Aqueous Protein–Polymer Bioconjugation via Photoinduced RAFT Polymerization Using High Loading Heterogeneous Catalyst

Abstract

Light-driven polymerization, such as photoinduced electron/energy transfer−reversible addition−fragmentation chain transfer (PET-RAFT) polymerization, enables biological benign conditions and versatile functional polymer structure design, which is readily used in protein−polymer bioconjugates. However, conventional metalloporphyrinic homogeneous catalysts for PET-RAFT polymerization suffer from limited aqueous solubility and tedious purification. Here we demonstrate the design of PET-RAFT photocatalyst from the reticular assembled Zr−porphyrinic metal−organic frameworks (MOFs), along with a biomacromolecule-based chain transfer agent, as efficient bioconjugation tools in water. Our methodology offers manufacturing advantages on bioconjugates under mild conditions such that MTT (3-[4,5dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and cytotoxicity assays have shown the preservation of the protein integrity, bioactivity, and high cell viability after PET-RAFT polymerization. We find that the fast kinetics are benefiting from the ultrahigh loading of metalloporphyrins in MOF-525-Zn. This heterogeneous catalyst also allows us to maintain living characteristics to incorporate myriads of monomers into block copolymers. Other advantages like easy postreaction purification, reusability, and high oxygen tolerance even in an open system are demonstrated. This study provides a tool of highly efficient heterogeneous photocatalysts for polymer−protein bioconjugation in aqueous media and paves the road for biological applications.

Development of High Throughput Photopolymerizations Using Micron‐Sized Ultrathin Metal‐Organic Framework Nanosheets

“…The deconvolution of high-resolution C 1s core-level spectra comprised three peaks with respective binding energies (BEs) at 284.6 eV for -C-C/-CH species, 285.9 eV for -C-N species and 288.1 eV for O-C═O species (Figure 2b,d and Figure S5b, Supporting Information). [17] Besides, the [-C-N]/[O-C═O] peak component area ratio approximated 2:1 after deconvolution were consistent with the molecular structure of ZnTCPP units except for a marked difference in specific element intensity for these MOF samples. The deconvolution of high-resolution C 1s core-level spectra comprised two peaks with BEs at 398.2 eV for the pyrrole nitrogen ((C)═N-) and 399.7 eV for amine nitrogen ((C)-N-) doped in the carbon matrix (Figure 2b′,d′ and Figure S5b′, Supporting Information).…”

“…The high degree of oxygen tolerance and catalyst reusability could be harnessed to enable PET‐RAFT polymerization to occur without prior deoxygenation suggesting the efficiency with which Zn‐ZnPPF‐2D can remove both dissolved oxygen and atmospheric oxygen diffusing into solution. [ 17,49,50 ] The unimodal molecular weight distribution confirmed that the Zn‐ZnPPF‐2D mediated PET‐RAFT polymerization in aerobic condition did not affect the polymerization kinetics and living characteristics, expect for a prolonged induction period resulting from continuous oxygen photosensitization and consumption (Figure S11, Supporting Information). Noting the broadband absorption characteristics of Zn‐ZnPPF‐2D nanosheets, PET‐RAFT polymerization was next extended to a range of hydrophilic acrylamides (including N,N ‐dimethylacrylamide (DMA), N,N ‐diethylacrylamide (DEA), N ‐isopropylacrylamide (NIPAM), and N ‐hydroxyethyl acrylamide (HEAA)) and hydrophobic acrylates (including methyl acrylate (MA), butyl acrylate (BA), isobornyl acrylate (IBA) and tetrahydrofurfuryl acrylate (THFA)) in a 96‐well deep well plate to determine any impediments to the polymerization.…”

“…In biological field, PET-RAFT polymerization have provided a powerful toolkit for expanding the structural and functional repertoire of protein, DNA and live cells. [15][16][17][18][19] The realization of cytocompatible PET-RAFT polymerization provides an array of advantages associated with the increase in structure diversity for secondary interaction, derivatization, and alternations in physical properties. [51] Successful polymerization without prior deoxygenation convinced us to perform the Zn-ZnPPF-2D mediated PET-RAFT polymerizations of various concentrations of poly(ethylene glycol) methyl ether acrylate (PEGA, M n = 480 g mol -1 ) in the presence of human embryonic kidney 293 cells (Hek293 cells) under red LED light excitation (𝜆 max = 635 nm, 3.6 mW cm -2 ).…”

“…[14] In the biological field, PET-RAFT polymerization has provided a powerful toolkit for expanding the structural and functional repertoire of protein, DNA and live cells. [15][16][17][18][19] However, the amount of feasible bio-substrates is limited and polymerizations in a high throughput format are still demanding for more efforts contributing to this area.…”

Controlled cationic polymerization using RAFT agents with selenonium cations as metal-free Lewis acids: from homogeneous to heterogeneous catalysis

“…Because they can easily be separated and reused, heterogeneous catalysts play an important role in various polymerizations, and increasing attention has been paid to this field in recent years. [30][31][32][33][34][35][36][37][38][39][40][41] However, the use of heterogeneous catalysis in LCP is very limited. Few studies of heterogeneous catalysis of LCP have been reported to date.…”