Radiopaque scaffolds based on electrospun iodixanol/polycaprolactone fibrous composites

Grafts based on biodegradable polymer scaffolds are increasingly used in tissue-engineering applications as they facilitate natural tissue regeneration. However, monitoring the position and integrity of these scaffolds over time is challenging due to radiolucency. In this study, we used an electrospinning method to fabricate biodegradable scaffolds based on polycaprolactone (PCL) and iodixanol, a clinical contrast agent. Scaffolds were implanted subcutaneously into C57BL/6 mice and monitored in vivo using longitudinal X-ray imaging and micro-computed tomography (CT). The addition of iodixanol altered the physicochemical properties of the PCL scaffold; notably, as the iodixanol concentration increased, the fiber diameter decreased. Radiopacity was achieved with corresponding signal enhancement as iodine concentration increased while exhibiting a steady time-dependent decrease of 0.96% per day in vivo. The electrospun scaffolds had similar performance with tissue culture-treated polystyrene in supporting the attachment, viability, and proliferation of human mesenchymal stem cells. Furthermore, implanted PCL-I scaffolds had more intense acute inflammatory infiltrate and thicker layers of maturing fibrous tissue. In conclusion, we developed radiopaque, biodegradable, biocompatible scaffolds whose position and integrity can be monitored noninvasively. The successful development of other imaging enhancers may further expand the use of biodegradable scaffolds in tissue engineering applications.

Abstract 3722: Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer

Introduction: Irreversible electroporation (IRE) is an emerging, minimally invasive ablation technique with the advantage of not being affected by heat sink effect and the ability of ablation in close vicinity of major blood vessels. One limitation is local recurrence at the original ablated site. We hypothesize that combining IRE with a chemotherapeutic drug could prevent recurrence. NVP-BEZ235 (BEZ) is a dual PI3K/mTOR inhibitor that has shown promise for treating advanced solid malignancies, including sensitizing head and neck squamous cell carcinoma to radiotherapy. However, clinical trials revealed low bioavailability and high toxicity due to high dose oral administration over a long period of time. Thus, we formulated a liposomal BEZ (L-BEZ) and studied its antitumor effect in combination with IRE and compared the results with orally delivered BEZ (oral-BEZ).

Methods: IRE was performed using ECM 830 (BTX Harvard Apparatus) at various field strengths. BEZ was loaded into liposome (L-BEZ) by hydration-sonication method. The in vitro and in vivo efficacy was tested against head and neck cancer cell line, HN5 cells and in nude mice bearing HN5 xenografts (n=4/group). Mice were divided into control (no treatment), IRE (2500 V/cm for 99 pulses), IRE + L-BEZ (IRE at 2500 V/cm for 99 pulses and 7 doses of L-BEZ) and IRE + oral-BEZ (IRE at 2500 V/cm for 99 pulses and 21 doses of oral-BEZ) groups. Tumor size was monitored for 60 days.

Results: The hydrodynamic volume of NVP-BEZ ranged from 100-500nm. Maximum drug loading was achieved at 2.7mg/mL of BEZ. Electroporation disrupted nanoparticle's integrity even at the lowest tested field strength (250 V/cm) and released BEZ. At the highest field strength (2500 V/cm), approximately 5% of cells survived with IRE, while cells electroporated at 500 V/cm increased cell viability (114%) as compared to the untreated group (100 %). Combination of electroporation and L-BEZ significantly decreased cell viability at 500 V/cm (p<0.05). In vivo, IRE + L-BEZ suppressed tumor growth the longest, as compared with control (no treatment), IRE, and IRE + oral-BEZ. It was also the only group that resulted in no palpable tumor from day 30 to day 60. Survival studies show a significant difference between IRE + L-BEZ and the other groups. IRE + L-BEZ group had 100% animal survival on day 60. IRE + oral-BEZ had 50%, while IRE and control groups had 0% animal survival, on day 60. Also, the total administered BEZ amount in IRE + L-BEZ group was only 6.6% of that in IRE + oral-BEZ group.

Conclusion: Incomplete electroporation increases the viability of surviving cells both in vitro and in vivo. Co-delivery of L-BEZ enhances the antitumor efficacy of IRE alone. L-BEZ also decreases BEZ exposure compared to oral-BEZ. Thus, L-BEZ in combination with IRE potentially ensures complete eradication of surviving cells left after IRE.

Citation Format: Li Tian, Lucas Wang, Yang Qiao, Saisree Ravi, Ashley Chang, Thomas Alexander Rogers, Linfeng Lu, Adam D. Melancon, Marites Pasuelo Melancon. Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3722.

Selective uptake and imaging of aptamer- and antibody-conjugated hollow nanospheres targeted to epidermal growth factor receptors overexpressed in head and neck cancer

The purpose of this study was to compare the binding affinity and selective targeting of aptamer- and antibody-coated hollow gold nanospheres (HAuNS) targeted to epidermal growth factor receptors (EGFR). EGFR-targeting aptamers were conjugated to HAuNS (apt-HAuNS) by attaching a thiol-terminated single-stranded DNA to the HAuNS and then adding the complementary RNA targeted to EGFR. Apt-HAuNS was characterized in terms of size, surface charge, absorption, and number of aptamers per particle. The in vivo pharmacokinetics, in vivo biodistribution, and micro-SPECT/CT imaging of (111)In-labeled apt-HAuNS and anti-EGFR antibody (C225)-conjugated HAuNS were evaluated in nude mice bearing highly malignant human OSC-19 oral tumors. (111)In-labeled PEG-HAuNS was used as a control (n = 5/group). Apt-HAuNS did not have an altered absorbance profile or size (λmax = 800 nm; diameter = 55 nm) compared to C225-HAuNS or PEG-HAuNS. The surface charge became more negative upon conjugation of the aptamer (-51.4 vs -19.0 for PEG-HAuNS and -25.0 for C225-HAuNS). The number of aptamers/particle was ∼250. In vitro cell binding and in vivo biodistribution showed selective binding of the apt-HAuNS to EGFR. μSPECT/CT imaging confirmed that there was more tumor uptake of apt-HAuNS than C225-HAuNS. Aptamer is a promising ligand for image-guided delivery of nanoparticles for treatment of tumor cells overexpressing EGFR.