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Abstract Background Limulus Amebocyte Lysate (LAL), which is a major component of Fungal infection diagnosis kit, is used for the adjunct diagnosis of invasive fungal infection. This study used different blood collection buffers to find the optimal blood collection buffer to maximize the yield of LAL. The PBS collection buffer was found to prevent degranulation during blood collection procedure and the PBS-derived Limulus Amebocyte Lysate (LAL) was observed to work in both the chromogenic test and the turbidimetric method assays. A similar phenomenon was observed with the caffeine collection buffer. Methods To further confirm this observation, we used a caffeine collection buffer to collect the blood of horseshoe crabs in the 2023 bleeding season (from July to October). Once a week, 3 crabs were bled for a total of 30 crabs. The blood of each crab was collected using the caffeine collection buffer and the 3% NaCl collection buffer, respectively. The cell pellets were resuspended into LAL reagent water (LRW) or 5 mM CaCl2. The final LAL activity was tested by both chromogenic and turbidimetric assay methods. Results The results showed that a caffeine collection buffer could prevent degranulation for over 1 hr and the activity yield of caffeine-derived LAL is much higher than that of the 3% NaCl solution. There was no discernible impact upon activity yield of crab size, period of the bleed season, or the vendors. Interestingly, caffeine-derived LAL was observed to work in both the chromogenic and turbidimetric assays. The enzyme characteristic of the LAL was also described. Conclusions Caffeine collection buffer prevents amebocyte degranulation during blood collection and processing. The activity of caffeine LAL is much higher than that of 3% NaCl. Caffeine LAL works in both chromogenic test and turbidimetric assay.
Zhang et al. (Tue,) studied this question.