Optical Properties of Gelatin Methacrylate and Implications for In Situ Cross-Linking in Spinal Cord Lesions and Engineered Hydrogel Systems
Bibliographic record
Abstract
Abstract Understanding how light interacts with biomaterials is critical not only for therapeutic delivery in vivo but also for enabling emerging light-based fabrication methods such as volumetric bioprinting. In particular, optical characterization of photosensitive hydrogels like Gelatin Methacrylate (GelMA) provides foundational data for additive manufacturing of complex, tissue-engineered constructs with spatially controlled architecture. GelMA is a promising candidate for use as an injectable hydrogel for spinal cord injury (SCI) repair. This is primarily due to its highly tunable properties, allowing it to mimic tissue. Additionally, GelMA can be optically crosslinked. Optical simulations of this material within the spinal cord can inform whether the cross-linking of this material is feasible and uniform within a particular injury with a chosen exposure paradigm. These simulations require the optical properties of the tissues and materials of interest. However, the optical properties of GelMA have not been studied. The optical properties of GelMA were measured using a double integrating sphere setup and modelled with inverse adding doubling. We measured the absorption coefficient (µ a [mm -1 ]), reduced scattering coefficient (µ s ’[mm -1 ]), and scattering anisotropy (g [unitless]) for GelMA hydrogels, and examined the effect on these properties when magnetically alignable microstructures were suspended in the hydrogel. We conducted Monte Carlo simulations using these optical properties to determine whether the GelMA hydrogels would be cross-linked under different illumination conditions within a representative spinal cord injury geometry. The depth of hydrogel cross-linking for this representative spinal cord injury geometry was experimentally validated. Overall, it was found that GelMA without rods has an µ a = 0.516 ± 0.025 mm -1 , with insignificant scattering at 450 nm, GelMA with rods has an µ a = 0.588 ± 0.018 mm -1 , µ s ’ = 0.196 ± 0.024 mm -1 , and g = 0.906 ± 0.014 at 450 nm. Additionally, it was observed that in fluid-filled lesions, external illumination is often sufficient to achieve uniform gel curing. In contrast, fibrotic lesions require an intraspinal approach to adequately deliver light throughout the lesion, although the dose distribution will be nonuniform. Finally, experimental results confirmed the simulation findings, showing that when exposing GelMA to 63.29 mW/cm 2 of 450 nm light, curing is uniform within the first 4 mm of gel and worsens with depth. These findings support the conclusion that larger volumes of photosensitive GelMA can be feasibly cured within the porcine spinal cord, but an intraspinal exposure will likely be required within human spinal tissue. These findings not only support the feasibility of in situ photopolymerization for SCI repair, but also provide critical optical parameters and validation approaches relevant to bioprinting systems.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".