Design of functional cationic microgels as conjugation scaffolds

Abstract

We describe the development of primary amine functionalized microgels with the potential as dye scaffolds for bioimaging.

Importance of pH in Synthesis of pH-Responsive Cationic Nano- and Microgels

“…Cationic polymers can be conjugated with biomolecules such as peptides, antibodies, and nucleic acids for different purposes [ 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. Especially the replacement of controversial viral vectors with cationic polymers for delivery of nucleic acid contructs experiences emerging interest in the context of genetic therapies or vaccination [ 39 ].…”

“…However, to reversibly immobilize nucleic acids or peptides with nano- or microgels, a sufficient amount of cationic groups (e.g., stemming from amines) has to be incorporated into their network [ 40 ]. To achieve this, various approaches including the post-synthetic introduction of cationic charges (e.g., hydrolysis of polyvinylformamide to polyvinylamine or “click” chemistry), addition of salts to screen charges, synthesis in reverse micelles or the use of anionic radical initiators have been published [ 12 , 36 , 41 , 42 , 43 , 44 , 45 ]. However, these solutions can have certain drawbacks, as they render the synthesis more complex, could induce aggregation and aspherical deformations or introduce (possibly unwanted) anionic charges into the microgels.…”

“…Using the well-established method of precipitation polymerization, different issues arise at elevated concentrations of the cationic monomers. For various polymer systems, a decreasing microgel size along with high dispersities, poor synthesis yields and low incorporation efficiencies of the cationic comonomer are reported consistently for increased concentrations of the comonomer [ 12 , 36 , 46 , 47 , 48 ]. A work by Meunier et al on cationic microgels based on N -isopropylacrylamide (NIPAM) and the amine 2-aminoethylmethacrylate hydrochloride (AEMH) reveals a clear influence of the cationic comonomer on size, yield and polydispersity of the obtained cationic microgels even at minor AEMH-feeds below 5 mol% [ 47 ].…”

Simple Platform Method for the Synthesis of Densely Functionalized Microgels by Modification of Active Ester Latex Particles

“…For the preparation of stimuli‐responsive microgels, e.g., pH‐ or light‐responsive microgels, approaches focus on traditional copolymerization in precipitation polymerization, in which only a small portion of functional groups can participate, and lead to limited functionality . Our approach also contrasts other microgel synthesis approaches, in which small amounts of active ester moieties were incorporated in classical precipitation polymerization by herein focusing on using the active ester monomer alone (together with crosslinker) in an emulsion polymerization approach and showing routes toward densely functionalized microgels.…”

“…[ 26,27,31 ] For the preparation of stimuli-responsive microgels, e.g., pH-or light-responsive microgels, approaches focus on traditional copolymerization in precipitation polymerization, in which only a small portion of functional groups can participate, and lead to limited functionality. [32][33][34] Our approach also contrasts other microgel synthesis approaches, [ 35,36 ] in which small amounts of active ester moieties were incorporated in classical precipitation polymerization by herein focusing on using the active ester monomer alone (together with crosslinker) in an emulsion polymerization approach and showing routes toward densely functionalized microgels. In more detail, we will demonstrate the synthesis of series of precisely controlled microgels from latex particles bearing pentafl uorophenyl active ester (PFPA) groups at each monomer unit by the nucleophilic substitution of active esters with functional amines.…”