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Table 2 In vitro tests design: main factors affecting bioaccessibility results

From: Experimental determination of the oral bioavailability and bioaccessibility of lead particles

Parameters Degree of Importance General impact on IVBA% Notes References (non exhaustive)
Gastric pH +++ - IVBA ↑ when pH ↓ - Check the pH increase at the end of the G phase. [69, 8184]
Intestinal pH +++ - ↓ IVBA as compared to gastric IVBA - Adjust intestinal IVBA to Pb salt solubility during the intestinal phase [65, 67, 85, 86]
   - Major ↓ IVBA from pH 4 to 6   
    - Increase in solubility of bile/pancreatin-Pb complexes at pH 7.5  
   - Slight ↑ IVBA at pH 7.5 compared to pH 6.0-7.0   
Temperature - - No impact between 20°C and 37°C - May be important when enzymes are added [84]
Phases simulated +++ - Gastric IVBA > Intestinal IVBA - Adjust intestinal IVBA to Pb salt solubility during the intestinal phase [67]
Extraction + - IVBA ↓ in the range: centrifugation > microfiltration > UF - No difference between 0.2 and 0.45 μm filtration [84, 87]
Fluid composition + - Contradictory results (↑ or ↓ IVBA) - Physiologically based fluids may be important when food is added [55, 67, 85, 8890]
   - Physiologically based fluids do not seem important for the G phase   
    - Bile/pancreatin would create soluble complexes with Pb  
Retention time ++ - IVBA ↑ when gastric phase time ↑ - Lower impact on more soluble Pb forms: IVBA plateau reached after 20–30 min [55, 74, 88, 91]
   - No information on intestinal extraction time effect   
Mixing ++ - Aggressive mixing (Ar gas) ↑ IVBA - End-over-end agitation adapted to maximize solid/fluid contact, but not too aggressive [69, 74, 84]
S/L ratio (g/mL) +++ - IVBA ↓ with high S/L > 1/100 - High S/L ↑ the effect of TM on pH ↑ [83, 84, 92]
   - No effect between low ratio 1/100 and 1/5000 - Low ratios (< 1/125) give poorer reproducibility  
Food addition +++ - IVBA ↓ with food, except powdered milk - Effect variable depending on food type [62, 87, 88, 93]
    - Fed tests linked to lower recovery rates  
  1. +++ high importance, ++ moderate importance, + light importance, - no importance, based on the studies published to date.