# Bottlebrush Polymers for Articular Joint Lubrication: Influence of Anchoring Group Chemistry on Lubrication Properties

## TL;DR

This study explores how different chemical groups on bottlebrush polymers affect joint lubrication and cartilage binding, showing significant friction reduction.

## Contribution

The novel contribution is identifying epoxide-functionalized bottlebrush polymers as highly effective lubricants for cartilage surfaces.

## Key findings

- Bottlebrush polymers with anchoring groups reduce friction on cartilage-like surfaces by 75–95%.
- Epoxide groups show the best performance, reducing friction coefficient to 0.009 ± 0.001.
- Preliminary tests on animal cartilage confirm the potential of these polymers for osteoarthritis treatment.

## Abstract

The role of carboxylic, aldehyde, or epoxide groups incorporated
into bottlebrush macromolecules as anchoring blocks (or cartilage-binding
blocks) is investigated by measuring their lubricating properties
and cartilage-binding effectiveness. Mica modified with amine groups
is used to mimic the cartilage surface, while bottlebrush polymers
functionalized with carboxylic, aldehyde, or epoxide groups played
the role of the lubricant interacting with the cartilage surface.
We demonstrate that bottlebrushes with anchoring blocks effectively
reduce the friction coefficient on modified surfaces by 75–95%
compared to unmodified mica. The most efficient polymer appears to
be the one with epoxide groups, which can react spontaneously with
amines at room temperature. In this case, the value of the friction
coefficient is the lowest and equals 0.009 ± 0.001, representing
a 95% reduction compared to measurements on nonmodified mica. These
results show that the presence of the functional groups within the
anchoring blocks has a significant influence on interactions between
the bottlebrush polymer and cartilage surface. All synthesized bottlebrush
polymers are also used in the preliminary lubrication tests carried
out on animal cartilage surfaces. The developed materials are very
promising for future in vivo studies to be used in
osteoarthritis treatment.