Hello Thomas Kaltsounis

IAA is poorly soluble in water or aqueous buffers unless the pH of the solvent is alkaline. 1N NaOH is the preferable solvent to dissolve IAA. So, you may dissolve IAA completely in PBS (make stock solution 10 mg/mL) by adding NaOH (1N), followed by adjusting the pH to 7.4 by adding 0.5M Sodium Phosphate buffer pH 7.4 to neutralize the 1N NaOH and reduce the pH to 7.2 -7.4. Sterilize by filtering through a 0.2 μm filter.

You may prepare 0.5 M Sodium Phosphate buffer as follows:

Prepare 0.5 M NaH2PO4 and 0.5 M Na2HPO4. Mix 20% NaH2PO4 and 80% Na2HPO4 and adjust the pH to 7.4. Store in 1-ml aliquots at −20°C.

If you are interested in some more information, you may refer to the link below.

https://goldbio.com/documents/1372/Indole-3-Acetic%20Acid%20(IAA)%20Stock%20Solution%20Protocol.pdf

Good Luck!

1. IP Injection: To prepare an IP injection solution of IAA, you can use a vehicle solution that is suitable for injection and compatible with mice. One commonly used vehicle for IP injections is saline (0.9% sodium chloride solution). Here's a step-by-step guide:

a. Weigh the desired amount of IAA powder. b. Add a small volume of an appropriate solvent such as DMSO or ethanol to dissolve the IAA completely. Use the minimum amount of solvent necessary to dissolve the compound. c. Once the IAA is dissolved in the solvent, add the required amount of saline (0.9% sodium chloride solution) to achieve the desired concentration. d. Mix the solution thoroughly to ensure uniform distribution of IAA. e. Filter the solution using a sterile filter to remove any particulate matter. f. Use the prepared solution for IP injection following standard injection protocols.

2. Oral Gavage: Preparing an oral gavage solution for IAA involves using a suitable vehicle that is safe for oral administration to mice. Water or a suitable vehicle such as a pharmaceutical-grade solution (e.g., 0.5% carboxymethylcellulose sodium) can be used. Here's a general procedure:

a. Weigh the desired amount of IAA powder. b. Add a small volume of an appropriate solvent (DMSO or ethanol) to dissolve the IAA completely. Again, use the minimum amount of solvent necessary. c. Once the IAA is dissolved, add the required amount of vehicle solution (e.g., water or 0.5% carboxymethylcellulose sodium) to achieve the desired concentration. d. Mix the solution thoroughly to ensure uniform distribution of IAA. e. Filter the solution if needed to remove any particulate matter. f. Administer the solution using an oral gavage needle following proper oral gavage techniques.

When preparing the IAA solution for administration in drinking water, it is generally challenging because IAA is not highly soluble in water. However, a common approach is to prepare a concentrated stock solution in an appropriate solvent (e.g., DMSO) and then dilute it in the drinking water to achieve the desired concentration.