HPMA-Based Nanoparticles for Fast, Bioorthogonal iEDDA Ligation

Abstract

Fast and bioorthogonally reacting nanoparticles are attractive tools for biomedical applications such as tumor pretargeting. In this study, we designed an amphiphilic block copolymer system based on HPMA using different strategies to introduce the highly reactive click units 1,2,4,5-tetrazines (Tz) either at the chain end (Tz-CTA) or statistical into the hydrophobic block. This reactive group undergoes a rapid, bioorthogonal inverse electron-demand Diels–Alder reaction (iEDDA) with trans-cyclooctenes (TCO). Subsequently, this polymer platform was used for the preparation of different Tz-covered nanoparticles, such as micelles and colloids. Thereby it was found that the reactivity of the polymeric micelles is comparable to that of the low molar mass tetrazines. The core-cross-linked micelles can be successfully conjugated at rather low concentrations to large biomacromolecules like antibodies, not only in physiological buffer, but also in human blood plasma, which was confirmed by fluorescence correlation spectroscopy (FCS).

Polymeric Nanoparticles with Neglectable Protein Corona

“…All nanoparticles (30 mg mL −1 ) were incubated with EDTA‐stabilized, pure and undiluted plasma 1:1 (v:v) at 37 °C for 1 h. The concentration of nanoparticles during plasma incubation was thus higher than during possible in vivo scenario, for which they were calculated to be 0.133 mg mL −1 the in the blood pool. [ 66 ] For a sufficient separation, the AF4 was limited to a maximal plasma concentration of 5 vol%. Therefore, after incubation the samples had to be diluted with PBS to a particle concentration of 1.5 g L −1 and a 5 vol% solution of plasma and immediately measured in AF4.…”

Antibody‐Incorporated Nanomedicines for Cancer Therapy

“…Utilizing a similar strategy, Kramer et al used the iEDDA method for the synthesis of fast and bioorthogonally reacting nanoparticles to pretarget tumor cells ( Figure a). [ 179 ] Micelles were prepared from amphiphilic block copolymers based on N ‐(2‐hydroxypropyl)methacrylamide (HPMA) and then core‐crosslinked to yield micelle nanoparticles by UV light (Figure 6b). These micelle nanoparticles were subsequently modified with methylated Tz moieties, which were stable in blood plasma.…”

“…a,b) Reproduced with permission. [ 179 ] Copyright 2019, American Chemical Society. c) Schematic illustration and TEM image of the drug‐loaded MSNs‐Tz consisting of MSN (gray circle), chemotherapeutic agent (DOX; not shown), and tetrazine (Tz) at the terminal end of the long‐chain PEG.…”

“…b) Schematic illustration of the preparation of the Tz-modified polymeric nanoparticles by crosslinking the amphiphilic block copolymers and the subsequent click reaction with TCO-modified antibodies (pink: Tz group, green: IRDye CW800, yellow: TCO group, red: ligation product). a,b) Reproduced with permission [179]. Copyright 2019, American Chemical Society.…”

Antibody Pretargeting Based on Bioorthogonal Click Chemistry for Cancer Imaging and Targeted Radionuclide Therapy

“…As mention earlier, the TCO/Tz cycloaddition using mAbs-conjugates prevails in the scientific literature, but this strategy could also be applied to other systems such as organic molecules, peptides, mAbs fragments, nanoparticles, or polymeric micelles . On one hand, using smaller structures than mAbs as vectors for TCOs, such as peptides, chemistries, or mAbs fragments, could further increase the therapeutic index by concentrating higher doses of Tz-ligands in tumors.…”