Biocompatibility and customizability: Expanding possibilities with 3D printed guide cannulas

Intracerebral cannulation bypasses the blood-brain barrier, and is frequently used for targeted drug delivery to specific brain structures. Despite the availability of brain infusion kits and manual injections without cannulation, the traditional design of guide cannulas continues to be utilized in research. Several protocols describing guide cannula manufacture from stainless steel needles have been published previously.

We describe a method for producing the first fully plastic guide cannula intended for intracerebroventricular injections in mice using Dental Sand A1-A2 resin and digital light processing 3D printing.

The lack of resin neurotoxicity for primary rat cortical neuron cultures was shown. Histological evaluations performed 6 weeks after guide cannula implantation to C57/black mice show that plastic cannula are biocompatible. Microglial and astroglial reactions to plastic cannulas are reduced compared to lab-made stainless steel cannulas. Plastic cannulas are less prone to obstruction, and remained unobstructed over the course of 3 weeks of daily injections, while 50 % of stainless steel cannula became impassable by the 2 week mark.

These are the first published cannulas intended for applications in mice which combine the presence of usable threads, allowing dummy cannula fixation, with a low profile and small footprint compared to commercially available cannulas.

Editable parametric and stl files for reproducing the cannulas presented in this manuscript are included. The method described in this paper is accessible to most laboratories, enabling near-perfect standardization in length combined with a high level of customizability.