Improvement of fluorescence diagnosis of bladder cancer with ALA dendrimers
Bibliographic record
Abstract
Fluorescence guided cystoscopy with 5-aminolevulinic acid (5-ALA) or its hexyl derivative (h-ALA) is used in bladder cancer diagnosis. However, the lack of specificity and the fast photobleaching of the induced sensitizer protoporphyrin IX (PpIX) impair the complete resection of the tumor during cystoscopy. To overcome these drawbacks, we investigated the possibility to use dendrimers bearing a high ALA payload (18 molecules). We investigated the in vitro hydrolysis of ALA and the PpIX synthesis rate with ALA equimolar concentrations of h-ALA and 18-ALA. We further instilled prodrugs intravesically in rats bearing orthotopic bladder tumors and analyzed the PpIX distribution on frozen sections by fluorescence microscopy. A slow mono-exponential hydrolysis of the dendrimers was observed, compared with the rather fast release of ALA from h-ALA. Using dendrimers, the porphyrin levels observed to 24 h didn't significantly change, thus limiting PpIX synthesis to levels observed using h-ALA. The incomplete hydrolysis of ALA from dendrimer resulted in sustained PpIX synthesis in cells up to 24 h after exposure to the prodrug. Steric hindrance to esterase access would be a rate-determining factor in sequential release of ALA residues from the dendrimer. In vivo, the best tumor vs. muscle specificity of 18-ALA dendrimers was obtained after 1h instillation following 4h resting time with a tumor to healthy urothelium rate of 3/1 and a tumor to muscle ratio of 3.5/1. The continuous synthesis of PpIX has ensured a sustained ratio about 2.5/1 to 24 h after the end of instillation of prodrug. By comparison with h-ALA or smaller dendrimers with 6-ALA residues, 18-ALA dendrimers presented an increased tumor vs. urothelium ratio. Because of their size, 18-ALA dendrimers are less prone to enter a very cohesive structure. We have confirmed by the detection of esters ALA, and PpIX in serum from rats following intravesical administration that 18-ALA dendrimers were less taken up by the systemic circulation, contrary to h-ALA or 6-ALA. Dendrimers will more easily penetrate the tumor, explaining the high tumor to muscle ratio and the deeper penetration as compared to h-ALA. The prolonged and sustained PpIX synthesis and the improved selectivity are primary indicators that ALA dendrimers could possibly overcome drawbacks of ALA/h-ALA fluorescence guided cystoscopy.
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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".