Multimodal Approach to Assess Bone Regeneration and Scaffold Performance
February 13th, 2026
We propose a protocol for assessing bone regeneration at various hierarchical levels. This multimodal approach allows for structural analysis across different length scales, effectively addressing challenges in sample preparation. It also provides a reliable workflow for evaluating the effectiveness of biomaterials in promoting bone regeneration.
Our research evaluates how different biomaterials influen-cee-ate on bone architecture during the regeneration process. Bone regeneration requires a multiscale evaluation, as it is a hierarchically organized the tissue. This protocol enables analysis of the sample at the different scales.
To begin, secure the resin-embedded tibia containing the implanted biomaterial onto the specimen holder and attach it to the instrument arm. Orient the sample according to the desired sectioning direction. Obtain a low-speed diamond saw disc to section the bone into approximately 0.7-millimeter slices.
Fill the liquid reservoir until the fluid level completely covers the bottom edge of the blade. Ensure the sample is stable and horizontally aligned with the disc surface. Adjust the specimen position using the positioning knobs until the target cut region is aligned with the blade.
Begin cutting the sample using a higher speed setting and apply low pressure until an indentation forms. Then reduce the speed to complete the sectioning smoothly and minimize vibration. Stop the saw immediately after the cut is complete.
Then examine the cut sample using a stereo microscope for mounting. For mounting, use a homemade assembly consisting of an inner solid stainless steel cylinder and an outer hollow cylinder that provides mechanical support during polishing. Next, place the inner cylinder on a hot plate and heat it to approximately 120 to 140 degrees Celsius.
Choose a suitable wax and apply a small amount of wax onto the surface of the heated cylinder and allow it to melt completely. Then place the sample with the surface of interest facing down onto the wax-coated area and gently press the sample to ensure full contact with the melted wax. Then remove the aluminum cylinder from the hot plate and allow the wax to solidify at room temperature.
For coarse and intermediate polishing, select sandpaper with grit sizes of 1, 200, 2, 500, and 4, 100 to reduce the sample thickness to approximately 0.15 millimeters. Start with 1, 200-grit sandpaper, followed by 2, 500-grit while applying light pressure. Periodically monitor the sample thickness during polishing using reflection microscopy.
Once the target thickness is reached, polish both sides of the sample using 4, 100-grit sandpaper. Continuously clean the sample with distilled water during each polishing step. For final polishing, choose a diamond paste with six or three-micrometer particle size, based on the surface roughness of the sample.
Apply a small amount of diamond paste onto a felt polishing cloth, mounted on a polishing disc, and polish the sample. To detach the sample from the cylinder, warm the wax on a hot plate. After removing the unit from the hot plate, take the sample out from the cylinder.
Then gently polish both sides of the sample using minimal pressure and dry the polished surface with filter paper. Prior to microscopy analysis, mount the sample between a glass slide and coverslip using immersion oil as the mounting medium. Examine collagen fiber orientation using polarized light microscopy, starting with low magnification between 5x and 10x.
Finally, prepare the sample for scanning electron microscopy to further analyze the bone-biomaterial interface. After polishing and initial optical microscopy examination, intrinsic sample features allowed the region identified under light microscopy to be matched to the corresponding location in the micro-computed tomography dataset. Polarized light microscopy differentiated preexisting bone, shown in blue, from newly formed bone during healing, depicted in orange.
Higher magnification polarized light microscopy revealed an interface where bone grew in close opposition to preexisting cortical bone with Type I collagen fibers oriented perpendicularly in a thin region. Scanning electron microscopy imaging enabled precise localization of areas of interest. A volume of the selected region was further examined using slice-and-view tomography.
The face of the trench displayed bone morphology on a growing trabecula. Transmission electron microscopy enables nano scale examination of the bone-biomaterial interface, which can be combined with selected area electron diffraction. Selected area electron diffraction patterns indicated that both the biomaterial region and the bone region were composed of hydroxyapatite crystals.
Energy-dispersive X-ray spectroscopy mapping of the imaged interface region showed phosphorus and calcium. This multimodal workflow provides complementary insights that cannot be achieved by a single imaging technique. This workflow requires significant time, technical expertise, and access to specialized instrumentation.
It can investigate functional correlations, long-term bone remodeling, and biomaterial design.
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Overview
This article presents a detailed protocol for evaluating bone regeneration and the bone-biomaterial interface across multiple hierarchical levels. By integrating various imaging modalities, the method enables comprehensive analysis of bone repair processes, from the macroscopic to the nanoscopic scale, providing critical insights into scaffold effectiveness and osteointegration.
Key Study Components
Area of Science
- Biomaterials
- Bone tissue engineering
- Microscopy and imaging
Background
- Bone is a hierarchically organized tissue, with structure ranging from nanometer-scale collagen fibrils to macroscopic bone architecture.
- Successful bone implants require integration at multiple length scales for optimal function and mechanical performance.
- Comprehensive evaluation of bone repair and scaffold integration is technically challenging due to the complexity of bone structure.
- Multimodal imaging approaches are necessary to fully assess the effects of biomaterials on bone regeneration.
Purpose of Study
- To develop and demonstrate a protocol for multiscale analysis of bone regeneration and the bone-biomaterial interface.
- To enable assessment of newly formed bone and scaffold integration at different hierarchical levels.
- To provide a robust workflow for evaluating the effectiveness of bone repair scaffolds.
Methods Used
- Sectioning of resin-embedded bone samples containing biomaterials using a low-speed diamond saw.
- Mounting and polishing of bone sections to achieve thin samples suitable for microscopy.
- Polarized light microscopy to assess collagen fiber orientation and distinguish preexisting from newly formed bone.
- Scanning electron microscopy (SEM) and slice-and-view tomography for high-resolution imaging of the bone-biomaterial interface.
- Transmission electron microscopy (TEM) and selected area electron diffraction to analyze nanoscale features and crystal composition.
- Energy-dispersive X-ray spectroscopy (EDS) mapping to determine elemental composition at the interface.
Main Results
- The protocol enables precise preparation and analysis of bone-implant samples at multiple scales.
- Polarized light microscopy differentiates preexisting bone from newly formed bone based on collagen orientation and color.
- SEM and tomography reveal detailed bone morphology and scaffold integration at the microscale.
- TEM and electron diffraction confirm the presence of hydroxyapatite crystals in both bone and biomaterial regions.
- EDS mapping identifies key elements such as phosphorus and calcium at the interface.
Conclusions
- This multimodal workflow provides complementary insights into bone regeneration that cannot be achieved with a single imaging technique.
- The protocol supports functional correlation studies, long-term bone remodeling analysis, and biomaterial design optimization.
- Significant technical expertise and specialized instrumentation are required to implement the workflow.
