Polarization second harmonic generation by image correlation spectroscopy on collagen type I hydrogels.

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Biophysics

Background:

• Accurate mechanical property quantification of scaffolds is crucial for biomimetic tissue engineering.
• Microscopic techniques like label-free second harmonic generation (SHG) imaging complement bulk rheological measurements.
• Image correlation spectroscopy (ICS) has been used with SHG images, but the polarization SHG (P-SHG) effect was previously unaddressed.

Purpose of the Study:

• To develop a novel and flexible model for applying ICS to P-SHG images of fibrous structures.
• To incorporate the P-SHG effect into ICS analysis for improved quantification.
• To overcome limitations of existing models in analyzing fibrous scaffold properties.

Main Methods:

• Developed a new model based on straightforward assumptions, including the P-SHG effect.
• Evaluated the model using simulated datasets and compared it with existing literature models.
• Applied the model to experimental data from collagen type I hydrogels.

Main Results:

• The new model reliably applies ICS to P-SHG images of fibrous structures, accounting for ACF particularities.
• The model shows no restrictions on fiber length for density retrieval.
• It can determine average fiber length and P-SHG related non-zero susceptibility tensor element ratios for certain length ranges.
• Experimental validation on collagen type I hydrogels yielded SHG tensor element ratios and fiber thickness values consistent with literature.

Conclusions:

• The proposed model offers a reliable method for quantitative analysis of P-SHG images in fibrous scaffolds.
• It enhances the accuracy of mechanical property assessment for biomimetic tissue engineering.
• The model's validity and applicability are confirmed by experimental results matching established literature values.