# Molecular Biointerface Characterization for an Implanted Medical Device Using Cryogenic Orbitrap Secondary Ion Mass Spectrometry (Cryo-OrbiSIMS)

## TL;DR

This study uses advanced imaging techniques to analyze the molecular layers formed around implanted medical devices in mice, revealing insights into the body's response to implants.

## Contribution

The work introduces a novel depth profiling approach using Cryo-OrbiSIMS to study the biointerface of implants at a molecular level.

## Key findings

- Elevated sugars and itaconate were observed at 1 day of implantation, indicating early immune response.
- Inflammation markers like urate and palmitic acid were detected at 28 days.
- Depth profiling revealed distinct molecular layers, with lipids at the implant interface and amino acids/nucleic acids near host tissue.

## Abstract

Implanted
medical devices often fail due to foreign body reactions
(FBRs), a process that is still not fully understood. This work presents
a depth profiling approach to provide insight into the spatial metabolomics
of the biointerface of implants, revealing biomolecular strata representative
of the host response. This study examines silicone rubber poly­(dimethylsiloxane)
catheters implanted in mice for 1 and 28 days. Cryo-OrbiSIMS was used
in combination with ToF-SIMS to identify metabolite profiles from
the biological deposit found on the implants after removal from the
tissue, which were previously unattainable using tissue sectioning.
Machine learning and statistical analysis of the profiles were used
to help identify early biointerface responses to the implant, including
the observation of elevated sugars and itaconate, an immunomodulatory
metabolite that modulates FBR, at 1 day of implantation. At day 28,
inflammation-associated markers were observed, such as urate and palmitic
acid (FA 16:0). Depth profiling revealed two distinct molecular layers
in the deposits: amino acids and nucleic acids were preferentially
seen toward the host tissue, consistent with the observation of a
cell monolayer in the tissue sections, whereas certain lipids and
fatty acids were either at the catheter–deposit interface or
toward the host tissue after 28 days. The stratification was less
well developed at 1 day of implantation, but common lipids were seen
at the deposit–implant interface across both time points. These
insights advance the understanding of FBR and support the development
of improved implant materials.