Development of technetium-99m labeled ultrafine gold nanobioconjugates for targeted imaging of folate receptor positive cancers

Monte Carlo-derived 99m Tc uptake quantification with commercial planar MBI: Tumor and breast activity concentrations

BACKGROUND

Current molecular breast imaging (MBI) images are limited to qualitative evaluation, not absolute measurement, of 99m Tc uptake in benign and malignant breast tissues.

PURPOSE

This work assesses the accuracy of previously-published and newly-proposed tumor and normal breast tissue 99m Tc uptake MBI measurements using simulations of a commercial dual-headed planar MBI system under typical clinical and acquisition protocols.

METHODS

Quantification techniques were tested in over 4000 simulated acquisitions of spherical and ellipsoid tumors with clinically relevant uptake conditions using a validated Monte Carlo application of the GE Discovery NM750b system. The evaluated techniques consisted of four tumor total activity methodologies (two single-detector-based and two geometric-mean-based), two tumor MBI volume methodologies (diameter-based and ROI-based), and two normal tissue activity concentration methodologies (single-detector-based and geometric-mean-based). The most accurate of these techniques were then used to estimate tumor activity concentrations and tumor to normal tissue relative activity concentrations (RC).

RESULTS

Single-detector techniques for tumor total activity quantification achieved mean (standard deviation) relative errors of 0.2% (4.3%) and 1.6% (4.4%) when using the near and far detector images, respectively and were more accurate and precise than the measured 8.1% (5.8%) errors of a previously published geometric-mean technique. Using these activity estimates and the true tumor volumes resulted in tumor activity concentration and RC errors within 10% of simulated values. The precision of tumor activity concentration and RC when using only MBI measurements were largely driven by the errors in estimating tumor MBI volume using planar images (± 30% inter-quartile range).

CONCLUSIONS

Planar MBI images were shown to accurately and reliably be used to estimate tumor total activities and normal tissue activity concentrations in this simulation study. However, volumetric tumor uptake measurements (i.e., absolute and relative concentrations) are limited by inaccuracies in MBI volume estimation using two-dimensional images, highlighting the need for either tomographic MBI acquisitions or anatomical volume estimates for accurate three-dimensional tumor uptake estimates.

Nanoparticle biodistribution coefficients: A quantitative approach for understanding the tissue distribution of nanoparticles

The objective of this manuscript is to provide quantitative insights into the tissue distribution of nanoparticles. Published pharmacokinetics of nanoparticles in plasma, tumor and 13 different tissues of mice were collected from literature. A total of 2018 datasets were analyzed and biodistribution of graphene oxide, lipid, polymeric, silica, iron oxide and gold nanoparticles in different tissues was quantitatively characterized using Nanoparticle Biodistribution Coefficients (NBC). It was observed that typically after intravenous administration most of the nanoparticles are accumulated in the liver (NBC = 17.56 %ID/g) and spleen (NBC = 12.1 %ID/g), while other tissues received less than 5 %ID/g. NBC values for kidney, lungs, heart, bones, brain, stomach, intestine, pancreas, skin, muscle and tumor were found to be 3.1 %ID/g, 2.8 %ID/g, 1.8 %ID/g, 0.9 %ID/g, 0.3 %ID/g, 1.2 %ID/g, 1.8 %ID/g, 1.2 %ID/g, 1.0 %ID/g, 0.6 %ID/g and 3.4 %ID/g, respectively. Significant variability in nanoparticle distribution was observed in certain organs such as liver, spleen and lungs. A large fraction of this variability could be explained by accounting for the differences in nanoparticle physicochemical properties such as size and material. A critical overview of published nanoparticle physiologically-based pharmacokinetic (PBPK) models is provided, and limitations in our current knowledge about in vitro and in vivo pharmacokinetics of nanoparticles that restrict the development of robust PBPK models is also discussed. It is hypothesized that robust quantitative assessment of whole-body pharmacokinetics of nanoparticles and development of mathematical models that can predict their disposition can improve the probability of successful clinical translation of these modalities.

Methods for Radiolabelling Nanoparticles: SPECT Use (Part 1)

The use of nanoparticles (NPs) is rapidly increasing in nuclear medicine (NM) for diagnostic and therapeutic purposes. Their wide use is due to their chemical–physical characteristics and possibility to deliver several molecules. NPs can be synthetised by organic and/or inorganic materials and they can have different size, shape, chemical composition, and charge. These factors influence their biodistribution, clearance, and targeting ability in vivo. NPs can be designed to encapsulate inside the core or bind to the surface several molecules, including radionuclides, for different clinical applications. Either diagnostic or therapeutic radioactive NPs can be synthetised, making a so-called theragnostic tool. To date, there are several methods for radiolabelling NPs that vary depending on both the physical and chemical properties of the NPs and on the isotope used. In this review, we analysed and compared different methods for radiolabelling NPs for single-photon emission computed tomography (SPECT) use.

Optimization, Characterization and in vivo Evaluation of Paclitaxel-Loaded Folate-Conjugated Superparamagnetic Iron Oxide Nanoparticles

Background

Paclitaxel (PTX) has interesting anticancer activity. However, it is insoluble in water, which seriously hinders its use in clinical. Superparamagnetic iron oxide nanoparticles (SPIONs) are used as an ideal drug delivery system. Therefore, we proposed a folic acid (FA) targeting drug-loaded SPIONs to reduce its adverse reaction.

Methods

To improve the hydrophilicity of PTX, the structure of PTX was modified by succinic anhydride to obtain 2ʹ-succinate paclitaxel (SPTX). FA conjugated Polyethylene glycol (PEG)/polyethyleneimine (PEI)-SPIONs SPTX-loaded nanoparticles (SPTX@FA@PEG/PEI-SPIONs) were prepared by solvent volatilization and hydrogen bond adsorption, and the nano-formulation was optimized by response surface methodology (RSM). The characteristics, antitumor effect in vitro, pharmacokinetics, and biodistribution of SPTX@FA@PEG/PEI-SPIONs were evaluated.

Results

SPTX was successfully loaded on the surface of FA@PEG/PEI-SPIONs. The formation of SPTX@FA@PEG/PEI-SPIONs was exhibited water-dispersive monodispersity with high stability by RSM, and dynamic light scattering (DLS) was 178.1±3.12 nm, particle size observed in the transmission electron microscope (TEM) was 13.01±1.10 nm, and the encapsulation efficiency (EE) and loading efficiency (LE) were 81.1±1.66% and 14.8±1.46%, respectively. It enhanced the stability in normal physiological condition, accelerated drug release at tumorous pH, and preferentially prolonged the circulation time. In vitro, the SPTX@FA@PEG/PEI-SPIONs significantly targeted to folate receptor (FR) positive cancers cell (HNE-1) via the receptor-ligand mediated pathway, resulting in effective cytotoxic activity. Pharmacokinetic results demonstrated that SPTX@FA@PEG/PEI-SPIONs (t_1/2=3.41 h) had longer than free SPTX or PTX (t_1/2=1.67 h) in rats in vivo. Tissue distribution studies showed that SPTX@FA@PEG/PEI-SPIONs were present at high levels in the liver and help in targeting the folate receptors present on the kidneys.

Conclusion

These results suggest that SPTX@FA@PEG/PEI-SPIONs offer a highly promising approach to control drug release, improve drug pharmacokinetics and actively target the nasopharyngeal carcinoma.