation at failure from 356 to 1287%. In vitro degradation in PBS at 37 °C over 34 weeks demonstrated an induction period of 9 weeks during which the water content was minimal for all copolymers. Copolymer films with 21 or greater mol% TMC were found to undergo homogeneous bulk degradation, while films with 16 mol% TMC underwent heterogeneous bulk degradation.

Abstract LB-12: EphA2 as a diagnostic imaging target in glioblastoma: A PET/MRI study

Neuroimaging has evolved from being a purely anatomical tool to a discipline that can offer anatomical, functional, hemodynamic, metabolic and molecular information. From the perspective of patients with glioblastoma multiforme (GBM), the use of neuroimaging techniques is an essential stage in diagnosis and classification of the tumour and to assess patient response following treatment.[1]

The Eph receptor tyrosine kinases (RTKs) and their Eph-interacting ligands (ephrins) are the largest family of RTKs consisting of 16 Eph receptors and 9 ephrin ligands.[2] From the discovery of the first Eph RTK evidence has been presented to implicate the Eph family in tumour development and progression, a body of work which continues to grow. The complex bidirectional signaling mechanisms between Eph RTKs and ephrin ligands have been shown to influence cell morphology, adhesion, migration, invasion, cell proliferation and survival.[2-4] Recently, many studies have linked Eph and ephrin expression levels with tumour progression and metastatic spread and, as a consequence, patient survival. In the specific case of EphA2, an increasing number of studies have shown a correlation between EphA2 overexpression and poor patient prognosis.[5,6] As such, EphA2 represents an attractive target for highly specific PET imaging using a labeled monoclonal antibody (mAb).

In this study we present simultaneous PET/MRI of a 64Cu labeled mAb specific to the human form of EphA2. We show efficient targeting of the tumour in three intracranial mouse models of GBM. In addition, we show that non-specific binding can be significantly reduced by blocking removal of the mAb from the blood pool via Fc receptor binding. In all cases we compare the ability of the mAb to delineate tumour boundaries with the current clinical imaging techniques of 18F-FDOPA PET imaging and gadolinium (Gd) contrast enhanced MRI.

[1] Henson, J. W.; Gonzalez, R. G. Expert review of neurotherapeutics 2004, 4.

[2] Pasquale, E. B. Nature Reviews Cancer 2010, 10, 165.

[3] Pasquale, E. B. Cell 2008, 133, 38.

[4] Pasquale, E. B. Nat Rev Mol Cell Bio 2005, 6, 462.

[5] Lackmann, M.; Boyd, A. W. Science Signaling 2008, 1.

[6] Zhuang, G. L. et al. Cancer Res 2010, 70, 299.

Citation Format: Simon Puttick, Brett W. Stringer, Bryan W. Day, Karine Mardon, Gary J. Cowin, Michael Fay, Kristofer J. Thurecht, Andrew K. Whittaker, Andrew W. Boyd, Stephen Rose. EphA2 as a diagnostic imaging target in glioblastoma: A PET/MRI study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-12. doi:10.1158/1538-7445.AM2014-LB-12

Characteristics of starch-based films plasticised by glycerol and by the ionic liquid 1-ethyl-3-methylimidazolium acetate: a comparative study

This paper reports the plasticisation effect of the ionic liquid, 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), as compared with the traditionally used plasticiser, glycerol, on the characteristics of starch-based films. For minimising the additional effect of processing, a simple compression moulding process (which involves minimal shear) was used for preparation of starch-based films. The results show that [Emim][OAc] was favourable for plasticisation, i.e., disruption of starch granules (by scanning electron microscopy), and could result in a more amorphous structure in the starch-based materials (by X-ray diffraction and dynamic mechanical analysis). (13)C CP/MAS and SPE/MAS NMR spectroscopy revealed that not only was the crystallinity reduced by [Emim][OAc], but also the amorphous starch present was plasticised to a more mobile form as indicated by the appearance of amorphous starch in the SPE/MAS spectrum. Mechanical results illustrate that, when either glycerol or [Emim][OAc] was used, a higher plasticiser content could contribute to higher flexibility. In spite of the accelerated thermal degradation of starch by [Emim][OAc] as shown by thermogravimetric analysis, the biodegradation study revealed the antimicrobial effect of [Emim][OAc] on the starch-based materials. Considering the high-amylose starch used here which is typically difficult to gelatinise in a traditional plasticiser (water and/or glycerol), [Emim][OAc] is demonstrated to be a promising plasticiser for starch to develop "green" flexible antimicrobial materials for novel applications.