Electrospray Functionalization of Titanium Dioxide Nanoparticles with Transferrin for Cerenkov Radiation Induced Cancer Therapy

Abstract

Titanium dioxide (TiO₂) nanoparticles have shown success as photosensitizers in the form of light-based cancer therapy called Cerenkov radiation induced therapy (CRIT). While TiO₂ nanoparticles have been reported to be an effective therapeutic agent, there has been little work to control their functionalization and stability in aqueous suspension. In this work, the controlled coating of 25 nm diameter TiO₂ nanoparticles with the glycoprotein transferrin (Tf) for application in CRIT was demonstrated using an electrospray system. Monodisperse nanoscale droplets containing TiO₂ and Tf were dried during flight, coating the proteins on the surface of the metal oxide nanoparticles. Real-time scanning mobility particle sizing, dynamic light scattering, and transmission electron microscopy show efficient control of the Tf coating thickness when varying the droplet size and the ratio of Tf to TiO₂ in the electrospray precursor suspension. Further, the functionality of Tf-coated TiO₂ nanoparticles was demonstrated, and these particles were found to have enhanced targeting activity of Tf to the Tf receptor after electrospray processing. The electrospray-coated Tf/TiO₂ particles were also found to be more effective at killing the multiple myeloma cell line MM1.S than that of nanoparticles prepared by other reported functionalization methods. In summary, this investigation not only provides a single-step functionalization technique for nanomaterials used in Cerenkov radiation induced therapy but also elucidates an electrospray coating technique for nanomaterials that can be used for a wide range of drug design and delivery purposes.

Keywords: Cerenkov radiation induced therapy; electrospray; functionalization; multiple myeloma; titanium dioxide; transferrin.

Figure 1.

TEM of 25 nm TiO₂ nanoparticles after synthesis.

Figure 2.

XRD of nanoparticles indicating anatase TiO₂.

Figure 3.

Isoelectric point measurements of electrospray precursor solutions with varying concentrations of Tf to TiO₂. Ratio of Tf:TiO₂ (wt:wt) ranged from 0:1 to 2:1.

Figure 4.

SMPS measured geometric mean mobility diameter for varying Tf to TiO₂ ratios.

Figure 5.

SMPS measured geometric mean mobility diameter for varying Tf nanoparticle sizes.

Figure 6.

Transmission electron microscopy images of TiO₂ nanoparticles that have been electrospray coated with varying concentrations of Tf. Ratio of Tf:TiO₂ is wt:wt: (A) 0:1, (B) 1:3, (C) 1:1, and (D) 2:1.

Figure 7.

Binding affinity of electrospray-coated Tf680/TiO₂ nanoparticle (open circle, K_D = 2.07 nm), conventionally prepared Tf680/TiO₂ nanoparticle (solid circle, K_D = 21.86 nm), and free Tf680 (triangle, K_D = 5.71 nm) with transferrin receptor analyzed by microscale thermophoresis.

Figure 8.

Cell viability assay comparing the conventional Tf/TiO₂ and electrospray Tf/TiO₂ constructs with and without exposure to 100 uCi ¹⁸FDG on (a) MM1S cells and (b) HT1080 cells.

Figure 9.

Electrospray setup with SMPS particle sampling for size measurements. A syringe pump supplies the precursor suspension to the electrospray capillary with a grounded capture solution below. A high voltage power supply controls the electric field. A scanning mobility particle sizer (SMPS) measures the mobility size of the electrospray-coated particles by first neutralizing the particles and passing them through a differential mobility analyzer and then counting them using a condensation particle counter.