Scalable production of highly concentrated chitosan/TPP nanoparticles in different pHs and evaluation of the in vitro transfection efficiency

• Chitosan/pentasodium tripolyphosphate nanoparticles were produced in a reactor with mechanical stirring ready to scale up.
• Chitosan initial pH influenced mean diameter, polydispersity index and zeta potential of CHI/TPP nanoparticles.
• Higher pHs forms nanoparticles with lower polydispersity index and higher mean diameter.
• Time is an important factor for particle stability, which was evaluated simulating the medium in biological application.
• Difference on physico-chemical nanoparticles properties have non-significative difference on in vitro transfection studies.

Chitosan (CHI) pentasodium tripolyphosphate (TPP) nanoparticles have been studied extensively for biomedical applications. However, these studies do not attempt to develop a scalable and reproducible process. In this study, we investigated the production of CHI/TPP nanoparticles using a high concentration (5 mg/mL) of chitosan at three different pHs (4, 5 and 5.5) in a scalable batch process using tank reactor with baffles and a cowles impeller. The smallest size was obtained when the pH was 4, but the polydispersity index (PDI) was the highest; the opposite behavior was observed at pH 5.5. CHI/TPP nanoparticles were also studied in terms of physico-chemical stability in two extreme situations: increasing the pH of the CHI/TPP nanoparticles to 7 and adding nanoparticles to PBS buffer (pH 7.4). In both cases, the buffer conditions modulated the nanoparticle properties and time was also an important parameter. Plasmid pVAX1Luc was used for incorporation into CHI/TPP nanoparticles (CHI:TPP 5.8:1 m/m) at 10 and 20% DNA/CHI w/w. The final DNA-loaded nanoparticles ranged in size from 142 to 248 nm and 190 to 254 nm for 10 and 20% DNA, respectively. The final physico-chemical properties and process differences in CHI/TPP nanoparticle production have a small influence on in vitro transfection studies.

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