In vivo label-free tissue histology through a microstructured imaging window.

Area of Science:

• Biomaterials Science
• Microscopy
• Immunology

Background:

• Traditional histopathology for biomaterial evaluation is time-consuming and costly, hindering longitudinal studies.
• Non-linear excitation microscopy offers a label-free, in vivo alternative with potential to overcome current limitations.

Purpose of the Study:

• To develop and validate an implantable microstructured device for label-free, non-linear excitation microscopy assessment of the immune response to biomaterials.
• To create a correlation between histological observations and label-free imaging for cell identification and quantification.

Main Methods:

• Fabrication of a 3D lattice microstructured device using two-photon laser polymerization.
• Implantation of the device in the chorioallantoic membrane (CAM) of embryonated chicken eggs for 7 days.
• Comparison of histological analysis (H&E staining) with non-linear excitation and confocal microscopy images to build a cell atlas.

Main Results:

• Quantification of recruited cells within the microstructures and identification of granulocytes using label-free imaging.
• Identification of collagen and microvessels via second-harmonic generation and autofluorescence imaging.
• Tissue reaction observed was consistent with CAM healing, not a foreign body response.

Conclusions:

• The developed microstructured device enables label-free in vivo imaging of the tissue-biomaterial interface using non-linear excitation microscopy.
• This approach provides a transformative alternative to conventional histopathology for longitudinal biomaterial validation and bioengineering.