Amphiphilic ionic oligomers as functionalizable stabilizers for gene therapy nanoparticles

Inorganic nano drug delivery vehicles require the use of an appropriate organic stabilizer. Examples are uncharged thiol containing macromolecules or polymers for gold NPs [1] , positively charged polyethylenimines for metals [2], or carboxylate bearing polymers for cationic calcium phosphates [3].To match a variety of demands, including ion interaction, solubility, good synthetic availability, cellular uptake and endosomal escape, we present the synthesis of amphiphilic functionalizable terpolymers. Our work is based on a broad experience in the synthesis and application of free radical synthesis of maleic anhydride-containing cooligomers. [4],[5],[6] The shown terpolymers [Fig. 1] consist of tetradecylacrylate (14), methoxy-poly(ethylenglycol) methacrylate (PEG, Mn 950) and maleic anhydride (MA). The addition of filler monomers such as 4-acryloylmorpholine (AMO) or N-vinylpyrrolidone (NVP) has also been realized. Reactive anhydride moieties allowed for accessible functionalization by amide formation e.g. with Cy5 amine as fluorescent label or with the azide linker (11-azido-3,6,9-trioxaundecan-1-amine) which renders the oligomers accessible for any kind of Cu (I) catalysed azide alkyne click reaction.

Figure 1: A Anhydride-containing terpolymer synthesis and B illustration of stabilization of in situ generated siRNA-loaded calcium phosphate nanoparticles.
Anhydride content and intactness were determined by conductometric titration. 1H-NMR was used to quantify comonomer integration and size exclusion chromatography for molecular weight analysis. Terpolymer synthesis yields ranged between 24.1 and 51.1%, and molecular weights between 4500 and 6500 Da. MA incorporation was controlled by the reaction feed and anhydride intactness in the oligomers was higher than 60% (o14PEGMA (4/4/10)). Effects of comonomer feed on integration in the resulting purified oligomers are presented. Pristine oligomers were transferred to the respective polyanionic ammonia salt. The here presented oligomers are able to stabilize siRNA bearing calciumphosphate nanoparticles, show typical amphiphilic behaviour and can be functionalized by alkyne-azide cycloaddition.
Acknowledgements: European Development Found Saxony (EFRE) and the SAB (Sächsische Aufbaubank, Saxony, Germany) for funding
References:
1. Masse, Florence, et al.: Molecules 2019. 24 (16):
2. Norouzi, Mohammad, et al.: Nanomaterials 2020. 10 (3):
3. Zhang, Shuiquan, et al.: J. Mater. Chem. B 2020. 8 (41): 9589–9600.
4. Nawaz, Hafiz Awais, et al.: J. Mater. Chem. B 2021 (9): 2295–2307.
5. Wölk, Christian, et al.: Adv. Mater. Interfaces 2020. 7 (22): 2001168.
6. Loth, Tina, et al.: React. Funct. Polym. 2013. 73 (11): 1480–1492.