Development of theranostic PNIPAM/SPION nanoparticles for cancer treatment

Backround/Aim: Stimuli-responsive nanoparticles are being investigated for controlled delivery of toxic drugs to the disease site, especially in cancer. Tumors are known as more acidic and hypertermic in comparison with healthy body parts. Thus, pH and/or temperature-responsive drug delivery vehicles have a tremendous importance in achieving secure delivery and se-cretion of the cargo chemotherapeutic drug only to the tumor site to enhance the efficacy and reduce side effects. Materi-als & Methods: In this study, Poly (N-isopropylacrylamide) (PNIPAM) bound Fe3O4 nanoparticles (SPION-PNIPAM) were synthesized via surface initiated ATRP (atom transfer radical polymerization) and loaded with chemotherapeutic drug Doxo-rubicin (Dox). We performed MTT and Trypan Blue Exclusion Assay to evaluate dose and temperature dependent cell viabili-ty exposed to Dox, nanoparticles and Dox loaded nanoparticles. Confocal analysis was carried out to observe cellular uptake and intracellular trafficking of NPs. Gamma-H2AX phosphor-ylation, p53 and Caspase activation were examined through Immunoblotting to identify the NP and drug dependent DNA damage in vitro. Results: Release studies performed at differ-ent temperatures (25 °C, 37 °C, 42 °C) and pH (7.4, 5.6) re-vealed both pH and temperature dependent release which is minimal at physiological pH and temperature and maximum at low pH-high temperature combination. For the toxicity studies, we have used HeLa cervical cancer cells. Administration of the PNIPAM/SPION alone did not show toxic effect event at high doses, proving safety of the delivery vehicle.. However, Dox loaded NPs (0.3 μg/ml and 1.3 μg/ml drug content) showed dose and time dependent toxicity. Based on the confocal microsco-py studies, internalization of NPs increases with the NP dose, incubation time and temperature. We have also observed that NPs were internalized through endosomal pathway using the endosomal markers Rab5 and Rab9. In addition, cells incubated with Dox loaded NPs exhibited higher levels of gamma-H2AX phosphorylation, p53 and Caspase activation in comparison to free Doxorubicin. Conclusion: According to our findings, du-ally responsive controlled drug release behavior makes these SPION-PNIPAM nanoparticles valuable stimuli responsive theranostic candidates