PO-116 Indium-111 afterloading of preformed EGF-containing liposomes for molecularly targeted radionuclide delivery via ultrasound-induced cavitation

Abstract

Introduction Radiolabelled nuclear localising peptides are a promising cancer therapy. However, These peptides have unfavourable circulation kinetics and are highly susceptible to degradation and elimination by local enzymes. Liposome nanoparticles consist of a phospholipid bilayer structure which can encapsulate a therapeutic payload. Such encapsulation can improve pharmacokinetic profiles. One promising method for targeted therapeutic delivery is through the use of ultrasound, a longitudinal pressure wave of frequency >20 kHz. Ultrasound can be efficiently delivered through the body and cause Liposomes to crack and release their payload. The aim of this proposal is to develop a clinically relevant method of loading the therapeutic Indium labelled Epidermal Growth Factor (111In-DTPA-hEGF) into liposomes which can be released at the target site via externally applied ultrasound. Material and methods hEGF-DTPA was created and passively loaded into liposomes. Liposomes were then loaded with indium via incubation with indium chloride for 1 hour followed by loading efficiency analysis by TLC. Liposome structure was analysed via TEM and size distribution was analysed via DLS. For therapeutic efficacy liposomes were incubated with an EGFR positive cell (468) and an EGFR negative cell line (MCF7). After application of ultrasound cells were seeded in 6 well plates and colony analysis was performed after 14 days along with all controls. Uptake studies were also performed along with γ-H2AX staining. The biodistribution of the liposomes was examined in nude mice. Results and discussions BY TEM and DLS liposome size was approximately 200 nm. Protein loaded liposomes had a 93% loading efficiency for Indium encapsulation whereas empty liposomes only loaded 34% of the Indium. The Liposomes were found to be stable over 5 days. Uptake results indicated that cell uptake of 111In-DTPA-hEGF from liposomes was dependent on ultrasound application. An EGFR expressing cell line exposed to 111In-hEGF-DTPA loaded liposomes and ultrasound showed a>90% decrease in colony survival. A biodistribution in vivo has been obtained. Conclusion A protein loaded liposome has been successfully created and loaded Indium within one hour imitating techniques currently used in radiopharmacies. The liposome was shown to crack upon application of ultrasound and release 111In-hEGF-DTPA which resulted in a statistically significant impact on EGFR positive cells. This technology can be utilised for ultrasound targeted delivery of radiotherapeutics to tumours.