# Controlled Photoiniferter RAFT-Based Development of Linear Polymers Induced by the Presence of a Peptide to Produce Synthetic Antibody Substitutes Applicable to Immunofluorescence Imaging Techniques

## TL;DR

Scientists created synthetic polymers that mimic antibodies by using a peptide template, showing strong binding and potential for imaging techniques.

## Contribution

A new method using PI-RAFT polymerization to create synthetic antibody substitutes with high affinity and imaging applicability.

## Key findings

- Polymers with twice the size of the target peptide showed maximum affinity (K_D: 9.09 ± 0.27 nM).
- The polymers demonstrated recognition capacity for the CB1 receptor in dual-labeling immunofluorescence assays.
- The method uses a 12 amino acid peptide template to guide polymer formation on glass beads.

## Abstract

The fabrication of synthetic receptors that mimic the
behavior
of antibodies is attracting widespread attention, given their affinity
and improved stability over those of their natural counterparts. In
accordance with the mutually induced-fit principle, where flexible
chains mutually induce the organization of each other, herein, we
describe the fabrication linear copolymers as complementary chains
to peptide epitopes. The production of these linear polymers is performed
via controlled solid-phase polymerization by reversible addition–fragmentation
chain transfer using a photoiniferter (PI-RAFT),
pouring the monomer mixture onto glass beads having a peptide immobilized
on their surface. This peptide influences the monomer arrangement
in linear polymers generated at the surface, functioning as a template.
PI-RAFT polymerization has enabled the production of polymers with
half, equal to, or twice the size of the target peptide, the latter
showing maximum affinity (K
D
: 9.09 ± 0.27 nM). The present study focuses on the
cannabinoid CB1 receptor as a target protein and its linear
C-terminal intracellular sequence as an epitope targeted by the polymers
described herein. Accordingly, a synthetic 12 amino acid peptide matching
that sequence was used as a template, achieving polymers with outstanding
recognition capacity toward the target protein, also being evidenced
here by their applicability to dual-labeling immunofluorescence assays
toward CB1 receptor-expressing cells.