In Vitro and In Vivo Delivery of Magnetic Nanoparticle Hyperthermia Using a Custom-Built Delivery System

Summary

This protocol presents techniques and methodology necessary for the accurate delivery of magnetic nanoparticle hyperthermia using a sophisticated delivery and monitoring system.

Abstract

Hyperthermia has long been used in the treatment of cancer. Techniques have varied from the intra-tumoral insertion of hot iron rods, to systemically delivered tumor antibody-targeted magnetic nanoparticles, at temperatures from 39 ˚C (fever-level) to 1,000 ˚C (electrocautery) and treatment times from seconds to hours. The temperature-time relationship (thermal dose) dictates the effect with high thermal doses resulting in the tissue ablation and lower thermal doses resulting in sublethal effects such as increased blood flow, accumulation of drugs and immune stimulation. One of the most promising current medical therapies is magnetic nanoparticle hyperthermia  (mNPH). This technique involves activating magnetic nanoparticles, that can be delivered systemically or intratumorally, with a non-invasive, non-toxic alternating magnetic field. The size, construct and association of the magnetic nanoparticles and the frequency and field strength of the magnetic field are major heating determinants. We have developed sophisticated instrumentation and techniques for delivering reproducible magnetic nanoparticle hyperthermia in large and small animal models and cultured cells. This approach, using continuous, real time temperature monitoring in multiple locations, allows for the delivery of well-defined thermal doses to the target tissue (tumor) or cells while limiting non-target tissue heating. Precise control and monitoring of temperature, in multiple sites, and use of the industry standard algorithm (cumulative equivalent minutes at 43 ˚C /CEM43), allows for an accurate determination and quantification of thermal dose. Our system, which allows for a wide variety of temperatures, thermal doses, and biological effects, was developed through a combination of commercial acquisitions and inhouse engineering and biology developments. This system has been optimized in a manner that allows for the rapid conversion between ex vivo, in vitro, and in vivo techniques. The goal of this protocol is to demonstrate how to design, develop and implement an effective technique and system for delivering reproducible and accurate magnetic nanoparticle therapy (mNP) hyperthermia.

Introduction

Hyperthermia has historically been used in cancer therapy, either alone or in combination with other treatments. Although it has a long history of use, the most advantageous method for delivering this treatment is still being debated and is dependent on the disease site and location. Methods for hyperthermia delivery include microwave, radiofrequency, focused ultrasound, laser, and metallic nanoparticles (such as gold or iron oxide)^1,2,3,4. These methods of delivery can lead to a range of treatment temperatures from fever-level through to hu....

Protocol

The Dartmouth College Animal Care and Use Program is accredited by the American Association for the Accreditation of Laboratory Animal Care (iAAALAC) and adheres to all UDSA and NIH (Office of Laboratory Animal Welfare) guidelines and regulations. All in vivo studies were approved by the Dartmouth College Institutional Animal Care and Use Committee (IACUC). Euthanasia procedure adhere to the 2020 AVMA Guidelines for the Euthanasia of Animals.

1. Instrumentation/design of the system

1. Design custom AMF antenna (coil) to be a closed loop, choosing shapes to create the desired magnetic field. Use inductance formulas and char....

Results

In vitro studies
Cells will only achieve and maintain the desired temperature and thermal dose if the amount and concentration of the magnetic nanoparticles/iron and the AMF are appropriately matched. When using magnetic nanoparticles to heat cells in vitro (and in vivo), it should be noted that to achieve hyperthermia in cells with internalized magnetic nanoparticles, a specific level of intracellular mNP/Fe will be necessary, and number and proximity of mNP loaded cells, to each other, will be nece.......

Discussion

The design and implementation of this system provides the ability to conduct accurate and reproducible in vitro and in vivo magnetic nanoparticle hyperthermia experiments. It is critical that the system is designed such that the AMF frequency and field strength are adequately matched to the magnetic nanoparticle type, concentration, and the tissue location and temperature desired. Additionally, the accurate monitoring of the temperature in real time is crucial for safety and the calculation of an accurate thermal dose (c.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
.25% Trypsin	Corning	45000-664	available from many companies
1.5 mL tubes	Eppendorf	Eppendorf 22363204	available from many companies
B16F10 murine melanoma cells	American Type Culture Collection	CRL-6475
C57/Bl6 mice	Charles river	027C57BL/6	6-week-old female mice
Chiller	Thermal Care	NQ 5 series	chiller that cools the coil
Coolant fluid	Dow Chemical Company	Dowtherm SR-1	antenna cooling fluid
Fetal Bovine serum	Hyclone	SH30071	available from many companies
fiber optic probes, software and chassis	FISO		FISO evolution software used to read the temperatures
IR camera	Flir		infrared camera to monitor unintentional heating
iron oxide nanoparticles	micromod Partikeltechnologie GmbH	Bionized NanoFerrite	dextran coated iron oxide nanoparticles
mouse coil, solenoid	Fluxtrol	custom built
penicillin/streptomycin	Corning	45000-652	available from many companies
RF generator	Huttinger	TIG 10/300	power source
RPMI media	Corning	45000-396	available from many companies