Preparation of a novel injectable in situ-gelling nanoparticle with applications in controlled protein release and cancer cell entrapment

Abstract

Temperature sensitive injectable hydrogels have been used as drug/protein carriers for a variety of pharmaceutical applications. Oligo(ethylene glycol) methacrylate (OEGMA) monomers with varying ethylene oxide chain lengths have been used for the synthesis of in situ forming hydrogel. In this study, a new series of thermally induced gelling hydrogel nanoparticles (PMOA hydrogel nanoparticles) was developed by copolymerization with di(ethylene glycol) methyl ether methacrylate (MEO₂MA), poly(ethylene glycol) methyl ether methacrylate (300 g mol^-1, OEGMA₃₀₀), and acrylic acid (AAc). The effects of acrylic acid content on the physical, chemical, and biological properties of the nanoparticle-based hydrogels were investigated. Due to its high electrostatic properties, addition of AAc increases LCST as well as gelation temperature. Further, using Cy5-labelled bovine serum albumin and erythropoietin (Epo) as model drugs, studies have shown that the thermogelling hydrogels have the ability to tune the release rate of these proteins in vitro. Finally, the ability of Epo releasing hydrogels to recruit prostate cancer cells was assessed in vivo. Overall, our results support that this new series of thermally induced gelling systems can be used as protein control releasing vehicles and cancer cell traps.

Fig. 1. (A) Dynamic Light Scattering (DLS) measurement demonstrating polydispersity of PMOA3 nanoparticle at 24 °C. (B) Scanning Electron Microscope (SEM) image illustrating that the particles are in spherical shape. (C) DLS measurement at both 24 and 37 °C demonstrating an increase in particle size with the increase of acrylic acid content. (D) DLS measurement demonstrating a decrease in zeta potential with the increase of acrylic acid.

Fig. 2. (A) Turbidity measurement of thermogelling nanoparticles (1.0 mg mL⁻¹ in deionized water) demonstrating an increase in transition temperature with the increase of acrylic acid. Hydrogel nanoparticles dispersed in PBS (ionic strength: 43.5 mM) have lower transition temperatures than with deionized water. (B) Inversed particle sample (PMOA3) in a test tube illustrating that the hydrogel nanoparticles (60 mg mL⁻¹) form gel at physiological temperature. (C) Rheometry measurement of thermogelling nanoparticles (60 mg mL⁻¹) demonstrating the viscosity as a function of temperature.

Fig. 3. (A) Measurement of water loss demonstrating a decrease in water loss with the increase of acrylic acid. 1.0 mL of hydrogel nanoparticles (60 mg mL⁻¹) were incubated at 37 °C for 4 hours, and then the released water was collected from the top of the gels and measured the weight of the lost water. SEM images illustrating porosity of PMOA0 (B), PMOA1 (C), and PMOA3 (D) nanoparticles matrix.

Fig. 4. In vitro release tests of proteins. (A) Release profiles of Cy®5-labeled BSA and (B) release profiles of Cy®5-labeled Epo.

Fig. 5. In vitro analysis of hydrogel-associated cell and tissue toxicity. (A) In vitro toxicity of the thermogelling gels to cells. (B) H&E staining and cell quantification of tissue surrounding PMOA3 and PLGA implants.

Fig. 6. The ability of chemokine-releasing thermogelling nanoparticles to recruit prostate cancer cells in mice. (A) Whole body imaging and (B) fluorescent intensity measurement of NIR-labeled prostate cancer cells at the implant site of Epo and Epo-releasing thermogelling nanoparticles in animals.